sirolimus and Prostatic-Neoplasms

Breast cancer (BC) and prostate cancer (PC) are at the top of the list when it comes to the most common types of cancers worldwide. The phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway is important, in that it strongly influences the development and progression of these tumors. Previous studies have emphasized the key role of inhibitors of the PIK3/AKT/mTOR signaling pathway in the treatment of BC and PC, and it remains to be a crucial method of treatment. In this review, the inhibitors of these signaling pathways are compared, as well as their effectiveness in therapy and potential as therapeutic agents. The use of these inhibitors as polytherapy is evaluated, especially with the use of hormonal therapy, which has shown promising results.

Topics: Breast Neoplasms; Hormones; Humans; MTOR Inhibitors; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; Sirolimus; TOR Serine-Threonine Kinases

The scientific rationale and existing evidence for the use of novel molecular targets in the chemoprevention of cancer are reviewed, with special attention to prostate cancer.. A search for relevant literature on basic science and clinical trials was conducted using PubMed/MEDLINE.. The emergence of molecularly targeted therapies for advanced malignancies creates an important opportunity to examine these agents for the chemoprevention of prostate cancer. Two critical targets in the proliferation and malignant transformation of normal cells, the PI3/Akt signal transduction pathway and the epidermal growth factor receptor, are currently the focus of several novel investigational therapies that are in late stage phase II and phase III studies.. Research to date supports consideration of these novel molecular targets as future agents in the chemoprevention of prostate cancer.

Topics: Anticarcinogenic Agents; ErbB Receptors; Humans; Male; Phosphatidylinositol 3-Kinases; Prostatic Neoplasms; Protein Kinases; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

Background Androgen deprivation therapy (ADT) is a standard treatment for high-risk biochemically-recurrent, non-metastatic prostate cancer (BRPC) but is not curative and associated with toxicity. Racemetyrosine (SM-88) is an amino-acid analogue used with methoxsalen, phenytoin, and sirolimus (MPS) to enhance SM-88 activity. Method A phase 1b/2, open-label trial in BRPC and rising PSA. Patients were given daily SM-88 (230 mg BID), methoxsalen (10 mg), phenytoin (50 mg), and sirolimus (0.5 mg)). Outcome measures included changes in PSA, circulating tumor cells (CTCs) and imaging. Results 34 subjects were screened, 23 treated and 21 remained on study for ≥12 weeks. The median PSA was 6.4 ng/ml (range 1.7-80.1); doubling-time 6.2 months (range 1.4-36.6) and baseline testosterone 319.1 ng/ml (range 2.5-913.7). Median duration of therapy was 6.5 months (2.6-14.0). CTCs (median 48.5 cells/4 ml (range 15-268) at baseline) decreased a median of 65.3% in 18 of 19 patients. For patients who achieved an absolute CTC nadir count of <10 cells/4 ml (n = 10), disease control was 100% i.e. no metastases or PSA progression, while on trial (p = 0.005). PSA fell by ≥50% in 4.3% (1 subject). No patients developed metastatic disease while on treatment (metastases free survival =100%). There were no treatment-related adverse events (AEs) and quality of life was unchanged from baseline on the EORTC QLQ-C30 and QLQ-PR25. Testosterone levels rose slightly on SM-88 and were unrelated to efficacy or toxicity. Conclusions Use of SM-88 was associated with disease control while maintaining QOL. SM-88 may delay the need for ADT and the associated hormonal side effects. Larger trials are planned.Trial registration number, date of registration - NCT02796898, June 13, 2016.

Topics: Aged; Aged, 80 and over; Androgen Antagonists; Humans; Kaplan-Meier Estimate; Male; Methoxsalen; Middle Aged; Neoplasm Recurrence, Local; Phenytoin; Prostate-Specific Antigen; Prostatic Neoplasms; Quality of Life; Sirolimus; Tyrosine

Recent data indicate that there is a significant cross-talk between the PI3K/Akt/mTOR and androgen receptor signaling pathways. We evaluated safety and tolerability as well as potential drug-drug interaction of ridaforolimus, a mammalian target of rapamycin (mTOR) inhibitor, when combined with the androgen receptor inhibitor bicalutamide in patients with asymptomatic, metastatic castration-resistant prostate cancer.. Patients were treated with the combination of ridaforolimus 30 mg/day for 5 consecutive days each week and bicalutamide 50 mg/day. Ridaforolimus pharmacokinetics was assessed with and without bicalutamide.. Twelve patients were enrolled including 1 screen failure. Dose reductions were required in 7 patients. Three of the 11 patients experienced a dose-limited toxicity, 1 with Grade 3 hyperglycemia and 2 with Grade 2 stomatitis leading to <75 % of planned ridaforolimus dose during the first 35 days of study treatment. The pharmacokinetic results showed no differences in exposures to ridaforolimus with and without concomitant bicalutamide administration.. Although there was no evidence of a clinically relevant pharmacological drug-drug interaction, the occurrence of dose-limiting toxicities in 3 of 11 evaluable patients at a reduced dose of ridaforolimus of 30 mg/day suggests that this combination may not be well suited for asymptomatic or minimally symptomatic prostate cancer patients.

Topics: Aged; Androgen Antagonists; Anilides; Antineoplastic Combined Chemotherapy Protocols; Dose-Response Relationship, Drug; Drug Interactions; Follow-Up Studies; Humans; Male; Maximum Tolerated Dose; Middle Aged; Neoplasm Metastasis; Nitriles; Orchiectomy; Prospective Studies; Prostatic Neoplasms; Sirolimus; TOR Serine-Threonine Kinases; Tosyl Compounds

To determine the rate at which computed tomographically guided pelvic percutaneous bone biopsy in men with metastatic castration-resistant prostate cancer (mCRPC) yields adequate tissue for genomic profiling and to identify issues likely to affect diagnostic yields.. This study was institutional review board approved, and written informed consent was obtained. In a phase II trial assessing response to everolimus, 31 men with mCRPC underwent 54 biopsy procedures (eight men before and 23 men both before and during treatment). Variables assessed were lesion location (iliac wing adjacent to sacroiliac joint, iliac wing anterior and/or superior to sacroiliac joint, sacrum, and remainder of pelvis), mean lesion attenuation, subjective lesion attenuation (purely sclerotic vs mixed), central versus peripheral lesion sampling, lesion size, core number, and use of zoledronic acid for more than 1 year.. Of 54 biopsy procedures, 21 (39%) yielded adequate tissue for RNA isolation and genomic profiling. Three of four sacral biopsies were adequate. Biopsies of the ilium adjacent to the sacroiliac joints were more likely adequate than those from elsewhere in the ilium (48% vs 28%, respectively). All five biopsies performed in other pelvic locations yielded inadequate tissue for RNA isolation. Mean attenuation of lesions with inadequate tissue was 172 HU greater than those with adequate tissue (621.1 HU ± 166 vs 449 HU ± 221, respectively; P = .002). Use of zoledronic acid, peripheral sampling, core number, and lesion size affected yields, but the differences were not statistically significant. Histologic examination with hematoxylin-eosin staining showed that results of 36 (67%) biopsies were positive for cancer; only mean attenuation differences were significant (707 HU ± 144 vs 473 HU ± 191, negative vs positive, respectively; P < .001).. In men with mCRPC, percutaneous sampling of osseous metastases for genomic profiling is possible, but use of zoledronic acid for more than 1 year may reduce the yield of adequate tissue for RNA isolation. Sampling large low-attenuating lesions at their periphery maximizes yield.

Topics: Biopsy; Bone Density Conservation Agents; Bone Marrow; Diphosphonates; Everolimus; Gene Expression Profiling; Humans; Imidazoles; Immunosuppressive Agents; Male; Prostatic Neoplasms; RNA; Sirolimus; Tomography, X-Ray Computed; Ultrasonography, Interventional; Zoledronic Acid

The mammalian target of rapamycin (mTOR) pathway is deregulated in castration-resistant prostate cancer (CRPC). We investigated the efficacy and toxicity of temsirolimus, an mTOR inhibitor, in chemotherapy-naïve CRPC.. In this phase II open label study, eligible patients received IV temsirolimus at 25 mg weekly until objective disease progression, unacceptable toxicity or investigator's discretion. Toxicity was assessed every 4 weeks and responses every 8 weeks. Primary end point was calculating the overall response (OR) rate as well as measuring stable disease (SD) to assess the overall clinical benefit calculated as OR+SD. Secondary end points included prostatic-specific antigen (PSA) changes and time to progression biochemically and radiographically. Correlative studies included prospective assessment of quality of life (QoL) using two previously validated scales.. Although the sponsor halted the study early, 21 patients were enrolled of which, 15 were evaluable for efficacy and OR. Median age was 74 (range: 57-89), median PSA was 237.5 ng ml(-1) (range: 8.2-2360), visceral disease present in 11 patients (52%), and 17 patients (81%) patients had Gleason score (7-10). Two patients had a partial response (PR) and eight had SD. The OR was 13% (2/15) and the overall clinical benefit (OR+SD) was 67% (10/15). Median time to radiographic disease progression was 2 months (range 2-10 months). Biochemical response assessment was available for 14/15 patients. Any PSA decline was observed in four patients (28.5%; 4/14) with one patient (7%) having >50% PSA decline. Median time to progression by PSA was 2 months (range 1-10 months). With a median follow-up of 32 months, median overall survival (OS) was 13 months (range: 2-37) and three patients remain alive at the data cutoff (5/2013) for an OS of 14% at 4 years on an intent-to-treat analysis. Major non-haematologic toxicities included fatigue (19%) and pneumonia (14%). Main laboratory toxicities included hyperglycaemia (24%) and hypophosphatemia (14%). Also, 52% of enrolled patients had serious adverse events. Other toxicities were consistent with previously reported adverse events with temsirolimus. Despite these observed adverse events, temsirolimus did not adversely impact QoL.. Temsirolimus monotherapy has minimal activity in chemotherapy-naïve CRPC.

Topics: Aged; Aged, 80 and over; Antineoplastic Agents; Disease Progression; Humans; Male; Middle Aged; Orchiectomy; Prospective Studies; Prostate-Specific Antigen; Prostatic Neoplasms; Protein Kinase Inhibitors; Quality of Life; Sirolimus; TOR Serine-Threonine Kinases; Treatment Outcome

Few options are available after taxane-based therapy in men with CRPC. Genetic alterations involving the mTOR pathway have been associated with CRPC development, raising the hypothesis that blocking mTOR signaling may be an effective targeted approach to treatment.. In this open-label phase II study, the mTOR inhibitor Ridaforolimus was administered at a dose of 50 mg intravenous once weekly to 38 patients with taxane-treated CRPC. The primary end point was best overall response according to modified Response Evaluation Criteria in Solid Tumors guidelines. Serum prostate-specific antigen levels were prospectively monitored as a biomarker for cancer activity.. No objective responses were observed, but 18 patients (47.4%) had stable disease as their best response. Based on progression-free survival analysis, median time to progression with Ridaforolimus was 28 days (95% confidence interval, 27-29). Eight patients (21.1%) had stable disease as their best overall prostate-specific antigen response. The median number of days from first to last dose was 109.5 days (range, 1-442 days). Ridaforolimus was generally well tolerated, with a safety profile similar to that observed in patients with advanced malignancies. The most common side effects were typically mild or moderate in severity.. Ridaforolimus was generally well tolerated. Treatment did not produce objective responses, but stable disease was observed in some patients with taxane-treated CRPC. Alternative treatment regimens, such as combination therapy with a taxane or in a maintenance treatment paradigm, should be considered for further evaluation in this patient population.

Topics: Adenocarcinoma; Adult; Aged; Aged, 80 and over; Antineoplastic Agents; Disease-Free Survival; Drug Administration Schedule; Gonadotropin-Releasing Hormone; Humans; Male; Middle Aged; Orchiectomy; Prostate-Specific Antigen; Prostatic Neoplasms; Sirolimus; Taxoids; TOR Serine-Threonine Kinases; Treatment Outcome

Study Type--Therapy (cohort) Level of Evidence 2a. What's known on the subject? and What does the study add? Despite expanding treatment options for castration-resistant prostate cancer (CRPC), therapies with long response duration remain intangible due to prostate cancer cells' natural ability to develop iterative resistance. Androgen receptor (AR) signaling has been shown to play a critical role in CRPC and its expression is regulated by the PI3K-Akt pathway. Thus inhibition of AR signalling and PI3K-Akt-mTOR (a downstream mediator of the PI3K-Akt pathway) pathway is a logical combination in CRPC and we report a phase II trial of RAD001 and bicalutamide. Our study is the first clinical trial report of an AR inhibitor of PI3K-Akt-mTOR. The AR pathway and the PI3K-Akt-mTOR pathway are two of the most relevant growth pathway for CRPC. Despite low efficacy results from our trial there will be significant interest in the field for these data (dose, schedule, response, toxicity, trial design) as newer generations of both AR inhibitors and PI3K-Akt-mTOR inhibitors are in development and likely will be tested in combination in CRPC.. • To determine best overall response and duration of response of RAD001, a selective inhibitor of mammalian target of rapamycin, in combination with bicalutamide in castration-resistant prostate cancer (CRPC). • To characterize the toxicity profile of RAD001 in combination with bicalutamide in patients with CRPC.. • A phase II study was conducted to explore the efficacy and tolerability of RAD001 (10 mg daily) in combination with bicalutamide (50 mg daily) in men with progressive CRPC. • The primary endpoint was a composite of prostate-specific antigen (PSA) level and measurable disease response by standard criteria. • This single-stage trial with a sample size of 38 eligible patients provided 90% power to differentiate a response rate of ≥ 40% from a response rate of ≤ 20%, as expected for bicalutamide alone (α= 0.10, power = 0.90).. • In total, 36 men were enrolled, with a median (range) age of 68 (60-72) years and median (range) baseline PSA level of 22.2 (8.4-121.3) ng/mL, and 89% had metastatic disease. • There were 31 (86%) patients had previously used bicalutamide for a median duration of 7.4 months. • There were two patients with a confirmed PSA level decline ≥ 50%. • The median (interquartile range) time to progression was 8.7 (7.9-15.9) weeks. • The most common toxicity was grade 1/2 mucositis, which was observed in 20 (56%) patients.. • The combination of RAD001 and bicalutamide in men with CRPC was well tolerated but had low activity and failed to achieve the primary endpoint of improved response compared to the results previously achieved for bicalutamide alone in this population.

Topics: Adenocarcinoma; Aged; Androgen Receptor Antagonists; Anilides; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Drug Resistance, Neoplasm; Everolimus; Humans; Male; Middle Aged; Nitriles; Prostate-Specific Antigen; Prostatic Neoplasms; Sirolimus; Tosyl Compounds; Treatment Outcome

Given discrepancies between preclinical and clinical observations of mammalian target of rapamycin (mTOR) inhibition in prostate cancer, we sought to determine the pharmacodynamic effects of the mTOR/TORC1 inhibitor rapamycin in men with intermediate- to high-risk prostate cancer undergoing radical prostatectomy.. Rapamycin was given at 3 or 6 mg orally for 14 days before radical prostatectomy in men with multifocal Gleason sum > or =7 prostate cancer; 10 untreated control subjects were included. The primary outcome was inhibition of phosphorylation of ribosomal S6 in posttreatment radical prostatectomy versus pretreatment biopsy tumor tissue, evaluated using a Simon two-stage design for pharmacodynamic efficacy.. Thirty-two subjects were accrued: 20 at 3 mg, 2 at 6 mg, and 10 controls. No dose-limiting toxicities were observed at 3 mg; however, two of two men enrolled at 6 mg experienced dose-limiting toxicities including thrombocytopenia and fever with grade 3 stomatitis. Adverse events observed at 3 mg included stomatitis, rash, ileus, and neutropenia. Pharmacodynamic studies showed tumor S6 phosphorylation inhibition in 50% of 10 evaluable rapamycin-treated men with sufficient paired tissue [median 58% inhibition (P = 0.049) versus 2% inhibition in controls (P = 0.75)] with no significant effect on AKT activity. We observed no change in Ki-67 or caspase-3 cleavage but noted a reduction in cytoplasmic p27 staining with increased nuclear localization with rapamycin treatment. Prostate tissue rapamycin concentrations were 3- to 4-fold higher than blood.. At 3 mg daily, rapamycin successfully and safely inhibited prostate cancer S6 phosphorylation and achieved relatively high prostate tissue concentrations. No effect on AKT phosphorylation, tumor proliferation, or apoptosis was observed.

Topics: Administration, Oral; Aged; Aged, 80 and over; Antibiotics, Antineoplastic; Drug Administration Schedule; Humans; Intracellular Signaling Peptides and Proteins; Male; Middle Aged; Neoadjuvant Therapy; Phosphorylation; Prostatectomy; Prostatic Neoplasms; Protein Serine-Threonine Kinases; Ribosomal Protein S6 Kinases; Sirolimus; TOR Serine-Threonine Kinases

There is no doubt that prostate cancer is a disease. Then, according to hyperfunction theory, menopause is also a disease. Like all age-related diseases, it is a natural process, but is also purely harmful, aimless and unintended by nature. But exactly because these diseases (menopause, prostate enlargement, obesity, atherosclerosis, hypertension, diabetes, presbyopia and thousands of others) are partially quasi-programmed, they can be delayed by slowing aging. Is aging a disease? Aging is a quasi-programmed disease that is partially treatable by rapamycin. On the other hand, aging is an abstraction, a sum of all quasi-programmed diseases and processes. In analogy, the zoo consists of animals and does not exist without animals, but the zoo is not an animal.

Topics: Aging; Animals; Humans; Longevity; Male; Menopause; Prostatic Neoplasms; Sirolimus

Statin has recently been studied for its effects on inducing cell death and inhibiting metastasis. Nevertheless, the precise mechanism of its anti-tumor effect is not yet fully understood. We conducted research on statin as a novel treatment for castration-resistant prostate cancer (CRPC). This study focused on autophagy in prostate cancer cells and assessed the effects of simvastatin.. After administering simvastatin to PC-3 cells, we conducted a microarray analysis. Simvastatin was administered to prostate cancer cell lines (PC-3, LNCaP-LA; cultured under androgen-depleted conditions, DU145, 22RV1), and the tumor proliferation inhibition was evaluated using the MTS assay and cell count. Autophagy was measured by observing autophagosome staining under a fluorescence microscope and quantifying LC-3 protein using western blot. We also investigated the effects of rapamycin, an autophagy inducer, and chloroquine as an inhibitor.. Simvastatin demonstrated a significant concentration-dependent growth inhibition effect on prostate cell lines. Moreover, a significant increase in autophagy was observed in all cell lines following simvastatin administration. When we administered simvastatin with rapamycin at a concentration that did not show a tumor growth inhibitory effect, it significantly enhanced autophagy induction compared to simvastatin alone, and also significantly enhanced the growth inhibition effect on PC-3 cells.. Simvastatin induced autophagy and inhibited the proliferation of prostate cancer cell lines. The combination of simvastatin and rapamycin significantly induced autophagy and enhanced the inhibitory effect of simvastatin on proliferation. This mechanism may serve as a novel therapeutic target.

Topics: Apoptosis; Autophagy; Cell Line, Tumor; Cell Proliferation; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Male; Prostate; Prostatic Neoplasms; Simvastatin; Sirolimus

We investigated patients with genitourinary cancer after kidney transplant and the effects of immunosuppression reduction and switching to mechanistic target of rapamycin inhibitors.. We retrospectively evaluated kidney transplant recipients seen at our center between January 2000 and January 2020. Patients with <1 year of follow-up were excluded.. Of 827 patients, genitourinary cancer was detected in 11 (1.3%): prostate cancer in 5 patients (45%), renal cell carcinoma in native kidney in 3 (27%), renal cell carcinoma in allograft kidney in 2 (18%), and transitional cell carcinoma of the bladder in 1 (9%). All patients had surgery. Two patients had bone metastasis due to prostate cancer at diagnosis. Two patients had allograft nephrectomy due to de novo renal cell carcinoma. Mean follow-up and age were 97 ± 45 months (range, 26-189) and 50 ± 10.2 years (19% female). After cancer diagnosis, excluding the 2 patients with allograft nephrectomy, immunosuppression was changed in 8 patients (88.8%) (1 patient received the same treatment before and after cancer diagnosis). Six patients received double-drug and 3 received triple-drug protocols. Of 9 patients, 2 were already using mechanistic target of rapamycin inhibitors before cancer diagnosis and 7 were switched: 4 to double-based and 3 to triple-based regimens. Six were switched from tacrolimus. With new treatments, patients showed no progressive kidney failure or rejection (38 ± 40 mo average follow-up). At last follow-up, mean glomerular filtration rate was 62.8 ± 34 mL/min/1.72 m2, which was similar to rate at cancer diagnosis (58.9 ± 24 mL/ min/1.72 m2; P = .78). During follow-up, no patients developed local recurrence of primary tumor or new metastasis, and none showed adverse effects after switch to mechanistic target of rapamycin inhibitors. Three patients died of malignancy-unrelated reasons (ileus, urinary sepsis, heart failure).. Mechanistic target of rapamycin inhibitor-based drugs can be an important maintenance immunosuppressive treatment option for kidney transplant recipients with genitourinary cancers.

Topics: Carcinoma, Renal Cell; Graft Rejection; Humans; Immunosuppressive Agents; Kidney Neoplasms; Kidney Transplantation; Male; Prostatic Neoplasms; Retrospective Studies; Sirolimus; Treatment Outcome; Urogenital Neoplasms

MicroRNAs (miRNAs) are the small non-coding regulatory RNA molecules involved in gene regulation via base-pairing with complementary sequences in mRNAs. The dysregulation of specific miRNAs, such as miR-99b-5p (miR-99b), is associated with prostate cancer (PCa) progression. However, the mechanistic role of miR-99b in PCa remains to be determined. In this study, we aimed to investigate the functional and clinical significance of miR-99b in PCa.. The expression of miR-99b and its downstream targets mTOR/AR in the PCa samples were analyzed by RT/qPCR. The effects of miR-99b overexpression/inhibition on PCa cell survival/proliferation, spheroid formation, and cell migration were examined by specific assays. Luciferase reporter assays were performed to determine the binding of miR-99b to 3' untranslated region (UTR) of the mTOR gene. The effects of miR-99b on the expression of mTOR, AR, and PSA proteins, as well as on AKT/mTOR signaling, autophagy, and neuroendocrine differentiation markers were analyzed by western blotting. The expression of miR-99b, mTOR, AR, PSA in AR-negative PC3 and AR-positive LNCaP cells was analyzed by RT/qPCR. The effect of miR-99b on global gene expression in PC3 cells was analyzed by RNA-seq.. The expression of miR-99b was downregulated in tumor samples from PCa patients, whereas the expression of mTOR and AR was upregulated. In PCa cell lines, overexpression of miR-99b inhibited cell proliferation and cell colony/spheroid formation; induced apoptosis, and increased sensitivity towards docetaxel (DTX). In contrast, inhibition of miR-99b by miR-99b inhibitor resulted in increased cell growth in PCa cells. Mechanistically, miR-99b inhibited the expression of the mammalian target of the rapamycin (mTOR) gene by binding to its 3' UTR and induced autophagy. Furthermore, miR-99b inhibited androgen receptor (AR) activity in LNCaP cells and induced apoptosis. Activation of AR signaling by dihydrotestosterone (DHT) downregulated miR-99b expression and promoted cell PCa cell growth/survival, whereas inactivation of mTOR by rapamycin or AR by enzalutamide decreased miR-99b mediated PCa cell growth.. Our data suggest that miR-99b functions as a tumor suppressor by targeting the mTOR/AR axis in PCa cells, implicating miR-99b as a novel biomarker and therapeutic target for PCa management.

Topics: 3' Untranslated Regions; Autophagy; Cell Line, Tumor; Cell Movement; Cell Proliferation; Gene Expression Regulation, Neoplastic; Humans; Male; MicroRNAs; Prostate-Specific Antigen; Prostatic Neoplasms; Sirolimus; TOR Serine-Threonine Kinases

Inhibition of mammalian target of rapamycin complex 1 (mTORC1) with rapamycin in the absence of transforming growth factor-β (TGFβ) signaling induces apoptosis in many cancer cell lines. In the presence of TGFβ, rapamycin induces G

Topics: Apoptosis; Cell Cycle; Cell Line, Tumor; Cyclin-Dependent Kinase Inhibitor p16; Drug Resistance, Neoplasm; E2F Transcription Factors; Humans; Lung Neoplasms; Male; Mutation; Phosphorylation; Prostatic Neoplasms; Retinoblastoma Protein; Signal Transduction; Sirolimus; Transforming Growth Factor beta

Mammalian target of rapamycin (mTOR) is a downstream substrate activated by PI3K/AKT pathway and it is essential for cell migration. It exists as two complexes: mTORC1 and mTORC2. mTORC1 is known to be regulated by active AKT, but the activation of mTORC2 is poorly understood. In this study, we investigated the roles and differential activation of the two mTOR complexes during cell migration in prostate cancer cells.. We used small interfering RNA to silence the expression of Rac1 and the main components of mTOR complexes (regulatory associated protein of mTOR [RAPTOR] and rapamycin-insensitive companion of mTOR [RICTOR]) in LNCaP, DU145, and PC3 prostate cancer cell lines. We performed transwell migration assay to evaluate the migratory capability of the cells, and Western blot analysis to study the activation levels of mTOR complexes.. Specific knockdown of RAPTOR and RICTOR caused a decrease of cell migration, suggesting their essential role in prostate cancer cell movement. Furthermore, epidermal growth factor (EGF) treatments induced the activation of both the mTOR complexes. Lack of Rac1 activity in prostate cancer cells blocked EGF-induced activation of mTORC2, but had no effect on mTORC1 activation. Furthermore, the overexpression of constitutively active Rac1 resulted in significant increase in cell migration and activation of mTORC2 in PC3 cells, but had no effect on mTORC1 activation. Active Rac1 was localized in the plasma membrane and was found to be in a protein complex, with RICTOR, but not RAPTOR.. We suggest that EGF-induced activation of Rac1 causes the activation of mTORC2 via RICTOR. This mechanism plays a critical role in prostate cancer cell migration.

Topics: Aminoquinolines; Cell Line, Tumor; Cell Movement; Epidermal Growth Factor; Gene Knockdown Techniques; Humans; Male; Mechanistic Target of Rapamycin Complex 1; Mechanistic Target of Rapamycin Complex 2; PC-3 Cells; Prostatic Neoplasms; Pyrimidines; rac1 GTP-Binding Protein; Rapamycin-Insensitive Companion of mTOR Protein; Regulatory-Associated Protein of mTOR; RNA, Small Interfering; Sirolimus

Chemotherapy with docetaxel (DTX) is used for castration-resistant prostate cancer (CRPC), but it is inadequate.. We evaluated the effect of the combination treatment DTX and the mTOR inhibitor temsirolimus (TEM) in the PC3 prostate cancer cell line, by focusing on the induction of autophagy and apoptosis.. TEM induced autophagy but not apoptosis even at a high dose, whereas DTX induced apoptosis. The combination of low-dose DTX and TEM caused a 34% suppression in cell proliferation compared to monotherapy with a higher dose of DTX. The induction of apoptosis was increased by their combination. The combination with DTX overcame the induction of autophagy by TEM. The combination treatment suppressed tumor growth 72% less than the control group after 14 days of treatment in vivo.. The combination of TEM and DTX induced apoptosis by overcoming autophagy and enhanced the anticancer effect compared to monotherapy.

Topics: Animals; Antineoplastic Agents; Apoptosis; Autophagy; Cell Line, Tumor; Cell Proliferation; Combined Modality Therapy; Docetaxel; Humans; Male; Mice; Mice, Inbred BALB C; Mice, Nude; PC-3 Cells; Prostate; Prostatic Neoplasms; Protein Kinase Inhibitors; Sirolimus

Therapeutic strategies targeting both cancer cells and associated cells in the tumor microenvironment offer significant promise in cancer therapy. We previously reported that generation 5 (G5) dendrimers conjugated with cyclic-RGD peptides target cells expressing integrin alpha V beta 3. In this study, we report a novel dendrimer conjugate modified to deliver the mammalian target of rapamycin (mTOR) inhibitor, rapamycin. In vitro analyses demonstrated that this drug conjugate, G5-FI-RGD-rapamycin, binds to prostate cancer (PCa) cells and fibroblasts to inhibit mTOR signaling and VEGF expression. In addition, G5-FI-RGD-rapamycin inhibits mTOR signaling in cancer cells more efficiently under proinflammatory conditions compared to free rapamycin. In vivo studies established that G5-FI-RGD-rapamycin significantly inhibits fibroblast-mediated PCa progression and metastasis. Thus, our results suggest the potential of new rapamycin-conjugated multifunctional nanoparticles for PCa therapy.

Topics: Animals; Blotting, Western; Cell Line, Tumor; Cells, Cultured; Dendrimers; Fibroblasts; Flow Cytometry; Humans; Integrin alphaVbeta3; Male; Mice; Neoplasm Metastasis; PC-3 Cells; Peptides, Cyclic; Prostatic Neoplasms; Sirolimus

Akt activation in human cancers exerts chemoresistance, but pan-Akt inhibition elicits adverse consequences. We exploited the consequences of Akt-mediated mitochondrial and glucose metabolism to selectively eradicate and evade chemoresistance of prostate cancer displaying hyperactive Akt. PTEN-deficient prostate cancer cells that display hyperactivated Akt have high intracellular reactive oxygen species (ROS) levels, in part, because of Akt-dependent increase of oxidative phosphorylation. High intracellular ROS levels selectively sensitize cells displaying hyperactive Akt to ROS-induced cell death enabling a therapeutic strategy combining a ROS inducer and rapamycin in PTEN-deficient prostate tumors in mouse models. This strategy elicited tumor regression, and markedly increased survival even after the treatment was stopped. By contrast, exposure to antioxidant increased prostate tumor progression. To increase glucose metabolism, Akt activation phosphorylated HK2 and induced its expression. Indeed, HK2 deficiency in mouse models of Pten-deficient prostate cancer elicited a marked inhibition of tumor development and extended lifespan.

Topics: Animals; Antibiotics, Antineoplastic; Cell Line, Tumor; Disease Models, Animal; Humans; Male; Mice; Models, Biological; Neoplasm Transplantation; Oncogene Protein v-akt; Oxidative Phosphorylation; Prostatic Neoplasms; Reactive Oxygen Species; Sirolimus; Treatment Outcome

Prostate cancer incidence increases with age; along with many other cancers, it could be considered a disease of aging. Prostate cancer screening has led to a significant proportion of men diagnosed with low-grade, low-stage prostate cancer who are now more likely to choose an active surveillance strategy rather than definitive treatments. Definitive treatment, such as surgery and radiation therapy, is useful for high-grade disease; however, because of the low long-term risk of progression of a low-grade disease and side effects of surgery and radiation, these treatments are less commonly used for low-grade disease. While five alpha reductase inhibitors have been shown to reduce the risk of cancer detection on subsequent biopsies for men on active surveillance, no medications have been proven to prevent progression to high-grade disease. mTOR pathways have long been known to influence prostate cancer and are targets in various prostate cancer patient populations. Low-dose mTOR inhibition with rapamycin has shown promise in pre-clinical models of prostate cancer and appear to affect cellular senescence and immunomodulation in the aging population. We hypothesize that low-dose mTOR inhibition could reduce progression of low-grade prostate cancer patients, allowing them to remain on active surveillance.

Topics: 5-alpha Reductase Inhibitors; Aged; Animals; Cell Line, Tumor; Cellular Senescence; Disease Progression; Early Detection of Cancer; Glucose Intolerance; Humans; Magnetic Resonance Imaging; Male; Mice; Middle Aged; Models, Theoretical; Prostate; Prostate-Specific Antigen; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; Receptors, Androgen; Sirolimus; TOR Serine-Threonine Kinases

Topics: Animals; Apoptosis; Cell Line, Tumor; Cell Proliferation; Chromones; Dose-Response Relationship, Drug; Humans; Male; Mice; Mice, Inbred BALB C; Mice, Nude; Morpholines; NIH 3T3 Cells; Oligopeptides; Phosphatidylinositol 3-Kinases; Phosphorylation; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; S Phase Cell Cycle Checkpoints; Sea Anemones; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Xenograft Model Antitumor Assays

Phenotypic assays were performed in prostate cancer cell lines to describe the biological activity of PI3K-AKT-mTOR pathway inhibitors retrieved from the virtual screening initiative. These novel chemicals share in common the aminopyridine scaffold, hitting PC-3 cells in macromolar range, with selectivity index over fibroblast cell lines. Moreover, a preliminary study of the mode of action by flow cytometry assay pointed out that these compounds had a rapamycin-like response for the PI3K-AKT-mTOR pathway modulation.

Topics: Animals; Antineoplastic Agents; BALB 3T3 Cells; Cell Line, Tumor; Cell Proliferation; Cell Survival; Dose-Response Relationship, Drug; Drug Screening Assays, Antitumor; Fibroblasts; Humans; Male; Mice; Mice, Inbred BALB C; Molecular Structure; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Prostatic Neoplasms; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Structure-Activity Relationship; TOR Serine-Threonine Kinases

Advanced prostate cancers that are resistant to all current therapies create a need for new therapeutic strategies. One recent innovative approach to cancer therapy is the simultaneous use of multiple FDA-approved drugs to target multiple pathways. A challenge for this approach is caused by the different solubility requirements of each individual drug, resulting in the need for a drug vehicle that is non-toxic and capable of carrying multiple water-insoluble antitumor drugs. Micelles have recently been shown to be new candidate drug solubilizers for anti cancer therapy.. This study set out to examine the potential use of multi-drug loaded micelles for prostate cancer treatment in preclinical models including cell line and mouse models for prostate cancers with Pten deletions. Specifically antimitotic agent docetaxel, mTOR inhibitor rapamycin, and HSP90 inhibitor 17-N-allylamino-17-demethoxygeldanamycin were incorporated into the micelle system (DR17) and tested for antitumor efficacy.. In vitro growth inhibition of prostate cancer cells was greater when all three drugs were used in combination compared to each individual drug, and packaging the drugs into micelles enhanced the cytotoxic effects. At the molecular level DR17 targeted simultaneously several molecular signaling axes important in prostate cancer including androgen receptor, mTOR, and PI3K/AKT. In a mouse genetic model of prostate cancer, DR17 treatment decreased prostate weight, which was achieved by both increasing caspase-dependent cell death and decreasing cell proliferation. Similar effects were also observed when DR17 was administered to nude mice bearing prostate cancer cells xenografts.. These results suggest that combining these three cancer drugs in multi-drug loaded micelles may be a promising strategy for prostate cancer therapy.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Benzoquinones; Cell Line, Tumor; Cell Proliferation; Docetaxel; HSP90 Heat-Shock Proteins; Immunoblotting; Lactams, Macrocyclic; Male; Mice, Knockout; Mice, Transgenic; Micelles; Molecular Targeted Therapy; Neoplasms, Experimental; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; PTEN Phosphohydrolase; Signal Transduction; Sirolimus; Taxoids; TOR Serine-Threonine Kinases

Deregulation of phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway contributes to prostate cancer development and progression. Here, we compared the in vitro effects of the dual PI3K/mTOR inhibitor (XL765) with those observed with the sole PI3K (XL147) or mTOR (rapamycin) inhibition in 2 non-tumor prostate epithelial cell lines, 8 prostate cancer cell lines, and 11 prostate cancer cell derivatives. We demonstrated that the XL765 treatment showed superior and proliferative effects of XL147 or rapamycin. The XL765 effects were associated to increasing the chromosome region maintenance 1 (CRM1)-mediated nuclear localization of glycogen synthase kinase 3 beta (GSK3β) and Foxo-1a with higher induction of apoptosis when compared to those observed in XL147 and rapamycin treatments. IC50 values were calculated in phosphatase and tensin homologue deleted on chromosome 10 (PTEN)-positive and PTEN-negative cell lines as well as after PTEN transfection or PTEN downmodulation by siRNA strategy revealing that the presence of this protein was associated with reduced sensitivity to PI3K and mTOR inhibitors. The comparison of IC50 values was also calculated for androgen-dependent and -independent cell lines as well as after androgen receptor (AR) transfection or the AR downmodulation by siRNA strategy revealing that androgen independence was associated with enhanced responsiveness. Our results provide a rationale to use the dual PI3K/Akt/mTOR inhibitors in hormone-insensitive prostate cancer models due to the overactivity of PI3K/Akt/mTOR in this disease condition.

Topics: Apoptosis; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Drug Resistance, Neoplasm; Forkhead Box Protein O1; Glycogen Synthase Kinase 3 beta; Humans; Inhibitory Concentration 50; Male; Phosphoinositide-3 Kinase Inhibitors; Prostatic Neoplasms; Quinoxalines; Receptors, Androgen; RNA, Small Interfering; Sirolimus; Sulfonamides; TOR Serine-Threonine Kinases

A 63-year-old African male with end stage renal disease who received a renal transplantation from his daughter after successful treatment of hepatitis C virus, type 1 genotype developed metastatic Kaposi's sarcoma and subsequently adenocarcinoma of the prostate. He was successfully treated with chemotherapy and reduction of immunosuppression and switch over to rapamycin.

Topics: Adenocarcinoma; Antineoplastic Agents; Biopsy; Black People; Drug Substitution; Humans; Immunosuppressive Agents; Kidney Failure, Chronic; Kidney Transplantation; Living Donors; Male; Middle Aged; Neoplasms, Second Primary; Prostatic Neoplasms; Sarcoma, Kaposi; Sirolimus; Skin Neoplasms; Tanzania; Time Factors; Treatment Outcome

The mammalian target of rapamycin (mTOR) plays essential roles in the regulation of growth-related processes such as protein synthesis, cell sizing and metabolism in both normal and pathological growing conditions. These functions of mTOR are thought to be largely a consequence of its cytoplasmic activity in regulating translation rate, but accumulating data highlight supplementary role(s) for this serine/threonine kinase within the nucleus. Indeed, the nuclear activities of mTOR are currently associated with the control of protein biosynthetic capacity through its ability to regulate the expression of gene products involved in the control of ribosomal biogenesis and proliferation. Using primary murine embryo fibroblasts (MEFs), we observed that cells with overactive mTOR signaling displayed higher abundance for the growth-associated Npm1 protein, in what represents a novel mechanism of Npm1 gene regulation. We show that Npm1 gene expression is dependent on mTOR as demonstrated by treatment of wild-type and Pten inactivated MEFs cultured with rapamycin or by transient transfections of small interfering RNA directed against mTOR. In accordance, the mTOR kinase localizes to the Npm1 promoter gene in vivo and it enhances the activity of a human NPM1-luciferase reporter gene providing an opportunity for direct control. Interestingly, rapamycin did not dislodge mTOR from the Npm1 promoter but rather strongly destabilized the Npm1 transcript by increasing its turnover. Using a prostate-specific Pten-deleted mouse model of cancer, Npm1 mRNA levels were found up-regulated and sensitive to rapamycin. Finally, we also showed that Npm1 is required to promote mTOR-dependent cell proliferation. We therefore proposed a model whereby mTOR is closely involved in the transcriptional and posttranscriptional regulation of Npm1 gene expression with implications in development and diseases including cancer.

Topics: Animals; Cell Proliferation; Cells, Cultured; HeLa Cells; Humans; Male; Mice; Mice, Knockout; Nuclear Proteins; Nucleophosmin; Promoter Regions, Genetic; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; PTEN Phosphohydrolase; RNA Interference; RNA, Messenger; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Transplantation, Heterologous; Up-Regulation

This study investigated the effects of matrix on the behaviors of 3D-cultured cells of two prostate cancer cell lines, LNCaP and DU145. Two biologically-derived matrices, Matrigel and Cultrex BME, and one synthetic matrix, the Alvetex scaffold, were used to culture the cells. The cell proliferation rate, cellular response to anti-cancer drugs, and expression levels of proteins associated with drug sensitivity/resistance were examined and compared amongst the 3D-cultured cells on the three matrices and 2D-cultured cells. The cellular responses upon treatment with two common anti-cancer drugs, Docetaxel and Rapamycin, were examined. The expressions of epidermal growth factor receptor (EGFR) and β-III tubulin in DU145 cells and p53 in LNCaP cells were examined. The results showed that the proliferation rates of cells cultured on the three matrices varied, especially between the synthetic matrix and the biologically-derived matrices. The drug responses and the expressions of drug sensitivity-associated proteins differed between cells on various matrices as well. Among the 3D cultures on the three matrices, increased expression of β-III tubulin in DU145 cells was correlated with increased resistance to Docetaxel, and decreased expression of EGFR in DU145 cells was correlated with increased sensitivity to Rapamycin. Increased expression of a p53 dimer in 3D-cultured LNCaP cells was correlated with increased resistance to Docetaxel. Collectively, the results showed that the matrix of 3D cell culture models strongly influences cellular behaviors, which highlights the imperative need to achieve standardization of 3D cell culture technology in order to be used in drug screening and cell biology studies.

Topics: Antineoplastic Agents; Biocompatible Materials; Cell Culture Techniques; Cell Line, Tumor; Cell Proliferation; Collagen; Docetaxel; Drug Combinations; ErbB Receptors; Humans; Laminin; Male; Prostatic Neoplasms; Proteoglycans; Sirolimus; Taxoids; Tubulin; Tubulin Modulators; Tumor Suppressor Protein p53

Androgen receptor (AR) and PI3K/AKT/mTORC1 are major survival signals that drive prostate cancer to a lethal disease. Reciprocal activation of these oncogenic pathways from negative cross talks contributes to low/limited success of pathway-selective inhibitors in curbing prostate cancer progression. We report that the antibiotic salinomycin, a cancer stem cell blocker, is a dual-acting AR and mTORC1 inhibitor, inhibiting PTEN-deficient castration-sensitive and castration-resistant prostate cancer in culture and xenograft tumors. AR expression, its transcriptional activity, and androgen biosynthesis regulating enzymes CYP17A1, HSD3β1 were reduced by sub-micro molar salinomycin. Estrogen receptor-α expression was unchanged. Loss of phosphorylated AR at serine-81, which is an index for nuclear AR activity, preceded total AR reduction. Rapamycin enhanced the AR protein level without altering phosphoAR-Ser81 and CYP17A1. Inactivation of mTORC1, evident from reduced phosphorylation of mTOR and downstream effectors, as well as AMPK activation led to robust autophagy induction. Apoptosis increased modestly, albeit significantly, by sub-micro molar salinomycin. Enhanced stimulatory TSC2 phosphorylation at Ser-1387 by AMPK, and reduced inhibitory TSC2 phosphorylation at Ser-939/Thr-1462 catalyzed by AKT augmented TSC2/TSC1 activity, which led to mTORC1 inhibition. AMPK-mediated raptor phosphorylation further reduced mTOR's kinase function and mTORC1 activity. Our novel finding on dual inhibition of AR and mTORC1 suggests that salinomycin is potentially active as monotherapy against advanced prostate cancer.

Topics: AMP-Activated Protein Kinases; Androgen Receptor Antagonists; Animals; Antibiotics, Antineoplastic; Apoptosis; Cell Line, Tumor; Cell Proliferation; Estrogen Receptor alpha; Humans; Male; Mechanistic Target of Rapamycin Complex 1; Mice; Mice, Nude; Multienzyme Complexes; Phosphatidylinositol 3-Kinases; Phosphorylation; Progesterone Reductase; Prostatic Neoplasms; Prostatic Neoplasms, Castration-Resistant; Proto-Oncogene Proteins c-akt; PTEN Phosphohydrolase; Pyrans; Receptors, Androgen; Serine; Signal Transduction; Sirolimus; Steroid 17-alpha-Hydroxylase; Steroid Isomerases; Tuberous Sclerosis Complex 1 Protein; Tuberous Sclerosis Complex 2 Protein; Tumor Suppressor Proteins; Xenograft Model Antitumor Assays

Hyperpolarized magnetic resonance spectroscopy (HP MRS) using dynamic nuclear polarization (DNP) is a technique that has greatly enhanced the sensitivity of detecting (13)C nuclei. However, the HP MRS polarization decays in the liquid state according to the spin-lattice relaxation time (T1) of the nucleus. Sampling of the signal also destroys polarization, resulting in a limited temporal ability to observe biologically interesting reactions. In this study, we demonstrate that sampling hyperpolarized signals using a permanent magnet at 1 Tesla (1T) is a simple and cost-effective method to increase T1s without sacrificing signal-to-noise. Biologically-relevant information may be obtained with a permanent magnet using enzyme solutions and in whole cells. Of significance, our findings indicate that changes in pyruvate metabolism can also be quantified in a xenograft model at this field strength.

Topics: Animals; Antibiotics, Antineoplastic; Humans; Lactic Acid; Magnetic Fields; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Male; Mice, Inbred NOD; Mice, SCID; Prostatic Neoplasms; Pyruvic Acid; Sarcoma; Sirolimus; Tumor Cells, Cultured; Xenograft Model Antitumor Assays

Topics: Animals; Antimitotic Agents; Apoptosis; Cell Cycle Checkpoints; Cell Line, Tumor; Cell Proliferation; Humans; Male; Mice, Inbred BALB C; Mice, Nude; Microtubules; Polymerization; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; Quinolones; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Tubulin; Up-Regulation

Autophagy is a cellular degradation process for the recycling of damaged or superfluous intracellular compartments to provide an alternative energy source during periods of metabolic stress for maintaining cell homeostasis and viability. Although autophagy in different contexts have been shown to use similar signaling pathways, the exact molecular regulation of autophagy has been found to be cell-type dependent.. We used rapamycin to trigger autophagy and used nitric oxide (NO) to inhibit autophagy in prostate cancer cells. IWP-2 was used to inhibit β-catenin signaling. Autophagy-associated proteins were examined by Western blot.. We found that nitric oxide (NO), a potent cellular messenger, impaired rapamycin-induced autophagy in prostate cancer cells. Further analyses showed that NO induced nuclear accumulation of β-catenin, a key factor of Wnt signaling pathway, to inhibit autophagy in prostate cancer cells.. We demonstrate involvement of β-catenin signaling in the regulation of autophagy of prostate cancer cells. Our results shed light on a previously unappreciated β-catenin signaling pathway for regulating autophagy in prostate cancer.

Topics: Apoptosis; Autophagy; beta Catenin; Cell Line, Tumor; Cell Proliferation; Cell Transformation, Neoplastic; Gene Expression Regulation, Neoplastic; Humans; Male; Nitric Oxide; Prostatic Neoplasms; Sirolimus; Wnt Signaling Pathway

New therapies are required for castrate-resistant prostate cancer (CRPC), and growth-arrest specific 5 (GAS5) lncRNA, which riborepresses androgen receptor action, may offer novel opportunities in this regard. This lncRNA promotes the apoptosis of prostate cancer cells and its levels decline as prostate cancer cells acquire castrate-resistance, so that enhancing GAS5 expression may improve the effectiveness of chemotherapies. Since GAS5 is a member of the 5' terminal oligopyrimidine gene family, we have examined mTOR inhibition as a strategy to increase GAS5 expression. Furthermore, we have determined if GAS5 itself mediates the action of mTOR inhibitors, as demonstrated for other chemotherapeutic agents in prostate cancer cells.. The effects of mTOR inhibitors on GAS5 lncRNA levels and cell growth were determined in a range of prostate cancer cell lines. Transfection of cells with GAS5 siRNAs and plasmid constructs was performed to determine the involvement of GAS5 lncRNA in mTOR inhibitor action.. First generation mTORC1, combined mTORC1/mTORC2 and dual PI3K/mTOR inhibitors all increased cellular GAS5 levels and inhibited culture growth in androgen-dependent (LNCaP) and androgen-sensitive (22Rv1) cell lines, but not in androgen-independent (PC-3 and DU 145) cell lines. The latter exhibited low endogenous GAS5 expression, and GAS5 silencing in LNCaP and 22Rv1 cells decreased the sensitivity to mTOR inhibitors, whereas transfection of GAS5 lncRNA sensitized PC-3 and DU 145 cells to these agents.. mTOR inhibition enhances GAS5 transcript levels in certain prostate cancer cell lines. This selectivity is likely to be related to endogenous GAS5 expression levels, since GAS5 lncRNA is itself required for mTOR inhibitor action in prostate cancer cells.

Topics: Cell Line, Tumor; Cell Proliferation; Gene Expression Regulation, Neoplastic; Humans; Male; Neoplasms, Hormone-Dependent; Prostatic Neoplasms; Reverse Transcriptase Polymerase Chain Reaction; RNA, Long Noncoding; RNA, Neoplasm; RNA, Small Interfering; Sirolimus; TOR Serine-Threonine Kinases

Lipogenesis inhibition was reported to induce apoptosis and repress proliferation of cancer cells while barely affecting normal cells. Lipins exhibit dual function as enzymes catalyzing the dephosphorylation of phosphatidic acid to diacylglycerol and as co-transcriptional regulators. Thus, they are able to regulate lipid homeostasis at several nodal points. Here, we show that lipin-1 is up-regulated in several cancer cell lines and overexpressed in 50 % of high grade prostate cancers. The proliferation of prostate and breast cancer cells, but not of non-tumorigenic cells, was repressed upon lipin-1 knock-down. Lipin-1 depletion also decreased cancer cell migration through RhoA activation. Lipin-1 silencing did not significantly affect global lipid synthesis but enhanced the cellular concentration of phosphatidic acid. In parallel, autophagy was induced while AKT and ribosomal protein S6 phosphorylation were repressed. We also observed a compensatory regulation between lipin-1 and lipin-2 and demonstrated that their co-silencing aggravates the phenotype induced by lipin-1 silencing alone. Most interestingly, lipin-1 depletion or lipins inhibition with propranolol sensitized cancer cells to rapamycin. These data indicate that lipin-1 controls main cellular processes involved in cancer progression and that its targeting, alone or in combination with other treatments, could open new avenues in anticancer therapy.

Topics: Antibiotics, Antineoplastic; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Autophagy; Breast Neoplasms; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cell Survival; Dose-Response Relationship, Drug; Female; Humans; Lipogenesis; Male; Molecular Targeted Therapy; Nuclear Proteins; Phosphatidate Phosphatase; Phosphorylation; Propranolol; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; rhoA GTP-Binding Protein; Ribosomal Protein S6; RNA Interference; Signal Transduction; Sirolimus; Time Factors; TOR Serine-Threonine Kinases; Transfection

In this study, we compared the effect of oral administration of metformin (MET) and rapamycin (RAPA) alone or in combination on prostate cancer development and progression in HiMyc mice. MET (250 mg/kg body weight in the drinking water), RAPA (2.24 mg/kg body weight microencapsulated in the diet), and the combination inhibited progression of prostatic intraepithelial neoplasia lesions to adenocarcinomas in the ventral prostate (VP). RAPA and the combination were more effective than MET at the doses used. Inhibition of prostate cancer progression in HiMyc mice by RAPA was associated with a significant reduction in mTORC1 signaling that was further potentiated by the combination of MET and RAPA. In contrast, treatment with MET alone enhanced AMPK activation, but had little or no effect on mTORC1 signaling pathways in the VP of HiMyc mice. Further analyses revealed a significant effect of all treatments on prostate tissue inflammation as assessed by analysis of the expression of cytokines, the presence of inflammatory cells and NFκB signaling. MET at the dose used appeared to reduce prostate cancer progression primarily by reducing tissue inflammation whereas RAPA and the combination appeared to inhibit prostate cancer progression in this mouse model via the combined effects on both mTORC1 signaling as well as on tissue inflammation. Overall, these data support the hypothesis that blocking mTORC1 signaling and/or tissue inflammation can effectively inhibit prostate cancer progression in a relevant mouse model of human prostate cancer. Furthermore, combinatorial approaches that target both pathways may be highly effective for prevention of prostate cancer progression in men.

Topics: Adenocarcinoma; Animals; Antineoplastic Combined Chemotherapy Protocols; Blotting, Western; Cell Proliferation; Disease Models, Animal; Disease Progression; Immunohistochemistry; Male; Metformin; Mice; Prostatic Neoplasms; Real-Time Polymerase Chain Reaction; Sirolimus

An important strategy for improving advanced PCa treatment is targeted therapies combined with chemotherapy. PC-1, a prostate Leucine Zipper gene (PrLZ), is specifically expressed in prostate tissue as an androgen-induced gene and is up-regulated in advanced PCa. Recent work confirmed that PC-1 expression promotes PCa growth and androgen-independent progression. However, how this occurs and whether this can be used as a biomarker is uncertain. Here, we report that PC-1 overexpression confers PCa cells resistance to rapamycin treatment by antagonizing rapamycin-induced cytostasis and autophagy (rapamycin-sensitivity was observed in PC-1-deficient (shPC-1) C4-2 cells). Analysis of the mTOR pathway in PCa cells with PC-1 overexpressed and depressed revealed that eukaryotic initiation factor 4E-binding protein 1(4E-BP1) was highly regulated by PC-1. Immunohistochemistry assays indicated that 4E-BP1 up-regulation correlates with increased PC-1 expression in human prostate tumors and in PCa cells. Furthermore, PC-1 interacts directly with 4E-BP1 and stabilizes 4E-BP1 protein via inhibition of its ubiquitination and proteasomal degradation. Thus, PC-1 is a novel regulator of 4E-BP1 and our work suggests a potential mechanism through which PC-1 enhances PCa cell survival and malignant progression and increases chemoresistance. Thus, the PC-1-4E-BP1 interaction may represent a therapeutic target for treating advanced PCa.

Topics: Adaptor Proteins, Signal Transducing; Biomarkers, Tumor; Cell Cycle Proteins; Cell Line, Tumor; Disease Progression; Humans; Male; Phosphoproteins; Phosphoric Diester Hydrolases; Phosphorylation; Prostatic Neoplasms; Pyrophosphatases; Signal Transduction; Sirolimus

The TOR (target of rapamycin) kinase limits longevity by poorly understood mechanisms. Rapamycin suppresses the mammalian TORC1 complex, which regulates translation, and extends lifespan in diverse species, including mice. We show that rapamycin selectively blunts the pro-inflammatory phenotype of senescent cells. Cellular senescence suppresses cancer by preventing cell proliferation. However, as senescent cells accumulate with age, the senescence-associated secretory phenotype (SASP) can disrupt tissues and contribute to age-related pathologies, including cancer. MTOR inhibition suppressed the secretion of inflammatory cytokines by senescent cells. Rapamycin reduced IL6 and other cytokine mRNA levels, but selectively suppressed translation of the membrane-bound cytokine IL1A. Reduced IL1A diminished NF-κB transcriptional activity, which controls much of the SASP; exogenous IL1A restored IL6 secretion to rapamycin-treated cells. Importantly, rapamycin suppressed the ability of senescent fibroblasts to stimulate prostate tumour growth in mice. Thus, rapamycin might ameliorate age-related pathologies, including late-life cancer, by suppressing senescence-associated inflammation.

Topics: Animals; Anti-Inflammatory Agents; Antineoplastic Agents; Cell Line, Tumor; Cell Proliferation; Cellular Senescence; Dose-Response Relationship, Drug; Fibroblasts; Gene Expression Regulation, Neoplastic; Humans; Inflammation Mediators; Interleukin-1alpha; Interleukin-6; Male; Mice, SCID; Mitoxantrone; NF-kappa B; Phenotype; Prostatic Neoplasms; RNA Interference; RNA, Messenger; Sirolimus; Time Factors; TOR Serine-Threonine Kinases; Transcription, Genetic; Transfection; Tumor Burden; Up-Regulation; Xenograft Model Antitumor Assays

PTEN is one of the most frequently mutated tumor suppressor genes in human cancers. The role of PTEN in carcinogenesis has been validated by knockout mouse models. PTEN heterozygous mice develop neoplasms in multiple organs. Unfortunately, the embryonic lethality of biallelic excision of PTEN has inhibited the study of complete PTEN deletion in the development and progression of cancer. By crossing PTEN conditional knockout mice with transgenic mice expressing a tamoxifen-inducible Cre-ER(T) under the control of a chicken actin promoter, we have generated a tamoxifen-inducible mouse model that allows temporal control of PTEN deletion. Interestingly, administration of a single dose of tamoxifen resulted in PTEN deletion mainly in epithelial cells, but not in stromal, mesenchymal or hematopoietic cells. Using the mT/mG double-fluorescent Cre reporter mice, we demonstrate that epithelial-specific PTEN excision was caused by differential Cre activity among tissues and cells types. Tamoxifen-induced deletion of PTEN resulted in extremely rapid and consistent formation of endometrial in situ adenocarcinoma, prostate intraepithelial neoplasia and thyroid hyperplasia. We also analyzed the role of PTEN ablation in other epithelial cells, such as the tubular cells of the kidney, hepatocytes, colonic epithelial cells or bronchiolar epithelium, but those tissues did not exhibit neoplastic growth. Finally, to validate this model as a tool to assay the efficacy of anti-tumor drugs in PTEN deficiency, we administered the mTOR inhibitor everolimus to mice with induced PTEN deletion. Everolimus dramatically reduced the progression of endometrial proliferations and significantly reduced thyroid hyperplasia. This model could be a valuable tool to study the cell-autonomous mechanisms involved in PTEN-loss-induced carcinogenesis and provides a good platform to study the effect of anti-neoplastic drugs on PTEN-negative tumors.

Topics: Adenocarcinoma; Alleles; Animals; Disease Models, Animal; Dose-Response Relationship, Drug; Endometrial Neoplasms; Endometrium; Epithelial Cells; Everolimus; Female; Gene Deletion; Humans; Hyperplasia; Integrases; Male; Mice; Mice, Knockout; Precancerous Conditions; Prostatic Intraepithelial Neoplasia; Prostatic Neoplasms; PTEN Phosphohydrolase; Recombination, Genetic; Sirolimus; Stromal Cells; Tamoxifen; Thyroid Gland; Thyroid Neoplasms

The gastrin-releasing peptide receptor (GRPr) is overexpressed in prostate cancer and is an attractive target for radionuclide therapy. In addition, inhibition of the protein kinase mammalian target of rapamycin (mTOR) has been shown to sensitize various cancer cells to the effects of radiotherapy.. To determine the effect of treatment with rapamycin and radiotherapy with a novel (177)Lu-labeled GRPr antagonist ((177)Lu-RM2, BAY 1017858) alone and in combination, in vitro and in vivo studies were performed using the human PC-3 prostate cancer cell line. PC-3 cell proliferation and (177)Lu-RM2 uptake after treatment with rapamycin were assessed in vitro. To determine the influence of rapamycin on (177)Lu-RM2 tumor uptake, in vivo small-animal PET studies with (68)Ga-RM2 were performed after treatment with rapamycin. To study the efficacy of (177)Lu-RM2 in vivo, mice with subcutaneous PC-3 tumors were treated with (177)Lu-RM2 alone or after pretreatment with rapamycin.. Stable expression of GRPr was maintained after rapamycin treatment with doses up to 4 mg/kg in vivo. Monotherapy with (177)Lu-RM2 at higher doses (72 and 144 MBq) was effective in inducing complete tumor remission in 60% of treated mice. Treatment with 37 MBq of (177)Lu-RM2 and rapamycin in combination led to significantly longer survival than with either agent alone. No treatment-related toxicity was observed.. Radiotherapy using a (177)Lu-labeled GRPr antagonist alone or in combination with rapamycin was efficacious in inhibiting in vivo tumor growth and may be a promising strategy for treatment of prostate cancer.

Topics: Animals; Cell Line, Tumor; Combined Modality Therapy; Female; Gene Expression Regulation, Neoplastic; Humans; Lutetium; Male; Mice; Molecular Targeted Therapy; Oligopeptides; Prostatic Neoplasms; Radioisotopes; Receptors, Bombesin; Sirolimus

A three layer (trilayer) polymeric micelle system based on the self-association of the triblock polymer poly(ethylene glycol)-b-poly{N-[N-(2-aminoethyl)-2-aminoethyl] aspartamide}-b-poly(ε-caprolactone) (PEG-b-PAsp(DET)-b-PCL) has been synthesized and investigated for combination delivery of rapamycin (RAP) and siRNA targeting Y-box binding protein-1 (siYB-1). The trilayer micelle is composed of (a) a hydrophilic poly(ethylene glycol) (PEG) block constituting the outer layer to improve pharmacokinetics, (b) an intermediate compartment composed of the cationic poly{2-[(2-aminoethyl)amino] ethyl aspartamide} (PAsp(DET)) segment for interacting with siYB-1, and (c) an inner hydrophobic poly(ε-caprolactone) (PCL) compartment for encapsulation of RAP. A major advantage of this system is biocompatibility since PEG and PCL are both approved by the FDA, and PAsp(DET) is a non-toxic pH responsive cationic poly(amino acid)-based polymer. In this study, it has been shown that PCL can encapsulate RAP with high loading efficiencies, and PAsp(DET) can successfully interact with siRNA for efficient transfection/knockdown with negligible cytotoxicity. The enhanced therapeutic efficacy of RAP/siYB-1 micelles was demonstrated in cell cultures and in a PC3 xenograft nude mouse model of human prostate cancer. Herein, we demonstrate that trilayer micelles are a promising approach to improve the simultaneous delivery of combination siRNA/drug therapies.

Topics: Animals; Drug Carriers; Humans; Male; Mice; Mice, Nude; Micelles; Prostatic Neoplasms; RNA, Small Interfering; Sirolimus; Y-Box-Binding Protein 1

Tumor-specific adenoviral vectors comprise a fruitful gene-based diagnostic imaging and therapy research area for advanced stage of cancer, including metastatic disease. However, clinical translation of viral vectors has encountered considerable obstacles, largely due to host immune responses against the virus. Here, we explored the utilization of an immunosuppressant, rapamycin, to circumvent the anti-adenovirus immunity in immunocompetent murine prostate cancer models. Rapamycin diminished adenoviral-induced acute immune response by inhibiting NF-κB activation; it also reduced the scale and delayed the onset of inflammatory cytokine secretion. Further, we found that rapamycin abrogated anti-adenovirus antibody production and retarded the function of myeloid cells and lymphocytes that were activated upon viral administration in pre-immunized hosts. Thus, the co-administration of rapamycin prolonged and enhanced adenovirus-delivered transgene expression in vivo, and thereby augmented the imaging capability of adenoviral vectors in both bioluminescent and positron emission tomography modalities. Furthermore, we showed that despite an excellent response of cancer cells to a cytotoxic gene therapeutic vector in vitro, only minimal therapeutic effects were observed in vivo in pre-immunized mice. However, when we combined gene therapy with transient immunosuppression, complete tumor growth arrest was achieved. Overall, transient immunosuppression by rapamycin was able to boost the diagnostic utility and therapeutic potentials of adenoviral vectors.

Topics: Adaptive Immunity; Adenoviridae; Animals; Cell Line, Tumor; Ganciclovir; Genetic Therapy; Genetic Vectors; Immunity, Innate; Immunization; Immunosuppression Therapy; Immunosuppressive Agents; Male; Mice; Molecular Imaging; Prostatic Neoplasms; Safety; Sirolimus; Thymidine Kinase; Transgenes

The mechanisms that regulate hematopoietic stem cell (HSC) dormancy and self-renewal are well established and are largely dependent on signals emanating from the HSC niche. Recently, we found that prostate cancer (PCa) cells target the HSC niche in mouse bone marrow (BM) during metastasis. Little is known, however, as to how the HSC niche may regulate dormancy in cancer cells. In this study, we investigated the effects of TANK binding kinase 1 (TBK1) on PCa dormancy in the BM niche. We found that binding with niche osteoblasts induces the expression of TBK1 in PCa cells PC3 and C4-2B. Interestingly, TBK1 interacts with mammalian target of rapamycin (mTOR) and inhibits its function. Rapamycin, an mTOR inhibitor, induces cell cycle arrest of PCa cells and enhances chemotherapeutic resistance of PCa cells. As a result, the knockdown of TBK1 decreases PCa stem-like cells and drug resistance in vitro and in vivo. Taken together, these results strongly indicate that TBK1 plays an important role in the dormancy and drug resistance of PCa.

Topics: AC133 Antigen; Animals; Antigens, CD; Bone Marrow; Bone Marrow Cells; Cell Cycle Checkpoints; Cell Line, Tumor; Cell Proliferation; Drug Resistance, Neoplasm; Female; Glycoproteins; Hematopoietic Stem Cells; Humans; Hyaluronan Receptors; I-kappa B Kinase; Male; Mice; Mice, SCID; Neoplasm Metastasis; Osteoblasts; Peptides; Prostatic Neoplasms; Protein Serine-Threonine Kinases; RNA Interference; RNA, Small Interfering; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

Though prostate cancer (PCa) has slow progression, the hormone refractory (HRCP) and metastatic entities are substantially lethal and lack effective treatments. Transcription factor Slug is critical in regulating metastases of various tumors including PCa. Here we studied targeted therapy against Slug using combination of 3 drugs targeting 3 pathways respectively converging via Slug and further regulating PCa metastasis. Using in vitro assays we confirmed that Slug up-regulation incurred inhibition of E-cadherin that was anti-metastatic, and inhibited Bim-regulated cell apoptosis in PCa. Upstream PTEN/Akt, mTOR, Erk, and AR/Hsp90 pathways were responsible for Slug up-regulation and each of these could be targeted by rapamycin, CI-1040, and 17-AAG respectively. In 4 PCa cell lines with different traits in terms of PTEN loss and androgen sensitivity we tested the efficacy of mono- and combined therapy with the drugs. We found that metastatic capacity of the cells was maximally inhibited only when all 3 drugs were combined, due to the crosstalk between the pathways. 17-AAG decreases Slug expression via blockade of HSP90-dependent AR stability. Combination of rapamycin and CI-1040 diminishes invasiveness more potently in PCa cells that are androgen insensitive and with PTEN loss. Slug inhibited Bim-mediated apoptosis that could be rescued by mTOR/Erk/HSP90 inhibitors. Using mouse models for circulating PCa DNA quantification, we found that combination of mTOR/Erk/HSP90 inhibitors reduced circulating PCa cells in vivo significantly more potently than combination of 2 or monotherapy. Conclusively, combination of mTOR/Erk/Hsp90 inhibits metastatic capacity of prostate cancer via Slug inhibition.

Topics: Androgens; Animals; Antibiotics, Antineoplastic; Antineoplastic Combined Chemotherapy Protocols; Benzamides; Benzoquinones; Cell Line, Tumor; HSP90 Heat-Shock Proteins; Humans; Lactams, Macrocyclic; Male; Mice; Mice, Inbred BALB C; Neoplasm Invasiveness; Prostate; Prostatic Neoplasms; Protein Kinase Inhibitors; Signal Transduction; Sirolimus; Snail Family Transcription Factors; Transcription Factors

Rapamycin is a macrocyclic lactone currently used for the treatment of cancer and for the prevention of transplant rejection. The primary pharmacological mode of action of rapamycin occurs through the inhibition (blocking) of the mammalian target of rapamycin (mTOR). By doing so, rapamycin interferes with the phosphoinositide 3-kinase (PI3K)-Akt-mTOR axis that controls several cellular functions involving cell growth, proliferation and angiogenesis. The frequent activation of the phosphoinositide 3-kinase (PI3K)/AKT pathway in advanced prostate cancer has provided a rationale for the use of mTOR inhibitors in this setting. We carried out a comparative study on the effects of rapamycin and temsirolimus on the in vitro and in vivo growth of the prostate cancer cell lines, LnCap and PC3. Our results demonstrate that rapamycin and temsirolimus exert similar in vitro and in vivo anti-proliferative effects against prostate cancer cells.

Topics: Animals; Antineoplastic Agents; Cell Line, Tumor; Cell Proliferation; Humans; Male; Mice; Neoplasm Invasiveness; Prostatic Neoplasms; Sirolimus; Xenograft Model Antitumor Assays

The mammalian target of rapamycin (mTOR) is a key regulator of cell growth and its uncontrolled activation is a hallmark of cancer. Moreover, mTOR activation has been implicated in the resistance of cancer cells to many anticancer drugs, rendering this pathway a promising pharmacotherapeutic target. Here we explored the capability of a semisynthetic compound to intercept mTOR signaling. We synthesized and chemically characterized a novel, semisynthetic triterpenoid derivative, 3-cinnamoyl-11-keto-β-boswellic acid (C-KβBA). Its pharmacodynamic effects on mTOR and several other signaling pathways were assessed in a number of prostate and breast cancer cell lines as well as in normal prostate epithelial cells. C-KβBA exhibits specific antiproliferative and proapoptotic effects in cancer cell lines in vitro as well as in PC-3 prostate cancer xenografts in vivo. Mechanistically, the compound significantly inhibits the cap-dependent transition machinery, decreases expression of eukaryotic translation initiation factor 4E and cyclin D1, and induces G(1) cell-cycle arrest. In contrast to conventional mTOR inhibitors, C-KβBA downregulates the phosphorylation of p70 ribosomal S6 kinase, the major downstream target of mTOR complex 1, without concomitant activation of mTOR complex 2/Akt and extracellular signal-regulated kinase pathways, and independently of protein phosphatase 2A, liver kinase B1/AMP-activated protein kinase/tuberous sclerosis complex, and F12-protein binding. At the molecular level, the compound binds to the FKBP12-rapamycin-binding domain of mTOR with high affinity, thereby competing with the endogenous mTOR activator phosphatidic acid. C-KβBA represents a new type of proapoptotic mTOR inhibitor that, due to its special mechanistic profile, might overcome the therapeutic drawbacks of conventional mTOR inhibitors.

Topics: Apoptosis; Breast Neoplasms; Cell Cycle Checkpoints; Cell Proliferation; Down-Regulation; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Epithelial Cells; Female; G1 Phase; Humans; Male; Phosphorylation; Prostatic Neoplasms; Protein Interaction Domains and Motifs; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Triterpenes

The aim of this study was to elucidate whether the treatment of a prostate carcinoma cell line (LNCaP) and LNCaP-derived tumors with the histone deacetylase (HDAC) inhibitor valproate in combination with the mammalian target of rapamycin (mTOR) inhibitor temsirolimus resulted in synergistic effects on cell proliferation and tumor growth. LNCaP cells were treated with valproate, temsirolimus or a combination of both. The proliferation rates and the expression of key markers of tumorigenesis were evaluated. In in vivo experiments, LNCaP cells were implanted into immune-suppressed male nude mice. Mice were treated with valproate (per os), temsirolimus (intravenously) or with a combination of both. Tumor volumes were calculated and mRNA expression was quantified. The incubation of LNCaP cells with the combination of valproate and temsirolimus resulted in a decrease of cell proliferation with an additive effect of both drugs in comparison to the single treatment. In particular, the combined application of valproate and temsirolimus led to a significant upregulation of insulin-like growth factor-binding protein-3 (IGFBP-3), which mediates apoptosis and inhibits tumor cell proliferation. In the mouse model, we found no significant differences in tumor growth between the different treatment arms but immunohistological analyses showed that tumors treated with a combination of valproate and temsirolimus, but not with the single drugs alone, exhibited a significant lower proliferation capacity.

Topics: Animals; Antineoplastic Agents; Cell Line, Tumor; Cell Proliferation; Drug Synergism; Histone Deacetylase Inhibitors; Humans; Male; Mice; Mice, Nude; Prostate; Prostatic Neoplasms; Protein Kinase Inhibitors; Sirolimus; TOR Serine-Threonine Kinases; Valproic Acid

Selective inhibitors of mammalian target of rapamycin (mTOR) kinase based upon saturated heterocycles fused to a pyrimidine core were designed and synthesized. Each series produced compounds with K(i) < 10 nM for the mTOR kinase and >500-fold selectivity over closely related PI3 kinases. This potency translated into strong pathway inhibition, as measured by phosphorylation of mTOR substrate proteins and antiproliferative activity in cell lines with a constitutively active PI3K pathway. Two compounds exhibiting suitable mouse PK were profiled in in vivo tumor models and were shown to suppress mTORC1 and mTORC2 signaling for over 12 h when dosed orally. Both compounds were additionally shown to suppress tumor growth in vivo in a PC3 prostate cancer model over a 14 day study.

Topics: Administration, Oral; Animals; Antineoplastic Agents; Biological Availability; Cell Line, Tumor; Drug Screening Assays, Antitumor; Female; Humans; Male; Mechanistic Target of Rapamycin Complex 1; Mechanistic Target of Rapamycin Complex 2; Mice; Mice, Nude; Molecular Docking Simulation; Multiprotein Complexes; Neoplasm Transplantation; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; Prostatic Neoplasms; Pyrimidines; Pyrroles; Quinazolines; Structure-Activity Relationship; TOR Serine-Threonine Kinases; Transplantation, Heterologous

Ionizing radiation (IR) is used frequently in the management of multiple tumor types, including both organ-confined and locally advanced prostate cancer (PCa). Enhancing tumor radiosensitivity could both reduce the amount of radiation required for definitive treatment and improve clinical outcome. Androgen suppression therapy improves clinical outcomes when combined with radiation therapy but is associated with significant acute and chronic toxicities; hence, there is a clear need for alternative means to increase the therapeutic window of radiotherapy. Herein, it is demonstrated that the mammalian target of rapamycin (mTOR) inhibitors rapamycin (sirolimus) and temsirolimus limit both hormone therapy (HT)-sensitive and castration-resistant PCa (CRPC) cell proliferation as single agents and have a profound radiosensitization effect when used in combination with IR. Importantly, the observed radiosensitization was influenced by the treatment schedule, in which adjuvant administration of mTOR inhibitors was most effective in limiting PCa cell population doubling. This schedule-dependent influence on in vitro treatment outcome was determined to be the result of relative effects on the cell cycle kinetics. Finally, adjuvant administration of either mTOR inhibitor tested after IR significantly decreased clonogenic cell survival of both HT-sensitive and CRPC cells compared with IR alone. Taken together, these data demonstrate that inhibition of mTOR confers a radiosensitization phenotype that is dependent on relative cell cycle kinetics and provide a foundation for clinical assessment.

Topics: Antineoplastic Agents; Cell Cycle; Cell Line, Tumor; Cell Survival; Humans; Male; Prostatic Neoplasms; Radiation-Sensitizing Agents; Receptors, Androgen; Sirolimus; TOR Serine-Threonine Kinases; X-Rays

Extensive efforts are underway to develop small-molecule inhibitors of the mammalian target of rapamycin (mTOR) kinase. It is hoped that these inhibitors will have widespread clinical impact in oncology because mTOR is a major downstream effector of PI3K signaling, one of the most frequently activated pathways in cancer. In cells, mTOR is the catalytic core subunit of two distinct complexes, mTORC1 and mTORC2, which are defined by unique mTOR-interacting proteins and have unique functions downstream of PI3K. Two classes of mTOR inhibitors are currently being evaluated as cancer therapeutics: rapamycin and its analogs, which partially inhibit mTORC1 and in some cell types mTORC2, and the recently described ATP-competitive inhibitors, which inhibit the kinase activity of both complexes. Although small molecules that selectively target mTORC2 do not yet exist, experiments using mouse genetics suggest that a theoretical mTORC2 inhibitor may have significant therapeutic value. Here, we discuss an approach to model mTOR complex specific inhibitors using mouse genetics and how it can be applied to other gene products involved in oncogenic signaling to which inhibitors do not exist.

Topics: Adenosine Triphosphate; Animals; Cell Proliferation; Disease Models, Animal; Drug Discovery; Gene Knockout Techniques; Humans; Male; Mice; Mice, Knockout; Prostatic Neoplasms; Protein Kinase Inhibitors; PTEN Phosphohydrolase; Signal Transduction; Sirolimus; Trans-Activators; Transcription Factors

Ligation of cell surface-associated GRP78 by activated α(2) -macroglobulin triggers pro-proliferative cellular responses. In part, this results from activation of adenylyl cyclase leading to an increase in cAMP. We have previously employed the cAMP analog 8-CPT-2Me-cAMP to probe these responses. Here we show in 1-LN prostate cancer cells that 8-CPT-2Me-cAMP causes a dose-dependent increase in Epac1, p-Akt(T308) , p-Akt(S473) , but not p-CREB. By contrast, the PKA activator 6-Benz-cAMP caused a dose-dependent increase in p-CREB, but not Epac1. We measured mTORC2-dependent Akt phosphorylation at S473 in immunoprecipitates of mTOR or Rictor from 1-LN cells. 8-CPT-2Me-cAMP caused a two-threefold increase in p-Akt(S473) and Akt(S473) kinase activity in Rictor immunoprecipitates. By contrast, there was only a negligible effect on p-Akt(T308) in Rictor immunoprecipitates. Silencing Rictor gene expression by RNAi significantly suppressed 8-CPT-2Me-cAMP-induced phosphorylation of Akt at Ser(473) . These studies represent the first report that Epac1 mediates mTORC2-dependent phosphorylation of Akt(S473) . Pretreatment of these cells with the PI 3-Kinase inhibitor LY294002 significantly suppressed 8-CPT-2Me-cAMP-dependent p-Akt(S473) and p-Akt(S473) kinase activities, and both effects were rapamycin insensitive. This treatment caused a two to threefold increase in S6 Kinase and 4EBP1 phosphorylation, indices of mTORC1 activation. Pretreatment of the cells with LY294002 and rapamycin significantly suppressed 8-CPT-2Me-cAMP-induced phosphorylation of S6 Kinase and 4EBP1. We further demonstrate that in 8-CPT-2Me-cAMP-treated cells, Epac1 co-immunoprecipitates with AKAP, Raptor, Rictor, PDE3B, and PDE4D suggesting thereby that during Epac1-induced activation of mTORC1 and mTORC2, Epac1 may have an additional function as a "scaffold" protein.

Topics: Adaptor Proteins, Signal Transducing; Carrier Proteins; Cell Line, Tumor; Chromones; Cyclic AMP; Cyclic AMP Response Element-Binding Protein; Cyclic Nucleotide Phosphodiesterases, Type 3; Cyclic Nucleotide Phosphodiesterases, Type 4; Endoplasmic Reticulum Chaperone BiP; Gene Silencing; Guanine Nucleotide Exchange Factors; Humans; Male; Mechanistic Target of Rapamycin Complex 1; Models, Biological; Morpholines; Multiprotein Complexes; Phosphorylation; Prostatic Neoplasms; Protein Multimerization; Proteins; Proto-Oncogene Proteins c-akt; Rapamycin-Insensitive Companion of mTOR Protein; Regulatory-Associated Protein of mTOR; Ribosomal Protein S6 Kinases; RNA-Binding Proteins; Signal Transduction; Sirolimus; Thionucleotides; TOR Serine-Threonine Kinases; Up-Regulation

Preclinical studies and clinical analyses have implicated the mammalian target of rapamycin (mTOR) pathway in the progression of prostate cancer, suggesting mTOR as a potential target for new therapies. mTOR, a serine/threonine kinase, belongs to two distinct signaling complexes: mTORC1 and mTORC2. We previously showed that the synthetic organoselenium compound, p-XSC, effectively inhibits viability and critical signaling molecules (e.g., androgen receptor, Akt) in androgen responsive (AR) and androgen independent (AI) human prostate cancer cells. On the basis of its inhibition of Akt, we hypothesized that p-XSC modulates mTORC2, an upstream regulator of the kinase. We further hypothesized that combining p-XSC with rapamycin, an mTORC1 inhibitor, would be an effective combinatory strategy for the inhibition of prostate cancer. The effects of p-XSC and rapamycin, alone or in combination, on viability and mTOR signaling were examined in AR LNCaP prostate cancer cells and AI C4-2 and DU145 cells. Phosphorylation of downstream targets of mTORC1 and mTORC2 was analyzed by immunoblotting. The interaction of mTORC1- and mTORC2-specific proteins with mTOR was probed through immunoprecipitation and immunoblotting. p-XSC inhibited phosphorylation of mTORC2 downstream targets, Akt and PCKα, and decreased the levels of rictor, an mTORC2-specific protein, coimmunoprecipitated with mTOR in C4-2 cells. The combination of p-XSC and rapamycin more effectively inhibited viability and mTOR signaling in C4-2, LNCaP and DU145 cells than either agent individually.

Topics: Antineoplastic Combined Chemotherapy Protocols; Carrier Proteins; Cell Line, Tumor; Cell Proliferation; Humans; Male; Organoselenium Compounds; Phosphorylation; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; Rapamycin-Insensitive Companion of mTOR Protein; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

Docetaxel is a first-line treatment choice in castration-resistant prostate cancer (CRPC). However, the management of CRPC remains an important challenge in oncology. There have been many reports on the effects of rapamycin, which is an inhibitor of the mammalian target of rapamycin (mTOR), in the treatment of carcinogenesis. We assessed the cytotoxic effects of the combination treatment of docetaxel and rapamycin in prostate cancer cells. Furthermore, we examined the relationship between these treatments and survivin, which is a member of the inhibitory apoptosis family.. Prostate cancer cells were cultured and treated with docetaxel and rapamycin. The effects on proliferation were evaluated with the MTS assay. In addition, we evaluated the effect on proliferation of the combination treatment induced knockdown of survivin expression by small interfering RNA transfection and docetaxel. Protein expression levels were assayed using western blotting. PC3 cells and xenograft growth in nude mice were used to evaluate the in vivo efficacy of docetaxel and its combination with rapamycin.. In vitro and in vivo, the combination of rapamycin with docetaxel resulted in a greater inhibition of proliferation than treatment with rapamycin or docetaxel alone. In addition, in vitro and in vivo, rapamycin decreased basal surviving levels, and cotreatment with docetaxel further decreased these levels. Transfection siRNA against survivin enhanced the cytotoxicity of docetaxel in PC3 cells.. The rapamycin-dependent enhancement of the cytotoxic effects of docetaxel was associated with the downregulation of survivin expression. Our results suggest that the combination of docetaxel and rapamycin is a candidate for the improved treatment of advanced prostate cancer.

Topics: Androgens; Animals; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Cell Proliferation; Docetaxel; Down-Regulation; Drug Synergism; Humans; Inhibitor of Apoptosis Proteins; Male; Mice; Mice, Inbred BALB C; Prostatic Neoplasms; Repressor Proteins; RNA, Small Interfering; Sirolimus; Survivin; Taxoids; Xenograft Model Antitumor Assays

Although hyperactivated mTOR is well recognized as being pivotal to prostate cancer growth and progression, the underlying mechanisms by which it promotes such responses remain incompletely understood. Here, we show that rapamycin activates Smads 1 and 5 in human prostate cancer cells and tissues through blocking mTORC1 kinase. Small hairpin RNA-based gene silencing and gene overexpression approaches reveal that Smads 1 and 5 mediate, whereas Smad8 represses, rapamycin-induced cell death and expression of the bone morphogenetic protein (BMP) transcriptional target Id1 in human prostate cancer cell lines. Moreover, such phospho-Smad1/5-mediated rapamycin responses were blocked by LDN-193189 (a BMPRI kinase inhibitor) or Noggin (a BMP antagonist) in LNCaP prostate cancer cells. Likewise, the mTOR kinase inhibitors Ku-0063794 and WYE-354 each enhanced phosphorylation of Smad1/5. Intriguingly, silencing raptor alone enhanced, whereas silencing rictor repressed, the phosphorylation of Smad1/5, indicating that mTORC1 represses, whereas mTORC2 activates, BMP signaling. Immunohistochemical analysis showed increased levels of phospho-Smad1/5 concomitant with suppression of phospho-S6 and survivin levels in PC3 human prostate cancer xenografts in athymic mice administered rapamycin (intraperitoneally, 5 mg/kg/d, 2-6 days). Moreover, we show that compared with prostate tumor tissue from untreated patients, levels of phospho-Smad1/5 were significantly elevated in the prostate tumor tissue of patients with high-risk prostate cancer who received 8 weeks of the rapalog everolimus as part of a neoadjuvant clinical trial before undergoing local definitive therapy by radical prostatectomy. Taken together, our data implicate Smads 1, 5 and 8 as potential prognostic markers and therapeutic targets for mTOR inhibition therapy of prostate cancer.

Topics: Animals; Blotting, Western; Bone Morphogenetic Proteins; Cell Line, Tumor; Cell Survival; Cytostatic Agents; Gene Expression Regulation, Neoplastic; Humans; Immunohistochemistry; Male; Mice; Mice, Nude; Morpholines; Phosphorylation; Prostatic Neoplasms; Pyrazoles; Pyrimidines; Reverse Transcriptase Polymerase Chain Reaction; RNA Interference; Signal Transduction; Sirolimus; Smad1 Protein; Smad5 Protein; Smad8 Protein; TOR Serine-Threonine Kinases; Xenograft Model Antitumor Assays

PI3K/AKT/mTOR pathway plays a key role in the tumorigenesis of many human cancers including prostate cancer. However, inhibitors of this pathway, such as Rad001, have not shown therapeutic efficacy as a single agent. Through a high-throughput screen of 5,000 widely used small molecules, we identified compounds that can synergize with Rad001 to inhibit prostate cancer cells. One of the compounds, propachlor, synergizes with Rad001 to induce apoptosis of castration-resistant prostate cancer cells via enhanced autophagy. This enhanced autophagic cell death is accompanied by increased Beclin1 expression as well as upregulation of Atg5-Atg12 conjugate and LC3-2. Rad001 and propachlor can also synergistically inhibit tumors in a xenograft animal model of prostate cancer. These findings provide a novel direction to develop combination therapies for advanced and metastatic prostate cancer that has failed the currently available therapies.

Topics: Acetanilides; Animals; Antineoplastic Agents; Apoptosis; Apoptosis Regulatory Proteins; Autophagy; Autophagy-Related Protein 12; Autophagy-Related Protein 5; Beclin-1; Cell Line, Tumor; Drug Synergism; Everolimus; Humans; Male; Membrane Proteins; Mice; Mice, SCID; Microtubule-Associated Proteins; Prostatic Neoplasms; Sirolimus; Small Ubiquitin-Related Modifier Proteins

To explore the effects of rapamycin on the proliferation of prostate cancer cell line 22RV1 and the activity of S6K1.. Prostate cancer 22RV1 cells cultured in vitro were treated with rapamycin at the concentrations of 0, 50, 100, 200 and 400 nmol/L. The inhibition rate of the cells'proliferation was detected by MTT, and the activity of S6K1 was determined by liquid scintillation counting.. Rapamycin significantly inhibited the proliferation of the prostate cancer 22RV1 cells and the activity of S6K1 in a dose- dependent manner, most obviously at 400 nmol/L (P<0.01).. Rapamycin can effectively suppress the proliferation of prostate cancer 22RV1 cells by regulating the expression of S6K1, the downstream protein of mammalian target of rapamycin (mTOR).

Topics: Cell Line, Tumor; Cell Proliferation; Humans; Male; Prostate; Prostatic Neoplasms; Ribosomal Protein S6 Kinases, 70-kDa; Sirolimus

Although androgen ablation therapy is the foundation of current prostate cancer treatment, most patients ultimately develop castration-resistant disease. One proposed mechanism to account for androgen receptor (AR) activity in the castrate environment is via crosstalk with other signaling pathways. Specifically, reciprocal interactions between the AKT/mTOR and AR pathways have been implicated in prostate cancer progression. Here, we used the potent inhibitor ridaforolimus to target mTOR signaling alone and in combination with AR blockade by bicalutamide to examine the effect of abrogating these signaling pathways. Ridaforolimus treatment inhibited the proliferation of all six prostate cancer cell lines examined with the greatest sensitivity associated with loss of PTEN and elevated AKT/mTOR pathway activity. Dual inhibition of the AR and mTOR signaling pathways provided further benefit with the ridaforolimus-bicalutamide combination producing synergistic antiproliferative effects in prostate cancer cells in vitro when compared with each agent alone. Pharmacodynamic analysis confirmed that combination treatment resulted in full inhibition of each of the respective pathways. Importantly, the ridaforolimus-bicalutamide combination exhibited potent antitumor activity with parallel reductions in plasma PSA levels in vivo. Taken together, ridaforolimus exhibited potent antiproliferative and antitumor activity in prostate cancer models and the addition of bicalutamide represents a potentially effective combination strategy for patient therapy.

Topics: Androgen Receptor Antagonists; Anilides; Animals; Antineoplastic Combined Chemotherapy Protocols; Cell Cycle Checkpoints; Cell Line, Tumor; Cell Proliferation; Drug Synergism; Humans; Male; Mice; Mice, Nude; Nitriles; Prostate-Specific Antigen; Prostatic Neoplasms; PTEN Phosphohydrolase; Receptors, Androgen; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Tosyl Compounds; Tumor Burden; Xenograft Model Antitumor Assays

Mst1/Stk4, a hippo-like serine-threonine kinase, is implicated in many cancers, including prostate cancer. However, the mechanisms regulating Mst1 remain obscure. Here, we characterized the effects of phospho-Thr-120 on Mst1 in prostate cancer cells. We demonstrated that phospho-Thr-120 did not alter the nuclear localization or cleavage of Mst1 in a LNCaP or castration-resistant C4-2 prostate tumor cell model, as revealed by a mutagenesis approach. Phospho-Thr-120 appeared to be specific to cancer cells and predominantly localized in the nucleus. In contrast, phospho-Thr-183, a critical regulator of Mst1 cell death, was exclusively found in the cytoplasm. As assessed by immunohistochemistry, a similar distribution of phospho-Mst1-Thr-120/Thr-183 was also observed in a prostate cancer specimen. In addition, the blockade of PI3K signaling by a small molecule inhibitor, LY294002, increased cytoplasmic phospho-Mst1-Thr-183 without having a significant effect on nuclear phospho-Mst1-Thr-120. However, the attenuation of mammalian target of rapamycin (mTOR) activity by a selective pharmacologic inhibitor, Ku0063794 or CCI-779, caused the up-regulation of nuclear phospho-Mst1-Thr-120 without affecting cytoplasmic phospho-Mst1-Thr-183. This suggests that PI3K and mTOR pathway signaling differentially regulate phospho-Mst1-Thr-120/Thr-183. Moreover, mutagenesis and RNAi data revealed that phospho-Thr-120 resulted in C4-2 cell resistance to mTOR inhibition and reduced the Mst1 suppression of cell growth and androgen receptor-driven gene expression. Collectively, these findings indicate that phospho-Thr-120 leads to the loss of Mst1 functions, supporting cancer cell growth and survival.

Topics: Animals; Blotting, Western; Cell Line, Tumor; Cell Nucleus; Chromones; HEK293 Cells; HeLa Cells; Humans; Intracellular Signaling Peptides and Proteins; Male; Mice; Mice, Nude; Morpholines; Neoplasms, Experimental; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; Prostatic Neoplasms; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins c-akt; Pyrimidines; RNA Interference; Signal Transduction; Sirolimus; Threonine; TOR Serine-Threonine Kinases; Transplantation, Heterologous; Tumor Burden

Sulforaphane (SFN) is a compound derived from cruciferous plants. Its anticancer properties have been demonstrated both, in cancer cell lines as well as tumors in animal models. It has been shown that SFN inhibits cell proliferation, induces apoptosis, autophagy, and sensitizes cancer cells to therapies. As induction of catabolic processes is often related to perturbation in protein synthesis we aimed to investigate the impact of SFN on this process in PC-3 human prostate cancer cells. In the present study we show that SFN inhibits protein synthesis in PC-3 cells in a dose- and time-dependent manner which is accompanied by a decreased phosphorylation of mTOR substrates. Translation inhibition is independent of mitochondria-derived ROS as it is observed in PC-3 derivatives devoid of functional mitochondrial respiratory chain (Rho0 cells). Although SFN affects mitochondria and slightly decreases glycolysis, the ATP level is maintained on the level characteristic for control cells. Inhibition of protein synthesis might be a protective response of prostate cancer cells to save energy. However, translation inhibition contributes to the death of PC-3 cells due to decreased level of a short-lived protein, survivin. Overexpression of this anti-apoptotic factor protects PC-3 cells against SFN cytotoxicity. Protein synthesis inhibition by SFN is not restricted to prostate cancer cells as we observed similar effect in SKBR-3 breast cancer cell line.

Topics: Antineoplastic Agents, Phytogenic; Brassicaceae; Cell Line, Tumor; Cell Survival; Energy Metabolism; Humans; Inhibitor of Apoptosis Proteins; Isothiocyanates; Male; Mitochondria; Phosphorylation; Plant Extracts; Prostatic Neoplasms; Protein Biosynthesis; Protein Processing, Post-Translational; Protein Synthesis Inhibitors; Reactive Oxygen Species; Ribosomal Protein S6 Kinases, 70-kDa; Signal Transduction; Sirolimus; Sulfoxides; Survivin; Thiocyanates; TOR Serine-Threonine Kinases

Inhibitors of the mammalian target of rapamycin (mTOR) might become a novel tool to treat advanced prostate cancer. However, chronic drug exposure may trigger resistance, limiting the utility of mTOR inhibitors.. Metastatic potential of PC3 prostate cancer cells, susceptible (PC3(par)) or resistant (PC3(res)) to the mTOR-inhibitor RAD001 was investigated. Adhesion to vascular endothelium or immobilised collagen, fibronectin and laminin was quantified. Motility, migration and invasion were explored by modified Boyden chamber assay. Integrin α and β subtypes were analysed by flow cytometry, western blotting and real-time PCR. Integrin-related signalling, EGFr, Akt, p70S6kinase and ERK1/2 activation were determined.. Adhesion was reduced, whereas motility, migration and invasion were enhanced in PC3(res). The α2 and β1 integrin subtypes were dramatically elevated, integrins α1 and α6 were lowered, whereas α5 was nearly lost in PC3(res). Activation of the Akt signalling pathway was strongly upregulated in these cells. Treating PC3(par) cells with RAD001 reduced motility, migration and invasion and deactivated Akt signalling. Blocking studies revealed that α2 and β1 integrins significantly trigger the motile behaviour of the tumour cells.. Chronic RAD001 treatment caused resistance development characterised by distinct modification of the integrin-expression profile, driving prostate cancer cells towards high motility.

Topics: Cell Adhesion; Cell Line, Tumor; Cell Movement; Everolimus; Humans; Integrin alpha2; Integrin beta1; Male; Prostatic Neoplasms; Protein Kinase Inhibitors; Sirolimus; TOR Serine-Threonine Kinases

Although the prognosis for clinically localized prostate cancer is now favorable, there are still no curative treatments for castration-resistant prostate cancer (CRPC) and, therefore, it remains fatal. In this study, we investigate a new therapeutic approach for treatment of CRPC, which involves dual targeting of a major signaling pathway that is frequently deregulated in the disease. We found that dual targeting of the Akt and mTOR signaling pathways with their respective inhibitors, MK-2206 and ridaforolimus (MK-8669), is highly effective for inhibiting CRPC in preclinical studies in vivo using a refined genetically engineered mouse model of the disease. The efficacy of the combination treatment contrasts with their limited efficacy as single agents, since delivery of MK-2206 or MK-8669 individually had a modest impact in vivo on the overall tumor phenotype. In human prostate cancer cell lines, although not in the mouse model, the synergistic actions of MK-2206 and ridaforolimus (MK-8669) are due in part to limiting the mTORC2 feedback activation of Akt. Moreover, the effects of these drugs are mediated by inhibition of cellular proliferation via the retinoblastoma (Rb) pathway. Our findings suggest that dual targeting of the Akt and mTOR signaling pathways using MK-2206 and ridaforolimus (MK-8669) may be effective for treatment of CRPC, particularly for patients with deregulated Rb pathway activity.

Topics: Animals; Antineoplastic Agents; Cell Line, Tumor; Cluster Analysis; Disease Models, Animal; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Heterocyclic Compounds, 3-Ring; Humans; Male; Mice; Mice, Transgenic; Orchiectomy; Phenotype; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; Retinoblastoma Protein; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Tumor Burden; Xenograft Model Antitumor Assays

Isoprenoids are recognized for their ability to suppress carcinogenic processes in vivo and in vitro. We previously established that the isoprenoid, perillyl alcohol, acted mechanistically on translation of specific proteins through modulation of mechanistic target of rapamycin (mTOR) signaling. Telomerase-the enzyme responsible for immortalizing cells through the addition of telomeric repeats-is de-repressed early in an aspiring cancer cell. Here the effects of biologically-relevant concentrations and short incubations (1-16 h) of perillyl alcohol or the mTOR inhibitor, rapamycin, on telomerase activity were examined in prostate cancer cell lines. A rapid suppression of telomerase activity was observed (from ∼65% to >95%) determined by real-time quantitative telomerase repeat amplification protocol and confirmed by polyacrylamide gel-analysis. Using real-time reverse transcriptase-PCR, we demonstrated that human telomerase reverse transcriptase (hTERT) mRNA levels were unaltered. Western blot analysis revealed that hTERT protein levels decreased in response to perillyl alcohol or rapamycin. This decrease was partially blocked by pretreatment with a proteasome inhibitor MG-132, indicating that proteasomal degradation contributed to the loss of hTERT protein. No change in hTERT phosphorylation at Ser824 was observed, indicating the absence of cellular hTERT protein redistribution. These findings provide evidence for a unique link between nutrient- and macrolide-mediated regulation of mTOR and hTERT, a key enzyme that regulates DNA structure and stability.

Topics: Blotting, Western; Cell Line, Tumor; Cysteine Proteinase Inhibitors; Enzyme Inhibitors; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Neoplastic; Humans; Leupeptins; Male; Monoterpenes; Prostatic Neoplasms; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sirolimus; Telomerase; TOR Serine-Threonine Kinases

Androgen receptor has a critical role in prostate cancer development and progression. Cell death via autophagy may also contribute to prostate cancer progression. We determined the role and regulatory effects of androgen receptor on the autophagy process of prostate cancer cells.. Using a series of morphological approaches, such as transmission electron microscopy, monodansylcadaverine (Sigma®) and GFP-LC3 fluorescence microscopy assay, and Western blot we monitored the autophagic process in 3 pairs of prostate cancer cell lines to study the relationship to androgen receptor signals.. Androgen receptor knockdown in androgen receptor positive cells, such as LNCaP or CWRrv1 human prostate cancer cells, led to increased autophagy. Adding functional androgen receptor to androgen receptor negative cells, such as PC3 human prostate cancer cells, resulted in decreased autophagy. This suggests that androgen receptor could have a negative role in regulating autophagy. Mechanism dissection indicated that androgen receptor might repress autophagy via modulation of p62 expression. A therapeutic approach of targeting androgen receptor to increase autophagy using the androgen receptor degradation enhancer ASC-J9® suppressed prostate cancer growth.. Findings provide evidence that the androgen receptor might promote prostate cancer cell growth via autophagy down-regulation. Targeting the androgen receptor via ASC-J9 might lead to tumor suppression via the induction of autophagy. This may represent a new, potential therapeutic approach and mechanism for prostate cancer.

Topics: Antibiotics, Antineoplastic; Autophagy; Humans; Male; Prostatic Neoplasms; Receptors, Androgen; Sirolimus; Tumor Cells, Cultured

TNF-alpha levels in prostate cancer correlate with the extent of disease and are significantly elevated in the metastatic stage. TNF receptor superfamily controls two distinct signalling cascades, leading to opposite effects, i.e. apoptosis and survival; in prostate cancer TNF-alpha-mediated signalling induces cell survival and resistance to therapy. The apoptosis of prostate epithelial cancer cells LNCaP and PC3 was investigated upon treatment with the autophagy inhibitor 3-methyladenine and the autophagy inducer rapamycin, in combination with TNF-alpha. Cells were exposed to these molecules for 18, 24 and 48 h. Autophagy was assessed via LC3 Western blot analysis; propidium iodide and TUNEL stainings followed by flow cytometry or caspase-8 and caspase-3 activation assays were performed to evaluate apoptosis. TNF-alpha-induced apoptosis was potentiated by 3-methyladenine in the androgen-responsive LNCaP cells, whereas no effect was observed in the androgen-insensitive PC3 cells. Interestingly such pro-apoptosis effect in LNCaP cells was associated with reduced c-Flip levels through proteasomal degradation via increased reactive oxygen species production and p38 activation; such c-Flip reduction was reversed in the presence of either the proteasome inhibitor MG132 or the reactive oxygen species scavenger N-acetyl-cysteine. Conversely in PC3 but not in LNCaP cells, rapamycin stimulated TNF-alpha-dependent apoptosis; such effect was associated with reduced c-Flip promoter activity and FoxO3a activation. We conclude that TNF-alpha-induced apoptosis may be potentiated, in prostate cancer epithelial cells, through autophagy modulators. Increased sensitivity to TNF-alpha-dependent apoptosis correlates with reduced c-Flip levels which are consequent to a post-transcriptional and a transcriptional mechanism in LNCaP and PC3 cells respectively.

Topics: Adenine; Apoptosis; Autophagy; Blotting, Western; CASP8 and FADD-Like Apoptosis Regulating Protein; Cell Line, Tumor; Drug Screening Assays, Antitumor; Enzyme Activation; Epithelial Cells; Forkhead Box Protein O3; Forkhead Transcription Factors; Humans; Male; Microtubule-Associated Proteins; p38 Mitogen-Activated Protein Kinases; Promoter Regions, Genetic; Prostatic Neoplasms; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Proteolysis; Proto-Oncogene Proteins c-akt; Reactive Oxygen Species; Sirolimus; Transcription, Genetic; Tumor Necrosis Factor-alpha

Molecular targets in prostate cancer are continually being explored, for which there are currently few therapeutic options. Rapamycin (RPM) is an antifungal macrolide antibiotic isolated from Streptomyces hygroscopicus which can inhibit the G1 to S transition. URGCP (upregulator of cell proliferation) is a novel gene located on chromosome 7p13. We aimed to investigate the role of URGCP gene expression changes in PC3, DU145, and LNCAP cell lines with/out RPM. Average cell viability and cytotoxic effect of rapamycin were investigated at 24 h intervals for three days by using Trypan blue dye exclusion test and XTT assay. Cytotoxic effects of rapamycin in DU145, PC3 and LNCAP cells were detected in time and dose dependent manner with the IC(50) doses within the range of 1-100 nM. As the results were evaluated, IC(50) doses in the DU145, PC3, and LNCaP cells were detected as 10, 25, and 50 nM, respectively. The mean relative ratios of URGCP gene expression in DU145, LNCAP and PC3 cells were found as -1.48, 6.59 and -13.00, respectively, when compared to rapamycin-free cells. The False Discovery Rate adjusted p value in DU145, LNCAP and PC3 were 1.25 × 10(-5), 2.20 × 10(-8) and 6.20 × 10(-9), respectively. When the URGCP gene expression level is compared between the dose and control group, we found that URGCP gene expression was significantly decreased in dose groups of DU145 and PC3 cells.

Topics: Antibiotics, Antineoplastic; Cell Line, Tumor; Cell Survival; Gene Expression; Gene Expression Regulation, Neoplastic; Humans; Inhibitory Concentration 50; Male; Neoplasm Proteins; Prostatic Neoplasms; Sirolimus

The impact of the mTOR inhibitor RAD001 combined with the EGFr/VEGFr tyrosine kinase inhibitor AEE788 on prostate tumor cell growth, adhesion and migration was analyzed in vitro. The RAD001-AEE788 combination profoundly reduced tumor-endothelium and tumor-matrix contacts, suppressing cell growth and cell cycle progression. The underlying molecular mode of action depended on the cell phenotype, since cell cycle proteins, integrin subtype expression and integrin dependent signaling were altered in a different manner in PC-3 and DU-145 versus LNCaP prostate cancer cells. Simultaneous targeting of mTOR and VEGFr/EGFr related pathways may offer a novel therapeutic strategy for prostate cancer treatment.

Topics: Cell Adhesion; Cell Cycle; Cell Line, Tumor; Cell Movement; Cell Proliferation; ErbB Receptors; Everolimus; Humans; Male; Neoplasm Invasiveness; Prostatic Neoplasms; Protein Kinase Inhibitors; Purines; Receptors, Vascular Endothelial Growth Factor; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

To analyze the combined impact of the histone deacetylase (HDAC) inhibitor valproic acid (VPA) and the mammalian target of rapamycin (mTOR) inhibitor RAD001 on prostate cancer cell growth.. PC-3, DU-145 and LNCaP cells were treated with RAD001, VPA or with an RAD001-VPA combination for 3 or 5 days. Tumor cell growth, cell cycle progression and cell cycle regulating proteins were then investigated by MTT assay, flow cytometry and Western blotting, respectively. Effects of drug treatment on cell signaling pathways were determined.. Separate application of RAD001 or VPA distinctly reduced tumor cell growth and impaired cell cycle progression. Significant additive effects were evoked when both drugs were used in concert. Particularly, the cell cycle regulating proteins cdk1, cdk2, cdk4 and cyclin B were reduced, whereas p21 and p27 were enhanced by the RAD001-VPA combination. Signaling analysis revealed deactivation of EGFr, ERK1/2 and p70S6k. Phosphorylation of Akt was diminished in DU-145 but elevated in PC-3 and LNCaP cells.. The RAD001-VPA combination exerted profound antitumor properties on a panel of prostate cancer cell lines. Therefore, simultaneous blockage of HDAC and mTOR related pathways should be considered when designing novel therapeutic strategies for treating prostate carcinoma.

Topics: Adenocarcinoma; Antineoplastic Agents; Blotting, Western; Cell Cycle; Cell Cycle Proteins; Cell Movement; Cell Survival; Drug Screening Assays, Antitumor; Drug Therapy, Combination; ErbB Receptors; Everolimus; Flow Cytometry; Histone Deacetylase Inhibitors; Humans; Male; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Phosphorylation; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; Ribosomal Protein S6 Kinases, 70-kDa; Sirolimus; TOR Serine-Threonine Kinases; Tumor Cells, Cultured; Valproic Acid

The concept of molecular tumor targeting might provide new hope in the treatment of advanced prostate cancer. We evaluated metastasis blocking properties of the histone deacetylase (HDAC) inhibitor valproic acid (VPA) and the mammalian target of rapamycin (mTOR) inhibitor RAD001 on prostate cancer cell lines. RAD001 or VPA were applied to PC-3 or LNCaP cells, either separately or in combination. Adhesion to vascular endothelium or to immobilized collagen, fibronectin or laminin was quantified. Migration and invasion were explored by a modified Boyden chamber assay. Integrin α and β subtypes were analyzed by flow cytometry, western blotting and RT-PCR. Effects of drug treatment on integrin related signaling, Akt and p70S6kinase activation, histone H3 and H4 acetylation were also determined. Separate application of RAD001 or VPA distinctly reduced tumor cell adhesion, migration and invasion, accompanied by elevated Akt activation and p70S6kinase de-activation. Integrin subtype expression was altered significantly by both compounds (VPA > RAD001). When both drugs were used in concert additive effects were observed on the migratory and invasive behavior but not on tumor-endothelium and tumor-matrix interaction. Separate mTOR or HDAC inhibition slows processes related to tumor metastasis. The RAD001-VPA combination showed advantage over VPA monotreatment with particular respect to migration and invasion. Ongoing studies are required to assess the relevance of VPA monotherapy versus VPA-RAD001 combination on tumor cell motility.

Topics: Cell Adhesion; Cell Movement; Drug Therapy, Combination; Enzyme Inhibitors; Everolimus; Histone Deacetylases; Humans; Male; Neoplasm Invasiveness; Prostatic Neoplasms; Sirolimus; Structure-Activity Relationship; TOR Serine-Threonine Kinases; Tumor Cells, Cultured; Valproic Acid

The cell-cycle G(2)-M phase gene UBE2C is overexpressed in various solid tumors including castration-resistant prostate cancer (CRPC). Our recent studies found UBE2C to be a CRPC-specific androgen receptor (AR) target gene that is necessary for CRPC growth, providing a potential novel target for therapeutic intervention. In this study, we showed that the G(1)-S cell-cycle inhibitor-779 (CCI-779), an mTOR inhibitor, inhibited UBE2C mRNA and protein expression in AR-positive CRPC cell models abl and C4-2B. Treatment with CCI-779 significantly decreased abl cell proliferation in vitro and in vivo through inhibition of cell-cycle progression of both G(2)-M and G(1)-S phases. In addition, exposure of abl and C4-2B cells to CCI-779 also decreased UBE2C-dependent cell invasion. The molecular mechanisms for CCI-779 inhibition of UBE2C gene expression involved a decreased binding of AR coactivators SRC1, SRC3, p300, and MED1 to the UBE2C enhancers, leading to a reduction in RNA polymerase II loading to the UBE2C promoter, and attenuation of UBE2C mRNA stability. Our data suggest that, in addition to its ability to block cell-cycle G(1) to S-phase transition, CCI-779 causes a cell-cycle G(2)-M accumulation and an inhibition of cell invasion through a novel UBE2C-dependent mechanism, which contributes to antitumor activities of CCI-779 in UBE2C overexpressed AR-positive CRPC.

Topics: Animals; Antineoplastic Agents; Cell Division; Cell Growth Processes; Cell Line, Tumor; Cyclin D1; Down-Regulation; Enzyme Inhibitors; G2 Phase; Humans; Male; Mice; Mice, Inbred BALB C; Orchiectomy; Prostatic Neoplasms; RNA, Messenger; Sirolimus; Transcription, Genetic; Transfection; Ubiquitin-Conjugating Enzymes; Xenograft Model Antitumor Assays

Single drug use has not achieved satisfactory results in the treatment of prostate cancer, despite application of increasingly widespread targeted therapeutics. In the present study, the combined impact of the mammalian target of rapamycin (mTOR)-inhibitor RAD001, the dual EGFr and VGEFr tyrosine kinase inhibitor AEE788 and the histone deacetylase (HDAC)-inhibitor valproic acid (VPA) on prostate cancer growth and adhesion in vitro was investigated.. PC-3, DU-145 and LNCaP cells were treated with RAD001, AEE788 or VPA or with a RAD-AEE-VPA combination. Tumor cell growth, cell cycle progression and cell cycle regulating proteins were then investigated by MTT-assay, flow cytometry and western blotting, respectively. Furthermore, tumor cell adhesion to vascular endothelium or to immobilized extracellular matrix proteins as well as migratory properties of the cells was evaluated, and integrin α and β subtypes were analyzed. Finally, effects of drug treatment on cell signaling pathways were determined.. All drugs, separately applied, reduced tumor cell adhesion, migration and growth. A much stronger anti-cancer effect was evoked by the triple drug combination. Particularly, cdk1, 2 and 4 and cyclin B were reduced, whereas p27 was elevated. In addition, simultaneous application of RAD001, AEE788 and VPA altered the membranous, cytoplasmic and gene expression pattern of various integrin α and β subtypes, reduced integrin-linked kinase (ILK) and deactivated focal adhesion kinase (FAK). Signaling analysis revealed that EGFr and the downstream target Akt, as well as p70S6k was distinctly modified in the presence of the drug combination.. Simultaneous targeting of several key proteins in prostate cancer cells provides an advantage over targeting a single pathway. Since strong anti-tumor properties became evident with respect to cell growth and adhesion dynamics, the triple drug combination might provide progress in the treatment of advanced prostate cancer.

Topics: Antineoplastic Combined Chemotherapy Protocols; Cell Adhesion; Cell Cycle; Cell Growth Processes; Cell Line, Tumor; Cell Movement; Cyclin-Dependent Kinases; Cyclins; Down-Regulation; Everolimus; Human Umbilical Vein Endothelial Cells; Humans; Integrins; Male; Molecular Targeted Therapy; Prostatic Neoplasms; Purines; Signal Transduction; Sirolimus; Valproic Acid

The growth potential of PC3 prostate cancer cells, sensible (PC3(par)) or resistant (PC3(res)) to the mTOR inhibitor everolimus (RAD001) was investigated. Cell growth and proliferation of PC3(res) was similar to that of PC3(par), and late apoptosis increased in PC3(par) but decreased in PC3(res) following treatment with low dosed everolimus. PC3(res) accumulated in the G2/M-phase, accompanied by cdk1, cdk2 and cyclin B elevation. Knocking down cdk1 or cyclin B distinctly blocked the growth activity of PC3(res). One reason for everolimus resistance may be up-regulation of the cdk1-cyclin B complex in prostate cancer cells, leading to enhanced progression towards G2/M.

Topics: Blotting, Western; CDC2 Protein Kinase; Cell Cycle; Cell Division; Cell Line, Tumor; Cell Proliferation; Cell Survival; Cyclin B; Dose-Response Relationship, Drug; Drug Resistance, Neoplasm; Everolimus; G2 Phase; Humans; Immunosuppressive Agents; Inhibitory Concentration 50; Male; Multiprotein Complexes; Prostatic Neoplasms; RNA Interference; Sirolimus

Specific inhibitors towards Histone Deacetylases (HDACs) and Mammalian Target of Rapamycin Complex 1 (mTORC1) have been developed and demonstrate potential as treatments for patients with advanced and/or metastatic and castrate resistant prostate cancer (PCa). Further, deregulation of HDAC expression and mTORC1 activity are documented in PCa and provide rational targets to create new therapeutic strategies to treat PCa. Here we report the use of the c-Myc adenocarcinoma cell line from the c-Myc transgenic mouse with prostate cancer to evaluate the in vitro and in vivo anti-tumor activity of the combination of the HDAC inhibitor panobinostat with the mTORC1 inhibitor everolimus. Panobinostat/everolimus combination treatment resulted in significantly greater antitumor activity in mice bearing androgen sensitive Myc-CaP and castrate resistant Myc-CaP tumors compared to single treatments. We identified that panobinostat/everolimus combination resulted in enhanced anti-tumor activity mediated by decreased tumor growth concurrent with augmentation of p21 and p27 expression and the attenuation of angiogenesis and tumor proliferation via androgen receptor, c-Myc and HIF-1α signaling. Also, we observed altered expression of microRNAs associated with these three transcription factors. Overall, our results demonstrate that low dose concurrent panobinostat/everolimus combination therapy is well tolerated and results in greater anti-tumor activity compared to single treatments in tumor bearing immuno-competent mice. Finally, our results suggest that response of selected miRs could be utilized to monitor panobinostat/everolimus in vivo activity.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Cell Line, Tumor; Cell Proliferation; Drug Synergism; Everolimus; Genes, myc; Histone Deacetylase Inhibitors; Hydroxamic Acids; Hypoxia; Indoles; Male; Mice; Mice, Transgenic; MicroRNAs; Panobinostat; Prostatic Neoplasms; Receptors, Androgen; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Treatment Outcome

Antisense oligonucleotides (oligos) have demonstrated their efficacy in inhibiting the growth of prostate and breast tumor cells. Previous studies employed first generation, phosphorothioated, cDNA oligos synthesized complimentary to mRNA encoding transforming growth factor-alpha (TGF-alpha), epidermal growth factor receptor (EGFR), the anti-apoptosis protein bcl-2, and the androgen receptor (AR). In an effort to construct oligos with greater than one mRNA binding site, bi-specifics have been developed which target combinations of the above proteins, and these have been shown at least as effective as the mono-specific oligos from which their sequences were derived. While all bi-specifics have inhibitory effects, which can be enhanced by the combined administration of an additional chemotherapeutic agent, those bi-specifics which target bcl-2 and EGFR were reported to be the most effective. The experiments presented here are an effort to evaluate a new group of bi-specifics whose targets include the chaperone protein clusterin, whose expression is up regulated in many tumors and activity is known to inhibit apoptosis. Of particular interest were those bi-specifics constructed to target both clusterin and bcl-2 (also an apoptosis inhibitory protein). Cell lines targeted included both prostate LNCaP and PC-3, as well as the breast derived MCF-7. In order to identify agents which enhance oligo activity, but contribute less toxicity, oligos were tested both alone and in combination with either the immune inhibitor Rapamycin, or the chemotherapeutic (and more toxic) Taxol. Results indicate that bi-specifics targeting clusterin are statistically effective, and are similarly enhanced by Rapamycin, or Taxol. When bi-specifics including clusterin as a target, were tested against LNCaP and MCF-7 cells, the level of activity was intermediate between that of the mono-specific compounds tested separately. In experiments which compared both, bi-specifics which included a target for clusterin had inhibitory activity similar to the previously described bi-specifics directed towards bcl-2 and EGFR.

Topics: Adenocarcinoma; Antineoplastic Agents; Apoptosis; Breast Neoplasms; Cell Line, Tumor; Clusterin; Drug Delivery Systems; Drug Screening Assays, Antitumor; Female; Humans; Male; Neoplasm Proteins; Oligonucleotides, Antisense; Paclitaxel; Phosphorothioate Oligonucleotides; Prostatic Neoplasms; Proto-Oncogene Proteins c-bcl-2; RNA, Messenger; RNA, Neoplasm; Sirolimus; Substrate Specificity

Cancer cells have evolved exquisitely to ignore both intrinsic and extrinsic cell death signals, and resistance to cell death is a critical challenge facing clinical oncology. Autophagy, the catabolic recycling process that involves the fusion of autophagosomes containing sequestered cargo with lysosomes, has an enigmatic role in tumorigenesis. In times of metabolic stress due to deprived nutrition or hypoxia, tumor cells use autophagy as a scavenging mechanism for maintenance of critical processes and survival. However, modulation of the extent of autophagy plays a critical role, as excessive autophagy can result in a nonapoptotic and non-necrotic cell death (sometimes referred to as Type II programmed cell death). It is likely that the genetic context of specific cancers will have an impact upon whether autophagy is primarily a mechanism for survival or cell death.

Topics: Adaptor Proteins, Signal Transducing; Antibiotics, Antineoplastic; Autophagy; Cell Cycle Proteins; Cell Line; Humans; Male; Phosphoproteins; Prostatic Neoplasms; Proto-Oncogene Proteins c-myc; Sirolimus

Docetaxel (DOC) therapy is well tolerated and shows high response rates in patients with hormone refractory prostate cancer (HRPC). There are many reports on the effect of rapamycin (RPM) on the treatment of carcinogenesis. The goal of this study was to test whether RPM could enhance the susceptibility of both androgen-dependent and -independent prostate carcinoma cells to DOC.. Prostate cancer (PC) cell lines (LNCap, PC3 and AILNCap) were cultured and treated with RPM and DOC alone or in combination. The effects of therapeutic agents on cells were determined by the WST-1 assay. Apoptosis induction was confirmed by flow cytometric analysis. The apopcyto caspase colorimetric assay kit was applied to measure the activities of caspases 3 and 9. The antitumor effects of RPM and DOC against PC cells were also assessed in nude mice using four randomized groups: control, RPM, DOC and combination drug therapy by measuring tumor size. All the animals tolerated both RPM and DOC without significant weight loss.. RPM and DOC caused dosage-dependent growth suppression of PC cells. RPM could increase the susceptibility of PC cells to DOC significantly, and combined treatment with RPM and DOC caused synergistic growth suppression in all examined PC cell lines by isobolographic analysis. Both RPM and DOC significantly induced apoptosis in a dosage-dependent manner. RPM (10 nmol/L), DOC (1 nmol/L), and combined treatment induced apoptosis rate were 8%, 17% and 38%, respectively (the control was 2%). RPM could promote the apoptosis induced by DOC in PC cell lines. Both RPM and DOC significantly increased the caspase activity in a dosage-dependent manner. The relative activities of caspase 9 in control, RPM, DOC and RPM + DOC groups were 0.22 +/- 0.02, 0.36 +/- 0.06, 0.47 +/- 0.05 and 0.84 +/- 0.08, respectively. The relative activities of caspase 3 were 0.21 +/- 0.02, 0.24 +/- 0.05, 0.42 +/- 0.06 and 0.81 +/- 0.09, respectively. Either RPM or DOC alone significantly inhibited the growth of PC cells in nude mice compared to the control. The combination of RPM and DOC produced a significant reduction in tumor volume when compared to RPM or DOC alone. After 5-week treatment, the tumor sizes of LNCap in control, RPM, DOC and RPM + DOC groups were (570 +/- 56) mm(3), (412 +/- 41) mm(3), (425 +/- 46) mm(3) and (221 +/- 26) mm(3), respectively.. RPM could significantly increase the susceptibility of both androgen-dependent and -independent PC cells to DOC; the synergy of RPM and DOC was demonstrated. RPM enhanced the DOC-induced upregulation of caspase activity, resulting in an increasing number of cells in sub-G1 phases. The synergy of the combined treatment might be observed in both androgen-dependent and -independent PC cell lines.

Topics: Animals; Antineoplastic Agents; Cell Line, Tumor; Docetaxel; Drug Synergism; Flow Cytometry; Humans; Male; Mice; Mice, Nude; Prostatic Neoplasms; Random Allocation; Sirolimus; Taxoids; Xenograft Model Antitumor Assays

Membrane type 1 (MT1)-matrix metalloproteinase (MT1-MMP) is a membrane-tethered MMP that has been shown to play a key role in promoting cancer cell invasion. MT1-MMP is highly expressed in bone metastasis of prostate cancer (PC) patients and promotes intraosseous tumor growth of PC cells in mice. The majority of metastatic prostate cancers harbor loss-of-function mutations or deletions of the tumor suppressor PTEN (phosphatase and tensin homologue deleted on chromosome ten). However, the role of PTEN inactivation in MT1-MMP expression in PC cells has not been examined. In this study, prostate epithelial cell lines derived from mice that are either heterozygous (PTEN(+/-)) or homozygous (PTEN(-/-)) for PTEN deletion or harboring a wild-type PTEN (PTEN(+/+)) were used to investigate the expression of MT1-MMP. We found that biallelic loss of PTEN is associated with posttranslational regulation of MT1-MMP protein in mouse PC cells. PTEN(-/-) PC cells display higher levels of MT1-MMP at the cell surface when compared to PTEN(+/+) and PTEN(+/-) cells and consequently exhibited enhanced migratory and collagen-invasive activities. MT1-MMP displayed by PTEN(-/-) cells is differentially O-glycosylated and exhibits a slow rate of turnover. MT1-MMP expression in PTEN(-/-) cells is under control of the PI3K/AKT signaling pathway, as determined using pharmacological inhibitors. Interestingly, rapamycin, an mTOR inhibitor, upregulates MT1-MMP expression in PTEN(+/+) cells via PI3K activity. Collectively, these data in a mouse prostate cell system uncover for the first time a novel and complex relationship between PTEN loss-mediated PI3K/AKT activation and posttranslational regulation of MT1-MMP, which may play a role in PC progression.

Topics: Animals; Cell Line, Tumor; Cell Membrane; Cell Movement; Enzyme Activation; Enzyme Precursors; Epithelial Cells; Gelatinases; Gene Expression Profiling; Genotype; Glycosylation; Humans; Immunoblotting; Male; Matrix Metalloproteinase 14; Mice; Mice, Knockout; Phosphatidylinositol 3-Kinases; Prostatic Neoplasms; Protein Processing, Post-Translational; Proto-Oncogene Proteins c-akt; PTEN Phosphohydrolase; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction; Sirolimus

To determine the mechanisms associated with loss of androgen dependency and disease progression in prostate cancer (PCa), we investigated the relationship between the androgen receptor (AR) and mTOR pathways and the impact of inhibiting both pathways in androgen-dependent and castration-resistant PCa models.. Androgen-dependent (LNCaP) and castration-resistant PCa (HP-LNCaP) cells were grown as tumours in SCID mice. Once tumours reached 500 mm(3), animals were grouped and injected subcutaneous with vehicle, our novel anti-androgen/androgen synthesis inhibitor, VN/124-1, bicalutamide, and everolimus. Tumour volumes were measured biweekly. The PSA and protein analyses were performed after completion of the treatment.. The addition of everolimus to bicalutamide treatment of resistant tumours significantly reduced tumour growth rates and tumour volumes. Anti-androgen treatment also increased protein expression of multiple signal transduction pathways earlier than vehicle-treated control xenografts. VN/124-1 plus everolimus acted in concert to reduce tumour growth rates in our castration-resistant xenograft model.. This study suggests that dual inhibition of AR and mTOR in castration-resistant xenograft models can restore sensitivity of tumours to anti-androgen therapy. Furthermore, after bicalutamide failure, dual inhibition with VN/124-1 and everolimus was the most effective treatment.

Topics: Androgen Antagonists; Androgen Receptor Antagonists; Androstadienes; Anilides; Animals; Benzimidazoles; Castration; Cell Line, Tumor; Disease Progression; Drug Therapy, Combination; Everolimus; Intracellular Signaling Peptides and Proteins; Male; Mice; Mice, SCID; Neoplasms, Hormone-Dependent; Nitriles; Prostate-Specific Antigen; Prostatic Neoplasms; Protein Serine-Threonine Kinases; Receptor Cross-Talk; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Tosyl Compounds; Xenograft Model Antitumor Assays

Signaling between androgen receptor (AR) and mTOR may be crucial for prostate cancer cells to endure the low androgen and suboptimal nutrient conditions produced by androgen deprivation therapy.. AR and mTOR cross-talk was examined in LNCaP cells exposed to either high or low testosterone. AR and mTOR activities were modified separately using either siRNA knockdown or specific chemical inhibitor. The biological significance of the reciprocal communication was assessed by susceptibility to glucose deprivation-induced cell death.. AR positively regulated mTOR activity in both low and high testosterone levels. TSC1 and TSC2, the two negative regulators of mTOR, may be involved since both were up-regulated by AR knockdown. Sub-baseline mTOR increased AR protein levels. However, this effect only occurred with low testosterone. More cells underwent apoptosis if AR function was inhibited during glucose deprivation, which significantly depressed mTOR activity.. The compensatory increase of AR function due to a repressed mTOR signal is advantageous for survival. Disrupting this loop at the time of initiation of androgen deprivation therapy may delay, or even prevent, the recurrence of prostate cancer.

Topics: Androgen Antagonists; Anilides; Apoptosis; Cell Line, Tumor; Cell Survival; Down-Regulation; Gene Knockdown Techniques; Glucose; Humans; Male; Nitriles; Prostatic Neoplasms; Receptor Cross-Talk; Receptors, Androgen; RNA, Small Interfering; Sirolimus; Testosterone; TOR Serine-Threonine Kinases; Tosyl Compounds; Tuberous Sclerosis Complex 1 Protein; Tuberous Sclerosis Complex 2 Protein; Tumor Suppressor Proteins

Previous studies have demonstrated that monospecific antisense oligonucleotides (oligos) directed against mRNA encoding proteins associated with tumor growth, death, and survival are efficacious against breast and prostate tumors. Targeted proteins, associated with different signal transduction pathways, have included transforming growth factor-alpha [TGF-alpha (MR(1))], its binding site the epidermal growth factor receptor [EGFR (MR(2))] sharing sequence homology to the breast cancer prognostic marker Her-2/neu, an apoptosis inhibiting protein [bcl-2 (MR(4))], and the androgen receptor [AR (MR(5))]. In attempts to enhance antisense therapy, recent reports describe how two of the binding sites mentioned above can be sequentially placed within a single complementary (bispecific) strand and administered either in the presence or absence of additional therapeutic agents. When tested against breast and prostate tumor cell lines specific differences were noted: MCF-7 breast cancer cells were more receptive to the inhibitory effects of monospecific oligos, whereas PC-3 and LNCaP prostate cells were particularly responsive to bispecifics. In an effort to identify agents which enhance the activity of oligos and which possess less toxicity than traditionally employed chemotherapeutics, Rapamycin, an immunosuppressive agent known to regulate tumor growth and signal transduction mediated by the mTOR receptor, is compared to paclitaxel in combination therapy employing monospecific or bispecific oligos. Bispecifics were constructed recognizing the binding sites for TGF-alpha and EGFR mRNA [TGF-alpha/EGFR (MR(12)) and EGFR/TGF-alpha (MR(21))]; another pair recognized binding sites for EGFR and bcl-2 [EGFR/bcl-2 (MR(24)) and bcl-2/EGFR (MR(42))]; while a third pair employed only against the LNCaP prostate cell line recognized bcl-2 and the androgen receptor [bcl-2/AR (MR4(45)) and AR/bcl-2 (MR(54))]. Oligo pairs differ in their 5'-3' linear binding site orientations, and were tested in vitro against MCF-7 breast and PC-3 and LNCaP prostate tumor cell lines. Following cell attachment, incubations were done for 2 days with the agents followed by 2 days in their absence. Five experiments evaluated the effect of monospecific or bispecific antisense oligos in combination with an LD(50) dosage of either Rapamycin or paclitaxel and led to the conclusion that although these agents act via different mechanisms, they are comparable in effectiveness.

Topics: Androgen Receptor Antagonists; Antibiotics, Antineoplastic; Antineoplastic Agents, Phytogenic; Apoptosis Regulatory Proteins; Breast Neoplasms; Cell Line, Tumor; Combined Modality Therapy; ErbB Receptors; Female; Gene Targeting; Humans; Male; Oligonucleotides, Antisense; Paclitaxel; Prostatic Neoplasms; Receptors, Androgen; Signal Transduction; Sirolimus; Transforming Growth Factor alpha

Because the mammalian target of rapamycin (mTOR) pathway is commonly deregulated in human cancer, mTOR inhibitors, rapamycin and its derivatives, are being actively tested in cancer clinical trials. Clinical updates indicate that the anticancer effect of these drugs is limited, perhaps due to rapamycin-dependent induction of oncogenic cascades by an as yet unclear mechanism. As such, we investigated rapamycin-dependent phosphoproteomics and discovered that 250 phosphosites in 161 cellular proteins were sensitive to rapamycin. Among these, rapamycin regulated four kinases and four phosphatases. A siRNA-dependent screen of these proteins showed that AKT induction by rapamycin was attenuated by depleting cellular CDC25B phosphatase. Rapamycin induces the phosphorylation of CDC25B at Serine375, and mutating this site to Alanine substantially reduced CDC25B phosphatase activity. Additionally, expression of CDC25B (S375A) inhibited the AKT activation by rapamycin, indicating that phosphorylation of CDC25B is critical for CDC25B activity and its ability to transduce rapamycin-induced oncogenic AKT activity. Importantly, we also found that CDC25B depletion in various cancer cell lines enhanced the anticancer effect of rapamycin. Together, using rapamycin phosphoproteomics, we not only advance the global mechanistic understanding of the action of rapamycin but also show that CDC25B may serve as a drug target for improving mTOR-targeted cancer therapies.

Topics: Antibiotics, Antineoplastic; Breast Neoplasms; cdc25 Phosphatases; Cell Line, Tumor; Enzyme Activation; HeLa Cells; Humans; Male; Phosphorylation; Prostatic Neoplasms; Protein Kinases; Proteomics; Proto-Oncogene Proteins c-akt; Sirolimus; TOR Serine-Threonine Kinases

mTOR pathway inhibitors, specifically rapamycin and its derivatives, are promising therapeutics that targets downstream pathways including protein translation. We examined the effects of a series of inhibitors targeting various pathways on ribosomal polysome distribution, overall translation rates, and translation of specific mRNAs in the bone derived prostate cancer cell line, C4-2B. Treatment with either rapamycin, PD98059 or LY294002 failed to change the distribution of polysomes in sucrose gradients. Although no change in the accumulation of heavy polysomes was observed, there was an overall decrease in the rate of translation caused by treatment with rapamycin or LY294002. Inhibiting the MAPK pathway with PD98059 decreased overall translation by 20%, but had no effect on mRNAs containing a 5' terminal oligopyrimidine tract (TOP) sequences or those with complex 5' UTRs. In contrast, treatment with rapamycin for 24 h reduced overall translation by approximately 45% and affected the translation of mRNAs with complex 5' UTRs, specifically VEGF and HIF1alpha. After 24 h, LY294002 treatment alone decreased overall translation by 60%, more than was observed with rapamycin. Although LY294002 and similar inhibitors are effective at blocking prostate cancer cell growth, they act upstream of AKT and PTEN and cancer cells can find a way to bypass this inhibition. Thus, we propose that inhibiting downstream targets such as mTOR or targets of mTOR will provide rational approaches to developing new combination therapies focused on reducing growth of prostate cancer after arrival in the bone environment.

Topics: 5' Untranslated Regions; Antibiotics, Antineoplastic; Cell Line, Tumor; Humans; Male; Prostatic Neoplasms; Protein Biosynthesis; Ribosomes; Sirolimus

To evaluate the activation level of the mammalian target of rapamycin (mTOR) signalling pathway in Chinese patients with prostate cancer, as this pathway is over-activated in many human cancers and is an attractive target for cancer therapy.. We used immunohistochemistry to investigate the activation level of five important markers of the mTOR pathway, including PTEN, p-Akt, p-mTOR, p-p70S6K and p-4E-BP1, in tissues from 182 patients with prostate cancer, 20 with benign prostatic hyperplasia (BPH) and 10 with high-grade prostatic intraepithelial neoplasia (HGPIN). The expression levels of these five markers were associated with patient clinical and pathological characteristics.. Expression levels of p-Akt, p-mTOR, p-4E-BP1 and p-p70S6K were significantly higher in prostate cancer tissues than in BPH and HGPIN tissues. In 182 patients with prostate cancer the p-mTOR expression level significantly and positively correlated with its upstream p-Akt and downstream p-4E-BP1 and p-p70S6K expression levels. The cancer Gleason score was significantly correlated with p-Akt and p-mTOR expression level but not with p-4E-BP1 and p-p70S6K expression level. However, the p-4E-BP1 and p-p70S6K expression levels in primary cancer lesions were statistically significantly correlated with patient T stage and distant metastases.. Most patients with prostate cancer have at least one component of the mTOR signalling pathway activated. The activation of the mTOR pathway might be involved in prostate cancer development and progression. The association between activation of mTOR pathway and patient clinicopathological variables suggested that not all patients are equally amenable to treatment strategies targeting the mTOR pathway.

Topics: Adult; Aged; Aged, 80 and over; Biomarkers, Tumor; Disease Progression; Humans; Immunohistochemistry; Intracellular Signaling Peptides and Proteins; Male; Middle Aged; Phosphorylation; Prostatic Hyperplasia; Prostatic Intraepithelial Neoplasia; Prostatic Neoplasms; Protein Serine-Threonine Kinases; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

The tumor suppressor phosphatase and tensin homolog (PTEN) is frequently involved in human prostate carcinoma. PTEN is therefore an attractive target for the development of preclinical animal models. Prostate intraepithelial neoplasia lesions develop in mice with Pten heterozygosity, but disease progression has been reported only in combination with either other tumor suppressor gene alterations or the conditional inactivation of both Pten alleles in prostate epithelial cells. We report that on a C57BL/6 background, in contrast to previous studies on mixed 129 genetic backgrounds, Pten locus heterozygosity is fully penetrant for the development of prostate adenocarcinoma. Grossly observable tumors were detected at 6 months of age, and, by 10 to 12 months, 100% of examined mice developed adenocarcinoma of the anterior prostate. Furthermore, double heterozygotes carrying both Pten and Tsc2-null alleles showed no increase relative to Pten(+/-) heterozygotes in either lesion development or progression. Lesions in both Pten(+/-); Tsc2(+/-), and Pten(+/-) mice exhibited loss of PTEN expression and activation of PI3K signaling. PI3K activation occurred early in prostate intraepithelial neoplasia lesion formation in these animals, consistent with loss of PTEN function, and contributed to the etiology of tumors that developed in Pten(+/-) mice. Furthermore, prostate lesion growth in Pten(+/-) mice was dependent on mTOR, as evidenced by a reduction in both phospho-S6 levels and proliferative index after rapamycin treatment.

Topics: Adenocarcinoma; Animals; Blotting, Western; Disease Progression; Fluorescent Antibody Technique; Gene Expression Regulation, Neoplastic; Humans; Incidence; Loss of Heterozygosity; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Microsatellite Repeats; Phosphatidylinositol 3-Kinases; Prostatic Intraepithelial Neoplasia; Prostatic Neoplasms; Protein Kinases; Proto-Oncogene Proteins c-akt; PTEN Phosphohydrolase; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Tuberous Sclerosis Complex 2 Protein; Tumor Suppressor Proteins

Thymosin beta4, a major G-actin-sequestering protein, is known to be involved in tumor metastasis. In the present study, we found that thymosin beta4 expression promotes the formation of actin-based pseudopodia-like extensions, associated with cell migration, in human prostate cancer LNCaP cells. Treatment with the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin and Cdc42/Rac1/RhoA inhibitor Clostridium difficile toxin B significantly reduced pseudopodia formation in thymosin beta4-overexpressing LNCaP cells, suggesting that the pseudopodia formation by thymosin beta4 is probably involved in PI3K and Rho family pathway. We recently reported that thymosin beta4 expression is upregulated by androgen deprivation in prostate cancer cells. The increase in thymosin beta4 may be one of the causes of prostate cancer progression after androgen ablation therapy.

Topics: Androstadienes; Bacterial Proteins; Bacterial Toxins; Butadienes; cdc42 GTP-Binding Protein; Cell Line, Tumor; Cell Movement; Humans; Male; Microscopy, Phase-Contrast; Nitriles; Phosphoinositide-3 Kinase Inhibitors; Prostatic Neoplasms; Pseudopodia; rac1 GTP-Binding Protein; Reverse Transcriptase Polymerase Chain Reaction; rhoA GTP-Binding Protein; Sirolimus; Thymosin; Transfection; Wortmannin

The mammalian target of rapamycin (mTOR) signaling network regulates cell growth, proliferation, survival and apoptosis. This study was to investigate the effect and the underlying mechanism of rapamycin on prostate cancer PC-3 cells.. PC-3 cells were treated with 1 nmol/L rapamycin. The proliferation of PC-3 was examined by MTT. The cell cycle distribution of PC-3 was measured by FCM. The protein levels of raptor, rictor, Akt, pS6k1-T389, pAkt-s473 in PC-3 were examined by western blot.. Rapamycin increased the proliferation of PC-3 at 24 h, however, it remarkably inhibited cell proliferation after 36 h (P<0.01), which became more obviously at 72 h. Although incubation with rapamycin slightly induced cell arrest at the S phase at 24 h, this gradually increased PC-3 cells at the G1 phase at 36 h and 48 h. Compared with the control group, the protein levels of raptor and pS6k1-T389 were significantly decreased (P<0.01), and those of rictor and Akt remained unchanged after the treatment with rapamycin for 24 h; the protein level of pAkt-s473 was significantly increased at 24 h (P<0.01), but was obviously inhibited at 36 h and almost completely inhibited at 72 h (P<0.01).. Prolonged rapamycin treatment inhibits the proliferation of PC-3 cells. This may be caused by rapamycin-induced cell cycle arrest at the G(1) phase and inhibition of Akt phosphorylation.

Topics: Adaptor Proteins, Signal Transducing; Antibiotics, Antineoplastic; Carrier Proteins; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Dose-Response Relationship, Drug; Humans; Male; Phosphorylation; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; Rapamycin-Insensitive Companion of mTOR Protein; Regulatory-Associated Protein of mTOR; Ribosomal Protein S6 Kinases, 70-kDa; Signal Transduction; Sirolimus

To investigate the effect of the mammalian target of rapamycin (mTOR) inhibitor CCI-779 on the chemosensitivity of androgen-independent prostate cancer cell line PC-3.. Prostate cancer cells PC-3 were cultured and treated with CCI-779, Paclitaxel and combination of the two. Then the inhibitory effects of the three medications on the growth of the PC-3 cells were determined by MTT, and the their cell cycle and apoptosis were detected by flow cytometry.. Compared with the control group, the three medications all significantly inhibited the proliferation of the PC-3 cells, and the combined method even enhanced the effect. Flow cytometry showed that CCI-779 and Paclitaxel blocked the cell cycle mainly in the G1/G2 stage, while the combined medication mainly in the G0/G1 stage. Significantly increased apoptosis of the PC-3 cells was observed in the three medication groups as compared with the control group (P < 0.01).. CCI-779 can inhibit the proliferation of PC-3 cells and enhance the chemosensitivity of prostate cancer.

Topics: Antineoplastic Agents; Cell Cycle; Cell Line, Tumor; Drug Therapy, Combination; Humans; Male; Paclitaxel; Prostatic Neoplasms; Protein Kinase Inhibitors; Sirolimus

Optimal scheduling of cycle-active chemotherapy with (initially cytostatic) molecular-targeted agents is important to maximize clinical benefit. Concurrent scheduling might allow up-regulation of cell death pathways at the time of chemotherapy, whereas sequential treatments might maximize inhibition of repopulation and avoid putting tumor cells out of cycle when administering cycle-active chemotherapy. We compared the effects of concurrent and sequential administration of chemotherapy and the mammalian target of rapamycin (mTOR) inhibitor temsirolimus (CCI-779) on tumor cells and xenografts.. Human prostate cancer PC-3 and LnCaP, and human breast cancer MDA-468 cells and xenografts were treated with chemotherapy (docetaxel and 5-fluorouracil, respectively) and temsirolimus, using concurrent and sequential treatment schedules. Cell killing and repopulation were evaluated by clonogenic assays. Cell cycle analysis was done using flow cytometry. Effects on xenografts were assessed by tumor growth delay.. The proliferation of all cell lines was inhibited by temsirolimus in a dose-dependent manner; PTEN negative PC-3 and mutant LnCaP cells were more sensitive than PTEN-negative MDA-468 cells. Temsirolimus inhibited cell cycle progression from G(1) to S phase in all cell lines. Combined treatment had greater effects than temsirolimus or chemotherapy alone: for PC-3 and LnCaP xenografts, concurrent treatment seemed superior to sequential scheduling, whereas MDA-468 cells and xenograft tumors did not show schedule dependence.. Combined treatment with temsirolimus and chemotherapy had a greater therapeutic effect than monotherapy; concurrent scheduling was more effective for PC-3 and LnCaP cells and xenografts that were sensitive to temsirolimus.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Breast Neoplasms; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Docetaxel; Drug Synergism; Female; Fluorouracil; Humans; Male; Mice; Mice, Nude; Prostatic Neoplasms; Protein Kinase Inhibitors; Protein Kinases; Sirolimus; Taxoids; TOR Serine-Threonine Kinases; Xenograft Model Antitumor Assays

Androgen receptors have been shown to play a critical role in prostate cancer. We used ultrasound imaging techniques to track tumor response to antiandrogen and rapamycin treatment in a prostate-specific Pten-deleted mouse model of cancer. Depletion of androgens by either surgical or chemical castration significantly inhibited tumor growth progression without altering the activation of Akt and mammalian target of rapamycin (mTOR). We also showed for the first time that targeting mTOR along with antiandrogen treatment exhibited additive antitumor effects in vivo when compared with single agents. Our preclinical data suggest that combination of antiandrogens with mTOR inhibitors might be more effective in treating androgen-dependent prostate cancer patients.

Topics: Androgen Antagonists; Animals; Antineoplastic Combined Chemotherapy Protocols; Carrier Proteins; Cell Growth Processes; Imaging, Three-Dimensional; Male; Mice; Mice, Inbred C57BL; Mice, Inbred DBA; Oncogene Protein v-akt; Phosphotransferases (Alcohol Group Acceptor); Prostatic Neoplasms; PTEN Phosphohydrolase; Sirolimus; TOR Serine-Threonine Kinases; Ultrasonography

Loss of PTEN and activation of phosphoinositide 3-kinase are commonly observed in advanced prostate cancer. Inhibition of mammalian target of rapamycin (mTOR), a downstream target of phosphoinositide 3-kinase signaling, results in cell cycle arrest and apoptosis in multiple in vitro and in vivo models of prostate cancer. However, single-agent use of mTOR inhibition has limited clinical success, and the identification of molecular events mitigating tumor response to mTOR inhibition remains a critical question. Here, using genetically engineered human prostate epithelial cells (PrEC), we show that MYC, a frequent target of genetic gain in prostate cancers, abrogates sensitivity to rapamycin by decreasing rapamycin-induced cytostasis and autophagy. Analysis of MYC and the mTOR pathway in human prostate tumors and PrEC showed selective increased expression of eukaryotic initiation factor 4E-binding protein 1 (4EBP1) with gain in MYC copy number or forced MYC expression, respectively. We have also found that MYC binds to regulatory regions of the 4EBP1 gene. Suppression of 4EBP1 expression resulted in resensitization of MYC-expressing PrEC to rapamycin and increased autophagy. Taken together, our findings suggest that MYC expression abrogates sensitivity to rapamycin through increased expression of 4EBP1 and reduced autophagy.

Topics: Antibiotics, Antineoplastic; Autophagy; Cell Line, Tumor; Drug Resistance, Neoplasm; E-Box Elements; Eukaryotic Initiation Factor-4E; Genes, myc; Humans; Male; Prostatic Neoplasms; Protein Kinases; Proto-Oncogene Proteins c-myc; Sirolimus; TOR Serine-Threonine Kinases; Tunicamycin

Penta-1,2,3,4,6-O-galloyl-beta-d-glucose (PGG) suppresses the in vivo growth of human DU145 and PC-3 prostate cancer xenografts in nude mice, suggesting potential utility as a prostate cancer chemotherapeutic or chemopreventive agent. Our earlier work implicates caspase-mediated apoptosis in DU145 and LNCaP prostate cancer cells as one mechanism for the anticancer activity. We show here that, in the more aggressive PC-3 prostate cancer cell line, PGG induced programmed cell deaths lacking the typical caspase-mediated apoptotic morphology and biochemical changes. In contrast, PGG induced patent features of autophagy, including formation of autophagosomes and lipid modification of light chain 3 after 48 hours of PGG exposure. The "autophagic" responses were also observed in the murine TRAMP-C2 cells. Caspase inhibition exacerbated PGG-induced overall death. As for molecular changes, we observed a rapid inhibition of the phosphorylation of mammalian target of rapamycin-downstream targets S6K and 4EBP1 by PGG in PC-3 and TRAMP-C2 cells but not that of mammalian target of rapamycin itself, along with increased AKT phosphorylation. Whereas the inhibition of phosphatidylinositol 3-kinase increased PGG-induced apoptosis and autophagy, experiments with pharmacologic inducer or inhibitor of autophagy or by knocking down autophagy mediator Beclin-1 showed that autophagy provided survival signaling that suppressed caspase-mediated apoptosis. Knocking down of death receptor-interacting protein 1 kinase increased overall death without changing light chain 3-II or caspase activation, thus not supporting death receptor-interacting protein 1-necroptosis for PGG-induction of autophagy or other programmed cell death. Furthermore, PGG-treated PC-3 cells lost clonogenic ability. The induction by PGG of caspase-independent programmed cell death in aggressive prostate cancer cell lines supports testing its merit as a potential drug candidate for therapy of caspase-resistant recurrent prostate cancer.

Topics: Adenine; Animals; Apoptosis; Apoptosis Regulatory Proteins; Autophagy; Beclin-1; Caspases; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Drug Screening Assays, Antitumor; Enzyme Activation; Gene Knockdown Techniques; GTPase-Activating Proteins; Humans; Hydrolyzable Tannins; Male; Membrane Proteins; Mice; Phosphatidylinositol 3-Kinases; Prostatic Neoplasms; Protein Kinases; Proto-Oncogene Proteins c-akt; Reactive Oxygen Species; Sirolimus; TOR Serine-Threonine Kinases; Tumor Stem Cell Assay

While NF-kappaB is considered to play key roles in the development and progression of many cancers, the mechanisms whereby this transcription factor is activated in cancer are poorly understood. A key oncoprotein in a variety of cancers is the serine-threonine kinase Akt, which can be activated by mutations in PI3K, by loss of expression/activity of PTEN, or through signaling induced by growth factors and their receptors. A key effector of Akt-induced signaling is the regulatory protein mTOR (mammalian target of rapamycin). We show here that mTOR downstream from Akt controls NF-kappaB activity in PTEN-null/inactive prostate cancer cells via interaction with and stimulation of IKK. The mTOR-associated protein Raptor is required for the ability of Akt to induce NF-kappaB activity. Correspondingly, the mTOR inhibitor rapamycin is shown to suppress IKK activity in PTEN-deficient prostate cancer cells through a mechanism that may involve dissociation of Raptor from mTOR. The results provide insight into the effects of Akt/mTOR-dependent signaling on gene expression and into the therapeutic action of rapamycin.

Topics: Adaptor Proteins, Signal Transducing; Gene Expression Regulation; HeLa Cells; Humans; I-kappa B Kinase; Male; NF-kappa B; Prostatic Neoplasms; Protein Kinases; Proteins; Proto-Oncogene Proteins c-akt; Regulatory-Associated Protein of mTOR; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Tumor Cells, Cultured

Prostate cancer is the most frequent malignancy of the male population. Every year in Germany approximately 12,000 patients die of their hormone-refractory prostate cancer even though early detection is able to find more curable prostate cancers. In a hormone-refractory stage we only have limited options for treatment. Although docetaxel is currently the standard of care in most hormone-refractory prostate cancers, it is not the magic therapy that will dramatically change the patient's poor survival. This drug provides an overall survival advantage of 2 months. During recent years, significant progress has been made in the field of molecular therapy in urologic oncology. Targeted therapy leads to an inhibition of angiogenesis and proliferation in malignant tumors. Even if there is a great theoretical potential, mono- and combination therapies with target substances are not relevant in the clinical routine.

Topics: Angiogenesis Inhibitors; Antineoplastic Agents; Atrasentan; Calcitriol; Drug Delivery Systems; Humans; Male; Neoplasm Staging; Prostatic Neoplasms; Protein-Tyrosine Kinases; Pyrrolidines; Sirolimus; Survival Rate; Thionucleotides

Resistance to cell death is a hallmark of cancer. Autophagy is a survival mechanism activated in response to nutrient deprivation; however, excessive autophagy will ultimately induce cell death in a nonapoptotic manner. The present study demonstrates that CCL2 protects prostate cancer PC3 cells from autophagic death, allowing prolonged survival in serum-free conditions. Upon serum starvation, CCL2 induced survivin up-regulation in PC3, DU 145, and C4-2B prostate cancer cells. Both cell survival and survivin expression were stunted in CCL2-stimulated PC3 cells when treated either with the phosphatidylinositol 3-kinase inhibitor LY294002 (2 microm) or the Akt-specific inhibitor-X (Akti-X; 2.5 microm). Furthermore, CCL2 significantly reduced light chain 3-II (LC3-II) in serum-starved PC3; in contrast, treatment with LY294002 or Akti-X reversed the effect of CCL2 on LC3-II levels, suggesting that CCL2 signaling limits autophagy in these cells. Upon serum deprivation, the analysis of LC3 localization by immunofluorescence revealed a remarkable reduction in LC3 punctate after CCL2 stimulation. CCL2 treatment also resulted in a higher sustained mTORC1 activity as measured by an increase in phospho-p70S6 kinase (Thr389). Rapamycin, an inducer of autophagy, both down-regulated survivin and decreased PC3 cell viability in serum-deprived conditions. Treatment with CCL2, however, allowed cells to partially resist rapamycin-induced death, which correlated with survivin protein levels. In two stable transfectants expressing survivin-specific short hairpin RNA, generated from PC3, survivin protein levels controlled both cell viability and LC3 localization in response to CCL2 treatment. Altogether, these findings indicate that CCL2 protects prostate cancer PC3 cells from autophagic death via the phosphatidylinositol 3-kinase/Akt/survivin pathway and reveal survivin as a critical molecule in this survival mechanism.

Topics: Antibiotics, Antineoplastic; Autophagy; Cell Line, Tumor; Cell Survival; Chemokine CCL2; Culture Media, Serum-Free; Enzyme Inhibitors; Gene Expression Regulation, Neoplastic; Humans; Inhibitor of Apoptosis Proteins; Male; Mechanistic Target of Rapamycin Complex 1; Microtubule-Associated Proteins; Multiprotein Complexes; Neoplasm Proteins; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Prostatic Neoplasms; Proteins; Proto-Oncogene Proteins c-akt; Ribosomal Protein S6 Kinases, 70-kDa; Sirolimus; Survivin; TOR Serine-Threonine Kinases; Transcription Factors; Up-Regulation

The mTOR (mammalian target of rapamycin) inhibitor rapamycin caused growth arrest in both androgen-dependent and androgen-independent prostate cancer cells; however, long-term treatment induced resistance to the drug. The aim of this study was to investigate methods that can overcome this resistance. Here, we show that rapamycin treatment stimulated androgen receptor (AR) transcriptional activity, whereas suppression of AR activity with the antiandrogen bicalutamide sensitized androgen-dependent, as well as AR-sensitive androgen-independent prostate cancer cells, to growth inhibition by rapamycin. Further, the combination of rapamycin and bicalutamide, but not the individual drugs, induced significant levels of apoptosis in prostate cancer cells. The net effect of rapamycin is determined by its individual effects on the mTOR complexes mTORC1 (mTOR/raptor/GbetaL) and mTORC2 (mTOR/rictor/sin1/GbetaL). Inhibition of both mTORC1 and mTORC2 by rapamycin-induced apoptosis, whereas rapamycin-stimulation of AR transcriptional activity resulted from the inhibition of mTORC1, but not mTORC2. The effect of rapamycin on AR transcriptional activity was mediated by the phosphorylation of the serine/threonine kinase Akt, which also partially mediated apoptosis induced by rapamycin and bicalutamide. These results indicate the presence of two parallel cell-survival pathways in prostate cancer cells: a strong Akt-independent, but rapamycin-sensitive pathway downstream of mTORC1, and an AR-dependent pathway downstream of mTORC2 and Akt, that is stimulated by mTORC1 inhibition. Thus, the combination of rapamycin and bicalutamide induce apoptosis in prostate cancer cells by simultaneously inhibiting both pathways and hence would be of therapeutic value in prostate cancer treatment.

Topics: Adaptor Proteins, Signal Transducing; Apoptosis; Carrier Proteins; Cell Line, Tumor; Cell Proliferation; Cell Survival; Gene Expression Regulation, Neoplastic; Humans; Male; Mechanistic Target of Rapamycin Complex 1; Multiprotein Complexes; Prostatic Neoplasms; Proteins; Proto-Oncogene Proteins c-akt; Rapamycin-Insensitive Companion of mTOR Protein; Receptors, Androgen; Regulatory-Associated Protein of mTOR; Sirolimus; TOR Serine-Threonine Kinases; Transcription Factors; Transcription, Genetic

Deregulation of the phosphatidyl inositol trisphosphate kinase/AKT/mammalian target of rapamycin (mTOR) and RAS/mitogen-activated protein kinase (MAPK)/MNK pathways frequently occurs in human prostate carcinomas (PCas) and leads to aberrant modulation of messenger RNA (mRNA) translation. We have investigated the relative contribution of these pathways to translational regulation and proliferation of PCa cells. MNK-dependent phosphorylation of eIF4E is elevated in DU145 cells, which have low basal levels of AKT/mTOR activity due to the expression of the tumor suppressor PTEN. In contrast, eIF4E phosphorylation is low in PC3 and LNCaP cells with mutated PTEN and constitutively active AKT/mTOR pathway, but it can be strongly induced through inhibition of mTOR activity by rapamycin or serum depletion. Remarkably, we found that inhibition of MNKs strongly reduced the polysomal recruitment of terminal oligopyrimidine messenger RNAs (TOP mRNAs), which are known targets of mTOR-dependent translational control. Pull-down assays of the eIF4F complex indicated that translation initiation was differently affected by inhibition of MNKs and mTOR. In addition, concomitant treatment with MNK inhibitor and rapamycin exerted additive effects on polysomal recruitment of TOP mRNAs and protein synthesis. The MNK inhibitor was more effective than rapamycin in blocking proliferation of PTEN-expressing cells, whereas combination of the two inhibitors suppressed cell cycle progression in both cell lines. Microarray analysis showed that MNK affected translation of mRNAs involved in cell cycle progression. Thus, our results indicate that a balance between the activity of the AKT/mTOR and the MAPK/MNK pathway in PCa cells maintains a defined translational level of specific mRNAs required for ribosome biogenesis, cell proliferation and stress response and might confer to these cells the ability to overcome negative insults.

Topics: Adenosine Triphosphatases; Biomarkers, Tumor; Blotting, Western; Cation Transport Proteins; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Copper-Transporting ATPases; Enzyme Inhibitors; Eukaryotic Initiation Factor-4E; Humans; Male; Mitogen-Activated Protein Kinases; Phosphorylation; Polyribosomes; Prostatic Neoplasms; Protein Array Analysis; Protein Biosynthesis; Protein Kinases; Proto-Oncogene Proteins c-akt; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

Currently, no second-line treatment exists for hormonerefractory prostate cancer (HRPC) cases that fail docetaxel regimens. Rapamycin, an immunosuppressive macrolide, inhibits metastatic prostate tumor growth and angiogenesis in in vivo mouse models. This pilot study assessed the antitumor activity, safety, and toxicity of rapamycin in patients with HRPC.. Eligible patients had HRPC and disease progression. The initial dose of rapamycin was 0.15 mg/kg followed by 0.04 mg/kg daily without interruption. Rapamycin levels were measured every 28 days with dose adjustments of 0.04-0.06 mg/kg as necessary to maintain levels between 6-10 ng/mL. Patients were evaluated every 4 weeks for prostate-specific antigen (PSA) and safety and every 8 weeks for radiographic response.. Thirteen patients were enrolled from January 2005 to February 2006. One was not evaluable for response. Responses were seen in 2 of 12 evaluable patients (17%). One patient experienced a 50% decrease in absolute PSA and partial radiographic response; another experienced a PSA response only. Four patients had stable disease (33%). The median progression-free survival was 4.2 months (range, 1.9-23.3 months), and overall survival was 23.3+ months (range, 1.9-34.3+ months). Diarrhea (69%), fatigue (46%), and nausea (46%) were the most common adverse events. Rapamycin was well tolerated and showed signs of antitumor activity.. Rapamycin and other inhibitors of mammalian targets of rapamycin warrant further study in developing combination therapies with chemotherapy or radiation.

Topics: Aged; Aged, 80 and over; Antineoplastic Agents, Hormonal; Disease-Free Survival; Drug Administration Schedule; Drug Evaluation; Drug Resistance, Neoplasm; Humans; Male; Middle Aged; Pilot Projects; Prostate-Specific Antigen; Prostatic Neoplasms; Radiography; Sirolimus

In kidney recipients, the immunosuppressant sirolimus has been associated with a decreased incidence of de novo posttransplant malignancies (including prostate cancer). But the effect of sirolimus on the prostate-specific antigen (PSA) blood level, an important prostate cancer screening tool, remains unknown. We studied male kidney recipients >50 years old (transplanted from January 1994 to December 2006) without clinical evidence for prostate cancer. Pre- and posttransplant PSA levels were analyzed for 97 recipients (n = 19 on sirolimus, n = 78 on tacrolimus [control group]). Pretransplant PSA was similar for sirolimus versus tacrolimus recipients (mean, 1.8 versus 1.7 ng/mL, p = 0.89), but posttransplant PSA was significantly lower for recipients on sirolimus (mean, 0.9 versus 1.9 ng/mL, respectively, p < 0.001). The mean difference between pretransplant and posttransplant PSA was -0.9 ng/mL (50.0%, p = 0.006) for the sirolimus group versus +0.2 ng/mL (+11.8%, p = 0.24) for the tacrolimus group. By multivariate analysis, only pretransplant PSA and immunosuppression with sirolimus independently impacted posttransplant PSA. Our data strongly suggest that sirolimus is associated with a significant PSA decrease in kidney recipients. Future studies must investigate the clinical implications of our findings for the use of PSA for prostate cancer screening in male kidney recipients on sirolimus.

Topics: Case-Control Studies; Humans; Immunosuppressive Agents; Kidney Transplantation; Male; Mass Screening; Middle Aged; Multivariate Analysis; Prostate-Specific Antigen; Prostatic Neoplasms; Retrospective Studies; Sirolimus; Tacrolimus; Transplantation

Proper activation of phosphoinositide 3-kinase-Akt pathway is critical for the prevention of tumorigenesis. Recent data have characterized a negative feedback loop, wherein mammalian target of rapamycin (mTOR) blocks additional activation of the Akt/mTOR pathway through inhibition insulin receptor substrate 1 (IRS-1) function. However, the potential of IRS-1 inhibition during rapamycin treatment has not been examined. Herein, we show that IRS-1 antisense oligonucleotide and rapamycin synergistically antagonize the activation of mTOR in vivo and induced tumor suppression, through inhibition of proliferation and induction of apoptosis, in prostate cancer cell xenografts. These data demonstrate that the addition of agents that blocks IRS-1 potentiate the effect of mTOR inhibition in the growth of prostate cancer cell xenografts.

Topics: Adaptor Proteins, Signal Transducing; Animals; Antibiotics, Antineoplastic; Apoptosis; Blotting, Western; Cell Line, Tumor; Cell Proliferation; Enzyme Activation; Humans; Insulin Receptor Substrate Proteins; Male; Mice; Mice, SCID; Phosphorylation; Prostatic Neoplasms; Protein Kinases; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Xenograft Model Antitumor Assays

Platelet-derived growth factor-D (PDGF-D) is a newly recognized growth factor known to regulate many cellular processes, including cell proliferation, transformation, invasion, and angiogenesis. Recent studies have shown that PDGF-D and its cognate receptor PDGFR-beta are expressed in prostate tumor tissues, suggesting that PDGF-D might play an important role in the development and progression of prostate cancer. However, the biological role of PDGF-D in tumorigenesis remains elusive. In this study, we found that PDGF-D-overexpressing PC3 cells (PC3 cells stably transfected with PDGF-D cDNA and referred to as PC3 PDGF-D) exhibited a rapid growth rate and enhanced cell invasion that was associated with the activation of mammalian target of rapamycin (mTOR) and reduced Akt activity. Rapamycin repressed mTOR activity and concomitantly resulted in the activation of Akt, which could attenuate the therapeutic effects of mTOR inhibitors. In contrast, B-DIM (BR-DIM from Bioresponse, Inc.; a chemopreventive agent) significantly inhibited both mTOR and Akt in PC3 PDGF-D cells, which were correlated with decreased cell proliferation and invasion. Moreover, conditioned medium from PC3 PDGF-D cells significantly increased the tube formation of human umbilical vein endothelial cells, which was inhibited by B-DIM treatment concomitant with reduced full-length and active form of PDGF-D. Our results suggest that B-DIM could serve as a novel and efficient chemopreventive and/or therapeutic agent by inactivation of both mTOR and Akt activity in PDGF-D-overexpressing prostate cancer.

Topics: Cell Growth Processes; Cell Line, Tumor; Enzyme Activation; Humans; Indoles; Lymphokines; Male; Neoplasm Invasiveness; Neovascularization, Pathologic; Platelet-Derived Growth Factor; Prostatic Neoplasms; Protein Kinase Inhibitors; Protein Kinases; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-bcl-2; Sirolimus; TOR Serine-Threonine Kinases; Transfection; Up-Regulation

mTOR activity is increased in advanced prostate cancer (CaP) as a result of a high rate of PTEN mutations. RAD001 (Everolimus) is a new orally available mTOR inhibitor. The objective of our study was to evaluate the effects of RAD001 on the growth of CaP in the bone, both alone and in combination with docetaxel and zoledronic acid.. C4-2 CaP cells were injected into tibiae of mice and the animals were treated with RAD001, docetaxel, and zoledronic acid alone or in combination. Histomorphometrical analysis, serum PSA measurements, bone mineral density (BMD), and microCT were used to determine the effects of treatment on tumor and bone.. All three agents alone decreased tumor volume, and RAD001 and docetaxel also decreased levels of serum PSA by 68% and 65%, respectively (both P < 0.01). Combinations of the agents were more effective in decreasing tumor volume than single agents. Three-drug treatment showed the greatest effect: 64% inhibition versus control (P < 0.01). Treatment with RAD001 interfered with the weight loss associated with growth of this tumor in the bone (non-RAD001 groups: 4.0% decrease in body weight, P = 0.0014; RAD001 groups: increase of 3.6% in body weight, P = 0.0037).. RAD001 inhibited growth of C4-2 cells in bone, an effect augmented by addition of docetaxel and zoledronic acid. Moreover RAD001 had a significant impact on maintenance of body weight. RAD001 may hold promise for its effects on both metastatic CaP and the important syndrome of tumor cachexia.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Body Weight; Bone Neoplasms; Cell Line, Tumor; Cell Proliferation; Diphosphonates; Docetaxel; Everolimus; Humans; Imidazoles; Male; Mice; Prostatic Neoplasms; Protein Kinase Inhibitors; Protein Kinases; Sirolimus; Taxoids; Tomography, X-Ray Computed; TOR Serine-Threonine Kinases; Zoledronic Acid

The mammalian target of rapamycin (mTOR) inhibitor CCI-779 (temsirolimus) is a recently Food and Drug Administration-approved anticancer drug with efficacy in certain solid tumors and hematologic malignancies. In cell culture studies, CCI-779 at the commonly used nanomolar concentrations generally confers a modest and selective antiproliferative activity. Here, we report that, at clinically relevant low micromolar concentrations, CCI-779 completely suppressed proliferation of a broad panel of tumor cells. This "high-dose" drug effect did not require FKBP12 and correlated with an FKBP12-independent suppression of mTOR signaling. An FKBP12-rapamycin binding domain (FRB) binding-deficient rapamycin analogue failed to elicit both the nanomolar and micromolar inhibitions of growth and mTOR signaling, implicating FRB binding in both actions. Biochemical assays indicated that CCI-779 and rapamycin directly inhibited mTOR kinase activity with IC(50) values of 1.76 +/- 0.15 and 1.74 +/- 0.34 micromol/L, respectively. Interestingly, a CCI-779-resistant mTOR mutant (mTOR-SI) displayed an 11-fold resistance to the micromolar CCI-779 in vitro (IC(50), 20 +/- 3.4 micromol/L) and conferred a partial protection in cells exposed to micromolar CCI-779. Treatment of cancer cells with micromolar but not nanomolar concentrations of CCI-779 caused a marked decline in global protein synthesis and disassembly of polyribosomes. The profound inhibition of protein synthesis was accompanied by rapid increase in the phosphorylation of translation elongation factor eEF2 and the translation initiation factor eIF2 alpha. These findings suggest that high-dose CCI-779 inhibits mTOR signaling through an FKBP12-independent mechanism that leads to profound translational repression. This distinctive high-dose drug effect could be directly related to the antitumor activities of CCI-779 and other rapalogues in human cancer patients.

Topics: Antineoplastic Agents; Breast Neoplasms; Cell Division; Cell Line; Cell Line, Tumor; Colonic Neoplasms; Female; Humans; Kidney; Lung Neoplasms; Male; Prostatic Neoplasms; Protein Biosynthesis; Protein Kinases; Sirolimus; Tacrolimus Binding Protein 1A; TOR Serine-Threonine Kinases

Vascular endothelial growth factor (VEGF) and hypoxia-inducible factor 1 (HIF-1) are important regulators of angiogenesis. HIF-1 is composed of HIF-1alpha and HIF-1beta subunits, and regulates VEGF expression at transcriptional level. In this study, we demonstrated that insulin induced H2O2 production and p70S6K1 activation in PC-3 prostate cancer cells. The inhibition of H2O2 production by catalase abolished insulin-induced p70S6K1 activation. H2O2 production is also required for insulin-induced VEGF and HIF-1alpha expression in the cells. Over-expression of p70S6K1 or HIF-1alpha reversed catalase- and rapamycin-inhibited VEGF transcriptional activation. These results suggest that insulin induced HIF-1alpha and VEGF expression through H2O2 production and p70S6K1 activation in prostate cancer cells. In addition, we found that inhibition of p70S6K1 by rapamycin decreased prostate tumor angiogenesis, suggesting that p70S6K1 plays an important role in tumor angiogenesis. These results provide some useful information for prostate cancer therapy in the future.

Topics: Animals; Catalase; Cell Line, Tumor; Enzyme Activation; Enzyme-Linked Immunosorbent Assay; Humans; Hydrogen Peroxide; Hypoglycemic Agents; Hypoxia-Inducible Factor 1, alpha Subunit; Immunoblotting; Immunoenzyme Techniques; Immunosuppressive Agents; Insulin; Male; Mice; Mice, Inbred BALB C; Mice, Nude; Neovascularization, Pathologic; Prostatic Neoplasms; Reactive Oxygen Species; Reverse Transcriptase Polymerase Chain Reaction; Ribosomal Protein S6 Kinases, 70-kDa; RNA, Messenger; Sirolimus; Transcription, Genetic; Vascular Endothelial Growth Factor A

Survivin is a dual regulator of cell proliferation and cell viability overexpressed in most human tumors. Although strategies to lower survivin levels have been pursued for rational cancer therapy, the molecular circuitries controlling survivin expression in tumors have not been completely elucidated. Here, we show that stimulation with insulin-like growth factor-1 (IGF-1) results in increased survivin expression in prostate cancer cells. This response is independent of de novo gene transcription, changes in mRNA expression or modifications of survivin protein stability. Instead, IGF-1 induced persistence and translation of a pool of survivin mRNA, in a reaction abolished by the mTOR (mammalian target of rapamycin) inhibitor, rapamycin. Forced expression of the mTOR target p70S6K1 reproduced the increase in survivin expression in prostate cancer cells, whereas acute ablation of endogenous p70S6K1 by small interfering RNA downregulated survivin levels. Rapamycin, alone or in combination with suboptimal concentrations of taxol reduced survivin protein levels, and decreased viability of prostate cancer cells. Therefore, IGF-1/mTOR signaling elevates survivin in prostate cancer cells via rapid changes in mRNA translation. Antagonists of this pathway may be beneficial to lower an antiapoptotic threshold maintained by survivin in prostate cancer.

Topics: Animals; Apoptosis; Cell Cycle; Cell Proliferation; Down-Regulation; Gene Expression Regulation, Neoplastic; HeLa Cells; Humans; Inhibitor of Apoptosis Proteins; Insulin-Like Growth Factor I; Male; Mice; Mice, Knockout; Microtubule-Associated Proteins; Neoplasm Proteins; Promoter Regions, Genetic; Prostatic Neoplasms; Protein Kinases; Receptor, IGF Type 1; Ribosomal Protein S6 Kinases, 70-kDa; RNA Stability; RNA, Small Interfering; Signal Transduction; Sirolimus; Survivin; TOR Serine-Threonine Kinases; Transcription, Genetic; Tumor Cells, Cultured

Inhibition of the mammalian target of rapamycin (mTOR) signaling pathway is a potentially useful therapeutic strategy in the treatment of advanced prostate cancer. However mTOR antagonists used as single agents are not likely to result in dramatic clinical responses, so that it is useful to identify prospective agents that might be useful in combination. We treated CWR22Rv1 and LNCaP prostate cancer cells with an mTOR inhibitor, rapamycin, alone, or in combination with either of two receptor protein kinase (RTK) inhibitors. We assessed the effects of these treatments on cell survival and activation of down-stream mTOR target proteins. Treatment with either PD16839, an EGFr antagonist, or imatinib mesylate (Gleevec), a PDGFr, c-kit and bcr/abl antagonist, enhanced the anti-proliferative effects of rapamycin. We therefore assessed the effects of treatment with the RTK antagonist alone and in combination with rapamycin on mTOR targeted proteins. RTK antagonists alone had no effect or paradoxically increased phosphorylation of the mTOR targeted proteins, p70 S6 kinase and ribosomal S6. In contrast, when these cells were treated with either RTK antagonist in the presence of rapamycin, there was a dramatic decrease in phosphorylation of these two mTOR-targeted proteins. These effects were not mediated through phospho-AKT. Since two separate RTK antagonists had additive antiproliferative effects in combination with an mTOR antagonist and were associated with a dramatic decrease in mTOR targeted proteins in cells with or without PTEN expression, the strategy deserves further evaluation for the treatment of prostate cancer.

Topics: Antineoplastic Agents; Benzamides; Blotting, Western; Cell Line, Tumor; Cell Proliferation; Cell Survival; Gene Expression Regulation, Neoplastic; Humans; Imatinib Mesylate; Male; Piperazines; Prostatic Neoplasms; Protein Kinase Inhibitors; Protein Kinases; Pyrimidines; Receptor Protein-Tyrosine Kinases; Sirolimus; TOR Serine-Threonine Kinases; Treatment Outcome

Fibroblast growth factor-2 (FGF-2) has been shown to induce both angiogenesis and lymphangiogenesis in the mouse corneum; however, the signalling mechanism underlying FGF-2-induced lymphangiogenesis remains unknown. Here we investigated the effect of FGF-2 on newly developed temperature-sensitive rat lymphatic endothelial (TR-LE) cells. The supernatant of PC-3 prostate cancer cells facilitated tube-like formation in TR-LE cells, and formation was inhibited by neutralising antibodies against FGF-2. The addition of FGF-2 stimulated tube-like formation as well as proliferation and chemotactic migration of TR-LE cells. Blockade of the Akt signalling pathway by LY294002 abolished the elongation of tubes induced by FGF-2, whereas inhibition of the extracellular signal-regulated kinase (ERK) signalling pathway had no effect. Rapamycin abrogated the phosphorylation of p70S6kinase and consistently inhibited the formation of tubes induced by FGF-2. Furthermore, tube-like formation induced by the supernatant of PC-3 cells was inhibited by LY294002 or rapamycin. These data suggest that FGF-2 exerts lymphangiogenic effects by activating the Akt/mammalian target of rapamycin (mTOR)/p70S6kinase pathway in lymphatic endothelial cells, and that the pathway provides a potent target for tumour lymphangiogenesis.

Topics: Animals; Cell Communication; Chromones; Endothelial Cells; Enzyme Inhibitors; Fibroblast Growth Factor 2; Lymphatic Metastasis; Male; Microtubules; Morpholines; Piperazines; Prostatic Neoplasms; Rats; Ribosomal Protein S6 Kinases, 70-kDa; Sirolimus; Tumor Cells, Cultured

A cell line that we designed, AILNCaP, proliferated in androgen-depleted medium after emerging from long-term androgen-depleted cultures of an androgen-sensitive prostate cancer cell line, LNCaP. Using this cell line as a model of progression to androgen independence, we demonstrated that the activity of the mammalian target of rapamycin/p70 S6 kinase transduction pathway is down-regulated after androgen depletion in LNCaP, whereas its activation is related to transition of this cell line to androgen-independent proliferation. Kinase activity of protein kinase Czeta is regulated by androgen stimulation in LNCaP cells, whereas it is activated constitutively in AILNCaP cells under androgen-depleted conditions. Treatment with a protein kinase Czeta pseudosubstrate inhibitor reduced p70 S6 kinase activity and cell proliferation in both cell lines. We identified that both protein kinase Czeta and p70 S6 kinase were associated in LNCaP cells and this association was enhanced by the androgen stimulation. We examined the expression of phospho-protein kinase Czeta and phospho-p70 S6 kinase in hormone-naive prostate cancer specimens and found that the expression of both kinases was correlated with each other in those specimens. Significant correlation was observed between the expression of both kinases and Ki67 expression. Most of the prostate cancer cells that survived after prior hormonal treatment also expressed both kinases. This is the first report that shows the significance of this pathway for both androgen-dependent and -independent cell proliferation in prostate cancer. Our data suggest that protein kinase Czeta/mammalian target of rapamycin/S6 kinase pathway plays an important role for the transition of androgen-dependent to androgen-independent prostate cancer cells.

Topics: Androgens; Cell Line; Cell Proliferation; Culture Media; Enzyme Activation; Humans; Ki-67 Antigen; Male; Prostatic Neoplasms; Protein Kinase C; Protein Kinase Inhibitors; Protein Kinases; Ribosomal Protein S6 Kinases, 70-kDa; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Tumor Cells, Cultured

The phosphatidylinositol 3-kinase/Akt pathway plays a critical role in oncogenesis, and dysregulation of this pathway through loss of PTEN suppression is a particularly common phenomenon in aggressive prostate cancers. The mammalian target of rapamycin (mTOR) is a downstream signaling kinase in this pathway, exerting prosurvival influence on cells through the activation of factors involved in protein synthesis. The mTOR inhibitor rapamycin and its derivatives are cytotoxic to a number of cell lines. Recently, mTOR inhibition has also been shown to radiosensitize endothelial and breast cancer cells in vitro. Because radiation is an important modality in the treatment of prostate cancer, we tested the ability of the mTOR inhibitor RAD001 (everolimus) to enhance the cytotoxic effects of radiation on two prostate cancer cell lines, PC-3 and DU145. We found that both cell lines became more vulnerable to irradiation after treatment with RAD001, with the PTEN-deficient PC-3 cell line showing the greater sensitivity. This increased susceptibility to radiation is associated with induction of autophagy. Furthermore, we show that blocking apoptosis with caspase inhibition and Bax/Bak small interfering RNA in these cell lines enhances radiation-induced mortality and induces autophagy. Together, these data highlight the emerging importance of mTOR as a molecular target for therapeutic intervention, and lend support to the idea that nonapoptotic modes of cell death may play a crucial role in improving tumor cell kill.

Topics: Animals; Autophagy; bcl-2 Homologous Antagonist-Killer Protein; bcl-2-Associated X Protein; Cell Line, Tumor; Everolimus; Humans; Male; Mice; Prostatic Neoplasms; Protein Kinase Inhibitors; Protein Kinases; PTEN Phosphohydrolase; Radiation-Sensitizing Agents; RNA, Small Interfering; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

Cancer cells frequently evade apoptosis during tumorigenesis by acquiring mutations in apoptotic regulators. Chronic activation of the PI 3-kinase-Akt pathway through loss of the tumor suppressor PTEN is one mechanism by which these cells can gain increased protection against apoptosis. We report here that REDD1 (RTP801) can act as a transcriptional downstream target of PI 3-kinase signaling in human prostate cancer cells (PC-3). REDD1 expression is markedly reduced in PC-3 cells treated with LY294002 (LY) or Rapamycin and strongly induced under hypoxic conditions in a hypoxia-inducible factor-1 (HIF-1)-dependent manner. Loss of function studies employing antisense molecules or RNA interference indicate that REDD1 is essential for invasive growth of prostate cancer cells in vitro and in vivo. Reduced REDD1 levels can sensitize cells towards apoptosis, whereas elevated levels of REDD1 induced by hypoxia or overexpression desensitize cells to apoptotic stimuli. Taken together our data designate REDD1 as a novel target for therapeutic intervention in prostate cancer.

Topics: Apoptosis; Cell Hypoxia; Cell Line, Tumor; Chromones; Cobalt; Dimethyl Sulfoxide; Gene Expression; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Male; Morpholines; Neoplasm Invasiveness; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Prostatic Neoplasms; RNA, Antisense; Signal Transduction; Sirolimus; Transcription Factors; Up-Regulation

Topics: Androgen Receptor Antagonists; Androgens; Antineoplastic Agents; Biomarkers, Tumor; Drug Resistance, Neoplasm; Gefitinib; Gene Expression Regulation, Neoplastic; Genes, Tumor Suppressor; Humans; Male; Phosphoric Monoester Hydrolases; Predictive Value of Tests; Prostate-Specific Antigen; Prostatic Neoplasms; Protein Kinase Inhibitors; Protein Kinases; PTEN Phosphohydrolase; Quinazolines; Receptors, Androgen; Sirolimus; TOR Serine-Threonine Kinases; Tumor Suppressor Proteins; Up-Regulation

In a previous report, we showed that increased activation of Akt, a downstream effector of phosphoinositide 3-kinase (PI3K) together with decreased activation of extracellular-signal-regulated kinase (ERK), a member of the mitogen-activated protein kinase (MAPK) family, predicted poor clinical outcome in prostate cancer (Kreisberg et al. 2004 Cancer Research 64 5232-5236). We now show that Akt activation, but not ERK activation, is correlated with proliferation in human prostate tumors as estimated by the expression of the cell proliferation antigen Ki67. We verified these results in vitro, using the androgen-dependent prostate cancer cell line LNCaP and its androgen-independent clone C4-2 as models of prostate cancer of good and poor clinical outcome, respectively. C4-2 cells expressed higher Akt activation, lower ERK activation and increased proliferation compared with LNCaP cells, similar to cases of poor clinical outcome. The PI3K inhibitor LY294002, but not the MAPK/ERK kinase inhibitor PD98059, induced growth arrest in both cell lines. Transient transfection with constitutively active Akt increased proliferation while dominant negative Akt decreased it, thus showing that Akt plays an important role in prostate cancer proliferation. Akt regulates the expression and activation of the androgen receptor. Androgen receptor inhibition with Casodex induced growth arrest in LNCaP cells, but not in C4-2 cells. Another PI3K downstream effector, p70 S6 kinase, requires prior phosphorylation by mammalian target of rapamycin (mTOR) for complete activation. Activation of p70 S6 kinase was higher in C4-2 compared with LNCaP cells. Rapamycin, an mTOR inhibitor, had a growth-inhibitory effect in C4-2 cells, but not in LNCaP cells. Our data suggest a shift from a Casodex-sensitive proliferation pathway in LNCaP cells to a rapamycin-sensitive pathway in C4-2 cells.

Topics: Androgen Antagonists; Androgen Receptor Antagonists; Androgens; Anilides; Antibiotics, Antineoplastic; Cell Proliferation; Enzyme Inhibitors; Humans; Ki-67 Antigen; Male; Mitogen-Activated Protein Kinases; Neoplasms, Hormone-Dependent; Nitriles; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; Prostatic Hyperplasia; Prostatic Intraepithelial Neoplasia; Prostatic Neoplasms; Protein Kinases; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Receptors, Androgen; Ribosomal Protein S6 Kinases, 70-kDa; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Tosyl Compounds; Tumor Cells, Cultured

Selective inhibition of repopulation of surviving tumor cells between courses of chemotherapy might improve the outcome of treatment. A potential target for inhibiting repopulation is the mammalian target of rapamycin pathway; PTEN-negative tumor cells are particularly sensitive to inhibition of this pathway. Here we study the rapamycin analogue CCI-779, alone or with chemotherapy, as an inhibitor of proliferation of the human prostate cancer cell lines PC-3 and DU145. The PTEN and phospho-Akt/PKB status and the effect of CCI-779 on phosphorylation of ribosomal protein S6 were evaluated by immunostaining and/or Western blotting. Expression of phospho-Akt/PKB in PTEN mutant PC-3 cells and xenografts was higher than in PTEN wild-type DU145 cells. Phosphorylation of S6 was inhibited by CCI-779 in both cell lines. Cultured cells were treated weekly with mitoxantrone or docetaxel for two cycles, and CCI-779 or vehicle was given between courses. Growth and clonogenic survival of both cell lines were inhibited in a dose-dependent manner by CCI-779, but there were minimal effects when CCI-779 was given between courses of chemotherapy. CCI-779 inhibited the growth of xenografts derived from both cell lines with greater effects against PC-3 than DU145 tumors. CCI-779 caused mild myelosuppression. The activity of mitoxantrone or docetaxel was limited, but CCI-779 given between courses of chemotherapy increased growth delay of PC-3 xenografts. Our results suggest that repopulation of PTEN-negative cancer cells between courses of chemotherapy might be inhibited by CCI-779.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Cell Growth Processes; Cell Line, Tumor; Cell Proliferation; Docetaxel; Drug Synergism; Humans; Male; Mice; Mice, Inbred BALB C; Mice, Nude; Mitoxantrone; Phosphoric Monoester Hydrolases; Phosphorylation; Prostatic Neoplasms; Protein Kinase Inhibitors; Protein Kinases; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; PTEN Phosphohydrolase; Ribosomal Protein S6; Sirolimus; Taxoids; TOR Serine-Threonine Kinases; Tumor Suppressor Proteins; Xenograft Model Antitumor Assays

Recent analyses indicate that the expression of the Pim-1 protein kinase is elevated in biopsies of prostate tumors. To identify the mechanism by which the Pim kinases may affect the growth of prostate tumors, we expressed Pim-1, Pim-2, or a kinase-dead Pim-2 protein in human PC3 prostate cancer cells. On implantation of the transfectants in nude mice, the growth of the cells expressing Pim-1 or Pim-2 was significantly faster than the growth of the control cells transfected with the neomycin-resistant gene or the kinase-dead Pim-2 protein. When grown in medium, the doubling time of the Pim-1 and Pim-2 transfectants was faster (0.75 days) than that of the control cells (1.28 days). We, therefore, examined the ability of Pim to control the phosphorylation of proteins that regulate protein synthesis. On growth factor starvation or rapamycin treatment, the Pim-1 and Pim-2 transfectants maintained their ability to phosphorylate 4E-BP1 and S6 kinase, although this phosphorylation did not occur in the control-transfected PC3 cells. We have found that the cellular levels of c-Myc were elevated in the Pim-1 and Pim-2 transfectants under these conditions. The Pim-1 and Pim-2 transfectants have lower levels of serine/threonine protein phosphatase 2A (PP2A) activity and the alpha- and beta-subunit B56gamma of the PP2A phosphatase do not coimmunoprecipitate in these cells. Thus, the effects of Pim on PP2A activity may mediate the levels of c-Myc and the phosphorylation of proteins needed for increased protein synthesis. Both of these changes could have a significant impact on tumor growth.

Topics: Adaptor Proteins, Signal Transducing; Animals; Blotting, Western; Carrier Proteins; Cell Cycle; Cell Cycle Proteins; Cell Line, Tumor; Cell Nucleus; Cell Proliferation; Eukaryotic Initiation Factors; Humans; Immunoprecipitation; Male; Mice; Mice, Inbred BALB C; Mice, Nude; Neoplasm Transplantation; Phosphoprotein Phosphatases; Phosphoproteins; Phosphoric Monoester Hydrolases; Phosphorylation; Plasmids; Prostatic Neoplasms; Protein Phosphatase 2; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-myc; Proto-Oncogene Proteins c-pim-1; Reverse Transcriptase Polymerase Chain Reaction; Ribosomal Protein S6 Kinases; RNA Interference; Signal Transduction; Sirolimus; Time Factors; Transfection

Arsenite is ubiquitous in the environment, particularly in the form of contaminated water. Although this metal is a known human carcinogen, its exact mechanism of action remains unclear. P70S6K1 phosphorylates the ribosomal 40S protein leading to increased protein translation, and is an important regulator of cell growth and proliferation. Hypoxia inducible factor-1 (HIF-1) is a basic helix-loop-helix transcription factor composed of two subunits, HIF-1alpha and HIF-1beta. HIF-1 activates the transcription of a number of genes that mediate angiogenesis and tumor formation. In this study we demonstrated that arsenite treatment increased levels of p70S6K1 phosphorylation and p70S6K1 activity in a PI3K and mTOR sensitive manner. We have also shown that arsenite specifically induces HIF-1alpha, but not HIF-1beta, protein levels in prostate cancer cells in a mTOR-dependent manner.

Topics: Arsenites; Aryl Hydrocarbon Receptor Nuclear Translocator; Cell Line, Tumor; DNA-Binding Proteins; Enzyme Activation; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Male; Phosphatidylinositol 3-Kinases; Phosphorylation; Prostatic Neoplasms; Protein Kinases; Receptors, Aryl Hydrocarbon; Ribosomal Protein S6 Kinases, 70-kDa; Signal Transduction; Sirolimus; Teratogens; TOR Serine-Threonine Kinases; Transcription Factors

Loss of PTEN function leads to activation of phosphoinositide 3-kinase (PI3K) signaling and Akt. Clinical trials are now testing whether mammalian target of rapamycin (mTOR) inhibition is useful in treating PTEN-null cancers. Here, we report that mTOR inhibition induced apoptosis of epithelial cells and the complete reversal of a neoplastic phenotype in the prostate of mice expressing human AKT1 in the ventral prostate. Induction of cell death required the mitochondrial pathway, as prostate-specific coexpression of BCL2 blocked apoptosis. Thus, there is an mTOR-dependent survival signal required downstream of Akt. Bcl2 expression, however, only partially restored intraluminal cell growth in the setting of mTOR inhibition. Expression profiling showed that Hif-1 alpha targets, including genes encoding most glycolytic enzymes, constituted the dominant transcriptional response to AKT activation and mTOR inhibition. These data suggest that the expansion of AKT-driven prostate epithelial cells requires mTOR-dependent survival signaling and activation of HIF-1 alpha, and that clinical resistance to mTOR inhibitors may emerge through BCL2 expression and/or upregulation of HIF-1 alpha activity.

Topics: Animals; Apoptosis; Cell Survival; Epithelial Cells; Everolimus; Gene Expression Profiling; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Immunosuppressive Agents; In Situ Nick-End Labeling; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Phenotype; Placebos; Prostate; Prostatic Neoplasms; Protein Kinase Inhibitors; Protein Kinases; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-bcl-2; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Transcription Factors

Serum transforming growth factor (TGF)-beta1 is elevated in patients with metatatic prostate cancer. Although growth inhibitory in normal prostate epithelial cells, cancer cells are often resistant to TGF-beta1. The role of phosphatidylinositol 3-kinase (PI3K)/AKT and mammalian target of rapamycin (mTOR) signaling in TGF-beta1 resistance was studied in prostate cancer cell lines.. PC3 and LNCaP human prostate cancer cell lines were exposed for 72 hours to rapamycin (mTOR inhibition), LY294002 (PI3K/AKT inhibition) and TGF-beta1 in a proliferation (WST-1) assay. A TGF-beta1 receptor II, stably transfected LNCaP cell line was used (LNCaP-RII). TGF-beta1/SMAD (Sma and MAD [mothers-against-decapentaplegic]homologue) signaling was assessed using the pGL3-SBE4-luc (SBE4) reporter plasmid. Immunoblotting and immunocytochemistry were applied to evaluate phosphorylated Smad and E-cadherin expression in relation to mTOR inhibition and TGF-beta1 exposure.. In PC3 and LNCaP-RII cells mTOR and PI3K/AKT inhibition caused TGF-beta1 to become inhibitory for growth. The synergistic effect was associated with the increased expression of phosphorylated Smad and induction of SBE4 reporter plasmid expression. E-cadherin in PC3 cells increased upon mTOR inhibition and TGF-beta1 exposure.. Inhibition of growth signaling through PI3K/AKT/mTOR renders prostate cancer cells sensitive to TGF-beta1 induced growth inhibition.

Topics: Antibiotics, Antineoplastic; Cell Division; Cell Line, Tumor; Chromones; Drug Interactions; Flutamide; Humans; Male; Morpholines; Phosphoinositide-3 Kinase Inhibitors; Prostatic Neoplasms; Signal Transduction; Sirolimus; Stimulation, Chemical; Transforming Growth Factor beta; Tumor Cells, Cultured

Rapamycin inhibits the FK506-binding protein 12 (FKBP12)/mammalian target of rapamycin (mTOR) complex and causes cell cycle arrest in G1. The precise mechanism of growth inhibition by rapamycin is only partly understood. Rapamycin led to growth inhibition in the human prostate cancer cell lines LNCaP and PC3 cells after 72 h, ID50: 93 and 50 nM, respectively. Filter cDNA array analysis showed down-regulation by more than 0.75x by rapamycin in PC3 cells and LNCaP cells of the following genes: follistatin, eukaryotic initiation factor-4E (eIF4E), glucose-6-phosphate dehydrogenase (GAPDH), lactate dehydrogenase (LDH)-A, ATP synthase, heat shock protein (HSP)-1. Upregulation by more than 1.5x was found for: bone morphogenetic protein (BMP)-4, FKBP12, carcinoma embryonic antigen (CEA) precursor, eukaryotic initiation factor (eIF)-3 p36 subunit, latent transforming growth factor (TGF) beta binding protein (LTBP)1. Rapamycin induced BMP4 and reduced follistatin expression in PC3 cells. This resulted in a dose-dependent nuclear expression of Smad4 and activated the SBE4 Smad-reporter, indicating activation of TGFbeta/BMP signaling. Combining rapamycin with PI3K inhibition (LY294002) increased growth inhibition. These findings illustrate that Smad signaling plays a role in the anticancer effects of rapamycin and show that combination with PI3K inhibition improves growth inhibition.

Topics: Antibiotics, Antineoplastic; Bone Morphogenetic Protein 4; Bone Morphogenetic Proteins; Cell Division; Cell Line, Tumor; DNA-Binding Proteins; Dose-Response Relationship, Drug; Follistatin; Humans; Male; Prostatic Neoplasms; Signal Transduction; Sirolimus; Smad Proteins; Trans-Activators

Phosphatase and tensin homologue deleted from chromosome 10 (PTEN) is a lipid phosphatase with putative tumor suppressing abilities, which is frequently mutated in prostate cancer. Loss of PTEN leads to constitutive activation of the phosphatidylinositol 3'-kinase/serine-threonine kinase (Akt) signal transduction pathway and has been associated with resistance to chemotherapy. This study aimed to determine the effects of PTEN status and treatment with rapamycin, an inhibitor of mTOR, in the response of prostate cancer cell lines to doxorubicin. The DU-145 PTEN-positive cell line was significantly more susceptible to the antiproliferative effects of doxorubicin as compared with the PTEN-negative PC-3 cell line. Transfection of PTEN into the PC3 cells decreased the activation of Akt and the downstream mTOR-regulated 70-kDa S6 (p70(s6k)) kinase and reversed the resistance to doxorubicin in these cells, indicating that changes in PTEN status/Akt activation modulate the cellular response to doxorubicin. Treatment of PC-3 PTEN-negative cells with rapamycin inhibited 70-kDa S6 kinase and increased the proliferative response of these cells to doxorubicin, so that it was comparable with the responses of PTEN-positive DU-145 cells and the PC-3-transfected cells. Furthermore, treatment of mice bearing the PTEN-negative PC-3 prostate cancer xenografts with CCI-779, an ester of rapamycin in clinical development combined with doxorubicin, inhibited the growth of the doxorubicin-resistant PC-3 tumors confirming the observations in vitro. Thus, rapamycin and CCI-779, by interacting with downstream intermediates in the phosphatidylinositol 3'-kinase/Akt signaling pathway, reverse the resistance to doxorubicin conferred by PTEN mutation/Akt activation. These results provide the rationale to explore in clinical trials whether these agents increase the response to chemotherapy of patients with PTEN-negative/Akt active cancers.

Topics: Animals; Antibiotics, Antineoplastic; Doxorubicin; Drug Resistance, Neoplasm; Humans; Male; Mice; Mice, Nude; Phosphoric Monoester Hydrolases; Prostatic Neoplasms; Protein Kinase Inhibitors; Protein Kinases; PTEN Phosphohydrolase; Sirolimus; TOR Serine-Threonine Kinases; Transfection; Tumor Cells, Cultured; Tumor Suppressor Proteins; Xenograft Model Antitumor Assays

Androgen deprivation therapy for advanced prostate cancer is often effective, but not curative. Molecular pathways mediating the therapeutic response and those contributing to the subsequent hormone-refractory cell growth remain poorly understood. Here, cDNA microarray analysis of human CWR22 prostate cancer xenografts during the course of androgen deprivation therapy revealed distinct global gene expression profiles in primary, regressing and recurrent tumors. Elucidation of the genes involved in the transition between these states implicated specific molecular mechanisms in therapy failure and tumor progression. First, we identified a set of androgen-responsive genes whose expression decreased during the therapy response, but was then systematically restored in the recurrent tumors. In addition, altered expression of genes that encode known targets of rapamycin or that converge on the PI3K/AKT/FRAP pathway was observed in the recurrent tumors. Further suggestion for the involvement of these genes in hormone-refractory prostate cancer came from the observation that cells established from the recurrent xenografts were strongly inhibited in vitro by rapamycin. The results of this functional genomic analysis suggest that the combined effect of re-expression of androgen-responsive genes as well as the activation of rapamycin-sensitive signaling may drive prostate cancer progression, and contribute to the failure of androgen-deprivation therapy.

Topics: Algorithms; Animals; Antibiotics, Antineoplastic; Cell Survival; DNA, Complementary; Dose-Response Relationship, Drug; Drug Resistance, Neoplasm; Humans; Male; Mice; Mice, Nude; Models, Biological; Neoplasm Transplantation; Oligonucleotide Array Sequence Analysis; Prostatic Neoplasms; RNA, Messenger; Signal Transduction; Sirolimus; Software; Time Factors; Tumor Cells, Cultured