sirolimus and Carcinoid-Tumor

"Carcinoids" are mostly slow-growing neuroendocrine neoplasms (NENs) with low proliferative activity. A wide range of therapeutic options with variable efficacy exist, including locoregional ablative strategies. Thereafter, some patients may not require medical therapy for years depending on the rate of progression or recurrence. However, the majority of patients require systemic treatment and therein lies the dilemma, since no antiproliferative agent is currently approved for carcinoids. Somatostatin analogs (SSAs), and to a lesser extent interferon-alpha, are standard therapy for carcinoids associated with the carcinoid syndrome. These drugs have some antiproliferative efficacy. SSAs rarely lead to tumor remission but may modestly prolong time to tumor progression. Chemotherapy is of limited value in carcinoids with low proliferation indices but may be useful in higher grade tumors. Peptide receptor-targeted radionuclide therapy may be of benefit and is mostly used after medical therapies fail. However, it is considered an investigational modality. More recently, targeted drugs such as mammalian target of rapamycin (mTOR) inhibitors and anti-angiogenics have been investigated. Objective remissions are rare. Their value remains to be rigorously elucidated. Increased efficacy requires a better understanding of the underlying tumor biology and identification of molecular pathological criteria to allow appropriate preselection of candidates for targeted therapies.

Topics: Antineoplastic Agents; Carcinoid Tumor; Clinical Trials as Topic; Everolimus; Humans; Interferon-alpha; Octreotide; Sirolimus; Somatostatin; Treatment Outcome

Well-differentiated neuroendocrine tumors (NETs) can be subdivided into carcinoid and pancreatic NETs (panNETs). Recently, two therapies have been FDA approved for progressive well-differentiated pancreatic NETs but have not been submitted for use in carcinoid tumors (Yao, Shah, Ito, et al. N Engl J Med 364:514-23, 2011••; Raymond, Dahan, Raoul, et al. N Engl J Med 364:501-13, 2011••). The first is sunitinib (Sutent(®), Pfizer, Inc.), an orally administered, multitargeted receptor kinase inhibitor. The second targeted agent is everolimus (Afinitor(®), Novartis Pharmaceuticals), a mammalian target of rapamycin (mTOR) inhibitor (Yao, Shah, Ito, et al. N Engl J Med 364:514-23, 2011••). Both agents demonstrated improved progression-free survival but can also result in non-trivial toxicities and therefore, should only be considered in patients with progressing or symptomatic pancreatic NET. This review will discuss "new" NET therapies and provides an overview of liver directed and "older" cytotoxic treatment options. We also briefly outline "what's different" by describing a recent genetics report identifying genetic mutations in panNETs. Such a discovery could potentially be used to stratify treatment and such studies are currently being investigated.

Topics: Angiogenesis Inhibitors; Antineoplastic Agents; Carcinoid Tumor; Combined Modality Therapy; Dacarbazine; Embolization, Therapeutic; Everolimus; Humans; Immunosuppressive Agents; Indoles; Neuroendocrine Tumors; Pancreatic Neoplasms; Pyrroles; Sirolimus; Streptozocin; Sunitinib; Temozolomide; TOR Serine-Threonine Kinases; Vascular Endothelial Growth Factors; Yttrium Radioisotopes

Neuroendocrine neoplasms (NEN) are a heterogeneous group of tumors, whose incidence and prevalence are increasing. The clinical behavior of NEN is variable, ranging from well-differentiated slow growing tumors to highly aggressive poorly differentiated neuroendocrine carcinomas. The term carcinoid is commonly used for the more benign variants of these neoplasms. Most frequently, carcinoids have their origin in the small intestine, followed by in the lung and other sites. Some of these tumors are associated with the carcinoid syndrome. The use of somatostatin analogs has revolutionized the clinical management of patients with carcinoids. However, although symptomatic relief and stabilization of tumor growth for various periods of time are observed in many patients treated with somatostatin analogs, tumor regression is rare. Currently, there is no other powerful antiproliferative agent available for carcinoids. Mammalian target of rapamycin (mTOR), a main protein kinase in the phosphoinositide 3-kinase/Akt/p70S6K signaling pathway, is an important intracellular mediator involved in multiple cellular functions including proliferation, differentiation, apoptosis, tumorigenesis, and angiogenesis. Alterations of the normal activity of mTOR and of mTOR-related kinases in this pathway have been found in a diversity of human tumors, including NEN; therefore, mTOR pathway represents an attractive target for new anticancer therapies. While mTOR inhibitors, such as everolimus, are established therapy in pancreatic NEN, results from recent clinical trials indicate that mTOR inhibitors may be also of value in the management of carcinoids. However, further clinical trials will have to confirm efficacy and elucidate, in which subtypes and in which setting, these drugs might be most usefully applied.

Topics: Antineoplastic Agents; Carcinoid Tumor; Cell Differentiation; Everolimus; Gene Expression Regulation, Neoplastic; Humans; Medical Oncology; Models, Biological; Neuroendocrine Tumors; Phosphatidylinositol 3-Kinases; Signal Transduction; Sirolimus; Somatostatin; TOR Serine-Threonine Kinases; Treatment Outcome

Everolimus is a valid therapeutic option for neuroendocrine tumors (NETs); however, data in a real-world setting outside regulatory trials are sparse. The aim of this study was to determine everolimus tolerability and efficacy, in relation to previous treatments, in a compassionate use program. A total of 169 patients with advanced progressive NETs treated with everolimus were enrolled, including 85 with pancreatic NETs (pNETs) and 84 with nonpancreatic NETs (non-pNETs). Previous treatments included somatostatin analogs (92.9%), peptide receptor radionuclide therapy (PRRT; 50.3%), chemotherapy (49.7%), and PRRT and chemotherapy (22.8%). Overall, 85.2% of patients experienced adverse events (AEs), which were severe (grade 3-4) in 46.1%. The most frequent severe AEs were pneumonitis (8.3%), thrombocytopenia (7.7%), anemia (5.3%), and renal failure (3.5%). In patients previously treated with PRRT and chemotherapy, a 12-fold increased risk for severe toxicity was observed, with grade 3-4 AEs reported in 86.8% (vs. 34.3% in other patients). In addition, 63.3% of patients required temporarily everolimus discontinuation due to toxicity. Overall, 27.8% of patients died during a median follow-up of 12 months. Median progression-free survival (PFS) and overall survival (OS) were 12 months and 32 months, respectively. Similar disease control rates, PFS, and OS were reported in pNETs and non-pNETs. In the real-world setting, everolimus is safe and effective for the treatment of NETs of different origins. Higher severe toxicity occurred in patients previously treated with systemic chemotherapy and PRRT. This finding prompts caution when using this drug in pretreated patients and raises the issue of planning for everolimus before PRRT and chemotherapy in the therapeutic algorithm for advanced NETs.

Topics: Aged; Carcinoid Tumor; Compassionate Use Trials; Disease-Free Survival; Drug-Related Side Effects and Adverse Reactions; Everolimus; Female; Humans; Male; Middle Aged; Neoplasm Staging; Neuroendocrine Tumors; Octreotide; Pancreatic Neoplasms; Sirolimus

Everolimus, an oral inhibitor of the mammalian target of rapamycin (mTOR), has shown antitumour activity in patients with advanced pancreatic neuroendocrine tumours. We aimed to assess the combination of everolimus plus octreotide long-acting repeatable (LAR) in patients with low-grade or intermediate-grade neuroendocrine tumours (carcinoid).. We did a randomised, double-blind, placebo-controlled, phase 3 study comparing 10 mg per day oral everolimus with placebo, both in conjunction with 30 mg intramuscular octreotide LAR every 28 days. Randomisation was by interactive voice response systems. Participants were aged 18 years or older, with low-grade or intermediate-grade advanced (unresectable locally advanced or distant metastatic) neuroendocrine tumours, and disease progression established by radiological assessment within the past 12 months. Our primary endpoint was progression-free survival. Adjusted for two interim analyses, the prespecified boundary at final analysis was p≤0·0246. This study is registered at ClinicalTrials.gov, number NCT00412061.. 429 individuals were randomly assigned to study groups; 357 participants discontinued study treatment and one was lost to follow-up. Median progression-free survival by central review was 16·4 (95% CI 13·7-21·2) months in the everolimus plus octreotide LAR group and 11·3 (8·4-14·6) months in the placebo plus octreotide LAR group (hazard ratio 0·77, 95% CI 0·59-1·00; one-sided log-rank test p=0·026). Drug-related adverse events (everolimus plus octreotide LAR vs placebo plus octreotide LAR) were mostly grade 1 or 2, and adverse events of all grades included stomatitis (62%vs 14%), rash (37%vs 12%), fatigue (31%vs 23%), and diarrhoea (27%vs 16%).. Everolimus plus octreotide LAR, compared with placebo plus octreotide LAR, improved progression-free survival in patients with advanced neuroendocrine tumours associated with carcinoid syndrome.. Novartis Pharmaceuticals.

Topics: Adult; Aged; Aged, 80 and over; Antineoplastic Agents, Hormonal; Carcinoid Tumor; Delayed-Action Preparations; Disease Progression; Double-Blind Method; Drug Therapy, Combination; Everolimus; Female; Humans; Immunosuppressive Agents; Male; Malignant Carcinoid Syndrome; Middle Aged; Octreotide; Sirolimus; Young Adult

Evaluate the activity of everolimus (RAD001) in combination with octreotide long-acting repeatable (LAR) in patients with advanced low- to intermediate-grade neuroendocrine tumors.. Treatment consisted of RAD001 5 mg/d (30 patients) or 10 mg/d (30 patients) and octreotide LAR 30 mg every 28 days. Thirty carcinoid and 30 islet cell patients were enrolled.. Intent-to-treat response rate was 20%. Per protocol, there were 13 with partial responses (22%), 42 with stable disease (SD; 70%), and five patients with progressive disease (8%). Overall median progression-free survival (PFS) was 60 weeks. Median PFS for patients with known SD at entry was longer than for those who had progressive disease (74 v 50 weeks; P < .01). Median overall survival has not been reached. One-, 2-, and 3-year survival rates were 83%, 81%, and 78%, respectively. Among 37 patients with elevated chromogranin A, 26 (70%) achieved normalization or more than 50% reduction. Most common toxicity was mild aphthous ulceration. Grade 3/4 toxicities occurring in >or= 10% of patients included hypophosphatemia (11%), fatigue (11%), and diarrhea (11%). Treatment was associated with a dose-dependent rise in lactate dehydrogenase (LDH). Those with lower than 109 U/L rise in LDH at week 4 had shorter PFS (38 v 69 weeks; P = .01). Treatment was also associated with a decrease in proliferation marker Ki-67 among patients who underwent optional paired pre- and post-treatment biopsy (P = .04).. RAD001 at 5 or 10 mg/d was well tolerated in combination with octreotide LAR, with promising antitumor activity. Confirmatory studies are ongoing.

Topics: Adult; Aged; Antineoplastic Combined Chemotherapy Protocols; Carcinoid Tumor; Carcinoma, Islet Cell; Delayed-Action Preparations; Everolimus; Female; Humans; Male; Middle Aged; Neuroendocrine Tumors; Octreotide; Pancreatic Neoplasms; Sirolimus

Standard cytotoxic treatments for neuroendocrine tumours have been associated with limited activity and remarkable toxicity. A phase II study was designed to evaluate the efficacy, safety and pharmacodynamics of temsirolimus in patients with advanced neuroendocrine carcinoma (NEC). Thirty-seven patients with advanced progressive NEC received intravenous weekly doses of 25 mg of temsirolimus. Patients were evaluated for tumour response, time to progression (TTP), overall survival (OS) and adverse events (AE). Twenty-two archival specimens, as well as 13 paired tumour biopsies obtained pretreatment and after 2 weeks of temsirolimus were assessed for potential predictive and correlative markers. The intent-to-treat response rate was 5.6% (95% CI 0.6-18.7%), median TTP 6 months and 1-year OS rate 71.5%. The most frequent drug-related AE of all grades as percentage of patients were: fatigue (78%), hyperglycaemia (69%) and rash/desquamation (64%). Temsirolimus effectively inhibited the phosphorylation of S6 (P=0.02). Higher baseline levels of pmTOR (phosphorylated mammalian target of rapamycin) (P=0.01) predicted for a better response. Increases in pAKT (P=0.041) and decreases in pmTOR (P=0.048) after treatment were associated with an increased TTP. Temsirolimus appears to have little activity and does not warrant further single-agent evaluation in advanced NEC. Pharmacodynamic analysis revealed effective mTOR pathway downregulation.

Topics: Adult; Aged; Antineoplastic Agents; Carcinoid Tumor; Carcinoma, Neuroendocrine; Disease Progression; Exanthema; Fatigue; Female; Follow-Up Studies; Humans; Hyperglycemia; Infusions, Intravenous; Male; Middle Aged; Pancreatic Neoplasms; Phosphorylation; Protein Kinases; Proto-Oncogene Proteins c-akt; Ribosomal Protein S6; Sirolimus; Survival Analysis; TOR Serine-Threonine Kinases; Treatment Outcome

Topics: Antibiotics, Antineoplastic; Carcinoid Tumor; Female; Humans; Lung; Lung Neoplasms; Middle Aged; Neuroendocrine Cells; Sirolimus; Syndrome

Neuroendocrine tumors (NETs) are highly vascularized neoplasms characterized by rising incidence. Moreover, the neuroendocrine cells were shown to express vascular endothelial growth factor (VEGF) and VEGF receptors. Therefore, angiomodulators could be potentially a new group of drugs enhancing still unsatisfactory effectiveness of NET therapy. The aim of this study was to assess the direct influence of angiomodulators: VEGF and five endogenous and exogenous antiangiogenic compounds (endostatin, interferon alpha [IFNα], rapamycin, JV1-36, semaxinib [SU5416]) on the growth of two NET cell lines: lung carcinoid H727 cell line and medullary thyroid cancer TT cell line in vitro. IFNα and rapamycin induced the inhibitory effect on H727 and TT cell viability and proliferation, increasing apoptosis and arresting the cell cycle. Also semaxinib (10(-5)M) inhibited proliferation of both cell lines. VEGF and endostatin did not influence the growth of H727 and TT cells. The inhibitory effect of IFNα, rapamycin and semaxinib on carcinoid and medullary thyroid cancer growth was revealed in our in vitro study, although some other antiangiogenic agents did not directly influence H727 and TT cell growth. Thus, IFNα and mTOR inhibitors as multidirectionally acting drugs with antiangiogenic effect could be potentially efficient in treatment of neuroendocrine tumors and are worth further studies.

Topics: Angiogenesis Inhibitors; Apoptosis; Calcitonin; Carcinoid Tumor; Carcinoma, Neuroendocrine; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Cell Survival; Humans; Interferon-alpha; Lung Neoplasms; Sirolimus; Thyroid Neoplasms

As progression-free survival (PFS) has become increasingly used as the primary endpoint in oncology phase III trials, the U.S. Food and Drug Administration (FDA) has generally required a complete-case blinded independent central review (BICR) of PFS to assess and reduce potential bias in the investigator or local site evaluation. However, recent publications and FDA analyses have shown a high correlation between local site evaluation and BICR assessments of the PFS treatment effect, which questions whether complete-case BICR is necessary. One potential alternative is to use BICR as an audit tool to detect evaluation bias in the local site evaluation. In this article, the performance characteristics of two audit methods proposed in the literature are evaluated on 26 prospective, randomized phase III registration trials in nonhematologic malignancies. The results support that a BICR audit to assess potential bias in the local site evaluation is a feasible approach. However, implementation and logistical challenges need further consideration and discussion.

Topics: Algorithms; Bias; Carcinoid Tumor; Clinical Audit; Clinical Trials, Phase III as Topic; Disease Progression; Disease-Free Survival; Endpoint Determination; Everolimus; Humans; Immunosuppressive Agents; Neoplasms; Outcome Assessment, Health Care; Randomized Controlled Trials as Topic; Reproducibility of Results; Sarcoma; Sirolimus

Bronchial carcinoids (BCs) are rare neuroendocrine tumors that are still orphans of medical treatment. Human BC primary cultures may display resistance to everolimus, an inhibitor of the mammalian target of rapamycin (mTOR), in terms of cell viability reduction. Our aim was to assess whether the novel dual phosphatidylinositol 3-kinase (PI3K)/mTOR inhibitor NVP-BEZ235 is effective in everolimus-resistant human BC tissues and cell lines. In addition, we searched for possible markers of the efficacy of mTOR inhibitors that may help in identifying the patients who may benefit from treatment with mTOR inhibitors, sparing them from ineffective therapy. We found that NVP-BEZ235 is twice as potent as everolimus in reducing cell viability and activating apoptosis in human BC tissues that display sensitivity to mTOR inhibitors, but is not effective in everolimus-resistant BC tissues and cell lines that bypass cyclin D1 downregulation and escape G0/G1 blockade. Rebound AKT activation was not observed in response to treatment with either mTOR inhibitor in the 'resistant' BC cells. In addition to total mTOR levels, putative markers of the sensitivity of BCs to mTOR inhibitors are represented by AKT, p70S6K (RPS6KB2), and ERK1/2 (MAPK3/1) protein levels. Finally, we validated these markers in an independent BC group. These data indicate that the dual PI3K/mTOR inhibitor NVP-BEZ235 is more potent than everolimus in reducing the proliferation of human BC cells. 'Resistant' cells display lower levels of mTOR, p70S6K, AKT, and ERK1/2, indicating that these proteins may be useful as predictive markers of resistance to mTOR and PI3K/mTOR inhibitors in human BCs.

Topics: Adult; Aged; Antineoplastic Agents; Carcinoid Tumor; Cell Line, Tumor; Cell Survival; Drug Resistance, Neoplasm; Everolimus; Female; Humans; Imidazoles; Lung Neoplasms; Male; Middle Aged; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Quinolines; Ribosomal Protein S6 Kinases, 70-kDa; Sirolimus; TOR Serine-Threonine Kinases; Young Adult

Although targeted therapy, including inhibitors of mammalian target of rapamycin (mTOR) and vascular endothelial growth factor, being developed for carcinoids arised from the gastrointestinal tract, treatment for locally advanced or metastatic bronchial carcinoids (BCs) remains lacking. Traditional cytotoxic chemotherapy offers essentially minimal benefit to this largely under-characterized tumor. In the September issue of Endocrine-Related Cancer, Zatelli et al. reported an anti-proliferative effect of mTOR inhibitor, everolimus, in cultured primary BC tumor cells by attenuation of IGF signaling pathway. This effect is more significant in aggressive tumors that carry higher levels of mTOR, and is consistent with the therapeutic benefit of everolimus for patients with BC observed in our phase II and III clinical trials. Although adding somatostatin analog to mTOR inhibitor did not provide a synergistic anti-tumor effect, development of rational combinations is highly warranted to further improve the outcome for patients with neuroendocrine tumors.

Topics: Antineoplastic Agents; Bronchial Neoplasms; Carcinoid Tumor; Disease-Free Survival; Everolimus; Humans; Molecular Targeted Therapy; Sirolimus; TOR Serine-Threonine Kinases

Metastatic gastrointestinal neuroendocrine tumors (NETs) frequently are refractory to chemotherapy. Chemoresistance in various malignancies has been attributed to cancer stem cells (CSCs). We sought to identify gastrointestinal neuroendocrine CSCs (N-CSCs) in surgical specimens and a NET cell line and to characterize novel N-CSC therapeutic targets.. Human gastrointestinal NETs were evaluated for CSCs using the Aldefluor (Stemcell Technologies, Vancouver, Canada) assay. An in vitro, sphere-forming assay was performed on primary NET cells. CNDT2.5, a human midgut carcinoid cell line, was used for in vitro (sphere-formation) and in vivo (tumorigenicity assays) CSC studies. N-CSC protein expression was characterized using Western blotting. In vivo, systemic short interfering RNA administration targeted Src.. By using the Aldefluor assay, aldehyde dehydrogenase-positive (ALDH+) cells comprised 5.8% ± 1.4% (mean ± standard error of the mean) of cells from 19 patient samples. Although many primary cell lines failed to grow, CNDT96 ALDH+ cells formed spheres in anchorage-independent conditions, whereas ALDH- cells did not. CNDT2.5 ALDH+ cells formed spheres, whereas ALDH- cells did not. In vivo, ALDH+ CNDT2.5 cells generated more tumors, with shorter latency than ALDH- or sham-sorted cells. Compared with non-CSCs, ALDH+ cells demonstrated increased expression of activated Src, Erk, Akt, and mammalian target of rapamycin (mTOR). In vivo, anti-Src short interfering RNA treatment of ALDH+ tumors reduced tumor mass by 91%.. CSCs are present in NETs, as shown by in vitro sphere formation and in vivo tumorigenicity assays. Src was activated in N-CSCs and represents a potential therapeutic target in gastrointestinal NETs.

Topics: Aldehyde Dehydrogenase; Carcinogenicity Tests; Carcinoid Tumor; Cell Line, Tumor; Cells, Cultured; CSK Tyrosine-Protein Kinase; Gastrointestinal Neoplasms; Humans; In Vitro Techniques; Neoplastic Stem Cells; Neuroendocrine Tumors; Protein-Tyrosine Kinases; Signal Transduction; Sirolimus; src-Family Kinases

Topics: Antineoplastic Agents, Hormonal; Carcinoid Tumor; Everolimus; Female; Humans; Immunosuppressive Agents; Male; Malignant Carcinoid Syndrome; Octreotide; Sirolimus

Bronchial carcinoids (BCs) are rare tumors originating from endocrine cells dispersed in the respiratory epithelium. It has been previously demonstrated that everolimus, or RAD001, an mTOR inhibitor, has potent antiproliferative effects in human endocrine tumors. Our aim was to evaluate the possible antiproliferative effects of everolimus in human BCs in primary culture. We collected 24 BCs that were dispersed in primary cultures, treated without or with 1 nM-1 muM everolimus, 10 nM SOM230 (pasireotide, a somatostatin receptor multiligand), and/or 50 nM IGF1. Cell viability was evaluated after 48 h, and chromogranin A (CgA) as well as vascular endothelial growth factor (VEGF) secretion was assessed after 8 h incubation. Somatostatin receptors, mTOR, and AKT expression were investigated by quantitative PCR. We found that in 15 cultures (67.5%), everolimus significantly reduced cell viability (by approximately 30%; P<0.05 versus control), inhibited p70S6K activity (-30%), and blocked IGF1 proliferative effects. Everolimus also significantly reduced CgA (by approximately 20%) and VEGF (by approximately 15%) secretion. Cotreatment with SOM230 did not exert additive effects on cell viability and secretory activity. AKT expression was similar in responder and nonresponder tissues, while mTOR expression was significantly higher in the responder group, which was characterized by higher CgA plasma levels and bigger tumors with higher mitotic index and angiogenesis. Our data demonstrate that everolimus reduces VEGF secretion and cell viability in BCs with a mechanism likely involving IGF1 signaling, suggesting that it might represent a possible medical treatment for BCs.

Topics: Adult; Aged; Blotting, Western; Bronchial Neoplasms; Carcinoid Tumor; Cell Line, Tumor; Cell Proliferation; Everolimus; Female; Humans; Immunoenzyme Techniques; Immunosuppressive Agents; Intracellular Signaling Peptides and Proteins; Male; Middle Aged; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins c-akt; Receptors, Somatostatin; Reverse Transcriptase Polymerase Chain Reaction; Ribosomal Protein S6 Kinases, 70-kDa; RNA, Messenger; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Vascular Endothelial Growth Factor A

The mammalian target of rapamycin (mTOR) signaling pathway has emerged as a promising target for cancer therapy. Rapamycin inhibits mTOR activity but induces upstream signaling, leading to Akt activation, potentially limiting antitumor activity. Octreotide, a somatostatin analog, decreases phosphatidylinositol-3-kinase/Akt signaling in some models, and thus theoretically may enhance rapamycin's antitumor activity. The aim of this study was to determine the antitumor activity of rapamycin and octreotide as single agents and in combination in neuroendocrine tumors. In carcinoid cell lines BON-1 and NCI-H727, cell proliferation was significantly inhibited by rapamycin in vitro, although rapamycin treatment did lead to Akt phosphorylation. Octreotide had limited antiproliferative effects alone, and did not demonstrate synergistic or additive interactions with rapamycin. Furthermore, octreotide did not overcome rapamycin-induced Akt phosphorylation. In vivo, rapamycin alone caused significant tumor suppression. Octreotide alone did not inhibit in vivo tumor growth and did not enhance rapamycin-mediated growth inhibition. In conclusion, rapamycin causes significant growth inhibition in carcinoid tumor cell lines in vitro and in vivo, thus mTOR is a promising therapeutic target for neuroendocrine tumors. Octreotide does not enhance the efficacy of rapamycin's antiproliferative effects in the models tested, and does not inhibit rapamycin-mediated feedback activation of Akt. Further study is needed in order to determine whether octreotide or other somatostatin analogs enhance the efficacy of mTOR inhibitors in other models.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Blotting, Western; Carcinoid Tumor; Cell Proliferation; Cells, Cultured; Humans; Male; Mice; Mice, Inbred BALB C; Neuroendocrine Tumors; Octreotide; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; Protein Kinases; Signal Transduction; Sirolimus; Survival Rate; TOR Serine-Threonine Kinases; Tumor Cells, Cultured