dactolisib and Prostatic-Neoplasms--Castration-Resistant

The combination of standard dose abiraterone acetate and BEZ235, a pan-class I PI3K and mTORC1/2 inhibitor, was poorly tolerated in men with progressive mCRPC.Although the clinical development of BEZ235 has been discontinued in prostate cancer, agents that more selectively target PI3K-AKT-mTOR signaling may have a more favorable therapeutic index and should continue to be explored.. Androgen receptor (AR) and phosphatidylinositol-3 kinase (PI3K) signaling are two commonly perturbed pathways in prostate cancer. Preclinical data have shown that the two pathways compensate for each other when one is inhibited, and combined inhibition of AR and PI3K signaling may be a viable strategy to prevent or overcome castration resistance.. This phase I study evaluated the safety and tolerability of abiraterone acetate and prednisone combined with BEZ235, a dual PI3K and mTORC1/2 inhibitor, in men with progressive metastatic castration resistant prostate cancer (mCRPC) who have not received prior chemotherapy.. The combination of standard-dose abiraterone/prednisone with BEZ235 200 mg twice daily was poorly tolerated in patients with mCRPC. The on-target and off-target effects of dual PI3K and mTORC inhibition likely contributed to the unacceptable toxicity profile.

Topics: Abiraterone Acetate; Aged; Antineoplastic Combined Chemotherapy Protocols; Drug-Related Side Effects and Adverse Reactions; Humans; Imidazoles; Male; Middle Aged; Phosphoinositide-3 Kinase Inhibitors; Prostate-Specific Antigen; Prostatic Neoplasms, Castration-Resistant; Quinolines; Receptors, Androgen; Signal Transduction; TOR Serine-Threonine Kinases

The phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt) signalling axis and androgen receptor (AR) pathways exhibit reciprocal feedback regulation in phosphatase and tensin homologue (PTEN)-deficient metastatic castration-resistant prostate cancer (CRPC) in preclinical models. This phase Ib study evaluated the pan-PI3K inhibitor buparlisib (BKM120) and the dual pan-PI3K/ mammalian target of rapamycin (mTOR) inhibitor dactolisib (BEZ235) in combination with abiraterone acetate (AA) in patients with CRPC.. Patients with CRPC who had progressed on AA therapy received escalating doses of either buparlisib or dactolisib, along with fixed doses of AA (1000 mg once daily (qd)) and prednisone (5 mg twice daily (bid)). The primary objective was to define the maximum tolerated dose (MTD) and/or the recommended dose for expansion (RDE) of either buparlisib or dactolisib in combination with AA. Secondary objectives included safety, antitumour activity (Prostate Cancer Working Group 2 (PCWG2) criteria; 30% of prostate-specific antigen (PSA) decline at ≥week 12) and pharmacokinetic (PK) profile.. Based on the assessment of available pharmacokinetics, safety, and efficacy data, no further study is planned for either buparlisib or dactolisib in combination with AA in CRPC.

Topics: Abiraterone Acetate; Aged; Aged, 80 and over; Aminopyridines; Antineoplastic Combined Chemotherapy Protocols; Area Under Curve; Asthenia; Chills; Diarrhea; Fever; Humans; Hyperglycemia; Imidazoles; Kallikreins; Male; Maximum Tolerated Dose; Middle Aged; Morpholines; Prostate-Specific Antigen; Prostatic Neoplasms, Castration-Resistant; Quinolines; Stomatitis; Vomiting

Aberrant activation of several signaling pathways has been implicated in prostate cancer (PCa) progression to castrate-resistant prostate cancer (CRPC). Phosphoinositide-3-kinase/Protein Kinase B/mechanistic Target of Rapamycin (PI3K/AKT/mTOR) and Hedgehog/GLI (Hh/GLI) pathways are major participants in progression to CRPC. In this sense, the current work aims to assess the potential antitumor effects resulting from co-targeting the aforementioned pathways in PC3 cells with Dactolisib as a dual PI3K/mTOR inhibitor and GANT61 as a GLI1 antagonist. Three replica of PC3 cells were assigned for four treatment groups; vehicle control, Dactolisib-treated, GANT61-treated, and combination-treated groups. GLI1 gene expression was determined by quantitative real-time PCR while active caspase-3 was determined colorimetrically. P-AKT, p70 ribosomal s6 protein kinase 1 (pS6K1), cyclin D1, vascular endothelial growth factor 1 (VEGF1), and Microtubule-associated proteins 1A/1B light chain 3 (LC3) protein levels were determined by ELISA technique. GLI1 gene expression was down-regulated as a result of Dactolisib, GANT61, and their combination. Additionally, both drugs significantly reduced p-AKT, pS6K1, cyclin D1, and VEGF1 protein levels. Dactolisib elevated LC3 protein levels and GANT61 augmented Dactolisib effect on LC3. Moreover, only Dactolisib/GANT61combination significantly increased active caspase-3 level. To sum up, Dactolisib/GANT61 combination was shown to be promising in PCa treatment. Further in-vitro and in-vivo studies are warranted to support our findings.

Topics: Caspase 3; Cell Line, Tumor; Cyclin D1; Hedgehog Proteins; Humans; Imidazoles; Male; Phosphatidylinositol 3-Kinases; Prostatic Neoplasms, Castration-Resistant; Proto-Oncogene Proteins c-akt; Pyridines; Pyrimidines; Quinolines; TOR Serine-Threonine Kinases; Vascular Endothelial Growth Factor A; Zinc Finger Protein GLI1

Granulocytic myeloid-derived suppressor cells (Gr-MDSCs) promote immune evasion and resistance to immunotherapeutics in a variety of malignancies. Our previous study showed that dual PI3K/mTOR inhibitor Dactolisib impaired the viability and immunosuppressive function of Gr-MDSCs, and significantly synergized with immune checkpoint blockade (ICB) antibodies targeting PD1 and CTLA4 to eradicate metastatic castration-resistant prostate cancer (CRPC) in a preclinical transgenic mouse model. On the contrary, tyrosine kinase inhibitor Dasatinib diminished tumor-infiltrating T lymphocytes and showed no synergic activity with ICB. The understanding of the distinct effects of Dactolisib and Dasatinib on Gr-MDSCs, T cells and prostate neoplastic cells is inadequate, limiting the clinical translation of the combination immunotherapy. To address this question, we applied Reverse Phase Protein Array (RPPA) to profile 297 proteins and protein phosphorylation sites of Gr-MDSCs, T cells and prostate cancer cells isolated from the CRPC model. We found cell type-specific protein expression patterns and highly selective targets by the two drugs, including preferential inhibition of phospho-4E-BP1 in Gr-MDSCs by Dactolisib and preferential suppression of phospho-Src and phospho-p38 MAPK in T cells. Furthermore, transcriptomic profiling of Gr-MDSCs treated with the two inhibitors revealed downregulation of mitochondrial respiration pathways by Dactolisib but not Dasatinib. Overall, these results provide important mechanistic insight into the efficacious combination of Dactolisib and ICB as well as the detrimental effect of Dasatinib on anti-tumor immunity.

Topics: Animals; CTLA-4 Antigen; Dasatinib; Humans; Imidazoles; Immune Checkpoint Inhibitors; Immunotherapy; Lymphocytes, Tumor-Infiltrating; Male; Mice; Mice, Transgenic; Myeloid-Derived Suppressor Cells; Programmed Cell Death 1 Receptor; Prostate; Prostatic Neoplasms; Prostatic Neoplasms, Castration-Resistant; Protein Kinase Inhibitors; Quinolines; TOR Serine-Threonine Kinases

A significant fraction of patients with advanced prostate cancer treated with androgen deprivation therapy experience relapse with relentless progression to lethal metastatic castration-resistant prostate cancer (mCRPC). Immune checkpoint blockade using antibodies against cytotoxic-T-lymphocyte-associated protein 4 (CTLA4) or programmed cell death 1/programmed cell death 1 ligand 1 (PD1/PD-L1) generates durable therapeutic responses in a significant subset of patients across a variety of cancer types. However, mCRPC showed overwhelming de novo resistance to immune checkpoint blockade, motivating a search for targeted therapies that overcome this resistance. Myeloid-derived suppressor cells (MDSCs) are known to play important roles in tumour immune evasion. The abundance of circulating MDSCs correlates with prostate-specific antigen levels and metastasis in patients with prostate cancer. Mouse models of prostate cancer show that MDSCs (CD11b

Topics: Anilides; Animals; CD8-Positive T-Lymphocytes; Chimera; Cytokines; Disease Models, Animal; Drug Synergism; Female; Humans; Imidazoles; Immunotherapy; Lymphocytes, Tumor-Infiltrating; Male; Mice; Molecular Targeted Therapy; Myeloid-Derived Suppressor Cells; Phosphoinositide-3 Kinase Inhibitors; Prostatic Neoplasms, Castration-Resistant; Pyridines; Quinolines; Signal Transduction; Tumor Microenvironment

The PI3K/Akt/mTOR pathway is activated in most castration-resistant prostate cancers (CRPC). Transcriptionally active androgen receptor (AR) plays a role in the majority of CRPCs. Therefore, cotargeting full-length (FL) AR and PI3K/Akt/mTOR signaling has been proposed as a possible, more effective therapeutic approach for CRPC. However, truncated AR-splice variants (AR-V) that are constitutively active and dominant over FL-AR are associated with tumor progression and resistance mechanisms in CRPC. It is currently unknown how blocking the PI3K/Akt/mTOR pathway impacts prostate cancer driven by AR-Vs. Here, we evaluated the efficacy and mechanism of combination therapy to block mTOR activity together with EPI-002, an AR N-terminal domain (NTD) antagonist that blocks the transcriptional activities of FL-AR and AR-Vs in models of CRPC.. To determine the functional roles of FL-AR, AR-Vs, and PI3K/Akt/mTOR pathways, we employed EPI-002 or enzalutamide and BEZ235 (low dose) or everolimus in human prostate cancer cells that express FL-AR or FL-AR and AR-Vs (LNCaP95). Gene expression and efficacy were examined in vitro and in vivo. EPI-002 had antitumor activity in enzalutamide-resistant LNCaP95 cells that was associated with decreased expression of AR-V target genes (e.g., UBE2C). Inhibition of mTOR provided additional blockade of UBE2C expression. A combination of EPI-002 and BEZ235 decreased the growth of LNCaP95 cells in vitro and in vivo. Cotargeting mTOR and AR-NTD to block transcriptional activities of FL-AR and AR-Vs provided maximum antitumor efficacy in PTEN-null, enzalutamide-resistant CRPC. Clin Cancer Res; 22(11); 2744-54. ©2015 AACR.

Topics: Alternative Splicing; Animals; Antineoplastic Agents, Hormonal; Antineoplastic Combined Chemotherapy Protocols; Benzamides; Benzhydryl Compounds; Cell Line, Tumor; Cell Proliferation; Drug Synergism; Everolimus; Gene Expression Regulation, Neoplastic; Glycerol; Imidazoles; Male; Mice, Inbred NOD; Mice, SCID; Nitriles; Phenylthiohydantoin; Prostatic Neoplasms, Castration-Resistant; Protein Isoforms; Quinolines; Receptors, Androgen; Signal Transduction; TOR Serine-Threonine Kinases; Xenograft Model Antitumor Assays

Effective therapeutic strategies that can achieve long-term improvement in patients with castration resistant prostate cancer are urgently needed. We recently reported that the activated PI3K/Akt/mTOR signaling pathway induced by docetaxel explains resistance to docetaxel in castration resistant prostate cancer. In this study we explored the efficacy of NVP-BEZ235, a dual PI3K and mTORC1/2 inhibitor, for docetaxel resistant castration resistant prostate cancer.. We used the 2 human castration resistant prostate cancer cell lines C4-2 and C4-2AT6. At our laboratory C4-2AT6 cells were established from C4-2 under androgen ablated treatment for 6 months. We investigated the efficacy of NVP-BEZ235 monotherapy and NVP-BEZ235 combined with docetaxel in vitro and in vivo.. Increased phosphorylated Akt in C4-2AT6 cells was significantly inhibited by NVP-BEZ235 in a dose and time dependent manner. WST cell proliferation assay results in C4-2AT6 cells revealed that combined administration of NVP-BEZ235 and docetaxel had significant, synergistically greater cytotoxicity than NVP-BEZ235 or docetaxel monotherapy. Combined NVP-BEZ235 (40 mg/kg) and docetaxel (4 mg/kg) in vivo in a castrated mouse xenograft model inhibited C4-2AT6 tumor growth to a greater degree than in the monotherapy groups. Also, NVP-BEZ235 showed significant efficacy with docetaxel at a low concentration in vivo, suggesting that NVP-BEZ235 effectively decreased resistance to docetaxel.. Results suggest that inhibition of the PI3K/Akt/mTOR signaling pathway by NVP-BEZ235 can overcome docetaxel resistance in human castration resistant prostate cancer. Our findings provide a molecular basis for the clinical use of combined administration of NVP-BEZ235 and docetaxel in patients with castration resistant prostate cancer.

Topics: Animals; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Cell Line, Tumor; Disease Models, Animal; Docetaxel; Humans; Imidazoles; Male; Mice; Mice, Inbred BALB C; Orchiectomy; Phosphoinositide-3 Kinase Inhibitors; Prostatic Neoplasms, Castration-Resistant; Quinolines; Taxoids; TOR Serine-Threonine Kinases; Xenograft Model Antitumor Assays

According to recent studies, mTOR (mammalian target of rapamycin) inhibitor and tyrosine kinase inhibitor (TKI) can be used as combinational agents to enhance the antitumor effect or overcome resistance to one of the agents. In the present study, we investigated the synergistic interaction between NVP-BEZ235, a PI3K (phosphoinositide 3-kinase)/mTOR dual inhibitor, and sunitinib, a TKI, in castration-resistant prostate cancer (CRPC) cells with docetaxel resistance. Prostate cancer cells with different sensitivities to hormones and docetaxel levels were exposed to escalating doses of NVP-BEZ235 alone and in combination with sunitinib. The synergy between NVP-BEZ235 and sunitinib was determined by the combination index, three-dimensional model, and clonogenic assays. Flow cytometry and western blot analysis of proteins related to apoptosis and cell survival axis were performed. The combination of NVP-BEZ235 and sunitinib caused a significant synergistic antitumor effect over a wide range of doses in docetaxel-resistant CRPC cells. Furthermore, the IC50 (half-maximal inhibitory concentration) of NVP-BEZ235 and sunitinib was reduced by 7.8-fold and 6.6-fold, respectively. The three-dimensional synergy analysis resulted in a synergy volume of 182.47 μM/ml2%, indicating a strong synergistic effect of combination therapy. Combination therapy caused an induction of caspase-dependent apoptosis in docetaxel-resistant CRPC cells. Adding sunitinib did not produce any additional effect on the NVP-BEZ235-mediated inhibition of PI3K/AKT/mTOR phosphorylation. In conclusion, combining NVP-BEZ235, a dual PI3K/mTOR inhibitor, with sunitinib can synergistically potentiate the antitumor effect in CRPC cells after docetaxel failure though induction of caspase-dependent apoptosis.

Topics: Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Apoptosis Regulatory Proteins; Caspases; Cell Line, Tumor; Docetaxel; Dose-Response Relationship, Drug; Drug Resistance, Neoplasm; Drug Synergism; Humans; Imidazoles; Indoles; Male; Phosphorylation; Prostatic Neoplasms, Castration-Resistant; Proto-Oncogene Proteins c-akt; Pyrroles; Quinolines; Sunitinib; Taxoids; Vascular Endothelial Growth Factor Receptor-2

Increased expression of histone deacetylases (HDACs) and activation of the PI3K-Akt-mTORC1 pathway are common aberrations in prostate cancer (PCa). For this reason, inhibition of such targets is an exciting avenue for the development of novel therapeutic strategies to treat patients with advanced PCa. Previous reports demonstrated that HDAC inhibitors (HDACi) increases DNA damage and induce greater apoptosis in PCa cell lines that express androgen receptor (AR). In this study we utilized the AR negative PCa cell line and observed that re-expression of AR (PC3-AR) results in greater levels of apoptosis when treated with the pan-DACi, panobinostat (PAN). PAN mediated apoptosis in PC3 and PC3-AR cells was associated with increased levels of double strand DNA breaks, indicated by p-ɣH2AX. Further, PAN treatment in PC3-AR cells resulted in moderate attenuation of the ATM-Akt-ERK DNA damage response pathway. For this reason, we combined PAN with the dual PI3K-mTOR inhibitor, BEZ235. Combination of PAN with BEZ235 resulted in significant attenuation of the DNA damage repair protein ATM and significantly increased anti-tumor activity compared to each single treatment. Overall, superior anti-tumor activity with combination of PAN with BEZ235 was independent of AR status. These findings suggest that this therapeutic strategy should be further developed in clinical trials.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Cell Proliferation; DNA Damage; Histone Deacetylase Inhibitors; Humans; Hydroxamic Acids; Imidazoles; Indoles; Male; Mice; Mice, SCID; Oncogene Protein v-akt; Panobinostat; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Prostatic Neoplasms, Castration-Resistant; PTEN Phosphohydrolase; Quinolines; Random Allocation; Signal Transduction; TOR Serine-Threonine Kinases; Xenograft Model Antitumor Assays