panobinostat and Prostatic-Neoplasms--Castration-Resistant

This study assesses the action of panobinostat, a histone deacetylase inhibitor (HDACI), in restoring sensitivity to bicalutamide in a castration-resistant prostate cancer (CRPC) model and the efficacy and safety of the panobinostat/bicalutamide combination in CRPC patients resistant to second-line antiandrogen therapy (2. The CWR22PC xenograft and isogenic cell line were tested for drug interactions on tumor cell growth and on the androgen receptor (AR), AR-splice variant7, and AR targets. A phase I trial had a 3 × 3 panobinostat dose-escalation design. The phase II study randomized 55 patients to panobinostat 40 mg (A arm) or 20 mg (B arm) triweekly ×2 weeks with bicalutamide 50 mg/day in 3-week cycles. The primary endpoint was to determine the percentage of radiographic progression-free (rPF) patients at 36 weeks versus historic high-dose bicalutamide.. In the model, panobinostat/bicalutamide demonstrated synergistic antitumor effect while reducing AR activity. The dose-limiting toxicity was not reached. The probability of remaining rPF exceeded protocol-specified 35% in the A arm and 47.5% and 38.5% in the B arm. The probabilities of remaining rPF were 47.5% in the A arm and 38.5% in the B arm, exceeding the protocol-specified threshold of 35%. A arm/B arm: adverse events (AE), 62%/19%; treatment stopped for AEs, 27.5%/11.5%; dose reduction required, 41%/4%; principal A-arm grade ≥3 AEs, thrombocytopenia (31%) and fatigue (14%).. The 40 mg panobinostat/bicalutamide regimen increased rPF survival in CRPC patients resistant to 2

Topics: Aged; Androgen Antagonists; Anilides; Animals; Antineoplastic Combined Chemotherapy Protocols; Epigenesis, Genetic; Histone Deacetylase Inhibitors; Humans; Male; Mice; Middle Aged; Nitriles; Panobinostat; Progression-Free Survival; Prostate-Specific Antigen; Prostatic Neoplasms, Castration-Resistant; Receptors, Androgen; Tosyl Compounds; Xenograft Model Antitumor Assays

PI3K (phosphoinositide 3-kinase)/AKT and RAS/MAPK (mitogen-activated protein kinase) pathway coactivation in the prostate epithelium promotes both epithelial-mesenchymal transition (EMT) and metastatic castration-resistant prostate cancer (mCRPC), which is currently incurable. To study the dynamic regulation of the EMT process, we developed novel genetically defined cellular and in vivo model systems from which epithelial, EMT and mesenchymal-like tumor cells with Pten deletion and Kras activation can be isolated. When cultured individually, each population has the capacity to regenerate all three tumor cell populations, indicative of epithelial-mesenchymal plasticity. Despite harboring the same genetic alterations, mesenchymal-like tumor cells are resistant to PI3K and MAPK pathway inhibitors, suggesting that epigenetic mechanisms may regulate the EMT process, as well as dictate the heterogeneous responses of cancer cells to therapy. Among differentially expressed epigenetic regulators, the chromatin remodeling protein HMGA2 is significantly upregulated in EMT and mesenchymal-like tumors cells, as well as in human mCRPC. Knockdown of HMGA2, or suppressing HMGA2 expression with the histone deacetylase inhibitor LBH589, inhibits epithelial-mesenchymal plasticity and stemness activities in vitro and markedly reduces tumor growth and metastasis in vivo through successful targeting of EMT and mesenchymal-like tumor cells. Importantly, LBH589 treatment in combination with castration prevents mCRPC development and significantly prolongs survival following castration by enhancing p53 and androgen receptor acetylation and in turn sensitizing castration-resistant mesenchymal-like tumor cells to androgen deprivation therapy. Taken together, these findings demonstrate that cellular plasticity is regulated epigenetically, and that mesenchymal-like tumor cell populations in mCRPC that are resistant to conventional and targeted therapies can be effectively treated with the epigenetic inhibitor LBH589.

Topics: Animals; Blotting, Western; Cell Line, Tumor; Disease Models, Animal; Epithelial-Mesenchymal Transition; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Histone Deacetylase Inhibitors; Humans; Hydroxamic Acids; Indoles; Male; Mice, Inbred NOD; Mice, Knockout; Mice, SCID; Mice, Transgenic; Mitogen-Activated Protein Kinases; Neoplasm Metastasis; Panobinostat; Phosphatidylinositol 3-Kinases; Prostatic Neoplasms, Castration-Resistant; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins p21(ras); PTEN Phosphohydrolase; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction

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