Evidence for Efficacy of New Hsp90 Inhibitors Revealed by Ex Vivo Culture of Human Prostate Tumors

Abstract

Purpose: Targeting Hsp90 has significant potential as a treatment for prostate cancer, but prototypical agents such as 17-allylamino-17 demethoxygeldanamycin (17-AAG) have been ineffective in clinical trials. Recently, a phase I study aimed at defining a biologically active dose reported the first response to an Hsp90 inhibitor in a patient with prostate cancer, which supports the development of new generation compounds for this disease.Experimental Design: The biological actions of two new synthetic Hsp90 inhibitors, NVP-AUY922 and NVP-HSP990, were evaluated in the prostate cancer cell lines PC-3, LNCaP, and VCaP and in an ex vivo culture model of human prostate cancer.Results: In cell lines, both NVP-AUY922 and NVP-HSP990 showed greater potency than 17-AAG with regard to modulation of Hsp90 client proteins, inhibition of proliferation, and induction of apoptotic cell death. In prostate tumors obtained from radical prostatectomy that were cultured ex vivo, treatment with 500 nmol/L of NVP-AUY922, NVP-HSP990, or 17-AAG caused equivalent target modulation, determined by the pharmacodynamic marker Hsp70, but only NVP-AUY922 and NVP-HSP990 showed antiproliferative and proapoptotic activity.Conclusions: This study provides some of the first evidence that new generation Hsp90 inhibitors are capable of achieving biologic responses in human prostate tumors, with both NVP-AUY922 and NVP-HSP990 showing potent on-target efficacy. Importantly, the ex vivo culture technique has provided information on Hsp90 inhibitor action not previously observed in cell lines or animal models. This approach, therefore, has the potential to enable more rational selection of therapeutic agents and biomarkers of response for clinical trials. Clin Cancer Res; 18(13); 3562-70. Ó2012 AACR.

Peptidomimetic targeting of critical androgen receptor–coregulator interactions in prostate cancer

“…Fresh prostate cancer tissues were obtained with informed consent from men undergoing radical prostatectomy at the Hospitals of the University of Texas Southwestern Medical Center (Dallas, TX) 43 (see Supplementary Table S2 for clinicopathological characteristics). The tissues were dissected into 1 mm 3 pieces and randomly placed in triplicates on a pre-soaked 1-cm 3 veterinary dental sponge (Novartis, East Hanover, NJ) inside the wells of a 12-well plate containing 600 ml RPMI 1640 with 5% heat-inactivated FBS, 100 units per ml penicillin-streptomycin and vehicle (DMSO) alone, D1 (100 nM) or D2 (100 nM).…”

Co-targeting AR and HSP90 suppresses prostate cancer cell growth and prevents resistance mechanisms

“…Cells were treated as indicated for 4 days and counted as previously described (Centenera et al 2012). The caspase inhibitor z-VAD-fmk (50 mM) was included for the duration of the relevant experiments.…”

“…Unfortunately, 17-AAG did not show its predicted clinical efficacy as a single agent in CRPC, due to toxicity and poor pharmacodynamic properties that prevented therapeutic doses being achieved (Banerji et al 2005, Heath et al 2008, Ramanathan et al 2010. While more potent inhibitors such as AUY922 are currently being developed and show promise as single agents (Samuel et al 2010, Centenera et al 2012, recent evidence of additive or synergistic activity between 17-AAG and cytotoxic agents or specific molecular therapeutics provides a promising new avenue of clinical development for this drug . In preclinical prostate cancer studies, 17-AAG or AUY922 combined with ionizing radiation has demonstrated supra-additive reductions in tumor growth and clonogenicity (Enmon et al 2003, Ochel & Gademann 2006, Gandhi et al 2013.…”

A patient‐derived explant (PDE) model of hormone‐dependent cancer

“…It is also applicable to multiple solid tumor types; to date, the methodology has successfully been applied to all cancers tested, including some not represented in the current study (ovary, endometrium, renal, sarcoma; personal communication). The de novo cellular proliferation observed in cultured tissues indicates that the system is not static and makes this a particularly useful model to assess the growth inhibitory activity of new or emerging therapeutic agents, as demonstrated by our respective teams using PDEs from prostate cancer and breast cancer (Centenera et al ., 2012; Comstock et al ., 2013; Dean et al ., 2012; de Leeuw et al ., 2015; Schiewer et al ., 2012). …”

“…Despite observing significant effects of bicalutamide on PDE proliferative index, apoptotic response to bicalutamide was also evaluated, using the immunohistochemistry marker cleaved caspase‐3. We have previously reported apoptosis induction in prostate cancer PDEs cultured for 48 h with other therapeutic agents (Centenera et al ., 2012). It is therefore likely that higher doses of bicalutamide than the 10 μ m used in this study are required to induce apoptosis in prostate cancer PDEs.…”