Login to Access Video or Poster Abstract: MP57-04
Sources of Funding: This research was made possible through the National Institutes of Health (NIH) Medical Research Scholars Program, a public-private partnership supported jointly by the NIH and generous contributions to the Foundation for the NIH from the Doris Duke Charitable Foundation, The American Association for Dental Research, the Colgate-Palmolive Company, Genentech and alumni of student research programs and other individual supporters via contributions to the Foundation for the National Institutes of Health._x000D_ For a complete list, please visit the Foundation website at:_x000D_ http://fnih.org/work/education-training-0/medical-research-scholars-program

Introduction

VT464 is currently in clinical trials for the treatment of castration-resistant prostate cancer (CRPC). Interestingly, VT464 displays dual properties: it decreases androgen synthesis by inhibiting CYP17A1 and may also block AR function by binding to the ligand-binding domain (LBD) of full-length androgen receptor (ARFL). However, expression of AR variants (e.g. ARv7) lacking a LBD is a common occurrence in CRPC. Thus, ARv7 may be insensitive to direct inhibition by VT464 and other targeted agents may be necessary to blunt ARv7 expression and ARv7 regulated pathways for efficacy in CRPC._x000D_ ARv7 is stabilized by heat shock proteins (Hsp) 40 and Hsp70, which bind the AR and ARv7 N-terminal domain to prevent aggregation. Our novel compounds C86 and JG98 are inhibitors of Hsp40 and Hsp70, respectively. As such, we hypothesized that inhibition of the Hsp40/70 axis would lead to decreased CRPC cell viability and altered AR/ARv7 expression, which could be amplified in combination with VT464. Additionally, ARv7 leads to changes in cell metabolism such that cells are more dependent on glutaminolysis and fatty acid synthesis. Thus, we also hypothesized that the glutaminase inhibitor, CB839, and fatty acid synthase inhibitor, 3V-Biosciences 3166, would act in concert with VT464 for efficacy in CRPC. _x000D_

Methods

Using the CRPC cell line 22Rv1, we analyzed the effects of VT464, C86, JG98, CB839, and 3V-3166 on cell viability (MTT, Cyquant) as single agents and in combination. Western blot analysis of treated 22Rv1 cells was used to correlate protein expression changes of ARFL and ARv7 to the respective cell viability data.

Results

VT464 caused a dose-dependent decrease in 22Rv1 viability, as did C86 and JG98. Combination of either C86 or JG98 with VT464 showed additive toxicity. Importantly, both C86 and JG98 decreased ARFL and ARv7 protein expression and their downstream transcriptional activity, which may explain these combinatorial effects. Similarly, treatment with of 22Rv1 cells with 3-V3166 and CB839 inhibited cell viability, which was further decreased when combined with VT464.

Conclusions

C86 and JG98 are novel agents that inhibit AR and ARv7 stability. When combined with VT464, both agents display combinatorial activity. Further, 3V-3166 and CB839, drugs that target enzymes crucial to cells expressing ARv7, also inhibit viability to a greater extent when combined with VT464. Collectively, C86, JG98, 3V-3166, and CB839 are all promising novel therapies for CRPC, particularly for tumors which express ARv7. Further mechanistic and in vivo assays are warranted.

Funding

This research was made possible through the National Institutes of Health (NIH) Medical Research Scholars Program, a public-private partnership supported jointly by the NIH and generous contributions to the Foundation for the NIH from the Doris Duke Charitable Foundation, The American Association for Dental Research, the Colgate-Palmolive Company, Genentech and alumni of student research programs and other individual supporters via contributions to the Foundation for the National Institutes of Health._x000D_ For a complete list, please visit the Foundation website at:_x000D_ http://fnih.org/work/education-training-0/medical-research-scholars-program