Studies on the effects of inhibitors of androgen synthesis in model system for prostate cancer

Abstract

Our laboratory have designed and synthesized a number of cytochrome P450 17alpha-hydroxylase/C17,20-lyase (P450c17) inhibitors with the aim of inhibiting androgen synthesis and as potential agents to treat prostate cancer. VN/63-1, VN/85-1, VN/87-1, VN/107-1, VN/108-1, and VN/109-1 inhibitor were chosen for study. To select the most potent inhibitors, a new method for evaluating inhibitors of the P450c17 enzyme was designed. Bacteria expressing the P450c17 were used as a source of the enzyme. HPLC was replaced by a rapid radiometric assay, acetic acid releasing assay. This new analytical system will be a powerful tool to accelerate the process of new compound selection. Utilizing this system, I showed that VN/85-1, VN/87-1, and VN/108-1 are the most potent inhibitors of P450c17. The effects of the new inhibitors on androgen dependent LNCaP and androgen independent PC-3 prostatic carcinoma cells proliferation were studied. I have shown that VN/85-1, VN/87-1, and VN/108-1 are the most potent inhibitors of LNCaP cell growth in vitro . VN/85-1 also has weak inhibitory effects against androgen independent PC-3 cells. The effects of azolyl steroids on LNCaP androgen receptor (AR) were determined. VN/63-1, VN/85-1, and VN/87-1 were full antagonists of LNCaP AR. Although, VN/107-1 , VN/108-1, and VN/109-1 were partial agonists of LNCaP AR, all of the evaluated inhibitors were antiandrogens against the wild-type AR. The new inhibitors were also evaluated in vivo. The male SCID mice bearing LNCaP tumor xenografts were utilized for new compounds evaluation. I showed that VN/85-1 and VN/87-1 have potent antitumor effects in this in vivo model. The ability of pregnenolone to stimulate LNCaP cell proliferation was discovered and investigated. I showed that this pregnenolone stimulation is mediated through the mutated AR and can be inhibited by our novel compounds, especially by VN/63-1, VN/85-1, and VN/87-1. This findings suggests that pregnenolone has a significant role in stimulating prostate cancer and that our new compounds by inhibiting not only androgens but also pregnenolone action may be more effective for treating prostate cancer than currently available agents.