Effects of new 17α-hydroxylase/C17,20-lyase inhibitors on LNCaP prostate cancer cell growth in vitro and in vivo

Abstract

Our laboratory has been developing new inhibitors of a key regulatory enzyme of testicular and adrenal androgen synthesis 17α-hydroxylase/C 17,20 -lyase (P450c17), with the aim of improving prostate cancer treatment. We designed and evaluated two groups of azolyl steroids: Δ5-non-competitive inhibitors (Δ5NCIs), VN/63-1, VN/85-1, VN/87-1 and their corresponding Δ4 derivatives (Δ4NCIs), VN/107-1, VN/108-1 and VN/109-1. The human P450c17 gene was transfected into LNCaP human prostate cancer cells, and the resultant LNCaP-CYP17 cells were utilized to evaluate the inhibitory potency of the new azolyl steroids. VN/85-1 and VN/108-1 had the lowest IC 50 values of 1.25 ± 0.44 n M and 2.96 ± 0.78 n M respectively, which are much lower than that of the known P450 inhibitor ketoconazole (80.7 ± 1.8 n M ). To determine whether the compounds had direct actions on proliferation of wild-type LNCaP cells, cell growth studies were performed. All of the Δ5NCIs and VN/108-1 blocked the growth-stimulating effects of androgens. In steroid-free media, the Δ5NCIs decreased the proliferation of LNCaP cells by 35–40%, while all of the Δ4NCIs stimulated LNCaP cells growth 1.5- to 2-fold. In androgen receptor (AR) binding studies, carried out to determine the mechanism of this effect, all of the Δ4NCIs (5 μ M ) displaced 77–82% of synthetic androgen R1881 (5 n M ) from the LNCaP AR. The anti-androgen flutamide and the Δ5NCIs displaced 53% and 32–51% of R1881 bound to AR respectively. These results suggested that the Δ5NCIs may also be acting as anti-androgens. We further evaluated our inhibitors in male severe combined immuno- deficient mice bearing LNCaP tumour xenografts. In this model VN/85-1 was as effective as finasteride at inhibiting tumor growth (26% and 28% inhibition, respectively) and the inhibitory effect of VN/87-1 was similar to that of castration (33% and 36% inhibition respectively). These results suggest that VN/85-1 and VN/87-1 may be potential candidates for treatment of prostate cancer. © 1999 Cancer Research Campaign

Potent CYP17 inhibitors: improved syntheses, pharmacokinetics and anti-tumor activity in the LNCaP human prostate cancer model

“…Furthermore, the anti-tumor efficacies of the compounds were evaluated in male severe combined immunodeficient (SCID) mice bearing tumor xenografts. VN/85-1 (50 mg/kg, subcutanously (s.c.), once daily) was as effective as finasteride at inhibiting tumor growth (36% versus 37%) and the inhibitory effect of VN/87-1 (50 mg/kg, s.c., once daily) was similar to that of castration (48.5% versus 51.5%) [15].…”

“…Since both compounds have the same basic steroid structure, the difference in metabolic stability is probably due principally to the difference in the 17-azolyl groups. Although this metabolite (VN/108-1) has previously been shown to be a potent CYP17 inhibitor [11] and also an inhibitor of T and DHT production in vivo [15,16] it had no significant effects on prostate cancer LNCaP tumor growth [15]. However, the compound binds to the androgen receptor and may exhibit androgenic activity [15].…”

“…3␤-Hydroxy-17-(imidazol-1-yl)androsta-5,16-diene (VN/85-1) and 3␤-hydroxy-17-(1H-1,2,3-triazol-1-yl)androsta-5,16-diene (VN/87-1) (Scheme 1) are the most promising CYP17 that we have identified. In cultures of human prostate cancer cell line (LNCaP), both compounds effectively blocked the growth-stimulating effects of T and dihydrotestosterone (DHT), and were also shown to manifest anti-androgenic activity [15]. In animal studies, both compounds reduced the levels of circulating T and DHT in male rat tissues [16].…”

Steroidogenesis inhibitors alter but do not eliminate androgen synthesis mechanisms during progression to castration-resistance in LNCaP prostate xenografts

“…Steroid starved (CSS) cells and AD, N and CRPC xenograft tumor cells were treated with 1 Ci/mL [ 3 H]-progesterone for 48 h. Steroid starved cells and CRPC tumor cells were treated with an additional 1 nM R1881 and inhibitors of CYP17A1, SRD5A2, AKR1C3, steroid receptors and AR: 20 M ketoconazole, 25 M finasteride [32,33], 50 M cinnamic acid [34], 10 M RU-486 [35] and 25 M casodex [36], respectively for the same 48-h period to determine the effect of inhibitors on steroidogenesis downstream of progesterone. Dose titrations of steroid starved LNCaP cells with 10 M progesterone and 0, 0.1, 1, 10, 20/25, 50, 100 and 1000 M ketoconazole/finasteride, were conducted in order to verify optimal dosing for metabolism studies.…”

Inhibitory effects of retinoic acid metabolism blocking agents (RAMBAs) on the growth of human prostate cancer cells and LNCaP prostate tumour xenografts in SCID mice

“…The procedure was modified from Grigoryev et al (1999). Briefly, LNCaP cells were trypsinised, counted, and suspended in Matrigel (2 Â 10 7 cells ml À1 ) (Fisher Scientific International, Inc., Hampton, NH, USA).…”