Contribution of extragonadal steroids to the androgen receptor activity and to the castration-resistance development in recurrent prostate cancers after primary therapy.

Abstract

148 Background: Beyond testosterone, several steroids contribute to the activation of the androgen receptor (AR) pathway, but their relative contributions in castrated prostate cancer (PCa) patients remain unknown. Methods: Serum levels of nine steroids were measured by mass spectrometry from continuously castrated patients of the PR.7 study (n=219) and from the PCA24 cohort (n=116). For each steroid, standard curves for dose-dependent prostate-specific antigen promoter activation were built in castration-sensitive (LAPC4) and resistant (VCaP) PCa models. Standard curves were used to determine the AR activation potency for each steroid measurement from patients. Results: In LAPC4 and VCaP cells, testosterone, dihydrotestosterone and androstenedione induced AR transcriptional activity, while dehydroepiandrosterone, 5alpha-androstan-3beta,17beta-diol, androstenediol, androsterone stimulated AR only in VCaP cells. Extragonadal steroids were responsible for 34% (LAPC4) and 88% (VCaP) of the serum total AR transcriptional activity found in castrated patients. The total AR transcriptional activity secondary to testosterone, dihydrotestosterone and androstenedione was associated with time to castration resistance in patients from the PR.7 study (HR=2.17; 95% CI: 1.12-4.23; p=0.02) in multivariate analysis using the castration-sensitive model (LAPC4). AR transcriptional activity of extragonadal androstenedione was the only steroid statistically associated with time to castration resistance in univariate analysis (HR=1.89; 95% CI: 1.04-3.44; p=0.036). Conclusions: Extragonadal steroids contribute significantly to the AR axis activation at testosterone castration levels in recurrent non-metastatic PCa and these sustain the development of castration resistance after primary local treatment.