Abstract 4554: Regulation of intracrine androgen synthesis by NF-kappaB2/p52

Abstract

Abstract Introduction: Benign prostatic hyperplasia and the initial stages of prostate cancer (CaP) exhibit androgen dependence, but androgen ablation results only in temporary regression of CaP, with progression to castration-resistant prostate cancer (CRPC). Androgen receptor (AR) signaling remains active in CRPC due to aberrant activation of the AR. Synthesis of intracrine androgens has emerged as one of the mechanisms by which AR is activated in CRPC after androgen ablation. Even though levels of androgen biosynthetic enzymes have been shown to be elevated in CRPC, their regulation is not completely understood. In this study, we examined the role of NF-kappaB2/p52 in intracrine androgen synthesis and castration-resistant progression of CaP. Methods: Expression levels of androgen biosynthetic enzymes were measured in CaP cells with or without expression of NF-kappaB2/p52 using real-time RT-PCR and western blotting. Regulation by NF-kappaB2/p52 was examined using luciferase reporter assays and plasmids containing regulatory elements of androgen biosynthetic enzymes. Intracrine levels of androgens were measured using EIA in tumors obtained from castrated mice. Results: Expression levels of androgen biosynthetic enzymes including AKR1C3, CYP17A1, HSD3B2, and SRD5A1 were found to be elevated in CaP cells expressing NF-kappaB2/p52. Luciferase assays showed that NF-kappaB2/p52 regulates their expression directly by binding to their promoters and inducing transcription. The levels of total testosterone in CaP cells expressing NF-kappaB2/p52 were approximately 3-fold higher than control cells as measured using EIA. Intraprostatic androgen levels were found to be at 1002 ± 232 pg/g tissue, compared to 377.8 ± 105 pg/g tissue in control tumors obtained by orthotopic implantation of CaP cells expressing NF-kappaB2/p52. These data suggest that CaP cells synthesize detectable levels of testosterone in the absence of exogenous steroid precursors and overexpression of NF-kappaB2/p52 can increase this process, possibly by enhancing the expression of genes encoding steroidogenic enzymes. Conclusions: Intraprostatic androgen synthesis in recurrent prostate tumors contributes significantly to resistance to androgen ablation and development of CRPC. NF-kappaB2/p52 regulates the expression levels of steroidogenic enzymes and thereby enhances synthesis of intracrine androgens and aberrant activation of the AR. Coupled with our previous studies, these data suggest that antagonizing NF-kappaB2/p52 signaling may prove beneficial in CRPC therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4554. doi:10.1158/1538-7445.AM2011-4554