1454 TETRANDRINE BLOCKS EMERGENCE OF CASTRATE RESISTANT PHENOTYPE BY PROMOTING APOPTOSIS AND SENSITIZING PROSTATE CANCER CELLS TO ANDROGEN DEPRIVATION

Abstract

zymes 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.