Antiandrogen-like actions of an antioxidant on survivin and bcl-2 in human prostate cancer cells.
aDepartment of Internal Medicine, Pathology, bDepartment of Internal Medicine; ARUP Institute, Salt Lake City, Utah, United States, cUniversity of Utah, Salt Lake City, Utah, United States
Aim: We have documented that testosterone (T) enhances the induction of apoptosis by antioxidants in prostate cancer cells. We postulated that antioxidants block androgen signals on androgen receptor responses that lead to antiapoptotic events in an androgen-responsive human prostate cancer cell line (ALVA-101) by modulating a nuclear factor-kappa B (NF-kB) a transcription factor. Methods: Cells were grown in RPMI 1640 medium with 5% FBS, antibiotics and 5% CO2, with or without treatment with either 10-6 or 10-12 M T and pyrrolidinedithiocarbamate [PDTC (2.5 – 10 mg/mL)], a potent antioxidant. Charcoal-stripped serum was used in experiments with added T. Cell growth was estimated using the Cell Titer 96 AQ assay. The electrophoretic mobility shift assay (EMSA) was used to quantitate nuclear factor-kappa B (NF-kB) activity. Reverse transcription / polymerase chain reaction (RT-PCR) was used to quantify the Bcl-2 and survivin mRNA expressions, and survivin protein expression was quantified by Western blot. Results: Treatment for 1 – 7 days with PDTC (2.5 – 10 mg/mL) significantly reduced cell growth by 60% (p < 0.05; n=6-8), and T (10-6M or 10-12M) in combination with PDTC significantly enhanced the apoptotic effects of PDTC alone in the ALVA-101 cell line (<0.05; n=6-8). PDTC treatment also significantly (p<0.05, n=3-6, respectively) reversed the stimulatory effect of T (10-12M) on survivin protein expression, PSA mRNA, Bcl-2 mRNA, survivin mRNA and NF-kB, all of which are known inhibitors of apoptosis. Antisense to both survivin and Bcl-2 (antiapoptotic factors) significantly (p<0.05) suppressed cell growth. Conclusions: PDTC is a potent inducer of apoptosis in human prostate cancer cells and an inhibitor of androgen action by reducing survivin protein and reversing the stimulatory effects of androgen on inhibitors of apoptosis. These antiandrogen-like effects of PDTC may contribute to the paradoxical augmentation of apoptosis induced in human prostate cancer cells treated with both T and PDTC. These results support the use of antioxidants for chemoprevention and chemotherapy of prostate cancer.
Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Nice, France; February 7 - 10, 2004; in oral session 898 (Oncogenesis).