We describe an in vitro model for prostate cancer treatment that suggests a potential benefit for combined androgen ablation and cytotoxic chemotherapy. Androgen treatment of the LNCaP hormone-dependent human prostate cancer cell line induces increased expression of the BCL-2 protein. Increased levels of this protein are known to mediate inhibition of apoptosis. LNCaP cells, however, did not undergo apoptosis in response to androgen withdrawal. Etoposide exerts its cytotoxicity on LNCaP and other cells by inducing apoptosis. In vitro etoposide cytotoxicity was diminished 83% in the presence of either 10(-8) M dihydrotestosterone or 10(-9) M R1881 in LNCaP cells. The interaction between androgen and etoposide was mediated through the BCL-2 protein, since bcl-2 antisense oligonucleotides blocked the protective effect of androgens on etoposide cytotoxicity.