Androgen ablation therapy provides effective palliation for patients with advanced cancer of the prostate for only a short duration because the tumor eventually develops resistance. Among the many potential molecular mechanisms involved in the development of tumor resistance to both androgen ablation therapy and chemotherapy, mutations in the p53 tumor suppressor gene, overexpression of the antiapoptotic protein bcl-2, and overexpression of the multidrug resistance protein probably play a role. Because hormone-resistant tumors demonstrate greater expression of bcl-2 and because transfection of the bcl-2 gene into hormone-sensitive tumor cells confers resistance to both hormone therapy and chemotherapy, efforts to abrogate bcl-2 in prostate tumors represent one approach to improve clinical results. Of several agents recently shown to reduce prostate-specific antigen levels in phase II studies, 13-cis-retinoic acid and interferon-alpha can reduce the expression of bcl-2 and overcome bcl-2-mediated resistance to paclitaxel in resistant cell lines. For these reasons, our current studies test the hypothesis that reducing the expression of bcl-2 with 13-cis-retinoic acid and interferon-alpha in combination with taxanes will improve clinical results. Additionally, other studies test the hypothesis that treatment early, before the development of resistance mechanisms, in hormone-sensitive disease will improve results. Studies with docetaxel (Taxotere; Rhône-Poulenc Rorer, Collegeville, PA) and with estramustine combination therapy are also ongoing.