Study of Recurrent Prostate Cancer With Rising Prostate Specific Antigen (PSA)

The primary hypothesis of this study is that disulfiram is a DNA methyltransferase inhibitor and may provide benefit for patients with prostate cancer by restoration of tumor suppressor genes. Disulfiram is a potent DNA methyltransferase 1 (DNMT1) inhibitor in vitro in our laboratory and it was recently found as one of the most potent inhibitors for PCa growth in vitro by screening the Johns Hopkins Drug Library. Based on this data, extensive in vitro and in vivo studies have been performed to explore its potential antitumor activities in prostate PCa. Using both androgen sensitive and insensitive PCa cell lines, we have confirmed that disulfiram can demethylate known highly methylated tumor suppressor genes such as APC and RARß in PCa cell lines. Disulfiram inhibited PCa cell growth in vitro and in vivo. In addition to these new findings, the antitumor activity of disulfiram and its other possible mechanisms of action are well documented in literature. Disulfiram has been shown to induce apoptosis in a number of cell lines including PCa. A variety of underlying mechanisms of anticancer activity have been reported. Disulfiram has been shown to reduce angiogenesis, inhibit DNA topoisomerases, inhibit nuclear factor κB, induce p21 and p53 with G1/S cell cycle arrest, induce pro-apoptotic redox-related mitochondrial membrane permeabilization, inactivate Cu/Zn superoxide dismutase by Cu2+ complexation, inhibit Zn2+-dependent matrix metalloproteinases, and prevent tumor invasion or metastasis. The disulfiram analogue pyrrolidine dithiocarbamate (PDTC) has been shown to inhibit proteasomal activity in combination with copper in human breast and PCa cell lines. Also, disulfiram or its metabolites permanently inactivate the human multidrug resistance P-glycoprotein or reverses either MDR1- or MRP1-mediated drug efflux.