Objectives: Hormone-refractory prostate cancer continues to be associated with a very poor prognosis. Agents that interact with the nuclear matrix have been demonstrated to have activity against hormone-refractory prostate cancer. It was the aim of this study to assess the activity of estramustine, an estradiol-nitrogen mustard conjugate, and 9-aminocamptothecin (9-AC), a topoisomerase I inhibitor, in a preclinical model of hormone-refractory prostate cancer.
Methods: We used the Dunning rat prostatic adenocarcinoma model to demonstrate that the combination of estramustine and 9-AC interacts at the level of the nuclear matrix to inhibit the growth of prostate cancer cells.
Results: We demonstrate that the combination of these two agents at pharmacologically achievable doses are cytotoxic to rat and human prostate cancer cells in vitro and in vivo in the rat.
Conclusions: The combination of the two drugs was significantly more cytotoxic than either drug alone. We have instituted a Phase II clinical trial in patients with hormone-refractory prostate cancer using 9-AC based on these preclinical findings.