Cytostatic effects of suramin on prostate cancer cells cultured from primary tumors.

Suramin is currently undergoing clinical trials as a chemotherapeutic agent for prostate cancer. The effects of suramin on cultured human epithelial cells derived from normal, benign hyperplastic, and malignant prostate tissues were examined. In serum-free medium, suramin inhibited the clonal growth of prostate cells at a half-maximal dose of approximately 10 micrograms/ml. Growth inhibition by suramin was completely reversible even after 24 hours of exposure. In conjunction, suramin did not alter cellular phenotype with regard to expression of keratins and prostate-specific antigens. Although suramin is reportedly an antagonist of growth factor-mediated mitogenesis, ten-fold excesses of growth factors did not appreciably suppress the cytostatic activity of suramin. In comparison to the activities of other possible chemotherapeutic agents, suramin would appear suboptimal because its inhibitory effects are reversible and it does not induce a terminally differentiated cellular phenotype.