[The enhancement of the chemotherapeutic effects on human prostate cancer cell--the combination with the growth factor interaction inhibitor (suramin)].

The present study was designed to evaluate the antiproliferative effects of suramin and the combination of suramin plus cisplatin (CDDP) on the hormone-independent human prostate carcinoma cell line (PC-93). In vitro, suramin induced a dose-dependent reduction of PC-93 proliferation, and at the clinically achievable concentration (300 micrograms/ml), suramin induced a 19.7% decrease in proliferation on the 3rd day compared to suramin-free control (P < 0.01). However, from the 4th day on the inhibitory action of suramin was reversed following exposure. The suramin-cisplatin combination showed an additive effect (inhibition ratio 32.4% on the 3rd day), and prolongation of the inhibition activity on the 4th day on, but it did not show any synergistic effect. Suramin inhibited dose-dependently the growth stimulatory effect of exogenous epidermal growth factor (EGF). In vivo study, suramin and suramin-cisplatin combination showed antitumor effects continuously in nude mouse implanted PC-93. These findings suggest that the inhibitory effects of suramin on PC-93 are mediated by inhibition of the EGF-mediated growth mechanism, but by a cytostatic rather than cytotoxic manner in vitro. In addition, other mechanisms such as inhibition of angiogenesis factor might exist in vivo.