Dipyridamole-cisplatin potentiation: enhanced in vivo cytotoxicity in xenograft models of human testicular and bladder cancers.

The antitumor efficacy and host toxicity of dipyridamole (DP), methotrexate (MTX) and cisplatin (CDDP) alone and combined were evaluated in a nude mouse supported human bladder cancer model. Single agent post treatment tumor volume growth ratio [TGR] values of DP, MTX and CDDP were 97%, 65% and 49% of control. While the MTX/DP combination produced only mild cytotoxic enhancement, CDDP/DP and CDDP/MTX/DP reduced TGR to 20% and 17%, respectively. A second multi-dose evaluation of CDDP/DP using human testicular carcinoma in this model also showed a CDDP dose-dependent response with achievable complete tumor regression. Host toxicity was not substantially increased by DP. DP would appear to be effective in vivo as a chemosensitizer of CDDP; it may enhance the therapeutic efficacy of CDDP in a variety of tumors.