Verapamil enhancement of antitumor effect of cis-diamminedichloroplatinum(II) in nude mouse-grown human neuroblastoma.

The antitumor effect of combined use of cis-diamminedichloroplatinum(II) (CDDP) and verapamil, a calcium influx blocker, was examined in neuroblastoma transplanted to BALB/c athymic mice. The response of the tumor to CDDP was related to the dose administered. Regression of the tumor was observed when CDDP was administered at 4.2 mg/kg/injection. The retardation of tumor growth was observed in the group to which CDDP was administered at 2.1 mg/kg/injection. When verapamil was administered with CDDP, regression of the tumor was observed in the group treated with CDDP at 2.1 mg/kg/injection, and the retardation of tumor growth was observed in the group treated with CDDP at 1.4 mg/kg/injection. These results indicate that verapamil enhances the antitumor effect of CDDP against transplanted neuroblastoma in BALB/c athymic mice.