Importance of clinical exposure on verapamil enhancement of adriamycin-vincristine cytotoxicity in human neuroblastoma.

A review of the effects of Ca2+ channel blockers on vincristine and adriamycin cytotoxic activity revealed the majority of the studies to be centered on murine leukemia or human tumors of adults. We investigated the effects of verapamil, a Ca2+ channel blocker, on human neuroblastoma cells as a representative tumor of childhood. By choosing a cell line derived from a patient previously treated with vincristine but not adriamycin, we attempted to evaluate whether previous clinical exposure to a specific drug could influence the verapamil enhancement of the cytotoxic effects of that drug.