Effect of verapamil on paclitaxel toxicity to marrow progenitor cells.

 Normal human CD34⁺ marrow cells were exposed to paclitaxel (0.1 μM) alone or after pretreatment with verapamil (50 μg/mL). Cells were then cultured in methylcellulose in the presence of cytokines designed to stimulate the growth of CFU-GM (A), BFU-E (B), or CFU-Meg (C) colonies. Growth of untreated (control) cells, as well as cells exposed to verapamil alone, is shown for comparison purposes. Data from 4 different donors performed in quadruplicate are shown.