Synergistic interaction of cyclosporin A and verapamil on vincristine and daunorubicin resistance in multidrug-resistant human leukemia cells in vitro

Summary We studied the effects of cyclosporin A and verapamil on the modulation of vincristine and daunorubicin resistance in a multidrug-resistant subline of human T-cell acute lymphatic leukemia GM3639. Our results show that cyclosporin A is more effective than verapamil as a modulator of the high degree of primary vincristine resistance and the low degree of daunorubicin cross-resistance expressed by this cell line. Isobologram analysis revealed that the combined modulators act synergistically in correcting both vincristine and daunorubicin resistance.Financially supported by the Marcia Slater Society for Research in Leukemia, the Jacob Wallerstein Foundation, and the Children's Leukemia Research Foundation