Slater L, Sweet P, Wetzel M, Stupecky M, Osann K
Department of Medicine, University of California, Irvine 92717, USA.
Leuk Res. 1995 Aug;19(8):543-8. doi: 10.1016/0145-2126(95)00029-n.
Although verapamil, cyclosporin A. cremophor EL and PSC-833 are active as multidrug resistance modulators, there has been limited study of these compounds as possible chemotherapy enhancing agents against drug-sensitive tumors. We compared these agents as modifiers of VP-16 cytotoxicity in vitro and modifiers of VP-16 efficacy in vivo against drug-sensitive P388 and L1210 leukemias. Our study indicates that cyclosporin A enhances VP-16 cytotoxicity to a significantly greater extent than equimolar concentrations of verapamil or PSC-833. Although cremophor EL shows significantly greater activity than verapamil in VP-16 cytotoxicity enhancement in vitro, it is ineffective when added to VP-16 therapy of mice bearing L1210 leukemia.
