Modulation of Adriamycin cytotoxicity and transport in drug-sensitive and multidrug-resistant Chinese hamster ovary cells by hyperthermia and cyclosporin A

Abstract

Chemosensitizers such as cyclosporin A can increase intracellular accumulation of chemotherapeutic agents such as Adriamycin in certain multidrug-resistant (MDR) cell lines with overexpression of P-glycoprotein. It is likely that, when combined with cyclosporin A, hyperthermia could increase membrane permeability to Adriamycin and enhance its cytotoxic effects. The ability of both hyperthermia and cyclosporin A to modulate the cytotoxicity, transport and subcellular distribution pattern of Adriamycin was studied in a pleiotropic MDR Chinese hamster ovary cell line (CH(R)C5) and in the drug-sensitive parent line (AuxB1). Adriamycin cytotoxicity was evaluated by clonogenic cell survival, drug transport using [(14)C]-labeled Adriamycin and intracellular drug distribution by fluorescence microscopy. Adriamycin cytotoxicity was increased in both drug-sensitive and MDR cells by cyclosporin A (5 microM) alone, and by hyperthermia alone (41-43 degrees C) only in sensitive cells. However, when cyclosporin A and 42 degrees C hyperthermia were used in combination, a large increase in drug cytotoxicity occurred in both cell lines. This effect increased with time and was temperature-dependent. The increase in Adriamycin cytotoxicity caused by cyclosporin A and hyperthermia was accompanied by alterations in membrane permeability to the drug. Cyclosporin A increased [(14)C]Adriamycin uptake, while drug efflux decreased, for both AuxB1 and CH(R)C5 cells and nuclei. For AuxB1 cells only, drug distribution studies showed that cyclosporin A promoted an increase in both nuclear and cytoplasmic drug accumulation. Hyperthermia, combined with cyclosporin A, increased [(14)C]Adriamycin uptake. This effect was seen as an increase in intensity of nuclear and cytosolic drug fluorescence in both cell lines. Cyclosporin A alone diminished drug efflux and caused Adriamycin to remain firmly bound in the nucleus of AuxB1 cells, while it remained primarily in the cytoplasm of CH(R)C5 cells. Hyperthermia alone had little effect on Adriamycin cytotoxicity and transport in MDR cells, in contrast to drug-sensitive cells. This suggests that P-glycoprotein is fully functional in these MDR cells. Our findings suggest that cyclosporin A and hyperthermia could be beneficial by increasing intracellular drug accumulation, thus improving the effectiveness of Adriamycin against both drug-sensitive and MDR cells within a localized target region.