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

Purpose: Chemosensitizers such as cyclosporin A can increase intracellular accumulation of chemotherapeutic agents such as Adriamycin in certain multi drug-resistant (MDR) cell lines with overexpression of P-glycoprotein. It i s likely that, when combined with cyclosporin A: hyperthermia could increas e membrane permeability to Adriamycin and enhance its cytotoxic effects. Th e ability of both hyperthermia and cyclosporin A to modulate the cytotoxici ty, transport and subcellular distribution pattern of Adriamycin was studie d in a pleiotropic MDR Chinese hamster ovary cell line (CH(R)C5) and in the drug-sensitive parent line (AuxB1). Methods: Adriamycin cytotoxicity was e valuated by clonogenic cell survival, drug transport using [C-14]-labeled A driamycin and intracellular drug distribution by fluorescence microscopy. R esults: Adriamycin cytotoxicity was increased in both drug-sensitive and MD R cells by cyclosporin A (5 mu M) alone, and by hyperthermia alone (41-43 d egrees C) only in sensitive cells. However, when cyclosporin A and 42 degre es C hyperthermia were used in combination, a large increase in drug cytoto xicity occurred in both cell lines This effect increased with time and was temperature-dependent. The increase in Adriamycin cytotoxicity caused by cy closporin A and hyperthermia was accompanied by alterations in membrane per meability to the drug. Cyclosporin A increased [C-14]Adriamycin uptake, whi le drug efflux decreased, for both AuxB1 and CH(R)C5 cells and nuclei. For AuxB1 cells only, drug distribution studies showed that cyclosporin A promo ted an increase in both nuclear and cytoplasmic drug accumulation. Hyperthe rmia, combined with cyclosporin A, increased [C-14]Adriamycin uptake. This effect was seen as an increase in intensity of nuclear and cytosolic drug f luorescence 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. Conclusions : Hyperthermia alone had little effect on Adriamycin cytotoxicity and trans port 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 intr acellular drug accumulation, thus improving the effectiveness of Adriamycin against both drug-sensitive and MDR cells within a localized target region .