POTENTIATION OF PIRARUBICIN CYTOTOXICITY BY DIPYRIDAMOLE IN DOXORUBICIN-RESISTANT MOUSE P388 LEUKEMIA-CELLS

The activity of dipyridamole and its possible mechanisms which reverse the resistance to pirarubicin were studied in a P388 mouse leukemia cell lines. Dipyridamole alone was minimally cytotoxic in both of the doxorubicin-resistant cell line (P388/DOX) and the sensitive parent cell line (P388/S), but reversed pirarubicin-resistance in a dose-related manner in P388/DOX cells. A similar dose-response relationship was observed for dipyridamole by increasing net intracellular pirarubicin accumulation. The increase was a result of secondary blocking of enhanced pirarubicin efflux from P388/DOX cells. In contrast, dipyridamole did not affect cytotoxicity and transport in the drug-sensitive cell line. It is suggested that dipyridamole is a useful drug for modulation of the multidrug-resistance of cells.