Comparison of daunorubicin and anthrapyrazolone sensitivity and transport in resistant cell lines

Two P388 cell lines with acquired resistance to daunorubicin have been shown to exhibit cross-resistance to anthrapyrazolone (NSC 357885). The degree of cross-resistance observed in these cell lines (58 and 150 fold) is similar to those observed towards daunorubicin (34 and 142 fold). However the decreased drug accumulation observed for daunorubicin in the resistant cell lines (4-6 fold) is not observed for anthrapyrazolone. Similarly, verapamil can increase daunorubicin accumulation in resistant cells but has no effect on anthrapyrazolone accumulation. It is concluded that in contrast to daunorubicin, decreased anthrapyrazolone accumulation is not the resistance mechanism operative in daunorubicin resistant cell lines towards anthrapyrazolone.