Role of structural factors of antitumour anthraquinone derivatives and analogues in the ability to undergo bioreductive activation by NADPH cytochrome P450 reductase: implications for increasing the activity against sensitive and multidrug-resistant leukaemia HL60 cells

The aim of this study was to examine the role of structural factors of antitumour anthraquinone derivatives and analogues in the ability to undergo bioreductive activation by NADPH cytochrome P450 reductase (CPR) and determine the impact of this activation on increasing the activity especially with regard to multidrug resistant (MDR) tumour cells. It was found that at a high NADPH concentration (500 µmol/l), the anthracenedione agent ametantrone, with an unmodified quinone structure, was susceptible to CPR-dependent reductive activation. In contrast, it was shown that compounds with modified quinone grouping (benzoperimidine BP1, anthrapyridone CO1 and pyrazolopyrimidoacridine PPAC2) did not undergo reductive activation by CPR. This suggests that the presence of a modified quinone function is the structural factor excluding reductive activation of antitumour anthraquinone derivatives and analogues by CPR. In the second part of the work, the ability of antitumour anthraquinone derivatives and analogues to inhibit the growth of the human promyelocytic, sensitive leukaemia HL60 cell line as well as its MDR sublines exhibiting two different phenotypes of MDR related to the overexpression of P-glycoprotein (HL60/VINC) or MRP1 (HL60/DOX) was studied in the presence of exogenously added CPR. A significant increase in the activity of ametantrone with an unmodified quinone structure after its reductive conversion by CPR was observed against HL60 as well as HL60/VINC and HL60/DOX cells, whereas in the case of quinone-modified compounds (BP1, CO1 and PPAC2), the presence of the activation system had no effect on their activity against the sensitive and MDR tumour cells examined.