The drug resistant cell line K562 AZQ has been developed from the parent K562 cell line by treatment with AZQ C215-bis (carboethoxyamino)-3, 6-diazitinyl 1;4 (benzoquinone). The cells have been shown to contain decreased levels of glutathione and superoxoid dismutase. They are cross-resistant to adriamycin, mitzolamide, MMNG and mitmycin. Cells should be challenged with AZQ at every 4th passage at a minimum density of 100,000 cells/ml. It is recommended to cultivate the cells without drug on resuscitation.