Treatment of PARP1-KO leukemic cells with APO866 led also to an upregulation of antioxidant genes including (catalase and other genes DHCR24, GSR, UCP2, SIRT2...) that are known to play a crucial role in drug resistance in different types of cancer cell, which could provide a plausible explanation on how PARP1-KO leukemic cells displayed less sensitivities to APO866. The gene discussed is GSR; the disease is cancer.