The contribution of PARP1 in the depletion of antioxidant leukemia cell capacity (catalase; heme oxygenase-1) is suggested by the fact that genetic deletion of PARP1 indeed fully blunted H2O2 generation in APO866-treated cancer cells, via regulation of several genes involved in oxidative stress, including many antioxidant genes. This evidence concerns the gene CAT and cancer.