On the other hand, to escape from the detrimental effect of overproduced O2−, CLL cells adopted a mechanism to eliminate O2− more efficiently by converting inactive SOD2 into a constitutively active enzyme via inducing SIRT3 expression, while maintaining low levels of catalase through variable degrees of promoter methylation for H2O2 accumulation to promote cell survival (Fig. 6). Here, SIRT3 is linked to B-cell chronic lymphocytic leukemia.