Although the increased DNMTs and SAM in OXPHOS inhibition‐sensitive cancer cells may result in augmented global DNA methylation, no significant alternation of methylation level in promoter regions of the upregulated OXPHOS genes was detected, suggesting the increased expression of OXPHOS genes is unlikely the direct target for DNMTs; and thus, the direct NNMT/DNMT target(s) essential for cancer cell sensitivity to OXPHOS inhibition remain largely unknown and need further exploration. The gene discussed is NNMT; the disease is cancer.