Marker for determining anti-cancer effects of mitochondrial oxidative phosphorylation pathway inhibitor

The present invention relates to a marker for determining anti-cancer effects of a mitochondrial oxidative phosphorylation pathway inhibitor. Specifically, the present invention relates to use of the mitochondrial oxidative phosphorylation pathway inhibitor for preparing a composition or a formulation for preventing and/or treating tumors. The present invention has found that the mitochondrial oxidative phosphorylation pathway inhibitor has significantly excellent treatment effects on tumors having mitochondrial oxidative phosphorylation pathway up-regulation, low or no expression of an NNMT gene, high expression of a DNA methylase, high expression of UHRF1, a high methylation level of a nucleotide site of an NNMT gene and/or a high methylation level of a DNA CpG site of an NNMT gene region.