MT-ND2 and neoplasm: Although the functional impact of these changes was not directly addressed, the finding that two differentially methylated sites fall within MT-ATP6 (Complex V) and a third lies in the intergenic region between MT-ND2 (Complex I) and MT-CO1 (Complex IV) suggests that tumor-associated alterations in mtDNA methylation may occur in proximity to loci involved in oxidative phosphorylation, potentially accompanying subtle mitochondrial regulatory shifts during tumorigenesis.