Nevertheless, studies using mouse transmitochondrial cybrids, where specific mtDNA variants have been introduced into cells with identical nuclear backgrounds, have shown that G→A at position 13997 bp and a frame-shift mutation at position 13885 bp caused by the insertion of a C residue, in the ND6 gene, were involved in metastasis and can affect tumor phenotype [40]. Here, MT-ND6 is linked to neoplasm.