**6. Conclusions**

In the last decades, evidence on the contribution of mtDNA variants to tumorigenesis has incredibly grown. Therefore, mitochondria are actually considered one of the most promising targets for novel anticancer therapies. Accordingly, mtDNA variants can be regarded as useful tumor biomarkers for clinical practice, whereas the tight communication between nuclear and mitochondrial genomes sheds new light on the molecular and functional mechanisms underlying the onset and progression of complex human diseases, such as cancer and neurodegenerative diseases.

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