Mitochondrial DNA (mtDNA) haplogroups and single nucleotide polymorphisms (mtSNP) have been shown to play a role in various human conditions including aging and some neurodegenerative diseases, metabolic diseases and cancer. Methods: To investigate whether mtDNA haplogroups contribute to the occurrence of cancer in a specific Chinese population, we have carried out a comprehensive case-control study of mtDNA from large cohorts of patients with three common cancer types, namely, colorectal cancer (n=108), thyroid cancer (n=100) and breast cancer (n=104), in Wenzhou, a southern Chinese city in the Zhejiang Province.

We found that patients with mtDNA haplogroup M exhibited an increased risk of breast cancer occurrence [OR=1.77; 95% CI (1.03-3.07); p=0.040], and that this risk was even more pronounced in a sub-haplogroup of M, D5 [OR=3.11; 95%CI (1.07-9.06); p=0.030]. In spite of this, in patients with breast cancer, haplogroup M was decreased in the metastatic group. On the other hand, our results also showed that haplogroup D4a was associated with an increased risk of thyroid cancer [OR=3.00; 95%CI (1.09-8.29); p=0.028]. However, no significant correlation has been detected between any mtDNA haplogroups and colorectal cancer occurrence.

Our investigation indicates that mitochondrial haplogroups could have a tissue-specific, population-specific and stage-specific role in modulating cancer development.

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