Lower mitochondrial DNA copy number in peripheral blood leukocytes increases the risk of endometrial cancer

Mitochondria are the primary source of energy generation in human cells. Low mitochondrial DNA (mtDNA) copy number in peripheral blood leukocytes (PBLs) has been associated with obesity and increased risks of several cancers. Since obesity is a significant risk factor for endometrial cancer, we hypothesize that low mtDNA copy number in PBLs is associated with an increased susceptibility to endometrial cancer. Using a Caucasian case-control study, we measured mtDNA copy number in PBLs from 139 endometrial cancer patients and 139 age-matched controls and determined the association of mtDNA copy number with the risk of endometrial cancer using multivariate logistic regression analysis. The normalized mtDNA copy number was significantly lower in endometrial cancer cases (median, 0.84; range, 0.24-2.00) than in controls (median, 1.06; range, 0.64-1.96) (P<0.001). Dichotomized into high and low groups based on the median mtDNA copy number value in the controls, individuals with low mtDNA copy number had a significantly increased risk of endometrial cancer (adjusted OR, 5.59; 95%CI, 3.05-10.25; P<0.001) compared to those with high mtDNA copy number. There was a significant dose-response association in tertile analysis. In addition, there was a significant joint effect between lower mtDNA copy number and never smoking, hypertension, diabetes, and obesity in elevating the risk of endometrial cancer. Low mtDNA copy number in PBLs is significantly associated with an increased risk of endometrial cancer in Caucasians.