High mitochondrial DNA copy number was associated with an increased gastric cancer risk in a Chinese population.

Mitochondrial DNA (mtDNA) copy number (mtCN) may be a potential biomarker in relation to cancer risk. However, the role of mtCN in gastric cancer remains uncertain. We examined the association between peripheral blood leukocytes mtCN level and gastric cancer risk in a case-control study including 984 gastric cancer cases and 984 controls. We measured relative mtCN level by real-time quantitative PCR-based assay, and used logistic regression models to assess the association between mtCN and risk of gastric cancer. The mtCN level in gastric cancer cases was significantly higher than that in controls (median value: 6.53 vs 4.12, P = 1.79 × 10-5 ). Compared with those with low mtCN, the risk for gastric cancer was 1.29 (95% confidence interval [CI] = 1.02-1.63) in the median group and 1.74 (95%CI = 1.39-2.18) in the high mtCN group (P for trend = 1.51 × 10-6 ). Because relative telomere length (RTL) has been associated with gastric cancer risk in our previous study, we also evaluated the combined effects of mtCN and RTL on gastric cancer risk. Multivariable regression model revealed that the effects of mtCN and RTL were independent on gastric cancer risk. Compared with those in the lowest risk group by combining mtCN and RTL, the odds ratio for gastric cancer was 4.30 (95%CI = 2.79-6.63) in the highest risk group. Our results suggest that mtDNA may be implicated in gastric carcinogenesis and mtCN as well as RTL may serve as joint susceptible biomarkers for gastric cancer.