[The relationship between peripheral blood mitochondrial DNA copy number and incident risk of liver cancer: a...

Objective: To investigate the association between peripheral blood mitochondrial DNA copy number (mtDNAcn) and incident risk of liver cancer. Methods: At the baseline of Dongfeng-Tongji (DFTJ) cohort, 27 009 retirees were recruited from Dongfeng Motor Corporation in 2008. After excluding people without baseline DNA, with current malignant tumor and loss of follow-up, 1 173 participants were randomly selected into a sub-cohort by age-and gender-stratified sampling method at a proportion of 5% among all retirees. A total of 154 incident liver cancer cases identified from the cohort before December 31, 2018 (4 cases had been selected into the sub-cohort) were selected to form the case cohort of liver cancer. For the above 1 323 participants, their baseline levels of mtDNAcn in peripheral blood cells were measured by using quantitative real-time PCR method. The restricted cubic spline analysis was used to fit the shape of the association between baseline mtDNAcn and incident risk of liver cancer. The weighted Cox proportional hazards model was used to estimate the hazard ratio (HR) and 95%CI. Results: In this case-cohort study, the median follow-up time was 10.3 years. The restricted cubic spline analysis indicated that the relationship between peripheral blood mtDNAcn and incident risk of liver cancer followed a U-shaped pattern (P_non-linear<0.05). All case-cohort population were divided into four subgroups by sex-specific quartiles of mtDNAcn levels among sub-cohort participants, when compared to participants in the Q₂ subgroup of mtDNAcn, those in the Q₁ subgroup (HR=2.00,95%CI:1.08-3.70) and Q₄ subgroup (HR=4.11,95%CI:2.32-7.26) both had a significantly elevated risk of liver cancer, while those in the Q₃ subgroup (HR=1.05,95%CI:0.54-2.05) had not. There were no significant multiply interaction effects of aging, gender, tobacco smoking, alcohol drinking and history of chronic hepatitis on the above association (P_interaction>0.05). Conclusion: Both extremely low and high baseline level of mtDNAcn in peripheral blood cells are associated with an increased risk of incident liver cancer, but the underlying mechanisms need to be further clarified.