A study of blood mitochondrial DNA copy number variation and lung cancer risk: A case-control study in a Chinese population
Objective. The purpose of the study is to examine the association between mitochondrial DNA (mtDNA) content and the risk of lung cancer in a case-control study in Chinese population, and the potential modifying effects of smoking and p53codon 72 polymorphisms. Methods. Using an existing case-control study of lung cancer conducted in Taiyuan, China, we assessed the association between mtDNA content and lung cancer risk. Cases (n=399) and controls (n=466) were frequency matched on age and sex. MtDNA was measured using quantitative PCR. Unconditional logistic regression were used to model the associations between mtDNA content and lung cancer risk as well as the modifying effects of age, sex, smoking status, alcohol drinking, tea drinking, p53 codon 72 polymorphisms, respectively. Odds ratio and 95% confidence interval were calculated with unconditional logistic regression models. Results. Mitochondrial DNA content was statistically significant higher in females, non-smokers and alcohol non-drinkers compared with males (5.08 vs. 2.45), ever smokers (4.44 vs. 2.35) and alcohol ever-drinkers (4.45 vs. 2.71), separately. Elevated level of mtDNA content was associated with lung cancer risk among alcohol drinkers (adjusted OR: 2.24, 95% CI: 1.19, 4.22). In addition, synergetic effects were detected of alcohol drinking (adjusted OR for interaction: 2.77, 95% CI: 1.34, 5.72) / pack years of smoking (adjusted OR for interaction: 1.97, 95% CI: 1.02, 3.82) and mtDNA content with regard to lung cancer risk. We did not find significant modifying effect of p53 codon 72 polymorphisms between mtDNA content and risk of lung cancer. Conclusion. Our study suggested that pack years of smoking and alcohol drinking were functioned as effect modifiers in the relationship between mtDNA content and lung cancer risk. However, due to the dynamics of mtDNA, additional studies with multiple sampling and in larger sample size are warranted to confirm our findings.