Mitochondrial DNA content and lung cancer risk in Xuan Wei, China.

Smoky coal contains polycyclic aromatic hydrocarbons (PAHs) and has been strongly implicated in etiology of lung cancer in Xuan Wei, China. While PAHs form bulky adducts in nuclear DNA, they have a 40-90-fold greater affinity for mitochondrial DNA (mtDNA). mtDNA content may increase to compensate for mtDNA damage. We conducted a population-based case-control study of lung cancer in Xuan Wei, China hypothesizing that mtDNA content is positively associated with lung cancer risk. Cases (n=122) and controls (n=121) were individually matched on age (+/-2 years), sex, village of residence, and current fuel type. Lifetime smoky coal use and potential confounders were determined with questionnaires. mtDNA was extracted from sputum and mtDNA content was determined with quantitative PCR. ORs and 95% CIs were calculated with unconditional logistic regression. mtDNA content >157 copies per cell was associated with lung cancer risk (OR=1.8; 95% CI=1.0-3.2) compared with those with <or=157 copies. In summary, mtDNA content was positively associated with lung cancer risk. Furthermore, mtDNA content was more strongly associated with lung cancer risk among older individuals. However, due to the small sample size, additional studies are needed to evaluate this potential association.