Association between XPD (Lys751G1n) Polymorphism and Lung Cancer Risk: A Population-Based Study in Iran

Objective: People are usually susceptible to carcinogenic aromatic amines, present in cigarrette smoke and polluted environment, which can cause DNA damage. Therefore, maintenance of genomic DNA integrity is a direct result of proper function of DNA repair enzymes. Polymorphic diversity could affect the function of repair enzymes and thus augment the risk of different cancers. Xeroderma pigmentosum group D (XPD) gene encodes one of the most prominent repair enzymes and the polymorphisms of this gene are thought to be of importance in lung cancer risk. This gene encodes the helicase, which is a component of transcription factor IIH and an important part of the nucleotide excision repair system. Studies reveal that individuals with Lys751Gln polymorphism of XPD gene have a low repairing capacity to delete the damages of ultraviolet light among other XPD polymorphisms. Materials and Methods: In this case-control study, first Lys751Gln polymorphism was genotyped, then its association with lung cancer risk was analyzed. Genomic DNA was extracted from the whole blood sample of 640 individuals from Iran (352 healthy individuals and 288 patients). Allele frequencies and heterozygosity of Lys751Gln polymorphism were determined using polymerase chain reaction-restriction fragment length polymorphism method. Results: According to statistical analyses, lung cancer risk in individuals with Lys751Gln polymorphism (Odd Ratio=1.8, 95% Confidence Interval 0.848-3.819) is approximately twice as high as that of Lys/Lys genotype, however 751Gln/Gln genotype did not relate to lung cancer risk (Odd Ratio=0.7, 95% Confidence Interval 0/307-1/595). Conclusion: This study suggests that heterozygous polymorphism (Lys/Gln) increases the sensitivity of lung cancer risk, while homozygous polymorphism (Lys/Lys) probably decreases its risk and C allele frequency shows no remarkable increase in the patients.