Pterygium and genetic polymorphisms of the DNA repair enzymes XRCC1, XPA, and XPD

Purpose: Pterygium is an ultraviolet (UV) related disease. UV radiation can produce DNA damage, which is repaired by the DNA repair systems. Among the DNA repair systems, the base excision repair (BER) and nucleotide excision repair (NER) systems are the major ones involved in repairing UV-induced DNA damage; X-ray repair cross complementary 1 (XRCC1) and human 8-oxoguanine DNA glycosylase 1 (hOGG1) are two BER genes, and xeroderma pigmentosum group A (XPA) and xeroderma pigmentosum group D (XPD) are two NER genes. Polymorphisms of these genes are associated with the differences in their repair DNA damage capacity, and they modulate the susceptibility to cancer. Because the polymorphism of hOGG1 was reported to be associated with pterygium, it is logical to assume the correlation between XRCC1, XPA, and XPD polymorphisms and pterygium formation. Methods: One hundred and twenty-seven pterygium patients and 103 volunteers without pterygium were enrolled in this study. Polymerase chain reaction based analysis was used to resolve the XRCC1 codon 107, 194, 280, and 399; XPA A23G; XPA codon 228; and XPD codon 751 polymorphisms. Results: There were significant differences in the frequency of genotypes and alleles of XRCC1 codon 194 and 399 polymorphisms between the groups. In codon 194, individuals who carried at least 1 Trp allele had a decreased risk of developing pterygium compared to those who carried the Arg/Arg wild-type genotype (odds ratio [OR]=0.58; 95% CI: 0.34-0.98). In codon 399, individuals who carried at least 1 Gln allele had a threefold increased risk of developing pterygium compared to those who carried the Arg/Arg wild-type genotype (OR=3.06; 95% CI: 1.78-5.26). There were no significant differences in the frequency of the genotypes and alleles of XRCC1 codon 107 and 280, XPA A23G, and XPD codon 751 polymorphisms between the groups. The XPA codon 228 polymorphism was not detected in any of the cases or controls. Conclusion: The XRCC1 codon 194 polymorphism causes a decreased risk of developing pterygium, but the codon 399 polymorphism increases the risk. There is no correlation between pterygium and XRCC1 codon 107 and 280, XPA A23G, and XPD codon 751 polymorphisms.