Association of genetic polymorphisms in DNA repair pathway genes with non-small cell lung cancer risk

Genetic variation of XPA gene and risk of cancer: a systematic review and pooled analysis

XPA, a zinc-finger DNA-binding protein, play an important role in both global genome and transcription-coupled repair pathways. XPA -4G>A polymorphism was identified in the 5' noncoding region, located four nucleotides upstream of the ATG start codon. Previous studies have shown that this polymorphism may affect mRNA tertiary structure and stability and play a role in susceptibility to cancer. However, the results remained controversial. To derive a more precise estimation of association between this polymorphism and risk of different types of cancer, we performed a meta-analysis based on 36 case-control or case-cohort studies, including a total of 11,700 cases and 15,033 controls. We used odds ratios with 95% confidence intervals to assess the strength of the association. Overall, no significantly elevated cancer risk was found in all genetic models when eligible studies were pooled into the meta-analysis. In the stratified analyses, we found that individuals with A-allele had a higher risk of lung cancer (AA versus GG: OR = 1.25, 95% CI = 1.09-1.43; recessive model: OR = 1.31, 95% CI = 1.16-1.48). When stratified by ethnicity, significantly elevated risks were observed among Asian populations (AA versus GG: OR = 1.31, 95% CI = 1.01-1.70; dominant model: OR = 1.14, 95% CI = 1.00-1.30). This meta-analysis suggests that XPA -4G>A polymorphism is associated with increased lung cancer risk and may be a low-penetrant risk factor in Asian ethnicity for cancer development.

Involvement of MRE11A and XPA gene polymorphisms in the modulation of DNA double-strand break repair activity: a genotype-phenotype correlation study

DNA double-strand breaks (DSB) are the most lethal form of ionizing radiation-induced DNA damage, and failure to repair them results in cell death. In order to see if any associations exist between DNA repair gene polymorphisms and phenotypic profiles of DSB repair (DSBR) we performed a genotype-phenotype correlation study in 118 young healthy subjects (mean age 25.8±6.7years). Subjects were genotyped for 768 single nucleotide polymorphisms (SNPs) with a custom Illumina Golden Gate Assay, and an H2AX histone phosphorylation assay was done to test DSBR capacity. We found that H2AX phosphorylation at 1h was significantly lower in subjects heterozygous (no variant homozygotes were observed) for the XPA gene SNP rs3176683 (p-value=0.005), while dephosphorylation was significantly higher in subjects carrying the variant allele in three MRE11A gene SNPs: rs1014666, rs476137 and rs2508784 (p-value=0.003, 0.003 and 0.008, respectively). An additive effect of low-activity DNA repair alleles was associated with altered DSBR activity, as demonstrated by both H2AX phosphorylation at 1 h (p-trend <0.0001) and γH2AX dephosphorylation at 3h (p-trend <0.0001). Our study revealed that in addition to SNPs of genes that are well-established players in DSBR, non-DSBR genes, such as the XPA gene that is mainly involved in the nucleotide excision repair pathway, can also influence DSBR in healthy subjects. This suggests that successful DSBR may require both DSBR and non-DSBR mechanisms.