DNA Repair Genes XRCC1, XRCC3, XPD, and OGG1 Polymorphisms among the Central Region Population of Saudi Arabia

DNA repair is one of the central defense mechanisms against mutagenic exposures. Inherited SNPs of DNA repair genes may contribute to variations in DNA repair capacity and susceptibility to cancer. Due to the presence of these variants, inter-individual and ethnic differences in DNA repair capacity have been established in various populations. Saudi Arabia harbors enormous genetic and cultural diversity. In the present study we aimed to determine the genotype and allele frequencies of XRCC1 Arg399Gln (rs25487), XRCC3 Thr241Met (rs861539), XPD Lys751Gln (rs13181), and OGG1 Ser326Cys (rs1052133) gene polymorphisms in 386 healthy individuals residing in the central region of Saudi Arabia and compare them with HapMap and other populations. The genotype and allele frequencies of the four DNA repair gene loci in central Saudi population showed a distinctive pattern. Furthermore, comparison of polymorphisms in these genes with other populations also showed a unique pattern for the central Saudi population. To the best of our knowledge, this is the first report that deals with these DNA repair gene polymorphisms among the central Saudi population.

Early-onset of sporadic basal-cell carcinoma: germline mutations in the TP53, PTCH, and XPD genes

BACKGROUND: Basal cell carcinoma (BCC) is the most common non-melanoma skin cancer in the Western world. The objective of this study was to examine together germline mutations in the TP53, PTCH, and XPD genes as risk factors for developing BCC at a young age. We hypothesized that mutations in these genes significantly increase the risk of early-onset BCC (< or = 35 years). METHODS: The PCR, DNA sequencing and Restriction Fragment Length Polymorphisms methods were utilized to study eight Puerto Rican patients with a confirmed diagnosis of BCC before age 35. RESULTS: A novel germline mutation (T:A transversion) was identified at the exon 4, codon 50 of the TP53 gene of one BCC patient. No other mutations were found at the TP53 or PTCH genes. The presence of the XPD mutant allele is associated with a seven-fold increase in risk (OR = 7.0, p = 0.03) for developing BCC prior to age 35. In addition, the DNA Repair Capacity (DRC) of these BCC patients showed a 47% reduction that was significant in relation to age-matched controls (p = 0.021). However, the XPD mutant allele was not associated with the decrease in DRC observed in BCC participants. CONCLUSIONS: The evaluated population presented BCC before age 35, a phenomenon that is so rare as to make very difficult the study of this subpopulation with a larger sample size. The results of this study, suggest that the XPD Lys751Gln polymorphism may have a significant role in the development of early-onset BCC in the Puerto Rican population.

XRCC1 and XPD gene polymorphisms in a South Indian population.

DNA repair systems play an important role in maintaining the integrity of the human genome. Deficiency in the repair capacity due to either mutations or inherited polymorphisms in DNA repair genes may contribute to variations in the DNA repair capacity and subsequently susceptibility to cancer. The interindividual variability as well as ethnic differences in DNA repair polymorphisms, stress the importance to establish genotype profiles unique to a population. Hence the present study aimed to determine the frequencies of XRCC1 and XPD gene polymorphisms in 255 healthy random unrelated individuals from South India. DNA was isolated from the peripheral blood sample of these individuals and the XRCC1 and XPD genotypes were determined by PCR- RFLP with Msp1 and Pst1 enzymes respectively. The XRCC1 genotype frequencies revealed 36% Arg/Arg, 47% Arg/Gln and 17% Gln/Gln with Gln allele frequency of 0.41. Analysis of XPD genotypes revealed 51% Lys/Lys, 41% Lys/Gln and 8% Gln/Gln with Gln allele frequency of 0.29. No significant difference in the distribution of genotypes was seen based on gender. Comparison of the frequencies of XRCC1 and XPD polymorphisms observed in the present study with other populations revealed a distinctive nature of the South Indian population. An understanding of DNA repair gene polymorphisms might not only enable risk assessment of humans exposed to environmental carcinogens but also response to therapy, which target the DNA repair pathway.