Genetic variation in a DNA double strand break repair gene in saudi population: a comparative study with worldwide ethnic groups

Genetic polymorphisms in DNA repair genes and their association with cervical cancer

Background and objective: Carcinoma of cervix is the second most common cancer among women worldwide. The DNA repair network plays an important role in the maintenance of genetic stability, protection against DNA damage and carcinogenesis. Alterations in repair genes XRCC1, XRCC2 and XRCC3 and been reported in certain cancers. We hypothesised an association between XRCC1+399A/G, XRCC2+31467G/A and XRCC3+18067C/T polymorphisms and the risk of cervical cancer. Subjects and methods: This study included 525 subjects (265 controls and 260 cervical cancer cases). Genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Results: Women with GA and AA genotypes of XRCC1+399A/G showed 2.4-3.8 fold higher risk of cervical cancer (P = 0.001). The +399A* allele was significantly linked with cervical cancer (P = 0.002). However, XRCC2+31479G/A and XRCC3+18067C/T polymorphisms did not show any statistically significant associations. Conclusion: The XRCC1+399A/G SNP is linked with cervical cancer. We suggest that this variant can be utilized as a prognostic marker for determination of cervical cancer susceptibility.

Association of DNA repair genes polymorphisms and mutations with increased risk of head and neck cancer: a review

DNA repair mechanisms allow maintain genomic stability and proper functioning within the cells. Any aberrations may cause an increased risk of many diseases such as cancer. The most crucial risk factors for head and neck squamous cell carcinoma are behavioral factors, predominantly chronic exposure to tobacco, alcohol addiction, and infection with human papillomavirus or Epstein–Barr virus. These agents can induce DNA damage; therefore, cells must activate appropriate mechanisms in order to function correctly. Cancer cells are marked with genomic instability, which is associated with a greater tendency for the accumulation of a DNA damage and increased chemo- and radioresistance. Multiple studies have assessed the correlation of increased head and neck cancer (HNC) risk with polymorphism in the DNA repair genes. However, they suggest that interaction of DNA repair genes mutations with susceptibility to HNC depends on a patient’s race and risk factors, especially tobacco smoking. Further identification of these sequence variations must be performed. In this review, we discuss the current knowledge about the DNA repair genes mutations and polymorphisms associated with the high risk of head and neck treatment.

Correlation between selected XRCC2, XRCC3 and RAD51 gene polymorphisms and primary breast cancer in women in Pakistan

Genetic polymorphisms in homologous recombination repair genes cause an abnormal development of cancerous cells. In the present study we evaluated the possibility of breast cancer association with single nucleotide polymorphisms of RAD51, XRCC2 and XRCC3 genes. Polymorphisms selected in this study were RAD51 135G/C, XRCC2 Arg188His; and XRCC3 Thr241Met. Each polymorphism was genotyped using Polymerase chain reaction-restriction fragment length polymorphism in study cohort of 306 females (156 breast cancer patients and 150 controls). We observed that heterozygous variant genotype (GC) of RAD51 135 G/C polymorphism was associated with a significantly (OR=2.70; 95%CI (0.63-1.79); p<0.03) increased risk of breast cancer. In case of the XRCC3 gene we observed that frequency of heterozygous (OR=2.88; 95%CI (1.02-8.14); p<0.02) and homozygous (OR=1.46; 95%CI (0.89-2.40); p<0.04) genotype of Thr241Met polymorphism were significantly higher in breast cancer patients. For the Arg188His polymorphism of XRCC2, ~2fold increase in breast cancer risk (OR=1.6, 95%CI = 0.73-3.50) was associated with GA genotype with a p value for trend of 0.03. Our results suggest that the 135G/C polymorphism of the RAD51, Thr241Met polymorphism of XRCC3 and Arg188His polymorphism of XRCC2 can be independent markers of breast cancer risk in Pakistan.

Molecular Links between Alcohol and Tobacco Induced DNA Damage, Gene Polymorphisms and Patho-physiological Consequences: A Systematic Review of Hepatic Carcinogenesis

Chronic alcohol and tobacco abuse plays a crucial role in the development of different liver associated disorders. Intake promotes the generation of reactive oxygen species within hepatic cells exposing their DNA to continuous oxidative stress which finally leads to DNA damage. However in response to such damage an entangled protective repair machinery comprising different repair proteins like ATM, ATR, H2AX, MRN complex becomes activated. Under abnormal conditions the excessive reactive oxygen species generation results in genetic predisposition of various genes (as ADH, ALDH, CYP2E1, GSTT1, GSTP1 and GSTM1) involved in xenobiotic metabolic pathways, associated with susceptibility to different liver related diseases such as fibrosis, cirrhosis and hepatocellular carcinoma. There is increasing evidence that the inflammatory process is inherently associated with many different cancer types, including hepatocellular carcinomas. The generated reactive oxygen species can also activate or repress epigenetic elements such as chromatin remodeling, non-coding RNAs (micro-RNAs), DNA (de) methylation and histone modification that affect gene expression, hence leading to various disorders. The present review provides comprehensive knowledge of different molecular mechanisms involved in gene polymorphism and their possible association with alcohol and tobacco consumption. The article also showcases the necessity of identifying novel diagnostic biomarkers for early cancer risk assessment among alcohol and tobacco users.