Single nucleotide polymorphisms of DNA repair genes XRCC1 and XPD and its molecular mapping in Indian oral cancer

Association of betel nut with carcinogenesis: revisit with a clinical perspective

Betel nut (BN), betel quid (BQ) and products derived from them are widely used as a socially endorsed masticatory product. The addictive nature of BN/BQ has resulted in its widespread usage making it the fourth most abused substance by humans. Progressively, several additives, including chewing tobacco, got added to simple BN preparations. This addictive practice has been shown to have strong etiological correlation with human susceptibility to cancer, particularly oral and oropharyngeal cancers.

The PUBMED database was searched to retrieve all relevant published studies in English on BN and BQ, and its association with oral and oropharyngeal cancers. Only complete studies directly dealing with BN/BQ induced carcinogenesis using statistically valid and acceptable sample size were analyzed. Additional relevant information available from other sources was also considered.

This systematic review attempts to put in perspective the consequences of this widespread habit of BN/BQ mastication, practiced by approximately 10% of the world population, on oral cancer with a clinical perspective. BN/BQ mastication seems to be significantly associated with susceptibility to oral and oropharyngeal cancers. Addition of tobacco to BN has been found to only marginally increase the cancer risk. Despite the widespread usage of BN/BQ and its strong association with human susceptibility to cancer, no serious strategy seems to exist to control this habit. The review, therefore, also looks at various preventive efforts being made by governments and highlights the multifaceted intervention strategies required to mitigate and/or control the habit of BN/BQ mastication.

Allelic variants of XRCC1 and XRCC3 repair genes and susceptibility of oral cancer in Brazilian patients

BACKGROUND

The capacity for DNA repair is essential in maintaining cellular functions and homeostasis; however, this capacity can be altered based on DNA sequence variations in DNA repair genes, which may contribute to the onset of cancer. Many single-nucleotide polymorphisms (SNPs) in repair genes have been found to be associated with oral cancer. The aim of this study was to investigate the relationship between the presence of allelic variants Arg194Trp (rs:1799782) and Arg399Gln (rs: 25487) of XRCC1 gene and Thr241Met (rs: 861539) of XRCC3 gene and susceptibility to oral cancer. We also attempted to correlate the frequencies obtained for each of the SNPs to histopathological parameters.

METHODS

A case-control study was conducted with genomic DNA from 150 patients with oral squamous cell carcinomas and 150 controls. SNPs were genotyped by RFLP-PCR.

RESULTS

The presence of the polymorphic variants of the XRCC1 gene within codon 194 (OR 0.82, 95% CI: 0.44-1.51) and codon 399 (OR 0.94, 95% CI: 0.59-1.50) and within the XRCC3 gene (OR 0.72; 95% CI: 0.45-1.16) were not associated with an increased risk of oral cancer. A combinational analysis of SNPs in both genes indicated no association. The presence of the allelic variants of these two genes had no statistically significant effect on tumor differentiation, lymph node invasion or tumor size.

CONCLUSIONS

These results suggest that allelic variants of XRCC1 and XRCC3 are not suitable markers for susceptibility to carcinomas of the oral cavity and are also not related to the later stages of such tumors.

Genetic polymorphisms in key DNA repair genes and risk of head and neck cancer in a Chinese population

Although tobacco and alcohol consumption are the major risk factors of head and neck cancer (HNC), genetic variations of genes involved in several biological pathways, such as DNA repair genes, may affect an individual's susceptibility to HNC. However, few studies have investigated the associations between polymorphisms in DNA repair genes and HNC risk in the Chinese population. Thus, we genotyped five common, non-synonymous single-nucleotide polymorphisms (SNPs) [APEX1 (Asp148Glu), XRCC1 (Arg399Gln), ADPRT (Val762Ala), XPD (Lys751Gln) and XPG (His1104Asp)] in a hospital-based, case-control study of 397 HNC cases and 900 cancer-free controls in China. The results showed that none of the five SNPs in the DNA repair pathway was significantly associated with HNC risk, suggesting that these polymorphisms may not play a major role in HNC susceptibility in this Chinese population.

Multiple pathway-based genetic variations associated with tobacco related multiple primary neoplasms

BACKGROUND

In order to elucidate a combination of genetic alterations that drive tobacco carcinogenesis we have explored a unique model system and analytical method for an unbiased qualitative and quantitative assessment of gene-gene and gene-environment interactions. The objective of this case control study was to assess genetic predisposition in a biologically enriched clinical model system of tobacco related cancers (TRC), occurring as Multiple Primary Neoplasms (MPN).

METHODS

Genotyping of 21 candidate Single Nucleotide Polymorphisms (SNP) from major metabolic pathways was performed in a cohort of 151 MPN cases and 210 cancer-free controls. Statistical analysis using logistic regression and Multifactor Dimensionality Reduction (MDR) analysis was performed for studying higher order interactions among various SNPs and tobacco habit.

RESULTS

Increased risk association was observed for patients with at least one TRC in the upper aero digestive tract (UADT) for variations in SULT1A1 Arg²¹³His, mEH Tyr¹¹³His, hOGG1 Ser³²⁶Cys, XRCC1 Arg²⁸⁰His and BRCA2 Asn³⁷²His. Gene-environment interactions were assessed using MDR analysis. The overall best model by MDR was tobacco habit/p53(Arg/Arg)/XRCC1(Arg³⁹⁹His)/mEH(Tyr¹¹³His) that had highest Cross Validation Consistency (8.3) and test accuracy (0.69). This model also showed significant association using logistic regression analysis.

CONCLUSION

This is the first Indian study on a multipathway based approach to study genetic susceptibility to cancer in tobacco associated MPN. This approach could assist in planning additional studies for comprehensive understanding of tobacco carcinogenesis.

Associated risk of XRCC1 and XPD cross talk and life style factors in progression of head and neck cancer in north Indian population

Effective DNA repair machinery ensures maintenance of genomic integrity. Environmental insults, ageing and replication errors necessitate the need for proper DNA repair systems. Any alteration in DNA repair efficacy would play a dominant role in progression of squamous cell carcinoma of head and neck (SCCHN). Genotypes of XRCC1 gene-Arg194Trp, Arg280His, Arg399Gln and XPD Lys751Gln, by PCR-RFLP were studied in 278 SCCHN patients and an equal number of matched healthy controls residing in north India. In XRCC1 polymorphisms, Arg194Trp and Arg399Gln variants showed a reduced risk, whereas, XPD Lys751Gln variants exhibited ∼2-fold increase in SCCHN risk. With XRCC1-Arg280His variants, there was no association with SCCHN risk. Arg399Gln of XRCC1 appears to have a protective role in people those consume alcohol, while XPD Lys751Gln variants indicated ∼2-fold increased risk of SCCHN in all the co-variate groups. Comparison of gene-gene interaction among XRCC1 Arg280His and XPD Lys751Gln suggested enhanced risk of SCCHN by ∼2.3-fold in group one and ∼6.1-fold in group two. In dichotomized groups of this combination, the risk was ∼2.4 times. Haplotype analysis revealed the frequency of C-G-G-G and C-A-G-G to be significantly associated with an increased risk of SCCHN. On the contrary, T-G-A-A significantly diminished the risk. CART analysis results showed that the terminal node that contains homozygous mutants of XPD Lys751Gln and XRCC1 Arg194Trp, wild type of XRCC1 Arg399Gln and homozygous mutant of XRCC1 Arg280His, represent the highest risk group. Our results demonstrate high degree of gene-gene interaction involving DNA repair genes of NER and BER pathways, namely XRCC1 and XPD. This study amply demonstrates positive association of XPD Arg751Gln polymorphism with an increased risk of SCCHN. Further, XRCC1 Arg280His variant though dormant individually, may also contribute to the development of cancer in combination with XPD Arg751Gln.

Polymorphisms in tobacco metabolism and DNA repair genes modulate oral precancer and cancer risk

The highest rates of oral squamous cell carcinomas are observed in south Asia, particularly in India, where complex forms of tobacco and alcohol exposures exist. Genetic polymorphisms contribute significantly to observed differences in cancer susceptibility. We examined the association of 13 variants in eight genes (rs4646903, rs2031920, rs3813867, GSTM1 null, GSTT1 null, rs1695, rs1138272, rs1799782, rs25487, rs1799791, rs1799793, rs13181 and rs1052133) involved in various stages of tobacco and alcohol metabolism and the risk of leukoplakia and oral cancer (OC) in a case-control study involving 219 oral leukoplakia, 665 OC and 802 age, sex and habit-matched controls. GSTT1 null and rs1695 were inversely associated with oral leukoplakia while GSTM1 null, GSTT1 null, rs2031920, rs3813867 (CYP2E1), and rs13181 were associated with OC. We report that genetic variants associated with premalignant and malignant conditions of the oral cavity differ. The associations appeared to be consistent among smokeless tobacco users, a characteristic risk factor in these parts.

Genetic biomonitoring of inhabitants exposed to uranium in the north region of Brazil

Aiming to assess the susceptibility of populations in the Brazilian Amazon region to ionizing radiation emitted from uranium, mutations frequencies in the DNA repair genes XRCC1 and XRCC3 and in the metabolic gene GSTM1 were evaluated. The XRCC1 allele frequencies for the 194Trp polymorphism in the municipalities of Monte Alegre, Prainha and Alenquer were, respectively, 0.12, 0.13 and 0.07, and for 399Gln polymorphism they were, respectively, 0.28, 0.30 and 0.32. Frequencies for GSTM1 gene deletion homozygotes were, respectively, 0.36, 0.31 and 0.40 for all municipalities. These frequencies are comparable to those described for Brazilian individuals from other regions of the country. Also, allele frequencies of XRCC3 241Met polymorphism of the Monte Alegre and Alenquer populations were 0.28 and 0.33, respectively. In conclusion, frequencies of important polymorphic features of cellular DNA repair and metabolic apparatus in the populations studied do not differ from those of populations in other regions of Brazil.

Interleukin-23 receptor polymorphism as a risk factor for oral cancer susceptibility

BACKGROUND

The purpose of this study was to evaluate the influence of genetic polymorphisms of interleukin (IL)-23 and the IL-23 receptor (IL-23R) on the susceptibility to oral cancer.

METHODS

Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to measure polymorphisms of these genes in 240 controls and 240 patients with oral cancer.

RESULTS

Individuals with at least 1 varied C allele of rs10889677 (IL-23R polymorphism) had a 1.553-fold risk (95% confidence interval [CI], 1.073-2.241) of developing oral cancer compared with patients with the wild-type A/A homozygote. Patients with oral cancer with at least 1 varied C allele of rs10889677 had a 1.931-fold risk of tumor lymph node metastasis compared with patients with the C/C homozygote.

CONCLUSION

The varied C allele of the IL-23R gene may be considered a factor contributing to increased susceptibility and may be a predictive factor for tumor lymph node metastasis in Taiwanese with oral cancer.

Effects of E-cadherin (CDH1) gene promoter polymorphisms on the risk and clinicopathologic development of oral cancer

BACKGROUND

This study investigates the association between polymorphism in the E-cadherin/CDH1 promoter region and the risk and progression of oral cancer.

METHODS

Genetic polymorphisms of CDH1-160 and -347 were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 347 noncancer controls and in 251 patients with oral cancer.

RESULTS

The statistical analysis showed that subjects with at least 1 varied GA allele of CDH1-347 polymorphic genotypes or combinations of the CDH1-160 CA/-347 GGA, CDH1-160 CC/-347 GGA, or CDH1-160 CC/-347 GAGA genotypes had a significantly higher risk, whereas subjects with CDH1-160 C/A or A/A had a significantly lower risk of developing oral cancer than those with wild-type genotypes. Furthermore, elderly patients with the CDH1-347 G/GA or GA/GA genotype were associated with a higher incidence in lymph node metastasis than were those with the G/G genotype.

CONCLUSIONS

These results suggest that CDH1-347 polymorphisms are associated with increased risks of oral cancer, and may be a predictive factor for tumor lymph node metastasis.

DNA repair gene ERCC2 polymorphisms and risk of squamous cell carcinoma of the head and neck

INTRODUCTION

Genetic aberrations of DNA repair enzymes are known to be common events and to be associated with different cancer entities. Aim of the following study was to analyze the genetic association of single nucleotide polymorphisms (SNP) of the DNA repair genes with the risk of squamous cell carcinoma of the head and neck (HNSCC).

MATERIALS AND METHODS

Genetic variants ERCC2 Lys751Gln (rs13181), ERCC2 Asp312Asn (rs1799793), XRCC1 Arg194Trp (rs1799782); XRCC1 Gln399Arg (rs25487), XRCC1 Arg280His (rs25489) and XRCC3 Thr241Met (rs861539) were analyzed in a primary study group comprising 169 patients with histologically confirmed HNSCC and 463 healthy control subjects. Polymorphisms associated with HNSCC were furthermore analyzed in an independent replication study including 125 HNSCC.

RESULTS

Only the ERCC2 751 Gln/Gln genotype was associated with HNSCC in the primary study (p=0.033) and in the replication study (p=0.023), resulting in an overall odds ratio of 0.54 (95% confidence interval 0.35-0.92; p=0.006).

CONCLUSION

Carriers of the homozygous ERCC2 751 Gln/Gln genotype may be at lower risk for HNSCC.

Association of genetic polymorphisms of CXCL12/SDF1 gene and its receptor, CXCR4, to the susceptibility and prognosis of non-small cell lung cancer

BACKGROUND

The aim of this study was to evaluate the relations of chemokine CXCL12, previously known as stromal cell-derived factor-1 (SDF1), and its receptor, CXCR4, gene variants on non-small cell lung cancer (NSCLC) risk and disease severity.

METHODS

Through a case-control study design, genomic DNA samples of 247 NSCLC patients and 328 age and sex-matched controls were subjected to polymerase chain reaction-restriction fragment length polymorphism analysis. The validity of this technique was proven by direct sequencing of amplified products. Statistical analyses were conducted to explore the contribution of polymorphism of the CXCL12/SDF1 gene and CXCR4, in the susceptibility to and prognosis of NSCLC.

RESULTS

Overall, the genotype frequencies of CXCL12/SDF1 gene and CXCR4, were significantly different between lung cancer patients and controls (p<0.0001), and also different between patients with lung cancers of various stages (p<0.0001). Logistic regression analysis revealed that higher odds ratios (ORs) for lung cancer were seen for individuals with CXCL12/SDF1 AA (an OR of 1.95, 95% CI 1.08-3.50, p=0.018), or CXCR4 TT (an OR of 4.71, 95% CI 1.99-11.2, p<0.0001), and for individuals with both CXCL12/SDF1 AA and CXCR4 TT genotypes (an OR of 12.4, 95% CI 1.56-98.3, p=0.002). The patients carrying a homologous AA genotype at CXCL12/SDF1, or a homologous TT genotype at CXCR4, had a tendency to advanced disease and toward poorer prognoses compared with other patients.

CONCLUSION

A significant association between the polymorphisms of CXCL12/SDF1 and CXCR4, and the susceptibility to and prognosis of NSCLC was demonstrated.

Polymorphisms in DNA damage response genes and head and neck cancer risk

BACKGROUND

Polymorphisms in DNA repair genes have been reported contributing factors in head and neck cancer risk but studies have shown conflicting results.

OBJECTIVE

To clarify the impact of DNA repair gene polymorphisms in head and neck cancer risk.

METHOD

A meta-analysis including 30 case-control studies was performed.

RESULTS

Marginally statistically significant association was found for XRCC1 codon 399 (for Caucasians only), XPD Asp312Asn and XRCC1 codon 194 variants and head and neck cancer.

CONCLUSION

Assessments of the effects of smoking, alcohol, human papillomavirus and race/ethnicity on the association between DNA repair gene polymorphisms and head and neck cancer are needed.

Smoking and selected DNA repair gene polymorphisms in controls: systematic review and meta-analysis

BACKGROUND

When the case-only study design is used to estimate statistical interaction between genetic (G) and environmental (E) exposures, G and E must be independent in the underlying population, or the case-only estimate of interaction (COR) will be biased. Few studies have examined the occurrence of G-E association in published control group data.

METHODS

To examine the assumption of G-E independence in empirical data, we conducted a systematic review and meta-analysis of G-E associations in controls for frequently investigated DNA repair genes (XRCC1 Arg399Gln, Arg194Trp, or Arg280His, XPD Lys751Gln, and Asp312Asn, and XRCC3 Thr241Met), and smoking (ever/never smoking, current/not current smoker, smoking duration, smoking intensity, and pack-years).

RESULTS

Across the 55 included studies, single nucleotide polymorphisms SNP-smoking associations in controls (OR(z)) were not reliably at the null value of 1.0 for any SNP-smoking combinations. Two G-E combinations were too heterogeneous for summary estimates: XRCC1 399 and ever-never smoking (N = 21), and XPD 751 and pack-years (N = 12). OR(z) ranges for these combinations were: [OR(z) (95% confidence interval (CI)] 0.7 (0.4, 1.2)-1.9 (1.2, 2.8) and 0.8 (0.5, 1.3)-2.3 (0.8, 6.1), respectively). Estimates for studies considered homogeneous (Cochran's Q P-value <0.10) varied 2- to 5-fold. No study characteristics were identified that could explain heterogeneity.

CONCLUSIONS

We recommend the independence assumption be evaluated in the population underlying any potential case-only study, rather than in a proxy control group(s) or pooled controls.

IMPACT

These results suggest that G-E association in controls may be population-specific. Increased access to control data would improve evaluation of the independence assumption.

Association of DNA repair gene XRCC1 and XPD polymorphisms with genetic susceptibility to gastric cancer in a Chinese population

BACKGROUND

DNA repair gene polymorphisms can contribute to susceptibility of human cancer, including gastric cancer. Three single nucleotide polymorphisms (SNPs) of xeroderma pigmentosum group D (XPD) and X-ray repair cross complement 1 (XRCC1) genes were genotyped in gastric cancer and control subjects in a population from Southwestern China for their association with susceptibility of gastric cancer risk.

METHODS

190 hospital-based cases and 180 matched controls were recruited and blood samples were collected from each of them and amplified with a PCR and DNA sequenced for XPD Asp312Asn, XRCC1 Arg194Trp, and XRCC1 Arg280Gln genotyping.

RESULTS

Allelic association analysis of these three SNPs showed that the frequency of XRCC1 194Trp in gastric cancer case and the control was 17.2% and 7.3%, respectively, which was significantly associated with gastric cancer risk (OR=2.72, 95% CI: 1.04-7.24, p=0.027). Furthermore, XRCC1 194Trp allele increased gastric carcinoma risk in male patients with older age and distant metastasis of gastric cancer. In addition, XRCC1 Trp allele but not XRCC1 Arg allele was closely associated to development of gastric cardia carcinoma. However, other SNPs did not show an association with gastric cancer risk or other clinicopathologic data of the patients.

CONCLUSION

XRCC1 194Trp allele significantly increased the risk of gastric cancer and also associated with risk of gastric cardia carcinoma and promoted distant metastasis of gastric cancer. Future study will verify these findings for use of this SNP as biomarker in gastric cancer.

The association between hypoxia inducible factor-1alpha gene polymorphisms and increased susceptibility to oral cancer

The aim of this study was to estimate the relations between hypoxia inducible factor-1alpha (HIF-1alpha) gene polymorphisms, C1772T and G1790A, to the susceptibility and clinicopathological status of oral cancer. A total of 521 subjects, including 347 controls and 174 oral cancer patients, were recruited in this study and subjected to polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) to analyze the impact of these two polymorphic variants on oral cancer. A significant association between oral cancer susceptibility and G1790A polymorphism was demonstrated since individuals with heterozygotes, that is GA, had a higher risk for oral cancer, compared to GG genotypes after adjusting for other confounders (AOR=3.31; 95%CI=1.27-8.61). Compared to individuals with both C1772C and G1790G homozygotes, individuals with at least one of either C1772T or G1790A of HIF-1alpha gene had a risk of 2.17-folds (95% CI=1.0-4.75) to develop oral cancer. Moreover, results also revealed the presence of synergistic effect between gene polymorphisms of HIF-1alpha and environmental risk factors, such as tobacco and betel nut consumptions while there was no significant association between HIF-1alpha gene polymorphism and clinicopathological parameters of oral cancer. Genetic polymorphism, including C1772T and G1790A, of HIF-1alpha is an important factor for the susceptibility to oral cancer.

Statistically significant association of the single nucleotide polymorphism (SNP) rs13181 (ERCC2) with predisposition to Squamous Cell Carcinomas of the Head and Neck (SCCHN) and Breast cancer in the north Indian population

Background

Non-synonymous single nucleotide polymorphisms (SNPs) within vital DNA repair genes may cause reduction of activity leaving the genome unrepaired resulting in genomic instability and cancer.

Materials and methods

The present endeavour involved study on the association of the SNP rs13181 (Lys751Gln/A18911C) in the Nucleotide Excision Repair (NER) pathway gene ERCC2 (excision repair cross-complementing rodent repair deficiency, complementation group 2) with the risks of Squamous Cell Carcinomas of the Head and Neck (SCCHN) and Breast cancer using a case-control based association study among 685 (400 controls and 285 SCCHN-affected cases) and 395 (227 normal healthy female controls and 168 breast cancer cases) ethnically-matched samples, respectively from north India using Polymerase Chain Reaction followed by Restriction Fragment Length Polymorphism (PCR-RFLP) analysis.

Results

Results showed significant association of rs13181 homozygous mutant (CC) [Odds Ratio (OR) 4.412, 95% Confidence Interval (CI) 2.413 to 8.068], heterozygous (AC) (OR 2.086, 95% CI 1.246 to 3.492) and combined mutant (AC + CC) (OR 2.672, 95% CI 1.647 to 4.334) genotypes with predisposition to Breast cancer. Statistically significant increase in SCCHN risk was also associated with the mutant genotypes of rs13181 (ERCC2), viz. homozygous mutant (CC) (OR 1.680, 95% CI 1.014 to 2.784), heterozygous (AC) (OR 1.531, 95% CI 1.092 to 2.149) and combined mutant (AC + CC) (OR 1.560, 95% CI 1.128 to 2.158) genotypes.

Conclusion

The results of this case-control study indicate that the polymorphism rs13181 might be a risk factor for predisposition towards SCCHN and breast cancer among north Indian subpopulations.

Cytochrome P450 2E1 and head and neck cancer: interaction with genetic and environmental risk factors

The present case-control study investigates the association of polymorphisms in cytochrome P450 2E1 (CYP2E1), involved in the metabolism of tobacco carcinogens and alcohol, with Head and Neck Squamous Cell Carcinoma (HNSCC). In addition, the interaction of CYP2E1 (CYP2E1*5B and CYP2E1*6) with other genetic factors (null genotype of glutathione-S-Transferase M1, GSTM1, X-Ray Repair Cross Complementing Group I, XRCC1 (Arg194Trp), and environmental risk factors such as alcohol and tobacco in modifying HNSCC risk were investigated. Genotypes were determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay in a total of 350 male cases of HNSCC and an equal number of healthy male controls. Statistical analysis showed a significant increase in HNSCC risk in cases with variant genotypes of CYP2E1*5B (RsaI) (O.R. 3.44; 95% C.I. 1.45-8.14) and CYP2E1*6 (DraI) (O.R. 1.76; 95% C.I. 1.28-2.41). Haplotype analysis revealed that haplotype T-A was associated with a greater than 10-fold increase in risk for HNSCC. Our data also revealed a several fold increase in HNSCC risk in cases carrying a combination of variant genotypes of CYP2E1 with the null genotype of GSTM1 or XRCC1 variant genotypes. Alcohol or tobacco use (both smoking and chewing) were also found to interact with variant genotypes of CYP2E1 in significantly enhancing HNSCC risk. This increase in risk associated with an interaction of CYP2E1 genotypes with GSTM1 or XRCC1 or with tobacco and alcohol use demonstrates the importance of gene-gene and gene-environment interactions in the development of HNSCC.

Smoking modifies the relationship between XRCC1 haplotypes and HPV16-negative head and neck squamous cell carcinoma

Reports on the relationship between head and neck squamous cell carcinoma (HNSCC) and polymorphisms in X-ray cross complementing group 1 (XRCC1) have been inconsistent. We hypothesized this may be due to not accounting for Human papillomavirus type-16 (HPV16) and thus examined whether smoking modified the association between XRCC1 haplotypes and HNSCC risk within HPV16 serologic strata. Cases were diagnosed in Greater Boston, Massachusetts. Controls were matched to cases on age, gender and residential town. Genotyping was conducted on three XRCC1 polymorphisms (Arg194Trp, Arg280His and Arg399Gln) and serology was used to determine HPV16 exposure. Unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs), adjusting for age, sex, race, education, smoking, alcohol consumption and HPV16 serology. There was no overall association between XRCC1 polymorphisms and HNSCC risk. Smoking did not modify the association between XRCC1 polymorphisms and HNSCC risk among the HPV16 seropositive (p(interaction) = 0.89) but it did for the HPV16 seronegative (p(interaction)=0.04). Among the HPV16 seronegative, heavy smokers with a haplotype containing a variant allele had an increased HNSCC risk (haplotype with 399Gln: OR, 1.35; 95% CI, 0.97-1.86), whereas never/light smokers with variant alleles may have a reduced risk. In sum, the association between XRCC1 and HNSCC risk differed by HPV16 status and smoking. Among the HPV16 seronegative, heavy smokers with XRCC1 variant alleles had an increased HNSCC risk. There was no relationship between XRCC1 and HPV16-related HNSCC, regardless of smoking. Our findings underscore the importance of accounting for HPV16 exposure even when studying susceptibility to HNSCC.

Chromosome aberrations in workers exposed to organic solvents: Influence of polymorphisms in xenobiotic-metabolism and DNA repair genes

Organic solvents are widely used as diluents or thinners for oil-paints, gasoline and other organic mixtures. We evaluated chromosome aberrations (CAs) in lymphocytes of 200 workers exposed to organic solvents and 200 referents and the influence of polymorphisms in xenobiotic-metabolism (CYP2E1, GSTM1 and GSTT1) and in DNA repair genes (XRCC1(194) Arg/Trp, XRCC1(280) Arg/His, XRCC1(399) Arg/Gln and XRCC3(241) Thr/Met). Polymorphisms were determined by PCR-RFLP. Poisson regression analysis indicates a significant CA frequency increase in exposed workers, representing a higher risk in relation to the matched referent (RR 2.15, 95% CI 1.21-1.53, p<0.001). The CA frequency in exposed workers was influenced by the polymorphic genotypes: GSTM1 null (RR 1.33, 95% CI 1.31-1.69, p<0.001), XRCC1(194) Arg/Trp, Trp/Trp (RR 1.23, 95% CI 1.08-1.40, p<0.001) and by the wild genotypes CYP2E1 C1/C1 (RR 1.20, 95% CI 1.05-1.37, p<0.001), GSTT1 positive (RR 1.49, 95% CI 1.31-1.69, p<0.001), XRCC1(280) Arg/Arg (RR 1.44, 95% CI 1.26-1.64, p<0.001) and XRCC1(241) Thr/Thr (RR 1.54, 95% CI 1.34-1.76, p=0.001). We contribute to the follow-up predictive value of individual susceptibility biomarkers and their CA frequency influence during occupational organic solvent exposure. We provide tools for surveillance and prevention strategies to reduce potential health risks in countries with a large population of car painters not using protection devices and limited organic solvents use control.

Single-nucleotide polymorphisms of DNA repair genes OGG1 and XRCC1: association with gallbladder cancer in North Indian population

BACKGROUND

DNA damage by endogenous or exogenous source of reactive oxygen species (ROS) plays an important role in induction and progression of various cancers. Physiologically, gallbladder is likely to be exposed to various ROS which leads to extensive DNA damage. Cells overcome the DNA damage by repair mechanisms. Genetic variants of OGG1 and XRCC1, important enzymes participating in base excision repair pathway, may confer interindividual variations in susceptibility to gallbladder cancer (GBC). This study was aimed to examine the role of OGG1 Ser326Cys (rs1052133) and XRCC1 Arg194Trp (C > T) (rs25487) and Arg399Gln (G > A) (rs1799782) polymorphisms in GBC susceptibility.

METHODS

The study included 173 GBC patients and 204 controls. Genotyping was done by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method. Differences in the frequencies were estimated by chi-square test and risk was estimated by using unconditional logistic regression after adjusting for age and gender.

RESULTS

OGG1 Cys/Cys genotype frequency was significantly higher in GBC patients [odds ratio (OR) = 2.93; 95% confidence interval (CI) = 1.14-7.51]. The increased risk was more pronounced in female GBC patients (OR = 5.92; 95%CI = 1.20-29.13), patients with gallstone (OR = 5.50; 95%CI = 1.99-15.16), female gender, and late onset of disease (OR = 4.72, 95%CI = 1.43-15.53). In XRCC1 Arg399Gln polymorphism, significant differences in frequencies of Gln/Gln and Arg/Gln genotypes conferred significantly low risk for GBC (OR = 0.62; 95%CI = 0.39-0.97 and OR = 0.37; 95%CI = 0.19-0.71 respectively). However, XRCC1 Arg194Trp polymorphism was not associated with GBC. The carriers of Arg-Gln haplotype consisting of 194Arg and 399Gln alleles of XRCC1 were also at significant low risk for GBC (OR = 0.59, 95%CI = 0.42-0.82). Interaction of genotypes and tobacco usage did not modulate the risk.

CONCLUSION

Results suggest that Cys/Cys genotype of OGG1 Ser326Cys polymorphism is associated with increased risk of GBC. However, Arg399Gln polymorphism and Arg-Gln haplotype comprising XRCC1 Arg194Trp and Arg399Gln polymorphisms conferred low risk for GBC susceptibility.

DNA repair gene XPD and XRCC1 polymorphisms and the risk of childhood acute lymphoblastic leukemia

Polymorphisms have been identified in several DNA repair genes. These polymorphisms may effect DNA repair capacity and modulate cancer susceptibility. In this study, we aimed to determine the four polymorphisms in two DNA repair genes, xeroderma pigmentosum complementation group D (XPD) and X-ray repair cross-complementing group 1 (XRCC1), in a sample of Turkish patients with childhood acute lymphoblastic leukemia (ALL), and evaluate their association with childhood ALL development. We used polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP), to analyze XPD Asp312Asn, XPD Lys751Gln, XRCC1 Arg194Trp, and XRCC1 Arg399Gln polymorphisms in 70 patients with childhood ALL and in 75 disease-free controls, who were of a similar age. No significant differences were observed among the study groups with regard to the XPD codon 312, XPD codon 751, XRCC1 codon 194, and XRCC1 codon 399 polymorphisms. However, the combined XRCC1 Arg194Trp/Trp194Trp variant genotypes were associated with increased risk for ALL in females (OR=5.47; 95% CI=1.49-20.10; p=0.008). This finding indicates that females carrying XRCC1 194Trp allele are at increased risk of developing childhood ALL. These results suggest that the risk of childhood ALL may be associated with DNA repair mechanisms, and understanding these mechanisms will help identify individuals at increased risk of developing childhood ALL, and also should be lead to improved treatment of ALL.

DNA repair gene XPD polymorphisms and cancer risk: a meta-analysis based on 56 case-control studies

Genetic variations in the XPD gene may increase cancer susceptibility by affecting the capacity for DNA repair. Several studies have investigated this possibility; however, the conclusions remain controversial. Therefore, we did a systematic review and executed a meta-analysis to explore the association. From 56 studies, a total of 61 comparisons included 25,932 cases and 27,733 controls concerning the Lys 751Gln polymorphism; 35 comparisons included 16,781 cases and 18,879 controls in the case of Asp 312 Asn were reviewed. In this analysis, small associations of the XPD Lys 751 Gln polymorphism with cancer risk for esophageal cancer [for Lys/Gln versus Lys/Lys: odds ratio (OR), 1.34; 95% confidence interval (95% CI), 1.10-1.64; for Gln/Gln versus Lys/Lys: OR, 1.61; 95% CI, 1.16-2.25] and acute lymphoblastic leukemia (for Gln/Gln versus Lys/Lys: OR, 1.83; 95% CI, 1.21-2.75) are revealed. Overall, individuals with the Gln/Gln genotype have a small cancer risk compared with Lys/Lys genotype for the reviewed cancer in total (OR, 1.10; 95% CI, 1.03-1.16). Subtle but significant cancer risk was observed for the XPD Asp 312 Asn polymorphism in bladder cancer (for Asp/Asn versus Asp/Asp: OR, 1.24; 95% CI, 1.06-1.46). No significant associations were found for other cancers separately and all the reviewed cancer in total assessed for the Asp 312 Asn polymorphism. Our study suggests that XPD is a candidate gene for cancer susceptibility regardless of environmental factors.

Combinational polymorphisms of four DNA repair genes XRCC1, XRCC2, XRCC3, and XRCC4 and their association with oral cancer in Taiwan

BACKGROUND

Many single nucleotide polymorphisms (SNPs) have been found to be associated with oral cancer but the biological interactions through SNPs are seldom addressed. In this study, we focused on the joint effect for SNP combinations of four DNA repair genes, X-ray repair cross-complementing groups (XRCCs) 1-4, involved in major cancer-related pathways.

METHODS

Single nucleotide polymorphism genotyping was determined using by polymerase chain reaction-restriction fragment length polymorphism in this study (case = 103, control = 98). Different numbers of combinational SNPs with genotypes called the pseudo-haplotypes from these chromosome-wide genes were used to evaluate their joint effect on oral cancer risk.

RESULTS

Except for XRCC2 rs2040639-AG, none of these SNPs was found to individually contribute to oral cancer risk. However, for two combined SNPs, the proportion of subjects with oral cancer was significantly higher in the pseudo-haplotype with AG-CC genotypes in rs2040639-rs861539 (XRCC2-XRCC3) compared with those with non-AG-CC genotypes. Similarly, the pseudo-haplotype of rs2040639-rs861539-rs2075685 (XRCC2-XRCC3-XRCC4) and rs2040639-rs861539-rs2075685-rs1799782 (XRCCs 1-4) with specific genotype pattern (AG-CC-TG and CT-AG-CC-TG) among three and four combinational SNPs were significantly associated with oral cancer. After controlling for age, gender, smoking, drinking, and betel nut chewing, the estimated odds ratio of oral cancer were 2.45, 5.03, and 10.10 for two, three and four specific SNP combinations, respectively, comparing these specific pseudo-haplotypes to their corresponding non-pseudo-haplotypes.

CONCLUSION

We have identified the potential combined XRCCs 1-4 SNPs with genotypes that were associated with oral cancer risk and may have an impact on identification of a high-risk population.

Prognostic importance of DNA repair gene polymorphisms of XRCC1 Arg399Gln and XPD Lys751Gln in lung cancer patients from India

PURPOSE

Inter individual variation in lung cancer susceptibility may be modulated in part through genetic polymorphisms in the DNA repair genes, especially the genes involved in the Base Excision Repair (BER) and nucleotide excision repair (NER) pathway. Two of the genetic polymorphisms, XRCC1Arg399Gln and XPD Lys751Gln have been extensively studied in the association with lung cancer risk, although published studies have been inconclusive.

METHODS

In order to verify the role of the common variant alleles in the XPD gene, we have genotyped 211 lung cancer patients and 211 healthy controls using PCR-RFLP assays in a hospital based, case-control study in an Indian population. Logistic regression models were fit to examine the relationship between the log odds of lung cancer and each covariate. Overall Survival in relation to various genotypes and clinicopathological factors were analyzed using Kaplan Meier estimates and hazard ratios were calculated using Cox Regression analysis.

RESULTS

The carriers of XRCC1 399 AA genotypes were at higher risk of lung cancer (OR = 2.1, 95% CI:1.224-3.669, P = 0.007) than carriers of GG genotype. Subjects carrying 751 AC genotype were at an increased risk of carcinoma of the lung (OR = 1.8; 95% CI:1.233-2.807, P = 0.003) than subjects with AA genotypes. Compared to the XRCC1 399 GG/ XPD 751 AA reference genotype, the combined variants, XRCC1 399 GG/ XPD 751 AC+CC (OR = 1.9, 95% CI: 1.037-3.481), P = 0.03), XRCC1 399 GA+AA/ XPD 751 AA (OR = 1.7, 95% CI: 1.020-2.833, P = 0.04), XRCC1 399 GA+AA/XPD 751 AC+CC (OR = 2.7, 95% CI: 1.582-4.864, P = 0.01), had significantly higher odds ratios. Increasing numbers of either XPD or XRCC1 variant alleles were associated with shorter overall survival, the risk being significant for the XRCC1 gene polymorphism (P = 0.01 by log-rank test). The hazard of dying was significant for the XRCC1 399 AA genotype (HR = 3.04, 95%CI: 1.393-6.670, P = 0.005). Higher tumour stage also came out as significant predictors of patient death.

CONCLUSIONS

These findings suggest that genetic polymorphisms in the DNA repair genes may modulate overall lung cancer susceptibility and that pathological stage and XRCC1 Arg399Gln independently predicted overall survival among Indian lung cancer patients.

Genetic polymorphisms in DNA base-excision repair genes ADPRT, XRCC1, and APE1 and the risk of squamous cell carcinoma of the head and neck

BACKGROUND

Tobacco smoke contains numerous carcinogens that cause DNA damage, including oxidative lesions that are removed effectively by the base-excision repair (BER) pathway, in which adenosine diphosphate ribosyl transferase (ADPRT), x-ray repair cross-complementing 1 (XRCC1), and apurinic/apyimidinic endonuclease (APE1) play key roles. Genetic variations in the genes encoding for these DNA repair enzymes may alter their functions. Although there have been several studies that generated mixed results on the association between XRCC1 variants and the risk of squamous cell carcinoma of the head and neck (SCCHN), no reported studies have investigated the association between ADPRT and APE1 variants and SCCHN risk.

METHODS

In a hospital-based, case-control study of 830 non-Hispanic white patients with SCCHN and 854 cancer-free, matched control participants, the authors genotyped the ADPRT alanine 762 valine (Ala762Val) single-nucleotide polymorphism (SNP), the XRCC1 arginine 399 glutamine (Arg399Gln) SNP, and the APE aspartic acid 148 glutamic acid (Asp148Glu) SNP and assessed their associations with the risk of SCCHN in multivariate logistic regression models.

RESULTS

The findings indicated that a significantly decreased risk of SCCHN was associated with the ADPRT 762Ala/Ala genotype (adjusted odds ratio [OR], 0.51; 95% confidence interval [95% CI], 0.27-0.97) and the combined ADPRT 762Ala/Val and Ala/Ala genotypes (OR, 0.79; 95% CI; 0.63-1.00) compared with the ADPRT 762Val/Val genotype, but no altered risk was associated with the XRCC1 Arg399Gln or APE Asp148Glu polymorphisms, and no evidence of interactions was observed between the 3 selected SNPs and age, sex, smoking status, drinking status, or tumor site.

CONCLUSIONS

The ADPRT Ala762Val polymorphism may play a role in the etiology of SCCHN or in linkage disequilibrium with other untyped protective alleles. Larger studies with more SNPs in the BER genes will be needed to verify these findings.

Polymorphisms at XPD and XRCC1 DNA repair loci and increased risk of oral leukoplakia and cancer among NAT2 slow acetylators

Polymorphisms at N-acetyl transferase 2 locus (NAT2) lead to slow, intermediate and rapid acetylation properties of the enzyme. Improper acetylation of heterocyclic and aromatic amines, present in tobacco, might cause DNA adduct formation. Generally, DNA repair enzymes remove these adduct to escape malignancy. But, tobacco users carrying susceptible NAT2 and DNA repair loci might be at risk of oral leukoplakia and cancer. In this study, 389 controls, 224 leukoplakia and 310 cancer patients were genotyped at 5 polymorphic sites on NAT2 and 3 polymorphic sites on each of XRCC1 and XPD loci by PCR-RFLP method to determine the risk of the diseases. None of the SNPs on these loci independently could modify the risk of the diseases in overall population but variant genotype (Gln/Gln) at codon 399 on XRCC1 and major genotype (Lys/Lys) at codon 751 on XPD were associated with increased risk of leukoplakia and cancer among slow acetylators, respectively (OR = 4.2, 95% CI = 1.2-15.0; OR = 1.6, 95% CI = 1.1-2.3, respectively). Variant genotype (Asn/Asn) at codon 312 on XPD was also associated with increased risk of cancer among rapid and intermediate acetylators (OR = 1.9, 95% CI = 1.2-2.9). Variant C-G-A haplotype at XRCC1 was associated with increased risk of leukoplakia (OR = 1.7, 95% CI = 1.2-2.4) but leukoplakia and cancer in mixed tobacco users (OR = 3.1, 95% CI = 1.4-7.1, OR = 2.4, 95% CI = 1.1-5.4, respectively) among slow acetylators. Although none of the 3 loci could modulate the risk of the diseases independently but 2 loci in combination, working in 2 different biochemical pathways, could do so in these patient populations.