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

The association between XPD rs13181 and rs1799793 polymorphism and oral cancer risk: evidence from a meta-analysis

OBJECTIVE

Single nucleotide polymorphisms (SNPs) are common in genes and can lead to dysregulation of gene expression in tissues, which can affect carcinogenesis. Many studies reporting the association between xeroderma pigmentosum group D (XPD) polymorphisms of rs13181 and rs1799793 with oral cancer risk, but with conflicting and inconclusive results.

METHODS

We performed a comprehensive and systematic search through the PubMed, Elsevier, Web of science, and Embase databases, twelve studies were included in the meta-analysis to determine whether XPD rs13181 and rs1799793 polymorphism contributed to the risk of oral cancer.

RESULTS

The pooled date indicated a significant association between the rs13181 polymorphism and oral cancer risk for the allele comparison model (odds ratio, OR = 1.60, 95% confidence intervals, CI = 1.09-2.35, P = 0.02), the dominant model (OR = 1.74, 95% CI = 1.08-2.82, P = 0.02), and the heterozygote model (OR = 1.59, 95% CI = 1.02-2.49, P = 0.04). For the XPD rs1799793 polymorphism, it is not associated with the incidence of oral cancer under any model. Subgroup analyses based on ethnicity indicated that the rs13181 polymorphism increased the risk of oral cancer among Asians according to the allele comparison model (OR = 1.97, 95% CI = 1.10-3.51, P = 0.02), the dominant model (OR = 2.35, 95% CI = 1.25-4.44, P = 0.008), the heterozygote model (OR = 2.05, 95% CI = 1.15-3.66, P = 0.01), and the homozygous model (OR = 2.47, 95% CI = 1.06-5.76, P = 0.04).

CONCLUSION

Our meta-analysis suggests a positive correlation between XPD rs13181polymorphism and the development of oral cancer among Asians, but a negative correlation among Caucasians populations.

Oral mucosa involvement in pediatric patients with xeroderma pigmentosum: a comprehensive review

BACKGROUND

Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder presenting with an inability to repair UV-induced DNA damage. This can lead to the development of neoplasms affecting multiple organ systems, with onset often in childhood. Unfortunately, no cure currently exists for XP, and management strategies focus on sun protection and early intervention for malignancies. Although most skin problems in XP patients are UV induced, various oral lesions are also described. However, the literature has not extensively characterized the oral manifestations and their prognostic significance.

METHODS

We conducted a comprehensive review to evaluate the prevalence and nature of oral mucosal lesions in pediatric XP patients.

RESULTS

Our literature search yielded 130 pediatric XP patients with oral involvement and 210 associated tumoral or non-tumoral lesions. Squamous cell carcinoma was the most common type of oral mucosal tumor reported, with other malignancies including basal cell carcinoma, melanoma, angiosarcoma, fibrosarcoma, and trichilemmal carcinoma.

CONCLUSION

Given the potential morbidity and mortality associated with oral mucosal tumors in XP patients, our study aims to raise awareness of these manifestations. Early diagnosis and treatment are crucial for managing these lesions effectively, and routine oral exams should be considered a critical component of dermatological evaluations for XP patients, especially in the pediatric age group.

Is Systemic Immunosuppression a Risk Factor for Oral Cancer? A Systematic Review and Meta-Analysis

Even if the relationship between immunosuppression and increased incidence of systemic cancers is well known, there is less awareness about the risk of developing oral cancer in immunosuppressed patients. The aim of this review was to evaluate the association between immunosuppression and the development of oral cancer. Two authors independently and, in duplicate, conducted a systematic literature review of international journals and electronic databases (MEDLINE via OVID, Scopus, and Web of Science) from their inception to 28 April 2023. The assessment of risk of bias and overall quality of evidence was performed using the Newcastle-Ottawa Scale and GRADE system. A total of 2843 articles was identified, of which 44 met the inclusion criteria and were included in either the qualitative or quantitative analysis. The methodological quality of the included studies was generally high or moderate. The quantitative analysis of the studies revealed that immunosuppression should be considered a risk factor for the development of oral cancer, with a percentage of increased risk ranging from 0.2% to 1% (95% CI: 0.2% to 1.4%). In conclusion, the results suggest that a constant and accurate follow-up should be reserved for all immunosuppressed patients as a crucial strategy to intercept lesions that have an increased potential to evolve into oral cancer.

The XRCC1 Arg194Trp polymorphism was associated with the risk of head and neck squamous cell carcinoma development: Results from a systematic review and meta-analysis

BACKGROUND

The X-ray repair cross complementing group 1 (XRCC1) is a DNA repair gene. Various studies have examined the association between XRCC1 Arg194Trp polymorphism and head and neck squamous cell carcinoma (HNSCC) susceptibility with contradictory results. So, this systematic review and meta-analysis aimed to assess whether variants of this polymorphism increase the HNSCC risk or not.

RECENT FINDINGS

Thirty three studies consisting of 14282 subjects (6012 cases and 8270 controls) were included in this meta-analysis. Variants of XRCC1 Arg194Trp polymorphism were associated with increased HNSCC risk and the associations were significant based on heterozygous and dominant models (heterozygous model: OR = 1.182, 95%CI = 1.015-1.377, P = 0.032; homozygous model: OR = 1.274, 95%CI = 0.940-1.727, P = 0.119; dominant model: OR = 1.194, 95%CI = 1.027-1.388, P = 0.021; recessive model: OR = 1.181, 95%CI = 0.885-1.576, P = 0.119). There were significant associations between variants of this polymorphism and HNSCC risk based on Asian ethnicity under dominant model, hospital control source under different genetic models, PCR-RFLP genotyping method under dominant model and oral cavity tumor site under heterozygous and dominant models.

OBJECTIVE

The X-ray repair cross complementing group 1 (XRCC1) is a DNA repair gene. Various studies have examined the association between XRCC1 Arg194Trp polymorphism and head and neck squamous cell carcinoma (HNSCC) susceptibility with contradictory results. So, this systematic review and meta-analysis aimed to assess whether variants of this polymorphism increase the HNSCC risk or not.

METHODS

A systematic search of the literatures published till April 2022 was conducted using Google Scholar, Scopus, PubMed, Web of Science, Cochrane Library and Embase databases. The heterogeneity was assessed with the I-Square statistic. A random effects model or fixed effects model was used to analyze the data. Data were reported by odds ratio (OR) and 95% confidence interval (CI). The p value was considered significant if p < .05.

RESULTS

Thirty three studies consisting of 14 282 subjects (6012 cases and 8270 controls) were included in this meta-analysis. Variants of XRCC1 Arg194Trp polymorphism were associated with increased HNSCC risk and the associations were significant based on heterozygous and dominant models (heterozygous model: OR = 1.182, 95%CI = 1.015-1.377, p = .032; homozygous model: OR = 1.274, 95%CI = 0.940-1.727, p = .119; dominant model: OR = 1.194, 95%CI = 1.027-1.388, p = .021; recessive model: OR = 1.181, 95%CI = 0.885-1.576, p = .119). There were significant associations between variants of this polymorphism and HNSCC risk based on Asian ethnicity under dominant model, hospital control source under different genetic models, PCR-RFLP genotyping method under dominant model and oral cavity tumor site under heterozygous and dominant models.

CONCLUSION

Variants of XRCC1 Arg194Trp polymorphism were significantly associated with increased risk of HNSCC development based on heterozygous and dominant genetic models.

Association Between X-Ray Repair Cross-Complementing Group 1 Arg399Gln Polymorphism and Risk of Oral Leukoplakia: A Meta-analysis

Aims: Previous studies have have reported inconsistent results regarding the association of the XRCC1 polymorphism Arg399Gln with oral leukoplakia (OLK) risk. This study was designed to assess the existing evidence of this association using a meta-analytic approach. Materials and Methods: The literature was searched using multiple databases, including PubMed, EMBASE, and China National Knowledge Infrastructure (CNKI), through October 22, 2020. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to evaluate the strength of any associations. Results: A total of 671 Indian cases and 1009 Indian controls from seven case-control studies were included in the meta-analysis. The overall analysis revealed that the AA genotype was associated with a significantly increased OLK risk compared with the GG+GA genotypes (OR = 1.51, 95% CI = 1.10-2.06). In the subgroup analysis stratified by tobacco use, a significant association was found in the mixed group (OR = 1.51, 95% CI = 1.12-2.56), but not in the tobacco-using group or the no tobacco use group. In the OLK subtype subgroup analysis, a significantly increased risk was found in the hyperplastic subgroup (OR = 5.01, 95% CI = 1.39-18.11), whereas no associations were found in the dysplastic or mixed subgroups. Conclusions: The results of this meta-analysis suggest that the XRCC1 Arg399Gln polymorphism may significantly contribute to susceptibility to OLK in the Indian population.

The Association Between the XRCC1 Arg399Gln Polymorphism and the Risk of Head and Neck Cancer: An Updated Meta-Analysis Including 14586 Subjects

BACKGROUND

Accumulated evidence shows that DNA repair gene X-ray repair cross complementing group 1 (XRCC1) may determine individual susceptibility to head and neck cancer (HNC) as a major DNA repair gene. However, the results from previous studies have been conflictive and inconsistent. In order to more accurately estimate and integrate the association between XRCC1 Arg399Gln polymorphism and HNC risk, we conducted a meta-analysis including 14586 subjects.

METHODS

In this meta-analysis, literatures were collected up until September 15, 2020 through multifarious retrieval strategies by searching through electronic databases of PubMed, Cochrane Library, EMBASE, Medline, Web of Science and CNKI. The association between the XRCC1 Arg399Gln polymorphism and HNC was analyzed through calculating summary odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

Thirty-one studies consisting of 6025 cases and 8561 controls were identified and analyzed. No significant association between XRCC1 Arg399Gln polymorphisms and HNC risk was found under the allelic (OR = 0.94, 95% CI: 0.82-1.07, P = 0.35), homozygous (OR = 0.99, 95% CI: 0.81-1.21, P = 0.91), heterozygous (OR = 1.01, 95% CI: 0.90-1.13, P = 0.91), dominant (OR = 1.05, 95% CI: 0.85-1.29, P = 0.67) or recessive (OR = 0.93, 95% CI: 0.80-1.08, P = 0.35) genetic models in the overall comparison. In addition, subgroup analyses according to tumor site also displayed no significant association between XRCC1 Arg399Gln polymorphisms and HNC risk. However, subgroup analyses based on ethnicity indicated that HNC risk was significantly related to Arg399Gln genetic heterozygous model (OR = 1.21, 95%CI: 1.04-1.42, P = 0.02) and dominant model (OR = 1.27, 95%CI: 1.02-1.60, P = 0.04) in Caucasians populations.

CONCLUSION

The results from this meta-analysis suggest that the XRCC1 Arg399Gln variants (Arg/Gln and Arg/Arg+Arg/Gln) may contribute to high HNC risk among Caucasians. Further well-designed studies and larger sample sizes are needed to validate our findings.

Cooperation between oncogenic Ras and wild-type p53 stimulates STAT non-cell autonomously to promote tumor radioresistance

Oncogenic RAS mutations are associated with tumor resistance to radiation therapy. Cell-cell interactions in the tumor microenvironment (TME) profoundly influence therapy outcomes. However, the nature of these interactions and their role in Ras tumor radioresistance remain unclear. Here we use Drosophila oncogenic Ras tissues and human Ras cancer cell radiation models to address these questions. We discover that cellular response to genotoxic stress cooperates with oncogenic Ras to activate JAK/STAT non-cell autonomously in the TME. Specifically, p53 is heterogeneously activated in Ras tumor tissues in response to irradiation. This mosaicism allows high p53-expressing Ras clones to stimulate JAK/STAT cytokines, which activate JAK/STAT in the nearby low p53-expressing surviving Ras clones, leading to robust tumor re-establishment. Blocking any part of this cell-cell communication loop re-sensitizes Ras tumor cells to irradiation. These findings suggest that coupling STAT inhibitors to radiotherapy might improve clinical outcomes for Ras cancer patients.

Relationship of the XRCC1 rs25487 polymorphism with demographic, behavioral, clinical, and histological parameters in oral potentially malignant disorders and oral squamous cell carcinoma in a Colombian population

OBJECTIVES

To evaluate the salivary detection of XRCC1 rs25487 single-nucleotide polymorphism (SNP), its relationship with clinicopathological characteristics, and the interactions with demographic/behavioral variables in the etiopathogenesis of oral potentially malignant disorders (OPMD) and oral squamous cell carcinoma (OSCC) in a Colombian population.

METHODS

Demographic/behavioral data and saliva samples were obtained from patients with oral leukoplakia (OL, n = 17) and oral lichenoid lesions with epithelial dysplasia (OLL-ED, n = 10), or OSCC (n = 45), along with healthy controls (n = 40). Tissue biopsies were obtained for histological assessment and genetic analysis was performed using polymerase chain reaction-restriction fragment length polymorphism. Descriptive analyses were used to compare the distribution of genotypes/alleles between study groups alongside an analysis of the interaction between genetic findings and demographic/behavioral variables.

RESULTS

No association was observed between the genotype and allele frequencies in OPMD or OSCC. The AG genotype was significantly more frequent in OL with high-grade dysplasia, acanthotic epithelial lining, moderate-to-severe mitotic count, and negative-to-mild apoptotic count; and in OSCC cases with stage III/IV, poorly differentiated, perineural/lymphovascular invasion, severe cellular atypia, moderate-to-severe mitotic count, and negative-to-mild apoptotic counts. Significant interaction effects were detected in the AG genotype with regard to ageing, smoking habits, and alcohol consumption in both OL and OSCC.

CONCLUSION

Although rs25487 SNP appeared to not modulate the risk of OPMD/OSCC independently, its significant association with clinicopathological characteristics in OL and OSCC, and the synergistic interaction between ageing and smoking/alcohol consumption, might play a role in these two diseases.

New Insights Into Oral Squamous Cell Carcinoma: From Clinical Aspects to Molecular Tumorigenesis

Oral squamous cell carcinoma (SCC) is a prevalent malignant disease worldwide, especially so in Taiwan. Early- or even preclinical-stage detection is critical for reducing morbidity and mortality from oral SCC. Epidemiological and genome association studies are useful for identifying clinicopathological risk factors for preventive, diagnostic, and therapeutic approaches of oral SCC. For advanced oral SCC, effective treatments are critical to prolonging survival and enhancing quality of life. As oral SCC is characteristic of regional invasion with lymph node metastases, understanding the aggressive features of oral SCC, particularly in lymphangiogenesis, is essential for determining effective treatments. Emerging evidence has demonstrated that the tumor microenvironment (TME) plays a pivotal role in tumor growth, invasion, and metastases. Recent clinical successes in immune checkpoint inhibitors either alone or combined with chemotherapy have also supported the therapeutic value of immunotherapy in oral SCC. This review summarizes critical advances in basic knowledge of oral SCC from the perspective of clinicopathological risk factors, molecular tumorigenesis, and the TME. We also highlight our recent investigations on the microbiome, genome association studies, lymphangiogenesis, and immunomodulation in oral SCC. This review may provide new insights for oral SCC treatment by systematically interpreting emerging evidence from various preclinical and clinical studies.

A PRISMA-compliant meta-analysis on association between X-ray repair cross complementing (XRCC1, XRCC2, and XRCC3) polymorphisms and oral cancer susceptibility

BACKGROUND

Oral Cancer (OC) is one of the leading causes of death and the disease mainly occurs over 50 years of age. Herein, a meta-analysis aimed to assess the association between X-ray repair cross complementing (XRCC) polymorphisms and OC risk.

METHODS

Four databases were searched extensively until June 5, 2020. Subgroup analysis, meta-regression, and funnel plots, as well as the quality assessment were estimated.

RESULTS

Fifteen studies were entered to the analysis. With regards to allele, homozygote, heterozygote, recessive, and dominant models, the pooled ORs for XRCC1 rs1799782 polymorphism were 1.51 (P = 0.01), 1.45 (P = 0.11), 1.45 (P = 0.0003), 1.44 (P = 0.0002), and 1.29 (P = 0.26); for XRCC1 rs1799782 polymorphism were 1.65 (P = 0.11), 1.50 (P = 0.33), 1.06 (P = 0.83), 1.57 (P = 0.12), and 1.32 (P = 0.45); for XRCC1 rs25489 polymorphism were 0.01 (P = 0.19), 1.44 (P = 0.48), 1.21 (P = 0.72), 1.17 (P = 0.19), and 1.38 (P = 0.54); for XRCC2 rs2040639 polymorphism were 0.68 (P = 0.0002), 0.63 (P = 0.02), 0.95 (P = 0.92), 0.79 (P = 0.49), and 0.61 (P = 0.005); and for XRCC3 rs861539 polymorphism were 1.24 (P = 0.20), 1.28 (P = 0.48), 0.99 (P = 0.95), 1.15 (P = 0.46), and 1.52 (P = 0.15), respectively.

CONCLUSIONS

The T allele and CT genotype of XRCC1 rs1799782 polymorphism had an elevated risk, whereas the G allele and GG genotype of XRCC2 rs2040639 polymorphism had a protective role in OC.

Effect of Arg399Gln single-nucleotide polymorphism in XRCC1 gene on survival rate of Indian squamous cell head-and-neck cancer patients

Background

Head-and-neck squamous cell carcinoma (HNSCC) is one of the most common cancers that contribute to 20%-40% of all cancer incidences in India. Indian patients with HNSCC are mostly associated with tobacco usage and may have different genetic alterations compared with Western patients who are mostly associated with human papillomavirus infection. Polymorphisms in DNA repair genes are correlated to individuals' susceptibility and progression of cancer. XRCC1 is a DNA repair enzyme.

Materials and Methods

In the present prospective study, Indian population of HNSCC patients (n = 45) were screened for Arg399Gln variant of XRCC1 using polymerase chain reaction-restriction fragment length polymorphism technique, prospective evaluation of the patients was done after treatment, and the single-nucleotide polymorphism results were correlated to survival functions.

Results

Out of 45 patients, 28 patients were Arg/Arg, 12 patients were Arg/Gln, and 5 patients were Gln/Gln. Overall survival for the entire cohort and Arg/Arg, Arg/Gln, and Gln/Gln cohort was 36.3 (95% confidence interval [CI]: 33-39.5), 38.6 (95% CI: 35.3-41.9), 35.8 (95% CI: 28.6-42.9), and 26.4 (95% CI: 13.7-39.1) months (P = 0.097), respectively. Progression-free survival (PFS) of the entire patient cohort and Arg/Arg, Arg/Gln, and Gln/Gln cohort was 35.2 (95% CI: 31.4-39.1), 38.2 (95% CI: 34.3-42.1), 32.7 (95% CI: 26.2-39.1), and 22.3 (95% CI: 9.4-35.3) (P = 0.061), respectively.

Conclusions

This study suggests that HNSCC patients with Gln substitution in place of Arg at position 399 (both homozygous and heterozygous) in XRCC1 protein have significantly inferior survival functions, higher recurrence rate, and events after radical treatment.

Genetic Variant XRCC1 rs1799782 (C194T) and Risk of Cancer Susceptibility in Indian Population: A Meta-analysis of Case-Control Studies

X-ray repair cross-complementing group 1 (XRCC1) plays a key role in the base excision repair pathway, as a scaffold protein that brings together proteins of the DNA repair complex. Several studies have reported contradictory results for XRCC1 exon 6 C>T (rs1799782) gene polymorphism and cancer risk in Indian population has provided inconsistent results. Therefore, we have performed this meta-analysis to evaluate the relationship between XRCC1 exon 6 C>T gene polymorphism and risk of cancer by published studies. We searched PubMed and Google scholar web databases to cover all studies published on association between XRCC1 exon 6 C>T gene polymorphism and cancer risk. The meta-analysis was carried out and pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were used to appraise the strength of association. In order to derive a more precise estimation of the association, A total of 3197 confirmed cancer cases and 3819 controls were included from eligible seventeen case-controls studies. Results from overall pooled analysis demonstrated suggested that that variant allele (T vs. C: OR 1.301, 95% CI 1.003-1.688, p = 0.047) was associated with the risk of overall cancer. Other genetic models; heterozygous (TC vs. CC: OR 1.108, 95% CI 0.827-1.485, p = 0.491), homozygous (TT vs. CC: OR 1.479, 95% CI 0.877-2.493, p = 0.142), dominant (TT+TC vs. CC: OR 1.228, 95% CI 0.899-1.677, p = 0.196) and recessive (TT vs. TC+CC: OR 1.436, 95% CI 0.970-2.125, p = 0.071) did not reveal statistical association. Publication bias observation was also considered and none was detected during the analysis. The present meta-analysis suggested that the variant allele T of XRCC1 exon 6 gene polymorphism was associated with the risk of cancer. It is therefore pertinent to confirm this finding in a large sample size to divulge the mechanism of this polymorphism and cancer risk in Indian population.

Single nucleotide polymorphisms as markers of genetic susceptibility for oral potentially malignant disorders risk: Review of evidence to date

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We reviewed single nucleotide polymorphisms for oral pre-cancer susceptibility.

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All of them were pathway based candidate gene association studies.

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The current level of evidence is very limited.

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Integrated characterization of germline/somatic alterations in oral cancer & pre-cancer is needed.

Background

Oral cancers are preceded by oral potentially malignant disorders (OPMD). Understanding genetic susceptibility for OPMD risk could provide an opportunity for risk assessment of oral cancer through early disease course. We conducted a review of single nucleotide polymorphism (SNP) studies for OPMD risk.

Methods

We identified all relevant studies examining associations of SNPs with OPMD (leukoplakia, erythroplakia and oral sub-mucous fibrosis) conducted world-wide between January, 2000 and February, 2016 using a combined keyword search on PubMed. Of these, 47 studies that presented results as odds ratios and 95% CI were considered for full review.

Results

The majority of eligible studies that explored candidate gene associations for OPMD were small (N < 200 cases), limiting their scope to provide strong inference for any SNP identified to date in any population. Commonly studied SNPs were genes of carcinogen metabolism (n = 18 studies), DNA repair (n = 11 studies), cell cycle control (n = 8 studies), extra-cellular matrix alteration (n = 8 studies) and immune-inflammatory (n = 6 studies) pathways. Based on significant associations as reported by two or more studies, suggestive markers included SNPs in GSTM1 (null), CCND1 (G870A), MMP3 (-1171; promotor region), TNFα (-308; rs800629), XPD (codon 751) and Gemin3 (rs197412) as well as in p53 (codon 72) in Indian populations. However, an equal or greater number of studies reported null or mixed associations for SNPs in GSTM1 (null), p53 (codon 72), XPD (codon 751), XRCC (rs25487 C/T), GSTT1 (null) and CYP1A1m1 (MspI site).

Conclusion

Candidate gene association studies have not yielded consistent data on risk loci for OPMD. High-throughput genotyping approaches for OPMD, with concurrent efforts for oral cancer, could prove useful in identifying robust risk-loci to help understand early disease course susceptibility for oral cancer.

Effect of Polymorphisms in XRCC1, CCND1 and GSTM1 and Tobacco Exposure as Risk Modifier for Oral Leukoplakia

Analysis of gene-environment interactions may help to define the risk of oral leukoplakia. We hypothesized that an individual's susceptibility to leukoplakia is dependent on interactions between polymorphic genotypes at susceptible loci and tobacco exposure. To test this hypothesis, the relationship between tobacco use and polymorphisms in 3 genes that might contribute to variance in individuals′ susceptibility to the risk of leukoplakia was determined. In this case-control study, polymorphic genotypes in XRCC1 (399Gln), a DNA repair gene involved in removing DNA adducts, CCND1 (G870A), a key component of cell cycle regulation, and GSTM1 (null genotype), a xenobiotic-metabolizing enzyme involved in the metabolism of tobacco carcinogens, were analyzed in 100 oral leukoplakia patients and age- and gender-matched controls by PCR using genomic DNA isolated from blood. The GSTM1 null genotype was associated with a 1.6-fold increased risk of developing leukoplakia. The risk conferred by the CCND1 GA+AA variant was 2.4-fold that of the GG genotype. Importantly, among non-users of tobacco, the XRCC1 (GA+AA) variant emerged as the most significant determinant of an individual's susceptibility to leukoplakia (OR=3.5). In GSTM1 null individuals, tobacco consumption increased the risk of leukoplakia 21.3 fold. Similarly, XRCC1 A allele carriers and CCND1 A allele carriers who consumed tobacco were at a significantly high risk of developing leukoplakia (OR=11.8 and 14.9, respectively). Our study provides evidence that tobacco use in individuals harboring these polymorphic genotypes elevates the risk of oral leukoplakia and warrants further studies on gene-environment interactions to define the risk of malignant transformation of leukoplakia.

Role of Genetic Variations in Determining Treatment Outcome in Head and Neck Cancer

Worldwide, head and neck squamous cell carcinoma (HNSCC) is responsible for >550,000 diagnoses and 380,000 deaths annually. It originates in the upper aerodigestive tract and has a multifactorial origin involving both genetic and lifestyle risk factors. The clinical management of HNSCC involves surgery, radiotherapy, and chemotherapy. Several studies point to the role of genetic variations in predicting drug efficacy and toxicity. Cancer pharmacogenomics has fast emerged as a new and promising field for the early identification of genetic markers that can predict drug response or toxicity, with the number of studies of genetic polymorphisms as prognostic factors of HNSCC treatment outcomes growing. The number of studies evaluating the association of candidate polymorphisms in drug-metabolising Phase I and II enzymes with treatment outcome far exceed the studies involving other candidate genes, such as those involved in drug metabolism, DNA repair, and cell cycle regulation. This review focusses on the relevance of genetic variations in genes, where the corresponding gene products play an important role in drug metabolism (TPMT, DPD), DNA repair (X-ray repair cross complementing 1), cell cycle (tumour protein P53), and carcinogenesis (matrix metalloproteinase 3 and 7), thereby contributing to the treatment outcome for HNSCC. This could greatly help clinicians in identifying genetic markers useful for the selection of optimal drugs, dose, and treatment duration on an individual basis, resulting in improved drug efficacy and decreased toxicity. However, further studies are needed in well characterised and larger HNSCC populations with proper validation of pharmacogenetic markers in experimental settings before application in clinical routine diagnostics.

Genetic Variant Arg399Gln G>A of XRCC1 DNA Repair Gene Enhanced Cancer Risk Among Indian Population: Evidence from Meta-analysis and Trial Sequence Analyses

The X-ray repair cross-complementation group 1 (XRCC1) gene plays an important role in base excision repair pathway. Several studies have reported contradictory results for XRCC1 exon 10 (Arg399Gln, G23990A, rs25487) gene polymorphism and cancer risk in Indian population, making it difficult to interpret them. Therefore, we have conducted a meta-analysis to evaluate the more precise association between XRCC1 exon 10 G>A gene polymorphism and risk of cancer by published studies. We searched PubMed (Medline) and Google scholar web databases to cover all studies published on association between XRCC1 exon 10 G>A gene polymorphism and cancer risk until August 2016. Pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were used to appraise the strength of association. Heterogeneity, publication bias and sensitivity analysis were also assessed. Twenty-five published studies had fulfilled the inclusion criteria comprising 4131 confirmed cancer cases and 5013 controls. When all studies were polled together, overall significant association was found between XRCC1 exon 10 G>A polymorphism and cancer risk in variant allele carrier (A vs. G: OR 1.217, 95% CI 1.056-1.402, p = 0.007), homozygous (AA vs. GG: OR 1.359, 95% CI 1.036-1.783, p = 0.027), dominant (AA+AG vs. GG OR 1.208, 95% CI 1.006-1.450, p = 0.043) and recessive (AA vs. AG+GG: OR 1.315, 95% CI 1.029-1.680, p = 0.029) genetic models. Further sensitivity analysis supported the stability of our result by showing similar ORs before and after removal of a single study. The present meta-analysis suggested that the XRCC1 exon 10 G>A polymorphism contribute cancer risk in Indian population, and supports that individuals with risk allele A and AA genotype are at higher risk of developing cancer.

Single nucleotide polymorphisms in an Indian cohort and association of CNTN4, MMP2 and SNTB1 variants with oral cancer

Oral cancer is a high incidence cancer in India primarily due to the prevalent tobacco/areca nut chewing habits and hence a major health concern. India constitutes 26% of the global oral cancer burden. Besides the well-established risk factors, the genomic constitution of an individual plays a role in oral cancer. The aim of the current study was to analyse genomic variants represented as single nucleotide polymorphisms (SNPs), analyse their prevalence and investigate risk association of allelotypes/genotypes to oral cancers. Eleven SNPs in genes associated with biological functions were analysed in an Indian cohort (n = 1000) comprising 500 oral cancer patients and 500 long term tobacco habitués as controls, using Allelic discrimination Real-Time PCR assay with SYBR Green dye. Fisher's exact test and Odds Ratio were used for statistical analysis. Increased risk was observed for rs9849237 CC [P = 0.008; OR 1.412 (1.09-1.82)] and rs243865 CT [P = 0.004; OR 1.469 (1.13-1.90)] genotypes, whereas rs9849237 CT [P = 0.034; OR 0.755 (0.58-0.97)], rs243865 CC [P = 0.002; OR 0.669 (0.51-0.86)] and rs10090787 CC [P = 0.049; OR 0.774 (0.60-0.99)] genotypes indicated decreased risk to oral cancer. The other SNPs showed equidistribution in both groups. Our data indicated genotypes and alleles in specific SNPs rs9849237, rs243865 and rs10090787 with increased/decreased risk to oral cancer.

Increased expression of ERCC2 gene in head and neck cancer is associated with aggressive tumors: a systematic review and case-control study

INTRODUCTION

The excision repair cross-complementation group 2 (ERCC2) ATP-dependent helicase is an essential member of the DNA repair pathway. It has been observed to be differentially expressed in different cancers, which shows its involvement in carcinogenesis.

AIM

In the present study we have tried to determine the association of expression patterns of this gene with head and neck carcinogenesis.

METHOD

We first carried out a systematic review of the available studies on the role of ERCC2 in head and neck cancer (HNC). In order to test the hypothesis that the expression patterns of XPD/ERCC2 play a critical role in HNC pathogenesis, we then conducted a population based case-control study on 81 head and neck tumor samples and adjacent normal-tissue control samples. Reverse transcriptase polymerase chain reaction (RT-PCR) and quantitative polymerase chain reaction (qPCR) were used to assess ERCC2 deregulation at the mRNA level.

RESULT

Expression analysis showed that the ERCC2 expression level was significantly upregulated (p<0.05) in HNC tissues compared with adjacent normal tissues. Furthermore, the expression pattern of ERCC2 was correlated with the expression pattern of Ki-67 and a significant correlation (r = 0.230, p<0.03) was observed between ERCC2 and Ki-67. Spearman's correlation also showed a significant correlation between ERCC2 expression and tumor stage (r = 0.271, p<0.02) and grade (r = 0.228, p<0.02) of HNC.

CONCLUSIONS

Our data suggest that deregulation of ERCC2 in HNC has the potential to predict a more aggressive cancer phenotype and may be considered a possible biomarker for improved diagnosis and prognosis of HNC.

A systematic gene-gene and gene-environment interaction analysis of DNA repair genes XRCC1, XRCC2, XRCC3, XRCC4, and oral cancer risk

Oral cancer is the sixth most common cancer worldwide with a high mortality rate. Biomarkers that anticipate susceptibility, prognosis, or response to treatments are much needed. Oral cancer is a polygenic disease involving complex interactions among genetic and environmental factors, which require multifaceted analyses. Here, we examined in a dataset of 103 oral cancer cases and 98 controls from Taiwan the association between oral cancer risk and the DNA repair genes X-ray repair cross-complementing group (XRCCs) 1-4, and the environmental factors of smoking, alcohol drinking, and betel quid (BQ) chewing. We employed logistic regression, multifactor dimensionality reduction (MDR), and hierarchical interaction graphs for analyzing gene-gene (G×G) and gene-environment (G×E) interactions. We identified a significantly elevated risk of the XRCC2 rs2040639 heterozygous variant among smokers [adjusted odds ratio (OR) 3.7, 95% confidence interval (CI)=1.1-12.1] and alcohol drinkers [adjusted OR=5.7, 95% CI=1.4-23.2]. The best two-factor based G×G interaction of oral cancer included the XRCC1 rs1799782 and XRCC2 rs2040639 [OR=3.13, 95% CI=1.66-6.13]. For the G×E interaction, the estimated OR of oral cancer for two (drinking-BQ chewing), three (XRCC1-XRCC2-BQ chewing), four (XRCC1-XRCC2-age-BQ chewing), and five factors (XRCC1-XRCC2-age-drinking-BQ chewing) were 32.9 [95% CI=14.1-76.9], 31.0 [95% CI=14.0-64.7], 49.8 [95% CI=21.0-117.7] and 82.9 [95% CI=31.0-221.5], respectively. Taken together, the genotypes of XRCC1 rs1799782 and XRCC2 rs2040639 DNA repair genes appear to be significantly associated with oral cancer. These were enhanced by exposure to certain environmental factors. The observations presented here warrant further research in larger study samples to examine their relevance for routine clinical care in oncology.

Polymorphism of the DNA base excision repair genes in keratoconus

Keratoconus (KC) is a degenerative corneal disorder for which the exact pathogenesis is not yet known. Oxidative stress is reported to be associated with this disease. The stress may damage corneal biomolecules, including DNA, and such damage is primarily removed by base excision repair (BER). Variation in genes encoding BER components may influence the effectiveness of corneal cells to cope with oxidative stress. In the present work we genotyped 5 polymorphisms of 4 BER genes in 284 patients and 353 controls. The A/A genotype of the c.–1370T>A polymorphism of the DNA polymerase γ (POLG) gene was associated with increased occurrence of KC, while the A/T genotype was associated with decreased occurrence of KC. The A/G genotype and the A allele of the c.1196A>G polymorphism of the X-ray repair cross-complementing group 1 (XRCC1) were associated with increased, and the G/G genotype and the G allele, with decreased KC occurrence. Also, the C/T and T as well as C/C genotypes and alleles of the c.580C>T polymorphism of the same gene displayed relationship with KC occurrence. Neither the g.46438521G>C polymorphism of the Nei endonuclease VIII-like 1 (NEIL1) nor the c.2285T>C polymorphism of the poly(ADP-ribose) polymerase-1 (PARP-1) was associated with KC. In conclusion, the variability of the XRCC1 and POLG genes may play a role in KC pathogenesis and determine the risk of this disease.

Association between the XRCC1 Arg194Trp polymorphism and risk of cancer: evidence from 201 case-control studies

The Arg194Trp polymorphism in the X-ray cross-complementing group 1 (XRCC1) had been implicated in cancer susceptibility. The previous published data on the association between XRCC1 Arg194Trp polymorphism and cancer risk remained controversial. Hence, we performed a meta-analysis to investigate the association between cancer susceptibility and XRCC1 Arg194Trp (59,227 cases and 81,587 controls from 201 studies) polymorphism in different inheritance models. We used odds ratios with 95 % confidence intervals to assess the strength of the association. Overall, significantly increased cancer risk was found (recessive model: (odds ration [OR] = 1.18, 95% confidence interval [CI] = 1.09-1.27; homozygous model: OR = 1.21, 95% CI = 1.10-1.33; additive model: OR = 1.05, 95% CI = 1.01-1.09) when all eligible studies were pooled into the meta-analysis. In further stratified and sensitivity analyses, significantly increased glioma risk was found among Asians, significantly decreased lung cancer risk was found among Caucasians, and significant increased breast cancer risk was found among hospital-based studies. In summary, this meta-analysis suggests that Arg194Trp polymorphism may be associated with increased breast cancer risk, Arg194Trp polymorphism is associated with increased glioma risk among Asians, and Arg194Trp polymorphism is associated with decreased lung cancer risk among Caucasians. In addition, our work also points out the importance of new studies for Arg194Trp association in some cancer types, such as gastric, pancreatic, prostate, and nasopharyngeal cancers, where at least some of the covariates responsible for heterogeneity could be controlled, to obtain a more conclusive understanding about the function of the XRCC1 Arg194Trp polymorphism in cancer development (I (2) > 75%).

The XRCC1 Arg194Trp and Arg280His polymorphisms in head and neck cancer susceptibility: a meta-analysis

The XRCC1 Arg194Trp and Arg280His polymorphisms are likely to be implicated with the development of head and neck cancer. However, studies of association have been inconsistent. This meta-analysis of the available literature was performed to make a more precise estimation of the risk associated with these polymorphisms. A comprehensive literature search was conducted to identify all case-control studies of the XRCC1 Arg194Trp and Arg280His polymorphisms in head and neck cancer. Summary odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of association. A total of 20 eligible studies were selected for this meta-analysis, including 3,362 cases and 5,796 controls for the XRCC1 Arg194Trp polymorphism and 1,932 cases and 2,757 controls for the XRCC1 Arg280His polymorphism. Overall, no significant associations were found in all genetic models when the studies were pooled into the meta-analysis for the Arg194Trp and Arg280His polymorphisms. When stratified by ethnicity, significant associations were found for Arg194Trp polymorphism in CT vs CC (OR = 1.26, 95% CI = 1.05-1.52) and the recessive model (OR = 1.28, 95% CI = 1.07-1.53) in Asian population, and no significant associations were found in non-Asian population in all genetic models. This meta-analysis suggests that the XRCC1 Arg194Trp polymorphism is a risk factor for head and neck cancer in Asian populations.

Combined effect of tobacco and DNA repair genes polymorphisms of XRCC1 and XRCC2 influence high risk of head and neck squamous cell carcinoma in northeast Indian population

Tobacco consumption in various forms is one of the major risk factor for the development of head and neck squamous cell carcinoma. Polymorphisms in XRCC1 and XRCC2 genes may alter an individual's susceptibility to tobacco-related cancers. Here, we have investigated the interaction of XRCC1 (Arg399Gln) and XRCC2 (Arg188His) polymorphism and tobacco exposure in the progression of HNSCC in northeast Indian population. The population-based case-control study includes 110 HNSCC patients and 140 controls. The polymorphisms of XRCC1 and XRCC2 were studied by means of PCR-RFLP, and the results were confirmed by DNA sequencing. Smokers and tobacco-betel quid chewers were significantly higher in cases (P = 0.045 and 0.033). The variant homozygote AA genotype of XRCC1 Arg399Gln and heterozygote GA genotype of XRCC2 Arg188His has an increased risk toward HNSCC (OR 2.43; P = 0.031 and OR 3.29; P < 0.01, respectively). The interaction between tobacco-betel quid chewing and variant genotypes of XRCC1 and XRCC2 resulted in several fold increase the risk of HNSCC, when compared to non-chewers. Heavy smokers carrying XRCC1 AA and XRCC2 GA genotypes had a significantly higher risk of HNSCC compared to never smokers (P = 0.017 and 0.003, respectively). Upon gene-gene interaction analysis, individuals carrying both XRCC1 GA (Arg/Gln) and XRCC2 GA (Arg/His) genotypes had the highest risk of HNSCC (P = 0.001).Our finding suggests that interaction of tobacco and polymorphisms of XRCC1 and XRCC2 increases the risk of HNSCC. Furthermore, cross talk between these two DNA repair genes might modulate susceptibility toward HNSCC.

The effect of XPD polymorphisms on digestive tract cancers risk: a meta-analysis

Background

The Xeroderma pigmento-sum group D gene (XPD) plays a key role in nucleotide excision repair. Single nucleotide polymorphisms (SNP) located in its functional region may alter DNA repair capacity phenotype and cancer risk. Many studies have demonstrated that XPD polymorphisms are significantly associated with digestive tract cancers risk, but the results are inconsistent. We conducted a comprehensive meta-analysis to assess the association between XPD Lys751Gln polymorphism and digestive tract cancers risk. The digestive tract cancers that our study referred to, includes oral cancer, esophageal cancer, gastric cancer and colorectal cancer.

Methods

We searched PubMed and EmBase up to December 31, 2012 to identify eligible studies. A total of 37 case-control studies including 9027 cases and 16072 controls were involved in this meta-analysis. Statistical analyses were performed with Stata software (version 11.0, USA). Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of the association.

Results

The results showed that XPD Lys751Gln polymorphism was associated with the increased risk of digestive tract cancers (homozygote comparison (GlnGln vs. LysLys): OR = 1.12, 95% CI = 1.01–1.24, P = 0.029, P_{heterogeneity} = 0.133). We found no statistical evidence for a significantly increased digestive tract cancers risk in the other genetic models. In the subgroup analysis, we also found the homozygote comparison increased the susceptibility of Asian population (OR = 1.28, 95% CI = 1.01–1.63, P = 0.045, P_{heterogeneity} = 0.287). Stratified by cancer type and source of control, no significantly increased cancer risk was found in these subgroups. Additionally, risk estimates from hospital-based studies and esophageal studies were heterogeneous.

Conclusions

Our meta-analysis suggested that the XPD 751Gln/Gln genotype was a low-penetrate risk factor for developing digestive tract cancers, especially in Asian populations.

Association between the XRCC1 Arg399Gln polymorphism and head and neck cancer susceptibility: a meta-analysis based on case-control studies

Published data regarding the association between the XRCC1 Arg399Gln polymorphism and head and neck cancer (HNC) susceptibility showed inconsistent results. This meta-analysis of eligible literatures was performed to draw a more precise estimation of the relationship. We systematically searched PubMed, Embase, and Web of Science with a time limit of Oct 28, 2013. Summary odds ratios (ORs) with 95% CIs were used to assess the strength of association between XRCC1 Arg399Gln polymorphism and HNC susceptibility using random-effect model. A total of 27 case-control studies including 5942 cases and 9041 controls were included for analysis. Meta-analysis of total studies showed that the XRCC1 Arg399Gln variant carriers were not susceptible to HNC (AA vs. GG: OR=0.92, 95% CI=0.77-1.11; AG vs. GG: OR=1.05, 95% CI=0.76-1.44; the dominant model AA+AG vs. GG: OR=1.00, 95% CI=0.78-1.29; the recessive model AA vs. AG+GG: OR=0.91, 95% CI=0.71-1.16). Further, subgroup analyses by ethnicity and source of controls did not identify any significant associations of XRCC1 Arg399Gln polymorphism with head and neck susceptibility in any populations. Our meta-analysis suggested that the XRCC1 Arg399Gln polymorphism was not a risk factor for HNC susceptibility.

Association of X-ray repair cross-complementing group 1 Arg194Trp, Arg399Gln and Arg280His polymorphisms with head and neck cancer susceptibility: a meta-analysis

Background

Previous studies on the association of X-ray repair cross-complementing group 1 (XRCC1) Arg194Trp, Arg399Gln, and Arg280His polymorphisms with head and neck cancer (HNC) have produced inconsistent results. The aim of the present study was to evaluate the effects of these three polymorphic variants on HNC risk.

Methods

The PubMed and EMBASE databases were searched for genetic association studies on the XRCC1 Arg194Trp, Arg399Gln, and Arg280His polymorphisms and HNC risk. (The most recent search was conducted on 20 August, 2013.) Twenty-six studies were identified and meta-analysis was performed to evaluate the association between the polymorphism and HNC by calculating combined odds ratios and 95% confidence intervals.

Results

No significant association was found under the allelic, homozygous, heterozygote, and dominant genetic models in the overall comparison. Further, no significant association between the XRCC1 Arg399Gln and Arg280His polymorphisms and HNC risk was detected under the four genetic models in subgroup analyses based on ethnicity, cancer site, and whether or not the studies had been adjusted for cigarette smoking and alcohol. However, in stratified analyses based on cancer site, a significant association was found between the XRCC1 Arg194Trp polymorphism and oral cancer under the allelic, heterozygote, and dominant models. The XRCC1 Arg194Trp polymorphism was significantly associated with HNC risk in studies that were adjusted for smoking and alcohol under the homozygous and heterozygote models.

Conclusion

The meta-analysis results suggest that the XRCC1 Arg399Gln and Arg280His polymorphisms are probably not associated with the risk of HNC, but the XRCC1 Arg194Trp polymorphism was associated with increased risk of HNC in the subgroup analysis of studies adjusted for smoking and alcohol and with increased risk of oral cancer in the stratified analyses based on cancer site. Further studies with larger samples are needed to confirm these findings.

Association of XPD Lys751Gln polymorphism with head and neck cancer susceptibility: evidence from 11,443 subjects

BACKGROUND

Whether the single nucleotide polymorphism (SNP) Lys751Gln of xeroderma pigmentosum group D(XPD) gene increases susceptibility to head and neck cancer (HNC) is controversial and undetermined. Therefore, we conducted this meta-analysis to systematically assess the possible association between them.

METHODS

The OVID, Medline, Embase, Pubmed, Web of Science databases were searched to identify the eligible studies. The odds ratio (OR) with 95% confidence interval (95% CI) were used to assess the strength of association.

RESULTS

A total of 11,443 subjects from eighteen studies were subjected to meta-analysis. Overall, XPD Lys751Gln polymorphism had no association with increased HNC risk under all five genetic models (P > 0.05). In the subgroup analysis by ethnicity and source of controls, still no significant association was found under five genetic models (P > 0.05). In the subgroup analysis by cancer type, XPD Lys751Gln polymorphism had statistically significant association with elevated laryngeal cancer (LC) and nasopharyngeal cancer (NPC) risk under heterozygous comparison and dominant model (P<0.05) and borderline significantly increased risk was found under allele contrast for LC and NPC. Carriers of Lys allele and Lys/Lys genotype may be associated with elevated LC and NPC risk.

CONCLUSIONS

There is overall lack of association between XPD Lys751Gln polymorphism and HNC risk under all five genetic models and still no significant association was found in the subgroup analysis by ethnicity and source of controls. However, XPD Lys751Gln polymorphism was significantly associated with susceptibility to LC and NPC and the Lys allele and Lys/Lys genotype of XPD Lys751Gln polymorphism may be a risk factor for LC and NPC. However, relatively modest sample sizes were included in this meta-analysis and studies with large sample sizes and representative population are warranted to further clarify this finding.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/5628716106316015.

Meta-analysis on the association of nucleotide excision repair gene XPD A751C variant and cancer susceptibility among Indian population

Polymorphism A751C (A>C) in XPD gene has shown susceptibility to many cancers in Indian population; however the results of these studies are inconclusive. Thus, we performed this meta-analysis to estimate the association between XPD A751C polymorphism and overall cancer susceptibility. We quantitavely synthesized all published studies of the association between XPD A751C polymorphism and cancer risk. Pooled odds ratios (ORs) and 95 % CI were estimated for allele contrast, homozygous, heterozygous, dominant and recessive genetic model. A total of thirteen studies including 3,599 controls and 3,087 cancer cases were identified and analyzed. Overall significant results were observed for C allele carrier (C vs. A: p = 0.001; OR 1.372, 95 % CI 1.172-1.605) variant homozygous (CC vs. AA: p = 0.001; OR 1.691, 95 % CI 1.280-2.233) and heterozygous (AC vs. AA: p = 0.001; OR 1.453, 95 % CI 1.215-1.737) genotypes. Similarly dominant (CC+AC vs. AA: p = 0.001; OR 1.512, 95 % CI 1.244-1.839) and recessive (CC vs. AA+AC: p = 0.001; OR 1.429, 95 % CI 1.151-1.774) genetic models also demonstrated risk of developing cancer. This meta-analysis suggested that XPD A751C polymorphism likely contribute to cancer susceptibility in Indian population. Further studies about gene-gene and gene-environment interactions are required.

Association between polymorphisms in ERCC2 gene and oral cancer risk: evidence from a meta-analysis

Background

Excision repair cross-complementing group 2 (ERCC2) plays important roles in the repair of DNA damage and adducts. Single nucleotide polymorphisms (SNPs) of ERCC2 gene are suspected to influence the risks of oral cancer. We performed a meta-analysis to systematically summarize the possible association of ERCC2 rs1799793 and rs13181 polymorphisms with oral cancer risks.

Methods

We retrieved the relevant articles from PubMed and Embase databases. Studies were selected using specific criteria. ORs and 95% CIs were calculated to assess the association. All analyses were performed using the Stata software.

Results

Six studies were included in this meta-analysis. There were no significant associations between ERCC2 rs1799793 and rs13181 polymorphism with overall oral cancer risk. In the stratified analysis by ethnicity, no significant associations were found. In the stratified analysis by tumor type, the risk of oral leukoplakia was significant associated with rs13181 polymorphism (AC vs. AA: OR = 1.28, 95% CI = 1.01-1.62, P = 0.546 for heterogeneity, I² = 0.0%; CC vs. AA: OR = 1.94, 95% CI = 0.99-3.79, P = 0.057 for heterogeneity, I² = 60.1%; dominant model AC + CC vs. AA: OR = 1.35, 95% CI = 1.08–1.69, P = 0.303 for heterogeneity, I² = 17.6%; allele C vs. A: OR = 1.38, 95% CI = 1.04–1.82. P = 0.043 for heterogeneity, I² = 56.4%).

Conclusion

Rs13181 in ERCC2 gene might be associated with oral leukoplakia risk.

Polymorphisms in human DNA repair genes and head and neck squamous cell carcinoma

Genetic polymorphisms in some DNA repair proteins are associated with a number of malignant transformations like head and neck squamous cell carcinoma (HNSCC). Xeroderma pigmentosum group D (XPD) and X-ray repair cross-complementing proteins 1 (XRCC1) and 3 (XRCC3) genes are involved in DNA repair and were found to be associated with HNSCC in numerous studies. To establish our overall understanding of possible relationships between DNA repair gene polymorphisms and development of HNSCC, we surveyed the literature on epidemiological studies that assessed potential associations with HNSCC risk in terms of gene-environment interactions, genotype-induced functional defects in enzyme activity and/or protein expression, and the influence of ethnic origin on these associations.We conclude that large, well-designed studies of common polymorphisms in DNA repair genes are needed. Such studies may benefit from analysis of multiple genes or polymorphisms and from the consideration of relevant exposures that may influence the likelihood of HNSCC when DNA repair capacity is reduced.

Association of XRCC1 genetic polymorphism (Arg399Gln) with laryngeal cancer: a meta-analysis based on 4,031 subjects

Several case-control studies on the relation between XRCC1 gene Arg399Gln polymorphism and laryngeal cancer do not have similar conclusions. To further evaluate the relation between the XRCC1 gene Arg399Gln polymorphism and laryngeal cancer, we selected seven case-control studies related to the XRCC1 gene Arg399Gln polymorphism and laryngeal cancer by searching MEDLINE, EMBase, Chinese Biomedical Literature Database, Chinese CNKI, and Wanfang database. We utilized Q test and I (2) test to test the heterogeneity between each study. The fixed effects model was utilized to calculate the odds ratio (OR) and 95 % confidence interval. The present study included 1,654 patients with laryngeal cancer and 2,377 cancer-free control subjects. By meta-analysis, we did not find any association of XRCC1 gene Arg399Gln polymorphism with laryngeal cancer (OR = 1.13, 95 % CI 0.81-1.58, P = 0.47). Therefore, we concluded that XRCC1 gene Arg399Gln polymorphism was not associated with laryngeal cancer.

Genome stability pathways in head and neck cancers

Genomic instability underlies the transformation of host cells toward malignancy, promotes development of invasion and metastasis and shapes the response of established cancer to treatment. In this review, we discuss recent advances in our understanding of genomic stability in squamous cell carcinoma of the head and neck (HNSCC), with an emphasis on DNA repair pathways. HNSCC is characterized by distinct profiles in genome stability between similarly staged cancers that are reflected in risk, treatment response and outcomes. Defective DNA repair generates chromosomal derangement that can cause subsequent alterations in gene expression, and is a hallmark of progression toward carcinoma. Variable functionality of an increasing spectrum of repair gene polymorphisms is associated with increased cancer risk, while aetiological factors such as human papillomavirus, tobacco and alcohol induce significantly different behaviour in induced malignancy, underpinned by differences in genomic stability. Targeted inhibition of signalling receptors has proven to be a clinically-validated therapy, and protein expression of other DNA repair and signalling molecules associated with cancer behaviour could potentially provide a more refined clinical model for prognosis and treatment prediction. Development and expansion of current genomic stability models is furthering our understanding of HNSCC pathophysiology and uncovering new, promising treatment strategies.

A self-assembled deoxyribonucleic acid concatemer for sensitive detection of single nucleotide polymorphism

Polymerase-free and label-free strategies for DNA detection have shown excellent sensitivity and specificity in various biological samples. Herein, we propose a method for single nucleotide polymorphism (SNP) detection by using self-assembled DNA concatemers. Capture probes, bound to magnetic beads, can joint mediator probes by T4 DNA ligase in the presence of target DNA that is complementary to the capture probe and mediator probe. The mediator probes trigger self-assembly of two auxiliary probes on magnetic beads to form DNA concatemers. Separated by a magnetic rack, the double-stranded concatemers on beads can recruit a great amount of SYBR Green I and eventually result in amplified fluorescent signals. In comparison with reported methods for SNP detection, the concatemer-based approach has significant advantages of low background, simplicity, and ultrasensitivity, making it as a convenient platform for clinical applications. As a proof of concept, BRAF(T1799A) oncogene mutation, a SNP involved in diverse human cancers, was used as a model target. The developed approach using a fluorescent intercalator can detect as low as 0.1 fM target BRAF(T1799A) DNA, which is better than those previously published methods for SNP detection. This method is robust and can be used directly to measure the BRAF(T1799A) DNA in complex human serum with excellent recovery (94-103%). It is expected that this assay principle can be directed toward other SNP genes by simply changing the mediator probe and auxiliary probes.

DNA repair gene XRCC1 polymorphisms and head and neck cancer risk: an updated meta-analysis including 16344 subjects

BACKGROUND

DNA repair gene X-ray repair cross complementing group 1 (XRCC1) plays an important role in the maintenance of the genomic integrity and protection of cells from DNA damage. Sequence variation in XRCC1 gene may alter head and neck cancer (HNC) susceptibility. However, these results are inconclusive. To derive a more precise estimation of the relationship between XRCC1 polymorphism and HNC risk, we undertook a meta-analysis involving 16,344 subjects.

METHODS

A search of the literature by PubMed, Embase, Web of Science and China National Knowledge Infrastructure was performed to identify studies based on the predetermined inclusion criteria. The odds ratio (OR) with 95% confidence interval (CI) was combined using a random-effects model or a fixed-effects model.

RESULTS

Twenty-nine studies consisting of 6,719 cases and 9,627 controls were identified and analyzed. Overall, no evidence of significant association was observed between XRCC1 Arg194Trp, XRCC1 Arg280His, XRCC1 Arg399Gln genotypes and the risk of HNC in any genetic models. Subgroup analyses according to ethnicity, tumor site, publication year, genotyping method also detected no significant association in any subgroup, except that oral cancer was associated with Arg194Trp variant in recessive model. Furthermore, no significant effect of these polymorphisms interacted with smoking on HNC risk was detected but Arg194Trp homozygous variant.

CONCLUSION

In conclusion, this meta-analysis suggests that the XRCC1 Arg194Trp, Arg280His and Arg399Gln polymorphism may not involve in HNC susceptibility. Further studies about gene-gene and gene-environment interactions in different populations are required.

DNA repair gene polymorphisms and risk of head and neck cancer in the Tunisian population

Altered activity of DNA repair enzymes may be involved in modulating cancer susceptibility and pathogenesis of head and neck cancer (HNC). We conducted a case-control study to test the association between three common single-nucleotide polymorphisms of XRCC1, ERCC2, and ERCC3 genes with HNC risk in Tunisian patients. To the best of our knowle dge, this is the first report on polymorphisms in XRCC1, ERCC2, and ERCC3 and susceptibility to HNC in our population. The genotype analyses of XRCC1 Arg399Gln, ERCC2 Lys751Gln, and ERCC3 7122 A>G polymorphisms for 169 HNC patients, and 261 controls were performed using the PCR-based restriction fragment length polymorphism. Stratification of the populations according to smoking and drinking habits and occupational exposure highlighted the importance of tobacco, alcohol, and toxic substance as three risk co-factors for the development of HNC. Our study suggests that only the XRCC1 Arg399Gln polymorphism was associated with the risk of HNC in the Tunisian population (OR = 2.04; P = 0.001). Furthermore, the risk of HNC was associated with XRCC1 Arg399Gln polymorphism stratified by occupational exposure status (OR = 2.29; P = 0.024). However, no statistically significant association was observed between the risk of developing HNC and the ERCC2 Lys751Gln and ERCC3 A>G polymorphisms. These data suggest that the XRCC1 Arg399Gln polymorphism is associated with an increased risk of developing HNC, because it correlates with occupational exposure in Tunisian population.

Single-nucleotide polymorphisms in nucleotide excision repair genes, cigarette smoking, and the risk of head and neck cancer

BACKGROUND

Cigarette smoking is associated with increased head and neck cancer (HNC) risk. Tobacco-related carcinogens are known to cause bulky DNA adducts. Nucleotide excision repair (NER) genes encode enzymes that remove adducts and may be independently associated with HNC, as well as modifiers of the association between smoking and HNC.

METHODS

Using population-based case-control data from the Carolina Head and Neck Cancer Epidemiology (CHANCE) Study (1,227 cases and 1,325 controls), race-stratified (White, African American), conventional, and hierarchical logistic regression models were used to estimate ORs with 95% intervals (I) for the independent and joint effects of cigarette smoking and 84 single-nucleotide polymorphisms (SNP) from 15 NER genes on HNC risk.

RESULTS

The odds of HNC were elevated among ever cigarette smokers and increased with smoking duration and frequency. Among Whites, rs4150403 on ERCC3 was associated with increased HNC odds (AA+AG vs. GG; OR, 1.28; 95% CI, 1.01-1.61). Among African Americans, rs4253132 on ERCC6 was associated with decreased HNC odds (CC+CT vs. TT; OR, 0.62; 95% CI, 0.45-0.86). Interactions between ever cigarette smoking and three SNPs (rs4253132 on ERCC6, rs2291120 on DDB2, and rs744154 on ERCC4) suggested possible departures from additivity among Whites.

CONCLUSIONS

We did not find associations between some previously studied NER variants and HNC. We did identify new associations between two SNPs and HNC and three suggestive cigarette-SNP interactions to consider in future studies.

IMPACT

We conducted one of the most comprehensive evaluations of NER variants, identifying a few SNPs from biologically plausible candidate genes associated with HNC and possibly interacting with cigarette smoking.

XRCC1 Arg194Trp polymorphism is associated with oral cancer risk: evidence from a meta-analysis

Previous studies show that X-ray cross-complementing group 1 (XRCC1) Arg194Trp may result in variations in host's repair efficiency of DNA damage, and this repair deficit may eventually cause individual susceptibility to oral cancer. However, published data regarding the association between XRCC1 Arg194Trp polymorphism and oral cancer risk were contradictory. The aim of this study was to derive a more precise estimation of the association of XRCC1 Arg194Trp polymorphism with oral cancer by performing a meta-analysis. Odds ratios (ORs) and 95 % confidence intervals (95 % CIs) were used to assess the strength of the association. Finally, a meta-analysis of nine eligible studies including 1,281 cases and 1,966 controls was performed. Overall, there was a significant association between XRCC1 Arg194Trp polymorphism and oral cancer risk (for Trp versus Arg: OR = 1.41, 95 % CI 1.08-1.83, P = 0.01; for TrpTrp versus ArgArg: OR = 1.50, 95 % CI 1.00-2.30, P = 0.05; for TrpTrp/ArgTrp versus ArgArg: OR = 1.49, 95 % CI 1.14-1.94, P = 0.003). After excluding those studies containing patients with oral leukoplakia, there was still an obvious association between XRCC1 Arg194Trp polymorphism and oral cancer risk (for TrpTrp/ArgTrp versus ArgArg: OR = 1.40, 95 % CI 1.14-1.71, P = 0.001). Subgroup analysis by ethnicity suggested that there was an obvious association between XRCC1 Arg194Trp polymorphism and oral cancer risk in Asians under three genetic models. In conclusion, the results from this meta-analysis suggest that XRCC1 Arg194Trp polymorphism is associated with oral cancer risk, especially in Asians.

Genetic polymorphisms of CYP2E1 and DNA repair genes HOGG1 and XRCC1: association with hepatitis B related advanced liver disease and cancer

A population based case-control study was designed to explore the genetic risk factors for hepatitis B virus (HBV) related liver disease susceptibility. A total of 424 subjects comprising 210 controls, 50 acute HBV (AVH), 84 chronic HBV (CHBV), 25 HBV related cirrhosis and 55 HBV related hepatocellular carcinoma (HCC) cases were included in the study. PCR-RFLP was used for the genotyping of Cyp2E1*5B, hOGG1 codon 326 and XRCC1 codon 399. Compared to controls, Cyp2E1 rsaI variant c2 genotype increased the risk of HBV related liver disease severity by 2.68 fold, the highest for HCC cases (3.981 folds, p=0.106); and was associated with higher histology activity index (HAI) (p<0.001) in CHBV patients. Cyp2E1 and hOGG1 variants were independently associated with a significantly higher fibrosis score in CHBV group. Analysis of gene-gene interaction studies showed an increased risk of HCC, cirrhosis and CHBV in a Cyp2E1 variant+XRCC1 variant combination (p<0.001); and hOGG1 variants+XRCC1 variants. A mutually independent heterozygous hOGG1 and XRCC1 combination resulted in a decreased risk of HBV related liver disease. On the other hand, a wild-type hOGG1 and XRCC1 combination was associated with a significantly higher risk of AVH (p=0.010) but a lower risk of CHBV (p=0.032) and HCC (p=0.006). The gene-gene interactions were also associated with a significant increase in HAI and fibrosis score in CHBV patients. Cyp2E1, hOGG1 and XRCC1 genotypes significantly alter the risk of HBV related liver disease susceptibility and severity, independently or through gene-gene interaction.

Association of XRCC1, XRCC3, and XPD genetic polymorphism with an increased risk of hepatocellular carcinoma because of the hepatitis B and C virus

OBJECTIVE

The south-east Asian and sub-Saharan African populations are the most susceptible to hepatocellular carcinoma (HCC). We aimed to establish whether XRCC1, XRCC3, and XPD are associated with liver cancer in Pakistan and to examine the interaction of hepatitis B virus (HBV) or hepatitis C virus (HCV) with repaired genes in the occurrence of liver cancer.

MATERIALS AND METHODS

We enrolled 74 healthy individuals, 75 had either HBV or HCV, and 50 were HCC patients. The characteristic information of all the study participants were collected through a standard interviewer-administered questionnaire. The PCR-RFLP was used to identify the genotype of the patients.

RESULTS

The results of our study indicated that the patients infected with HBV or HCV had a four or three-fold greater risk of developing liver cancer. Patients older than 55 years of age had a significantly higher risk of developing cancer compared with younger patients. The homozygous wild types Arg/Arg for 280 and Thr/Thr for 241 were more frequent in the controls than in the cases. The allelic frequency of mutant 280His and 399Gln was more pronounced among HCC cases than the controls or the HBV-infected patients.

CONCLUSION

The frequency of the XPD gene in the controls was in Hardy-Weinberg equilibrium, indicating that the gene played a protective role in the Pakistani population. XRCC1 or XRCC3 was associated with liver cancer in the Pakistani population; however, the XPD gene played a vital role in the repair of DNA damage.

Impact of DNA polymorphisms in key DNA base excision repair proteins on cancer risk

Genetic variation in DNA repair genes can modulate DNA repair capacity and may be related to cancer risk. However, study findings have been inconsistent. Inheritance of variant DNA repair genes is believed to influence individual susceptibility to the development of environmental cancer. Reliable knowledge on which the base excision repair (BER) sequence variants are associated with cancer risk would help elucidate the mechanism of cancer. Given that most of the previous studies had inadequate statistical power, we have conducted a systematic review on sequence variants in three important BER proteins. Here, we review published studies on the association between polymorphism in candidate BER genes and cancer risk. We focused on three key BER genes: 8-oxoguanine DNA glycosylase (OGG1), apurinic/apyrimidinic endonuclease (APE1/APEX1) and x-ray repair cross-complementing group 1 (XRCC1). These specific DNA repair genes were selected because of their critical role in maintaining genome integrity and, based on previous studies, suggesting that single-nucleotide polymorphisms (SNPs) in these genes have protective or deleterious effects on cancer risk. A total of 136 articles in the December 13, 2010 MEDLINE database (National Center for Biotechnology Information, http://www.ncbi.nlm.nih.gov/pubmed/) reporting polymorphism in OGG1, XRCC1 or APE1 genes were analyzed. Many of the reported SNPs had diverse association with specific human cancers. For example, there was a positive association between the OGG1 Ser326Cys variant and gastric and lung cancer, while the XRCC1 Arg399Gln variant was associated with reduced cancer risk. Gene-environment interactions have been noted and may be important for colorectal and lung cancer risk and possibly other human cancers.