Association between single-nucleotide polymorphisms of selected genes involved in the response to DNA damage and risk of colon, head and neck, and breast cancers in a Polish population. J Appl Genet. 2010;51:343-352. [PMID: 20720310 DOI: 10.1007/bf03208865]

XRCC1 R194W and R399Q Polymorphisms and Colorectal Cancer Risk in a Northeastern Mexican Population

Colorectal cancer (CRC) is one of the most common cancers worldwide. Its etiopathogenesis is complex, mainly influenced by genetic instability caused by the accumulation of mutations. The XRCC1 gene, which is involved in DNA repair, has been associated with CRC through the R194W (C194T) and R399Q (G399A) polymorphisms, but the results are inconsistent. Here, we analyzed the association of these polymorphisms with sporadic CRC in a northeastern Mexican population, including 155 male CRC patients and 155 male controls. Genotyping was performed using the RFLP method. An association with CRC was found for the 399A allele (G vs A; OR = 1.48 (1.03-2.13), P=0.034) and for the 399AA genotype in a codominant model (AA vs GG; OR = 3.11 (1.06-9.10), P=0.031). In contrast, there were no significant differences between CRC patients and controls for the C194T polymorphism (C vs T; OR = 0.82 (0.52-1.31), P=0.41). These results are consistent with many similar studies, but further research is needed to verify whether the XRCC1 R194W and R399Q polymorphisms play a role in CRC etiology. The functional significance of these polymorphisms is unclear, but some studies suggest that they influence DNA repair capacity and, thus, cancer risk.

Gene polymorphisms and risk of head and neck squamous cell carcinoma: a systematic review

Background

Exposure to the same environmental factors in different people have resulted in different susceptibility to head and neck squamous cell carcinoma (HNSCC), which suggests genetic variation may be a risk factor for the development of HNSCC. So, the aim was to review literatures on the association between gene polymorphisms and risk of HNSCCs.

Materials and methods

This systematic review included all articles on the impact of gene polymorphisms on risk and susceptibility to HNSCC published till September 2021 using PubMed, Web of science, SCOPUS, Google Scholar and Cochrane library databases.

Results

Of 1163 initial searched articles, 77 articles were eligible to include in this review. Studies were categorized based on gene functions. In each category, studied gene polymorphisms related to growth control genes, cell cycle control, apoptosis, DNA repair genes, carcinogen-metabolizing enzymes, alcohol-metabolizing genes, antioxidant gene, inflammatory cytokine, transcription factor, tumor immunity, folate metabolism, and tumor suppressor gene were discussed separately. Among the polymorphisms that are often significantly associated with HNSCC risk are: GSTM1 null, GSTT1 null, CYP2D6 *4, XRCC1 Arg194Trp and Arg399Gln, ERCC1 C8092A, XPD Lys751Gln, XRCC3 Thr241Met, P53 codon 72 and MTHFR C677T polymorphisms.

Conclusion

Varied and contradictory results have been reported in different studies regarding the association of gene polymorphisms with HNSCC risk. To conclude about this association and to overcome these contradictions, it is necessary to use the results of existing meta-analyses or to perform new or updated meta-analyses.

Polymorphisms of nucleotide excision repair genes associated with colorectal cancer risk: Meta-analysis and trial sequential analysis

Background: Reduced DNA repair capacity in nucleotide excision repair (NER) pathways owing to genetic variant may influence cancer susceptibility. According to published studies, variants of NER genes associations with colorectal cancer (CRC) risk were inconclusive. Thus, this meta-analysis aimed to explore the possible association. A trial sequence analysis (TSA) analysis was performed to control the risk of false positive or false negative.

Methods: PubMed, Web of Science, Embase, Cochrane Library, China National Knowledge Network (CNKI), Wanfang Database and Scientific and Technical Journal Database (VIP) were searched to identify relative studies until April 2022. The association was assessed by odds ratio (OR) in Allele, homozygous, heterozygous, dominant, recessive, and over-dominant models. In addition, Begg’s and Egger’s tests, sensitivity analysis, subgroup analysis and TSA analysis were performed.

Results: A total of 29 studies were eventually included in the meta-analysis, including 12,153 CRC patients and 14,168 controls. It showed that excision and repair cross complementary group 1 (ERCC1) rs11615 CC genotype decreased the risk of CRC, compared with TT genotype (CC vs. TT: OR = 0.816, 95% CI = 0.673–0.990, p = 0.039). For ERCC1 rs3212986, the significant impact was detected on increased the risk of CRC in the allele (OR = 1.267, 95% CI = 1.027–1.562, p = 0.027), homozygous (OR = 1.805, 95% CI = 1.276–2.553, p = 0.001), dominant (OR = 1.214, 95% CI = 1.012–1.455, p = 0.037) and recessive (OR = 1.714, 95% CI = 1.225–2.399, p = 0.002) models, especially in the Asian population. The results revealed the association of ERCC2 rs1799793 A allele with a higher risk of CRC (A vs. G: OR = 1.163, 95% CI = 1.021–1.325, p = 0.023). It also showed that ERCC5 rs17655 increased CRC risk in the allele (OR = 1.104, 95% CI = 1.039–1.173, p = 0.001), homozygous (OR = 1.164, 95% CI = 1.018–1.329, p = 0.026), heterozygous (OR = 1.271, 95% CI = 1.018–1.329, p < 0.001), dominant (OR = 1.241, 95% CI = 1.135–1.358, p < 0.001) and over-dominant (OR = 0.828, 95% CI = 0.762–0.900, p < 0.001) models, especially among Asians.

Conclusion: This meta-analysis based on current evidence suggests that the significant association was observed between ERCC1 rs11615, ERCC1 rs3212986, ERCC2 rs1799793, and ERCC5 rs17655 and CRC susceptibility. However, given the limited sample size and the influence of genetic background, studies of a larger scale and well-designed are required to confirm the results.

Xeroderma Pigmentosum: A Genetic Condition Skin Cancer Correlated—A Systematic Review

Background. Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder of UV radiation-induced damage repair that is characterized by photosensitivity and a propensity for developing, among many others, skin cancers at an early age. This systematic review focused on the correlation between the clinical, pathological, and genetic aspects of XP and skin cancer. Methods. A systematic review was conducted through a literature search of online databases PubMed, Cochrane Library, SciELO, and Google Scholar. Search terms were “Xeroderma pigmentosum”, “XP”, “XPC”, “Nucleotide excision repair”, “NER”, “POLH”, “Dry pigmented skin”, and “UV sensitive syndrome” meshed with the terms “Skin cancer”, “Melanoma”, and “NMSC”. Results. After 504 abstracts screening, 13 full-text articles were assessed for eligibility, and 3 of them were excluded. Ten articles were selected for qualitative assessment. Conclusions. Patients with XP usually suffer shorter lives due to skin cancer and neurodegenerative disease. Deletion/alteration of a distinct gene allele can produce different types of cancer. The XPC and XP-E variants are more likely to have skin cancer than patients in other complement groups, and the most common cause of death for these patients is skin cancer (metastatic melanoma or invasive SCC). Still, aggressive preventative measures to minimize UV radiation exposure can retard the course of the disease and improve the quality of life.

Association between superoxide dismutase 2, glutathione peroxidase 1, xeroderma pigmentosum group d gene variations, and head and neck squamous cell cancer susceptibility

As oxidative stress is implicated in the pathogenesis of head and neck squamous cell cancer (HNSCC), the functions of antioxidant enzyme systems and DNA repair proteins are critical in the development of cancer. To investigate the role of genetic polymorphisms of the antioxidant superoxide dismutase 2 (SOD2) Val16Ala, glutathione peroxidase 1 (GPX1) Pro198Leu, and the DNA repair Xeroderma Pigmentosum Group D (XPD) Lys751Gln genes under exogenous risk factors, including smoking and alcohol consumption, in HNSCC carcinogenesis, we conducted a case-control study on 139 unrelated cases and 265 non-cancer controls. Polymorphisms were analyzed in additive, dominant and recessive genetic models, individually and in an interaction model. Carriers of the T allele of SOD2 were associated with an increased risk for HNSCC in the overall subgroups of males and smokers; similarly, the T allele of GPX1 was associated with elevated risk in the overall and smoker subgroup. A 12.47-fold increased risk was observed for the carriers of GPX1 TT, SOD2 CT and XPD CC genotypes for HNSCC. This is the first study presenting the potential roles of SOD2, GPX1 and XPD polymorphisms in interaction and under three genetic models in the development of HNSCC. The results suggest that these polymorphisms slightly modify the risk in HNSCC development individually but are significantly higher when they functioned and were evaluated together.

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.

Association of XPD Lys751Gln gene polymorphism with susceptibility and clinical outcome of colorectal cancer in Pakistani population: a case-control pharmacogenetic study

BACKGROUND

XPD Lys751Gln polymorphism may modulate inter-individual variation in repair capacity of DNA, which may enhance a person's susceptibility to develop colorectal cancer (CRC). The analysis of XPD Lys751Gln polymorphism may provide important information for identifying high-risk individuals and for selecting the most appropriate treatment for poor prognostic CRC patients.

OBJECTIVE

The overall objective was to find out the association of XPD Lys751Gln gene polymorphism with the risk of having a colorectal cancer and the ultimate clinical outcomes. In this study a total of 300 subjects (CRC and Controls), were genotyped for XPD Lys751Gln.

METHODS

Using PCR-RFLP methods, the association of XPD Lys751Gln gene polymorphism with the risk of having a colorectal cancer was studied. In addition to overall risk assessment, genotyping results were also investigated with respect to the lifestyle risk factors, patients treated with oxaliplatin-based chemotherapy and clinicopathological characteristics.

RESULTS

The overall correlation between the XPD Lys751Gln genetic variation and the CRC risk was observed to be significant with both the homozygous variant genotype Gln/Gln as well as heterozygous genotype Lys/Gln being associated with the increased risk of CRC. Additional stratified analyses revealed that XPD Lys751Gln variants remarkably increased risk of CRC in males and younger individuals (≤ 50 years), Naswar users (8.09-fold) and high intake of red meat.

CONCLUSIONS

Our findings suggest that the relationship between the XPD Lys751Gln variants and lifestyle factors modulates the risk for CRC in Pakistani population.

Contribution of xeroderma pigmentosum complementation group D gene polymorphisms in breast and ovarian cancer susceptibility: A protocol for systematic review and meta analysis

BACKGROUND

The role of xeroderma pigmentosum complementation group D (XPD) gene polymorphisms in breast and ovarian cancer development has long been controversial and existing data were inconsistent. Here, we conducted a comprehensive systemic review and meta-analysis to better clarify the association.

METHODS

Relevant case-control studies published in electronic data base from October 1999 to September 2019 were assessed. The statistical analyses of the pooled odds ratios (ORs) and the corresponding 95% confidence intervals (95%CIs) were calculated by using Revman 5.2 software (Cochrane Collaboration, Copenhagen).

RESULTS

31 articles including 38 case-control studies and 2 XPD polymorphisms (rs1799793 and rs238406) were analyzed. The results showed statistical significance in heterozygous mutants among Asian population for rs1799793 (GA vs GG + AA: OR = 1.38, 95%CI = 1.21-1.56), and Caucasian population for rs238406 (CA vs AA + CC: OR = 0.63, 95%CI = 0.49-0.80), while the rest comparisons including overall groups and subgroups stratified by cancer types and ethnicity failed to indicate any association with breast and ovarian cancer risk.

CONCLUSIONS

The current meta-analysis suggested no concrete correlation of XPD rs1799793(G/A) and rs238406(C/A) polymorphisms with breast cancer or ovarian cancer susceptibility. However, it indicated that heterozygous genotypes might share different pathophysiologic mechanism from not only homozygous wildtypes but also homozygous mutants. More case-control studies with well-adjusted data and diverse populations are essential for validation of our conclusion.

Association of human XPA rs1800975 polymorphism and cancer susceptibility: an integrative analysis of 71 case-control studies

BACKGROUND

The objective of the present study is to comprehensively evaluate the impact of the rs1800975 A/G polymorphism within the human xeroderma pigmentosum group A (XPA) gene on susceptibility to overall cancer by performing an integrative analysis of the current evidence.

METHODS

We retrieved possible relevant publications from a total of six electronic databases (updated to April 2020) and selected eligible case-control studies for pooled assessment. P-values of association and odds ratio (OR) were calculated for the assessment of association effect. We also performed Begg's test and Egger's test, sensitivity analysis, false-positive report probability (FPRP) analysis, trial sequential analysis (TSA), and expression/splicing quantitative trait loci (eQTL/sQTL) analyses.

RESULTS

In total, 71 case-control studies with 19,257 cases and 30,208 controls from 52 publications were included for pooling analysis. We observed an enhanced overall cancer susceptibility in cancer cases compared with negative controls in the Caucasian subgroup analysis for the genetic models of allelic G vs. A, carrier G vs. A, homozygotic GG vs AA, heterozygotic AG vs. AA, dominant AG + GG vs. AA and recessive GG vs. AA + AG (P < 0.05, OR > 1). A similar positive conclusion was also detected in the "skin cancer" or "skin basal cell carcinoma (BCC)" subgroup analysis of the Caucasian population. Our FPRP analysis and TSA results further confirmed the robustness of the conclusion. However, our eQTL/sQTL data did not support the strong links of rs1800975 with the gene expression or splicing changes of XPA in the skin tissue. In addition, even though we observed a decreased risk of lung cancer under the homozygotic, heterozygotic and dominant models (P < 0.05, OR < 1) and an enhanced risk of colorectal cancer under the allelic, homozygotic, heterozygotic, dominant (P < 0.05, OR > 1), our data from FPRP analysis and another pooling analysis with only the population-based controls in the Caucasian population did not support the strong links between the XPA rs1800975 A/G polymorphism and the risk of lung or colorectal cancer.

CONCLUSIONS

Our findings provide evidence of the close relationship between the XPA rs1800975 A/G polymorphism and susceptibility to skin cancer in the Caucasian population. The potential effect of XPA rs1800975 on the risk of developing lung or colorectal cancer still merits the enrollment of larger well-scaled studies.

Association of DNA repair gene polymorphisms with colorectal cancer risk and treatment outcomes

Colorectal cancer (CRC) is the third most common carcinoma worldwide. Despite the progress in screening and treatment, CRC remains a leading cause of cancer-related mortality. Alterations to normal nucleic acid processing may drive neoplastic transformation of colorectal epithelium. DNA repair machinery performs an essential function in the protection of genome by reducing the number of genetic polymorphisms/variations that may drive carcinogenicity. Four essential DNA repair systems are known which include nucleotide excision repair (NER), base excision repair (BER), mismatch repair (MMR), and double-strand break repair (DSBR). Polymorphisms of DNA repair genes have been shown to influence the risk of cancer development as well as outcomes of treatment. Several studies demonstrated the association between genetic polymorphism of DNA repair genes and increased risk of CRC in different populations. In this review, we have summarized the impact of DNA repair gene polymorphisms on risk of CRC development and treatment outcomes. Advancements of the current understanding for the impact of DNA repair gene polymorphisms on the risk and treatment of CRC may support diagnostic and predictive roles in patients with CRC.

Genetic Polymorphisms of DNA Repair Pathways in Sporadic Colorectal Carcinogenesis

DNA repair systems play a critical role in maintaining the integrity and stability of the genome, which mainly include base excision repair (BER), nucleotide excision repair (NER), mismatch repair (MMR) and double-strand break repair (DSBR). The polymorphisms in different DNA repair genes that are mainly represented by single-nucleotide polymorphisms (SNPs) can potentially modulate the individual DNA repair capacity and therefore exert an impact on individual genetic susceptibility to cancer. Sporadic colorectal cancer arises from the colorectum without known contribution from germline causes or significant family history of cancer or inflammatory bowel disease. In recent years, emerging studies have investigated the association between polymorphisms of DNA repair system genes and sporadic CRC. Here, we review recent insights into the polymorphisms of DNA repair pathway genes, not only individual gene polymorphism but also gene-gene and gene-environment interactions, in sporadic colorectal carcinogenesis.

DNA Repair Gene (XPD, XRCC4, and XRCC1) Polymorphisms in Patients with Endometrial Hyperplasia: A Pilot Study

Background

In this study, we aimed to evaluate the association between endometrial hyperplasia and DNA repair gene (XPD, XRCC4, and XRCC1) polymorphisms.

Material/Methods

There were 114 cases enrolled in the study in 4 groups: simple endometrial hyperplasia (SH) (Group 1), complex endometrial hyperplasia without atypia (CH) (Group 2), complex atypical endometrial hyperplasia (CAH) (Group 3), and normal endometrium (NE) (Group 4). Of these cases, 37 cases had SH, 36 cases had CH, 16 cases had CAH, and 25 cases had NE. To evaluate an association between atypia and DNA repair genes, we consider a group that included both SH and CH, the endometrial hyperplasia without atypia cases (Group 5). Genomic DNA was isolated from paraffin-embedded endometrial tissue collected from the Pathology Department of Gaziantep University Medical School. Polymerase chain reaction (PCR) and/or restriction fragment length polymorphism (RFLP) method was used for evaluating of XPD (−751), XRCC4 (−1394 and a variable number of tandem repeats in intron 3), and XRCC1 (−399) genes.

Results

We observed a notable distinction in patients having endometrial hyperplasia without atypia (the SH+CH group) and the CAH group in terms of XPD (−751) gene polymorphisms. A notable contrast was observed in patients with endometrial hyperplasia without atypia (the SH+CH group) and the NE group in terms of XRCC4 (VNTR intron 3) polymorphisms (P=0.026, P=0.018, respectively).

Conclusions

It was evident the DNA repair gene XPD and XRCC4 polymorphisms had a role in the pathophysiology of endometrial hyperplasia.

DNA damage response and repair in colorectal cancer: Defects, regulation and therapeutic implications

DNA damage response, a key factor involved in maintaining genome integrity and stability, consists of several kinase-dependent signaling pathways, which sense and transduce DNA damage signal. The severity of damage appears to determine DNA damage responses, which can include cell cycle arrest, damage repair and apoptosis. A number of recent studies have demonstrated that defection in signaling through this network is thought to be an underlying mechanism behind the development and progression of various types of human malignancies, including colorectal cancer. In this review, colorectal cancer and its molecular pathology as well as DNA damage response is briefly introduced. Finally, the involvement of key components of this network in the initiation/progression, prognosis, response to treatment and development of drug resistance is comprehensively discussed.

Lack of correlation between X-ray repair cross-complementing group 1 gene polymorphisms and the susceptibility to colorectal cancer in a Malaysian cohort

X-ray repair cross-complementing group 1 (XRCC1) is one of the key components in the base excision repair pathway that repairs erroneous DNA lesions and removes nonbulky base adducts for the maintenance of genome integrity. Studies have revealed that differences in individual DNA repair capacity can impact the interindividual variation in cancer susceptibility, tumour aggressiveness and treatment response. The relationship between XRCC1 and sporadic colorectal cancer (CRC) susceptibility, which is hitherto inconclusive, has been explored in many association studies of different populations. In view of the conflicting findings generated, we aimed to investigate the association between XRCC1 and genetic predisposition to CRC among Malaysians. The present case-control association study was conducted on 130 CRC patients and 212 age-matched healthy controls. The genotyping of XRCC1 Arg194Trp, Arg280His and Arg399Gln single nucleotide polymorphisms was performed with allele-specific real-time PCR approach. This was followed by basic statistical analysis on the single nucleotide polymorphisms and haplotype data obtained. No significant difference in the allele and genotype frequencies was observed between CRC patients and healthy controls (P>0.05). There was also no association observed between XRCC1 haplotypes and CRC (P>0.05). In conclusion, a positive association between XRCC1 gene polymorphisms and CRC risk was not established in our Malaysian population.

Association of XPA polymorphism with breast cancer risk: A meta-analysis

BACKGROUND

The association of XPA rs1800975 polymorphism with breast cancers has been reported in several studies, but the results were conflicting. In order to analyze the association between XPA rs1800975 polymorphism and the risk of breast cancer, a meta-analysis was performed in the present study.

METHODS

The literature search for relevant studies was conducted in PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure (CNKI), and Wanfang Med Online databases. The odds ratios (ORs) and their corresponding 95% confidence intervals (95% CIs) were calculated using fixed-effect/random-effects models by the STATA 12.0 software. The sources of heterogeneity were analyzed by subgroup analysis.

RESULTS

Six case-control studies involving 5069 subjects (2338 patients and 2731 healthy controls) were included in the present meta-analysis. In the pooled analysis, no obvious association was found between XPA rs1800975 polymorphism and the risk of breast cancer in all genetic models. However, in subgroup analysis based on ethnicity, XPA rs1800975 polymorphism was found to be related to decreased breast cancer risk in non-Asians in the recessive model (OR = 0.80, 95% CI = 0.64-1.00, P = .045). Moreover, source of control subgroup analysis demonstrated that XPA rs1800975 polymorphism might decrease the risk of breast cancer in population-based group in the recessive model (OR = 0.80, 95% CI = 0.64-1.00, P = .045).

CONCLUSION

XPA rs1800975 polymorphism may decrease the risk of breast cancer in both non-Asians and population-based patients. Large sample size and well-designed study is needed for further assessing the role of XPA polymorphism in breast cancer risk.

Association between the ERCC2 Asp312Asn polymorphism and risk of cancer

Cancer is the leading cause of death in economically developed countries and the second leading cause of death in developing countries. The relationship between genetic polymorphisms and the risk of cancers has been widely researched. Excision repair cross-complementing group 2 (ERCC2) gene plays important roles in the nucleotide excision repair pathway. There is contrasting evidence on the association between the ERCC2 Asp312Asn polymorphism and the risk of cancer. We conducted a comprehensive meta-analysis in order to assess the correlation between these factors. We searched the PubMed, EMBASE, Science Direct, Web of Science, and CNKI databases for studies published from January 1, 2005 to January 1, 2016. Finally, 86 articles with 38,848 cases and 48,928 controls were included in the analysis. The overall analysis suggested a significant association between the ERCC2 Asp312Asn polymorphism and cancer risk. Furthermore, control source, ethnicity, genotyping method, and cancer type were used for subgroup analysis. The result of a trial sequential analysis indicated that the cumulative evidence is adequate; hence, further trials were unnecessary in the overall analysis for homozygote comparison. In summary, our results suggested that ERCC2 Asp312Asn polymorphism is associated with increased cancer risk. A significantly increased cancer risk was observed in Asian populations, but not in Caucasian populations. Furthermore, the ERCC2 Asp312Asn polymorphism is associated with bladder, esophageal, and gastric cancers, but not with breast, head and neck, lung, prostate, and skin cancers, and non-Hodgkin lymphoma. Further multi-center, well-designed studies are required to validate our results.

Associations between expression levels of nucleotide excision repair proteins in lymphoblastoid cells and risk of squamous cell carcinoma of the head and neck

Squamous cell carcinoma of head and neck (SCCHN) is one of the most common malignancies worldwide, and nucleotide excision repair (NER) is involved in SCCHN susceptibility. In this analysis of 349 newly diagnosed SCCHN patients and 295 cancer-free controls, we investigated whether expression levels of eight core NER proteins were associated with risk of SCCHN. We quantified NER protein expression levels in cultured peripheral lymphocytes using a reverse-phase protein microarray. Compared with the controls, SCCHN patients had statistically significantly lower expression levels of ERCC3 and XPA (P = 0.001 and 0.001, respectively). After dividing the subjects by controls' median values of expression levels, we found a dose-dependent association between an increased risk of SCCHN and low expression levels of ERCC3 (adjusted OR, 1.75, and 95% CI: 1.26-2.42; P_trend = 0.008) and XPA (adjusted OR, 1.88; 95% CI, 1.35-2.60; P_trend = 0.001). We also identified a significant multiplicative interaction between smoking status and ERCC3 expression levels (P = 0.014). Finally, after integrating demographic and clinical variables, we found that the addition of ERCC3 and XPA expression levels to the model significantly improved the sensitivity of the expanded model on SCCHN risk. In conclusion, reduced protein expression levels of ERCC3 and XPA were associated with an increased risk of SCCHN. However, these results need to be confirmed in additional large studies.

NBS1 rs2735383 polymorphism is associated with an increased risk of laryngeal carcinoma

BACKGROUND

Nijmegen breakage syndrome 1 (NBS1), as a key protein in the DNA double-strand breaks (DSBs) repair pathway, plays an important role in maintaining genomic stability. Although single nucleotide polymorphisms (SNPs) in NBS1 have frequently been studied in multiple cancers, the relationships of two functional NBS1 polymorphisms (rs2735383 and rs1805794) with laryngeal carcinoma are yet unclear. Therefore, in the present study, we performed a case-control study including 342 cases and 345 controls to analyze the associations between two polymorphisms of NBS1 and the risk of laryngeal carcinoma.

METHODS

We used the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method to determine the genotypes of the functional SNPs in NBS1 gene.

RESULTS

In comparison with the homozygous rs2735383GG genotype, the CC genotype was significantly associated with an increased risk of laryngeal carcinoma (adjusted OR = 1.884, 95%CI = 1.215-2.921). The rs2735383C variant genotypes (GC + CC) conferred a 1.410-fold increased risk of laryngeal carcinoma (adjusted OR = 1.410, 95%CI = 1.004-1.980). Furthermore, when compared to rs2735383GG genotype in laryngeal carcinoma tissues, the combined GC and CC genotypes exerted a significantly lower mRNA level of NBS1 (P = 0.003). In contrast, no significant association was found between rs1805794G > C polymorphism and cancer risk (adjusted OR = 1.074, 95%CI = 0.759-1.518 for GC; adjusted OR = 1.100, 95%CI = 0.678-1.787 for CC; adjusted OR = 1.079, 95%CI = 0.774-1.505 for GC + CC).

CONCLUSIONS

These findings indicate that rs2735383G > C polymorphism in NBS1 may play a crucial role in the development of laryngeal carcinoma.

Polymorphisms in BER genes and risk of breast cancer: evidences from 69 studies with 33760 cases and 33252 controls

Recently, numerous studies have reported an association between single nucleotide polymorphisms in base-excision repair genes and the risk of developing breast cancer, however there is no consensus. The aim of this meta-analysis was to review and quantitatively assess the relationship between single nucleotide polymorphisms in base-excision repair genes and breast cancer risk. The results suggested that a mutation of T to G in rs1760944 may lead to a higher risk of developing breast cancer in the Mongoloid population, and G to A of rs25487 significantly reduced the risk of breast cancer in Mongoloid and Caucasoid populations. In contrast to the CC and CG genotypes, the GG genotype of rs1052133 located on theOGG1 gene appeared to be a protective factor against developing breast cancer in both Mongoloid and Caucasoid populations. There was no evidence to suggest that rs25489, rs1799782, rs1130409, rs1805414 and rs1136410 were associated with breast cancer risk. In conclusion, this study provides evidence to support the theory that DNA repair genes are associated with breast cancer risk, providing information to further understand breast cancer etiology. and The potential biological pathways linking DNA repair, ethnic background, environment and breast cancer require further investigation.

Investigation of cyclin D1 rs9344 G>A polymorphism in colorectal cancer: a meta-analysis involving 13,642 subjects

The relationship between cyclin D1 (CCND1) rs9344 G>A polymorphism and colorectal cancer (CRC) risk is still ambiguous. To obtain a precise estimation of the relationship, we performed an extensive meta-analysis based on the eligible studies. Crude odds ratios with their 95% confidence intervals were harnessed to determine the strength of correlation between CCND1 rs9344 G>A polymorphism and CRC risk under the allele, the homozygote, the dominant, and the recessive genetic models, respectively (28 studies with 5,784 CRC cases and 7,858 controls). Our results indicated evidence of the association between CCND1 rs9344 G>A polymorphism and the increased risk of CRC in four genetic models: A vs G, AA vs GG, AA+GA vs GG, and AA vs GA+GG. In a stratified analysis by cancer type of CRC, there was an increased risk of sporadic CRC found in three genetic models: A vs G, AA vs GG, and AA+GA vs GG. In a stratified analysis by ethnicity, there was an increased CRC risk found among Asians in allele comparison genetic models, as well as Caucasians in two genetic models: AA+GA vs GG and A vs T. In summary, this meta-analysis demonstrates that CCND1 rs9344 G>A polymorphism may be a risk factor for CRC.

Gut Microbiota Imbalance and Base Excision Repair Dynamics in Colon Cancer

Gut microbiota are required for host nutrition, energy balance, and regulating immune homeostasis, however, in some cases, this mutually beneficial relationship becomes twisted (dysbiosis), and the gut flora can incite pathological disorders including colon cancer. Microbial dysbiosis promotes the release of bacterial genotoxins, metabolites, and causes chronic inflammation, which promote oxidative DNA damage. Oxidized DNA base lesions are removed by base excision repair (BER), however, the role of this altered function of BER, as well as microbiota-mediated genomic instability and colon cancer development, is still poorly understood. In this review article, we will discuss how dysbiotic microbiota induce DNA damage, its impact on base excision repair capacity, the potential link of host BER gene polymorphism, and the risk of dysbiotic microbiota mediated genomic instability and colon cancer.

CCND1 G870A polymorphism and colorectal cancer risk: An updated meta-analysis

Molecular epidemiological studies have revealed a closer association between cyclin D1 (CCND1) polymorphism and the risk of colorectal cancer; however, the results were inconsistent. The aim of the present meta-analysis was to investigate the association between CCND1 G870A polymorphism and colorectal cancer risk. Online electronic databases (PubMed and Embase) were searched. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to assess the association between CCND1 G870A polymorphism and the risk of colorectal cancer. In addition, heterogeneity, publication bias and sensitivity analysis were performed to guarantee the statistical power. In total, 23 published case-control studies with 6,320 patients and 8,252 controls were selected. Significantly increased risks were observed in four genetic models (A vs. G: OR=1.09, 95% CI=1.00-1.18, I²=54.3%; GA vs. GG: OR=1.13, 95% CI=1.04-1.24, I²=18.2%; AA vs. GG, OR=1.17: 95% CI=1.00-1.38, I²=52.5%; GA+AA vs. GG: OR=1.14, 95% CI=1.05-1.24, I²=33.8%). Similarly, significant associations were also identified in the stratified analysis in the cancer subtype of sporadic colorectal cancer (GA vs. GG: OR=1.21, 95% CI=1.04-1.42, I²=24.1%; GA+AA vs. GG: OR=1.18, 95% CI=1.02-1.37, I²=35.0%), Caucasian population (GA vs. GG, OR=1.14, 95% CI=1.02-1.28, I²=19.8%; GA+AA vs. GG, OR=1.14, 95% CI=1.02-1.27, I²=37.5%) and other subgroups of control design and genotyping type. The present updated meta-analysis suggested that CCND1 G870A may present an increased risk for developing colorectal cancer, particularly in sporadic colorectal cancer and a Caucasian population.

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.

XRCC1 and OGG1 Gene Polymorphisms and Breast Cancer: A Systematic Review of Literature

Context:

Known polymorphisms of DNA repair genes can be associated with the risk of many types of cancer. There is no consensus regarding association between XRCC1 and OGG1 with breast cancer (BC).

Objectives:

The aim of this study is to collect relevant published studies systematically.

Data Sources:

Sixty-two publications were identified through searching PubMed, PubMed Central, ISI web of knowledge, and reference list of related articles.

Study Selection:

We performed a systematic review according MOOSE guideline criteria. All longitudinal cohort and case-control studies investigating association of any type and grade of breast cancer with XRCC1 and OGG1 gene and their polymorphisms were eligible for initial inclusion.

Data Extraction:

Two authors screened titles and abstracts and extracted all needed information from eligible studies. Four research methodological components causing bias for the association between gene polymorphisms and breast cancer risk, including source of controls sampling, population ethnicity, sample size of studies and menopausal status of cases and controls was used for assessment of quality of studies

Results:

A total of 14,793 breast cancer cases and 15,409 controls were included in assessment of XRCC1 Arg194Trp. Four studies showed significant association and one study showed protective effect of XRCC1 Arg194Trp and BC. A total of 7,716 cases and 7,370 controls were included for XRCC1 Arg280His. Only one study showed significant association of XRCC1 Arg280His and breast cancer (OR = 1.82 (1.06 - 3.15). A total of 27,167 cases and 31,998 controls were included to estimate association between XRCC1 Arg399Gln polymorphism and breast cancer. Seven studies showed significant association and one showed protective effect of XRCC1 Arg399Gln and BC. A total of 9,417 cases and 11,087 controls were included for OGG1 Ser326Cys. Among studies focused on OGG1 Ser326Cys, none showed significant association with breast cancer.

Conclusions:

Systematic search of major databases identify many studies addressing the relationship between BC and susceptible alleles in the base excision repair genes and the fact that there are many variations in the magnitude of association depending on inheritance model and the population of the study.

Association of XRCC1 Arg399Gln Polymorphism with Colorectal Cancer Risk: A HuGE Meta Analysis of 35 Studies

BACKGROUND

Non-synonymous polymorphisms in XRCC1 hase been shown to reduce effectiveness of DNA repair and be associated with risk of certain cancers. In this study we aimed to clarify any association between XRCC1 Arg399Gln and colorectal cancer (CRC) risk by performing a meta-analysis of published case-control studies.

MATERIALS AND METHODS

PubMed and Google Scholar were searched to explore the association between XRCC1 and CRC. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to estimate the association strength. Publication bias was assessed by Egger's and Begg's tests.

RESULTS

Up to January 2015, 35 case control studies involving 9,114 CRC cases and 13,948 controls were included in the present meta-analysis. The results showed that the Arg399Gln polymorphism only under an allele genetic model was associated with CRC risk (A vs. G: OR 0.128, 95% CI 0.119-0.138, p<0.001). Also, this meta-analysis suggested that the XRCC1 Arg399Gln polymorphism might associated with susceptibility to CRC in Asians (A vs G: OR 0.124, 95% CI 0.112-0.138, p<0.001) and Caucasian (A vs G: OR 0.132, 95% CI 0.119-0.146, p<0.001) only under an allele genetic model.

CONCLUSIONS

This meta-analysis confirms the association between XRCC1 Arg399Gln polymorphism and CRC risk and suggests that the heterogeneity is not strongly modified by ethnicity and deviation from the Hardy-Weinberg equilibrium.

Potential risk of esophageal squamous cell carcinoma due to nucleotide excision repair XPA and XPC gene variants and their interaction among themselves and with environmental factors

The association of nucleotide excision repair (NER) gene polymorphisms with esophageal squamous cell carcinoma (ESCC) is inconclusive. The aim of the current study was to assess the association of repair gene xeroderma pigmentosum A (XPA) (rs-1800975) and xeroderma pigmentosum C (XPC) (rs-2228000) polymorphisms with ESCC risk as well as modifying effects of environmental factors. The genotyping was done in 450 confirmed ESCC cases and equal number of individually matched controls by the polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) and direct sequencing methods. Conditional logistic regression models were used to assess the genotypic associations and interactions. A high ESCC risk was found in subjects who carried the homozygous minor allele of XPA (odds ratio (OR) = 3.57; 95 % confidence interval (CI) = 1.76-7.23), and the risk was higher when analysis was limited to participants who were ever smokers (OR = 4.22; 95 % CI = 2.01-8.88), lived in adobe houses (OR = 8.42; 95 % CI = 3.74-18.95), consumed large volumes of salt tea (OR = 7.42; 95 % CI = 3.30-16.69), or had a positive family history of cancer (FHC) (OR = 9.47; 95 % CI = 4.67-19.20). In case of XPC, a homozygous minor allele also showed strong association with ESCC risk (OR = 4.43; 95 % CI = 2.41-8.16). We again observed a very strong effect of the above environmental factors in elevating the risk of ESCC. Further, the variant genotypes of both genes in combination showed an increased risk towards ESCC (OR = 7.01; 95 % CI = 3.14-15.64) and such association was synergistically significant. Salt tea consumption showed an interaction with genotypes of XPA and XPC. However, an interaction with FHC was significant in the case of XPA genotype only. XPA and XPC genotypes are associated with an increased risk of ESCC, and such association was reasonably modulated by different exposures.

The role of base excision repair in pathogenesis of breast cancer in the Polish population

Breast cancer (BC) is leading type of cancer among group of women, which determines almost 23% of invasive cancers. It has been reported repeatedly that the level of oxidative stress is higher for BC in comparison to cancer-free woman. The goal of the present study was to evaluate the role of base excision repair (BER) pathway in the development of BC. One-hundred seventy-one women with confirmed BC and 222 healthy controls were enrolled in presented study. The level of oxidative DNA damage and the kinetic of their repair were analyzed by the modified alkaline comet assay. The efficiency of BER pathway was evaluated by BER assay. The presence of the 326Cys/Cys genotype and 326Cys allele of OGG1 gene and the 324His/His of MUTYH gene are associated with increased risk of BC development. Moreover, correlation between clinical parameter with selected genes has shown increased risk of BC progression. The survival analysis has shown a significant lower DFS for individuals with the 762Ala/Ala genotype compared to 762Val/Vla carriers and the 762Val/Ala genotype in relation to concomitant chemotherapy and radiotherapy. In subgroup of patients with alone chemotherapy and alone radiotherapy, the 762Val/Val genotype was significantly associated with lower overall survival. Furthermore, we also elevated the level of basal and oxidative DNA damage in a group of patients with BC in relation to healthy controls. We also observed the difference in effectiveness of DNA damage repair. The results of present studies suggested the important role of BER pathway in BC development. © 2015 Wiley Periodicals, Inc.

Susceptibility and REF1 gene polymorphism towards colorectal cancer

Published data on the relation between REF1 polymorphism and colorectal cancer risk showed inconclusive results. The aim of this study was to derive a comprehensive estimation of the association. Data on association between REF1 polymorphism and colorectal cancer risk were summarized. The association was estimated by calculating an odds ratio (OR) with corresponding 95 % confidence interval (95 % CI) with the fixed effects model when P > 0.1 (from heterogeneity test) or with the random effects model when P < 0.1. No significant association was revealed in any genetic model assumed for the overall analysis (OR = 1.03, 95 % CI = 0.81-1.32 for Glu/Glu vs. Asp/Asp; OR = 1.05, 95 % CI = 0.96-1.15 for Glu/Glu + Asp/Glu vs. Asp/Asp; OR = 0.97, 95 % CI = 0.76-1.23 for Glu/Glu vs. Asp/Glu + Asp/Asp; OR = 1.03, 95 % CI = 0.92-1.16 for Glu vs. Asp; OR = 1.09, 95 % CI = 0.93-1.27 for Asp/Glu vs. Asp/Asp). In Caucasian population, nor did we find a significant association. This research indicates that REF1 polymorphism is unlikely to be associated with colorectal cancer risk.

Association of APE1 Gene Asp148Glu Variant with Digestive Cancer: A Meta-Analysis

Background

Apurinic/apyrimidinic endonuclease-1 (APE1) is a rate-limiting enzyme in DNA base excision repair and has been implicated in carcinogenesis. In this study, we summarize available data to examine the susceptibility of APE1 gene Asp148Glu variant to digestive cancer via a meta-analysis.

Material/Methods

Study selection and data abstraction were conducted independently by 2 authors. Random-effects model was utilized to pool effect estimates. Heterogeneity and publication bias were addressed.

Results

Sixteen articles involving 4916 digestive cancer patients and 7748 controls were qualified for this meta-analysis. Overall association showed an indicative association between Asp148Glu variant and digestive cancer under allelic (odds ratio or OR=1.11; 95% confidence interval or CI: 0.99–1.25; P=0.074) and dominant (OR=1.18; 95% CI: 1.00–1.40; P=0.056) models, with strong evidence of heterogeneity. Deviation from Hardy-Weinberg equilibrium was an obvious source of heterogeneity. In subgroup analyses by cancer sites, this variant was significantly associated with the increased risk for hepatocellular cancer under allelic (OR=1.50; 95% CI: 1.25–1.80; P<0.001) and homozygous genotypic (OR=1.55; 95% CI: 1.02–2.29; P=0.028) models. There were low probabilities of publication bias for the above comparisons.

Conclusions

The results of this meta-analysis collectively suggest that APE1 gene Asp148Glu variant is not a risk-conferring factor for digestive cancer. Further large and well-designed studies are required.

Associations between NBS1 Polymorphisms and Colorectal Cancer in Chinese Population

As the central protein of the double strand breaks (DSB)-induced DNA repair pathway, NBS1 participates in detecting the DSBs and plays an essential role in maintaining genomic stability. Single nucleotide polymorphisms (SNPs) in NBS1 gene were commonly tested that associated with the susceptibility to multiple cancers, but the results remained controversial. Thus, we conducted two independent hospital-based case-control studies comprising 1,072 colorectal cancer patients and 1,263 controls to evaluate the association between four NBS1 SNPs and colorectal cancer risk. The result showed that rs2735383C/G polymorphism in the 3'-untranslated region (UTR) of NBS1 was significantly associated with risk of colorectal cancer using logistic regression (P<10(-4)). Furthermore, we observed that rs2735383CC genotype was associated with substantially increased risk of colorectal cancer (odds ratio=1.55, 95% confidence interval=1.27-1.94), compared with the rs2735383GC+GG genotypes. Further functional experiments demonstrated that the rs2735383C allele in the NBS1 disrupted the binding affinity of has-miR-509-5p to the NBS1 3'-UTR in colorectal cancer cells, affecting the NBS1 transcriptional activity and expression level. In conclusion, current evidence suggests that the rs2735383C/G polymorphism might contribute to the risk for colorectal cancer.

Association of cyclin D1 variants with head and neck cancer susceptibility: evidence from a meta-analysis

Whether cyclin D1 (CCND1) gene variants increase susceptibility to head and neck cancer (HNC) is undetermined. Therefore, we performed the present meta-analysis to systematically assess any possible association between CCND1 variants (G870A and G1722C) and HNC risk. Seventeen studies for CCND1 G870A and three studies for CCND1 G1722C were included. Overall, CCND1 polymorphisms (G870A and G1722C) had no association with increased HNC risk (p>0.05). In the subgroup analysis by smoking status, significantly increased HNC risk was found among smokers under allele contrast, homozygous comparison and recessive models (p<0.05), smoking carriers of A allele and AA genotype appearing at elevated risk. In conclusion, while there was overall a lack of any association between CCND1 polymorphisms (G870A and G1722C) and HNC risk, smokers carrying the A allele and AA genotype of the CCND1 G870A polymorphism may be susceptible to HNC development.

Relationship between apurinic endonuclease 1 Asp148Glu polymorphism and gastrointestinal cancer risk: An updated meta-analysis

AIM: To evaluate the relationship between apurinic endonuclease 1 (APE1) Asp148Glu polymorphism and the susceptibility to gastrointestinal (GI) cancers.

METHODS: We searched PubMed, ISI Web of Knowledge, and Chinese National Knowledge Infrastructure (CNKI) databases updated on July 15, 2014 for relevant studies. Only case-control studies comparing APE1 Asp148Glu polymorphism and GI cancer risk were included. We excluded studies reporting only standardized incidence ratios without control groups and those without detailed genotyping data. Meta-analysis was performed on 17 studies involving 4856 cancer patients and 6136 cancer-free controls. Review Manager version 5.1 was used to perform the meta-analysis. The pooled odds ratios (ORs) and 95% confidence intervals (CIs) were estimated under the allele contrast, homozygous, heterozygous, dominant and recessive genetic models. We also conducted subgroup analyses stratified by ethnicity and cancer type. Publication bias was evaluated using Begg’s test.

RESULTS: The meta-analysis showed a significant association between APE1 Asp148Glu polymorphism and GI cancer risk in three genetic models in the overall population (G vs T: OR = 1.18; 95%CI: 1.05-1.32; TG vs TT: OR = 1.28; 95%CI: 1.08-1.52; TG + GG vs TT: OR = 1.32; 95%CI: 1.10-1.57). Stratified analysis by ethnicity revealed a statistically increased GI cancer risk in Asians (G vs T: OR = 1.27; 95%CI: 1.07-1.51; GG vs TT: OR = 1.58; 95%CI: 1.05-2.38; TG vs TT: OR = 1.30; 95%CI, 1.01- 1.67; and TG + GG vs TT: OR = 1.38; 95%CI: 1.07-1.78), but not in Caucasians. Further subgroup analysis by cancer type indicated that APE1 Asp148Glu polymorphism may contribute to gastric cancer risk. However, Asp148Glu has no significant association with colorectal or esophageal cancer risk in any genetic model.

CONCLUSION: This meta-analysis suggests that the APE1 Asp148Glu polymorphism G allele is associated with an increased GI cancer risk, especially in gastric cancer.

DNA repair gene XRCC3 Thr241Met polymorphisms and lung cancer risk: a meta-analysis

BACKGROUND

The X-ray repair cross-complementing group 3 (XRCC3) is a highly suspected candidate gene for cancer susceptibility, and a large amount studies have examined the association of the rs861539 in XRCC3 (Thr241Met) with lung cancer risk in various populations. However, the results remain inconclusive.

METHODS

The electronic database of PubMed, Medline, Embase and CNKI (China National Knowledge Infrastructure) were searched for case-control studies published up to December 05, 2013. A systematic review and meta-analysis was performed to evaluate the relationship between XRCC3 Thr241Met polymorphism and lung cancer risk. Data were extracted and pooled odds ratio (OR) with its 95% confidence intervals (CI) were calculated.

RESULTS

Total 21 studies, including 6880 lung cancer cases and 8329 controls, were available for meta-analysis. Overall, our results showed that the XRCC3 Thr241Met polymorphism was not associated with risk of lung cancer in all genetic contrast models (P>0.05). Stratified analyses by ethnicity (Asians, Caucasians and mixed population) showed similar results. Additionally, no evidence of publication bias was observed by using the funnel plot.

CONCLUSIONS

There is no clear evidence showing a significant correlation between XRCC3 Thr241Met polymorphism and lung cancer risk in total population and stratified analysis by ethnicity. However, studies assessing the gene-gene interactions should be considered to further estimate this gene variant in lung cancer risk.

Association of the XPA A23G polymorphism with the risk of head and neck carcinomas: Evidence from 5,491 subjects

The XPA gene participates in modulating DNA damage recognition during the DNA nucleotide excision repair process. Current data regarding the association of the XPA A23G polymorphism with the risk of head and neck squamous cell carcinoma (HNSCC) remain controversial, and meta-analyses focusing on the HNSCC risk and this polymorphism are limited. Therefore, the aim of the present study was to derive a more precise estimation of this association by a meta-analysis of all the eligible studies. Odds ratios (ORs) with 95% confidence intervals (CI) were assessed for the strength of the associations in eight studies, including 5,491 subjects (2,409 HNSCC cases and 3,082 controls). The overall analysis revealed that the XPA A23G polymorphism was not significantly associated with the overall HNSCC risk. Consistently, there was no evidence for the association between the XPA A23G polymorphism and HNSCC risk in subgroup analyses based on ethnicity and the source of controls. However, the significant associations in oral carcinoma with the increased risk among the XPA heterozygote (AG vs. AA: OR, 1.58; 95% CI, 1.06-2.37; P_{heterogeneity}=0.23, I²=30%) and dominant (AG +GG vs. AA: OR, 1.53; 95% CI, 1.04-2.23; P_{heterogeneity}=0.21, I²=36%) models were observed in the subgroup analysis by tumor site. In conclusion, the meta-analysis suggested that the XPA A23G polymorphism was not associated with overall HNSCC susceptibility, but it was associated with oral carcinoma susceptibility and it may be a risk factor for oral carcinoma. Further well-designed and large studies are required to confirm these associations.

XPA A23G polymorphism and risk of digestive system cancers: a meta-analysis

Background

Several studies have reported an association between the A23G polymorphism (rs 1800975) in the xeroderma pigmentosum group A (XPA) gene and risk of digestive system cancers. However, the results are inconsistent. In this study, we performed a meta-analysis to assess the association between XPA A23G polymorphism and the risk of digestive system cancers.

Methods

Relevant studies were identified using the PubMed, Web of Science, China National Knowledge Infrastructure, WanFang, and VIP databases up to August 30, 2014. The pooled odds ratio (OR) with a 95% confidence interval (CI) was calculated using the fixed or random effects model.

Results

A total of 18 case-control studies from 16 publications with 4,170 patients and 6,929 controls were included. Overall, no significant association was found between XPA A23G polymorphism and the risk of digestive system cancers (dominant model: GA + AA versus GG, OR 0.89, 95% CI 0.74–1.08; recessive model: AA versus GA + GG, OR 0.94, 95% CI 0.74–1.20; GA versus GG, OR 0.89, 95% CI 0.77–1.03; and AA versus GG, OR 0.87, 95% CI 0.64–1.19). When the analysis was stratified by ethnicity, similar results were observed among Asians and Caucasians in all genetic models. In stratified analysis based on tumor type, we also failed to detect any association between XPA A23G polymorphism and the risk of esophageal, gastric, or colorectal cancers.

Conclusion

This meta-analysis indicates that the XPA A23G polymorphism is not associated with a risk of digestive system cancers.

Genes and SNPs associated with non-hereditary and hereditary colorectal cancer

BACKGROUND

Colorectal cancer is the third most common cancer in both men and women in the world and the second leading cause of cancer-related deaths. The incidence of colorectal cancer has increased in Iran in the past three decades and is now considered as a serious problem for our society. This cancer has two types hereditary and non-hereditary, 80% of cases being the latter. Considering that the relationship between SNPs with diseases is a concern, many researchers believed that they offer valuable markers for identifying genes responsible for susceptibility to common diseases. In some cases, they are direct causes of human disease. One SNP can increase risk of cancer, but when considering the rate of overlap and frequency of DNA repair pathways, it might be expected that SNP alone cannot affect the final result of cancer, although several SNPs together can exert a significant influence. Therefore identification of these SNPs is very important. The most important loci which include mutations are: MLH1, MSH2, PMS2, APC, MUTYH, SMAD7, STK11, XRCC3, DNMT1, MTHFR, Exo1, XRCC1 and VDR. Presence of SNPs in these genes decreases or increases risk of colorectal cancer.

MATERIALS AND METHODS

In this article we reviewed the Genes and SNPs associated with non-hereditary and hereditary of colorectal cancer that recently were reported from candidate gene y, meta-analysis and GWAS studies.

RESULTS

As with other cancers, colorectal cancer is associated with SNPs in gene loci. Generally, by exploring SNPs, it is feasible to predict the risk of developing colorectal cancer and thus establishing proper preventive measures.

CONCLUSIONS

SNPs of genes associated with colorectal cancer can be used as a marker SNP panel as a potential tool for improving cancer diagnosis and treatment planning.

Polymorphisms in DNA repair genes and breast cancer risk in Russian population: a case-control study

Genetic variation in DNA repair genes can alter an individual's capacity to repair damaged DNA and influence the risk of cancer. We tested seven polymorphisms in DNA repair genes XRCC1, ERCC2, XRCC3, XRCC2, EXOI and TP53 for a possible association with breast cancer risk in a sample of 672 case and 672 control Russian women. An association was observed for allele A of the polymorphism XRCC1 (R399Q) rs25487 (co-dominant model AA vs. GG: OR 1.76, P = 0.003; additive model OR 1.28, P = 0.005; dominant model: OR 1.29, P = 0.03; recessive model OR 1.63, P = 0.008). Allele T of the polymorphism ERCC2 (D312N) rs1799793 was also associated with breast cancer risk (co-dominant model TT vs. CC: OR 1.43, P = 0.04; additive model OR 1.21, P = 0.02; dominant model: OR 1.30, P = 0.02), but the association became insignificant after applying Bonferroni correction. No association with breast cancer was found for the remaining SNPs. In summary, our study provides evidence that polymorphisms in DNA repair genes may play a role in susceptibility to breast cancer in the population of ethnical Russians.

Oxidatively induced DNA damage and its repair in cancer

Oxidatively induced DNA damage is caused in living organisms by endogenous and exogenous reactive species. DNA lesions resulting from this type of damage are mutagenic and cytotoxic and, if not repaired, can cause genetic instability that may lead to disease processes including carcinogenesis. Living organisms possess DNA repair mechanisms that include a variety of pathways to repair multiple DNA lesions. Mutations and polymorphisms also occur in DNA repair genes adversely affecting DNA repair systems. Cancer tissues overexpress DNA repair proteins and thus develop greater DNA repair capacity than normal tissues. Increased DNA repair in tumors that removes DNA lesions before they become toxic is a major mechanism for development of resistance to therapy, affecting patient survival. Accumulated evidence suggests that DNA repair capacity may be a predictive biomarker for patient response to therapy. Thus, knowledge of DNA protein expressions in normal and cancerous tissues may help predict and guide development of treatments and yield the best therapeutic response. DNA repair proteins constitute targets for inhibitors to overcome the resistance of tumors to therapy. Inhibitors of DNA repair for combination therapy or as single agents for monotherapy may help selectively kill tumors, potentially leading to personalized therapy. Numerous inhibitors have been developed and are being tested in clinical trials. The efficacy of some inhibitors in therapy has been demonstrated in patients. Further development of inhibitors of DNA repair proteins is globally underway to help eradicate cancer.

Genetic association between cyclin D1 polymorphism and breast cancer susceptibility

Cyclin D1 polymorphism has been reported to be associated with risk of breast cancer, but the published studies have yielded controversial results. This study was undertaken to derive a precise risk estimate for the cyclin D1 polymorphism associated with breast cancer risk. We performed a search of EMBASE, PubMed, and Web of Science. In total, data from 18 publications were pooled and the association was assessed by odds ratios (ORs) with 95 % confidence intervals (CIs). This analysis showed that there was no obvious association between the cyclin D1 polymorphism and breast cancer risk in any of the analyzed genetic model. We found the same negative association in stratified analyses by ethnicity, source of controls, and sample size. Our meta-analysis provides an estimate that the presence of cyclin D1 polymorphism may not confer susceptibility to breast cancer.

Polymorphisms in nucleotide excision repair genes and susceptibility to colorectal cancer in the Polish population

Xeroderma pigmentosum (XP) is a rare autosomal recessive disease that is associated with a severe deficiency in nucleotide excision repair. Genetic polymorphisms in XP genes may be associated with a change in DNA repair capacity, which could be associated with colorectal cancer development. We assessed the association between 94 single nucleotide polymorphisms (SNPs) within seven XP genes (XPA-XPG) and the colorectal cancer risk in the Polish population. We genotyped 758 unselected patients with colorectal cancer and 1,841 healthy adults. We found that a significantly decreased risk of colorectal cancer was associated with XPC polymorphism rs2228000_CT genotype (OR 0.59; p < 0.0001) and the rs2228000_TT genotype (OR 0.29; p < 0.0001) compared to the reference genotype (CC). And an increased disease risk was associated with the XPD SNP, rs1799793_AG genotype (OR 1.44, p = 0.018) and rs1799793_AA genotype (OR 3.31, p < 0.0001) compared to the reference genotype. Haplotype analysis within XPC, XPD and XPG revealed haplotypes associated with an altered colorectal cancer risk. Stratified analysis by gender showed differences between the association of three SNPs: XPC rs2228000, XPD rs1799793 and XPD rs238406 in females and males. Association analysis between age of disease onset and polymorphisms in XPD (rs1799793) and XPC (rs2228000) revealed differences in the prevalence of these variants in patients under and over 50 years of age. Our results confirmed that polymorphisms in XPC and XPD may be associated with the risk of colorectal cancer.

Effect of APE1 T2197G (Asp148Glu) polymorphism on APE1, XRCC1, PARP1 and OGG1 expression in patients with colorectal cancer

It has been hypothesized that genetic variation in base excision repair (BER) might modify colorectal adenoma risk. Thus, we evaluated the influence of APE1 T2197G (Asp148Glu) polymorphism on APE1, XRCC1, PARP1 and OGG1 expression in normal and tumor samples from patients with colorectal cancer. The results indicate a downregulation of OGG1 and an upregulation of XRCC1 expression in tumor tissue. Regarding the anatomical location of APE1, OGG1 and PARP-1, a decrease in gene expression was observed among patients with cancer in the rectum. In patients with or without some degree of tumor invasion, a significant downregulation in OGG1 was observed in tumor tissue. Interestingly, when taking into account the tumor stage, patients with more advanced grades (III and IV) showed a significant repression for APE1, OGG1 and PARP-1. XRCC1 expression levels were significantly enhanced in tumor samples and were correlated with all clinical and histopathological data. Concerning the polymorphism T2197G, GG genotype carriers exhibited a significantly reduced expression of genes of the BER repair system (APE1, XRCC1 and PARP1). In summary, our data show that patients with colorectal cancer present expression changes in several BER genes, suggesting a role for APE1, XRCC1, PARP1 and OGG1 and APE1 polymorphism in colorectal carcinogenesis.

Association between OGG1 Ser326Cys and APEX1 Asp148Glu polymorphisms and breast cancer risk: a meta-analysis

BACKGROUND

The base excision repair (BER) pathway removes DNA damage caused by ionizing radiation, reactive oxidative species and methylating agents. OGG1 and APE1 are two important genes in the BER pathway. Many epidemiological studies have evaluated the association between polymorphisms in the two BER genes (OGG1 Ser326Cys and APE1 Asp148Glu) and breast cancer risk. However, the results are inconsistent.

METHODS

We searched the electronic databases including PubMed, Embase and Cochrane library for all eligible studies for the period up to February 2014. Data were extracted by two independent authors and pooled odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were used to assess the strength of the association.

RESULTS

A total of 17 studies including 9,040 cases and 10,042 controls were available for OGG1 Ser326Cys polymorphism and 7 studies containing 2,979 cases and 3,111 controls were included for APE1 Asp148Glu polymorphism. With respect to OGG1 Ser326Cys polymorphism, we did not find a significant association with breast cancer risk when all eligible studies were pooled into the meta-analysis. However, in subgroup analyses by ethnicity and menopausal status, statistical significant increased breast cancer risk was found in Asian populations (Cys/Cys vs. Ser/Ser: OR=1.157, 95% CI 1.013-1.321, P=0.011; Cys/Cys vs. Ser/Cys+Ser/Ser: OR=1.113, 95% CI 1.009-1.227, P=0.014) and postmenopausal patients (Cys/Cys vs. Ser/Cys+Ser/Ser: OR=1.162, 95% CI 1.003-1.346, P=0.024). In subgroup analysis according to quality score, source of control, and HWE in controls, no any significant association was detected. With respect to APE1 Asp148Glu polymorphism, no significant association with breast cancer risk was demonstrated in the overall and stratified analyses.

CONCLUSIONS

The present meta-analysis suggests that the OGG1 Ser326Cys polymorphism may be a risk factor for breast cancer in Asians and postmenopausal patients. Further large and well-designed studies are needed to confirm this association.

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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.

No association between XRCC3 Thr241Met and XPD Lys751Gln polymorphisms and the risk of colorectal cancer in West Algerian population: a case-control study

Colorectal cancer (CRC) is a complex and multifactorial disease, in which genetic and environmental factors both seem to play a part. Many epidemiological studies have explored the association between genetic polymorphisms of X-ray repair cross-complementing group 3 (XRCC3) (Thr241Met) and Xeroderma pigmentosum group D (XPD) lysine to glutamine at codon 751 (Lys751Gln) and risk of CRC in various populations; however, the results are controversial. We conducted this case-control study in a West Algerian population to assess the potential role of this genetic polymorphism on the risk of CRC in this population. Genomic DNA was extracted from blood samples collected from 129 sporadic CRC patients and 148 normal controls. The polymorphisms were determined by pyrosequencing technique. The distribution of XRCC3 Thr241Met and XPD Lys751Gln genotypes among controls did not differ significantly from those predicted by the Hardy-Weinberg distribution (p > 0.05). There were no significant differences in the genotypes distribution and allele frequencies between CRC patients and controls. A significant association was found between the combined heterozygous of XRCC3 and homozygous variant of XPD gene and CRC. This is the first study on DNA repair genetic polymorphisms in West Algerian population, and it suggests that the XRCC3 Thr241Met and XPD Lys751Gln polymorphisms may not be associated with the CRC risk in this population.

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.

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