Polymorphisms in base excision repair genes and thyroid cancer risk

Polymorphisms of DNA Repair Genes in Thyroid Cancer

The incidence of thyroid cancer, one of the most common forms of endocrine cancer, is increasing rapidly worldwide in developed and developing countries. Various risk factors can increase susceptibility to thyroid cancer, but particular emphasis is put on the role of DNA repair genes, which have a significant impact on genome stability. Polymorphisms of these genes can increase the risk of developing thyroid cancer by affecting their function. In this article, we present a concise review on the most common polymorphisms of selected DNA repair genes that may influence the risk of thyroid cancer. We point out significant differences in the frequency of these polymorphisms between various populations and their potential relationship with susceptibility to the disease. A more complete understanding of these differences may lead to the development of effective prevention strategies and targeted therapies for thyroid cancer. Simultaneously, there is a need for further research on the role of polymorphisms of previously uninvestigated DNA repair genes in the context of thyroid cancer, which may contribute to filling the knowledge gaps on this subject.

Papillary Thyroid Cancer Remodels the Genetic Information Processing Pathways

The genetic causes of the differentiated, highly treatable, and mostly non-fatal papillary thyroid cancer (PTC) are not yet fully understood. The mostly accepted PTC etiology blames the altered sequence or/and expression level of certain biomarker genes. However, tumor heterogeneity and the patient's unique set of favoring factors question the fit-for-all gene biomarkers. Publicly accessible gene expression profiles of the cancer nodule and the surrounding normal tissue from a surgically removed PTC tumor were re-analyzed to determine the cancer-induced alterations of the genomic fabrics responsible for major functional pathways. Tumor data were compared with those of standard papillary and anaplastic thyroid cancer cell lines. We found that PTC regulated numerous genes associated with DNA replication, repair, and transcription. Results further indicated that changes of the gene networking in functional pathways and the homeostatic control of transcript abundances also had major contributions to the PTC phenotype occurrence. The purpose to proliferate and invade the entire gland may explain the substantial transcriptomic differences we detected between the cells of the cancer nodule and those spread in homo-cellular cultures (where they need only to survive). In conclusion, the PTC etiology should include the complex molecular mechanisms involved in the remodeling of the genetic information processing pathways.

XRCC1 Arg194Trp polymorphism and thyroid cancer

BACKGROUND

Previously published data on the association between the XRCC1 Arg194Trp polymorphism and thyroid cancer (TC) remain controversial.

METHODS

To clarify the association between the XRCC1 Arg194Trp polymorphism and susceptibility to TC, a meta-analysis of case-control studies was conducted. We systematically searched PubMed and CNKI to identify relevant studies. Pooled odds ratios (ORs) of various genetic models were estimated using fixed and random effects models. Heterogeneity was detected by Q-statistic, and the Egger's test was used to evaluate the publication bias.

RESULTS

A total of seven eligible studies for the XRCC1 Arg194Trp polymorphism (1500 patients and 2358 controls) were included in this meta-analysis. The results of our study failed to suggest an association between the Arg194Trp polymorphism and susceptibility of TC. However, in the subgroup analyses by ethnicity, the OR was 0.82 (C allele vs. T allele, 95% CI 0.68-0.98; P = 0.24 for heterogeneity) among the Chinese population. Nevertheless, no significant differences were observed in the Caucasian population in any genetic model.

CONCLUSION

This study suggested that the C allele of XRCC1 had an 18% significantly decreased risk of TC in Chinese, and there were no significant associations among Caucasians under all genetic models.

Overview of biological mechanisms of human carcinogens

This review summarizes the carcinogenic mechanisms for 109 Group 1 human carcinogens identified as causes of human cancer through Volume 106 of the IARC Monographs. The International Agency for Research on Cancer (IARC) evaluates human, experimental and mechanistic evidence on agents suspected of inducing cancer in humans, using a well-established weight of evidence approach. The monographs provide detailed mechanistic information about all carcinogens. Carcinogens with closely similar mechanisms of action (e.g. agents emitting alpha particles) were combined into groups for the review. A narrative synopsis of the mechanistic profiles for the 86 carcinogens or carcinogen groups is presented, based primarily on information in the IARC monographs, supplemented with a non-systematic review. Most carcinogens included a genotoxic mechanism.

Thyroid Cancer: The Quest for Genetic Susceptibility Involving DNA Repair Genes

The incidence of thyroid cancer (TC), particularly well-differentiated forms (DTC), has been rising and remains the highest among endocrine malignancies. Although ionizing radiation (IR) is well established on DTC aetiology, other environmental and genetic factors may also be involved. DNA repair single nucleotide polymorphisms (SNPs) could be among the former, helping in explaining the high incidence. To further clarify the role of DNA repair SNPs in DTC susceptibility, we analyzed 36 SNPs in 27 DNA repair genes in a population of 106 DTCs and corresponding controls with the aim of interpreting joint data from previously studied isolated SNPs in DNA repair genes. Significant associations with DTC susceptibility were observed for XRCC3 rs861539, XPC rs2228001, CCNH rs2230641, MSH6 rs1042821 and ERCC5 rs2227869 and for a haplotype block on chromosome 5q. From 595 SNP-SNP combinations tested and 114 showing relevance, 15 significant SNP combinations (p < 0.01) were detected on paired SNP analysis, most of which involving CCNH rs2230641 and mismatch repair variants. Overall, a gene-dosage effect between the number of risk genotypes and DTC predisposition was observed. In spite of the volume of data presented, new studies are sought to provide an interpretability of the role of SNPs in DNA repair genes and their combinations in DTC susceptibility.

Downregulated LRRK2 gene expression inhibits proliferation and migration while promoting the apoptosis of thyroid cancer cells by inhibiting activation of the JNK signaling pathway

Emerging studies have indicated that leucine-rich repeat kinase 2 (LRRK2) is associated with thyroid cancer (TC). The present study investigated the effect of LRRK2 on the cell cycle and apoptosis in TC, and examined the underlying mechanisms in vitro. To screen TC-associated differentially expressed genes, gene expression microarray analysis was conducted. Retrieval of pathways associated with TC from the Kyoto Encyclopedia of Genes and Genomes database indicated that the c-Jun N-terminal kinase (JNK) signaling pathway serves an essential role in TC. SW579, IHH-4, TFC-133, TPC-1 and Nthy-ori3-1 cell lines were used to screen cell lines with the highest and lowest LRRK2 expression for subsequent experiments. The two selected cell lines were transfected with pcDNA-LRRK2, or small interfering RNA against LRRK2 or SP600125 (a JNK inhibitor). Subsequently, flow cytometry, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling, a 5-ethynyl-2′-deoxyuridine assay and a scratch test was conducted to detect the cell cycle distribution, apoptosis, proliferation and migration, respectively, in each group. The LRRK2 gene was determined to be elevated in TC based on the microarray data of the GSE3678 dataset. The SW579 cell line was identified to exhibit the highest LRRK2 expression, while IHH-4 cells exhibited the lowest LRRK2 expression. LRRK2 silencing, through inhibiting the activation of the JNK signaling pathway, increased the expression levels of genes and proteins associated with cell cycle arrest and apoptosis in TC cells, promoted cell cycle arrest and apoptosis, and inhibited cell migration and proliferation in TC cells, indicating that LRRK2 repression could exert beneficial effects through the JNK signaling pathway on TC cells. These observations demonstrate that LRRK2 silencing promotes TC cell growth inhibition, and facilitates apoptosis and cell cycle arrest. The JNK signaling pathway may serve a crucial role in mediating the anti-carcinogenic activities of downregulated LRRK2 in TC.

Interaction among susceptibility genotypes of PARP1 SNPs in thyroid carcinoma

Polymorphisms in DNA repair genes may alter the repair mechanism which makes the person susceptible to DNA damage. Polymorphic variants in these DNA repair pathway genes such as Poly (ADP-ribose) polymerase- 1 (PARP1) have been associated with susceptibility of several types of cancer including thyroid. Many studies have been published on PARP1 gene polymorphisms and carcinogenesis with inconsistent results. The present study was designed to explore the link between the PARP1 polymorphisms and thyroid cancer risk. This case-control study was comprised of 456 thyroid cancer patients and 400 healthy controls. Three SNPs of PARP1 gene; rs1136410, rs1805414 and rs1805404 were analyzed using ARMS-PCR. The combined genotype and haplotype analysis were performed using haploview software 4.2. Major allele homozygote (CC) of rs1136410 and combined genotype (TT+TC) of rs180414 showed a significant association with thyroid cancer risk (OR = 1.30; 95% CI 0.99–1.77; P = 0.05) and (OR = 0.43; 95% CI = 0.27–0.67; P = 0.03). Histological subtype analysis showed the significant association of selected PARP1 SNPs with papillary, follicular and anaplastic subtypes in thyroid cancer patients. Haplotype analysis showed that TCT (p = 0.01), CTT (p = 0.02) and CTC (p = 0.03) were significantly higher in controls when compared to cases. However, TTC (p = 0.05) and TCC (p = 0.01) haplotype frequency was significantly higher in cases compared to controls. Global haplotype analysis showed that there was an overall significant difference between cases and controls (p = 0.001). Identification of these genetic risk markers may provide evidence for exploring insight into mechanisms of pathogenesis and subsequently aid in developing novel therapeutic strategies for thyroid cancer.

Polymorphisms of base-excision repair genes and the hepatocarcinogenesis

AIM

To determine the possible association between polymorphisms of DNA repair genes, including XRCC1 Arg194Tryp, Arg280His, and Arg399Glu, APE1 Asp148Glu, and NEIL2 Arg257Leu, and the risk of developing hepatitis C virus (HCV)-related hepatocellular carcinoma (HCC).

METHODS

A total of 264 subjects were recruited in this retrospective case-control study and were categorized into four groups: 88 control subjects (CR), 53 chronic hepatitis C patients (CHC), 36 liver cirrhotic patients (LC), and 87 HCC patients. The XRCC1 Arg194Tryp, Arg280His, and Arg399Glu polymorphisms were detected using PCR-RFLP, while real-time PCR was used to genotype APE1 Asp148Glu and NEIL2 Arg257Leu.

RESULTS

Our data revealed that, compared with the healthy controls, for those subjects with the XRCC1 Arg194Trp genotype, the risk of developing CHC, LC, and HCC was increased by 6.66- (odds ratio (OR) = 6.667; 95% confidence interval (CI) = 3.244-13.701; P > 0.01), 3.85- (OR = 3.852; 95% CI = 1.797-8.256; P > 0.01), and 2.14-fold (OR = 2.14; 95% CI = 1.13-4.06; P > 0.05), respectively. There was no association between the risk of HCC development and the XRCC1 Arg280His or XRCC1 Arg399Gln genotypes. Moreover, the analysis showed a lack of association between APE1 Asp148Glu and the risk of HCC development. The analysis of clinicopathological parameters showed that the HCC patients with the XRCC1 Arg280His polymorphism were 2.9 fold more likely to have hepatic lesions in both hepatic lobes (OR: 2.9; 95% CI: 1.15-7.29). Notably, in the HCC patients, the prevalence of the APE1 polymorphism in the males was four times higher than that in the females (OR = 4; 95% CI = 1.129-14.175; P > 0.05).

CONCLUSION

Our results indicate that the XRCC1 Arg194Trp polymorphism could be a risk factor for HCV-related HCC development in Egypt.

Mismatch repair single nucleotide polymorphisms and thyroid cancer susceptibility

Thyroid cancer (TC) is the most common endocrine malignancy and its incidence continues to rise worldwide. Ionizing radiation exposure is the best established etiological factor. Heritability is high; however, despite valuable contribution from recent genome-wide association studies, the current understanding of genetic susceptibility to TC remains limited. Several studies suggest that altered function or expression of the DNA mismatch repair (MMR) system may contribute to TC pathogenesis. Therefore, the present study aimed to evaluate the potential role of a panel of MMR single nucleotide polymorphisms (SNPs) on the individual susceptibility to well-differentiated TC (DTC). A case-control study was performed involving 106 DTC patients and 212 age- and gender-matched controls, who were all Caucasian Portuguese. Six SNPs present in distinct MMR genes (MLH1 rs1799977, MSH3 rs26279, MSH4 rs5745325, PMS1 rs5742933, MLH3 rs175080 and MSH6 rs1042821) were genotyped through TaqMan^® assays and genotype-associated risk estimates were calculated. An increased risk was observed in MSH6 rs1042821 variant homozygotes [adjusted odds ratio (OR)=3.42, 95% CI: 1.04-11.24, P=0.04, under the co-dominant model; adjusted OR=3.84, 95% CI: 1.18-12.44, P=0.03, under the recessive model]. The association was especially evident for the follicular histotype and female sex. The association was also apparent when MSH6 was analysed in combination with other MMR SNPs such as MSH3 rs26279. Interestingly, two other SNP combinations, both containing the MSH6 heterozygous genotype, were associated with a risk reduction, suggesting a protective effect for these genotype combinations. These data support the idea that MMR SNPs such as MSH6 rs1042821, alone or in combination, may contribute to DTC susceptibility. This is coherent with the limited evidence available. Nevertheless, further studies are needed to validate these findings and to establish the usefulness of these SNPs as genetic susceptibility biomarkers for DTC so that, in the near future, cancer prevention policies may be optimized under a personalized medicine perspective.

Investigation of DNA repair-related SNPs underlying susceptibility to papillary thyroid carcinoma reveals MGMT as a novel candidate gene in Belarusian children exposed to radiation

BACKGROUND

Genetic factors may influence an individual's sensitivity to ionising radiation and therefore modify his/her risk of developing papillary thyroid carcinoma (PTC). Previously, we reported that common single nucleotide polymorphisms (SNPs) within the DNA damage recognition gene ATM contribute to PTC risk in Belarusian children exposed to fallout from the Chernobyl power plant accident. Here we explored in the same population the contribution of a panel of DNA repair-related SNPs in genes acting downstream of ATM.

METHODS

The association of 141 SNPs located in 43 DNA repair genes was examined in 75 PTC cases and 254 controls from the Gomel region in Belarus. All subjects were younger than 15 years at the time of the Chernobyl accident. Conditional logistic regressions accounting for radiation dose were performed with PLINK using the additive allelic inheritance model, and a linkage disequilibrium (LD)-based Bonferroni correction was used for correction for multiple testing.

RESULTS

The intronic SNP rs2296675 in MGMT was associated with an increased PTC risk [per minor allele odds ratio (OR) 2.54 95% CI 1.50, 4.30, P per allele = 0.0006, P corr.= 0.05], and gene-wide association testing highlighted a possible role for ERCC5 (P Gene = 0.01) and PCNA (P Gene = 0.05) in addition to MGMT (P Gene = 0.008).

CONCLUSIONS

These findings indicate that several genes acting in distinct DNA repair mechanisms contribute to PTC risk. Further investigation is needed to decipher the functional properties of the methyltransferase encoded by MGMT and to understand how alteration of such functions may lead to the development of the most common type of thyroid cancer.

DNA repair genes polymorphisms and genetic susceptibility to Philadelphia-negative myeloproliferative neoplasms in a Portuguese population: The role of base excision repair genes polymorphisms

The role of base excision repair (BER) genes in Philadelphia-negative (PN)-myeloproliferative neoplasms (MPNs) susceptibility was evaluated by genotyping eight polymorphisms [apurinic/apyrimidinic endodeoxyribonuclease 1, mutY DNA glycosylase, earlier mutY homolog (E. coli) (MUTYH), 8-oxoguanine DNA glycosylase 1, poly (ADP-ribose) polymerase (PARP) 1, PARP4 and X-ray repair cross-complementing 1 (XRCC1)] in a case-control study involving 133 Caucasian Portuguese patients. The results did not reveal a correlation between individual BER polymorphisms and PN-MPNs when considered as a whole. However, stratification for essential thrombocythaemia revealed i) borderline effect/tendency to increased risk when carrying at least one variant allele for XRCC1_399 single-nucleotide polymorphism (SNP); ii) decreased risk for Janus kinase 2-positive patients carrying at least one variant allele for XRCC1_399 SNP; and iii) decreased risk in females carrying at least one variant allele for MUTYH SNP. Combination of alleles demonstrated an increased risk to PN-MPNs for one specific haplogroup. These findings may provide evidence for gene variants in susceptibility to MPNs. Indeed, common variants in DNA repair genes may hamper the capacity to repair DNA, thus increasing cancer susceptibility.

Genetic Association of XRCC1 Gene rs1799782, rs25487 and rs25489 Polymorphisms with Risk of Thyroid Cancer: a Systematic Review and Meta-Analysis

Background:

A number of case-control studies have evaluated associations between the X-ray cross complementary group 1 protein (XRCC1) gene rs1799782 (Arg194Trp), rs25487 (Arg399Gln) and rs25489 (Arg280His) polymorphisms and thyroid cancer (TC) risk, but the results remain inconclusive.

Materials and Methods:

A systematic literature search was performed using PubMed and Google Scholar Search. According to defined criteria data were extracted and pooled odds ratios with 95% confidence intervals were calculated under five genetic models.

Results:

A total of 8 studies with 1,672 cases and 2,805 controls for the rs1799782 polymorphism, 14 studies with 2,506 cases and 5,180 controls for the rs25487 polymorphism, and 11 studies with 2,197 cases and 4,761 controls for the rs25489 polymorphism were included in this meta-analysis. Overall, there was a statistical association between XRCC1 rs1799782 polymorphism and TC risk with the homozygote genetic model (TT vs. CC: OR = 1.815, 95% CI = 1.115-2.953, p= 0.016) and the recessive genetic model (TT vs. TC+ CC: OR = 1.854, 95% CI = 1.433-2.399, p= <0.001). In the subgroup analysis by ethnicity, significantly increased TC risk was observed only in Asians under the recessive model (TT vs. TC+ CC: OR = 1.816, 95% CI = 1.398-2.358, p= <0.001). In addition, there was no positive association between XRCC1 rs25487 and rs25489 polymorphisms and risk of TC. However, there was a significant association between XRCC1 rs25487 polymorphism risk of TC among Caucasians with allele genetic comparison (A vs. G: OR= 0.882, 95% CI = 0.794-0.979, p= 0.136) and dominant genetic comparison (AA+AG vs. GG: OR=0.838, 95% CI = 0.728-0.965, p= 0.014).

Conclusions:

The results of our meta-analysis suggest an increased risk of TC with the XRCC1 rs1799782 and rs25487 polymorphisms. However, the XRCC1 rs25489 polymorphism appeared to be without influence.

Molecular genetics of thyroid cancer

The pathogenesis of the development and progression of thyroid cancer (TC) is far from being clear at present. Accumulated evidence suggests that it is a complex polygenic disorder for which genetic factors play an important role in disease aetiology. Here we review the literature to report the genetic variations and alterations that have been described in the aetiology of TC. The functional effects of some mutations and single nucleotide polymorphisms on TC are validated, establishing the role of sequence variations in this cancer. However, large prospective studies are still required to evaluate the diagnostic and prognostic value of these genetic determinants in clinical practice.

A Comprehensive Meta-analysis of Case-Control Association Studies to Evaluate Polymorphisms Associated with the Risk of Differentiated Thyroid Carcinoma

BACKGROUND

Linkage analyses and association studies suggested that inherited genetic variations play a role in the development of differentiated thyroid carcinoma (DTC).

METHODS

We combined the results from a genome-wide association study (GWAS) performed by our group and from published studies on DTC. With a first approach, we evaluated whether a SNP published as associated with the risk of DTC could replicate in our GWAS (using FDR as adjustment for multiple comparisons). With the second approach, meta-analyses were performed between literature and GWAS when both sources suggested an association, increasing the statistical power of the analysis.

RESULTS

rs1799814 (CYP1A1), rs1121980 (FTO), and 3 SNPs within 9q22 (rs965513, rs7048394, and rs894673) replicated the associations described in the literature. In addition, the meta-analyses between literature and GWAS revealed 10 more SNPs within 9q22, six within FTO, two within SOD1, and single variations within HUS1, WDR3, UGT2B7, ALOX12, TICAM1, ATG16L1, HDAC4, PIK3CA, SULF1, IL11RA, VEGFA, and 1p31.3, 2q35, 8p12, and 14q13.

CONCLUSION

This analysis confirmed several published risk loci that could be involved in DTC predisposition.

IMPACT

These findings provide evidence for the role of germline variants in DTC etiology and are consistent with a polygenic model of the disease. Cancer Epidemiol Biomarkers Prev; 25(4); 700-13. ©2016 AACR.

Cancer Drug Resistance: A Brief Overview from a Genetic Viewpoint

Cancer drug resistance leading to therapeutic failure in the treatment of many cancers encompasses various mechanisms and may be intrinsic relying on the patient's genetic makeup or be acquired by tumors that are initially sensitive to cancer drugs. All in all, it may be responsible for treatment failure in over 90 % of patients with metastatic cancer. Cancer drug resistance, in particular acquired resistance, may stem from the micro-clonality/micro-genetic heterogeneity of the tumors whereby, among others, the following mechanisms may entail resistance: altered expression of drug influx/efflux transporters in the tumor cells mediating lower drug uptake and/or greater efflux of the drug; altered role of DNA repair and impairment of apoptosis; role of epigenomics/epistasis by methylation, acetylation, and altered levels of microRNAs leading to alterations in upstream or downstream effectors; mutation of drug targets in targeted therapy and alterations in the cell cycle and checkpoints; and tumor microenvironment that are briefly reviewed.

OGG1 Mutations and Risk of Female Breast Cancer: Meta-Analysis and Experimental Data

In first part of this study association between OGG1 polymorphisms and breast cancer susceptibility was explored by meta-analysis. Second part of the study involved 925 subjects, used for mutational analysis of OGG1 gene using PCR-SSCP and sequencing. Fifteen mutations were observed, which included five intronic mutations, four splice site mutations, two 3'UTR mutations, three missense mutations, and a nonsense mutation. Significantly (p < 0.001) increased (~29 fold) breast cancer risk was associated with a splice site variant g.9800972T>G and 3'UTR variant g.9798848G>A. Among intronic mutations, highest (~15 fold) increase in breast cancer risk was associated with g.9793680G>A (p < 0.009). Similarly ~14-fold increased risk was associated with Val159Gly (p < 0.01), ~17-fold with Gly221Arg (p < 0.005), and ~18-fold with Ser326Cys (p < 0.004) in breast cancer patients compared with controls, whereas analysis of nonsense mutation showed that ~13-fold (p < 0.01) increased breast cancer risk was associated with Trp375STOP in patients compared to controls. In conclusion, a significant association was observed between OGG1 germ line mutations and breast cancer risk. These findings provide evidence that OGG1 may prove to be a good candidate of better diagnosis, treatment, and prevention of breast cancer.

MUTYH association with esophageal adenocarcinoma in a Han Chinese population

Adenocarcinoma of esophagus (AE) is a complex disease, affected by a variety of genetic and environmental factors. Much evidence has shown that the MutY glycosylase homologue (MUTYH) plays a key role in the pathogenesis of many cancers. However, there have been no reports on influence on AE in the Han Chinese population. The objective of this study was to investigate this issue. A gene-based association study was conducted using three single nucleotide polymorphisms(SNPs) reported in previous studies. The three SNPs (rs3219463, rs3219472, rs3219489) were genotyped in 207 unrelated AE patients and 249 healthy controls in a case-control study using polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP). The results revealed that the genotype distribution of rs3219472 differed between the case and control groups (OR=1.66,95%CI=1.11-2.48, P=0.012 ), indicating that an association may exist between MUTYH and AE. These findings support a signifcant role for MUTYH in AE pathogenesis in the Han Chinese population.

Association between the XRCC1 polymorphisms and thyroid cancer risk: a meta-analysis from case-control studies

Background

The previous published data on the association between the X-ray repair cross-conplementation group 1 (XRCC1) polymorphisms and thyroid cancer risk remained controversial. Hence, we performed a meta-analysis on all available studies that provided 1729 cases and 3774 controls (from 11 studies) for XRCC1 Arg399Gln, 1040 cases and 2487 controls for Arg194Trp (from 7 studies), and 1432 cases and 3356 controls for Arg280His (from 8 studies).

Methodology/Principal Findings

PubMed, CNKI, and EMBASE database were searched to identify relevant studies. Overall, no significant association was found between XRCC1 Arg399Gln (recessive model: OR = 0.95, 95% CI = 0.77–1.15; dominant model: OR = 0.89, 95% CI = 0.75–1.05; homozygote model: OR = 0.92, 95% CI = 0.69–1.23; Heterozygote model: OR = 0.91, 95% CI = 0.80–1.03; additive model: OR = 0.93, 95% CI = 0.81–1.07), Arg194Trp (recessive model: OR = 1.41, 95% CI = 0.62–3.23; dominant model: OR = 1.01, 95% CI = 0.77–1.34; homozygote model: OR = 1.42, 95% CI = 0.55–3.67; Heterozygote model: OR = 1.03, 95% CI = 0.85–1.26; additive model: OR = 1.08, 95% CI = 0.81–1.42), and Arg280His (recessive model: OR = 1.08, 95% CI = 0.56–2.10; dominant model: OR = 1.01, 95% CI = 0.84–1.22; homozygote model: OR = 1.00, 95% CI = 0.51–1.96; Heterozygote model: OR = 1.04, 95% CI = 0.75–1.42; additive model: OR = 1.03, 95% CI = 0.86–1.23) and thyroid cancer risk when all the eligible studies were pooled into the meta-analysis. In the further stratified and sensitivity analyses, significant association was still not found in these three genetic polymorphisms.

Conclusions/Significance

In summary, this meta-analysis indicates that XRCC1 Arg399Gln, Arg280His, and Arg194Trp are not associated with thyroid cancer.

No association between XRCC1 genetic polymorphisms and differentiated thyroid carcinoma risk: a meta-analysis

The X-ray repair cross-complementing group 1 (XRCC1) gene belongs to the family of DNA repair genes. Polymorphisms in the XRCC1 gene, Arg399Gln, Arg194Trp and Arg280His, have been reported to have implications in differentiated thyroid carcinoma (DTC) susceptibility, but the results remain conflicting and no meta-analysis has been published. Therefore, we carried out a systematic review of the published epidemiology studies, aiming to assess the relationship between XRCC1 polymorphisms and susceptibility to DTC risk. We selected three databases, PubMed, EMBASE and CNKI, in which to search for published literature. With respect to DTC risk associated with XRCC1, combined odds ratios (ORs) and 95% confidence intervals (CI) were appropriately calculated on the basis of co-dominant, dominant and recessive models. To investigate different effects from specific race, subgroup analyses were carried out in Asian and Caucasian populations. Eight studies meeting the inclusion criteria were eventually selected for Arg399Gln (1,550 cases and 2,692 controls), five studies for Arg194Trp (858 cases and 1,394 controls) and five studies for Arg280His (1,237 cases and 2,267 controls). The combined results of the relevant studies exhibited that no significant associations with DTC risk were demonstrated for polymorphisms in XRCC1 Arg399Gln, Arg194Trp and Arg280His in all genetic models. Stratified analyses in Asian and Caucasian populations showed similar results. This meta-analysis arrives at a conclusion that the XRCC1 (Arg399Gln, Arg194Trp, Arg280His) polymorphisms appear to confer no risk for DTC.

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%).

PARP-1 Val762Ala polymorphism and risk of cancer: a meta-analysis based on 39 case-control studies

Background

Poly(ADP-ribose) polymerase-1 (PARP-1) is a nuclear chromatin-associated enzyme involved in several important cellular processes, particularly in the DNA repair system. PARP-1 rs1136410: C>T is among the most studied polymorphisms and likely involved in human carcinogenesis. However, results from previous studies are inconclusive. Thus, a meta-analysis was conducted to derive a more precise estimation of the effects of this enzyme.

Methodology and Principal Findings

A comprehensive search was conducted in the PubMed and EMBASE databases until December 9, 2013. A total of 39 studies with 16,783 cancer cases and 23,063 control subjects were included in the meta-analysis on the basis of the inclusion and exclusion criteria. No significant association between the PARP-1 Val762Ala polymorphism and cancer risk was found when all of the studies were pooled into the analysis (VA + AA vs. VV: OR = 1.03, 95% CI = 0.95–1.11). The subgroup analysis of cancer types revealed that the –762Ala allele was associated with increased risk of gastric, cervical, and lung cancers and a decreased risk of glioma. In addition, a significantly increased risk of cancer associated with the polymorphism was observed in Asian descendents (VA + AA vs. VV: OR = 1.17, 95% CI = 1.09–1.25; AA vs. VV: OR = 1.28, 95% CI = 1.08–1.51; VA vs. VV: OR = 1.12, 95% CI = 1.04–1.20; AA vs. VA + VV: OR = 1.09, 95% CI = 1.03–1.39). These results also indicated that a joint effect between PARP-1 Val762Ala and XRCC1 Arg399Gln could be involved in the risk of cancer development (OR = 3.53, 95% CI = 1.30–9.59).

Conclusion

The present meta-analysis provides evidence that the PARP-1 Val762Ala may be involved in cancer development at least in some ethnic groups (Asian) or some specific cancer types (gastric, cervical, and lung cancers, and glioma).

Association of XRCC1 polymorphisms with thyroid cancer risk

Due to the important role in the DNA repair pathways, numerous studies have been carried out to explore the relationship between the polymorphisms in the X-ray repair cross-complementing group 1 (XRCC1) gene and thyroid cancer risk. But previous reports have produced conflicting results. Thus, we performed an updated comprehensive meta-analysis to better investigate the association of the XRCC1 polymorphisms with thyroid cancer risk. There were a total of nine studies included with 1,621 cases and 3,669 controls examining the effects of the XRCC1 Arg280His, Arg399Gln, and Arg194Trp polymorphisms on the susceptibility of thyroid cancer. In our study, the XRCC1 Arg280His polymorphism was found to be associated with an increased thyroid cancer risk in the Caucasian population [allelic contrast: odds ratio (OR) = 1.38, 95% CI = 1.05-1.80, P(Z) = 0.02, P(Q) = 0.61; dominant model: OR = 1.43, 95% CI = 1.08-1.89, P(Z) = 0.01, P(Q) = 0.57]. The Arg399Gln polymorphism was associated with a significant decreased risk [allelic contrast: OR = 0.73, 95% CI = 0.59-0.92, P(Z) = 0.006, P(Q) = 0.31; dominant model: OR = 0.73, 95% CI = 0.55-0.97, P(Z) = 0.03, P(Q) = 0.33; recessive model: OR = 0.56, 95% CI = 0.34-0.93, P(Z) = 0.02, P(Q) = 0.59], while the Arg194Trp SNP conferred an increased risk for thyroid cancer in the mixed populations [allelic contrast: OR = 1.49, 95% CI = 1.02-2.17, P(Z) = 0.04]. To conclude, the present meta-analysis demonstrated that the polymorphisms in the XRCC1 gene may be associated with developing of thyroid cancer.

Association between the PARP1 Val762Ala polymorphism and cancer risk: evidence from 43 studies

BACKGROUND

Poly (ADP-ribose) polymerase-1 (PARP-1) plays critical roles in the detection and repair of damaged DNA, as well as cell proliferation and death. Numerous studies have examined the associations between PARP1 Val762Ala (rs1136410 T>C) polymorphism and cancer susceptibility; nevertheless, the findings from different research groups remain controversial.

METHODS

We searched literatures from MEDLINE, EMBASE and CBM pertaining to such associations, and then calculated pooled odds ratio (OR) and 95% confidence interval (CI) by using random-effects model. The false-positive report probability (FPRP) analysis was used to confirm the validity of significant findings. Moreover, potential effects of rs1136410 variants on PARP1 mRNA expression were analyzed for three ethnicities by combining data from HapMap (genotype) and SNPexp (mRNA expression).

RESULTS

The final meta-analysis incorporated 43 studies, consisting of 17,351 cases and 22,401 controls. Overall, our results did not suggest significant associations between Ala variant (Ala/Ala or Ala/Val genotype) and cancer risk. However, further stratification analysis showed significantly increased risk for gastric cancer (Ala/Ala vs. Val/Val: OR = 1.56, 95% CI = 1.01-2.42, Ala/Val vs. Val/Val: OR = 1.34, 95% CI = 1.14-1.58, dominant model: OR = 1.41, 95% CI = 1.21-1.65 and Ala vs. Val: OR = 1.29, 95% CI = 1.07-1.55). On the contrary, decreased risk for brain tumor (Ala/Val vs. Val/Val: OR = 0.77, 95% CI = 0.68-0.87, dominant model: OR = 0.77, 95% CI = 0.68-0.87 and Ala vs. Val: OR = 0.82, 95% CI = 0.74-0.91). Additionally, we found that the Ala carriers had a significantly increased risk in all models for Asians. Our mRNA expression data provided further biological evidence to consolidate this finding.

CONCLUSIONS

Despite some limitations, this meta-analysis found evidence for an association between the PAPR1 Val762Ala and cancer susceptibility within gastric cancer, brain tumor and Asian subgroups.

The role of CCNH Val270Ala (rs2230641) and other nucleotide excision repair polymorphisms in individual susceptibility to well-differentiated thyroid cancer

Well-differentiated thyroid cancer (DTC) is the most common form of thyroid cancer (TC); however, with the exception of radiation exposure, its etiology remains largely unknown. Several single nucleotide polymorphisms (SNPs) have previously been implicated in DTC risk. Nucleotide excision repair (NER) polymorphisms, despite having been associated with cancer risk at other locations, have received little attention in the context of thyroid carcinogenesis. In order to evaluate the role of NER pathway SNPs in DTC susceptibility, we performed a case-control study in 106 Caucasian Portuguese DTC patients and 212 matched controls. rs2230641 (CCNH), rs2972388 (CDK7), rs1805329 (RAD23B), rs3212986 (ERCC1), rs1800067 (ERCC4), rs17655, rs2227869 (ERCC5), rs4253211 and rs2228529 (ERCC6) were genotyped using TaqMan® methodology, while conventional PCR-RFLP was employed for rs2228000 and rs2228001 (XPC). When considering all DTC cases, only rs2230641 (CCNH) was associated with DTC risk; a consistent increase in overall DTC risk was observed for both the heterozygous genotype (OR=1.89, 95% CI=1.14-3.14) and the variant allele carriers (OR=1.79, 95% CI=1.09-2.93). Histological stratification analysis confirmed an identical effect on follicular TC (OR=2.72, 95% CI=1.19-6.22, for heterozygous; OR=2.44, 95% CI=1.07‑5.55, for variant allele carriers). Considering papillary TC, the rs2228001 (XPC) variant genotype was associated with increased risk (OR=2.33, 95% CI=1.05-5.16), while a protective effect was observed for rs2227869 (ERCC5) (OR=0.26, 95% CI=0.08‑0.90, for heterozygous; OR=0.25, 95% CI=0.07-0.86, for variant allele carriers). No further significant results were observed. Our results suggest that NER polymorphisms such as rs2230641 (CCNH) and, possibly, rs2227869 (ERCC5) and rs2228001 (XPC), may influence DTC susceptibility. However, larger studies are required to confirm these results.

XRCC1 gene polymorphisms and the risk of differentiated thyroid carcinoma (DTC): a meta-analysis of case-control studies

Background

Previous studies investigating the association between X-ray repair cross-complementing group 1 (XRCC1) polymorphisms and thyroid cancer risk have yielded inconsistent results. This meta-analysis was performed to derive a more precise estimation of the relationship between three XRCC1 polymorphisms and thyroid cancer risk.

Methods/Principal Findings

PubMed and EMBASE database were systematically searched to identify relevant studies. 10 publications were selected for this meta-analysis, including 11 studies for Arg399Gln polymorphism (1726 cases and 3774 controls), 7 studies for Arg194Trp polymorphism (1037 cases and 2487 controls) and 8 studies for Arg280His polymorphism (1432 cases and 3356 controls). The results in total population did not show any significant association between these three polymorphisms and the risk of DTC for all genetic models. However, when stratified by ethnicity, the results showed that Arg280His polymorphism was associated with an increased risk of DTC among Caucasians (Arg/His vs. Arg/Arg: OR = 1.45, 95% CI = 1.09–1.93; dominant model: OR = 1.43, 95% CI = 1.08–1.89; additive model: OR = 1.38, 95% CI = 1.05–1.80), whereas individuals carrying Arg/His genotype have a significantly reduced risk of DTC among Asians (Arg/His vs. Arg/Arg: OR = 0.71, 95% CI = 0.51–0.98). We also detected that 399Gln variant allele carriers might presented an overall decreased risk of DTC in mixed population. Furthermore, subgroup analyses by histological subtype revealed that Arg194Trp polymorphism was significantly associated with reduced risk for papillary thyroid carcinoma (PTC) (dominant model: OR = 0.71, 95% CI = 0.50–0.99).

Conclusions

This meta-analysis suggests that Arg280His polymorphism might contribute to the susceptibility of DTC among Caucasians, whereas it might provide protective effects in Asians against the risk of DTC. Additionally, our results support the protective role of Arg194Trp polymorphism in developing PTC, and show evidence of an association between Arg399Gln polymorphism and decreased risk of DTC in mixed population.