A prospective study of XRCC1 (X-ray cross-complementing group 1) polymorphisms and breast cancer risk

Human Variation in DNA Repair, Immune Function, and Cancer Risk

DNA damage constantly threatens genome integrity, and DNA repair deficiency is associated with increased cancer risk. An intuitive and widely accepted explanation for this relationship is that unrepaired DNA damage leads to carcinogenesis due to the accumulation of mutations in somatic cells. But DNA repair also plays key roles in the function of immune cells, and immunodeficiency is an important risk factor for many cancers. Thus, it is possible that emerging links between inter-individual variation in DNA repair capacity and cancer risk are driven, at least in part, by variation in immune function, but this idea is underexplored. In this review we present an overview of the current understanding of the links between cancer risk and both inter-individual variation in DNA repair capacity and inter-individual variation in immune function. We discuss factors that play a role in both types of variability, including age, lifestyle, and environmental exposures. In conclusion, we propose a research paradigm that incorporates functional studies of both genome integrity and the immune system to predict cancer risk and lay the groundwork for personalized prevention.

Impact of XRCC1 genetic variants on its tissue expression and breast cancer risk: A case-control study

X-ray repair cross-complementing group 1 (XRCC1), a coordinator protein of the DNA repair complex, is thought to be involved in cancer progression. This case-control study aimed to investigate the association of two biallelic single-nucleotide polymorphisms (SNPs; Arg399Gln, Arg194Trp) of the XRCC1 gene with its tissue expression level and breast cancer (BC) risk in Egyptian women. This study included 100 BC female patients (case group 1) and 100 healthy females (control group 2). The XRCC1 tissue expression was assessed by immunohistochemistry (IHC). Genotyping of the two XRCC1 SNPs (Arg399Gln, Arg194Trp) using real-time polymerase chain reaction (PCR) was also conducted. The XRCC1 expression level was significantly lower in cancerous tissues than adjacent non-cancerous tissues (p < .001). The XRCC1 399Gln/Gln genotype, 399Gln allele, the dominant, and recessive models were significantly associated with lower XRCC1 expression in breast cancerous tissues and increased risk for BC (3.390-, 1.965-, 2.241-, and 2.429-folds, respectively). The XRCC1 399Gln/Gln genotype was associated with lower incidence of advanced tumor grade (OR: 0.06; 95%CI: 0.01-0.74; p = .028). Conversely, the XRCC1 Arg194Trp polymorphism did not show any significant association with either XRCC1 expression in breast cancer tissues or BC risk in all genetic models. The XRCC1 haplotypes, 399Gln/194Arg and 399Gln/194Trp, were associated with 1.800- and 1.675-folds risk for BC, respectively. The XRCC1 gene polymorphism (Arg399Gln) is associated with reduced XRCC1 tissue expression and enhanced BC risk with a well-differentiated nature in Egyptian women. Moreover, XRCC1 haplotypes, 399Gln/194Arg and 399Gln/194Trp, were associated with increased BC risk.

Genetic polymorphisms in DNA repair genes XRCC1 and 3 are associated with increased risk of breast cancer in Bangladeshi population

BACKGROUND

Genetic polymorphisms in DNA repair genes, XRCC1 (Arg399Gln) and XRCC3 (Thr241Met), may affect their DNA repair capacity leading to individual variation in breast cancer susceptibility among Bangladeshi females.

METHODS

The case-control study comprised 121 breast cancer patients and 133 healthy controls. Genomic DNA isolated from peripheral blood was genotyped for target SNPs using PCR-RFLP method.

RESULTS

For XRCC1, heterozygous Arg/Gln and homozygous Gln/Gln genotypes showed 1.78-fold (95% CI 1.0084 to 3.1442, p = 0.0467) and 2.41-fold (95% CI 1.0354 to 5.5914, p = 0.0413) increased risk of breast cancer, respectively, when compared with Arg/Arg genotype. The presence of any XRCC1 Gln showed association with 1.93-fold increased risk. The variant Gln allele was associated with increased risk of breast cancer (95% CI 1.1885 to 2.6805, p = 0.0052). For XRCC3, Thr/Met heterozygous and combined Thr/Met + Met/Met genotypes were associated with 1.85-fold (95% CI 1.0815 to 3.1834, p = 0.0248) and 1.89-fold (95% CI 1.1199 to 3.1908, p = 0.0171) higher risk, respectively, compared to Thr/Thr genotypes. The variant Met allele showed significant association with increased breast cancer susceptibility. Among cases genotype frequencies were significantly different in patients with age 55 or above, and with menopause and diabetes.

CONCLUSION

XRCC1 (Arg399Gln) and XRCC3 (Thr241Met) polymorphisms may be associated with increased breast cancer risk in Bangladeshi females.

XRCC1 rs1799782 (C194T) polymorphism correlated with tumor metastasis and molecular subtypes in breast cancer

BACKGROUND

Breast cancer, a malignant tumor with its highest incidence in women, affects physical and mental health, and can even be life-threatening. In recent years, its incidence has continued to grow, accompanied by a trend of younger onset. XRCC1 is well known as a DNA-repair gene, and its abnormal expression is related to the occurrence of various malignant tumors.

METHODS

In this study, we detected XRCC1 expression and investigated its association with the XRCC1 rs1799782 polymorphism. XRCC1 was overexpressed to investigate its effect on in breast cancer cells. CCK8 and clone formation efficiency assay were used to detect cell proliferation. Transwell assay was performed to confirm cell migration and invasion. Flow cytometry was used to detect cell apoptosis.

RESULTS

In 118 breast cancer samples, CC genotype frequency was 49.15% (58 of 118), CT genotype frequency was 42.37% (50 of 118), and TT genotype frequency was 8.48% (ten of 118). Lymphatic metastasis was associated with a higher frequency of XRCC1 rs1799782 polymorphism (P<0.05), and breast cancer patients with positive PR, HER2, and negative ER had high XRCC1 rs1799782 frequency (P<0.05). Meanwhile, XRCC1 had low expression in breast cancer (74.6%, 88 of 118) and high expression in ER-negative, PR-negative, HER2-positive and Ki67-low-expression patients. XRCC1 rs1799782 may play an important role in the development and metastasis of breast cancer. These results differ from previous studies that did not suggest that rs1799782 is effective in breast cancer. We also investigated the role of XRCC1 in breast cancer progression.

CONCLUSION

We have proved that XRCC1 can inhibit proliferation and invasion and promote apoptosis of breast cancer cells. XRCC1 expression was regulated by the JNK pathway. We found that the JNK inhibitor SP600125 significantly inhibited the growth of breast cancer cells, and consider it a potential drug for breast cancer.

The association of XRCC1 polymorphism with osteosarcoma risk, clinicopathologic features, and prognosis in a Chinese Han population

Introduction

The association of single-nucleotide polymorphisms at X-ray repair cross-complementing group-1 (XRCC1) with osteosarcoma (OS) development has not been fully clear to date. The aim of the present study is to evaluate the association of XRCC1 polymorphisms with risk, clinicopathologic features, and prognosis in Chinese OS patients.

Methods

A total of 146 patients with primary OS and 248 age- and gender-matched controls were included in the present study. The frequencies of four XRCC1 polymorphisms (rs25487, rs1799782, rs25489, and rs3213245) were determined between OS patients and controls. The association of XRCC1 polymorphism with clinicopathologic characteristics, prognosis, and XRCC1 expression was further evaluated.

Results

Compared with TT genotype, individuals carrying the minor C allele (TC+ CC) of rs3213245 had significantly increased risk of OS development (OR =1.83, 95% CI 1.14–3.00). OS patients carrying TC genotype and C allele at rs3213245 were more likely to be with larger tumor size and metastasis. Survival analysis demonstrated that OS patients carrying C allele (TC + CC) at rs3213245 had shorter survival time than those with TT genotype. The T to C substitution at rs3213245 could decrease XRCC1 gene transcriptional activity in vitro. XRCC1 mRNA and protein expression levels were lower in OS patients carrying TC or CC genotype at rs3213245. Besides, no significant association of rs25487, rs1799782, and rs25489 with OS was observed.

Conclusion

In conclusion, these findings revealed that XRCC1 rs3213245 polymorphism was associated with increased risk of OS, which could affect XRCC1 expression in vitro and in vivo.

Polymorphisms in genes implicated in base excision repair (BER) pathway are associated with susceptibility to Paget's disease of bone

Paget's disease of bone (PDB) is a chronic bone metabolic disorder. Currently, PDB is the second most frequent bone disorder. PDB is a focal disorder affecting the skeleton segmentally but the cause of which is unknown. It has been hypothesised that somatic mutations could be responsible for the mosaicism described in PDB patients. Therefore, our hypothesis is that defective response to DNA damage may lead to somatic mutations favouring an increased risk of PDB. So that we have analysed polymorphisms in DNA repair genes involved in the BER, NER and DSBR pathways in order to evaluate the role of these variants in modulating PDB risk. We found statistically significant differences in genotypic and allelic distribution for polymorphisms in genes implicated in the BER pathway. Our results showed that carrying the allele T of XRCC1 rs1799782 polymorphism and the allele G of APEX rs1130409 polymorphism increased the risk of developing PDB. These polymorphisms could cause a lower DNA repair efficiency and this might lead to local somatic mutations favouring bone metabolic alterations characteristic of PDB. This is the first report showing an association between polymorphism in genes implicated in the BER pathway with PDB.

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.

DNA Repair Mechanism Gene, XRCC1A ( Arg194Trp) but not XRCC3 ( Thr241Met) Polymorphism Increased the Risk of Breast Cancer in Premenopausal Females: A Case-Control Study in Northeastern Region of India

X-ray repair cross complementary group gene is one of the most studied candidate gene involved in different types of cancers. Studies have shown that X-ray repair cross complementary genes are significantly associated with increased risk of breast cancer in females. Moreover, studies have revealed that X-ray repair cross complementary gene polymorphism significantly varies between and within different ethnic groups globally. The present case–control study was aimed to investigate the association of X-ray repair cross complementary 1A (Arg194Trp) and X-ray repair cross complementary 3 (Thr241Met) polymorphism with the risk of breast cancer in females from northeastern region of India. The present case–control study includes histopathologically confirmed and newly diagnosed 464 cases with breast cancer and 534 apparently healthy neighborhood community controls. Information on sociodemographic factors and putative risk factors were collected from each study participant by conducting face-to-face interviews. Genotyping of X-ray repair cross complementary 1A (Arg194Trp) and X-ray repair cross complementary 3 (Thr241Met) was carried out by polymerase chain reaction-restriction fragment length polymorphism. For statistical analysis, both univariate and multivariate logistic regression analyses were performed. We also performed stratified analysis to find out the association of X-ray repair cross complementary genes with the risk of breast cancer stratified based on menstrual status. This study revealed that tryptophan allele (R/W-W/W genotype) in X-ray repair cross complementary 1A (Arg194Trp) gene significantly increased the risk of breast cancer (adjusted odds ratio = 1.44, 95% confidence interval = 1.06-1.97, P < .05 for R/W-W/W genotype). Moreover, it was found that tryptophan allele (W/W genotype) at codon 194 of X-ray repair cross complementary 1A (Arg194Trp) gene significantly increased the risk of breast cancer in premenopausal females (crude odds ratio = 1.66, 95% confidence interval = 1.11-2.46, P < .05 for R/W-W/W genotype). The present study did not reveal any significant association of X-ray repair cross complementary 3 (Thr241Met) polymorphism with the risk of breast cancer. The present study has explored that X-ray repair cross complementary 1A (Arg194Trp) gene polymorphism is significantly associated with the increased risk of breast cancer in premenopausal females from northeastern region of India which may be beneficial for prognostic purposes.

XRCC1 Arg399Gln Genetic Polymorphism in a Turkish Population

Humans are routinely exposed to mutagenic and carcinogenic chemicals. These chemicals can form DNA adducts in vivo and thus lead to DNA damage. The integrity of most of the so-damaged DNAs is typically restored as a consequence of the action of certain DNA-repairing enzymes. In several DNA repair genes, polymorphisms may result in reduced repair capacity, which has been implicated as a risk factor for various types of cancer. XRCC1 is a base-excision repair protein that plays a central role in the repair of DNA base damage and strand breaks. Amongst the known genetic polymorphisms of the DNA-repair genes, X-ray repair cross-complementing groups 1 and 3 ( XRCC1 and XRCC3) have been studied most commonly. Inconsistent results have been reported regarding the associations between the Arg399Gln (exon 10) polymorphism of XRCC1 and either functional significance or the risk of tobacco-associated cancers. The Gln allele of this polymorphism was associated with higher levels of DNA adducts. Therefore we genotyped one of the polymorphism of XRCC1, Gln allele. The frequency of the polymorphic alleles varies among populations, suggesting an ethnic distribution of genotypes. There has been no information on interindividual variability of Arg399Gln genotype in the Turkish population. Due to the association between the Arg399Gln polymorphism of XRCC1 and the risk of tobacco-associated cancers, we preferred to evaluate the allelic frequencies of Arg399Gln genotype than the other polymorphisms in XRCC1 gene in healthy Turkish population by polymerase chain reaction–restriction fragment polymorphism (PCR-RFLP) analysis to enable to show interindividual differences and compare to other populations.

Association of XRCC1 Trp194 allele with risk of breast cancer, and Ki67 protein status in breast tumor tissues

OBJECTIVES

To evaluate the role of this polymorphism as a risk factor for breast cancer in Kurdish patients and to investigate the possible association between Arg194Trp x-ray repair cross-complementing group 1 (XRCC1) gene polymorphisms with clinical and histopathological outcomes of patients with breast cancer.

METHODS

A total of 100 breast cancer patients and 200 cancer-free controls in Kurdish population of Kurdistan state admitted to Tohid Hospital, Sanandaj, Kurdistan, Iran between January 2012 and May 2015 were enrolled in this cross-sectional study. Tissue expression of estrogen receptor (ER), progesteron receptor (PR), human epidermal growth factor receptor 2 (Her2/neu), and Ki67 were evaluated by immunohistochemistry (IHC). The Arg194Trp genotypes were determined by polymerase chain reaction- restriction fragment length polymorphism method. 

RESULTS

Our data showed that the risk for breast cancer increased significantly among the Trp variant of XRCC1. Statistically significant association was found between codon 194 polymorphisms and tissue expression of Ki67.

CONCLUSION

The Trp allele of codon 194 XRCC1 is a potential risk factor for breast cancer in Kurdish ethnicity. Furthermore, effect of this polymorphism on clinical and histological features of breast cancer was significant.

DNA repair variants and breast cancer risk

A functional DNA repair system has been identified as important in the prevention of tumour development. Previous studies have hypothesized that common polymorphisms in DNA repair genes could play a role in breast cancer risk and also identified the potential for interactions between these polymorphisms and established breast cancer risk factors such as physical activity. Associations with breast cancer risk for 99 single nucleotide polymorphisms (SNPs) from genes in ten DNA repair pathways were examined in a case-control study including both Europeans (644 cases, 809 controls) and East Asians (299 cases, 160 controls). Odds ratios in both additive and dominant genetic models were calculated separately for participants of European and East Asian ancestry using multivariate logistic regression. The impact of multiple comparisons was assessed by correcting for the false discovery rate within each DNA repair pathway. Interactions between several breast cancer risk factors and DNA repair SNPs were also evaluated. One SNP (rs3213282) in the gene XRCC1 was associated with an increased risk of breast cancer in the dominant model of inheritance following adjustment for the false discovery rate (P < 0.05), although no associations were observed for other DNA repair SNPs. Interactions of six SNPs in multiple DNA repair pathways with physical activity were evident prior to correction for FDR, following which there was support for only one of the interaction terms (P < 0.05). No consistent associations between variants in DNA repair genes and breast cancer risk or their modification by breast cancer risk factors were observed.

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.

Single nucleotide polymorphisms (SNPs) of hOGG1 and XRCC1 DNA repair genes and the risk of ovarian cancer in Polish women

The aim of this study was to determine single nucleotide polymorphisms in hOGG1 (Ser326Cys (rs13181)) and XRCC1 (Arg194Trp (rs1799782)) genes, respectively, and to identify the correlation between them and the overall risk, grading and staging of ovarian cancer in Polish women. Our study comprised 720 patients diagnosed with ovarian cancer and 720 healthy controls. The genotype analysis of hOGG1 and XRCC1 polymorphisms was performed using polymerase chain reaction (PCR)-based restriction fragment length polymorphism (PCR-RFLP). Odds ratios (OR) and 95 % confidence intervals (CI) for each genotype and allele were calculated. Results revealed an association between hOGG1 Ser326Cys polymorphism and the incidence of ovarian cancer. Variant Cys allele of hOGG1 increased the overall cancer risk (OR 2.89; 95 % CI 2.47-3.38; p < .0001). Moreover, ovarian cancer grading remained in a relationship with both analysed polymorphisms; G1 tumours presented increased frequencies of hOGG1 Cys/Cys homozygotes (OR 18.33; 95 % CI 9.38-35.81; p < .0001) and XRCC1 Trp/Trp homozygotes (OR 20.50; 95 % CI 10.17-41.32; p < .0001). Furthermore, G1 ovarian cancers displayed an overrepresentation of Cys and Trp allele. In conclusion, hOGG1 Ser326Cys and XRCC1 Arg194Trp polymorphisms may be regarded as risk factors of ovarian 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%).

Deoxyribonucleic acid repair gene X-ray repair cross-complementing group 1 polymorphisms and non-carcinogenic disease risk in different populations: A meta-analysis

PURPOSE

This study aims to assess a meta-analysis of the association of X-ray repair cross-complementing group 1 (XRCC1) polymorphisms with the risk of various non-carcinogenic diseases in different population.

MATERIALS AND METHODS

This meta-analysis was performed by critically reviewing reveals 38 studies involving 10043 cases and 11037 controls. Among all the eligible studies, 14 focused on Arg194Trp polymorphism, 33 described the Arg399Gln and three articles investigated on Arg280His. Populations were divided into three different ethnic subgroups include Caucasians, Asians and other (Turkish and Iranian).

RESULTS

Pooled results showed no correlation between Arg194Trp and non-carcinogenic disease. There was only weak relation in the recessive (odds ratio [OR] =1.11, 95% confidence interval [CI]: 0.86-1.44) model in Asian population and dominant (OR = 1.04, 95% CI: 0.66-1.63) model of other populations. In Arg399Gln polymorphism, there was no relation with diseases of interest generally. In the pooled analysis, there were weak relation in the dominant (OR = 1.08, 95% CI: 0.86-1.35) model of Asian population and quite well-correlation with recessive (OR = 1.49, 95% CI: 1.19-1.88), dominant (OR = 1.23, 95% CI: 0.94-1.62), and additive (OR = 1.23, 95% CI: 0.94-1.62) models of other subgroup. For Arg280His, there was a weak relation only in the dominant model (OR = 1.06, 95% CI: 0.74-1.51).

CONCLUSION

The present meta-analysis correspondingly shows that Arg399Gln variant to be associated with increased non-carcinogenic diseases risk through dominant and recessive modes among Iranian and Turkish population. It also suggests a trend of dominant and recessive effect of Arg280His variant in all population and its possible protective effect on non-carcinogenic diseases.

XRCC1 Arg399Gln polymorphism confers risk of breast cancer in American population: a meta-analysis of 10846 cases and 11723 controls

Background

In the X-ray repair cross-complementing group 1 (XRCC1) gene, a polymorphism, Arg399Gln (rs25487), has been shown to change neoconservative amino acid and thus result in alternation of DNA repair capacity. Numerous studies have investigated the association between Arg399Gln and breast cancer risk in the American population, but yielding inconsistent results. This study aimed to clarify the role of this polymorphism in susceptibility to breast cancer.

Methods

Literatures were searched in multiple databases including PubMed, Springer Link, Ovid, EBSCO and ScienceDirect databases up to April 2013. A comprehensive meta-analysis was conducted to estimate the overall odds ratio (OR), by integrating data from 18 case control studies of 10846 cases and 11723 controls in the American population.

Results

Overall, significant association was observed between the Arg399Gln polymorphism and breast cancer risk under the random-effects model (OR for dominant model = 1.12, 95% CI: 1.02–1.24, P_{heterogeneity} = 0.003; OR for additive model = 1.07, 95% CI: 1.01–1.14, P_{heterogeneity} = 0.017). Further sensitivity analysis supported the robust stability of this current result by showing similar ORs before and after removal of a single study.

Conclusions

This meta-analysis suggests that the XRCC1 Arg399Gln polymorphism may significantly contribute to susceptibility of breast cancer in the American population.

Single nucleotide polymorphisms (SNPs) of ERCC2, hOGG1, and XRCC1 DNA repair genes and the risk of triple-negative breast cancer in Polish women

Triple-negative breast cancer (TNBC) refers to about 15–20 % of all breast cancer cases. It is characterized by worse clinical outcome, poor prognosis, and absence of prognostic indicators. Several polymorphisms in the nucleotide excision repair (NER) and base excision repair (BER) gene have been extensively studied in association with various human cancers. The aim of this study was to evaluate the role of the hOGG1-Ser326Cys (rs13181), XRCC1-Arg194Trp (rs1799782), and ERCC2-Lys751Gln (rs13181) gene polymorphisms with clinical parameters and the risk for development of triple-negative breast cancer. Our research included 70 patients with TNBC and 70 healthy controls. Gene polymorphisms were genotyped by the PCR-RFLP (restriction fragment length polymorphism) method. The genotype distributions were contrasted by the chi-square test, and the significance of the polymorphism was assessed by multiple logistic regression producing odds ratios (ORs) and 95 % confidence intervals (CIs). In the present work, a relationship was identified between ERCC2-Lys751Gln polymorphism and the incidence of triple-negative breast cancer. An association was observed between triple-negative breast carcinoma occurrence and the presence of Gln/Gln genotype (OR = 5.71 (2.12–5.43), p = 0.0007). A tendency for an increased risk of TNBC was detected with the occurrence of 751Gln allele of ERCC2 polymorphism. No significant associations between Ser326Cys and Arg194Trp genotype and TNBC were observed. We suggest that the Lys751Gln polymorphism of the ERCC2 gene may be risk factors for triple-negative breast cancer development in Polish women.

miRNA dysregulation in breast cancer

miRNAs have emerged, in the last decade, as key players in the carcinogenic process, with many candidates identified as playing important roles in many aspects of tumor development, growth, metastasis, and drug resistance. More recently, polymorphisms in miRNAs themselves or in their binding sites in target genes have been identified to incur increased risk of breast cancer in certain populations. In addition, epigenetic regulation and differential expression of processing enzymes has been shown to contribute to the aberrant expression of miRNAs in breast cancer. This review focuses on the area of miRNA dysregulation in breast cancer through both genetic and epigenetic mechanisms, and the impact of this dysregulation on breast cancer risk and resistance to therapies.

Meta-analysis of genetic polymorphisms and ophthalmologic disease risk in Asian populations: a case of DNA repair XRCC1 gene

This study aimed to assess a meta-analysis of the association of XRCC1 polymorphisms with the risk of various ophthalmologic diseases in Asian population. This meta-analysis was performed by critically reviewing reveals 38 studies involving 1373 cases and 1745 controls. Among all the eligible studies, one focused on Arg194Trp polymorphism, nine described the Arg399Gln and no article investigated on Arg280His. There was a large between-study heterogeneity in ORs of individual studies of the dominant model (chi2 = 74.18, I2 = 58.9%, p = 0.013) and the additive (chi2 = 56.18, I2 = 41.4%, p = 0.091) models, but a moderate heterogeneity in the recessive model (chi2 = 72.27, I2 = 78.8%, p = 0.000) was observed. So, we pooled the results using the random-effect analysis and found that Arg399Gln has a weak relation with ophthalmologic disease in the recessive (OR = 0.96, 95% CI: 0.64-1.44), the dominant (OR = 1.05, 95% CI: 0.82-1.33) and the additive (OR = 1.15, 95% CI: 0.77-1.70) and models. The present meta-analysis correspondingly shows that comprising diverse population is very important since susceptibility loci might vary indifferent ethnic groups. To ratify our findings, widespread studies with enlarged sample size and various populations are essential to explain the role of all polymorphism of XRCC1 genes in the pathogenesis of ophthalmologic diseases. Finally, our meta-analysis showed Arg399Gln variant was not associated with increased ophthalmologic diseases risk via dominant and recessive modes among Asian population.

Correlation between X-ray cross-complementing group 1 polymorphisms and the onset risk of glioma: A meta-analysis

OBJECTIVE:

To evaluate the association of X-ray cross-complementing group 1 (XRCC1) Arg399Gln, Arg194Trp and Arg280His polymorphisms with the risk of glioma.

DATA SOURCES:

A systematic literature search of papers published from January 2000 to August 2012 in PubMed, Embase, China National Knowledge Infrastructure database, and Wanfang database was performed. The key words used were “glioma”, “polymorphism”, and “XRCC1 or X-ray repair cross-complementing group 1”. References cited in the retrieved articles were screened manually to identify additional eligible studies.

STUDY SELECTION:

Studies were identified according to the following inclusion criteria: case-control design was based on unrelated individuals; and genotype frequency was available to estimate an odds ratio (OR) and 95% confidence interval (CI). Meta-analysis was performed for the selected studies after strict screening. Dominant and recessive genetic models were used and the relationship between homozygous mutant genotype frequencies and mutant gene frequency and glioma incidence was investigated. We chose the fixed or random effect model according to the heterogeneity to calculate OR and 95%CI, and sensitivity analyses were conducted. Publication bias was examined using the inverted funnel plot and the Egger's test using Stata 12.0 software.

MAIN OUTCOME MEASURES:

Association of XRCC1 Arg399Gln, Arg194Trp, and Arg280His polymorphisms with the risk of glioma, and subgroup analyses were performed according to different ethnicities of the subjects.

RESULTS:

Twelve articles were included in the meta-analysis. Eleven of the articles were concerned with the Arg399Gln polymorphism and glioma onset risk. Significantly increased glioma risks were found only in the dominant model (Gln/Gln + Gln/Arg versus Arg/Arg: OR = 1.26, 95%CI = 1.03–1.54, P = 0.02). In the subgroup analysis by ethnicity, significantly increased risk was found in Asian subjects in the recessive (OR = 1.46, 95%CI = 1.04–2.45, P = 0.03) and dominant models (OR = 1.40, 95%CI = 1.10–1.78, P = 0.007), and homozygote contrast (OR = 1.69, 95%CI = 1.17–2.45, P = 0.005), but not in Caucasian subjects. For association of the Arg194Trp (eight studies) and Arg280His (four studies) polymorphisms with glioma risk, the meta-analysis did not reveal a significant effect in the allele contrast, the recessive genetic model, the dominant genetic model, or homozygote contrast.

CONCLUSION:

The XRCC1 Arg399Gln polymorphism may be a biomarker of glioma susceptibility, especially in Asian populations. The Arg194Trp and Arg280His polymorphisms were not associated with overall glioma risk.

Polymorphisms of DNA repair genes in endometrial cancer

Endometrial cancer belongs to the commonest malignancy in females. Its development may be associated with the high exposure of endometrium to exo- and endogenous estrogens. Estrogens produce DNA bulky adducts and oxidative base damages which are removed in nucleotide excision repair (NER) and base excision repair (BER) pathways. The reaction of endometrial cells to DNA damage may be crucial for their susceptibility to cancer transformation. This reaction is executed mainly by DNA repair, which can be modulated by the variability in the genes encoding DNA repair proteins. In this report we genotyped 4 polymorphisms of 3 DNA repair genes in 94 endometrial cancer patients and 114 age-matched cancer-free women using RFLP-PCR. The following polymorphisms were studied: p.Arg194Trp, p.Arg399Gln of the XRCC1 gene, p.Ser326Cys of the hOGG1 gene and p.Lys751Gln of the ERCC2 gene. We found an association between the ERCC2 751Gln variant and endometrial cancer occurrence (OR 3.95; 95 % CI 1.88–8.31). Gene-gene interaction between the ERCC2 751Gln and XRCC1 194Trp variants also increased the risk of endometrial cancer (OR 4.41; 95 % CI 2.01–9.67). The risk in the carriers of the ERCC2 751Gln variant was increased by a positive cancer history in first degree relatives (OR 4.97; 95 % CI 1.98–12.48). The risk of endometrial cancer was not alter by polymorphism p.Ser326Cys of the hOGG1 gene. The 751 Lys/Gln polymorphism of the ERCC2 gene may be linked with endometrial cancer occurrence and its effect can be potentiated by variants of the XRCC1 gene or first degree relatives positive cancer history.

XRCC1 polymorphisms and risk of papillary thyroid carcinoma in a Korean sample

Polymorphisms of DNA repair genes, X-ray repair cross-complementing group 1 (XRCC1) might contribute to individual susceptibility to different types of cancers. We analyzed the relationship between XRCC1 polymorphisms and the risk of papillary thyroid carcinoma in a Korean sample. A hospital-based case-control study was performed in 111 papillary thyroid carcinoma patients and 100 normal control subjects. XRCC1 Arg194Trp and Arg399Gln single nucleotide polymorphisms (SNPs) were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The XRCC1 Arg194Trp Arg/Trp genotype was significantly associated with a decreased risk of papillary thyroid carcinoma compared to that of Arg/Arg genotype (odds ratio [95% confidence intervals]; 0.550 [0.308-0.983]). There was no significant association between XRCC1 Arg399Gln genotypes and risk of papillary thyroid carcinoma. Based on these results, the XRCC1 Arg194Trp Arg/Trp genotype could be used as a useful molecular biomarker to predict genetic susceptibility for papillary thyroid carcinoma in Koreans.

Association of XRCC1 variants with acute skin reaction after radiotherapy in breast cancer patients

After irradiation results in cytotoxic effects by DNA damage, base excision repair (BER) pathway is involved in the repair of single-strand breaks and nonhomologous end joining and homologous repair of double-strand breaks caused by radiotherapy. Alterations in the function of BER DNA repair genes may affect DNA repair proficiency and influence the response of patients with cancer to radiotherapy. The association of single nucleotide polymorphisms of BER DNA repair X-ray repair cross-complementing group 1 protein (XRCC1) and risk of radiotherapy-induced ≥grade 2 acute skin reaction in patients with breast cancer was examined. It was found that the risk of ≥grade 2 acute skin toxicity after radiotherapy could be increased by 2.86-fold in patients carrying the XRCC1 -77TC and CC genotypes (p = 0.016). However, the other three coding XRCC1 variants did not influence the risk of ≥grade 2 acute skin toxicity for patients with breast cancer after radiotherapy. Our results suggested that the XRCC1 polymorphism is associated with increased risk of radiation-induced acute skin reaction in a Chinese population.

Polymorphism in the DNA repair enzyme XRCC1: utility of current database and implications for human health risk assessment

Genetic polymorphisms are increasingly recognized as sources of variability not only in toxicokinetic but also in toxicodynamic response to environmental agents. XRCC1 is involved in base excision repair (BER) of DNA; it has variant genotypes that are associated with modified repair function. This analysis focuses on four polymorphisms: three in the coding region that affect protein structure and one in an upstream regulatory sequence that affects gene expression. The Arg399Gln variant is the most widely studied with evidence supporting a quantitative effect of genotype on phenotype. The homozygous variant (Gln/Gln) can have 3-4-fold diminished capacity to remove DNA adducts and oxidized DNA damage. This variant is relatively common in Caucasians and Asians where approximately 10% are homozygous variant. In contrast, the Arg194Trp variant appears to protect against genotoxic effects although the degree to which DNA repair is enhanced by this polymorphism is uncertain. The homozygous variant is rare in Caucasians and African Americans but it is present at 7% in Asians. A third coding region polymorphism at codon 280 appears to decrease repair function but additional quantitative information is needed and the homozygous variant is rare across populations studied. A polymorphism in an upstream promoter binding sequence (-77T>C) appears to lower XRCC1 levels by decreasing gene expression. Based upon genotype effect on phenotype and allele frequency, the current analysis finds that the codon 399 and upstream (-77) polymorphisms have the greatest potential to affect the toxicodynamic response to DNA damaging agents. However, the implications for risk assessment are limited by the likelihood that polymorphisms in multiple BER genes interact to modulate DNA repair.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

IMPACT

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

Single-nucleotide polymorphisms inside microRNA target sites influence tumor susceptibility

Single-nucleotide polymorphisms (SNP) associated with polygenetic disorders, such as breast cancer (BC), can create, destroy, or modify microRNA (miRNA) binding sites; however, the extent to which SNPs interfere with miRNA gene regulation and affect cancer susceptibility remains largely unknown. We hypothesize that disruption of miRNA target binding by SNPs is a widespread mechanism relevant to cancer susceptibility. To test this, we analyzed SNPs known to be associated with BC risk, in silico and in vitro, for their ability to modify miRNA binding sites and miRNA gene regulation and referred to these as target SNPs. We identified rs1982073-TGFB1 and rs1799782-XRCC1 as target SNPs, whose alleles could modulate gene expression by differential interaction with miR-187 and miR-138, respectively. Genome-wide bioinformatics analysis predicted approximately 64% of transcribed SNPs as target SNPs that can modify (increase/decrease) the binding energy of putative miRNA::mRNA duplexes by >90%. To assess whether target SNPs are implicated in BC susceptibility, we conducted a case-control population study and observed that germline occurrence of rs799917-BRCA1 and rs334348-TGFR1 significantly varies among populations with different risks of developing BC. Luciferase activity of target SNPs, allelic variants, and protein levels in cancer cell lines with different genotypes showed differential regulation of target genes following overexpression of the two interacting miRNAs (miR-638 and miR-628-5p). Therefore, we propose that transcribed target SNPs alter miRNA gene regulation and, consequently, protein expression, contributing to the likelihood of cancer susceptibility, by a novel mechanism of subtle gene regulation.

Contribution of XPD (Lys751Gln) and XRCC1 (Arg399Gln) polymorphisms in familial and sporadic breast cancer predisposition and survival: an Indian report

The etiology of a significant proportion of familial breast cancers is still poorly understood, with known high penetrance gene mutations accounting for only a small proportion of the cases. The increased risk of breast cancer for the majority of women with a family history likely reflects shared minor low penetrant genetic factors. In the present case-control study undertaken to examine the influence of DNA damage repair gene polymorphisms in familial and sporadic breast cancer susceptibility, 219 Sporadic and 140 familial breast cancer patients and 367 controls were genotyped using PCRRFLP. Odds Ratios (ORs) and 95% Confidence Intervals (95%CIs) were calculated by unconditional logistic regression adjusted to age. Variant genotypes XRCC1 Arg/Gln or Gln/Gln and XPD Lys/Gln or Gln/Gln increased both familial and sporadic breast cancer susceptibility. However, when the intra group risk was compared, the risk due to the XPD polymorphic genotypes Lys/Gln or Gln/Gln was significantly lower among familial breast cancer patients compared to sporadic breast cancer patients [OR = 0.61; 95%CI = 0.39-0.94; p value = 0.024) whereas the risk implied by XRCC1 variant genotype was not significantly different between the familial and nonfamilial groups of breast cancer patients [OR = 0.97; 95%CI = 0.63-1.49; p value = 0.882]. Both these variant genotypes were not associated with the disease characteristics or survival of either familial or sporadic breast cancer patients. This study represents an addition to previous published work on GSTs from the same study population and substantiates the hypothesis that the impact of the low penetrance gene polymorphisms differ by family history of the disease.

Basic properties and molecular mechanisms of exogenous chemical carcinogens

Exogenous chemical carcinogenesis is an extremely complex multifactorial process during which gene-environment interactions involving chronic exposure to exogenous chemical carcinogens (ECCs) and polymorphisms of cancer susceptibility genes add further complexity. We describe the properties and molecular mechanisms of ECCs that contribute to induce and generate cancer. A basic and specific property of many lipophilic organic ECCs including polycyclic aromatic hydrocarbons and polyhalogenated aromatic hydrocarbons is their ability to bioaccumulate in the adipose tissue from where they may be released in the blood circulation and target peripheral tissues for carcinogenesis. Many organic ECCs are procarcinogens and consequently need to be activated by the cytochrome P450 (CYP) system and/or other enzymes before they can adduct DNA and proteins. Because they contribute not only to the cocarcinogenic and promoting effects of many aromatic pollutants but also to their mutagenic effects, the aryl hydrocarbon receptor-activating and the inducible CYP systems are central to exogenous chemical carcinogenesis. Another basic property of ECCs is their ability to induce stable and bulky DNA adducts that cannot be simply repaired by the different repair systems. In addition, following ECC exposure, mutagenesis may also be caused indirectly by free-radical production and by epigenetic alterations. As a result of complex molecular interplays, direct and/or indirect mutagenesis may especially account for the carcinogenic effects of many exogenous metals and metalloids. Because of these molecular properties and action mechanisms, we conclude that ECCs could be major contributors to human cancer, with obviously great public health consequences.

An empirical comparison of meta-analyses of published gene-disease associations versus consortium analyses

PURPOSE

Consortia of investigators currently compile sufficiently large sample sizes to investigate the effects of low-risk susceptibility genetic variants. It is not clear how the results obtained by consortia compare with those derived from meta-analyses of published studies.

METHODS

We performed meta-analyses of published data for 16 genetic polymorphisms investigated by the Breast Cancer Association Consortium, and compared sample sizes, heterogeneity, and effect sizes. PubMed, Web of Science, and Human Genome Epidemiology Network databases were searched for breast cancer case-control association studies.

RESULTS

We found that meta-analyses of published data and consortium analyses were based on substantially different data. Published data by non-consortium teams amounted on average to 26.9% of all available data (range 3.0 -50.0%). Both approaches showed statistically significant decreased breast cancer risks for CASP8 D302H. The meta-analyses of published data demonstrated statistically significant results for five other genes and the consortium analyses for two other genes, but the strength of this evidence, evaluated on the basis of the Venice criteria, was not strong.

CONCLUSIONS

Because both approaches identified the same gene out of 16 candidates, the methods can be complimentary. The expense and complexity of consortium-based studies should be considered vis-à-vis the potential methodological limitations of synthesis of published studies.

XRCC1 Arg399Gln, Arg194Trp and Arg280His polymorphisms in breast cancer risk: a meta-analysis

X-ray repair cross-complementing group 1 (XRCC1) plays an important role in base excision and single-strand break repair, as a scaffold protein that brings together proteins of the DNA repair complex, and appears to be a candidate for cancer risk. However, studies on the association between polymorphisms in this protein and cancer have yielded conflicting results. We performed a meta-analysis to investigate the association between the breast cancer and the XRCC1 polymorphisms Arg194Trp (9411 cases and 9783 controls), Arg399Gln (22 481 cases and 23 905 controls) and Arg280His (6062 cases and 5864 controls) in different inheritance models. Our analysis suggested that Arg399Gln was associated with a trend of increased breast cancer risk when using both dominant [odds ratio (OR) = 1.06, 95% confidence interval (CI): 1.00-1.13] and recessive models (OR = 1.12, 95% CI: 1.02-1.23) to analyse the data. In ethnic subgroups and using recessive model analysis: Arg399Gln increased breast cancer risk in Asians (OR = 1.26, 95% CI: 0.96-1.64) and Africans (OR = 1.80, 95% CI: 0.97-3.32), and also while only slightly increasing the breast cancer risk in Caucasians (OR = 1.08, 95% CI: 0.95-1.22). However, Arg194Trp (recessive model, OR = 0.95, 95% CI: 0.75-1.20) and Arg280His (recessive model, OR = 1.28, 95% CI: 0.64-2.55) did not appear to be risk factors for breast cancer. Larger scale primary studies are required to further evaluate the interaction of XRCC1 polymorphisms and breast cancer risk in specific populations.

XRCC1 gene polymorphisms and breast cancer risk in different populations: a meta-analysis

We performed a meta-analysis to investigate the role of XRCC1 polymorphisms Arg194Trp, Arg280His and Arg399Gln in breast cancer. The results were pooled in a manner that appropriately reflects a biological model of gene effect using a random effects logistic regression model without multiple comparisons. Forty studies from 31 reports were included with 10 465 cases and 10 888 controls at Arg194Trp, 6156 cases and 5806 controls at Arg280His, and 21 467 cases and 22 766 controls at Arg399Gln. Our analysis found a tendency towards a recessive effect of Arg280His variant in Asian population only (His/His vs. Arg/Arg+Arg/His: OR=2.27, 95% CI=0.82, 6.31). An increased breast cancer risk with a recessive effect was also suggested for Arg399Gln variant in Asian population (Gln/Gln vs. Arg/Arg+Arg/Gln: OR=1.59, 95% CI=1.22, 2.09) only. These findings suggest that polymorphisms Arg280His and Arg399Gln may modify breast cancer risk differently in Caucasian and Asian populations.

Polymorphism of XRCC1 (at codon 399) and susceptibility to breast cancer, a meta-analysis of the literatures

The X-ray repair cross-complementation group 1 (XRCC1) protein plays an important role in base excision repair. Several polymorphisms in the XRCC1 gene have been described, including Arg399Gln. Previous studies investigating the association between genetic polymorphism of Arg399Gln XRCC1 and risk of breast cancer have provided inconsistent results. A meta-analysis was conducted to investigate the association between common genetic variant in the XRCC1 gene (exon 10, Arg399Gln) with breast cancer risk. We identified 36 eligible studies, in relation to the Arg399Gln polymorphism of XRCC1 and risk of breast cancer. These studies comprised of 43,716 subjects (20,837 patients and 22,879 controls). We first estimated the risk of the genotypes Arg/Gln and Gln/Gln compared with the wild-type Arg/Arg homozygote, and then evaluated the risk of Gln/Gln versus (Arg/Gln+Arg/Arg) and (Gln/Gln+Arg/Gln) versus Arg/Arg, which assumed recessive and dominant effects, respectively, of the variant 399Gln allele. There was significant heterogeneity between studies. The overall ORs showed that the breast cancer risk were not associated with the XRCC1 genotypes. The heterogeneity between studies decreased dramatically when studies stratified into Asian and Western countries. There was significant association between the polymorphism of XRCC1 and breast cancer risk among studies of Asian countries. In Asian countries the Arg/Gln versus Arg/Arg (OR = 0.98, 95% CI: 0.88-1.10) and Gln/Gln+Arg/Gln versus Arg/Arg (OR = 1.05, 95% CI: 0.95-1.18) were not associated with increased risk of breast cancer. On the other hand, both Gln/Gln versus Arg/Arg (OR = 1.46, 95% CI: 1.19-1.79) and Gln/Gln versus Arg/Gln+Arg/Arg (OR = 1.49, 95% CI: 1.22-1.81) increased the risk. Therefore, it could be concluded that 399Gln allele might act as a recessive allele in its association with breast cancer risk.

XRCC1 polymorphisms and severe toxicity in lung cancer patients treated with cisplatin-based chemotherapy in Chinese population

Cisplatin kills tumor cells through DNA cross linking. Alterations in the function of DNA repair genes may affect DNA repair proficiency and influence cancer patients' response to cisplatin. The predictability of DNA repair XRCC1 (X-ray repair cross-complementing group 1 protein) single nucleotide polymorphisms (SNPs) for cisplatin-based grades 3 and 4 chemotherapy-related toxicity in patients with newly diagnosed advanced lung cancer was evaluated. The genotypes of XRCC1 at the Arg194Trp, and Arg399Gln sites were determined by PCR-based restriction fragment length polymorphism (RFLP) methods. There was no statistically significant association between either the Arg194Trp or the Arg399Gln polymorphisms and hematologic grade 3 or 4 toxicity. However, carrying at least one variant XRCC1 Arg399Gln allele (399Arg/Gln or 399Gln/Gln) was associated with a significantly increased risk of overall grade 3 or 4 toxicity (odds ratio, 2.05; 95% confidence interval, 1.02-4.10; p=0.04); and grade 3 or 4 gastrointestinal toxicity (odds ratio, 2.53; 95% confidence interval, 1.06-6.03; p=0.03). Our results suggested that patients carrying at least one variant XRCC1 Arg399Gln allele have a 2.5-fold increased risk of grade 3 or 4 gastrointestinal toxicity when treated with first-line cisplatin-based chemotherapy.

SnoRNA U50 is a candidate tumor-suppressor gene at 6q14.3 with a mutation associated with clinically significant prostate cancer

Deletion of chromosome 6q14-q22 is common in multiple human cancers including prostate cancer, and chromosome 6 transferred into cancer cells induces senescence and reduces cell growth, tumorigenicity and metastasis, indicating the existence of one or more tumor-suppressor genes in 6q. To identify the 6q tumor-suppressor gene, we first narrowed the common region of deletion to a 2.5 Mb interval at 6q14-15. Of the 11 genes located in this minimal deletion region and expressed in normal prostates, only snoRNA U50 was mutated, demonstrated transcriptional downregulation and inhibited colony formation in prostate cancer cells. The mutation, a homozygous 2 bp (TT) deletion, was found in two of 30 prostate cancer cell lines/xenografts and nine of 89 localized prostate cancers (eleven of 119 or 9% cancers). Two of 89 (2%) patients with prostate cancer also showed the same mutation in their germline DNA, but none of 104 cancer-free control men did. The homozygous deletion abolished U50 function in a colony formation assay. Analysis of 1371 prostate cancer cases and 1371 matched control men from a case-control study nested in a prospective cohort showed that, although a germline heterozygous genotype of the deletion was detected in both patients and controls at similar frequencies, the homozygosity of the deletion was significantly associated with clinically significant prostate cancer (odds ratio 2.9; 95% confidence interval 1.17-7.21). These findings establish snoRNA U50 as a reasonable candidate for the 6q tumor-suppressor gene in prostate cancer and likely in other types of cancers.

Genetic variability in iron-related oxidative stress pathways (Nrf2, NQ01, NOS3, and HO-1), iron intake, and risk of postmenopausal breast cancer

Oxidative stress resulting from excess reactive oxygen species and/or deficiencies in antioxidant capabilities may play a role in breast cancer etiology. In a nested case-control study of postmenopausal women (505 cases and 502 controls) from the American Cancer Society Prevention II Nutrition Cohort, we examined relationships between breast cancer risk and genetic polymorphisms of enzymes involved in the generation and removal of iron-mediated reactive oxygen species. Using unconditional logistic regression, genetic variations in Nrf2 (11108C>T), NQO1 (609C>T), NOS3 (894G>T), and HO-1 [(GT)(n) dinucleotide length polymorphism] were not associated with breast cancer risk in a multivariate model. A significant dose trend (P trend = 0.04), however, was observed for total number of putative "at-risk" alleles (Nrf T, NQO1 T, NOS T, and HO-1 LL and LM genotypes), with those carrying three or more at-risk alleles having an odds ratio (OR) of 1.56 [95% confidence interval (95% CI), 0.97-2.51] compared with those having none. When examined in relation to iron, carriage of three or more high-risk alleles in the highest tertile of iron intake (OR, 2.27; 95% CI, 0.97-5.29; P trend = 0.02; P interaction = 0.30) or among users of supplemental iron (OR, 2.39; 95% CI, 1.09-5.26; P trend = 0.02; P interaction = 0.11) resulted in a greater than 2-fold increased risk compared with women with no high-risk alleles. Increased risk was also observed among supplement users with the HO-1 LL or LM genotypes (OR, 1.56; 95% CI, 1.01-2.41; P interaction = 0.32) compared with S allele carriers and MM genotypes combined. These results indicate that women with genotypes resulting in potentially higher levels of iron-generated oxidative stress may be at increased risk of breast cancer and that this association may be most relevant among women with high iron intake.

Cigarette smoke condensate-induced level of adenomatous polyposis coli blocks long-patch base excision repair in breast epithelial cells

Our previous studies have shown that treatment with cigarette smoke condensate (CSC) transforms normal breast epithelial cell line, MCF-10A. In the present study, the mechanism of CSC-induced transformation of breast epithelial cells was examined. We first determined whether benzo[a]pyrene (B[a]P)- and CSC-induced levels of APC are capable of inhibiting long-patch base excision repair (LP-BER) since our earlier studies had shown that an interaction of APC with DNA polymerase beta (pol-beta) blocks strand-displacement synthesis. With the use of a novel in vivo LP-BER assay, it was demonstrated that increased and decreased APC levels in different breast cancer cell lines were associated with a decrease or increase in LP-BER activity, respectively. The effect of APC on LP-BER in malignant and pre-malignant breast epithelial cell lines was produced by either overexpression or knockdown of APC. Furthermore, it was shown that the decreased LP-BER in B[a]P- or CSC-treated pre-malignant breast epithelial cells is associated with an increased level of APC and decreased cell growth. Our results suggest that the decreased growth allows cells to repair the damaged DNA before mitosis, and failure to repair damaged DNA has the potential to transform pre-malignant breast epithelial cells.

The DNA repair gene XRCC1 and genetic susceptibility of lung cancer in a northeastern Chinese population

To evaluate the effect of DNA repair gene XRCC1 polymorphisms on the risk of lung cancer in a northeastern Chinese population, we studied five cSNPs in the XRCC1 gene, three that lead to non-synonymous changes: Arg194Trp, Arg280 His and Arg399Gln and two that lead to synonymous changes: Pro206Pro and Gln632Gln. A hospital-based case-control study consisted of 247 lung cancer cases and 253 cancer-free controls matched on age, gender and ethnicity. PCR-RFLP was used for genotyping. Carriers of the minor G-allele of Pro206Pro were at significantly increased risk of lung cancer (adjusted OR=1.96, 95% CI=1.26-3.06, P=0.003). Stratified analyses revealed a significantly decreased risk of lung cancer associated with the AG/AA genotype of Arg280His (AG+AA versus GG, OR=0.38, 95% CI=0.19-0.75, P=0.005) among never smokers, although there was no interaction between Arg280His and smoking. In a haplotype analysis, a haplotype defined by Arg194Trp(C)-Pro206Pro(G)-Arg280His(G)-Arg399Gln(G)-Gln632Gln(G) was associated with increased risk of lung cancer (OR=28.60, 95% CI=2.49-331.31, P=4.45x10(-5)). No associations were observed for the other polymorphisms or haplotypes. Our results suggest that the XRCC1 Pro206Pro polymorphism or the haplotype encompassing the minor allele may contribute to genetic susceptibility for lung cancer in this northeastern Chinese population. To our knowledge, this is first report that XRCC1 Pro206Pro influences cancer risk.

Is the association between cigarette smoking and breast cancer modified by genotype? A review of epidemiologic studies and meta-analysis

Epidemiologic studies have examined the association between cigarette smoking and breast cancer risk according to genotype with increasing frequency, commensurate with the growing awareness of the roles genes play in detoxifying or activating chemicals found in cigarette smoke and in preventing or repairing the damage caused by those compounds. To date, approximately 50 epidemiologic studies have examined the association between smoking and breast cancer risk according to variation in genes related to carcinogen metabolism, modulation of oxidative damage, and DNA repair. Some of the findings presented here suggest possible effect modification by genotype. In particular, 14 epidemiologic studies have tended to show positive associations with long-term smoking among NAT2 slow acetylators, especially among postmenopausal women. Summary analyses produced overall meta-relative risk (RR) estimates for smoking of 1.2 [95% confidence interval (95% CI), 1.0-1.5] for rapid acetylators and 1.5 (95% CI, 1.2-1.8) for slow acetylators. After stratification by menopausal status, the meta-RR for postmenopausal slow acetylators was 2.4 (95% CI, 1.7-3.3), whereas similar analyses for the other categories showed no association. In addition, summary analyses produced meta-RRs for smoking of 1.1 (95% CI, 0.8-1.4) when GSTM1 was present and 1.5 (95% CI, 1.1-2.1) when the gene was deleted. Overall, however, interpretation of the available literature is complicated by methodologic limitations, including small sample sizes, varying definitions of smoking, and difficulties involving single nucleotide polymorphism selection, which likely have contributed to the inconsistent findings. These methodologic issues should be addressed in future studies to help clarify the association between smoking and breast cancer.

Lycopene Intake and Prostate Cancer Risk: Effect Modification by Plasma Antioxidants and the XRCC1 Genotype

Lycopene has been associated with reduced prostate cancer risk, although the results of epidemiological studies have varied. We hypothesize that an effect of lycopene may be modified by XRCC1 genotype and other antioxidants. We used a food-frequency questionnaire to assess lycopene intake in a case-control study of prostate cancer in North Carolina. Plasma alpha-tocopherol and beta-carotene levels were measured using high-performance liquid chromatography. XRCC1 genotypes were detected using polymerase chain reaction-restriction fragment length polymorphism. The final dataset included 77 cases and 174 controls with complete questionnaires, genotyping, and plasma analyses. Among men with the Arg/Arg genotype at codon 399, odds ratios (ORs) for prostate cancer risk associated with medium (732-1,529 microg/day) and high (>1,529 microg/day) lycopene intake were 0.59 (95% confidence interval = 0.23-1.50) and 0.21 (0.06-0.71), respectively (P(trend) < 0.01). Similar analyses for persons with Arg/Gln or Gln/Gln genotypes produced null results. Above-median (1,048 microg/day) lycopene intake combined with above-median levels of alpha-tocopherol and beta-carotene was associated with an OR of 0.11 (0.02-0.65) among men with the Arg/Arg genotype but not those with at least one Gln allele (P(interaction) = 0.01). Although limited by small sample size, these findings indicate that the association between lycopene and prostate cancer is complex and may be modified by other antioxidants and by XRCC1 genotype.

Tobacco smoking and breast cancer risk: an evaluation based on a systematic review of epidemiological evidence among the Japanese population

BACKGROUND

Our research group undertook an appraisal of the body of epidemiological studies on cancer in Japan to evaluate the existing evidence concerning the association between health-related lifestyles and cancer. As tobacco smoking may be one of the few modifiable risk factors for breast cancer, we focused on the association between tobacco smoking and the risk of breast cancer in this review.

METHODS

A MEDLINE search was conducted to identify epidemiological studies on the association between smoking and breast cancer incidence or mortality among the Japanese from 1966 to 2005. Evaluation of associations was based on the strength of evidence and the magnitude of association, together with biological plausibility as previously evaluated by the International Agency for Research on Cancer.

RESULTS

Three cohort studies and eight case-control studies were identified. The relative risk (RR) or odds ratio (OR) of breast cancer for current smokers ranged from 0.71 to 6.26 in these studies. A significantly increased risk among current smokers compared with never smokers (RR = 1.7) was reported in one out of the three cohort studies. Moderate or strong associations between smoking and breast cancer risk (OR > 2.0) were observed in four of the eight case-control studies. Experimental studies have supported the biological plausibility of a positive association between tobacco smoking and breast cancer risk.

CONCLUSION

We conclude that tobacco smoking possibly increases the risk of breast cancer in the Japanese population.