Nucleotide excision repair polymorphisms may modify ionizing radiation-related breast cancer risk in US radiologic technologists

Cosmic Ionizing Radiation: A DNA Damaging Agent That May Underly Excess Cancer in Flight Crews

In the United States, the Federal Aviation Administration has officially classified flight crews (FC) consisting of commercial pilots, cabin crew, or flight attendants as "radiation workers" since 1994 due to the potential for cosmic ionizing radiation (CIR) exposure at cruising altitudes originating from solar activity and galactic sources. Several epidemiological studies have documented elevated incidence and mortality for several cancers in FC, but it has not yet been possible to establish whether this is attributable to CIR. CIR and its constituents are known to cause a myriad of DNA lesions, which can lead to carcinogenesis unless DNA repair mechanisms remove them. But critical knowledge gaps exist with regard to the dosimetry of CIR, the role of other genotoxic exposures among FC, and whether possible biological mechanisms underlying higher cancer rates observed in FC exist. This review summarizes our understanding of the role of DNA damage and repair responses relevant to exposure to CIR in FC. We aimed to stimulate new research directions and provide information that will be useful for guiding regulatory, public health, and medical decision-making to protect and mitigate the risks for those who travel by air.

Molecular targets that sensitize cancer to radiation killing: From the bench to the bedside

Radiotherapy is a standard cytotoxic therapy against solid cancers. It uses ionizing radiation to kill tumor cells through damage to DNA, either directly or indirectly. Radioresistance is often associated with dysregulated DNA damage repair processes. Most radiosensitizers enhance radiation-mediated DNA damage and reduce the rate of DNA repair ultimately leading to accumulation of DNA damages, cell-cycle arrest, and cell death. Recently, agents targeting key signals in DNA damage response such as DNA repair pathways and cell-cycle have been developed. This new class of molecularly targeted radiosensitizing agents is being evaluated in preclinical and clinical studies to monitor their activity in potentiating radiation cytotoxicity of tumors and reducing normal tissue toxicity. The molecular pathways of DNA damage response are reviewed with a focus on the repair mechanisms, therapeutic targets under current clinical evaluation including ATM, ATR, CDK1, CDK4/6, CHK1, DNA-PKcs, PARP-1, Wee1, & MPS1/TTK and potential new targets (BUB1, and DNA LIG4) for radiation sensitization.

Cancer Effects of Low to Moderate Doses of Ionizing Radiation in Young People with Cancer-Predisposing Conditions: A Systematic Review

Moderate to high doses of ionizing radiation (IR) are known to increase the risk of cancer, particularly following childhood exposure. Concerns remain regarding risks from lower doses and the role of cancer-predisposing factors (CPF; genetic disorders, immunodeficiency, mutations/variants in DNA damage detection or repair genes) on radiation-induced cancer (RIC) risk. We conducted a systematic review of evidence that CPFs modify RIC risk in young people. Searches were performed in PubMed, Scopus, Web of Science, and EMBASE for epidemiologic studies of cancer risk in humans (<25 years) with a CPF, exposed to low-moderate IR. Risk of bias was considered. Fifteen articles focusing on leukemia, lymphoma, breast, brain, and thyroid cancers were included. We found inadequate evidence that CPFs modify the risk of radiation-induced leukemia, lymphoma, brain/central nervous system, and thyroid cancers and limited evidence that BRCA mutations modify radiation-induced breast cancer risk. Heterogeneity was observed across studies regarding exposure measures, and the numbers of subjects with CPFs other than BRCA mutations were very small. Further studies with more appropriate study designs are needed to elucidate the impact of CPFs on RIC. They should focus either on populations of carriers of specific gene mutations or on common susceptible variants using polygenic risk scores.

Genetic Association of ERCC6 rs2228526 Polymorphism with the Risk of Cancer: Evidence from a Meta-Analysis

At present, several studies have assessed the association between ERCC6 rs2228526 polymorphism and the risk of cancer. However, the association remained controversial. To provide a more accurate estimate on the association, we performed a meta-analysis search of case-control studies on the associations of ERCC6 rs2228526 with susceptibility to cancer. PubMed, Embase, Google Scholar, Wanfang database, and Chinese National Knowledge Infrastructure databases (CNKI) China Biological Medicine Database (CBM) (up to August 2021) were searched to identify eligible studies. The effect summary odds ratio (OR) with 95% confidence intervals (CI) was applied to assay the association between the ERCC6 rs2228526 polymorphism and the risk of cancer. 14 studies included 15 case-control studies which contained 5,856 cases, and 6,387 controls were finally determined as qualified studies for this meta-analysis. Overall, based on current studies, we found significant association between ERCC6 rs2228526 polymorphism and the risk of cancer in four genetic models [the allele model G vs. A: 1.10, (1.03–1.17); the homozygous model GG vs. AA: 1.27, (1.07–1.51); heterozygote model GA vs. AA: 1.08, (1.00–1.17); the dominant model GG + GA vs. AA: 1.10, (1.02–1.19); the recessive model GG vs. GA + AA: 1.22, (1.03–1.45)]. In the stratified analysis based on ethnicity, we found significant association in two genetic models in Asians. Further, significant genetic cancer susceptibility was found under PB control on subgroup analysis by source of control. In addition, no significant association was found in lung cancer and bladder cancer patients in subgroup analyses based on cancer style. This study suggests that the ERCC6 rs2228526 polymorphism may be associated with increased cancer risk.

PA1 cells containing a truncated DNA polymerase β protein are more sensitive to gamma radiation

PURPOSE

DNA polymerase β (Polβ) acts in the base excision repair (BER) pathway. Mutations in DNA polymerase β (Polβ) are associated with different cancers. A variant of Polβ with a 97 amino acid deletion (PolβΔ), in heterozygous conditions with wild-type Polβ, was identified in sporadic ovarian tumor samples. This study aims to evaluate the gamma radiation sensitivity of PolβΔ for possible target therapy in ovarian cancer treatment.

MATERIALS AND METHODS

PolβΔ cDNA was cloned in a GFP vector and transfected in PA1 cells. Stable cells (PA1PolβΔ) were treated with 60Co sourced gamma-ray (0-15 Gy) to investigate their radiation sensitivity. The affinity of PolβΔ with DNA evaluated by DNA protein in silico docking experiments.

RESULTS

The result showed a statistically significant (p < 0.05) higher sensitivity towards radiation at different doses (0-15 Gy) and time-point (48-72 hours) for PA1PolβΔ cells in comparison with normal PA1 cells. Ten Gy of gamma radiation was found to be the optimal dose. Significantly more PA1PolβΔ cells were killed at this dose than PA1 cells after 48 hours of treatment via an apoptotic pathway. The in silico docking experiments revealed that PolβΔ has more substantial binding potential towards the dsDNA than wild-type Polβ, suggesting a possible failure of BER pathway that results in cell death.

CONCLUSION

Our study showed that the PA1PolβΔ cells were more susceptible than PA1 cells to gamma radiation. In the future, the potentiality of ionizing radiation to treat this type of cancer will be checked in animal 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.

Altering DNA Repair to Improve Radiation Therapy: Specific and Multiple Pathway Targeting

Radiation therapy (RT) is widely used in cancer care strategies. Its effectiveness relies mainly on its ability to cause lethal damage to the DNA of cancer cells. However, some cancers have shown to be particularly radioresistant partly because of efficient and redundant DNA repair capacities. Therefore, RT efficacy might be enhanced by using drugs that can disrupt cancer cells' DNA repair machinery. Here we review the recent advances in the development of novel inhibitors of DNA repair pathways in combination with RT. A large number of these compounds are the subject of preclinical/clinical studies and target key enzymes involved in one or more DNA repair pathways. A totally different strategy consists of mimicking DNA double-strand breaks via small interfering DNA (siDNA) to bait the whole DNA repair machinery, leading to its global inhibition.

Genetic susceptibility to radiation-induced breast cancer after Hodgkin lymphoma

Female Hodgkin lymphoma (HL) patients treated with chest radiotherapy (RT) have a very high risk of breast cancer. The contribution of genetic factors to this risk is unclear. We therefore examined 211 155 germline single-nucleotide polymorphisms (SNPs) for gene-radiation interaction on breast cancer risk in a case-only analysis including 327 breast cancer patients after chest RT for HL and 4671 first primary breast cancer patients. Nine SNPs showed statistically significant interaction with RT on breast cancer risk (false discovery rate, <20%), of which 1 SNP in the PVT1 oncogene attained the Bonferroni threshold for statistical significance. A polygenic risk score (PRS) composed of these SNPs (RT-interaction-PRS) and a previously published breast cancer PRS (BC-PRS) derived in the general population were evaluated in a case-control analysis comprising the 327 chest-irradiated HL patients with breast cancer and 491 chest-irradiated HL patients without breast cancer. Patients in the highest tertile of the RT-interaction-PRS had a 1.6-fold higher breast cancer risk than those in the lowest tertile. Remarkably, we observed a fourfold increased RT-induced breast cancer risk in the highest compared with the lowest decile of the BC-PRS. On a continuous scale, breast cancer risk increased 1.4-fold per standard deviation of the BC-PRS, similar to the effect size found in the general population. This study demonstrates that genetic factors influence breast cancer risk after chest RT for HL. Given the high absolute breast cancer risk in radiation-exposed women, these results can have important implications for the management of current HL survivors and future patients.

XPG rs17655 G>C polymorphism associated with cancer risk: evidence from 60 studies

Xeroderma pigmentosum group G (XPG), a key component in nucleotide excision repair pathway, functions to cut DNA lesions during DNA repair. Genetic variations that alter DNA repair gene expression or function may decrease DNA repair ability and impair genome integrity, thereby predisposing to cancer. The association between XPG rs17655 G>C polymorphism and cancer risk has been investigated extensively, but the results remain contradictory. To get a more accurate conclusion, we performed a comprehensive meta-analysis of 60 case-control studies, involving 27,098 cancer cases and 30,535 healthy controls. Crude odds ratios (ORs) and 95% confidence interval (CIs) were calculated to determine the association of interest. Pooled analysis indicated that the XPG rs17655 G>C polymorphism increased the risk of overall cancer (CC vs. GG: OR=1.10, 95% CI=1.00-1.20; CG vs. GG: OR=1.06, 95% CI=1.02-1.11; CG+CC vs. GG: OR=1.07, 95% CI=1.02-1.12; C vs. G: OR=1.05, 95% CI=1.01-1.09). Stratification analysis by cancer type further showed that this polymorphism was associated with increased risk of gastric cancer and colorectal cancer. This meta-analysis indicated that the XPG gene rs17655 G>C polymorphism was associated with increased overall cancer risk, especially the risk of gastric cancer and colorectal cancer. Further validation experiments are needed to strength our conclusion.

XPF polymorphism toward lung cancer susceptibility and survival in patients treated with platinum-based chemotherapy

AIM

To evaluate the association of three XPF polymorphic variants (673 C>T, 11985 A>G, G415A) with lung cancer, overall survival and clinical response in North Indians.

METHODS

Genotyping was performed using PCR-restriction fragment length polymorphism.

RESULTS

A total of 673 C>T polymorphism was associated with 1.5-fold increased lung cancer risk for heterozygous genotype (CT; p = 0.03). Adenocarcinoma patients with 673 C>T polymorphism carrying heterozygous genotype (CT) had a lower hazard ratio (p = 0.01). Classification and regression tree analysis predicted XPF 673 C>T (M) as the strongest risk factor for the lung cancer (p = 0.003). For 11985 A>G polymorphism, lung cancer subjects treated with irinotecan cisplatin/carboplatin regimen having heterozygous genotype (AG) was associated with high mortality risk (p = 0.0001).

CONCLUSION

673 C>T polymorphism was associated with increased lung cancer risk.

Haplotype analysis on relationship of ERCC2 and ERCC3 gene polymorphisms with osteosarcoma risk in Chinese young population

The purpose of the study was to investigate the association of single-nucleotide polymorphisms (SNPs) within excision repair cross-complementation (ERCC) gene polymorphisms, additional gene-gene interaction, and haplotype combination with osteosarcoma risk. Generalized multifactor dimensionality reduction (GMDR) was used to screen the best interaction combination among SNPs. Logistic regression was performed to investigate the association between six SNPs within ERCC gene, additional gene-gene interaction on osteosarcoma risk. Haplotype analysis was performed using SNPstats ( http://bioinfo.iconcologia.net/SNPstats ). Osteosarcoma risk was significantly higher in carriers with the T allele of ERCC2-rs1799793 than those with GG genotype (GT+ TT vs. GG), adjusted OR (95% CI) = 1.56 (1.13-2.01), and higher in carriers with the A allele of ERCC3-rs4150441 than those with GG genotype (GA+ AA vs. GG), adjusted OR (95% CI) = 1.63 (1.25-2.09). GMDR model indicated a significant two-locus model (p = 0.0107) involving rs1799793 and rs4150441; cross-validation consistency of the two-locus model was 9/10; and the testing accuracy was 60.11%. Participants rs1799793-GT or -TT and rs4150441-GA or -AA genotype have the highest osteosarcoma risk, compared to subjects with rs1799793-GG and rs4150441-GG genotype, OR (95% CI) = 2.87 (1.21-4.63), after covariates adjustment. Haplotype containing the rs1799793-T and rs11615-T alleles was associated with a statistically increased osteosarcoma risk, OR (95% CI) = 1.47 (1.12-1.92). We found that the T allele of ERCC2-rs1799793 and the A allele of ERCC3-rs4150441, interaction between rs1799793 and rs4150441, and haplotype containing the rs1799793T and rs11615-T alleles were all associated with increased osteosarcoma risk.

Functional Analysis of SNPs in the ERCC5 Promoter in Advanced Colorectal Cancer Patients Treated With Oxaliplatin-Based Chemotherapy

The promoter is the center for regulation of gene transcription due to containing numerous transcription factor binding sites. The aim of the study was to determine whether genetic variations at excision repair cross complementation group 5 (ERCC5) promoter could affect transcription factor binding and whether such single nucleotide polymorphism (SNP)-dependent binding could affect gene expression, drug response, and clinical outcome.A total of 170 patients who were cytologically or histologically confirmed with advanced colorectal cancer (CRC), at least 1 measurable lesion, and underwent oxaliplatin-based chemotherapy were studied. The polymerase chain reaction-ligation detection reaction (PCR-LDR) was used to analyze SNPs. The reporter gene assay system and electrophoretic mobility shift assays (EMSA) were performed to investigate the effect of SNPs on the ERCC5 promoter activity and DNA-binding activity, respectively. The mRNA and protein expression of ERCC5 in tumor tissues of colorectal cancer patients with different genotypes were detected by real-time PCR and western blot, respectively.Both -763A and -763G allele had nuclear protein-binding ability. +25A allele did not show any nuclear protein-binding ability, whereas +25G allele did. The relative luciferase activity of the -763A/+25G haplotype was significantly higher than other 3 haplotypes (P < 0.05). The expression level of ERCC5 mRNA and protein was significantly higher in tumor tissues with -763AA+25GG genotype combination than that with -763GG+25AA genotype combination (P < 0.05, respectively). Allelic variants (-763AA vs -763AG or -763GG, +25GG versus +25AG or +25AA) were significantly associated with shorter progression-free survival (PFS) and overall survival (OS) (P < 0.05, respectively). At multivariate analysis, patients with risk genotypes (-763AA or +25GG genotype) demonstrated a significantly increasing risk of progression (P = 0.01) or worse OS (P = 0.001).The ERCC5 promoter polymorphisms at -763 and +25 may be important functional variants and predictors of clinical outcome of CRC patients who received oxaliplatin chemotherapy.

A New Era of Low-Dose Radiation Epidemiology

The last decade has introduced a new era of epidemiologic studies of low-dose radiation facilitated by electronic record linkage and pooling of cohorts that allow for more direct and powerful assessments of cancer and other stochastic effects at doses below 100 mGy. Such studies have provided additional evidence regarding the risks of cancer, particularly leukemia, associated with lower-dose radiation exposures from medical, environmental, and occupational radiation sources, and have questioned the previous findings with regard to possible thresholds for cardiovascular disease and cataracts. Integrated analysis of next generation genomic and epigenetic sequencing of germline and somatic tissues could soon propel our understanding further regarding disease risk thresholds, radiosensitivity of population subgroups and individuals, and the mechanisms of radiation carcinogenesis. These advances in low-dose radiation epidemiology are critical to our understanding of chronic disease risks from the burgeoning use of newer and emerging medical imaging technologies, and the continued potential threat of nuclear power plant accidents or other radiological emergencies.

Nucleotide Excision Repair Gene ERCC2 and ERCC5 Variants Increase Risk of Uterine Cervical Cancer

Purpose

Defects in the DNA damage repair process can cause genomic instability and play an important role in cervical carcinogenesis. The purpose of this study was to analyze the association of 29 candidate single nucleotide polymorphisms (SNPs) in genes in the DNA repair pathway, TP53, and TP53BP1 with the risk of cervical cancer.

Materials and Methods

Twenty-nine SNPs in four genes in the DNA repair pathway (ERCC2, ERCC5, NBS1, and XRCC1), TP53, and TP53BP1 were genotyped for 478 cervical cancer patients and 922 healthy control subjects, and their effects on cervical carcinogenesis were analyzed.

Results

The most significant association was found for rs17655 in ERCC5, with an age-adjusted p-value < 0.0001, for which a strong additive effect of the risk allele C was observed (odds ratio, 2.01 for CC to GG). On the other hand, another significant polymorphism rs454421 in ERCC2 showed a dominant effect (odds ratio, 1.68 for GA+AA to GG) with an age-adjusted p-value of 0.0009. The association of these polymorphisms remained significant regardless of the age of onset. The significant result for rs17655 was also consistent for subgroups of patients defined by histology and human papillomavirus (HPV) types. However, for rs454421, the association was observed only in patients with squamous cell carcinoma and non-HPV 18 type.

Conclusion

The results of this study show a novel association of cervical cancer and the genes involved in the nucleotide excision pathway in the Korean population.

Association between ERCC5 gene polymorphisms and breast cancer risk

We conducted a case-control study to evaluate the association between ERCC5 polymorphism and breast cancer risk. 325 breast cancer patients and 325 controls were recruited in our study between January 2011 and March 2014. ERCC5 rs1047768, rs2094258, rs2296147, rs751402 and rs873601 polymorphisms were genotyped, using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. By logistic regression analysis, we found that individuals with AA genotype of rs2094258 was associated with increased risk of breast cancer when compared with wide-type genotype, and the OR (95% CI) was 1.80 (1.12-2.92) for AA genotype. Individuals with GA+GG genotype of rs2094258 were significantly correlated with increased risk of breast cancer in tobacco smokers, and the OR (95% CI) was 7.35 (1.21-47.20). In conclusion, our study indicated that ERCC5 rs2094258 polymorphism may contribute to the risk of breast cancer.

Interleukin-12 preserves the cutaneous physical and immunological barrier after radiation exposure

The United States continues to be a prime target for attack by terrorist organizations in which nuclear detonation and dispersal of radiological material are legitimate threats. Such attacks could have devastating consequences to large populations, in the form of radiation injury to various human organ systems. One of these at risk organs is the cutaneous system, which forms both a physical and immunological barrier to the surrounding environment and is particularly sensitive to ionizing radiation. Therefore, increased efforts to develop medical countermeasures for treatment of the deleterious effects of cutaneous radiation exposure are essential. Interleukin-12 (IL-12) was shown to elicit protective effects against radiation injury on radiosensitive systems such as the bone marrow and gastrointestinal tract. In this article, we examined if IL-12 could protect the cutaneous system from a combined radiation injury in the form of sublethal total body irradiation and beta-radiation burn (β-burn) directly to the skin. Combined radiation injury resulted in a breakdown in skin integrity as measured by transepidermal water loss, size of β-burn lesion and an exacerbated loss of surveillant cutaneous dendritic cells. Interestingly, intradermal administration of IL-12 48 h postirradiation reduced transepidermal water loss and burn size, as well as retention of cutaneous dendritic cells. Our data identify IL-12 as a potential mitigator of radiation-induced skin injury and argue for the further development of this cytokine as a radiation countermeasure.

Predictive impact of genetic polymorphisms in DNA repair genes on susceptibility and therapeutic outcomes to colorectal cancer patients

Several hereditary syndromes characterized by defective DNA repair are associated with high risk of colorectal cancer (CRC). To explore whether common polymorphisms in DNA repair genes affect risk and prognosis of CRC, we evaluated the association between single nucleotide polymorphisms (SNPs) in XPG, XPC, and WRN gene and susceptibility of CRC, and clinical outcomes in a population-based case-control study. A total of 890 CRC cases and 910 controls recruited into the study provided a biologic sample. Individuals with variant genotypes of XPC Ala499Val appeared to be associated with the increased risk of CRC. WRN Cys1367Arg variants carriers showed an increased susceptibility for CRC. More importantly, the risk of CRC increased further in a combined analysis of multiple polymorphisms. Furthermore, stratified analyses revealed that XPG Arg1104His polymorphism was associated with tumor differentiation of CRC patients (P = 0.043). Log-rank test and adjusted multivariate Cox regression analysis verified that XPG Arg1104His variants were associated with a longer disease-free survival (DFS) [CG genotype: adjusted HR (95% confidence interval (CI)) = 0.163 (0.107-0.248), P < 0.001; CC genotype: adjusted HR (95% CI) = 0.333 (0.235-0.470), P < 0.001; CG/CC genotype: adjusted HR (95% CI) = 0.333 (0.235-0.470)] in patients with oxaliplatin-based chemotherapy (N = 718). Moreover, XPC Ala499Val CT genotype showed a significant impact on DFS [CC genotype: adjusted HR (95% CI) = 0.691 (0.528-0.904), P = 0.007; CT/CC genotype: adjusted HR (95% CI) = 0.602 (0.389-0.934), P = 0.024]. However, no correlation was found between WRN Cys1367Arg polymorphism and prognosis in CRC patients. Our findings will add to the literature on the impact of genetic variation in DNA repair genes involved in susceptibility for CRC and therapeutic outcomes in response to oxaliplatin-based chemotherapy.

Genetic variation as a modifier of association between therapeutic exposure and subsequent malignant neoplasms in cancer survivors

Subsequent malignant neoplasms (SMNs) are associated with significant morbidity and are a major cause of premature mortality among cancer survivors. Several large studies have demonstrated a strong association between the radiation and/or chemotherapy used to treat primary cancer and the risk of developing SMNs. However, for any given therapeutic exposure, the risk of developing an SMN varies between individuals. Genomic variation can potentially modify the association between therapeutic exposures and SMN risk and may explain the observed interindividual variability. In this review, the author provides a brief overview of the current knowledge regarding the role of genomic variation in the development of therapy-related SMNs and discusses the methodological challenges in undertaking an endeavor to develop a deeper understanding of the molecular underpinnings of therapy-related SMNs, such as an appropriate study design, the identification of an adequately sized study population together with a reliable plan for collecting and maintaining high-quality DNA, clinical validation of the phenotype, and the selection of an appropriate approach or platform for genotyping. Understanding the factors that can modify the risk of treatment-related SMNs is critical to developing targeted intervention strategies and optimizing risk-based health care for cancer survivors.

Associations of ERCC4 rs1800067 polymorphism with cancer risk: an updated meta-analysis

BACKGROUND

RESULTS from previous studies concerning the association of ERCC4 rs1800067 polymorphism with risk of cancer were inconsistent. To explore the exact relation with susceptibility, we conducted the present meta-analysis.

MATERIALS AND METHODS

Literature of electronic databases including PubMed, Web of Science, EMBASE, Wanfang and Chinese National Knowledge Infrastructure (CNKI) were systematically searched. ORs and their 95%CIs were used to assess the strength of associations between ERCC4 polymorphism and cancer risk.

RESULTS

There was no significant association between ERCC4 rs1800067 AA or AG genotypes and overall risk of cancer (AA vs. GG: OR=0.998, 95%CI=0.670-1.486, P=0.992; AG vs. GG: OR=0.970, 95%CI=0.888- 1.061, P=0.508). A dominant genetic model also did not demonstrate significant association of (AA+AG) genotype carriers with altered risk of overall cancer (OR=0.985, 95%CI=0.909-1.068, P=0.719). In addition, no significant association was observed between A allele of ERCC4 rs1800067 A/G polymorphism and altered cancer risk compared with G allele (OR=0.952, 95%CI=0.851-1.063, P=0.381). Subgroup analysis suggested that AA genotype carriers were significantly associated with decreased risk of glioma compared with wild-type GG genotype individuals (OR=0.523, 95%CI=0.275-0.993, P=0.048). For subgroup of lung cancer, A allele of ERCC4 rs1800067 A/G polymorphism was significantly associated with decreased risk of lung cancer compared with G allele (OR=0.806, 95%CI=0.697-0.931, P=0.003).

CONCLUSIONS

This meta-analysis indicated that ERCC4 rs1800067 A/G polymorphism might not be associated with risk of overall cancer. However, individuals with the AA genotype were associated with significantly reduced risk of glioma compared with wild-type GG genotype; The A allele was associated with significantly reduced risk of lung cancer compared with G allele. Future large- scale studies performed in multiple populations are warranted to confirm our results.

The DNA repair gene ERCC6 rs1917799 polymorphism is associated with gastric cancer risk in Chinese

OBJECTIVE

Excision repair cross-complementing group 6 (ERCC6) is a major component of the nucleotide excision repair pathway that plays an important role in maintaining genomic stability and integrity. Several recent studies suggested a link of ERCC6 polymorphisms with susceptibility to various cancers. However, the relation of ERCC6 polymorphism with gastric cancer (GC) risk remains elusive. In this sex- and age- matched case-control study including 402 GC cases and 804 cancer-free controls, we aimed to investigate the association between a potentially functional polymorphism (rs1917799 T>G) in the ERCC6 regulatory region and GC risk.

METHODS

The genotypes of rs1917799 were determined by Sequenom MassARRAY platform and the status of Helicobacter pylori infection was detected by enzyme-linked immunosorbent assay. Odd ratios (ORs) and 95% confidential interval (CI) were calculated by logistic regression analysis.

RESULTS

Compared with the common TT genotype, the ERCC6 rs1917799 GG genotype was associated with increased GC risk (adjusted OR=1.46, 95%CI: 1.03-2.08, P=0.035). When compared with (GT+TT) genotypes, the GG genotype also demonstrated a statistical association with increased GC risk (adjusted OR=1.38, 95%CI: 1.01-1.89, P=0.044). This was also observed for the male subpopulation (GG vs. TT: adjusted OR=1.71, 95%CI: 1.12-2.62, P=0.013; G allele vs. T allele: adjusted OR=1.32, 95%CI: 1.07-1.62, P=0.009). Genetic effects on increased GC risk tended to be enhanced by H. pylori infection, smoking and drinking, but their interaction effects on GC risk did not reach statistical significance.

CONCLUSIONS

ERCC6 rs1917799 GG genotype might be associated with increased GC risk in Chinese, especially in males.

Association of xeroderma pigmentosum complementation group G Asp1104His polymorphism with breast cancer risk: A cumulative meta-analysis

The xeroderma pigmentosum complementation group G (XPG) gene plays an important role in the DNA nucleotide excision repair (NER) pathway. Several studies have investigated the association between the XPG Asp1104His polymorphism and breast cancer; however, the results have been inconsistent. Therefore, we conducted a meta-analysis of 8 published articles (10 case-control studies) including a total of 5,235 patients with breast cancer and 5,685 healthy controls. The results demonstrated that the XPG Asp1104His polymorphism was not associated with breast cancer in the overall population [His vs. Asp, odds ratio (OR)=1.00, 95% confidence interval (CI): 0.91-1.08; His/His vs. Asp/Asp, OR=0.96, 95% CI: 0.83-1.11; Asp/His vs. Asp/Asp, OR=1.02, 95% CI: 0.94-1.11; His/His+Asp/His vs. Asp/Asp, OR=1.03, 95% CI: 0.92-1.15; and His/His vs. Asp/Asp+Asp/His, OR=0.93, 95% CI: 0.81-1.06]. In the subgroup analysis by ethnicity, no significant association was observed in European subjects. In conclusion, this meta-analysis suggested that the XPG Asp1104His polymorphism is not associated with breast cancer risk.

Association between the XPG Asp1104His and XPF Arg415Gln polymorphisms and risk of cancer: a meta-analysis

BACKGROUND

The XPG (xeroderma pigmentosum type G) Asp1104His and XPF (xeroderma pigmentosum type F) Arg415Gln polymorphisms had been implicated in cancer susceptibility. The previous published data on the association between XPG Asp1104His and XPF Arg415Gln polymorphisms and cancer risk remained controversial.

METHODOLOGY/PRINCIPAL FINDINGS

To derive a more precise estimation of the association between the XPG Asp1104His and XPF Arg415Gln polymorphisms and overall cancer risk, we performed a meta-analysis to investigate the association between cancer susceptibility and XPG Asp1104His (32,162 cases and 39,858 controls from 66 studies) and XPF Arg415Gln polymorphisms (17,864 cases and 20,578 controls from 32 studies) in different inheritance models. We used odds ratios with 95% confidence intervals to assess the strength of the association. Overall, significantly elevated cancer risk was found when all studies were pooled into the meta-analysis of XPG Asp1104His (dominant model: OR = 1.05, 95% CI = 1.00-1.10; Asp/His vs. Asp/Asp: OR = 1.06, 95% CI = 1.01-1.11). In the further stratified and sensitivity analyses, significantly decreased lung cancer risk was found for XPF Arg415Gln (dominant model: OR = 0.82, 95% CI = 0.71-0.96; Arg/Gln versus Arg/Arg: OR = 0.83, 95% CI = 0.71-0.97; additive model: OR = 0.83, 95% CI = 0.72-0.95) and significantly increased other cancer risk was found among hospital-based studies for XPG Asp1104His (dominant model: OR = 1.23, 95% CI = 1.02-1.49).

CONCLUSIONS/SIGNIFICANCE

In summary, this meta-analysis suggests that XPF Arg415Gln polymorphism may be associated with decreased lung cancer risk and XPG Asp1104His may be a low-penetrant risk factor in some cancers development. And larger scale primary studies are required to further evaluate the interaction of XPG Asp1104His and XPF Arg415Gln polymorphisms and cancer risk in specific populations.

Therapy-related myelodysplasia and acute myeloid leukemia

Therapy-related leukemia (myelodysplasia and acute myeloid leukemia-t-MDS/AML) is a well-known complication of conventional chemoradiotherapy used to treat a variety of primary malignancies including Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL), acute lymphoblastic leukemia (ALL), sarcoma, and ovarian and testicular cancers. The median time to development of t-MDS/AML is 3-5 years, with the risk decreasing markedly after the first decade. t-MDS/AML is the major cause of non-relapse mortality after autologous hematopoietic cell transplantation (HCT) for HL or NHL. The magnitude of risk of t-MDS/AML is higher, and the latency is shorter after HCT, compared to conventional therapy. Two types of t-MDS/AML are recognized depending on the causative therapeutic exposure: an alkylating agent/radiation-related type and a topoisomerase II inhibitor-related type. Inter-individual variability in the risk for development of t-MDS/AML suggests a role for genetic variation in susceptibility to genotoxic exposures. Treatment of t-MDS/AML with conventional therapy is associated with a uniformly poor prognosis, with a median survival of 6 months. Because of the poor response to conventional chemotherapy, allogeneic HCT is recommended. Current research is focused on developing risk prediction and risk reduction strategies.

Second malignant neoplasms and cardiovascular disease following radiotherapy

Second malignant neoplasms (SMNs) and cardiovascular disease (CVD) are among the most serious and life-threatening late adverse effects experienced by the growing number of cancer survivors worldwide and are due in part to radiotherapy. The National Council on Radiation Protection and Measurements (NCRP) convened an expert scientific committee to critically and comprehensively review associations between radiotherapy and SMNs and CVD, taking into account radiobiology; genomics; treatment (i.e., radiotherapy with or without chemotherapy and other therapies); type of radiation; and quantitative considerations (i.e., dose-response relationships). Major conclusions of the NCRP include: (1) the relevance of older technologies for current risk assessment when organ-specific absorbed dose and the appropriate relative biological effectiveness are taken into account and (2) the identification of critical research needs with regard to newer radiation modalities, dose-response relationships, and genetic susceptibility. Recommendation for research priorities and infrastructural requirements include (1) long-term large-scale follow-up of extant cancer survivors and prospectively treated patients to characterize risks of SMNs and CVD in terms of radiation dose and type; (2) biological sample collection to integrate epidemiological studies with molecular and genetic evaluations; (3) investigation of interactions between radiotherapy and other potential confounding factors, such as age, sex, race, tobacco and alcohol use, dietary intake, energy balance, and other cofactors, as well as genetic susceptibility; (4) focusing on adolescent and young adult cancer survivors, given the sparse research in this population; and (5) construction of comprehensive risk prediction models for SMNs and CVD to permit the development of follow-up guidelines and prevention and intervention strategies.

XPD Asp312Asn and Lys751Gln polymorphisms and breast cancer susceptibility: a meta-analysis

The association between xeroderma pigmentosum complementation group D (XPD) Asp312Asn and Lys751Gln gene polymorphisms and breast cancer risk has been widely reported, but the results were inconsistent. In order to derive a more precise estimation of the relationship, a meta-analysis was performed. A comprehensive search strategy was conducted towards the electronic databases including Medline, PubMed, Web of Science, Embase, and Chinese Biomedical Literature Database (Chinese). The association between the XPD polymorphism and breast cancer risk was conducted by odds ratios (ORs) and 95 % confidence intervals (95 % CIs). A total of 22 studies with 18,136 cases and 18,351 controls were included in our meta-analysis. Among these, 12 studies with 7,667 cases and 7,480 controls for Asp312Asn polymorphism and 20 studies with 10,469 cases and 10,871 controls for Lys751Gln polymorphism. With regard to Asp312Asn polymorphism, no significantly associated was found with breast cancer risk. However, significant association was found between Lys751Gln polymorphism and breast cancer risk under all genetic models in overall populations (C vs. A—OR = 1.10, 95 % CI = 1.04–1.17, P = 0.002; CC vs. AA—OR = 1.17, 95 % CI = 1.06–1.30, P = 0.003; AC vs. AA—OR = 1.06, 95 % CI = 1.01–1.12, P = 0.032; CC vs. AC/AA—OR = 1.17, 95 % CI = 1.04–1.32, P = 0.009; CC/AC vs. AA—OR = 1.07, 95 % CI = 1.02–1.12, P = 0.005). In subgroup analysis base on ethnicity, significance was found in Caucasians and mix. The results suggest that XPD Asp312Asn polymorphism was not associated with breast cancer. The XPD Lys751Gln polymorphism significantly increased breast cancer risk, especially for Caucasian and mix.

GSTP1, ERCC1 and ERCC2 polymorphisms, expression and clinical outcome of oxaliplatin-based adjuvant chemotherapy in colorectal cancer in Chinese population

AIM

Platinum agents have shown to be effective in the treatment of colorectal cancer. We assessed whether single nucleotide polymorphisms (SNPs) in GSTP1, ERCC1 Asn118Asn and ERCC2 Lys751Gln might predict the overall survival in patients receiving oxaliplatin-based chemotherapy in a Chinese population.

METHODS

SNPs of GSTP1, ERCC1 Asn118Asn and ERCC2 Lys751Gln in 335 colorectal cancer patients were assessed using TaqMan nuclease assays.

RESULTS

At the time of final analysis on Nov. 2011, the median follow-up period was 37.7 months (range from 1 to 60 months). A total of 229 patients died during follow-up. Our study showed GSTP1 Val/Val (HR=0.44, 95% CI=0.18-0.98), ERCC1 C/C (HR=0.20, 95% CI=0.10-0.79) and ERCC2 G/G (HR=0.48, 95% CI=0.19-0.97) to be significantly associated with better survival of colorectal cancer. GSTP1 Val/Val, ERCC1 C/C and ERCC2 G/G were also related to longer survival among patients with colon cancer, with HRs (95% CIs) of 0.41 (0.16-0.91), 0.16 (0.09-0.74) and 0.34 (0.16-0.91), respectively.

CONCLUSION

GSTP1, GSTP1, ERCC1 Asn118Asn and ERCC2 Lys751Gln genotyping might facilitate tailored oxaliplatin-based chemotherapy for colorectal cancer patients.

Assessing SNP-SNP interactions among DNA repair, modification and metabolism related pathway genes in breast cancer susceptibility

Genome-wide association studies (GWASs) have identified low-penetrance common variants (i.e., single nucleotide polymorphisms, SNPs) associated with breast cancer susceptibility. Although GWASs are primarily focused on single-locus effects, gene-gene interactions (i.e., epistasis) are also assumed to contribute to the genetic risks for complex diseases including breast cancer. While it has been hypothesized that moderately ranked (P value based) weak single-locus effects in GWASs could potentially harbor valuable information for evaluating epistasis, we lack systematic efforts to investigate SNPs showing consistent associations with weak statistical significance across independent discovery and replication stages. The objectives of this study were i) to select SNPs showing single-locus effects with weak statistical significance for breast cancer in a GWAS and/or candidate-gene studies; ii) to replicate these SNPs in an independent set of breast cancer cases and controls; and iii) to explore their potential SNP-SNP interactions contributing to breast cancer susceptibility. A total of 17 SNPs related to DNA repair, modification and metabolism pathway genes were selected since these pathways offer a priori knowledge for potential epistatic interactions and an overall role in breast carcinogenesis. The study design included predominantly Caucasian women (2,795 cases and 4,505 controls) from Alberta, Canada. We observed two two-way SNP-SNP interactions (APEX1-rs1130409 and RPAP1-rs2297381; MLH1-rs1799977 and MDM2-rs769412) in logistic regression that conferred elevated risks for breast cancer (P_interaction<7.3×10⁻³). Logic regression identified an interaction involving four SNPs (MBD2-rs4041245, MLH1-rs1799977, MDM2-rs769412, BRCA2-rs1799943) (P_permutation = 2.4×10⁻³). SNPs involved in SNP-SNP interactions also showed single-locus effects with weak statistical significance, while BRCA2-rs1799943 showed stronger statistical significance (P_{correlation/trend} = 3.2×10⁻⁴) than the others. These single-locus effects were independent of body mass index. Our results provide a framework for evaluating SNPs showing statistically weak but reproducible single-locus effects for epistatic effects contributing to disease susceptibility.

Association between the ERCC5 Asp1104His polymorphism and cancer risk: a meta-analysis

BACKGROUND

Excision repair cross complementing group 5 (ERCC5 or XPG) plays an important role in regulating DNA excision repair, removal of bulky lesions caused by environmental chemicals or UV light. Mutations in this gene cause a rare autosomal recessive syndrome, and its functional single nucleotide polymorphisms (SNPs) may alter DNA repair capacity phenotype and cancer risk. However, a series of epidemiological studies on the association between the ERCC5 Asp1104His polymorphism (rs17655, G>C) and cancer susceptibility generated conflicting results.

METHODOLOGY/PRINCIPAL FINDINGS

To derive a more precise estimation of the association between the ERCC5 Asp1104His polymorphism and overall cancer risk, we performed a meta-analysis of 44 published case-control studies, in which a total of 23,490 cases and 27,168 controls were included. To provide additional biological plausibility, we also assessed the genotype-gene expression correlation from the HapMap phase II release 23 data with 270 individuals from 4 ethnic populations. When all studies were pooled, we found no statistical evidence for a significantly increased cancer risk in the recessive genetic models (His/His vs. Asp/Asp: OR = 0.99, 95% CI: 0.92-1.06, P = 0.242 for heterogeneity or His/His vs. Asp/His + Asp/Asp: OR = 0.98, 95% CI: 0.93-1.03, P = 0.260 for heterogeneity), nor in further stratified analyses by cancer type, ethnicity, source of controls and sample size. In the genotype-phenotype correlation analysis from 270 individuals, we consistently found no significant correlation of the Asp1104His polymorphism with ERCC5 mRNA expression.

CONCLUSIONS/SIGNIFICANCE

This meta-analysis suggests that it is unlikely that the ERCC5 Asp1104His polymorphism may contribute to individual susceptibility to cancer risk.

Second malignant neoplasms and cardiovascular disease following radiotherapy

Second malignant neoplasms (SMNs) and cardiovascular disease (CVD) are among the most serious and life-threatening late adverse effects experienced by the growing number of cancer survivors worldwide and are due in part to radiotherapy. The National Council on Radiation Protection and Measurements (NCRP) convened an expert scientific committee to critically and comprehensively review associations between radiotherapy and SMNs and CVD, taking into account radiobiology; genomics; treatment (ie, radiotherapy with or without chemotherapy and other therapies); type of radiation; and quantitative considerations (ie, dose-response relationships). Major conclusions of the NCRP include: 1) the relevance of older technologies for current risk assessment when organ-specific absorbed dose and the appropriate relative biological effectiveness are taken into account and 2) the identification of critical research needs with regard to newer radiation modalities, dose-response relationships, and genetic susceptibility. Recommendation for research priorities and infrastructural requirements include 1) long-term large-scale follow-up of extant cancer survivors and prospectively treated patients to characterize risks of SMNs and CVD in terms of radiation dose and type; 2) biological sample collection to integrate epidemiological studies with molecular and genetic evaluations; 3) investigation of interactions between radiotherapy and other potential confounding factors, such as age, sex, race, tobacco and alcohol use, dietary intake, energy balance, and other cofactors, as well as genetic susceptibility; 4) focusing on adolescent and young adult cancer survivors, given the sparse research in this population; and 5) construction of comprehensive risk prediction models for SMNs and CVD to permit the development of follow-up guidelines and prevention and intervention strategies.

Cancer risks associated with external radiation from diagnostic imaging procedures

The 600% increase in medical radiation exposure to the US population since 1980 has provided immense benefit, but increased potential future cancer risks to patients. Most of the increase is from diagnostic radiologic procedures. The objectives of this review are to summarize epidemiologic data on cancer risks associated with diagnostic procedures, describe how exposures from recent diagnostic procedures relate to radiation levels linked with cancer occurrence, and propose a framework of strategies to reduce radiation from diagnostic imaging in patients. We briefly review radiation dose definitions, mechanisms of radiation carcinogenesis, key epidemiologic studies of medical and other radiation sources and cancer risks, and dose trends from diagnostic procedures. We describe cancer risks from experimental studies, future projected risks from current imaging procedures, and the potential for higher risks in genetically susceptible populations. To reduce future projected cancers from diagnostic procedures, we advocate the widespread use of evidence-based appropriateness criteria for decisions about imaging procedures; oversight of equipment to deliver reliably the minimum radiation required to attain clinical objectives; development of electronic lifetime records of imaging procedures for patients and their physicians; and commitment by medical training programs, professional societies, and radiation protection organizations to educate all stakeholders in reducing radiation from diagnostic procedures.

Using functional signatures to identify repositioned drugs for breast, myelogenous leukemia and prostate cancer

The cost and time to develop a drug continues to be a major barrier to widespread distribution of medication. Although the genomic revolution appears to have had little impact on this problem, and might even have exacerbated it because of the flood of additional and usually ineffective leads, the emergence of high throughput resources promises the possibility of rapid, reliable and systematic identification of approved drugs for originally unintended uses. In this paper we develop and apply a method for identifying such repositioned drug candidates against breast cancer, myelogenous leukemia and prostate cancer by looking for inverse correlations between the most perturbed gene expression levels in human cancer tissue and the most perturbed expression levels induced by bioactive compounds. The method uses variable gene signatures to identify bioactive compounds that modulate a given disease. This is in contrast to previous methods that use small and fixed signatures. This strategy is based on the observation that diseases stem from failed/modified cellular functions, irrespective of the particular genes that contribute to the function, i.e., this strategy targets the functional signatures for a given cancer. This function-based strategy broadens the search space for the effective drugs with an impressive hit rate. Among the 79, 94 and 88 candidate drugs for breast cancer, myelogenous leukemia and prostate cancer, 32%, 13% and 17% respectively are either FDA-approved/in-clinical-trial drugs, or drugs with suggestive literature evidences, with an FDR of 0.01. These findings indicate that the method presented here could lead to a substantial increase in efficiency in drug discovery and development, and has potential application for the personalized medicine.

The effective drug of a given disease is aimed to bring abnormal functions associated with disease back to the normal state. Using expression profile as the surrogate marker of the cellular function, we introduce a novel procedure to identify candidate therapeutics by searching for those bioactive compounds that either down-regulate abnormally over-expressed genes, or up-regulate those that are abnormally under-expressed. We show that the approach detects a pool of plausible candidates as repositioning/new drugs. In contrast to previous studies, our approach uses a variable big number of genes and/or gene combinations as a representation of functional signatures to identify bioactive compounds that modulate a given disease, irrespective of the particular genes that contribute to the cellular functions; therefore it covers potential drugs with heterogeneous properties. The method may also have potential application for the personalized medicine.

Role of genetic susceptibility in development of treatment-related adverse outcomes in cancer survivors

Clear and unambiguous associations have been established between therapeutic exposures and specific complications. However, considerable interindividual variability is observed in the risk of developing an outcome for a given therapeutic exposure. Genetic predisposition and especially its interaction with therapeutic exposures can potentially exacerbate the toxic effect of treatment on normal tissues and organ systems, and can possibly explain the interindividual variability. This article provides a brief overview of the current knowledge about the role of genomic variation in the development of therapy-related complications. Relatively common outcomes with strong associations with therapeutic exposures, including cardiomyopathy, obesity, osteonecrosis, ototoxicity, and subsequent malignancies are discussed here. To develop a deeper understanding of the molecular underpinnings of therapy-related complications, comprehensive and near-complete collection of clinically annotated samples is critical. Methodologic issues such as study design, definition of the endpoints or phenotypes, identification of appropriate and adequately sized study population together with a reliable plan for collecting and maintaining high-quality DNA, and selection of an appropriate approach or platform for genotyping are also discussed. Understanding the etiopathogenetic pathways that lead to the morbidity is critical to developing targeted prevention and intervention strategies, optimizing risk-based health care of cancer survivors, thus minimizing chronic morbidities and improving quality of life.

Association between XPF polymorphisms and cancer risk: a meta-analysis

BACKGROUND

Xeroderma pigmentosum complementation group F (XPF or ERCC4) plays a key role in DNA repair that protects against genetic instability and carcinogenesis. A series of epidemiological studies have examined associations between XPF polymorphisms and cancer risk, but the findings remain inconclusive.

METHODOLOGY/PRINCIPAL FINDINGS

In this meta-analysis of 47,639 cancer cases and 51,915 controls, by searching three electronic databases (i.e., MEDLINE, EMBASE and CNKI), we summarized 43 case-control studies from 29 publications on four commonly studied polymorphisms of XPF (i.e., rs1800067, rs1799801, rs2020955 and rs744154), and we did not find statistical evidence of any significant association with overall cancer risk. However, in stratification analyses, we found a significant association of XPF-rs1799801 with a reduced cancer risk in Caucasian populations (4,845 cases and 5,556 controls; recessive model: OR=0.87, 95% CI=0.76-1.00, P=0.049, P=0.723 for heterogeneity test, I(2) =0). Further genotype-phenotype correlation analysis showed that the homozygous variant CC genotype carriers had higher XPF expression levels than that of the TT genotype carriers (Student's t test for a recessive model: P=0.046). No publication bias was found by using the funnel plot and Egger's test.

CONCLUSION

This meta-analysis suggests a lack of statistical evidence for the association between the four XPF SNPs and overall risk of cancers. However, XPF-rs1799801 may be associated with cancer risk in Caucasian populations, which needs to be further validated in single large, well-designed prospective studies.

Lack of association between XPG Asp1104His and XPF Arg415Gln polymorphism and breast cancer risk: a meta-analysis of case-control studies

The xeroderma pigmentosum group G (XPG or ERCC5) and group F (XPF or ERCC4) play an important role in DNA repair, and produce dual incision 3' and 5' to the damaged nucleotide fragment. Several polymorphisms in the XPF and XPG gene have been described, including the commonly occurring Asp1104His in XPG and Arg415Gln in XPF. The published data on the association between these polymorphisms and breast cancer remained controversial. This meta-analysis of literatures was performed to derive a more precise estimation of the relationship. A total of 17 studies were identified to the meta-analysis, including 5,235 cases and 5,685 controls for XPG Asp1104His (from ten studies) and 3,910 cases and 3,985 controls for XPF Arg415Gln (from seven studies). Overall, no significantly elevated breast cancer risk was found in all genetic models when all studies were pooled into the meta-analysis (for XPG Asp1104His Asp/His vs. Asp/Asp: OR 1.02, 95% CI 0.94-1.11; His/His vs. Asp/Asp: OR 0.96, 95% CI 0.83-1.11; dominant model: OR 1.01, 95% CI 0.94-1.09; and for XPF Arg415Gln Arg/Gln vs. Arg/Arg: OR 1.00, 95% CI 0.89-1.12; Gln/Gln vs. Arg/Arg: OR 2.40, 95% CI 0.62-9.22; dominant model: OR 1.03, 95% CI 0.90-1.18). In stratified analyses, we observed an overall OR of 5.20 (95% CI 2.08-12.95) for breast cancer developing risk in the Caucasian ethnicity, comparing Gln/Gln type to wild-type Arg/Arg for Arg415Gln polymorphism. In conclusion, this meta-analysis suggests that XPG Asp1104His polymorphism is not associated with increased breast cancer risk, and XPF Arg415Gln may be a low-penetrant risk factor in the Caucasian ethnicity for developing breast cancer.

Cancer mortality among women frequently exposed to radiographic examinations for spinal disorders

We studied cancer mortality in a cohort of 5,573 women with scoliosis and other spine disorders who were diagnosed between 1912 and 1965 and were exposed to frequent diagnostic X-ray procedures. Patients were identified from medical records in 14 orthopedic medical centers in the United States and followed for vital status and address through December 31, 2004, using publicly available regional, state and nationwide databases. Causes of death were obtained from death certificates or through linkage with the National Death Index (NDI). Statistical analyses included standardized mortality ratios (SMR = observed/expected) based on death rates for U.S. females and internal comparisons using Cox regression models with attained age as the time scale. Diagnostic radiation exposure was estimated from radiology files for over 137,000 procedures; estimated average cumulative radiation doses to the breast, lung, thyroid and bone marrow were 10.9, 4.1, 7.4 and 1.0 cGy, respectively. After a median follow-up period of 47 years, 1527 women died, including 355 from cancer. Cancer mortality was 8% higher than expected (95% CI = 0.97-1.20). Mortality from breast cancer was significantly elevated (SMR = 1.68; 95% CI: 1.38-2.02), whereas death rates from several other cancers were below expectation, in particular lung (SMR = 0.77), cervical (SMR = 0.31), and liver (SMR = 0.17). The excess relative risk (ERR) for breast cancer mortality increased significantly with 10-year lagged radiation dose to the breast (ERR/Gy = 3.9; 95% CI: 1.0-9.3).

Meta-analysis of two ERCC2 (XPD) polymorphisms, Asp312Asn and Lys751Gln, in breast cancer

The excision repair cross-complementing group 2 gene (ERCC2) plays a key role in DNA repair. Several polymorphisms in the ERCC2 gene have been described, including the commonly occurring Lys751Gln and Asp312Asn polymorphisms. Studies investigating the association of these polymorphisms with breast cancer risk produced controversial results. To evaluate these associations presented in diverse populations, we have conducted a meta-analysis based on 40 studies from 33 publications in PubMed which included analyses of Lys751Gln (14,545 cases, 15,352 controls) and Asp312Asn polymorphisms (16,254 cases, 14,006 controls). Overall findings of both polymorphisms have implicated null effects (OR = 1.01-1.03) when the analyses were limited to the statistically powerful (≥80%) studies. Although modestly increased statistically significant breast cancer risk was detected in the underpowered studies (≤80%), removal of outliers resulted in null associations. Ethnic stratification showed non-significant and relatively null associations for both polymorphisms with breast cancer risk for the overall Caucasians as well as North American and the European sub-populations. Although statistically increased and decreased risks were observed for the homogenous populations of African-Americans (Lys751Gln, OR 1.25, 95% CI 1.03-1.53, P = 0.03) and Asians (Asp312Asn, ORs: 0.53-0.55, P values: 0.02-0.03), respectively, this may be the result of small sample size. Analyses of the homogeneous adduct studies, with relatively large sample size, exhibited increased risk for Lys751Gln (OR 1.20, 95% CI (1.02-1.41), P = 0.03) and Asp312Asn (OR 1.17 95% CI 1.02-1.34, P = 0.03) under the dominant genetic model. In conclusion, our results suggest null associations of both polymorphisms in the overall and the Caucasian subgroups, although some effects can be suggested for relatively smaller minority studies. Increased risk effect was more visible when the adduct studies are considered, suggesting the role of these polymorphisms in the presence of exposure to DNA damaging agents.

Associations between XPD polymorphisms and risk of breast cancer: a meta-analysis

Studies on polymorphisms of Xeroderma Pigmentosum Group D Protein (XPD) and breast cancer risk are inconclusive. To elucidate the role of XPD genotypes, all available studies were considered in this meta-analysis. The study provided 11,362/10,622 cases/controls for XPD K751Q and 9010/9873 cases/controls for XPD D312N, respectively. Overall, no apparent effects of 751Q allele compared to 751K on breast cancer risk was found in all subjects [RE OR = 1.04, 95% confidence interval (CI) (0.97-1.10), P = 0.28]. Insignificant effects were also found under other genetic contrasts (homologous contrast, dominant model, and recessive model). However, the 751Q allele showed significantly increased risk in Caucasians [FE OR = 1.05, 95% CI (1.00-1.11), P = 0.035]. In addition, insignificant risk effects of D312N polymorphism on breast cancer susceptibility were observed in all subjects under any genetic contrast, but protective effects of 312NN genotype were observed under recessive model [P = 0.02, OR = 0.53, 95% CI (0.32, 0.90)] and homozygote contrast [P = 0.03, OR = 0.55; 95% CI (0.32, 0.96)] in Asians. In summary, our meta-analysis suggested 312N allele might act as a recessive allele in its association with breast cancer and the 751Q allele may play a plausible role in breast cancer development whereas the ethnic background should be carefully concerned in further studies.

DNA repair gene polymorphisms and risk of adult meningioma, glioma, and acoustic neuroma

Although the etiology of primary brain tumors is largely unknown, prior studies suggest that DNA repair polymorphisms may influence risk of glioma. Altered DNA repair is also likely to affect the risk of meningioma and acoustic neuroma, but these tumors have not been well studied. We estimated the risk of glioma (n = 362), meningioma (n = 134), and acoustic neuroma (n = 69) in non-Hispanic whites with respect to 36 single nucleotide polymorphisms from 26 genes involved in DNA repair in a hospital-based, case-control study conducted by the National Cancer Institute. We observed significantly increased risk of meningioma with the T variant of GLTSCR1 rs1035938 (OR(CT/TT) = 3.5; 95% confidence interval: 1.8-6.9; P(trend) .0006), which persisted after controlling for multiple comparisons (P = .019). Significantly increased meningioma risk was also observed for the minor allele variants of ERCC4 rs1800067 (P(trend) .01); MUTYH rs3219466 (P(trend) .02), and PCNA rs25406 (P(trend) .03). The NBN rs1805794 minor allele variant was associated with decreased meningioma risk (P(trend) .006). Risk of acoustic neuroma was increased for the ERCC2 rs1799793 (P(trend) .03) and ERCC5 rs17655 (P(trend) .05) variants and decreased for the PARP1 rs1136410 (P(trend) .03). Decreased glioma risk was observed with the XRCC1 rs1799782 variant (P(trend) .04). Our results suggest that common DNA repair variants may affect the risk of adult brain tumors, especially meningioma.