Polymorphisms in the DNA repair genes XRCC1, APEX1, XRCC3 and NBS1, and the risk for lung cancer in never- and ever-smokers

Exploring homologous recombination repair and base excision repair pathway genes for possible diagnostic markers in hematologic malignancies

Hematologic malignancies (HMs) are a collection of malignant transformations, originating from the cells in the bone marrow and lymphoid organs. HMs comprise three main types; leukemia, lymphoma, and multiple myeloma. Globally, HMS accounts for approximately 10% of newly diagnosed cancer. DNA repair pathways defend the cells from recurrent DNA damage. Defective DNA repair mechanisms such as homologous recombination repair (HRR), nucleotide excision repair (NER), and base excision repair (BER) pathways may lead to genomic instability, which initiates HM progression and carcinogenesis. Expression deregulation of HRR, NER, and BER has been investigated in various malignancies. However, no studies have been reported to assess the differential expression of selected DNA repair genes combinedly in HMs. The present study was designed to assess the differential expression of HRR and BER pathway genes including RAD51, XRCC2, XRCC3, APEX1, FEN1, PARP1, and XRCC1 in blood cancer patients to highlight their significance as diagnostic/ prognostic marker in hematological malignancies. The study cohort comprised of 210 blood cancer patients along with an equal number of controls. For expression analysis, q-RT PCR was performed. DNA damage was measured in blood cancer patients and controls using the comet assay and LORD Q-assay. Data analysis showed significant downregulation of selected genes in blood cancer patients compared to healthy controls. To check the diagnostic value of selected genes, the Area under curve (AUC) was calculated and 0.879 AUC was observed for RAD51 (p < 0.0001) and 0.830 (p < 0.0001) for APEX1. Kaplan-Meier analysis showed that downregulation of RAD51 (p < 0.0001), XRCC3 (p < 0.02), and APEX1 (p < 0.0001) was found to be associated with a significant decrease in survival of blood cancer patients. Cox regression analysis showed that deregulation of RAD51 (p < 0.0001), XRCC2 (p < 0.02), XRCC3 (p < 0.003), and APEX1 (p < 0.00001) was found to be associated with the poor prognosis of blood cancer patients. Comet assay showed an increased number of comets in blood cancer patients compared to controls. These results are confirmed by performing the LORD q-assay and an increased frequency of lesions/Kb was observed in selected genes in cancer patients compared to controls. Our results showed significant downregulation of RAD51, XRCC2, XRCC3, APEX1, FEN1, PARP1, and XRCC1 genes with increased DNA damage in blood cancer patients. The findings of the current research suggested that deregulated expression of HRR and BER pathway genes can act as a diagnostic/prognostic marker in hematologic malignancies.

Potential Impact of Cancer Susceptibility Genes on Lung Cancer Metastasis

Background. Studies of prognosis-related molecular markers are an important tool to uncover the mechanism of tumour metastasis. Cancer susceptibility gene testing is an important tool for genetic counselling of cancer risk. However, the impact of lung cancer susceptibility genes (LCSGs) on lung cancer metastasis and prognosis has not been well studied. Methods. The list of lung cancer susceptibility genes was retrospectively analysed and updated. After expression profiling and functional analysis, LCSG-based signatures for prognosis were identified by Cox regression and LASSO regression analyses. For translational purposes, nomograms integrating LCSGs and clinical characteristics were constructed. Results. A total of 301 LCSGs were employed for modelling. For lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC), 10-gene and 7-gene signatures were created and independently validated. The LCSG-based risk score could stratify LUAD survival (univariate: hazard ratio $\left(\text{HR}\right)=1.076$ , 95% confidence interval $\left(\text{CI}\right)=1.049$ –1.103, $P<0.001$ ; multivariate: $\text{HR}=1.066$ , 95% $\text{CI}=1.037$ –1.095, $P<0.001$ ) and LUSC survival (univariate: $\text{HR}=1.149$ , 95% $\text{CI}=1.066$ −1.239, $P<0.001$ ; multivariate: $\text{HR}=1.129$ , 95% $\text{CI}=1.038$ −1.228, $P=0.005$ ). One of the processes affected by differentially expressed genes in both LUAD and LUSC was the negative regulation of epithelial cell differentiation. Conclusions. Overall, novel LCSG-based gene signatures for LUAD and LUSC were constructed. These findings could expand the understanding of the impact of LCSG expression on cancer metastasis and prognosis.

Radon, Tobacco Exposure and Non-Small Cell Lung Cancer Risk Related to BER and NER Genetic Polymorphisms

INTRODUCTION

Tobacco consumption and radon exposure are considered the first and second most common causes of lung cancer, respectively. The aim of this study was to analyze both whether selected genetic polymorphisms in loci that are in DNA repair pathways, are related to non-small-cell lung cancer (NSCLC) and whether they may modulate the association between residential radon exposure and lung cancer in both smokers and never smokers.

METHODS

A multicentre, hospital-based, case-control study with 826 cases and 1201 controls was designed in a radon-prone area. Genotyping was determined in whole blood and residential radon exposure was measured in participants' dwellings.

RESULTS

Attending to tobacco exposure, the variant in the gene NBN (rs1805794) was associated with lung cancer in never smokers (OR 2.72; 95%1.44-5.2) and heavy smokers (OR 3.04; 95%CI 1.21-7.69). The polymorphism with the highest lung cancer association was OGG1 (rs125701), showing an OR of 8.04 (95%CI 1.64-58.29) for its homozygous variant genotype in heavy smokers. Attending to indoor radon exposure (>200Bq/m3), rs1452584, for its homozygous variant genotype, showed the highest association (OR 3.04 (95%CI 1.15-8.48).

CONCLUSION

The genes analyzed seem to have no association with the fully adjusted model, but they might modulate lung cancer association when different categories of tobacco consumption are considered (i.e. heavy smokers). This association may similarly be elevated for those individuals having high indoor radon exposures, though at a minor extent.

A Novel Signature for Predicting Prognosis of Smoking-Related Squamous Cell Carcinoma

Tobacco smoking is an established risk factor for squamous cell carcinoma (SCC). We obtained smoking-related SCC, including cervical SCC (CSCC), esophageal SCC (ESCC), head and neck SCC (HNSC), and lung SCC (LUSC), from The Cancer Genome Atlas (TCGA) database to investigate the association between smoking status (reformed and current smoking) and prognosis. We found that reformed smokers had a better prognosis than current smokers in CSCC (p = 0.003), HNSC (p = 0.019), and LUSC (p < 0.01) cohorts. Then, we selected LUSC cohorts as the training cohort and other SCC cohorts as the test cohorts. Function analysis revealed that homologous recombination (HR) was the most significant pathway involved in smoking-induced LUSC. Moreover, the effect of cross-talk between the smoking status and HR deficiency (HRD) on the prognosis was further evaluated, revealing that quitting smoking with high HRD scores could significantly improve patients’ prognosis (p < 0.01). To improve prognosis prediction and more effectively screen suitable populations for platinum drugs and poly-ADP-ribose polymerase (PARP) inhibitors, we constructed a risk score model using smoking- and HRD-related genes in LUSC. The risk score model had high power for predicting 2-, 3-, and 5-year survival (p < 0.01, AUC = 0.67, 0.66, and 0.66). In addition, the risk scores were an independent risk factor for LUSC (HR = 2.34, 95%CI = 1.70–3.23). The practical nomogram was also built using the risk score, smoking status, and other clinical information with a good c-index (0.72, 95%CI = 0.70–0.74). Finally, we used other TCGA SCC cohorts to confirm the reliability and validity of the risk score model (p < 0.01 and AUC > 0.6 at 2, 3, and 5 years in CSCC and HNSC cohorts). In conclusion, the present study suggested that smoking cessation should be a part of smoking-related SCC treatment, and also provided a risk score model to predict prognosis and improve the effectiveness of screening the platinum/PARP population.

Mutation Spectra of the MRN (MRE11, RAD50, NBS1/NBN) Break Sensor in Cancer Cells

Simple Summary

A DNA double strand break cuts a chromosome in two and is one of the most dangerous forms of DNA damage. Improper repair can lead to various chromosomal re-arrangements that have been detected in almost all cancer cells. A complex of three proteins (MRE11, RAD50, NBS1 or NBN) detects chromosome breaks and orchestrates repair processes. Mutations in these “break sensor” genes have been described in a multitude of cancers. Here, we provide a comprehensive analysis of reported mutations from data deposited on the Catalogue of Somatic Mutations in Cancer (COSMIC) archive. We also undertake an evolutionary analysis of these genes with the aim to understand whether these mutations preferentially accumulate in conserved residues. Interestingly, we find that mutations are overrepresented in evolutionarily conserved residues of RAD50 and NBS1/NBN but not MRE11.

Abstract

The MRN complex (MRE11, RAD50, NBS1/NBN) is a DNA double strand break sensor in eukaryotes. The complex directly participates in, or coordinates, several activities at the break such as DNA resection, activation of the DNA damage checkpoint, chromatin remodeling and recruitment of the repair machinery. Mutations in components of the MRN complex have been described in cancer cells for several decades. Using the Catalogue of Somatic Mutations in Cancer (COSMIC) database, we characterized all the reported MRN mutations. This analysis revealed several hotspot frameshift mutations in all three genes that introduce premature stop codons and truncate large regions of the C-termini. We also found through evolutionary analyses that COSMIC mutations are enriched in conserved residues of NBS1/NBN and RAD50 but not in MRE11. Given that all three genes are important to carcinogenesis, we propose these differential enrichment patterns may reflect a more severe pleiotropic role for MRE11.

Association between family history of lung cancer and lung cancer risk: a systematic review and meta-analysis

BACKGROUND

Familial risk of lung cancer has been widely studied but the effects of sociodemographic factors and geographical regions are largely unknown.

METHODS

PubMed and Embase were systematically searched until 1^st October 2019. A total of 84 articles were identified and (19 cohort and 66 case control studies) included in this systematic review and meta-analysis. Pooled summary estimates and 95% confidence intervals were estimated, and the analysis was stratified by sociodemographic factors and geographical regions.

RESULTS

Geographical regions, sex, age of proband, smoking status, type of first-degree relatives, number of affected relatives, and early onset of lung cancer in affected relatives were significant determinants of familial risk of lung cancer. Higher risk of familial lung cancer was found among Asians as compared to non-Asians, younger individuals (age≤50) as compared with older individuals (age>50), individuals with ≥2 affected relatives as compared with individuals with one affected relative, ever-smokers as compared with never-smokers, Asian females as compared with Western females, and never-smokers in Asia as compared with never-smokers in the West.

CONCLUSIONS

Familial risk of lung cancer is influenced by both genetic and environmental factors. Future studies should control for environmental factors such as air pollution and environmental tobacco smoke which are prevalent in Asia.

Polymorphisms of XRCC3 and XRCC7 and Colorectal Cancer Risk in Khorasan Razavi Province, Iran

Background: Colorectal cancer (CRC) is highly prevalent cancer, which should be genetically studied among different peoples of the world. Objective: The aim of this study was to evaluate the effect of XRCC3T241M, XRCC3 A17893G and, for the first time, XRCC7 I3434T polymorphisms on CRC risk in Khorasan Razavi Province, Iran. Materials and Methods: In this case-control study, 180 patients with CRC and 160 sex- and age-matched healthy controls were studied. Genotypes were determined by RFLP-PCR and ARMS-PCR. Results: The incidence of CRC was observed to be significantly more in a heterozygous XRCC3 C/T genotype than in the CC genotype (OR 2.210, 95% CI 1.073-4.548, p=0.030). In the case of the XRCC7 I3434T polymorphism, CRC risk was significantly (4.3 fold) higher in I/T+T/T variant subjects compared to the I/I genotype (OR 4.394, 95% CI 2.721-7.096, p=0.000). Moreover, the XRCC3 A17893G polymorphism did not correlate with CRC. In addition, there was no significant difference between the distribution of genotypes of the three studied polymorphisms with demographic and clinicopathological features in the CRC patients. Conclusion: Polymorphisms of XRRC3 and XRCC7 genes are involved in CRC and should be considered as a risk factor.

Cytogenetic effects of radiation and genetic polymorphisms of the XRCC1 and XRCC3 repair genes in industrial radiographers

Different types of DNA damages caused by ionizing radiation may enhance the cancer risk in exposed individuals. Inherited variations in DNA repair genes cause the inter-individual variability in response to ionizing radiation. The purpose of this study was to determine the association between single nucleotide polymorphism (SNP) of two important DNA repair genes (XRCC1 R399Q and XRCC3 T241M) and the level of DNA damage investigated by micronucleus (MN) frequency in peripheral blood lymphocytes of 120 industrial radiographers (IR) and 120 non-exposed control individuals. The frequencies of MN and nucleoplasmic bridges were significantly higher in the IR group than in the control group (33.83 ± 11.96 vs. 7.47 ± 2.96, p < 0.0001 and 1.69 ± 1.86 vs. 0.12 ± 0.33, p < 0.0001). MN frequencies in the IR group were associated with the cumulative radiation doses (p < 0.0001, r = 0.58 for last 1 year of exposure and p < 0.0001, r = 0.67 for last 5 years of exposure). Polymorphism of XRCC3 T241M was associated with higher MN frequencies in the IR group. However, the same result was not observed between XRCC3 SNP and MN frequency in the control group. Consequently, XRCC3 241Met alleles may cause the increased DNA damage in the industrial radiographers.

Effect of NBS1 Gene Polymorphism on the Risk of Cervix Carcinoma in a Northern Indian Population

Cervical cancer is one of the most common neoplastic diseases affecting women, with a worldwide incidence of almost half a million cases. A history of smoking and use of oral contraceptives have been confirmed to be risk factors for cervical cancer. Genetic susceptibility and immune response, especially impaired cellular immune response, may well be related to the development of cervical cancer. NBS1 is one of the key proteins participating in the recognition and repair of double-strand breaks that may lead to genomic instability and cancer if unrepaired. The objective of the present study was therefore to investigate NBS1 Glu185Gln gene polymorphisms and the risk of cervix cancer in a northern Indian population. We found that passive smokers having particular NBS1 genotypes (Glu/Gln, Gln/Gln or Glu/Gln + Gln/Gln) have an increased risk of developing cervix cancer (OR 5.21, p=0.000001; OR 4.60, p=0.001; OR 5.10, p=0.0000009, respectively). The risk was increased 2.4-fold in oral contraceptive users with a Glu/Gln genotype. We conclude that the risk of cervical cancer is increased in passive smokers and in users of oral contraceptives with certain NBS1 genotypes.

Modulation of Colorectal Cancer Risk by Polymorphisms in 51Gln/His, 64Ile/Val, and 148Asp/Glu of APEX Gene; 23Gly/Ala of XPA Gene; and 689Ser/Arg of ERCC4 Gene

Polymorphisms in DNA repair genes may affect the activity of the BER (base excision repair) and NER (nucleotide excision repair) systems. Using DNA isolated from blood taken from patients (n = 312) and a control group (n = 320) with CRC, we have analyzed the polymorphisms of selected DNA repair genes and we have demonstrated that genotypes 51Gln/His and 148Asp/Glu of APEX gene and 23Gly/Ala of XPA gene may increase the risk of colorectal cancer. At the same time analyzing the gene-gene interactions, we suggest the thesis that the main factor to be considered when analyzing the impact of polymorphisms on the risk of malignant transformation should be intergenic interactions. Moreover, we are suggesting that some polymorphisms may have impact not only on the malignant transformation but also on the stage of the tumor.

The relationship of single-strand breaks in DNA to breast cancer risk and to tissue concentrations of oestrogens

CONTEXT

Clinical study of breast cancer patients in Chicago, IL, USA.

OBJECTIVE

Ascertain the utility of measurements of single-strand breaks (SSB) in DNA for assessment of breast cancer risk.

METHODS

Fine-needle aspirates of the breast, SSB by nick translation, percent breast density (PBD), Gail model risk, cumulative methylation index (CMI), enzymes of DNA repair and tissue antioxidants.

RESULTS

DNA repair enzymes and 4-hydroxyestradiol were negatively associated with SSB; CMI and PBD were positively associated.

CONCLUSIONS

Quantitative measurement of SSBs by this procedure indicates the relative number of SSBs and is related to promoter methylation, antioxidant availability and percent breast density.

XRCC3 Thr241Met Polymorphism is not Associated with Lung Cancer Risk in a Romanian Population

BACKGROUND AND AIMS

Deoxyribonucleic Acid (DNA) repair mechanisms play a critical role in protecting the cellular genome against carcinogens. X-ray cross-complementing gene 3 (XRCC3) is involved in DNA repair and therefore certain genetic polymorphisms that occur in DNA repair genes may affect the ability to repair DNA defects and may represent a risk factor in carcinogenesis. The purpose of our study was to investigate the association between XRCC3 gene substitution of Threonine with Methionine in codon 241 of XRCC3 gene (Thr241Met) polymorphism and the risk of lung cancer, in a Romanian population.

METHODS

We recruited 93 healthy controls and 85 patients with lung cancer, all smokers. Thr241Met, XRCC3 gene genotyping was determined by multiplex Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP).

RESULTS

Statistical analysis (OR, recessive model), did not revealed an increased risk for lung cancer, for the variant 241Met allele and Thr241Met genotypes (p=0.138, OR=0.634, CI=0.348-1.157; p=0.023, OR=0.257, CI=0.085-6.824). Also, there were no positive statistical associations between Thr241Met polymorphism of XRCC3 gene, gender, tobacco and various histopathological tumor type of lung cancer.

CONCLUSION

In conclusion, the results of the study suggest that the XRCC3 gene Thr241Met polymorphism is not associated with an increased risk for the development of lung cancer in this Romanian group.

Genetic Variation in the 3'-Untranslated Region of NBN Gene Is Associated with Gastric Cancer Risk in a Chinese Population

NBN plays a crucial role in carcinogenesis as a core component for both homologous recombination (HR) and non-homologous end-joining (NHEJ) DNA double-strand breaks (DSBs) repair pathways. Genetic variants in the NBN gene have been associated with multiple cancers risk, suggesting pleiotropic effect on cancer. We hypothesized that genetic variants in the NBN gene may modify the risk of gastric cancer. To test this hypothesis, we evaluated the association between four potentially functional single nucleotide polymorphisms in NBN and gastric cancer risk in a case-control study of 1,140 gastric cancer cases and 1,547 controls in a Chinese population. We found that the A allele of rs10464867 (G>A) was significantly associated with a decreased risk of gastric cancer (odds ratio [OR] = 0.81, 95% confidence interval [95% CI] = 0.71-0.94; P = 4.71×10-3). Furthermore, the association between A allele of rs10464867 and decreased risk of gastric cancer was more significantly in elder individuals (per-allele OR = 0.72[0.59-0.88], P = 1.07×10-3), and male individuals (per-allele OR = 0.73[0.62-0.87], P = 3.68×10-4). We further conducted a haplotype analysis and identified that the NBN Ars10464867Grs14448Grs1063053 haplotype conferred stronger protective effect on gastric cancer (OR = 0.76[0.65-0.89], P = 6.39×10-4). In summary, these findings indicate that genetic variants at NBN gene may contribute to gastric cancer susceptibility and may further advance our understanding of NBN gene in cancer development.

Associations between NBS1 Polymorphisms and Colorectal Cancer in Chinese Population

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

The functional polymorphism of NBS1 p.Glu185Gln is associated with an increased risk of lung cancer in Chinese populations: case-control and a meta-analysis

NBS1 plays pivotal roles in maintaining genomic stability and cancer development. The exon variant rs1805794G>C (p.Glu185Gln) of NBS1 has been frequently studied in several association studies. However, the results were conflicting. Also, the function of this variant has never been well studied. In the current study, we performed a two centers case-control study and function assays to investigate the effect of the variant rs1805794G>C on lung cancer risk in Chinese, and a meta-analysis to summarize the data on the association between rs1805794G>C and cancer risk. We found that compared with the rs1805794GG genotype, the C genotypes (CG/CC) conferred a significantly increased risk of lung cancer in Chinese (OR=1.40, 95% CI=1.21-1.62) and interacted with medical ionizing radiation exposure on increasing cancer risk (Pinteraction=0.015). The lymphocyte cells from the C genotype individuals developed more chromatid breaks than those from the GG genotype carriers after the X-ray radiation (P=0.036). Moreover, the rs1805794C allele encoding p.185Gln attenuated NBS1's ability to repair DNA damage as the cell lines transfected with NBS1 cDNA expression vector carrying rs1805794C allele had significantly higher DNA breaks than those transfected with NBS1 cDNA expression vector carrying rs1805794G allele (P<0.05). The meta-analysis further confirmed the association between the variant rs1805794G>C and lung cancer risk, that compared with the GG genotype, the carriers of C genotypes had a 1.30-fold risk of cancer (95% CI=1.14-1.49, P=8.49×10(-5)). These findings suggest that the rs1805794G>C of NBS1 may be a functional genetic biomarker for lung cancer.

NBN and XRCC3 genetic variants in childhood acute lymphoblastic leukaemia

Nibrin and DNA repair protein XRCC3 are involved in DNA double-strand break repair. We genotyped seven tagging SNPs in these genes (rs1805794, rs709816; rs1063054; rs7141928, rs1799794, rs861530, rs861539) with the aim to analyse their association with acute lymphoblastic leukaemia (ALL), a disease, that is characterised by elevated genetic instability. Study consisted of 460 paediatric ALL cases and 552 healthy controls. For selection of DNA sequence variants we employed SNP-tagging approach, incorporating the HAPMAP CEU reference panel data. We did not find association of analysed and tagged SNPs and derived haplotypes with the ALL risk thus did not confirm the hypothesis that analysed DNA recombination repair variants account for increased susceptibility to ALL.

Human AP endonuclease 1: a potential marker for the prediction of environmental carcinogenesis risk

Human apurinic/apyrimidinic endonuclease 1 (APE1) functions mainly in DNA repair as an enzyme removing AP sites and in redox signaling as a coactivator of various transcription factors. Based on these multifunctions of APE1 within cells, numerous studies have reported that the alteration of APE1 could be a crucial factor in development of human diseases such as cancer and neurodegeneration. In fact, the study on the combination of an individual's genetic make-up with environmental factors (gene-environment interaction) is of great importance to understand the development of diseases, especially lethal diseases including cancer. Recent reports have suggested that the human carcinogenic risk following exposure to environmental toxicants is affected by APE1 alterations in terms of gene-environment interactions. In this review, we initially outline the critical APE1 functions in the various intracellular mechanisms including DNA repair and redox regulation and its roles in human diseases. Several findings demonstrate that the change in expression and activity as well as genetic variability of APE1 caused by environmental chemical (e.g., heavy metals and cigarette smoke) and physical carcinogens (ultraviolet and ionizing radiation) is likely associated with various cancers. These enable us to ultimately suggest APE1 as a vital marker for the prediction of environmental carcinogenesis risk.

The codon 399 Arg/Gln XRCC1 polymorphism is associated with lung cancer in Indians

BACKGROUND

The XRCC1 (X-ray repair cross complimenting group-I) gene in BER (base excision repair) pathway is essential for DNA repair process. Polymorphisms in this gene are associated with variations in the repair efficiency which might predispose individuals to development of various cancers. Two variants of XRCC1gene (at codon 399), Gln/Gln and Arg/Gln, have been shown to be related to lowered DNA repair capacity and increased genomic instability in multiple studies. Hence our investigation focused on genotyping these variants to correlate with other multiple risk factors in lung cancer (NSCLC) patients since we hypothesized that these variants of the XRCC1 gene might influence disease susceptibility.

MATERIALS AND METHODS

We examined the frequency of the polymorphism in one hundred cases and an almost equal number of controls after recording their demographics with a structured questionnaire. Genomic DNA from blood samples was extracted for PCR studies, followed by RFLP to determine the variants. The significance of the data was statistically analyzed.

RESULTS

The three genotypes in cases and controls were Arg/Arg (40% and 54.45%); Gln/Gln (19% and 9.90%), and Arg/Gln (41.0% and 35.64%) respectively. Among these 3 genotypes, we found Gln/Gln and Arg/Gln to show association with lung cancer. Correlating these genotypes with several parameters, we also found that these two variants were associated with risk in males (p<0.05) and with smoking habits (p<0.05). In females Arg/Gln genotype showed association with stage of the disease (p=0.04). This is the first report in South Indian scenario where Arg399Gln genotypes were found to be associated with stage of the disease in females.

CONCLUSIONS

It is concluded that XRCC1 genotypes Gln/Gln and Arg/Gln may influence cancer susceptibility in patients with smoking habits and these functional SNPs in XRCC1 gene may act as attractive candidate biomarkers in lung cancer for diagnosis and prognosis.

The (CCTTT)n microsatellite polymorphism in the NOS2 gene may influence lung cancer risk and long-term survival, especially in non-smokers

We analyzed the associations of the NOS2 (CCTTT)n promoter polymorphism to lung cancer risk and tumor histology in smokers and non-smokers. We also investigated lung cancer long-term survival in relation to the polymorphism, smoking data, histology, age at diagnosis, and gender. One hundred eighty-five lung-cancer patients and 164 matched controls, where non-smokers were enriched among the lung cancer cases, were genotyped by fragment analysis and sequencing. Genotypes were combined with information on histology, patient smoking status, and cancer-specific death, using a 20-year follow-up. We divided the (CCTTT)n alleles into short (n ≤ 10), intermediate (n = 11-12), and long (n ≥ 13). Patients homozygous for short repeats had significantly increased risk of lung cancer (p = 0.030) compared to carriers of two long alleles (LL). Lack of long allele was associated with a significantly increased lung cancer risk overall (p = 0.011), especially among non-smokers (p = 0.001). A significantly higher lung cancer survival was seen in non-smokers compared to smokers (p = 0.046) and in low-dose smokers compared to high-dose smokers at the time of diagnosis (p = 0.028). Moreover, non-smoking patients with squamous cell carcinoma (p = 0.015) or adenocarcinoma (p = 0.024) showed a significantly lower survival compared to other lung carcinomas. Nitric oxide can induce proliferation as well as apoptosis depending on cellular context. Our results suggest that the (CCTTT)n NOS2 microsatellite may influence the risk of developing lung cancer, especially in non-smokers, possibly by affecting intracellular nitric oxide levels. Our results also give additional information about the yet poorly understood etiological and prognostic differences between lung cancer in non-smokers and smokers.

NBN Gene Polymorphisms and Cancer Susceptibility: A Systemic Review

The relationship between DNA repair failure and cancer is well established as in the case of rare, high penetrant genes in high cancer risk families. Beside this, in the last two decades, several studies have investigated a possible association between low penetrant polymorphic variants in genes devoted to DNA repair pathways and risk for developing cancer. This relationship would be also supported by the observation that DNA repair processes may be modulated by sequence variants in DNA repair genes, leading to susceptibility to environmental carcinogens. In this framework, the aim of this review is to provide the reader with the state of the art on the association between common genetic variants and cancer risk, limiting the attention to single nucleotide polymorphisms (SNPs) of the NBN gene and providing the various odd ratios (ORs). In this respect, the NBN protein, together with MRE11 and RAD50, is part of the MRN complex which is a central player in the very early steps of sensing and processing of DNA double-strand breaks (DSBs), in telomere maintenance, in cell cycle control, and in genomic integrity in general. So far, many papers were devoted to ascertain possible association between common synonymous and non-synonymous NBN gene polymorphisms and increased cancer risk. However, the results still remain inconsistent and inconclusive also in meta-analysis studies for the most investigated E185Q NBN miscoding variant.

Tobacco smoking, NBS1 polymorphisms, and survival in lung and upper aerodigestive tract cancers with semi-Bayes adjustment for hazard ratio variation

PURPOSE

Although single nucleotide polymorphisms (SNPs) of NBS1 have been associated with susceptibility to lung and upper aerodigestive tract (UADT) cancers, their relations to cancer survival and measures of effect are largely unknown.

METHODS

Using follow-up data from 611 lung cancer cases and 601 UADT cancer cases from a population-based case-control study in Los Angeles, we prospectively evaluated associations of tobacco smoking and 5 NBS1 SNPs with all-cause mortality. Mortality data were obtained from the Social Security Death Index. We used Cox regression to estimate adjusted hazard ratios (HR) for main effects and ratios of hazard ratios (RHR) derived from product terms to assess hazard ratio variations by each SNP. Bayesian methods were used to account for multiple comparisons.

RESULTS

We observed 406 (66 %) deaths in lung cancer cases and 247 (41 %) deaths in UADT cancer cases with median survival of 1.43 and 1.72 years, respectively. Ever tobacco smoking was positively associated with mortality for both cancers. We observed an upward dose-response association between smoking pack-years and mortality in UADT squamous cell carcinoma. The adjusted HR relating smoking to mortality in non-small cell lung cancer (NSCLC) was greater for cases with the GG genotype of NBS1 rs1061302 than for cases with AA/AG genotypes (semi-Bayes adjusted RHR = 1.97; 95 % limits = 1.14, 3.41).

CONCLUSIONS

A history of tobacco smoking at cancer diagnosis was associated with mortality among patients with lung cancer or UADT squamous cell carcinoma. The HR relating smoking to mortality appeared to vary with the NBS1 rs1061302 genotype among NSCLC cases.

XRCC3 Thr241Met is associated with response to platinum-based chemotherapy but not survival in advanced non-small cell lung cancer

Background

A lot of studies have investigated the correlation between x-ray repair cross-complementing group 3 (XRCC3) Thr241Met polymorphism and clinical outcomes in non-small cell cancer (NSCLC), while the conclusion is still conflicting.

Materials and Methods

We conducted this meta-analysis to evaluate the predictive value of XRCC3 Thr241Met polymorphism on response and overall survival of patients with NSCLC. Pooled odds ratios (ORs) and hazard ratios (HRs) and corresponding 95% confidence intervals (95% CIs) were used to estimate the association strength.

Results

A total of 14 eligible studies with 2828 patients were identified according to our inclusion criteria. Meta-analysis results showed that carriers of the variant 241Met allele were significantly associated with good response, compared with those harboring the wild 241Thr allele (Met vs. Thr, OR = 1.453, 95% CI: 1.116–1.892, P_{heterogeneity} = 0.968 and ThrMet+MetMet vs. ThrThr, OR = 1.476, 95% CI: 1.087–2.004, P_{heterogeneity} = 0.696). This significant association was observed in Caucasian population but not in Asian population. On the other hand, there was no significant association of XRCC3 Thr241Met polymorphism with survival (ThrMet+MetMet vs. ThrThr, HR = 1.082, 95% CI: 0.929–1.261, P_{heterogeneity} = 0.564), and there was no difference between Asian and Caucasian population.

Conclusions

These findings suggest a predictive role of XRCC3 Thr241Met polymorphism on response to platinum-based chemotherapy in patients with advanced NSCLC. Additionally, we first report that the XRCC3 Thr241Met polymorphism is associated with response to platinum-based chemotherapy and highlights the prognostic value of the XRCC3 Thr241Met polymorphism.

NBS1 Glu185Gln polymorphism and cancer risk: update on current evidence

A number of studies have investigated the association between NBS1 Glu185Gln (rs1805794, E185Q) polymorphism and cancer risk, but the results remained controversial. Previous meta-analysis found a borderline significant impact of this polymorphism on cancer risk; however, the result might be relatively unreliable due to absence of numerous newly published studies. Thus, we conducted an updated meta-analysis. A systematic search was performed in PubMed and Embase databases until April 9, 2013. The odds ratios were pooled by the fixed-effects/random-effects model in STATA 12.0 software. As a result, a total of 48 case-control studies with 17,159 cases and 22,002 controls were included. No significant association was detected between the Glu185Gln polymorphism and overall cancer risk. As to subgroup analysis by cancer site, the results showed that this polymorphism could increase the risk for leukemia and nasopharyngeal cancer. Notably, the Glu185Gln polymorphism was found to be related to increased risk for urinary system cancer, but decreased risk for digestive system cancer. No significant associations were obtained for other subgroup analyses such as ethnicity, sample size and smoking status. In conclusion, current evidence did not suggest that the NBS1 Glu185Gln polymorphism was associated with overall cancer risk, but this polymorphism might contribute to the risk for some specific cancer sites due to potential different mechanisms. More well-designed studies are imperative to identify the exact function of this polymorphism in carcinogenesis.

Association between XRCC1 and XRCC3 polymorphisms with lung cancer risk: a meta-analysis from case-control studies

Many studies have reported the association of X-ray repair cross-complementing group 1 (XRCC1) Arg399Gln, Arg194Trp, Arg280His, −77T>C, and X-ray repair cross-complementing group 3 (XRCC3) T241M polymorphisms with lung cancer risk, but the results remained controversial. Hence, we performed a meta-analysis to investigate the association between lung cancer risk and XRCC1 Arg399Gln (14,156 cases and 16,667 controls from 41 studies), Arg194Trp (7,426 cases and 9,603 controls from 23 studies), Arg280His (6,211 cases and 6,763 controls from 16 studies), −77T>C (2,487 cases and 2,576 controls from 5 studies), and XRCC3 T241M (8,560 cases and 11,557 controls from 19 studies) in different inheritance models. We found that −77T>C polymorphism was associated with increased lung cancer risk (dominant model: odds ration [OR] = 1.45, 95% confidence interval [CI] = 1.27–1.66, recessive model: OR = 1.73, 95% CI = 1.14–2.62, additive model: OR = 1.91, 95% CI = 1.24–1.94) when all the eligible studies were pooled into the meta-analysis. In the stratified and sensitive analyses, significantly decreased lung cancer risk was observed in overall analysis (dominant model: OR = 0.83, 95% CI = 0.78–0.89; recessive model: OR = 0.90, 95% CI = 0.81–1.00; additive model: OR = 0.82, 95% CI = 0.74–0.92), Caucasians (dominant model: OR = 0.82, 95% CI = 0.76–0.87; recessive model: OR = 0.89, 95% CI = 0.80–0.99; additive model: OR = 0.81, 95% CI = 0.73–0.91), and hospital-based controls (dominant model: OR = 0.81, 95% CI = 0.76–0.88; recessive model: OR = 0.89, 95% CI = 0.79–1.00; additive model: OR = 0.80, 95% CI = 0.71–0.90) for XRCC3 T241M. In conclusion, this meta-analysis indicates that XRCC1 −77T>C shows an increased lung cancer risk and XRCC3 T241M polymorphism is associated with decreased lung cancer risk, especially in Caucasians.

The joint effect of hOGG1, APE1, and ADPRT polymorphisms and cooking oil fumes on the risk of lung adenocarcinoma in Chinese non-smoking females

Background

The human 8-oxoguanine DNA glycosylase 1 (hOGG1), apurinic/apyrimidinic endonuclease 1 (APE1), and adenosine diphosphate ribosyl transferase (ADPRT) genes play an important role in the DNA base excision repair pathway. Single nucleotide polymorphisms (SNPs) in critical genes are suspected to be associated with the risk of lung cancer. This study aimed to identify the association between the polymorphisms of hOGG1 Ser326Cys, APE1 Asp148Glu, and ADPRT Val762Ala, and the risk of lung adenocarcinoma in the non-smoking female population, and investigated the interaction between genetic polymorphisms and environmental exposure in lung adenocarcinoma.

Methods

We performed a hospital-based case-control study, including 410 lung adenocarcinoma patients and 410 cancer-free hospital control subjects who were matched for age. Each case and control was interviewed to collect information by well-trained interviewers. A total of 10 ml of venous blood was collected for genotype testing. Three polymorphisms were analyzed by the polymerase chain reaction-restriction fragment length polymorphism technique.

Results

We found that individuals who were homozygous for the variant hOGG1 326Cys/Cys showed a significantly increased risk of lung adenocarcinoma (OR = 1.54; 95% CI: 1.01–2.36; P = 0.045). When the combined effect of variant alleles was analyzed, we found an increased OR of 1.89 (95% CI: 1.24–2.88, P = 0.003) for lung adenocarcinoma individuals with more than one homozygous variant allele. In stratified analyses, we found that the OR for the gene-environment interaction between Ser/Cys and Cys/Cys genotypes of hOGG1 codon 326 and cooking oil fumes for the risk of lung adenocarcinoma was 1.37 (95% CI: 0.77–2.44; P = 0.279) and 2.79 (95% CI: 1.50–5.18; P = 0.001), respectively.

Conclusions

The hOGG1 Ser326Cys polymorphism might be associated with the risk of lung adenocarcinoma in Chinese non-smoking females. Furthermore, there is a significant gene-environment association between cooking oil fumes and hOGG1 326 Cys/Cys genotype in lung adenocarcinoma among female non-smokers.

Association of XRCC3 and XRCC4 gene polymorphisms, family history of cancer and tobacco smoking with non-small-cell lung cancer in a Chinese population: a case-control study

Single-nucleotide polymorphisms (SNPs) of DNA repair genes have been reported to modify cancer risk. This study aimed to determine SNPs of the DNA repair genes X-ray repair cross-complementing group 3 (XRCC3) and X-ray cross-complementing group 4 (XRCC4) and their association with non-small-cell lung cancer (NSCLC) susceptibility in a Chinese population. A total of 507 NSCLC patients and 662 healthy controls were recruited for genotyping. Epidemiological and clinical data were also collected for association studies. The data showed that the rs1799794 G allele in the XRCC3 gene and minor allele carriers of XRCC4, including rs1056503 and rs9293337, were inversely associated with NSCLC risk (GG vs homozygote AA), whereas the rs861537 AG or AA genotype and XRCC4 rs6869366 had a significantly increased NSCLC risk. Furthermore, tobacco smoking over 26 pack-years, a family history of lung cancer, exposure to environmental tobacco smoke (ETS) and negative mental status were risk factors for developing NSCLC. This study suggests that SNPs of XRCC3 and XRCC4 and other environmental factors are risk factors for developing NSCLC in this Chinese Han population.

Association between the XRCC3 T241M polymorphism and risk of cancer: evidence from 157 case-control studies

The T241M polymorphism in the X-ray cross-complementing group 3 (XRCC3) had been implicated in cancer susceptibility. The previous published data on the association between XRCC3 T241M polymorphism and cancer risk remained controversial. Hence, we performed a meta-analysis to investigate the association between cancer susceptibility and XRCC3 T241M (61,861 cases and 84,584 controls from 157 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 observed in any genetic model (dominant model: odds ration [OR]=1.07, 95% confidence interval [CI]=1.00-1.13; recessive model: OR=1.15, 95% CI=1.08-1.23; additive model: OR=1.17, 95% CI=1.08-1.28) when all eligible studies were pooled into the meta-analysis. In further stratified and sensitivity analyses, the elevated risk remained for subgroups of bladder cancer and breast cancer, especially in Caucasians. In addition, significantly decreased lung cancer risk was also observed. In summary, this meta-analysis suggests the participation of XRCC3 T241M in the susceptibility for bladder cancer and breast cancer, especially in Caucasians, and XRCC3 T241M polymorphism is associated with decreased lung cancer risk. Moreover, our work also points out the importance of new studies for T241M association in some cancer types, such as gastric cancer, colorectal cancer, and melanoma skin cancer, where at least some of the covariates responsible for heterogeneity could be controlled, to obtain a more conclusive understanding about the function of the XRCC3 polymorphism in cancer development.

Lack of association between XRCC3 rs861539 (C > T) polymorphism and lung cancer risks: an update meta-analysis

X-ray repair cross-complementing protein 3 (XRCC3) belongs to DNA double-strand break repair pathway and XRCC3 rs861539 (C > T) polymorphism has been suspected with lung cancer risk. However, results from previous studies are inconclusive and affected by bias. Electronic databases of PubMed, EMBASE, China National Knowledge Infrastructure, and SinoMed were searched. References of relative reviews were also screened. Pooled odds ratios (ORs) and 95 % confidence intervals (CIs) were calculated to estimate the association strength. A number of 18 eligible studies with 6 studies of Asians, 11 of Caucasians, and 1 of African were extracted and analyzed, including 4,896 lung cancer cases and 6,360 controls. No significant correlation between XRCC3 polymorphism and lung cancer risk was observed in homozygote comparison (CC vs. TT; OR=0.877; 95 % CI, 0.659, 1.168), heterozygote comparison (CT vs. TT; OR=0.857; 95 % CI, 0.675, 1.089), dominant model (CC/CT vs. TT; OR=0.862; 95 % CI, 0.663, 1.123), or recessive model (CC vs. CT/TT; OR=1.047; 95 % CI, 0.956, 1.145). Subgroup analyses of ethnicity and controls did not reveal any significant association with lung cancer risk. No publication bias was detected. In this update meta-analysis of 18 studies and 11,256 participants, we find that XRCC3 rs861539 polymorphism does not contribute to lung cancer risk and there is no difference between Asians and Caucasians.

Association between the NBS1 Glu185Gln polymorphism and lung cancer risk: a systemic review and meta-analysis

Nijmegen Breakage Syndrome protein 1 (NBS1) is one of the most important DNA repair proteins playing important roles in maintaining the genomic stability of NDA. Previous studies regarding the association between NBS1 8360G>C (Glu185Gln) polymorphism and lung cancer reported conflicting results. To derive a more precise estimation of this association, a systemic review and meta-analysis was performed. We performed a meta-analysis using eligible case-control studies to summarize the data on the association between the NBS1 Glu185Gln polymorphism and lung cancer risk. Odds ratios (ORs) with corresponding 95 % confidence intervals (95 %CIs) were pooled to assess the association between NBS1 Glu185Gln polymorphism and lung cancer risk. Six case-control studies with a total of 2,348 lung cancer cases and 2,401 controls without canner were included into the meta-analysis. Overall, there was an association between NBS1 Glu185Gln polymorphism and lung cancer risk under the dominant comparison model (fixed-effects OR GluGln/GlnGln vs. GluGlu = 1.21, 95 % CI 1.07-1.37, P = 0.002, I (2) = 8.1 %). Subgroup analysis by race suggested a significant association between NBS1 Glu185Gln polymorphism and lung cancer risk in Asians (fixed-effects OR GluGlnGlnGln vs. GluGlu = 1.22, 95 % CI 1.06-1.41, P = 0.005) but not in Caucasians (fixed-effects OR GluGlnGlnGln vs. GluGlu = 1.17, 95 % CI 0.91-1.50, P = 0.220). This meta-analysis supports that there is an association between NBS1 Glu185Gln polymorphism and lung cancer risk. More studies are needed to further verify this association.

Association between the NBS1 Glu185Gln polymorphism and breast cancer risk: a meta-analysis

Nijmegen breakage syndrome 1 (NBS1), a vital DNA repair protein in the homologous recombination repair pathway and a signal modifier in the intra-S phase checkpoint, plays a critical role in cellular response to DNA damages and the maintenance of genomic stability. The NBS1 Glu185Gln (NBS1 E185Q, NBS1 8360G>C, rs1805794) polymorphism has been indicated to be involved in the development of cancer, but results of previous individual studies on the association between NBS1 Glu185Gln polymorphism and breast cancer risk remain controversial and inconclusive. Our meta-analysis investigated this association for the first time by pooling the odds ratios with corresponding 95 % confidence intervals (95 % CIs) of all individual publications available to date. Overall, 14 separate studies with 6,642 cases and 7,138 controls were finally included into the present meta-analysis after a comprehensive literature search of the PubMed, Embase, Web of Science, and China National Knowledge Infrastructure databases up to October 21, 2012. Overall analysis and subgroup analyses by ethnicity and source of controls were performed. Meta-analysis of total studies showed that the NBS1 Glu185Gln variant carriers were not susceptible to breast cancer (ORGln vs. Glu = 1.05, 95 % CI 0.80-1.39, P OR = 0.719; OR Gln/Gln vs. Glu/Glu = 0.82, 95 % CI 0.62-1.08, P OR = 0.154; OR Glu/Gln vs. Glu/Glu = 1.00, 95 % CI 0.90-1.13, P OR = 0.939; ORGln/Gln + Glu/Gln vs. Glu/Glu = 0.96, 95 % CI 0.83-1.11, P OR = 0.551; ORGln/Gln vs. Glu/Glu + Glu/Gln = 0.84, 95 % CI 0.67-1.05, P OR = 0.134). Similar results were observed in heterogeneity-adjusted meta-analysis of all studies. Furthermore, subgroup analyses by ethnicity and source of controls did not identify any appreciable relationship of the NBS1 Glu185Gln polymorphism with breast cancer susceptibility in any populations. Sensitivity analysis by sequentially omitting individual studies confirmed the stability and reliability of our results. Our meta-analysis of currently available data shows no association between the NBS1 Glu185Gln polymorphism and breast cancer risk.

Genetic susceptibility to lung cancer--light at the end of the tunnel?

Lung cancer is one of the most common and deadliest cancers in the world. The major socio-environmental risk factor involved in the development of lung cancer is cigarette smoking. Additionally, there are multiple genetic factors, which may also play a role in lung cancer risk. Early work focused on the presence of relatively prevalent but low-penetrance alterations in candidate genes leading to increased risk of lung cancer. Development of new technologies such as genomic profiling and genome-wide association studies has been helpful in the detection of new genetic variants likely involved in lung cancer risk. In this review, we discuss the role of multiple genetic variants and review their putative role in the risk of lung cancer. Identifying genetic biomarkers and patterns of genetic risk may be useful in the earlier detection and treatment of lung cancer patients.

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

Many studies have examined the association between the XRCC3 Thr241Met gene polymorphism and lung cancer risk in various populations, but their results have been inconsistent. To assess this relationship more precisely, a meta-analysis was performed. The PubMed, Embase, Web of Science, and CNKI database was searched for case–control studies published up to July 2012. Data were extracted and pooled odds ratios (OR) with 95% confidence intervals (CI) were calculated.

Ultimately, 17 studies, comprising 4123 lung cancer cases and 5597 controls were included. Overall, for T allele carriers (TC + TT) versus the wild-type homozygotes (CC), the pooled OR was 0.95 (95% CI = 0.87-1.04 P = 0.228 for heterogeneity), for TT versus CC the pooled OR was 0.99 (95% CI = 0.86-1.15 P = 0.315 for heterogeneity). In the stratified analysis by ethnicity, histological types of lung cancer and smoking status, no any significantly risks were found for (C/T + T/T) vs C/C or T/T vs C/C. No publication bias was found by using the funnel plot and Egger's test.

Overall, there is no evidence showing a significant correlation between XRCC3 Thr241Met polymorphism and lung cancer risk stratified analysis by ethnicity, histology and smoking status.

XRCC1 gene polymorphisms and lung cancer susceptibility: a meta-analysis of 44 case-control studies

X-ray repair cross-complementing group 1 gene (XRCC1) has been implicated in risk for lung cancer. However, the results from different studies remain controversial. In this meta-analysis, we have assessed 44 published case-control studies regarding associations of lung cancer risk with three common polymorphisms, codon 194, codon 280 and codon 399, and -77 T > C in the promoter region of XRCC1. The results in total population showed that the risk for lung cancer was increased among the variant homozygote Trp/Trp of codon 194 polymorphism, compared with the wild type Arg/Arg (OR: 1.19; 95 % CI 1.01-1.39), and the variant genotype CC of -77 T > C polymorphism showed a significantly increased risk of developing lung cancer, compared to wild-type genotype TT (OR: 1.91; 95 % CI 1.24-2.94). However, no associations were found between lung cancer risk and codon 280, codon 399. In the subgroup analyses by ethnicity, the OR for the variant homozygote Trp/Trp of codon 194 was 1.21(95 % CI 1.02-1.43) for Asian. When stratified by source of control, we found a protective effect of codon 194 Arg/Trp genotype (OR: 0.87; 95 % CI 0.77-0.98) and risk effect of codon 399 combined Arg/Gln + Gln/Gln variant genotype (OR: 1.09; 95 % CI 1.01-1.18) for lung cancer on the basis of hospital control. Subgroup analyses by histological types of lung cancer indicated that the heterozygote Arg/Trp in codon 194 could decrease and the combined variant genotype Arg/Gln + Gln/Gln in codon 399 could increase the risk of non-small cell lung cancer (OR: 0.69; 95 % CI 0.57-0.85 and OR: 1.14; 95 % CI 1.04-1.24). In conclusion, this meta-analysis has demonstrated that codon 194, codon 399 and -77 T > C polymorphisms of XRCC1 gene might have contributed to individual susceptibility to lung cancer. To further evaluate effect of XRCC1 polymorphisms, gene-gene interaction and gene-environment interaction on lung cancer risk, a single large sample size study with thousands of subjects is required to get conclusive results.

Genetic variation in the NBS1 gene is associated with hepatic cancer risk in a Chinese population

NBS1 plays important roles in maintaining genomic stability as a key DNA repair protein in the homologous recombination repair pathway and as a signal modifier in the intra-S phase checkpoint. We hypothesized that polymorphisms of NBS1 are associated with hepatic cancer (HCC) risk. The NBS1 rs1805794 C/G polymorphism has been frequently studied in some cancers with discordant results, but its association with HCC has not been investigated. Moreover, studies of the 3'UTR variant rs2735383 have not touched upon HCC. This study examined the contribution of these two polymorphisms to the risk of developing HCC in a Chinese population. NBS1 genotypes were determined in 865 HCC patients and 900 controls and the associations with risk of HCC were estimated by logistic regression. Compared with the rs1805794 GG genotype, the GC genotype had a significantly increased risk of HCC (adjusted odds ratios [OR]=1.41; 95% confidence interval [CI]=1.11-1.80), the CC carriers had a further increased risk of HCC (OR=2.27; 95% CI=1.68-3.14), and there was a trend for an allele dose effect on risk of HCC (p<0.001). Also, we found that the risk effect of rs1805794 CC+CG was more pronounced in HCC patients that drank (OR=2.28, 95% CI=1.55-3.29 for drinkers; OR=1.31, 95% CI=1.00-1.77 for nondrinkers). However, there was no significant difference in genotype frequencies of rs2735383 G/C site between cases and controls. These findings suggest that rs1805794 C/G polymorphism in NBS1 may be a genetic modifier for developing HCC.

Association of CTTN polymorphisms with the risk of colorectal cancer

Purpose

Various studies searching for biomarkers to predict tumor metastasis or prognosis in both esophageal squamous cell carcinoma (ESCC) and head and neck squamous cell carcinoma (HNSCC) are currently underway. However, few data have been reported on its association with colorectal cancer (CRC). Single nucleotide polymorphisms (SNPs) are the most common known form of human genetic variation and may contribute to an increased susceptibility to cancer including CRC. The present study aimed to investigate whether the polymorphisms in the CTTN gene are associated with susceptibility to CRC in the Korean population.

Methods

A case-control study was performed to examine the relationship between the CTTN g.-9101C>T, g.-8748C>T, and g.72C>T polymorphisms and the risk of CRC. Polymerase chain reaction-restriction fragment length polymorphism analysis of g.-8748C>T, g.-9101C>T and Taqman analysis of g.72C>T were performed on blood samples from 218 patients with CRC and 533 control individuals. The g.-9101C>T, g.-8748C>T, and g.72C>T SNPs in CTTN and their haplotypes were analyzed.

Results

The genotype and allele frequencies of g.-9101C>T, g.-8748C>T, and g.72C>T did not differ between the patient group and the control group. Further, the haplotype of CTTN g.-9101C>T, g.-8748C>T, and g.72C>T did not differ between patient group and the control group. However, the genotype and allele frequencies of CTTN g.-9101C>T were significantly increased in the lymph node positive CRC group compared to the control group.

Conclusion

The CTTN g.-9101C>T polymorphism may influence lymph node positive CRC.

Lung cancer in never smokers

Lung cancer in never smokers (LCINS) is the seventh leading cause of death among solid tumors. The main risk factor for lung cancer is smoking; however, approximately 15% of lung cancer patients have never smoked. LCINS is more frequent in women, irrespective of geographical location, nevertheless, the highest incidence has been found in South-East Asia. The histological incidence of adenocarcinoma is higher in the group of never smokers than squamous cell carcinoma. There is a familial clustering of lung cancer that is more pronounced in never smokers, where the family history was associated with an increased risk. Genome-wide association studies identified certain chromosomal aberrations in LCINS. Furthermore, the oncogenic mutation pattern is distinct in nonsmoking patients: activating mutations of EGFR or anaplastic lymphoma kinase are more frequent. The etiology of LCINS includes several environmental factors as well, such as environmental tobacco smoke, viral and hormonal factors, a variety of pulmonary diseases and certain occupational exposures. It is now established that EGFR-tyrosine kinase inhibitor treatment (erlotinib and geftinib) in lung cancer is more effective in LCINS, owing to the higher incidence of EGFR mutation in nonsmokers. Despite the growing body of information on LCINS in recent years there is a need to further investigate the pathogenesis of this particular lung cancer. Future studies on LCINS should try to tackle the issues of prevention, early diagnosis and the exploration of novel therapeutic targets to combat lung cancer disease.

Investigation of Arg399Gln and Arg194Trp polymorphisms of the XRCC1 (x-ray cross-complementing group 1) gene and its correlation to sister chromatid exchange frequency in patients with chronic lymphocytic leukemia

Polymorphisms of the x-ray repair cross-complementing group 1 (XRCC1) gene have been reported to be associated with various forms of cancer. We evaluated the possible effects of the Arg194Trp and the Arg399Gln polymorphisms on the risk for chronic lymphocytic leukemia (CLL) in 73 patients and 50 controls. We also analyzed their relation to frequency of sister chromatid exchange (SCE). With respect to codon 194, the allelic frequency of the Arg194Trp polymorphism did not significantly differ between the 2 groups. The proportion of individuals carrying the Arg194Trp polymorphism was not different in the 2 groups. With respect to codon 399, the proportion of the individuals carrying the Arg399Gln allele (90% vs 62%; p=0.000; odds ratio [OR], 5.779; 95% confidence interval [CI], 2.2-15.183) and the allelic frequency of the Arg399Gln polymorphism (56% vs 36%; p=0.002; OR, 2.278; 95% CI, 1.350-3.843) was significantly higher in the patient group. The frequency of the Arg/Gln genotype was significantly higher in the patient group (68.50% vs 52%; p=0.049; OR, 2.007; 95% CI, 0.955-4.217). The mean SCE frequency in the patient group was significantly higher (9.2±4 vs 7.5±2; p=0.02). When different compound genotypes were compared, the coexistence of Arg/Arg genotype in codon 194 with Arg/Arg genotype in codon 399 was significantly more frequent in the control group (30% vs 9%; p=0.004; OR, 0.247; 95% CI, 0.092-0.664). Within the patient group, SCE frequency did not differ between patients with various genotypes. The Arg399Gln polymorphism may be etiologically associated with CLL; however, it does not seem to increase SCE frequency.

ERCC1 and XRCC1 as biomarkers for lung and head and neck cancer

Advanced stage non-small cell lung cancer and head and neck squamous cell carcinoma are both treated with DNA damaging agents including platinum-based compounds and radiation therapy. However, at least one quarter of all tumors are resistant or refractory to these genotoxic agents. Yet the agents are extremely toxic, leading to undesirable side effects with potentially no benefit. Alternative therapies exist, but currently there are no tools to predict whether the first-line genotoxic agents will work in any given patient. To maximize therapeutic success and limit unnecessary toxicity, emerging clinical trials aim to inform personalized treatments tailored to the biology of individual tumors. Worldwide, significant resources have been invested in identifying biomarkers for guiding the treatment of lung and head and neck cancer. DNA repair proteins of the nucleotide excision repair pathway (ERCC1) and of the base excision repair pathway (XRCC1), which are instrumental in clearing DNA damage caused by platinum drugs and radiation, have been extensively studied as potential biomarkers of clinical outcomes in lung and head and neck cancers. The results are complex and contradictory. Here we summarize the current status of single nucleotide polymorphisms, mRNA, and protein expression of ERCC1 and XRCC1 in relation to cancer risk and patient outcomes.

[Gender-associated differences of lung cancer and mechanism]

肺癌是全球发病率、死亡率最高、治疗效果差的恶性肿瘤。肺癌在流行病学、病理类型、疗效和预后、甚至发病机制等多方面均表现出明显性别差异。对这些差异的深入剖析能更好地认识男女性别肺癌各自的特点，为肺癌防治采用不同的性别化措施提供新线索和思路；而对导致性别差异的具体机制进行深入研究，有助于阐明肺癌的发病机制。

Polymorphisms of XRCC1 and gastric cancer susceptibility: a meta-analysis

Studies investigating the association between X-ray repair cross-complementing gene 1 (XRCC1) polymorphisms and gastric cancer (GC) risk have reported conflicting results. We performed a meta-analysis of published case-control and cohort studies to better compare results between studies. Published literature from PubMed, EMBASE, and China National Knowledge Infrastructure were retrieved. 18 studies with 3,915 GC cases and 6,759 controls were selected. For XRCC1 Arg194Trp polymorphism, we only found the Trp/Trp genotype carriers might be at high risk of GC (TT vs. CC+CT: OR = 1.31, 95%CI = 1.04-1.65). When stratifying for ethnicity, the results showed there was a significant difference in genotype distribution between GC cases and controls among Asians (especially, in Chinese population), but not among Caucasians. When stratifying for control sources, significant association between Arg194Trp polymorphism and GC risk was only observed in the hospital-based controls' subgroup (TT vs. CC+CT: OR = 1.45, 95%CI = 1.13-1.87). Additionally, no significant association was detected in the gastric cardia cancer's subgroup. The results of the overall meta-analysis did not suggest any association between Arg280His/Arg399Gln polymorphisms and GC susceptibility for all genetic models. There was no evidence for the association between these two gene polymorphisms and GC risk in subgroup analyses based on study design, ethnicity, country, tumor location, Helicobacter pylori infection and the Lauren's classification of GC. In conclusion, XRCC1 Arg194Trp homozygous mutant genotype (Trp/Trp) was found to be associated with increased risk of GC.

Polymorphisms and haplotypes in the XRCC1 gene and the risk of advanced non-small cell lung cancer

INTRODUCTION AND HYPOTHESIS

Single-nucleotide polymorphisms (SNPs) and haplotypes in the x-ray repair cross-complementing group 1 (XRCC1) gene, which is one of the base excision repair genes, are thought to be associated with the risk of non-small cell lung cancer (NSCLC).

METHODS

We genotyped three coding (Arg280His, Arg399Gln, and Gln632Gln) SNPs and six haplotype-tagging SNPs (htSNPs) for 140 advanced NSCLC cases and 217 healthy controls (all Koreans) using unconditional logistic regression analysis, and this was adjusted for age, gender, and the smoking status. The haplotypes were reconstructed according to the genotyping data and the linkage disequilibrium status of these nine SNPs.

RESULTS

The minor allele heterozygotes of the rs1001581 htSNP showed an increased risk of NSCLC (adjusted odds ratio = 2.118, p = 0.013), and the minor allele homozygotes of the rs2293036 htSNP showed a decreased risk of NSCLC (adjusted odds ratio = 0.363, p = 0.020). Seven possible haplotypes were demonstrated in this study (haplotype frequency >1%). The GGGGGGGGG haplotype, which is composed of nine major alleles, showed a protective effect for developing NSCLC (odds ratio = 0.433, p = 0.002); however, the GGGGGGAGG haplotype that contained the minor allele of the rs1001581 demonstrated an increased risk of NSCLC (odds ratio = 1.597, p = 0.044). The above associations were similarly noted for the never smokers, and so the smoking status might modify the associations between the x-ray repair cross-complementing group 1 (XRCC1) genetic variants and the risk of developing NSCLC. On 10-million permutation testing, only the GGGGGGGGG haplotype was significantly associated with a decreased risk of NSCLC in the total group (p = 0.001).

CONCLUSIONS

This study presents several novel aspects of the genetic susceptibility to develop NSCLC. Larger studies that will focus on the role of the rs1001581 and rs2293036 htSNPs and haplotypes for developing NSCLC are needed in the future.

8-Oxoguanine incision activity is impaired in lung tissues of NSCLC patients with the polymorphism of OGG1 and XRCC1 genes

Decreased repair of oxidative DNA damage is a risk factor for developing certain human malignancies. We have previously found that the capacity of 8-oxo-7,8-dihydroguanine repair was lower in leukocytes of NSCLC patients than in controls. To explain these observations, we searched for mutations and polymorphisms in the OGG1 gene among 88 NSCLC patients and 79 controls. One patient exhibited a heterozygous mutation in exon 1, which resulted in Arg46Gln substitution. Normal lung and tumor tissue carrying this mutation showed markedly lower 8-oxoG incision activity than the mean for all patients. The predominant polymorphism of OGG1 was Ser326Cys. A significant difference was observed in the frequencies of the OGG1 variants between populations of NSCLC patients and controls. The frequency of the Cys326 allele and the number of Cys326Cys homozygotes was higher among patients than controls. In individuals with either Ser326Cys or Cys326Cys genotype 8-oxoG incision rate was lower than in those with both Ser326 alleles, either in lung or leukocytes. Moreover, 8-oxodG level was higher in lung tissue and leukocytes of patients carrying two Cys326 alleles and in leukocytes of patients with the Ser326Cys genotype. We also screened for polymorphisms of the XRCC1 gene. Only heterozygotes of the XRCC1 variants Arg194Trp, Arg280His and Arg399Gln were found among patients and controls, with the frequency of Arg280His being significantly higher among patients. NSCLC patients with Arg280His or Arg399Gln polymorphism revealed lower 8-oxoG incision activity in their lung tissues, but not in leukocytes. We can conclude that the OGG1 Ser326Cys polymorphisms may have an impact on the efficiency of 8-oxoG incision in humans and the XRCC1 His280 and Gln399 may influence the OGG1 activity in tissues exposed to chronic oxidative/inflammatory stress. Higher frequency of the OGG1 Cys326 allele among NSCLC patients may partially explain the impairment of the 8-oxoG repair observed in their leukocytes.

Associations between polymorphisms in DNA repair genes and TP53 mutations in non-small cell lung cancer

This study was conducted to identify genetic factors predisposing to TP53 mutations in patients with non-small cell lung cancer (NSCLC). A comprehensive panel of potentially functional single nucleotide polymorphisms (SNPs) in DNA repair genes was evaluated in relation to TP53 mutations. Thirty-seven SNPs in 28 DNA repair genes were genotyped by a sequenome mass spectrometry-based genotyping assay in 173 NSCLCs and the associations with TP53 mutations in the entire coding exons (exons 2-11), including splicing sites of the gene, were analyzed. Four SNPs (XPA rs1800975, OGG1 rs1052133, ADPRT rs1136410, and NBS1 rs1805794) were significantly associated with the prevalence of TP53 mutations in multivariate analysis for each SNP. When the 4 SNPs were combined, the prevalence of TP53 mutations was increased as the number of bad genotypes increased (P(trend)=0.001). Patients with 3 and 4 bad genotypes had a significantly higher frequency of TP53 mutations than those with 0-1 bad genotypes (adjusted odds ratio=5.18, 95% confidence interval=1.51-17.81, P=0.01 and adjusted odds ratio=18.26, 95% confidence interval=2.87-116.09, P=0.002, respectively). These findings suggest that the 4 SNPs may modulate the occurrence of TP53 mutations and contribute to lung carcinogenesis. However, larger studies are required to confirm our findings in other ethnic populations.