Influence of common XPD and XRCC1 variant alleles on p53 mutations in lung tumors

A comprehensive meta-analysis and a case-control study give insights into genetic susceptibility of lung cancer and subgroups

Reports of genetic association of polymorphisms with lung cancer in the Indian subcontinent are often conflicting. To summarise and replicate published evidence for association with lung cancer and its subgroups. We performed a meta-analysis of candidate associations on lung cancer, its histological subtypes and smoking status in the Indian subcontinent following PRISMA guidelines. Multiple testing corrections were done by the Benjamini-Hochberg method through assessment of significance at a false discovery rate of 10%. We genotyped and investigated rs1048943/CYP1A1 in a case-control sample from eastern India, followed by its global meta-analysis using a similar protocol. Meta-analysis of 18 variants of 11 genes reported in 39 studies (7630 cases and 8169 controls) showed significant association of rs1048943/CYP1A1 [2.07(1.49-2.87)] and rs4646903/CYP1A1 [1.48(1.93-1.95)] with overall lung cancer risk at 10% FDR, while nominal association (p < 0.05) was observed for del1/GSTT1, del2/GSTM1, rs1695/GSTP1 and rs17037102/ DKK2. Subtype analysis showed a significant association of del1/GSTT1 with adenocarcinoma, rs4646903/CYP1A1 with squamous carcinoma, and rs1048943/CYP1A1 with both. Association of rs4646903/CYP1A1 in smokers and effect modification by meta-regression analysis was observed. Genotyping of rs1048943/CYP1A1 that presented significant heterogeneity (p < 0.1) revealed an association with adenocarcinoma among eastern Indian smokers, while a global meta-analysis in 10458 cases and 10871 controls showed association with lung cancer and its subgroups. This study identified the susceptibility loci for lung cancer and its covariate-subgroups.

Assessment on the influence of TLR4 and DNA repair genes in laryngeal cancer susceptibility: a selective examination in a Romanian case control study

Background: Tumor characterization through the study of molecular biology has become an invaluable tool in understanding cancer development and evolution due to its relationship with chromosomal mutations, alterations or aberrations. The purpose of this study was to investigate the involvement of genes such as TLR-4 and DNA repair pathways (XRCC1 and XPD) in laryngeal cancer susceptibility in a Romanian population. Method: We performed a case-control study on 157 laryngeal cancer patients and 101 healthy controls. Genetic testing was carried out using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism. Results: We identified the Gln allele of the XPDLys751Gln polymorphism as an individual risk factor in laryngeal cancer development (Gln vs Lys, adjusted OR=1.65, 95%CI=1.13–2.40, P=0.008). Subjects with the mutant homozygote variant (Gln/Gln) had a two fold increase in cancer risk (adjusted OR=2.18, 95%CI=1.06–4.47, p=0.028) when compared to the reference wild type genotype (Lys/Lys). Stratification by sex and age, identified males under 62 years as the most susceptible group with an almost three fold risk (adjusted OR=2.94, 95%CI=1.31–6.59, p=0.007) for the dominant model (Lys/Gln+Gln/Gln). No associations were found for TLR-4Thr399Ile, XRCC1Arg194Trp and XRCC1Arg399Gln. Conclusion: The results of the study show that the XPDLys751Gln polymorphism may be among other independent risk factors for developing laryngeal cancer where as TLR-4Thr399Ile, XRCC1Arg194Trp and XRCC1 Arg399Gln show no such association. However, we consider the relative small number of the subjects selected for this analyses a possible limitation towards the real influence the obtain results may pertain in laryngeal cancer evolution.

Gene-environment and gene-gene interactions between CHRNA3 rs1051730, XRCC1 rs25487, and ERCC1 rs735482 variants highly elevate the risk of lung cancer

Background

Gene-gene and gene-environment interactions play an important role in cancer susceptibility. In this work, we studied the association of XRCC1 rs25487, ERCC1 rs735482, and CHRNA3 rs1051730 variants with lung cancer and assessed the modulatory effect of potential interaction between these variants on disease risk.

Results

In this study, 86 primary lung cancer patients and 64 control subjects were genotyped for CHRNA3 rs1051730, XRCC1 rs25487, and ERCC1 rs735482 by real-time PCR. The frequency of the three studied variants was higher among lung cancer patients than in control subjects, but with no statistical significance. ERCC1 rs735482 variant was associated with 6.9-fold increased risk to develop lung cancer among smokers (p = 0.03). Concomitant presence of CHRNA3 and ERCC1 wild alleles was associated with 2.7-fold elevated risk of lung cancer (p < 0.0001), while concomitant presence of CHRNA3 rs1051730 variant allele with ERCC1 wild allele was associated with 20-fold elevated risk (p < 0.000). Concomitant presence of both variants, ERCC1 rs735482 and CHRNA3 rs1051730, was associated with 9.9-fold elevated risk (p < 0.0001). Meanwhile, the concomitant presence of XRCC1 rs25487 with either ERCC1 rs735482 or CHRNA3 rs1051730 or both was not associated with increased risk of the disease.

Conclusion

Our results emphasize the role of gene-gene interaction in the pathogenesis of lung cancer. Large-scale further studies to clarify the underlying mechanisms are needed.

Prognostic Significance of p53 Protein and X-ray Repair Cross-Complementing Protein 1 in Non-Small Cell Lung Cancer

Objectives

p53 and XRCC1 protein expression were evaluated in 54 samples of non-small cell lung cancer.

Patients and methods

The immunohistochemical method was used for detection of the monitored proteins. Tissue samples were divided according to histopathological tumor type. The results were then compared with basic clinical and histopathological parameters (histopathological type, nuclear grade and TNM tumor stage IA, IB).

Results

Statistically significant correlations were found between histopathological type and p53 expression, since P <0.05 (P = 0.015). Comparing p53 expression with grade resulted in a strong positive correlation (P <0.0396, R2 = 0.9223). The percentage of p53-positive tumors progressively increased from 0% in grade 1 to 75% in grade 4. No correlation was found between p53 expression and tumor stage. In case of XRCC1, the highest level was found in squamous cell lung carcinoma, where 71% of samples was positive. In case of large cell carcinoma samples, it was 67%, and in adenocarcinoma 52% of samples showed XRCC1 immunoreactivity. No statistically significant correlation was found between histopathological type, grade or early stage (IA, IB) of non-small cell lung cancer and expression of XRCC1 protein profile without neoadjuvant therapy.

Conclusions

We found a statistically significant correlation between p53 expression and histopathological tumor type. It is possible that stabilized p53 protein plays an important role in the development of squamous and large cell carcinoma. Our findings also suggest that p53 expression cumulates with the dedifferentiation of cancer cells. It is possible that the expression of XRCC1 is not fixed and could be changed by the status of cancer cells and in relation to therapy. Relevant data about pre- versus post-chemotherapy and XRCC1 expression are needed to evaluate the influence of XRCC1 on drug resistance. Free full text available at www.tumorionline.it

Genetic variants of SULT1A1 and XRCC1 genes and risk of lung cancer in Bangladeshi population

Lung cancer is one of the most frequently occurring cancers throughout the world as well as in Bangladesh. This study aimed to correlate the prognostic and/or predictive value of functional polymorphisms in SULT1A1 (rs9282861) and XRCC1 (rs25487) genes and lung cancer risk in Bangladeshi population. A case-control study was conducted which comprises 202 lung cancer patients and 242 healthy volunteers taking into account the age, sex, and smoking status. After isolation of genomic DNA, genotyping was done by polymerase chain reaction-restriction fragment length polymorphism method and the lung cancer risk was evaluated as odds ratio that was adjusted for age, sex, and smoking status. A significant association was found between SULT1A1 rs9282861 and XRCC1 rs25487 polymorphisms and lung cancer risk. In case of rs9282861 polymorphism, Arg/His (adjusted odds ratio = 5.06, 95% confidence interval = 3.05-8.41, p < 0.05) and His/His (adjusted odds ratio = 3.88, 95% confidence interval = 2.20-6.82, p < 0.05) genotypes were strongly associated with increased risk of lung cancer in comparison to the Arg/Arg genotype. In case of rs25487 polymorphism, Arg/Gln heterozygote (adjusted odds ratio = 4.57, 95% confidence interval = 2.79-7.46, p < 0.05) and Gln/Gln mutant homozygote (adjusted odds ratio = 4.99, 95% confidence interval = 2.66-9.36, p < 0.05) were also found to be significantly associated with increased risk of lung cancer. This study demonstrates that the presence of His allele and Gln allele in case of SULT1A1 rs9282861 and XRCC1 rs25487, respectively, involve in lung cancer prognosis in Bangladeshi population.

Haplotype CGC from XPD, hOGG1 and ITGA2 polymorphisms increases the risk of nasopharyngeal carcinoma in Malaysia

BACKGROUND

8-oxoG, a common DNA lesion resulting from reactive oxygen species (ROS), has been shown to be associated with cancer initiation. hOGG1 DNA glycosylase is the primary enzyme responsible for excision of 8-oxoG through base excision repair (BER). Integrins are members of a family of cell surface receptors that mediate the cell-cell and extracellular matrix (ECM) interactions. Integrins are involved in almost every aspect of carcinogenesis, from cell differentiation, cell proliferation, metastasis to angiogenesis. Loss of ITGA2 expression was associated with enhanced tumor intravasation and metastasis of breast and colon cancer. XPD gene encodes DNA helicase enzyme that is involved in nucleotide excision repair (NER). It is shown in previous research that XPD homozygous wildtype Lys/Lys genotype was associated with higher odds of NPC.

METHODS

We conducted a 1 to N case-control study involving 300 nasopharyngeal carcinoma (NPC) cases and 533 controls matched by age, gender and ethnicity to investigate the effect of hOGG1 Ser326Cys, ITGA2 C807T and XPD Lys751Gln polymorphisms on NPC risk. Linkage disequilibrium and haplotype analysis were conducted to explore the association of allele combinations with NPC risk. Restriction fragment length polymorphism (RFLP-PCR) was used for DNA genotyping.

RESULTS

No significant association was observed between hOGG1 Ser326Cys and ITGA2 C807T polymorphisms with NPC risk after adjustment for age, gender, ethnicity, cigarette smoking, alcohol and salted fish consumption. Lys/Lys genotype of XPD Lys751Gln polymorphism was associated with increased NPC risk (OR = 1.60, 95% CI = 1.06-2.43). Subjects with history of smoking (OR = 1.81, 95% CI = 1.26-2.60), and salted fish consumption before age of 10 (OR = 1.77, 95% CI = 1.30-2.42) were observed to have increased odds of NPC. The odds of developing NPC of CGC haplotype was significantly higher compared to reference AGC haplotype (OR = 2.20, 95% CI = 1.06-4.58).

CONCLUSION

The allele combination of CGC from hOGG1, ITGA2 and XPD polymorphisms was significantly associated with increased odds of NPC.

What's your poison? Impact of individual repair capacity on the outcomes of genotoxic therapies in cancer. Part II - information content and validity of biomarkers for individual repair capacity in the assessment of outcomes of anticancer therapy

The individual variance in the efficiency of repair of damage induced by genotoxic therapies may be an important factor in the assessment of eligibility for different anticancer treatments, the outcomes of various treatments and the therapy-associated complications, including acute and delayed toxicity and acquired drug resistance. The second part of this paper analyses the currently available information about the possibilities of using experimentally obtained knowledge about individual repair capacity for the purposes of personalised medicine and healthcare.

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.

Polymorphisms in apoptosis-related genes and TP53 mutations in non-small cell lung cancer

Apoptosis plays an essential role in the elimination of mutated or transformed cells from the body. Therefore, polymorphisms of apoptosis-related genes may lead to an alteration in apoptotic capacity, thereby affecting the occurrence of TP53 mutations in lung cancer. We investigated the relationship between potentially functional polymorphisms of apoptosis-related genes and TP53 mutations in non-small cell lung cancer (NSCLC). Twenty-seven single nucleotide polymorphisms in 20 apoptosis-related 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. None of the 27 polymorphisms was significantly associated with the occurrence of TP53 mutations. This suggests that apoptosis-related genes may not play an important role in the occurrence of TP53 mutations in lung cancer.

Functional polymorphisms of base excision repair genes XRCC1 and APEX1 predict risk of radiation pneumonitis in patients with non-small cell lung cancer treated with definitive radiation therapy

PURPOSE

To explore whether functional single nucleotide polymorphisms (SNPs) of base-excision repair genes are predictors of radiation treatment-related pneumonitis (RP), we investigated associations between functional SNPs of ADPRT, APEX1, and XRCC1 and RP development.

METHODS AND MATERIALS

We genotyped SNPs of ADPRT (rs1136410 [V762A]), XRCC1 (rs1799782 [R194W], rs25489 [R280H], and rs25487 [Q399R]), and APEX1 (rs1130409 [D148E]) in 165 patients with non-small cell lung cancer (NSCLC) who received definitive chemoradiation therapy. Results were assessed by both Logistic and Cox regression models for RP risk. Kaplan-Meier curves were generated for the cumulative RP probability by the genotypes.

RESULTS

We found that SNPs of XRCC1 Q399R and APEX1 D148E each had a significant effect on the development of Grade ≥2 RP (XRCC1: AA vs. GG, adjusted hazard ratio [HR] = 0.48, 95% confidence interval [CI], 0.24-0.97; APEX1: GG vs. TT, adjusted HR = 3.61, 95% CI, 1.64-7.93) in an allele-dose response manner (Trend tests: p = 0.040 and 0.001, respectively). The number of the combined protective XRCC1 A and APEX1 T alleles (from 0 to 4) also showed a significant trend of predicting RP risk (p = 0.001).

CONCLUSIONS

SNPs of the base-excision repair genes may be biomarkers for susceptibility to RP. Larger prospective studies are needed to validate our findings.

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.

XPD codon 312 and 751 polymorphisms, and AFB1 exposure, and hepatocellular carcinoma risk

BACKGROUND

Genetic polymorphisms in DNA repair genes may influence individual variation in DNA repair capacity, which may be associated with risk of hepatocellular carcinoma (HCC) related to the exposure of aflatoxin B1 (AFB1). In this study, we have focused on the polymorphisms of xeroderma pigmentosum complementation group D (XPD) codon 312 and 751 (namely Asp312Asn and Lys751Gln), involved in nucleotide excision repair.

METHODS

We conducted a case-control study including 618 HCC cases and 712 controls to evaluate the associations between these two polymorphisms and HCC risk for Guangxi population by means of TaqMan-PCR and PCR-RFLP analysis.

RESULTS

We found that individuals featuring the XPD genotypes with codon 751 Gln alleles (namely XPD-LG or XPD-GG) were related to an elevated risk of HCC compared to those with the homozygote of XPD codon 751 Lys alleles [namely XPD-LL, adjusted odds ratios (ORs) were 1.75 and 2.47; 95% confidence interval (CIs) were 1.30-2.37 and 1.62-3.76, respectively]. A gender-specific role was evident that showed an higher risk for women (adjusted OR was 8.58 for XPD-GG) than for men (adjusted OR = 2.90 for XPD-GG). Interestingly, the interactive effects of this polymorphism and AFB1-exposure information showed the codon 751 Gln alleles increase the risk of HCC for individuals facing longer exposure years (Pinteraction = 0.011, OR = 0.85). For example, long-exposure-years (> 48 years) individuals who carried XDP-GG had an adjusted OR of 470.25, whereas long-exposure-years people with XDP-LL were at lower risk (adjusted OR = 149.12). However, we did not find that XPD codon 312 polymorphism was significantly associated with HCC risk.

CONCLUSION

These findings suggest that XPD Lys751Gln polymorphism is an important modulator of AFB1 related-HCC development in Guangxi population.

Modulation of nucleotide excision repair in human lymphocytes by genetic and dietary factors

Gene-environment interactions determine inter-individual variations in nucleotide excision repair (NER) capacity. Oxidative stress was previously found to inhibit NER, thus supplementation with dietary antioxidants could prevent this inhibition, especially in genetically susceptible subjects. To study the effects of genetic polymorphisms in NER-related genes and dietary intake of antioxidants on an individual's NER capacity, lymphocytes of 168 subjects were isolated before and after a 4-week blueberry and apple juice intervention. Twelve genetic polymorphisms in NER genes XPA, XPC, ERCC1, ERCC2, ERCC5, ERCC6 and RAD23B were assessed by multiplex PCR with single base extension. Based on specific genotype combinations, a subset of individuals (n 36) was selected for phenotypical assessment of NER capacity, which was significantly affected by the total sum of low-activity alleles (P = 0.027). The single polymorphism XPA G23A was the strongest predictor of NER capacity (P = 0.002); carriers of low-activity alleles AA had about three times lower NER capacity than XPA GG carriers. NER capacity assessed before and after intervention correlated significantly (R(2) 0.69; P < 0.001), indicating that inter-individual differences in NER capacity are maintained over 4 weeks. Although the intervention increased plasma trolox equivalent antioxidant capacity from 791 (SE 6.61) to 805 (SE 7.90) microm (P = 0.032), on average it did not affect NER capacity. Nonetheless, carriers of twelve or more low-activity alleles seemed to benefit from the intervention (P = 0.013). Among these, carriers of the variant allele for RAD23B Ala249Val showed improved NER capacity upon intervention (P = 0.020). In conclusion, improved NER capacity upon dietary intervention was detected in individuals carrying multiple low-activity alleles. The XPA G23A polymorphism might be a predictor for NER capacity.

XRCC1 polymorphisms and lung cancer risk in Chinese populations: a meta-analysis

X-ray repair cross-complementing group 1 (XRCC1), one of the >20 genes that participate in the base excision repair (BER) pathway, is thought to account for differences in lung cancer susceptibility. Our meta-analysis on 2861 cases (lung cancer patients) and 2783 controls from eight eligible studies in Chinese populations showed that for the XRCC1 Arg194Trp polymorphism, compared with the Arg/Arg homozygous genotype, the variant Arg/Trp and Trp/Trp genotypes combined was not associated with lung cancer risk (OR=1.06, 95% confidence interval [CI]=0.89-1.27) (Z=0.70, P=0.48), nor was Arg280His (OR=0.63, 95% CI=0.28-1.41) (Z=1.12, P=0.26); however, for the XRCC1 Arg399Gln polymorphism, the combination of variant Arg/Gln and Gln/Gln genotypes was borderline significantly associated with lung cancer risk (OR=1.16, 95% CI=1.00-1.36) (Z=1.90, P=0.06), compared with the Arg/Arg homozygous genotype. Therefore, in the eight published studies in Chinese populations, we found little evidence of an association between the combined variant genotypes of the XRCC1Arg399Gln polymorphism and the increased risk of lung cancer.

Influence of DNA repair gene polymorphisms on the initial repair of MMS-induced DNA damage in human lymphocytes as measured by the alkaline comet assay

We have applied the alkaline comet assay to study the functional impact of gene polymorphisms in base excision repair (APEX1 Asp148Glu, XRCC1 Arg194Trp, XRCC1 Arg399Gln) and homologous recombination repair (XRCC3 Thr241Met, NBS1 Glu185Gln), two pathways that play crucial roles in the repair of DNA damage induced by methylmethane sulphonate (MMS). We also examined the effect of polymorphisms in mismatch repair (MLH1 -93 A/G) and nucleotide excision repair (XPD Lys751Gln) as putative negative controls based on the limited roles of these pathways in MMS-induced repair. Phytohemagglutinin-stimulated peripheral lymphocytes from 52 healthy individuals were treated with MMS and allowed to repair for 0, 15, 40, or 120 min after a 6-min washing step. DNA damage was measured as a pseudo-percentage score (comparable to % tail DNA) converted from a total visual score calculated from the distribution of cells with different degrees of damage (normal, mild, moderate and severe). The repair was faster at the beginning of the observation period than towards the end, and was not complete after 2 hr. Presence of the APEX1 148Asp, XRCC3 241Met or NBS1 185Gln alleles were significantly associated with a high pseudo-percentage score (above median) at early time points, with the APEX1 effect being most prolonged (up to 40 min after washing, odds ratio 5.6, 95% confidence interval 2.0-15.5). No significant effects were seen with the XRCC1 Arg194Trp, XRCC1 Arg399Gln, MLH1 -93A/G and XPD Lys751Gln polymorphisms. Our results provide evidence for the functional nature of the variant alleles studied in the APEX1, XRCC3, and NBS1 genes.

DNA repair gene polymorphisms affect cytotoxicity in the National Cancer Institute Human Tumour Cell Line Screening Panel

Polymorphisms in DNA repair genes have been suggested to increase the risk of cancer and other diseases, but the epidemiological studies are often not consistent, and the results confusing. We have examined the effect of polymorphisms in base and nucleotide excision-repair genes, as well as regulatory and signalling genes, on cytotoxic sensitivity of tumour cell lines used for screening anticancer drugs by the National Cancer Institute. It was found that for the TP53 P72R and ERCC2 D312N polymorphisms, the heterozygous genotype was most sensitive, while for the OGG1 S326C and NOS3 g.-786T>C polymorphisms the homozygous-variant genotype was most sensitive. The biggest increase in sensitization was found with the XRCC1 R399Q homozygous dominant genotype. The sensitization was found across a broad range of drugs, indicating the importance of DNA repair responses. It was also found that while the other gene polymorphisms were in Hardy-Weinberg equilibrium, the TP53 P72R heterozygous genotype was relatively depleted. For the OGG1 polymorphism, the repair of 8-oxo-guainine from DNA was measured in three panel cell lines that differed in their OGG1 genotype. The cell line with the homozygous-variant genotype had a much poorer repair than the other genotypes, as predicted. The correlation of polymorphisms with cytotoxicity may be an approach to understanding their effects which may be difficult to reveal in epidemiological studies.

Prognostic importance of DNA repair gene polymorphisms of XRCC1 Arg399Gln and XPD Lys751Gln in lung cancer patients from India

PURPOSE

Inter individual variation in lung cancer susceptibility may be modulated in part through genetic polymorphisms in the DNA repair genes, especially the genes involved in the Base Excision Repair (BER) and nucleotide excision repair (NER) pathway. Two of the genetic polymorphisms, XRCC1Arg399Gln and XPD Lys751Gln have been extensively studied in the association with lung cancer risk, although published studies have been inconclusive.

METHODS

In order to verify the role of the common variant alleles in the XPD gene, we have genotyped 211 lung cancer patients and 211 healthy controls using PCR-RFLP assays in a hospital based, case-control study in an Indian population. Logistic regression models were fit to examine the relationship between the log odds of lung cancer and each covariate. Overall Survival in relation to various genotypes and clinicopathological factors were analyzed using Kaplan Meier estimates and hazard ratios were calculated using Cox Regression analysis.

RESULTS

The carriers of XRCC1 399 AA genotypes were at higher risk of lung cancer (OR = 2.1, 95% CI:1.224-3.669, P = 0.007) than carriers of GG genotype. Subjects carrying 751 AC genotype were at an increased risk of carcinoma of the lung (OR = 1.8; 95% CI:1.233-2.807, P = 0.003) than subjects with AA genotypes. Compared to the XRCC1 399 GG/ XPD 751 AA reference genotype, the combined variants, XRCC1 399 GG/ XPD 751 AC+CC (OR = 1.9, 95% CI: 1.037-3.481), P = 0.03), XRCC1 399 GA+AA/ XPD 751 AA (OR = 1.7, 95% CI: 1.020-2.833, P = 0.04), XRCC1 399 GA+AA/XPD 751 AC+CC (OR = 2.7, 95% CI: 1.582-4.864, P = 0.01), had significantly higher odds ratios. Increasing numbers of either XPD or XRCC1 variant alleles were associated with shorter overall survival, the risk being significant for the XRCC1 gene polymorphism (P = 0.01 by log-rank test). The hazard of dying was significant for the XRCC1 399 AA genotype (HR = 3.04, 95%CI: 1.393-6.670, P = 0.005). Higher tumour stage also came out as significant predictors of patient death.

CONCLUSIONS

These findings suggest that genetic polymorphisms in the DNA repair genes may modulate overall lung cancer susceptibility and that pathological stage and XRCC1 Arg399Gln independently predicted overall survival among Indian lung cancer patients.

Prospective Assessment of XPD Lys751Gln and XRCC1 Arg399Gln Single Nucleotide Polymorphisms in Lung Cancer

PURPOSE

XRCC1 and XPD play key roles in the repair of DNA lesions and adducts. Contrasting findings have been reported on the effect of polymorphisms of these genes on the response to platinum-based chemotherapy in advanced non-small-cell lung cancer (NSCLC). This study aimed to investigate the relationship between the XPD Lys751Gln and XRCC1 Arg399Gln genotypes and outcome in lung cancer patients.

EXPERIMENTAL DESIGN

We genotyped 203 NSCLC and 45 small-cell lung carcinoma (SCLC) patients for the two polymorphisms. Most of the patients (81%) received a platinum-based chemotherapy.

RESULTS

The patients' genotype frequencies did not significantly differ from controls and both groups were in Hardy-Weinberg equilibrium for the two polymorphisms. The XRCC1399 Gln/Gln variant genotype was associated with a higher median survival time (80 weeks versus 54.6 weeks for the Arg/Gln heterozygous and 55.6 weeks for the wild-type Arg/Arg genotype; P=0.09). At the multivariable analysis adjusted for histology, stage of the disease, performance status, age, and gender, the Gln/Gln genotype was associated with a better survival of borderline significance in the subgroup of patients treated with cisplatin (hazard ratio, 0.55; 95% CI, 0.30-1.00); this association became significant for those with grade 3-4 clinical toxicity (hazard ratio, 0.46; 95% CI, 0.22-0.98). No association between XPD Lys751Gln genotype and clinical outcome was found.

CONCLUSION

This prospective investigation provides suggestive evidence of a favorable effect of the XRCC1399 Gln/Gln genotype on survival in platinum-treated NSCLC and, for the first time, in SCLC patients also. This contrasts with other authors who did not include non-platinum-treated patients, but it does fit the expectation for a suboptimal ability to remove DNA adducts.

DNA repair gene polymorphisms and probability of p53 mutation in bladder cancer

We investigated if the presence of single nucleotide polymorphisms (SNPs) in the XRCC1, XRCC3, and XPD genes were associated with the type and frequency of p53 mutations in bladder cancer. Using a hospital-based case-control study we have previously reported risks for the XRCC1 codon 194, XRCC1 codon 399, XRCC3 codon 241, and XPD codon 751 SNPs 1-3. We have also previously reported mutation data for 149 cases from this study who were screened for mutations in exons 4 through 9 of the p53 gene 4. Here we investigate possible associations between the DNA repair SNPs mentioned above and the presence of p53 mutations by comparing the frequency of each genotype between p53 mutation positive and negative cases. We also considered different classes of p53 mutations, including any mutation (nonsense, missense or silent), transversions and transitions and estimated odds ratios (ORs) and 95% confidence intervals (CI) for these associations. Cases with the XRCC1 codon 399 Gln/Gln genotype were positively associated with the presence of p53 transversions (OR = 4.8; 94% CI = 0.8-30). Cases with the XPD codon 751 Gln/Gln genotype were positively associated with the presence of p53 transitions (OR = 2.8; 95% CI = 0.8-9.3), in particular G:C-A:T transitions (OR = 3.7; 95% CI = 1.1-13). Our data provide some limited support for the hypothesis that mutations in the p53 gene in bladder cancer may differ according to the presence or absence of certain DNA repair gene variants.

Association of polymorphisms in ERCC2 gene with non-familial thyroid cancer risk

The ERCC2 protein is an evolutionary conserved ATP-dependent helicase that is associated with a TFIIH transcription factor complex and plays an important role in nucleotide excision repair. Mutations in this gene are responsible for xeroderma pigmentosum and also for Cocayne syndrome and trichothiodystrophy. Several single nucleotide polymorphisms have been identified in the ERCC2 locus. Among them, a G23591A polymorphism in the codon 312 results in an Asp --> Asn substitution in a conserved region and a A35931C polymorphism in the codon 751 results in a Lys --> Gln substitution. Because these polymorphisms have been associated with an increased risk for several types of cancers, we carried out an hospital based case-control study in a Caucasian Portuguese population to evaluate the potential role of these polymorphisms on the individual susceptibility to thyroid cancer. The results obtained did not reveal a significant association between each individual polymorphism studied (G23591A and A35931C) and an increased thyroid cancer risk, but individuals homozygous for non-wild-type variants are overrepresented in patients group. The evaluation of the different haplotypes generated by these polymorphisms showed that individuals simultaneously homozygous for rare variants of both polymorphisms have an increased risk for thyroid cancer [adjusted odds ratio (OR) 3.084; 95% confidence interval (95% CI), 1.347-7.061; P = 0.008] and for papillary thyroid-type tumors (adjusted OR, 2.997; 95% CI, 1.235-7.272; P = 0.015) but not for follicular thyroid-type tumors. These results suggest that genetic polymorphisms in this gene might be associated with individual susceptibility towards thyroid cancer, mainly papillary-type tumors, but larger studies are required to confirm these results.

Influence of polymorphism in DNA repair and defence genes on p53 mutations in bladder tumours

We studied the effects of polymorphisms in nine genes involved in DNA repair and detoxification on occurrence and type of p53 mutation in 327 bladder cancer patients. The included polymorphisms are XPC(Lys939Gln), XPD(Lys751Gln), XPG(Asp1104His), XRCC1(Arg3999Gln), XRCC3(Thr241Met), NBS1(Glu185Gln), cyclin D1(Pro241Pro), MTHFR(Ala222Val and Glu429Ala) and NQO1(Arg139Trp and Pro187Ser). We found increased risk for p53 mutation among cyclin D1 variant allele homozygotes (OR 2.4 CI 0.8-6.7). Among non-smokers, 75% (3/4) with p53 mutation but only 12.5% (3/24) without p53 mutations were XRCC3 241Met homozygotes (P=0.03). Among smokers, all p53 transversions (3/3), but only 41.7% (5/12) of p53 transitions were found among carriers of the XPC 939Gln allele. Individuals carrying the NQO1 187Ser allele showed increased risk for p53 transversions (OR 4.7, CI 0.9-26.1). All (2/2) NQO1 139Trp allele carriers but only 17.5% (7/40) of the Arg139 homozygotes had p53 transversions. Our findings suggest that altered repair and detoxification due to genetic polymorphism may influence the occurrence of p53 mutations in bladder cancer.

XRCC1 polymorphisms and cancer risk: a meta-analysis of 38 case-control studies

Several potential functional polymorphisms (Arg194Trp, Arg280His, Arg399Gln) in the DNA base excision repair gene X-ray repair cross-complementing group 1 (XRCC1) have been implicated in cancer risk. Our meta-analysis on total of 11,957 cancer cases and 14,174 control subjects from 38 published case-control studies showed that the odds ratio (OR) for the variant genotypes (Trp/Trp + Arg/Trp) of the Arg194Trp polymorphism, compared with the wild-type homozygote (Arg/Arg), was 0.89 [95% confidence interval (95% CI), 0.81-0.98] for all tumor types without between-study heterogeneity. Similarly, the overall risk for the combined variant genotypes (His/His + Arg/His) of the Arg280His, compared with the wild homozygote (Arg/Arg), was 1.19 (95% CI, 1.00-1.42). However, there was no main effect in either recessive or dominant modeling for the Arg399Gln, and the variant Gln/Gln homozygote was not associated with overall cancer risk (OR, 1.01; 95% CI, 0.90-1.14). The analyses suggest that XRCC1 Arg194Trp, Arg280His polymorphisms may be biomarkers of cancer susceptibility and a single larger study with thousands of subjects and tissue-specific biochemical and biological characterization is warranted to further evaluate potential gene-to-gene and gene-to-environment interactions on XRCC1 polymorphisms and cancer risk.

Polymorphisms in DNA repair genes in the molecular pathogenesis of esophageal (Barrett) adenocarcinoma

To test the hypothesis that aberrations of DNA repair contribute to susceptibility for the progression of gastroesophageal reflux disease (GERD) into Barrett esophagus (BE) and esophageal adenocarcinoma (EADC), we studied the frequency of polymorphisms of selected DNA repair genes in patients with GERD (n = 126), BE (n = 125) and EADC (n = 56) enrolled in a 2-year prospective case-control study. Controls comprised 95 strictly asymptomatic healthy individuals. Using genomic DNA extracted from blood samples, we identified wild-type and polymorphic variants of XPD (Arg156Arg and Lys751Gln), XRCC1 (Arg194Trp and Arg399Gln) and XRCC3 (Thr241Met), and the poly (AT) insertion/deletion of XPC (PAT). Allelic frequencies were compared between cases and controls using logistic regression to calculate age, gender, smoking and alcohol-adjusted odds ratios (OR) and 95% confidence intervals (CI). Patients with EADC demonstrated a significantly higher frequency of the XPC PAT homozygous variant genotype compared with asymptomatic controls (OR = 3.82; 95% CI = 1.05-13.93). Significantly reduced frequencies were seen for the XPD Lys751Gln homozygous variant genotype in patients with EADC (OR = 0.24; 95% CI = 0.07-0.88), and for the XRCC1 Arg399Gln homozygous variant genotype in patients with BE (OR = 0.38; 95% CI = 0.12-0.64) and GERD (OR = 0.29; 95% CI = 0.12-0.66). We conclude that the malignant phenotype probably results from a summation of polymorphic nucleotide excision repair genes showing opposing effects (an increased risk of XPC versus a protective effect of XPD). The protective effect of the homozygous variant of XRCC1 Arg399Gln for GERD and BE suggests that base excision repair alterations may occur early in progression to EADC, likely in response to GERD-induced endogenous oxidative or inflammatory DNA damage. As GERD and BE are highly prevalent in the general population, this protective effect may well explain why only a fraction of individuals with GERD and BE progress into invasive EADC.

Polymorphisms in XPD Exons 10 and 23 and Bladder Cancer Risk

INTRODUCTION

The nucleotide excision repair gene, xeroderma pigmentosum complementation group D (XPD), has been hypothesized to have a role in cancer risk, but results from prior molecular epidemiologic studies and genotype-phenotype analyses are conflicting.

MATERIALS AND METHODS

We examined the frequency of the XPD Asp312Asn polymorphism in exon 10 and the XPD Lys751Gln polymorphism in exon 23 in 505 incident bladder cancer cases and 486 healthy controls.

RESULTS

Overall, the XPD exon 10 and 23 genotypes were not associated with bladder cancer risk, after adjusting for age, sex, ethnicity, and smoking status. A gender-specific role was evident that showed an increased risk for women, but not for men, associated with the variant genotypes for both exons. For example, when the exon 23 variant allele genotypes were combined (Lys/Gln + Gln/Gln), there was an increased bladder cancer risk in women [odds ratio (OR), 1.69; 95% confidence interval (95% CI), 1.12-2.58] but not in men (OR, 0.99; 95% CI, 0.79-1.24; P(interaction) = 0.041; OR, 1.62; 95% CI, 1.02-2.58). There was also a gene-smoking interaction that showed the variant alleles for either exon or the combination of both increase the risk of bladder cancer for light and heavy smokers. For exon 23 (P(interaction) = 0.057; OR, 1.21; 95% CI, 0.99-1.47), heavy smokers (> or = 20 pack-years) who carried the exon 23 variant allele genotypes had an OR of 4.13 (95% CI, 2.53-6.73), whereas heavy smokers with the wild-type genotypes were at lower risk (OR, 3.55; 95% CI, 2.19-5.75). Moderate smokers (1-19 pack-years) with the variant allele genotypes had an OR of 1.54 (95% CI, 0.94-2.53), whereas moderate smokers with the wild-type genotypes had an OR of 1.12 (95% CI, 0.63-1.98).

CONCLUSIONS

Although we did not observe main effects associated with the XPD genotypes, these results do suggest the variant allele genotypes were associated with increased bladder cancer risk in women and smokers with statistically significant interactions in the exon 23 polymorphism. Although there is biological plausibility, these novel findings for gender and smoking should be interpreted with caution upon confirmation in larger studies.

Genotoxicity of tobacco smoke and tobacco smoke condensate: a review

This report reviews the literature on the genotoxicity of mainstream tobacco smoke and cigarette smoke condensate (CSC) published since 1985. CSC is genotoxic in nearly all systems in which it has been tested, with the base/neutral fractions being the most mutagenic. In rodents, cigarette smoke induces sister chromatid exchanges (SCEs) and micronuclei in bone marrow and lung cells. In humans, newborns of smoking mothers have elevated frequencies of HPRT mutants, translocations, and DNA strand breaks. Sperm of smokers have elevated frequencies of aneuploidy, DNA adducts, strand breaks, and oxidative damage. Smoking also produces mutagenic cervical mucus, micronuclei in cervical epithelial cells, and genotoxic amniotic fluid. These data suggest that tobacco smoke may be a human germ-cell mutagen. Tobacco smoke produces mutagenic urine, and it is a human somatic-cell mutagen, producing HPRT mutations, SCEs, microsatellite instability, and DNA damage in a variety of tissues. Of the 11 organ sites at which smoking causes cancer in humans, smoking-associated genotoxic effects have been found in all eight that have been examined thus far: oral/nasal, esophagus, pharynx/larynx, lung, pancreas, myeoloid organs, bladder/ureter, uterine cervix. Lung tumors of smokers contain a high frequency and unique spectrum of TP53 and KRAS mutations, reflective of the PAH (and possibly other) compounds in the smoke. Further studies are needed to clarify the modulation of the genotoxicity of tobacco smoke by various genetic polymorphisms. These data support a model of tobacco smoke carcinogenesis in which the components of tobacco smoke induce mutations that accumulate in a field of tissue that, through selection, drive the carcinogenic process. Most of the data reviewed here are from studies of human smokers. Thus, their relevance to humans cannot be denied, and their explanatory powers not easily dismissed. Tobacco smoke is now the most extreme example of a systemic human mutagen.

Polymorphisms in DNA repair genes, chromosome aberrations, and lung cancer

We have previously investigated the role of polymorphic chemical metabolizing genes in the susceptibility to the development of lung cancer using 110 primary lung cancer patients and 119 matched smoker controls. Together with data from the present study on DNA repair genes, we did not observe significant associations between any single variant genotype for several DNA-repair and chemical-metabolizing genes (XPD [or ERCC2], XRCC1, XRCC3, GSTM1, GSTT1, MPO, and mEH [or EPHX1]) and lung cancer. In the present study, we have further evaluated a nested group of 79 patients and 69 matched controls, and observed that increased chromosome aberrations (CAs) were associated with variant DNA-repair genotypes among both the patient and the control groups, with a significant increase for individuals having the XPD Lys/Gln + Gln/Gln genotypes (P = 0.046). Patients often had significantly increased CAs compared with controls with the same DNA-repair genotype and with similar cigarette smoking habits (< or =40 pack-years or >40 pack-years). Analyses of interactions between the DNA-repair and chemical-metabolizing genes indicated that the most significant interactions were between the repair genotypes and the GSTM1/T1 null genotypes. Significant increases in CA from the interactions were often observed among patients with < or =40 pack-years, but not among those with >40 pack-years. Since some variant DNA-repair genotypes have functional deficits for DNA repair, the association between variant DNA-repair genotypes and increased CAs suggests a risk mechanism for the development of lung cancer, with the DNA-repair genotypes interacting with variant chemical metabolizing genotypes to further increase the risk. The observation that patients had significantly increased CA frequencies compared with controls, irrespective of genotype, suggests that patients have additional factors that contribute to the development of lung cancer.

Functional characterization of polymorphisms in DNA repair genes using cytogenetic challenge assays

A major barrier to understanding the role of polymorphic DNA repair genes for environmental cancer is that the functions of variant genotypes are largely unknown. Using our cytogenetic challenge assays, we conducted an investigation to address the deficiency. Using X-rays or ultraviolet (UV) light, we irradiated blood lymphocytes from 80 nonsmoking donors to challenge the cells to repair the induced DNA damage, and we analyzed expression of chromosome aberrations (CA) specific to the inducing agents. We have genotyped polymorphic DNA repair genes preferentially involved with base excision repair (BER) and nucleotide excision repair (NER) activities (XRCC1, XRCC3, APE1, XPD) corresponding to the repair of X-ray- and UV light-induced DNA damage, respectively. We expected that defects in specific DNA repair pathways due to polymorphisms would cause corresponding increases of specific CA. From our data, XRCC1 399Gln and XRCC3 241Met were associated with significant increases in chromosome deletions compared with the corresponding homozygous wild types (18.27 1.1 vs 14.79 1.2 and 18.22 0.99 vs 14.20 1.39, respectively); XPD 312Asn and XPD 751Gln were associated with significant increases in chromatid breaks compared with wild types (16.09 1.36 vs 11.41 0.98 and 16.87 1.27 vs 10.54 0.87, respectively), p < 0.05. The data indicate that XRCC1 399Gln and XRCC3 241Met are significantly defective in BER, and the XPD 312Asn and XPD 751Gln are significantly defective in NER. In addition, the variant genotypes interact significantly, with limited overlap of the two different repair pathways.