CYP1A1 Val462 and NQO1 Ser187 polymorphisms, cigarette use, and risk for colorectal adenoma

Genic-intergenic polymorphisms of CYP1A genes and their clinical impact

The humancytochrome P450 1A (CYP1A) subfamily genes, CYP1A1 and CYP1A2, encoding monooxygenases are critically involved in biotransformation of key endogenous substrates (estradiol, arachidonic acid, cholesterol) and exogenous compounds (smoke constituents, carcinogens, caffeine, therapeutic drugs). This suggests their significant involvement in multiple biological pathways with a primary role of maintaining endogenous homeostasis and xenobiotic detoxification. Large interindividual variability exist in CYP1A gene expression and/or catalytic activity of the enzyme, which is primarily due to the existence of polymorphic alleles which encode them. These polymorphisms (mainly single nucleotide polymorphisms, SNPs) have been extensively studied as susceptibility factors in a spectrum of clinical phenotypes. An in-depth understanding of the effects of polymorphic CYP1A genes on the differential metabolic activity and the resulting biological pathways is needed to explain the clinical implications of CYP1A polymorphisms. The present review is intended to provide an integrated understanding of CYP1A metabolic activity with unique substrate specificity and their involvement in physiological and pathophysiological roles. The article further emphasizes on the impact of widely studied CYP1A1 and CYP1A2 SNPs and their complex interaction with non-genetic factors like smoking and caffeine intake on multiple clinical phenotypes. Finally, we attempted to discuss the alterations in metabolism/physiology concerning the polymorphic CYP1A genes, which may underlie the reported clinical associations. This knowledge may provide insights into the disease pathogenesis, risk stratification, response to therapy and potential drug targets for individuals with certain CYP1A genotypes.

Regulation of stress signaling pathways by protein lipoxidation

Enzymatic and non-enzymatic oxidation of unsaturated fatty acids gives rise to reactive species that covalently modify nucleophilic residues within redox sensitive protein sensors in a process called lipoxidation. This triggers adaptive signaling pathways that ultimately lead to increased resistance to stress. In this graphical review, we will provide an overview of pathways affected by protein lipoxidation and the key signaling proteins being altered, focusing on the KEAP1-NRF2 and heat shock response pathways. We review the mechanisms by which lipid peroxidation products can serve as second messengers and evoke cellular responses via covalent modification of key sensors of altered cellular environment, ultimately leading to adaptation to stress.

The Interaction of Smoking with Gene Polymorphisms on Four Digestive Cancers: A Systematic Review and Meta-Analysis

The main purpose of this study was to perform a meta-analysis to assess the interaction between smoking and nine genes (GSTM1, GSTT1, GSTP1, CYP1A1, NAT2, SULT1A1, hOGG1, XRCC1 and p53) on colorectal cancer, gastric cancer, liver cancer and oesophageal cancer. Published articles from the PubMed, ISI and EMBASE databases were retrieved. A total of 67 case-control studies or nested case-control studies were identified for the analysis. The pooled jodds ratio (OR) with 95% confidence interval (CI) was calculated using the random effect model. The overall study showed that the GSTM1 polymorphism was associated with the risk of the four digestive cancers among Asian population (OR 1.284, 95% CI: 1.122-1.470, p: 0). Subgroup analyses by cancer site showed that GSTM1 null genotype increased the gastric cancer risk in total population (OR 1.335, 95% CI: 1.145-1.556, p: 0). However, the association of GSTM1 null genotype with the oesophageal cancer risk was found in smokers (OR 1.382, 95% CI: 1.009-1.894, p:0.044), but not in non-smokers (OR 1.250, 95% CI: 0.826-1.891, p:0.290). Moreover, smokers with the CYP1A1 IIe462Val polymorphism were at an increased cancer risk in Asian population (OR=1.585, 95% CI 1.029-2.442, p: 0.037). None of the other gene-smoking interactions was observed in the above cancers. This meta-analysis reveals two potential gene-smoking interactions, one is between smoking and GSTM1 on oesophageal cancer, and the other is between smoking and CYP1A1 IIe462Val on the four cancers in Asian population. Future studies need to be conducted to verify the conclusions.

Application of a New Probabilistic Model for Mining Implicit Associated Cancer Genes from OMIM and Medline

An important issue in current medical science research is to find the genes that are strongly related to an inherited disease. A particular focus is placed on cancer-gene relations, since some types of cancers are inherited. As bio-medical databases have grown speedily in recent years, an informatics approach to predict such relations from currently available databases should be developed. Our objective is to find implicit associated cancer-genes from biomedical databases including the literature database. Co-occurrence of biological entities has been shown to be a popular and efficient technique in biomedical text mining. We have applied a new probabilistic model, called mixture aspect model (MAM) [ 48 ], to combine different types of co-occurrences of genes and cancer derived from Medline and OMIM (Online Mendelian Inheritance in Man). We trained the probability parameters of MAM using a learning method based on an EM (Expectation and Maximization) algorithm. We examined the performance of MAM by predicting associated cancer gene pairs. Through cross-validation, prediction accuracy was shown to be improved by adding gene-gene co-occurrences from Medline to cancer-gene co-occurrences in OMIM. Further experiments showed that MAM found new cancer-gene relations which are unknown in the literature. Supplementary information can be found at http://www.bic.kyotou.ac.jp/pathway/zhusf/CancerInformatics/Supplemental2006.html

CYP1A1 and GSTP1 gene variations in breast cancer: a systematic review and case-control study

In first part of this study, a systematic review was designed to explore the involvement of CYP1A1 and GSTP1 genes in breast cancerogenesis. Based on systematic review, we designed a study to screen CYP1A1 and GSTP1 genes for mutation and their possible association with breast carcinogenesis. A total of 400 individuals were collected and analyzed by PCR-SSCP. After sequence analysis of coding region of CYP1A1 we identified eleven mutations in different exons of respective gene. Among these eleven mutations, ~3 folds increased breast cancer risk was found associated with Asp82Glu mutation (OR 2.99; 95% CI 1.26-7.09), with Ser83Thr mutation (OR 2.99; 95% CI 1.26-7.09) and with Glu86Ala mutation (OR 3.18; 95% CI 1.27-7.93) in cancer patients compared to controls. Furthermore, ~4 folds increase in breast cancer risk was found associated with Asp347Glu, Phe398Tyr and 5178delT mutations (OR 3.92; 95% CI 1.35-11.3) in patients compared to controls. The sequence analysis of GSTP1 resulted in identification of total five mutations. Among these five mutations, ~3 folds increase in breast cancer risk was observed associated with 1860G>A mutation, with 1861-1876delCAGCCCTCTGGAGTGG mutation (OR 2.70; 95% CI 1.10-6.62) and with 1861C>A mutation (OR 2.97; 95% CI 1.01-8.45) in cancer patients compared to controls. Furthermore, ~5 folds increase in breast cancer risk was associated with 1883G>T mutation (OR 4.75; 95% CI 1.46-15.3) and ~6 folds increase in breast cancer risk was found associated with Iso105Val mutation (OR 6.43; 95% CI 1.41-29.3) in cancer patients compared to controls. Our finding, based on systematic review and experimental data suggest that the polymorphic CYP1A1 and GSTP1 genes may contribute to risk of developing breast cancer.

Associations between CYP1A1 rs1048943 A > G and rs4646903 T > C genetic variations and colorectal cancer risk: Proof from 26 case-control studies

Cytochrome P450 1A1 (CYP1A1) enzyme is one of the most important metabolizing enzymes responsible for the metabolism of numerous xenobiotics. Numerous individual case-control studies have investigated the associations between the CYP1A1 rs1048943 A > G and rs4646903 T > C genetic variations and colorectal cancer (CRC) risk, but the conclusions were controversial. To obtain a scientific conclusion, we performed a meta-analysis based on a total of 26 publications, including 20 studies with 8665 cases and 9953 controls on rs1048943 A > G and 19 studies with 6416 cases and 7551 controls on rs4646903 T > C, respectively. The pooled analysis indicated that rs1048943 A > G was associated with an increased risk of CRC (G vs. A: OR = 1.28, 95% CI = 1.08-1.52; GG vs. AA: OR = 1.54, 95% CI = 1.25-1.91; GA vs. AA: OR = 1.26, 95% CI = 1.00-1.60; GG/GA vs. AA: OR = 1.31, 95% CI = 1.05-1.64; GG vs. GA/AA. OR = 1.56, 95% CI = 1.26-1.91). Stratification analysis showed the association between rs1048943 A > G and CRC risk was more obvious in studies with the population-based (PB) design or high quality score. The association between rs4646903 T > C and CRC risk did not reach statistical significance in the pooled analysis as well as stratification analysis. This meta-analysis demonstrated CYP1A1 rs1048943 A > G may increase the susceptibility to CRC instead of rs4646903 T > C. This conclusion suggested CYP1A1 may contribute to the pathogenesis of CRC.

GSTM1, GSTT1, and NQO1 polymorphisms in cervical carcinogenesis

The aim of the study is to investigate the clinical significance of glutathione-S-transferase GSTM1, GSTT1, and NQO1 c.609C>T (rs1800566) genetic polymorphisms in cervical carcinogenesis. GSTM1, GSTT1, and NQO1 polymorphisms together with human papillomavirus (HPV) types were examined in a total of 192 cervical smear in exfoliated cervical cell samples using polymerase chain reaction (PCR) system and real-time polymerase chain reaction (PCR) system. The 19 patients with high-grade squamous intraepithelial lesion had statistically higher frequency of null GSTT1 genotype than 9 with low-grade squamous intraepithelial lesion (LSIL) among the 67 patients with high-risk HPV (P = 0.024). The 24 patients with HSIL had also statistically higher frequency of NQO1 (CT+TT) genotype than 14 with LSIL among the 67 patients with high-risk HPV (P = 0.024). GSTT1 null and NQO1 genotype in cervical cell samples may be associated with more severe precancerous lesions of the cervix in a Japanese population.

Clinical Significance of the NQO1 C609T Polymorphism in Non Small Cell Lung Adenocarcinoma Patients

NAD(P)H

quinone oxidoreductase 1 (NQO1) is part of the antioxidant defence system involved in detoxification. This study aimed to analyze the influence of NQO1 (C609T) genetic polymorphism in non small cell lung cancer (NSCLC)as a putative risk factor.

MATERIALS AND METHODS

Present study included 100 cases of NSCLC (adenocarcinoma) patients and 100 age and sex matched healthy controls. NQO1 (C609T) genotyping was performed by allele specific PCR for assessment of putative associations with clinical outcome and genotypes of. The association of the polymorphism with the survival of NSCLC patients' was analyzed by Kaplan-Meier method.

RESULTS

In Indian NSCLC (adenocarcinoma) patients increased risk of developing NSCLC was found to be associated with NQO1 609TT genotype [OR 3.68(0.90-14.98), RR 2.04(0.78-5.31)] for CT [OR 2.91(1.58- 5.34), RR 1.74(1.23-2.44) p= 0.0005 for CT], for CT+TT [ OR 3.26(1.82-5.82), RR 1.87(1.34-2.61) p<0.0001 for CT+TT]. A significant difference (p=0.0009) was observed in genotype distribution among cases and healthy controls. Patients with CT+TT genotype exhibited a significant poor overall survival compared with patients displaying homozygous CC genotype (p=0.03) and when survival independently compared with CC, TT and CT genotype was also found to be significantly associated (p=0.02). Overall median survival times were CT 6.0 months, TT 8.2 months, and CT + TT (6.4 months)].

CONCLUSIONS

The present study revealed that NQO1 CT, TT and CT+TT genotypes may be associated with clinical outcome and risk of developing NSCLC in the Indian population.

Calcium intake and ion transporter genetic polymorphisms interact in human colorectal neoplasia risk in a 2-phase study

BACKGROUND

The kidney-specific sodium-potassium-chloride cotransporter (NKCC2) protein encoded by solute carrier family 12 member 1 (SLC12A1) is the direct downstream effector of the inward-rectifier potassium channel (ROMK) encoded by potassium inwardly-rectifying channel, subfamily J, member 1 (KCNJ1), both of which are critical for calcium reabsorption in the kidney.

OBJECTIVE

We hypothesized that polymorphisms in KCNJ1, SLC12A1, and 7 other genes may modify the association between calcium intake and colorectal neoplasia risk.

METHODS

We conducted a 2-phase study in 1336 cases and 2891 controls from the Tennessee Colorectal Polyp Study.

RESULTS

In phase I, we identified 5 single-nucleotide polymorphisms (SNPs) that significantly interacted with calcium intake in adenoma risk. In phase II, rs2855798 in KCNJ1 was replicated. In combined analysis of phases I and II, the P values for interactions between calcium intake and rs2855798 were 1 × 10(-4) for all adenoma and 5 × 10(-3) for multiple/advanced adenoma. The highest calcium intake was not associated with risk among those with no variant allele but was significantly associated with a 41% reduced adenoma risk among those who carried at least 1 variant allele in KCNJ1. The corresponding reduction in risk of multiple or advanced adenomas was 52% among those with at least 1 variant allele. The P values for interactions between calcium intake and combined SNPs from the KCNJ1 and SLC12A1 genes were 7.5 × 10(-5) for adenoma and 9.9 × 10(-5) for multiple/advanced adenoma. The highest calcium intake was not associated with risk among those with nonvariant alleles in 2 genes but was significantly associated with a 34% reduced adenoma risk among those who carried a variant allele in 1 of the genes. The corresponding reduction in risk of multiple or advanced adenomas was 64% among those with variant alleles in both genes.

CONCLUSION

These findings, if confirmed, will be critical for the development of personalized prevention strategies for colorectal cancer.

NQO1 C609T polymorphism and colorectal cancer susceptibility: a meta-analysis

INTRODUCTION

A FEW STUDIES HAVE REPORTED AN ASSOCIATION BETWEEN NADP(H): quinine oxidoreductase 1 (NQO1) C609T polymorphism and susceptibility to colorectal cancer (CRC). However, the results were inconsistent rather than conclusive. We performed a meta-analysis to examine this association in various populations.

MATERIAL AND METHODS

Eligible articles were identified by a search of several databases up until June 30, 2013. Summary odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the strength of the association.

RESULTS

Overall, 14 case-control studies with 4,461 cases and 5,474 controls were included in this meta-analysis. The results indicated that the NQO1 C609T polymorphism was significantly associated with CRC susceptibility (summary ORs (95% CIs): 1.30 (1.07-1.59) for CT vs. CC, 1.64 (1.15-2.33) for TT vs. CC, 1.34 (1.10-1.64) for TT/CT vs. CC, and 1.43 (1.10-1.87) for TT vs. CT/CC). Subgroup analyses indicated that the T allele was significantly associated with CRC susceptibility in both Asians and Caucasians, and was also observed in high quality studies and hospital-based case-control studies. Specifically, we found a positive association between the NQO1 C609T polymorphism and CRC susceptibility in smokers, but not in non-smokers.

CONCLUSIONS

The results of this meta-analysis suggest that the NQO1 C609T polymorphism significantly contributes to increased susceptibility to CRC in both Asians and Caucasians.

Effect of NQO1 C609T polymorphism on prostate cancer risk: a meta-analysis

Background

Some studies have found that the NAD(P)H:quinone oxidoreductase 1 (NQO1) SNP609 is associated with an increased risk for several malignancies. Numerous epidemiological studies have evaluated the association between the NQO1 C609T polymorphism and the risk of prostate cancer. However, the results of these studies have been conflicting. The aim of this study was to provide a more precise estimation of its relationship with prostate cancer using a meta-analysis.

Methods

Electronic searches of several databases were conducted for all publications on the association between the NQO1 C609T polymorphism and prostate cancer before May 2013. The odds ratio (OR) and its 95% confidence interval (CI) were used for statistical analysis.

Results

A total of six studies with 717 cases and 1,794 controls were included. No significant association was found between the NQO1 C609T polymorphism and prostate cancer risk in the total population analysis. In subgroup meta-analysis by ethnicity, a positive association was found in an Asian subgroup (T versus C, OR 1.337, 95% CI 1.014–1.763, P=0.040; TT + CT versus CC, OR 1.419, 95% CI 1.053–1.913, P=0.021). However, no significant association in any genetic models was observed in Caucasians.

Conclusion

This meta-analysis showed that the NQO1 SNP609 T allele might be a risk factor for prostate cancer in Asians. However, this result should be verified by additional population-based studies with large sample sizes.

Association between NQO1 C609T polymorphism and prostate cancer risk

Published studies on the association between NQO1 C609T polymorphism and prostate cancer risk have yielded conflicting results. Thus, a systemic review and meta-analysis of published studies were performed to assess the possible association. All eligible studies of NQO1 C609T polymorphism and prostate cancer risk were collected from the PubMed and the Cochrane Library. Statistical analyses were performed by Review Manage 5.0 and Stata 11.0. A total of 6 available studies were considered in the present meta-analysis, with 717 cases and 1,794 controls. When all groups were pooled, there was no evidence that NQO1 C609T had significant association with prostate cancer under additive, recessive, dominant, and allelic models. When stratifying for the race, our analysis suggested that NQO1 C609T was associated with prostate cancer risk in Asians when using dominant (TT + CT vs CC: OR = 1.419, 95 % CI = 1.053 - 1.913, P = 0.021) and allelic models (OR = 1.337, 95 % CI = 1.014 - 1.763, P = 0.040) to analyze the data. However, no significant associations were found in Caucasians. This meta-analysis suggested that NQO1 C609T polymorphism most likely contributes to increased susceptibility to prostate cancer in the Asians. Further large-scale and well-designed case-control studies are necessary to validate the risk identified in the present meta-analysis.

Genetic variations in the xenobiotic-metabolizing enzymes CYP1A1, CYP1A2, CYP2C9, CYP2C19 and susceptibility to colorectal cancer among Turkish people

Cytochrome P450 (CYP) enzymes are genetically polymorphic and play key roles in the metabolism of xenobiotics. Colorectal cancer (CRC) is one of the most common malignant tumors in Turkey as well as in the world. In this study, it was aimed both to evaluate the effects of CYP variants on the susceptibility to CRC and to predict the individual response of the Turkish people to xenobiotics metabolized by CYP enzymes. For that, we assessed the association of CYP1A1, CYP1A2, CYP2C9, and CYP2C19 polymorphisms in patients with CRC in the Turkish population through a case-control study. Distributions of the variants were determined in 104 patients with CRC and 183 healthy volunteers. As results, CYP1A1 6235T/C was significantly associated with CRC risk (odds ratio [OR]=2.53; 95% confidence interval [CI]=0.99-6.45; p=0.046). In a haplotype-based analysis, CYP1A1 haplotype C6235-A2455 might be associated with the development of CRC (OR=2.70; 95% CI=0.58-5.90; p=0.046). We believe that the findings are the first results of CYP allele distributions in the Turkish population and provide an understanding of the epidemiological studies that correlate therapeutic approaches and etiology of CRC especially in Turkish patients.

Influence of dietary fat type on benzo(a)pyrene [B(a)P] biotransformation in a B(a)P-induced mouse model of colon cancer

In the US alone, around 60,000 lives/year are lost due to colon cancer. Diet and environment have been implicated in the development of sporadic colon tumors. The objective of this study was to determine how dietary fat potentiates the development of colon tumors through altered B(a)P biotransformation, using the Adenomatous polyposis coli with Multiple intestinal neoplasia mouse model. Benzo(a)pyrene was administered to mice through tricaprylin, and unsaturated (USF; peanut oil) and saturated (SF; coconut oil) fats at doses of 50 and 100 μg/kg via oral gavage over a 60-day period. Blood, colon, and liver were collected at the end of exposure period. The expression of B(a)P biotransformation enzymes [cytochrome P450 (CYP)1A1, CYP1B1 and glutathione-S-transferase] in liver and colon were assayed at the level of protein, mRNA and activities. Plasma and tissue samples were analyzed by reverse phase high-performance liquid chromatography for B(a)P metabolites. Additionally, DNA isolated from colon and liver tissues was analyzed for B(a)P-induced DNA adducts by the (32)P-postlabeling method using a thin-layer chromatography system. Benzo(a)pyrene exposure through dietary fat altered its metabolic fate in a dose-dependent manner, with 100 μg/kg dose group registering an elevated expression of B(a)P biotransformation enzymes, and greater concentration of B(a)P metabolites, compared to the 50 μg/kg dose group (P<.05). This effect was more pronounced for SF group compared to USF group (P<.05). These findings establish that SF causes sustained induction of B(a)P biotransformation enzymes and extensive metabolism of this toxicant. As a consequence, B(a)P metabolites were generated to a greater extent in colon and liver, whose concentrations also registered a dose-dependent increase. These metabolites were found to bind with DNA and form B(a)P-DNA adducts, which may have contributed to colon tumors in a subchronic exposure regimen.

CYP1A1, GSTM1, GSTT1 and NQO1 polymorphisms and colorectal adenomas in Japanese men

AIM: To investigate the role of functional genetic polymorphisms of metabolic enzymes of tobacco carcinogens in the development of colorectal adenomas.

METHODS: The study subjects were 455 patients with colorectal adenomas and 1052 controls with no polyps who underwent total colonoscopy in a preretirement health examination at two Self Defense Forces hospitals. The genetic polymorphisms studied were CYP1A1*2A (rs 4646903), CYP1A1*2C (rs 1048943), GSTM1 (null or non-null genotype), GSTT1 (null or non-null genotype) and NQO1 C609T (rs 1800566). Genotypes were determined by the polymerase chain reaction (PCR)-restriction fragment length polymorphism or PCR method using genomic DNA extracted from the buffy coat. Cigarette smoking and other lifestyle factors were ascertained by a self-administered questionnaire. The associations of the polymorphisms with colorectal adenomas were examined by means of OR and 95%CI, which were derived from logistic regression analysis. Statistical adjustment was made for smoking, alcohol use, body mass index and other factors. The gene-gene interaction and effect modification of smoking were evaluated by the likelihood ratio test.

RESULTS: None of the five polymorphisms showed a significant association with colorectal adenomas, nor was the combination of GSTM1 and GSTT1. A borderline significant interaction was observed for the combination of CYP1A1*2C and NQO1 (P = 0.051). The OR associated with CYP1A1*2C was significantly lower than unity among individuals with the NQO1 609CC genotype. The adjusted OR for the combination of the CYP1A1*2C allele and NQO1 609CC genotype was 0.61 (95%CI: 0.42-0.91). Although the interaction was not statistically significant (P = 0.24), the OR for individuals carrying the CYP1A1*2C allele and GSTT1 null genotype decreased significantly compared with those who had neither CYP1A1*2C allele nor GSTT1 null genotype (adjusted OR: 0.69, 95%CI: 0.49-0.97). Smoking did not modify the associations of the individual polymorphisms with colorectal adenomas. There was no measurable effect modification of smoking even regarding the combination of the genetic polymorphisms of the phase I and phase II enzymes.

CONCLUSION: Combination of the CYP1A1*2C and NQO1 609CC genotypes was associated with a decreased risk of colorectal adenomas regardless of smoking status.

NQO1 609C>T polymorphism interaction with tobacco smoking and alcohol drinking increases colorectal cancer risk in a Chinese population

BACKGROUND

NAD (P)H:quinone oxidoreductase (NQO1) catalyzes the activation of some environmental procarcinogens present in tobacco smoke or the diet. We conducted a hospital-based case-control study to evaluate the potential association between NQO1 609C>T polymorphisms and colorectal cancer risk in a Chinese population.

METHODS

The study population comprised 672 histologically confirmed colorectal cancer patients and 672 frequency-matched control subjects without cancer or systemic illness. We used PCR restriction fragment length polymorphism-based methods for genotyping analyses and unconditional logistic regression model for statistical evaluations.

RESULTS

The risk of colorectal cancer increased with the level of smoking and decreased with the consumption of tea, fresh fruits, and vegetables. In addition, we found that the NQO1 609 CT and TT genotypes were associated with an increased risk of colorectal cancer (CT: adjusted OR=2.02, 95% CI=1.55-2.57; TT: adjusted OR=2.51, 95% CI=1.82-3.47), compared with the CC genotype. Moreover, NQO1 609C>T appeared to have a multiplicative joint effect with both tobacco smoking and alcoholic drinking (P for multiplicative interactions were 0.0001 and 0.013, respectively) on colorectal cancer risk.

CONCLUSION

Our findings suggest that the NQO1 609C>T polymorphism plays an important role in the development of colorectal cancer in the Chinese population, which is strengthened by alcohol drinking or tobacco smoking.

Association of NQO1 rs1800566 polymorphism and the risk of colorectal cancer: a meta-analysis

INTRODUCTION

NAD(P)H:quinone oxidoreductase 1 (NQO1) rs1800566 polymorphism is found to have a lower enzymatic activity, which may result in increased incidence of several kinds of carcinomas including colorectal cancer. Results from published studies on the association of NQO1 rs1800566 genetic polymorphism with the risk of colorectal cancer are inconsistent. We performed a meta-analysis to summarize the possible association.

MATERIALS AND METHODS

All eligible published studies were searched from PubMed and Elsevier ScienceDirect. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were analyzed for additive, dominant, and recessive models to assess the association using fixed- or random-effect model.

RESULTS

We identified 12 case-control studies that include 5,525 cases and 6,272 controls for the present meta-analysis. Significant associations between NQO1 rs1800566 genetic polymorphism and risk of colorectal cancer were observed in additive (OR = 1.09, 95% CI = 1.02-1.16, p = 0.009) and dominant models (OR = 1.12, 95% CI = 1.04-1.21, p = 0.004 for TT + CT vs. CC). Moreover, in the subgroup analysis based on ethnicity, significant associations were observed in Caucasians but not in Asians.

CONCLUSIONS

This meta-analysis provided evidence that NQO1 rs1800566 genetic polymorphism was associated with increased risk of colorectal cancer and that the T allele probably acts as an important risk factor.

Contribution of NAD(P)H quinone oxidoreductase 1 (NQO1) Pro187Ser polymorphism and risk of colorectal adenoma and colorectal cancer in Caucasians: a meta-analysis

BACKGROUND AND AIMS

The effects of polymorphism of NAD(P)H quinone oxidoreductase 1 (NQO1 Pro187Ser, rs1800566) on the risks of colorectal adenoma and cancer have been widely studied and results remain controversial. Therefore, the aim of this meta-analysis was to quantitatively assess the relationships.

METHODS

Databases of Medline, Embase and Wanfang were retrieved until May 15, 2011. Pooled odds ratio (OR) and 95% confidence interval (95% CI) as effect sizes were calculated by using fixed- or random-effect model. Cochrane Q-test was used to explore between-study heterogeneity; p <0.10 indicated statistical significance.

RESULTS

A total of 12 case-control studies with 11,700 individuals (including 5528 cases and 6172 controls) were included in this meta-analysis. Of these studies, four studies conducted in Caucasian populations were for colorectal adenoma, and eight studies were for colorectal cancer. NQO1 187Ser allele was significantly associated with increased risk of colorectal adenoma in co-dominant and dominant comparison models (OR = 1.07, 95% CI = 1.04-1.32 for ProSer vs. ProPro and OR = 1.19, 95% CI = 1.06-1.33 for Ser carries vs. ProPro), without between-study heterogeneity. Overall, NQO1 Pro187Ser was not associated with risk of colorectal cancer, without between-study heterogeneity. Subgroup analyses indicated that Ser allele was significantly associated with increased risk of colorectal cancer for Caucasians (OR = 1.14, 95% CI = 1.00-1.30 for ProSer vs. ProPro and OR = 1.16, 95% CI = 1.02-1.31 for Ser carries vs. ProPro).

CONCLUSIONS

This meta-analysis suggested that Ser allele of NQO1 Pro187Ser significantly contributed to the increased risks of colorectal adenoma and cancer in Caucasians.

A functional NQO1 609C>T polymorphism and risk of gastrointestinal cancers: a meta-analysis

Background

The functional polymorphism (rs1800566) in the NQO1 gene, a 609C>T substitution, leading to proline-to-serine amino-acid and enzyme activity changes, has been implicated in cancer risk, but individually published studies showed inconclusive results.

Methodology/Principal Findings

We performed a meta-analysis of 20 publications with a total of 5,491 cases and 5,917 controls, mainly on gastrointestinal (GI) cancers. We summarized the data on the association between the NQO1 609C>T polymorphism and risk of GI cancers and performed subgroup analyses by ethnicity, cancer site, and study quality. We found that the variant CT heterozygous and CT/TT genotypes of the NQO1 609 C>T polymorphism were associated with a modestly increased risk of GI cancers (CT vs. CC: OR = 1.10, 95% CI = 1.01 – 1.19, P_{heterogeneity} = 0.27, I² = 0.15; CT/TT vs. CC: OR = 1.11, 95%CI = 1.02 – 1.20, P_{heterogeneity} = 0.14; I² = 0.27). Following further stratified analyses, the increased risk was only observed in subgroups of Caucasians, colorectal cancer in Caucasians, and high quality studies.

Conclusions

This meta-analysis suggests that the NQO1 609T allele is a low-penetrance risk factor for GI cancers. Although the effect on GI cancers may be modified by ethnicity and cancer sites, small sample seizes of the subgroup analyses suggest that further larger studies are needed, especially for non-colorectal GI cancers in Caucasians and GI cancers in Asians.

System review and metaanalysis of the relationships between five metabolic gene polymorphisms and colorectal adenoma risk

The relationships between some metabolic (including EPHX1, GSTs and NQO1) gene polymorphisms and colorectal adenoma (CRA) risk have been commonly studied, and no conclusions are available up to now. Therefore, we quantitatively studied the relationships by a metaanalysis. The databases of Medline and Embase were retrieved updated to June 15th, 2011. Crude or adjusted odds ratio (crude OR or adjusted OR) and 95% confidence interval (95%CI) were calculated to present the strength of the associations. Overall, nine case-control studies for EPHX1 Tyr113His and His139Arg, five case-control studies for GSTM1, four studies for GSTP1 Ile105Val, two studies for GSTP1 Ala114Val, six studies for GSTT1 and four studies for NQO1 Pro187Ser were included in this metaanalysis. The results of combined analyses indicated that EPHX1 Tyr113His and His139Arg, GSTT1, GSTM1, GSTP1 Ile105Val and Ala114Val were not associated with CRA risk [crude OR (95%CI): 0.98 (0.90-1.07) and P ( z-test) = 0.65 for EPHX1 His carriers vs. Tyr/Tyr; 1.05 (0.97-1.15) and P ( z-test) = 0.21 for EPHX1 Arg carriers vs. His/His; 1.05 (0.92-1.20) and P ( z-test) = 0.47 for GSTT1 Null vs. Present; 1.01 (0.90-1.13) and P ( z-test) = 0.90 for GSTM1 Null vs. Present; 1.04 (0.92-1.17) and P ( z-test) = 0.56 for G carriers vs. AA for GSTP1 Ile105Val; 0.88 (0.70-1.11) and P ( z-test) = 0.28 for T carriers vs. CC for GSTP1 Ala114Val]. In contrast, Ser allele of NQO1 Ser187Pro might be a modest risk factor for CRA development [1.19 (1.06-1.33) and P ( z-test) = 0.003 for Ser carriers vs. Pro/Pro]. To get more precise evidences, adjusted ORs (95%CI) for EPHX1 Tyr113His, His139Arg, GSTP1 Ile105Val and NQO1 Ser187Pro were also calculated based on adjusted ORs (95%CIs) reported in primary studies. The results still indicated that EPHX1 Tyr113His, His139Arg and GSTP1 Ile105Val were not associated with CRA risk except for NQO1 Ser187Pro. When subgroup analyses were performed for population-based case-control studies or studies in HWE for EPHX1 Tyr113His and His139Arg, and NQO1 Ser187Pro polymorphisms, the results were persistent. Although with modest limitations and biases, this metaanalysis suggests that EPHX1 Tyr113His and His139Arg, GSTT1, GSTM1, GSTP1 Ile105Val and Ala114Val polymorphisms may be not risk factors for CRA development, while Ser allele of NQO1 Ser187 Pro may be a modest risk factor for CRA development, and may be used with other genetic markers for screening CRA in the future.

Genetic variation in the bioactivation pathway for polycyclic hydrocarbons and heterocyclic amines in relation to risk of colorectal neoplasia

Animal work implicates chemical carcinogens, such as polycyclic aromatic hydrocarbons (PAHs) and heterocyclic aromatic amines (HAAs) as contributing to the development of colorectal cancer (CRC). The epidemiologic evidence, however, remains inconsistent possibly due to intra-individual variation in bioactivation of these compounds. We conducted a case-control study of colorectal adenoma (914 cases, 1185 controls) and CRC (496 cases, 607 controls) among Japanese Americans, European Americans and Native Hawaiians to investigate the association of genetic variation in the PAH and HAA bioactivation pathway (CYP1A1, CYP1A2, CYP1B1, AHR and ARNT) identified through sequencing with risk of colorectal neoplasia, as well as their interactions with smoking and intakes of red meat and HAAs. The A allele for ARNT rs12410394 was significantly inversely associated with CRC [odds ratios (ORs) and 95% confidence intervals (CIs) for GG, AG and AA genotypes: 1.00, 0.66 (0.48-0.89), 0.54 (0.37-0.78), P(trend) = 0.0008] after multiple comparison adjustment. CYP1A2 rs11072508 was marginally significantly associated with CRC, where each copy of the T allele was associated with reduced risk (OR: 0.72, 95% CI: 0.58-0.88, P(trend) = 0.0017). No heterogeneity of genetic effects across racial/ethnic groups was detected. In addition, no significant interaction was observed after adjusting for multiple testing between genetic variants and pack-years of smoking, intake of red meat or HAAs (PhIP, MeIQx, Di-MeIQx or total HAAs) or NAT2 genotype (Rapid versus Slow or Intermediate). This study suggests that the genomic region around ARNT rs12410394 may harbor variants associated with CRC.

In utero tobacco exposure epigenetically modifies placental CYP1A1 expression

The metabolic pathways used by higher-eukaryotic organisms to deal with potentially carcinogenic xenobiotic compounds from tobacco smoke have been well characterized. Carcinogenic compounds such as polycyclic aromatic hydrocarbons are metabolized sequentially in 2 phases: in phase I, CYP1A1 catalyzes conversion into harmful hydrophilic DNA adducts, whereas in phase II, GSTT1 enables excretion via conjugation into polar electrophiles. In an effort to understand susceptibility to in utero tobacco exposure, we previously characterized known metabolic functional polymorphisms and demonstrated that although deletion of fetal GSTT1 significantly modified birth weight in smokers, no polymorphism fully accounted for fetal growth restriction. Because smoking up-regulates CYP1A1 expression, we hypothesized that nonallelic (epigenetic) dysregulation of placental CYP1A1 expression via alterations in DNA methylation (meCpG) may further modify fetal growth. In the present article, we compared placental expression of multiple CYP family members among gravidae and observed significantly increased CYP1A1 expression among smokers relative to controls (4.4-fold, P < .05). To fully characterize CYP1A1 meCpG status, bisulfite modification and sequencing of the entire proximal 1-kilobase promoter (containing 59 CpG sites) were performed. CpG sites immediately proximal to the 5′-xenobiotic response element transcription factor binding element were significantly hypomethylated among smokers (55.6% vs 45.9% meCpG, P = .027), a finding that uniquely correlated with placental gene expression (r = 0.737, P = .007). Thus, in utero tobacco exposure significantly increases placental CYP1A1 expression in association with differential methylation at a critical xenobiotic response element.

Polymorphisms in xenobiotic metabolizing enzymes and diet influence colorectal adenoma risk

OBJECTIVES

We have earlier shown that diet and xenobiotic metabolizing enzyme genotypes influence colorectal cancer risk, and now investigate whether similar associations are seen in patients with premalignant colorectal adenomas (CRA), recruited during the pilot phase of the Scottish Bowel Screening Programme.

METHODS

Nineteen polymorphisms in 13 genes [cytochrome P450 (P450), glutathione S-transferase (GST), N-acetyl transferase, quinone reductase (NQ01) and microsomal epoxide hydrolase (EPHX1) genes] were genotyped using multiplex PCR or Taqman-based allelic discrimination assays and analyzed in conjunction with diet, assessed by food frequency questionnaire, in a case-control study [317 CRA cases (308 cases genotyped), 296 controls]. Findings significant at a nominal 5% level are reported.

RESULTS

CRA risk was inversely associated with fruit (P=0.02, test for trend) and vegetable (P=0.001, test for trend) consumption. P450 CYP2C9*3 heterozygotes had reduced CRA risk compared with homozygotes for the reference allele [odds ratio (OR): 0.60; 95% confidence interval (CI): 0.36-0.99], whereas CYP2D6*4 homozygotes (OR: 2.72; 95% CI: 1.18-6.27) and GSTM1 'null' individuals (OR: 1.43; 95% CI: 1.04-1.98) were at increased risk. The protective effect of fruit consumption was confined to GSTP1 (Ala114Val) reference allele homozygotes (OR: 0.49; 95% CI: 0.34-0.71, P=0.03 for interaction). CRA risk was not associated with meat consumption, although a significant interaction between red meat consumption and EPHX1 (His139Arg) genotype was noted (P=0.02 for interaction).

CONCLUSION

We report the novel associations between P450 genotype and CRA risk, and highlight the risk association with GSTM1 genotype, common to our CRA and cancer case-control series. In addition, we report a novel modifying influence of GSTP1 genotype on dietary chemoprevention. These novel findings require independent confirmation.

Cigarette smoking, genetic polymorphisms and colorectal cancer risk: the Fukuoka Colorectal Cancer Study

Background

It is uncertain whether smoking is related to colorectal cancer risk. Cytochrome P-450 CYP1A1, glutathione-S-transferase (GST) and NAD(P)H:quinone oxidoreductase 1 (NQO1) are important enzymes in the metabolism of tobacco carcinogens, and functional genetic polymorphisms are known for these enzymes. We investigated the relation of cigarette smoking and related genetic polymorphisms to colorectal cancer risk, with special reference to the interaction between smoking and genetic polymorphism.

Methods

We used data from the Fukuoka Colorectal Cancer Study, a population-based case-control study, including 685 cases and 778 controls who gave informed consent to genetic analysis. Interview was conducted to assess lifestyle factors, and DNA was extracted from buffy coat.

Results

In comparison with lifelong nonsmokers, the odds ratios (OR) of colorectal cancer for <400, 400-799 and ≥800 cigarette-years were 0.65 (95% confidence interval [CI], 0.45-0.89), 1.16 (0.83-1.62) and 1.14 (0.73-1.77), respectively. A decreased risk associated with light smoking was observed only for colon cancer, and rectal cancer showed an increased risk among those with ≥400 cigarette-years (OR 1.60, 95% CI 1.04-2.45). None of the polymorphisms under study was singly associated with colorectal cancer risk. Of the gene-gene interactions studied, the composite genotype of CYP1A1*2A or CYP1A1*2C and GSTT1 polymorphisms was associated with a decreased risk of colorectal cancer, showing a nearly statistically significant (P_interaction = 0.06) or significant interaction (P_interaction = 0.02). The composite genotypes of these two polymorphisms, however, showed no measurable interaction with cigarette smoking in relation to colorectal cancer risk.

Conclusions

Cigarette smoking may be associated with increased risk of rectal cancer, but not of colon cancer. The observed interactions between CYP1A1 and GSTT1 polymorphisms warrant further confirmation.

Pharmacogenomics of maternal tobacco use: metabolic gene polymorphisms and risk of adverse pregnancy outcomes

OBJECTIVE

To assess whether functional maternal or fetal genotypes along well-characterized metabolic pathways (ie, CYP1A1, GSTT1, and CYP2A6) may account for varying associations with adverse outcomes among pregnant women who smoke.

METHODS

DNA samples from 502 smokers and their conceptuses, alongside women in a control group, were genotyped for known functional allelic variants of CYP1A1 (Ile462Val AA>AG/GG), GSTT1(del), and CYP2A6 (Lys160His T>A). Modification of the association between smoking and outcome by genotype was evaluated. Outcomes included birth weight, pregnancy loss, preterm birth, small for gestational age, and a composite outcome composed of the latter four components plus abruption.

RESULTS

No interaction between maternal or fetal genotype of any of the polymorphisms and smoking could be demonstrated. In contrast, the association of smoking with gestational age-adjusted birth weight (birth weight ratio) was modified by fetal GSTT1 genotype (P for interaction=.02). Fetuses with GSTT1(del) had a mean birth weight reduction among smokers of 262 g (P=.01), whereas in fetuses without the GSTT1(del) the effect of tobacco exposure was nonsignificant (mean reduction 87 g, P=.16). After adjusting for confounding, results were similar.

CONCLUSION

Fetal GSTT1 deletion significantly and specifically modifies the effect of smoking on gestational age-corrected birth weight.

Genetic polymorphism of metabolic enzymes P450 (CYP) as a susceptibility factor for drug response, toxicity, and cancer risk

The polymorphic P450 (CYP) enzyme superfamily is the most important system involved in the biotransformation of many endogenous and exogenous substances including drugs, toxins, and carcinogens. Genotyping for CYP polymorphisms provides important genetic information that help to understand the effects of xenobiotics on human body. For drug metabolism, the most important polymorphisms are those of the genes coding for CYP2C9, CYP2C19, CYP2D6, and CYP3A4/5, which can result in therapeutic failure or severe adverse reactions. Genes coding for CYP1A1, CYP1A2, CYP1B1, and CYP2E1 are among the most responsible for the biotransformation of chemicals, especially for the metabolic activation of pre-carcinogens. There is evidence of association between gene polymorphism and cancer susceptibility. Pathways of carcinogen metabolism are complex, and are mediated by activities of multiple genes, while single genes have a limited impact on cancer risk. Multigenic approach in addition to environmental determinants in large sample studies is crucial for a reliable evaluation of any moderate gene effect. This article brings a review of current knowledge on the relations between the polymorphisms of some CYPs and drug activity/toxicity and cancer risk.

Environmental influences on epigenetic profiles

Studies of environmental challenges, such as hazardous air pollutants, nonmutagenic toxins, diet choice, and maternal behavioral patterns, reveal changes in gene expression patterns, DNA methylation, and histone modifications that are in causal association with exogenous exposures. In this article we summarize some of the recent advances in the field of environmental epigenetics and highlight seminal studies that implicate in utero exposures as causative agents in altering not only the epigenome of the exposed gestation, but that of subsequent generations. Current studies of the effects of maternal behavior, exposure to environmental toxins, and exposure to maternal diet and an altered gestational milieu are summarized.

Traumatic brain injury induces the activation of the Nrf2-ARE pathway in the lung in rats

BACKGROUND

Acute lung injury (ALI) is a frequent but poorly understood complication of traumatic brain injury (TBI). The Nrf2-ARE pathway has been proved to be essential for protection against diffuse inflammation and oxidative damage, which are both involved in ALI following TBI. However, whether the Nrf2-ARE pathway is activated after TBI in the lung hasn't been studied.

METHODS AND PROCEDURES

In the present study, the nuclear Nrf2 protein level was detected by Western blot and the mRNA levels of heme oxygenase-1 (HO-1) and NAD(P)H:quinone oxidoreductase-1 (NQO1), two Nrf2-regulated gene products, were determined by RT-PCR at 24 hours after TBI. In addition, the expression of Nrf2 and HO-1 was localized by immunohistochemical study.

MAIN OUTCOMES AND RESULTS

After TBI, the nuclear Nrf2 protein level in the lung was significantly increased and the mRNA levels of both HO-1 and NQO1 were also up-regulated. Moreover, immunohistochemical study showed that both Nrf2 and HO-1 were mainly localized in tracheobronchial epithelium and alveolar macrophages.

CONCLUSION

These results suggest that the Nrf2-ARE pathway is activated in the lung after TBI.

NQO1 and NFE2L2 polymorphisms, fruit and vegetable intake and smoking and the risk of colorectal adenomas in an endoscopy-based population

Both environment and genetics contribute to the pathogenesis and prevention of colorectal neoplasia.

NAD(P)H

quinone oxidoreductase (NQO1) is a detoxification enzyme that is polymorphic and inducible. We investigated interactions between lifestyle factors and polymorphisms in NQO1 and its key regulatory transcription factor NFE2L2 in colorectal adenoma risk. The NQO1 c.609C>T and g.-718A>G and NFE2L2 g.-650C>A, g.-684G>A and g.-686A>G polymorphisms were determined among 740 Dutch adenoma cases and 698 endoscopy-based controls. Dietary intake was assessed by food frequency questionnaire, other lifestyle information by questionnaire. The NQO1 609CT genotype was associated with a higher adenoma risk (OR 1.27, 95% CI 1.00-1.62) compared with the 609CC genotype, whereas the 609TT genotype was not (OR 1.03, 95% CI 0.56-1.88). The higher risk with the NQO1 609CT-genotype was seen among smokers (OR 1.96, 95% CI 1.40-2.76), but not among nonsmokers (OR 0.91, 95% CI 0.62-1.35; interaction p = 0.030). Fruit and vegetable consumption did not protect smokers from adenomas and did not interact with the NQO1 609C>T polymorphism or the NFE2L2 polymorphisms. A higher adenoma risk seen with high fruit and vegetable consumption among NQO1 -718GG genotypes was absent among -718GA genotypes (interaction p = 0.071). Gene-gene interactions were observed between the NQO1 609C>T and NFE2L2 -686A>G polymorphisms (interaction p = 0.056) and between the NQO1 -718 G>A and NFE2L2 -650C>A polymorphisms (interaction p = 0.013).

IN CONCLUSION

the NQO1 609CT genotype is associated with increased adenoma risk among smokers, which is not diminished by high fruit and vegetable consumption. The observed gene-gene interactions may point to a role for NFE2L2 polymorphisms in NQO1-related adenoma formation.

Relationship between Genetic Polymorphism of CYP1A1 at Codon 462 (Ile462Val) in Colorectal Cancer

Aims and background

The enzyme cytochrome P450 plays an important role in the metabolization and detoxification of various compounds. CYP1A1 is a polymorphic enzyme and some of its alleles have been correlated with an increased risk of developing various types of cancer. The aim of this study was to investigate the incidence of the polymorphism A→G (Ile462Val, exon 7) in colorectal cancer patients and the correlation of this polymorphism with others risk factors.

Patients and methods

114 Brazilian patients with colorectal cancer were matched by age and sex to 114 healthy individuals. DNA was extracted from peripheral blood and the genotypes of the polymorphisms were assessed by PCR-restriction fragment length polymorphism.

Results

In the case group 64 subjects were male, 53 were alcohol users and 68 were smokers. In the control group 61 were male, 67 were alcohol users and 53 smokers. There were 14 subjects with wild-type homozygous A/A, 97 with heterozygous A/G, and 3 with homozygous mutated G/G in the cancer group versus 81 subjects with wild-type homozygous A/A and 33 with heterozygous A/G in the control group. The presence of the G allele (OR 5.14, 95%CI 3.15–10.80) was associated with an increased risk of colorectal cancer (p=0.001). The prevalence of smokers was higher in the cancer group (p=0.047, OR 1.71, 95%CI 1.03–3.11).

Conclusion

These results suggest a positive association between the A→G polymorphism and the risk of colorectal cancer. In addition, smoking was also a colorectal cancer risk. We did not find any correlation between this polymorphism and sex, grade of differentiation, stage, or evolution of the disease.

Cytotoxicity and gene expression profiles in cell cultures exposed to whole smoke from three types of cigarettes

The purpose of this study was to evaluate and compare the cytotoxicity and gene expression profiles in cell cultures exposed to whole smoke generated from a full flavor cigarette (Test 1), a low tar cigarette (Test 2), and an ultra-low tar cigarette (Test 3). In addition, a reference cigarette 2R4F was evaluated for cytotoxicity. Neutral red (NR) cytotoxicity assay was performed to determine relative cell death at each exposure concentration (n = 6). LC(50) was generated using wet total particular matter (WTPM), cigarette number, or nicotine concentrations. The overall order of cytotoxicity was Test 1 >> 2R4F approximately Test 2 > Test 3. Cell culture samples were collected for RNA extraction at WTPM concentrations of each cigarette that gave similar nicotine concentrations. Affymetrix mouse whole genome 430 2.0 array was used to characterize the gene expression profiles for each cigarette. A total of 598 genes in Test 1, 176 genes in Test 2, and 234 genes in Test 3 samples were differentially expressed compared to the concurrent sham controls. The major biological processes associated with the changed genes in Test 1 samples were down-regulated DNA replication and cell proliferation; the same biological processes were much less affected in Test 2 and Test 3 samples. The common findings in all three cigarettes types were increased glutathione biosynthesis/consumption and inflammatory response, which are known biological effects caused by smoke exposure. The most significantly up-regulated genes were CYP1A1, GSTs, Hmox1, and Procr in smoke-exposed samples, which are either related to well-studied mechanisms of smoke exposure-related diseases or potential new biomarkers for assessing and monitoring biological effects of cigarette smoke exposure in vivo and in smokers. In summary, both the NR cytotoxicity assay and gene expression profiling were able to differentiate the three types of test cigarettes, and the results demonstrated reduced biological effects for the Test 2 and Test 3 cigarettes compared to the Test 1 cigarette in BALB/c-3T3 Cells.

A NAD(P)H:quinone oxidoreductase 1 polymorphism is a risk factor for human colon cancer

Colon cancer is one of the most common cancers in North America and generally develops from colonic epithelial cells following initiation by carcinogens. We have shown that the phase II detoxifying enzyme, NAD(P)H:quinone oxidoreductase 1 (NQO1) contributes to the inhibition of carcinogen-induced colon cancer in rats at both the initiation and postinitiation stages. An inactivating polymorphism at base 609 of the NQO1 gene, (609)C (NQO1 *1) --> (609)T (NQO1 *2), occurs at high frequency in the human population. Thus, we carried out a case-control study to determine if this polymorphism is associated with an increased risk of developing colon cancer. A total of 298 patients with colon cancer and 349 healthy controls matched for age, gender, and ethnic origin were enrolled in the study. There was an increased incidence of the NQO1 *2/*2 genotype in patients with colon cancer, with a gender and age-adjusted odds ratio of 2.68 (95% confidence intervals, 1.14-6.28). However, the incidence of the NQO1 *1/*2 genotype was not increased in patients with colon cancer compared with controls. When the patient and control groups were stratified by tobacco and alcohol use, the incidences of the NQO1 *2/*2 genotype were increased in patients with colon cancer for tobacco and alcohol users and nonusers, suggesting that there is no interaction between the NQO1 base 609 polymorphism and tobacco or alcohol use. These results strongly suggest that NQO1 plays a significant role in preventing the development of colon cancer, and individuals with an NQO1 *2/*2 genotype are at an increased risk of developing this disease.

Colorectal cancer and genetic polymorphisms of CYP1A1, GSTM1 and GSTT1: a case-control study in the Grampian region of Scotland

Cytochrome P-450 CYP1A1 is involved in the metabolism of polycyclic aromatic hydrocarbons (PAHs) that are derived from meat intake and tobacco smoking. Expression of the CYP1A1 gene is induced by compounds present in cruciferous vegetables. The glutathione S-transferases play a central role in the detoxification of carcinogens, including PAHs. We investigated the association between colorectal cancer and three variants (CYP1A1*2A, CYP1A1*2C, CYP1A1*4) of the CYP1A1 gene, and homozygosity for the null deletion of the GSTM1 and GSTT1 genes, and the joint effects of these genotypes and smoking, meat intake and intake of green leafy vegetables in a population-based study of 264 cases and 408 controls in Northeast Scotland. There was an inverse association with the CYP1A1*4 (m4) variant (OR 0.3, 95% CI 0.13-0.70). The OR for the CYP1A1*2C (m2) variant was 1.3 (95% CI 0.59-2.91), which is similar to a combined estimate for previous studies (OR 1.2, 95% CI 0.95-1.41). We observed no association with the CYP1A1*2A (m1) variant, or the GSTM1 and GSTT1 polymorphisms. Significant interactions between all 3 CYP1A1 variants and meat intake, and between the m1 and m2 variants and intake of green leafy vegetables, were observed. There was no evidence of interaction between CYP1A1 and smoking, and no evidence of interaction between the GSTM1 or GSTT1 polymorphisms and smoking, meat intake, green leafy vegetable intake, CYP1A1 variants or each other.

Tobacco smoking and colorectal hyperplastic and adenomatous polyps

Colorectal adenomas and possibly some hyperplastic polyps are precursors of colorectal cancer. Tobacco use is associated in epidemiologic studies with these polyps, although links between smoking and colorectal cancer are less consistent. To characterize the role of tobacco in early colorectal carcinogenesis, we compared tobacco use among 4,383 subjects with histologically verified benign (hyperplastic or adenomatous) polyps of the distal colon (descending colon, sigmoid, and rectum) with tobacco use among 33,667 subjects who were endoscopy negative for distal colon tumors, in the screening arm of the Prostate, Lung, Colorectal, and Ovarian Trial, a randomized trial of flexible sigmoidoscopy. Risks, estimated by the odds ratio (OR), associated with current cigarette use were OR = 4.4 [95% confidence interval (95% CI), 3.7-5.2] for hyperplastic polyps only, OR = 1.8 (95% CI, 1.5-2.1) for adenomas only, and OR = 6.2 (95% CI, 4.7-8.3) for subjects with both hyperplastic and adenomatous polyps concurrently. Effects were weaker among ex smokers; the smoking-associated ORs remained consistently higher for hyperplastic polyps. This pattern was also seen in relation to cigarettes smoked per day, smoking duration, and pack-years. Tobacco-associated risks for multiple polyps were also stronger when hyperplastic disease was involved. In conclusion, tobacco use, particularly recent use, increases risk for both adenomatous and hyperplastic polyps, but the risks are substantially greater for hyperplastic lesions.

Different p53 mutation patterns in colorectal tumors from smokers and nonsmokers

Epidemiological studies consistently find associations between colorectal cancer and cigarette smoking; however, there are little molecular data supporting the association. To examine the relationship between cigarette smoking and colorectal cancer, we compared p53 mutation patterns in colorectal tumors from smokers and nonsmokers. In this study, 153 tumor tissues from colorectal cancer patients, including 63 smokers and 90 nonsmokers, were examined for p53 mutation and p53 protein expression by direct sequencing and immunohistochemistry (IHC), respectively. p53 mutations were detected in 77 of 153 (50.3%) colorectal tumors, and no difference was observed in the p53 mutation frequencies in tumors from smokers and nonsmokers (33 of 63, 50.8% for smokers vs. 44 of 90, 48.9% for nonsmokers, P = 0.743). IHC showed that p53-immunoreactive tumors were positively correlated with p53-mutated tumors (P < 0.0001). G:C-->A:T transition and G:C-->T:A transversion were the predominant types of mutations detected in the tumor p53 genes. G:C-->A:T mutation was relatively more common in nonsmokers than in smokers (93.5% for nonsmokers vs. 77.3% for smokers), although this difference was not significant. The frequency of deletion mutation in smoker tumors, however, was significantly higher than that in nonsmoker tumors (7 of 33, 21.2% for smokers vs. 1 of 44, 2.3% for nonsmokers, P = 0.01). Although there were only a few cases of p53 deletion mutation in this study, the observation of a higher frequency of p53 deletion mutation in smoker tumors supports the association between cigarette smoking and the development of colorectal cancer.

Nucleotide excision repair gene polymorphisms and risk of advanced colorectal adenoma: XPC polymorphisms modify smoking-related risk

OBJECTIVES

Nucleotide excision repair enzymes remove bulky damage caused by environmental agents, including carcinogenic polycyclic aromatic hydrocarbons found in cigarette smoke, a risk factor for colorectal adenoma. Among participants randomized to the screening arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, we studied the risk of advanced colorectal adenoma in relation to cigarette smoking and selected single nucleotide polymorphisms (SNP) in the nucleotide excision repair pathway.

METHODS

Cases (n = 772) were subjects with left-sided advanced adenoma (>1 cm in size, high-grade dysplasia, or villous characteristics). Controls (n = 777) were screen-negative for left-sided polyps by sigmoidoscopy. DNA was extracted from blood samples and 15 common nonsynonymous SNPs in seven-nucleotide excision repair genes [XPC, RAD23B (hHR23B), CSB (ERCC6), XPD (ERCC2), CCNH, XPF (ERCC4), and XPG (ERCC5)] were genotyped.

RESULTS

None of the studied SNPs were independently associated with advanced adenoma risk. Smoking was related to adenoma risk and XPC polymorphisms (R492H, A499V, K939Q) modified these effects (P(interaction) from 0.03-0.003). Although the three XPC variants were in linkage disequilibrium, a multivariate logistic regression tended to show independent protective effects for XPC 499V (P(trend) = 0.06), a finding supported by haplotype analysis (covariate-adjusted global permutation P = 0.03).

CONCLUSIONS

Examining a spectrum of polymorphic variants in nucleotide excision repair genes, we found evidence that smoking-associated risks for advanced colorectal adenoma are modified by polymorphisms in XPC, particularly haplotypes containing XPC 499V.

Role of epoxide hydrolase, NAD(P)H:quinone oxidoreductase, cytochrome P450 2E1 or alcohol dehydrogenase genotypes in susceptibility to colorectal cancer

Colorectal cancer (CRC) is one of the most common forms of cancer in Western countries. CRC has been associated with genetic and lifestyle factors. Individual susceptibility to CRC may be due partly to variations in detoxification capacity in the gastrointestinal tract. Genetic polymorphisms in detoxification enzymes may result in variations in detoxification activities, which subsequently might influence the levels of toxic/carcinogenic compounds, and this may influence the risk for CRC. Therefore, we determined whether polymorphisms in the genes coding for microsomal epoxide hydrolase (EPHX1), NAD(P)H:quinone oxidoreductase (NQO1), cytochrome P450 2E1 (CYP2E1) and alcohol dehydrogenase (ADH3) predispose to the development of CRC. DNA samples were obtained from 371 patients with sporadic CRC and 415 healthy controls. Patients and controls were all of Caucasian origin. All genetic polymorphisms were determined by polymerase chain reaction, eventually followed by restriction-fragment-length-polymorphism analyses, except for the EPHX1 codon 113 polymorphism, which was genotyped by an allele-specific discrimination assay. Calculation of crude Odds Ratios (ORs) revealed an increased risk for CRC associated with variant NQO1 (OR 1.5, 95% CI 1.1-2.0) and CYP2E1 intron 6 genotypes (OR 2.2, 95% CI 1.3-3.8). However, after adjustment for age and gender, logistic regression analyses only showed a statistically significant risk for CRC associated with variant NQO1 genotypes (OR 1.6, 95% CI 1.03-2.4). No associations were found between CRC and the other polymorphic genes as mentioned above. In conclusion, these data suggest that the presence of variant NQO1 genotypes, with expected reduced enzyme activities might enhance susceptibility to CRC.