A pharmacogenetic study to investigate the role of dietary carcinogens in the etiology of colorectal cancer

Poor metabolizers at the cytochrome P450 2C19 loci is at increased risk of developing cancer in Asian populations

BACKGROUND

CYP2C19 encodes a member of the cytochrome P450 superfamily of enzymes, which play a central role in activating and detoxifying many carcinogens and endogenous compounds thought to be involved in the development of cancer. In the past decade, two common polymorphisms among CYP2C19 (CYP2C19*2 and CYP2C19*3) that are responsible for the poor metabolizers (PMs) phenotype in humans and cancer susceptibility have been investigated extensively; however, these studies have yielded contradictory results.

METHODS AND RESULTS

To investigate this inconsistency, we conducted a comprehensive meta-analysis of 11,554 cases and 16,592 controls from 30 case-control studies. Overall, the odds ratio (OR) of cancer was 1.52 [95% confidence interval (CI): 1.23-1.88, P<10(-4)] for CYP2C19 PMs genotypes. However, this significant association vanished when the analyses were restricted to 5 larger studies (no. of cases ≥ 500 cases). In the subgroup analysis for different cancer types, PMs genotypes had an effect of increasing the risks of esophagus cancer, gastric cancer, lung cancer and hepatocellular carcinoma as well as head neck cancer. Significant results were found in Asian populations when stratified by ethnicity; whereas no significant associations were found among Caucasians. Stratified analyses according to source of controls, significant associations were found only in hospital base controls.

CONCLUSIONS

Our meta-analysis suggests that the CYP2C19 PMs genotypes most likely contributes to cancer susceptibility, particularly in the Asian populations.

quantitative assessment of the influence of cytochrome P450 1A2 gene polymorphism and colorectal cancer risk

Cytochrome P450 1A2 (CYP1A2) encodes a member of the cytochrome P450 superfamily of enzymes, which play a central role in activating and detoxifying many carcinogens and endogenous compounds thought to be involved in the development of colorectal cancer (CRC). The CYP1A2*C (rs2069514) and CYP1A2*F (rs762551) polymorphism are two of the most commonly studied polymorphisms of the gene for their association with risk of CRC, but the results are conflicting. To derive a more precise estimation of the relationship between CYP1A2 and genetic risk of CRC, we performed a comprehensive meta-analysis which included 7088 cases and 7568 controls from 12 published case-control studies. In a combined analysis, the summary per-allele odds ratio for CRC was 0.91 (95% CI: 0.83-1.00, P = 0.04), and 0.91 (95% CI: 0.68-1.22, P = 0.53), for CYP1A2 *F and *C allele, respectively. In the subgroup analysis by ethnicity, significant associations were found in Asians for CYP1A2*F and CYP1A2*C, while no significant associations were detected among Caucasian populations. Similar results were also observed using dominant genetic model. Potential sources of heterogeneity were explored by subgroup analysis and meta-regression. No significant heterogeneity was detected in most of comparisons. This meta-analysis suggests that the CYP1A2 *F and *C polymorphism is a protective factor against CRC among Asians.

Association between NQO1 C609T polymorphism and colorectal cancer risk

NAD(P)H

quinone oxidoreductase 1 (NQO1) is a cytosolic enzyme, and the NQO1 C609T polymorphism is associated with the enzymatic activity of NQO1. Many studies were performed to assess the association between NQO1 C609T polymorphism and colorectal cancer risk, but no consensus was available up to now. We conducted a meta-analysis to examine the association between NQO1 C609T polymorphism and colorectal cancer risk, and the pooled odds ratios (OR) with their 95% confidence intervals (95% CI) were used to assess the association. Finally, 12 studies involving 4,026 cases and 4,855 controls were included into the meta-analysis. Overall, there was an obvious association between NQO1 C609T polymorphism and colorectal cancer risk (T versus C: OR = 1.28, 95% CI 1.08-1.51, P = 0.005; TT versus CC: OR = 1.60, 95% CI 1.10-2.33, P = 0.015; TT/CT versus CC: OR = 1.36, 95% CI 1.09-1.69, P = 0.006; TT versus CT/CC: OR = 1.37, 95% CI 1.05-1.80, P = 0.022). Subgroup analysis by ethnicity showed that the association was obvious in both Caucasians and Asians. Therefore, the meta-analysis provides strong evidence for the association between NQO1 C609T polymorphism and colorectal cancer risk, and the T allele of NQO1 C609T polymorphism is an important risk factor of colorectal cancer.

The NQO1 polymorphism C609T (Pro187Ser) and cancer susceptibility: a comprehensive meta-analysis

Background:

Evidence is increasingly emerging about multiple roles for the NAD(P)H quinone oxidoreductase 1 enzyme in cancer. The C609T (rs1800566, Pro187Ser) null polymorphism of the NQO1 gene contributes significantly to the variation in enzymatic activity across different populations. NQO1 C609T polymorphism was thoroughly investigated with respect to cancer susceptibility. The results were inconsistent partly due to low sample sizes. The aim of the present work was to perform a meta-analysis to assess association for all common cancer sites separately and in combination.

Methods:

Our meta-analysis involved 92 studies including 21 178 cases and 25 157 controls. Statistical analysis involved individual cancer sites and the combined cancer risk. Association was tested under different genetic models.

Results:

We found a statistically significant association between the variant T allele and overall cancer risk in the worldwide population (for the TT vs CC model, OR=1.18 (1.07–1.31), P=0.002, I²=36%). Stratified analysis revealed that this association was largely attributed to the Caucasian ethnicity (for the TT vs CC model, OR=1.28 (1.12–1.46), P=0.0002, I²=1%). Stratification by tumour site showed significant association for bladder cancer in the worldwide population (for the TT vs CC model, OR=1.70 (1.17–2.46), P=0.005, I²=0%), and in the Asian population (for the TT vs CC model, 1.48 (1.14–1.93), P=0.003, I²=16%). Positive association was also found for gastric cancer in the worldwide population under the dominant model (OR=1.34 (1.09–1.65), P=0.006, I²=15%).

Conclusion:

Our results indicate that the C609T polymorphism of the NQO1 gene is an important genetic risk factor in cancer.

Functional polymorphisms in the CYP2C19 gene contribute to digestive system cancer risk: evidence from 11,042 subjects

Background

CYP2C19 belongs to the cytochrome P450 superfamily of enzymes involved in activating and detoxifying many carcinogens and endogenous compounds, which has attracted considerable attention as a candidate gene for digestive system cancer. CYP2C19 has two main point mutation sites (CYP2C19*2, CYP2C19*3) leading to poor metabolizer (PM) phenotype. In the past decade, the relationship between CYP2C19 polymorphism and digestive system cancer has been reported in various ethnic groups; however, these studies have yielded contradictory results.

Methods

To clarify this inconsistency, we performed this meta-analysis. Databases including Pubmed, EMBASE, Web of Science and China National Knowledge Infrastructure (CNKI) were searched to find relevant studies. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of association.

Results

In total, 18 studies with 4,414 cases and 6,628 controls were included. Overall, significantly elevated digestive system cancer risk was associated CYP2C19 PM with OR of 1.66 (95%CI: 1.31–2.10, P<10⁻⁵) when all studies were pooled into the meta-analysis. There was strong evidence of heterogeneity (P = 0.006), which largely disappeared after stratification by cancer type. In the stratified analyses according to cancer type, ethnicity, control source and sample size, significantly increased risks were found.

Conclusions

In summary, our meta-analysis suggested that the PM phenotype caused by the variation on CYP2C19 gene is associated with increased risk of digestive system cancer, especially in East Asians.

Association of methylenetetrahydrofolate reductase C677T and A1298C polymorphisms with colorectal cancer risk: A meta-analysis

Colorectal cancer (CRC) is one of the most common types of cancer worldwide and a leading cause of cancer-related mortality. This meta-analysis was conducted to determine the effect of methylenetetrahydrofolate reductase (MTHFR) mutants on the risk of CRC. A literature search was conducted on PubMed, Medline and the China National Knowledge Infrastructure (CNKI) databases. Eligible studies were collected based on rigorous criteria of inclusion. The pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated by the fixed- or random-effects model. After all the studies were pooled, the OR of CRC for individuals carrying the MTHFR 677TT genotype, compared to the CC genotype, was 0.89 (95% CI: 0.82-0.97). When analyzed by ethnicity, Asians with the MTHFR 1298CC genotype exhibited a decreased risk of CRC (OR=0.69; 95% CI: 0.54-0.89). In a mixed population, a significantly reduced risk of CRC was observed among carriers of the 677TT (OR=0.86; 95% CI: 0.76-0.96) and the 1298CC (OR=0.82; 95% CI: 0.69-0.98) genotypes, compared to the wild-type homozygous genotype. In the subgroup of colon cancer, the OR of 677TT vs. CC+CT was 0.83 (95% CI: 0.72-0.96) and the OR of 1298CC vs. AA+AC was 0.81 (95% CI: 0.69-0.96). In the rectal cancer subgroup, the OR of 677TT vs. CC+CT was 0.86 (95% CI: 0.77-0.97). Therefore, this meta-analysis suggested that the MTHFR 677T and 1298C alleles were associated with a low risk of CRC.

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.

GSTP1 Ala114Val polymorphism and colorectal cancer risk: a meta-analysis

Studies investigating the association between cytochrome glutathione S-transferase P1 (GSTP1) Ala114Val polymorphism and colorectal cancer (CRC) risk report conflicting results. The aim of this study was to quantitatively summarize the evidence for such a relationship. Two investigators independently searched the Medline, Embase, China National Knowledge Infrastructure, and Chinese Biomedicine databases. Summary odds ratios (ORs) and 95 % confidence intervals (95 % CIs) for GSTP1 polymorphism and CRC were calculated in a fixed effects model (the Mantel-Haenszel method) and a random effects model (the DerSimonian and Laird method) when appropriate. The pooled ORs were performed for co-dominant model (ValVal vs. AlaAla, AlaVal vs. AlaAla), dominant model (ValVal + AlaVal vs. AlaAla), and recessive model (ValVal vs. AlaVal + AlaAla). This meta-analysis included seven case-control studies, which included 3,173 CRC cases and 3,323 controls. Overall, the variant genotypes (ValVal and AlaVal) of the Ala114Val were not associated with CRC risk when compared with the wild-type AlaAla homozygote. Similarly, no associations were found in the dominant and recessive models. When stratifying for ethnicity, Hardy-Weinberg equilibrium in controls, study sample size, and source of controls, a significantly increased risk was observed among Asians (AlaVal vs. AlaAla, OR=1.67, 95 % CI=1.08-2.59; dominant model, OR=1.74, 95 % CI=1.14-2.67). No heterogeneity or publication bias was found in the present study. This meta-analysis suggests that the GSTP1 Ala114Val polymorphism may not be associated with CRC risk, while the observed increase in risk of CRC may be due to small-study bias.

The 677C>T (rs1801133) polymorphism in the MTHFR gene contributes to colorectal cancer risk: a meta-analysis based on 71 research studies

Background

The 677C>T polymorphism of methylenetetrahydrofolate reductase (MTHFR) gene is considered to have a significant effect on colorectal cancer susceptibility, but the results are inconsistent. In order to investigate the association between the MTHFR 677C>T polymorphism and the risk of colorectal cancer, a meta-analysis was held based on 71 published studies.

Methods

Eligible studies were identified through searching the MEDLINE, EMBASE, PubMed, Web of Science, Chinese Biomedical Literature database (CBM) and CNKI database. Odds ratios (OR) and 95% confidence intervals (CIs) were used to assess the association. The statistical heterogeneity across studies was examined with x²-based Q-test. Begg's and Egger's test were also carried out to evaluate publication bias. Sensitive and subgroup analysis were also held in this meta-analysis.

Results

Overall, 71 publications including 31,572 cases and 44,066 controls were identified. The MTHFR 677 C>T variant genotypes are significantly associated with increased risk of colorectal cancer. In the stratified analysis by ethnicity, significantly increased risks were also found among Caucasians for CC vs TT (OR = 1.076; 95%CI =  1.008–1.150; I² = 52.3%), CT vs TT (OR = 1.102; 95%CI = 1.032–1.177; I² = 51.4%) and dominant model (OR = 1.086; 95%CI = 1.021–1.156; I² = 53.6%). Asians for CC vs TT (OR  = 1.226; 95%CI  = 1.116–1.346; I²  = 55.3%), CT vs TT (OR  = 1.180; 95%CI  = 1.079–1.291; I²  = 36.2%), recessive (OR  = 1.069; 95%CI  = 1.003-1.140; I²  = 30.9%) and dominant model (OR  = 1.198; 95%CI  = 1.101-1.303; I²  = 52.4%), and Mixed populations for CT vs TT (OR  = 1.142; 95%CI  = 1.005-1.296; I²  = 0.0%). However, no associations were found in Africans for all genetic models.

Conclusion

This meta-analysis suggests that the MTHFR 677C>T polymorphism increases the risk for developing colorectal cancer, while there is no association among Africans found in subgroup analysis by ethnicity.

Association of carbamazepine major metabolism and transport pathway gene polymorphisms and pharmacokinetics in patients with epilepsy

AIM

The aim of this study was to evaluate the association of genetic variants in the major genes involved in carbamazepine (CBZ) metabolism and transport with its pharmacokinetics in epilepsy patients.

MATERIALS & METHODS

Twenty-five SNPs within seven CBZ pathway genes, namely CYP3A4, CYP3A5, EPHX1, NR1I2, UGT2B7, ABCB1 and ABCC2, were analyzed for association with CBZ pharmacokinetics in 90 epilepsy patients.

RESULTS

The CYP3A4*1B SNP was significantly associated with CBZ clearance. Significant association of EPHX1 SNPs was observed with greater carbamazepine-10,11-trans dihydrodiol:carbamazepine 10-11 epoxide ratios. Among drug transporters, ABCB1 and ABCC2 SNPs were significantly associated with altered CBZ clearance.

CONCLUSION

SNPs within CBZ pathway genes contribute to interpatient variation in CBZ pharmacokinetics and might contribute to pharmacoresistant epilepsy. Although our results need further clinical validation in a larger patient cohort, they indicate that genetic variation in CBZ pathway genes could influence its pharmacokinetics, and hence would have clinical significance.

Analysis of the Functional Polymorphism in the Cytochrome P450 CYP2C8 Gene rs11572080 with Regard to Colorectal Cancer Risk

In addition to the known effects on drug metabolism and response, functional polymorphisms of genes coding for xenobiotic-metabolizing enzymes (XME) play a role in cancer. Genes coding for XME act as low-penetrance genes and confer modest but consistent and significant risks for a variety of cancers related to the interaction of environmental and genetic factors. Consistent evidence supports a role for polymorphisms of the cytochrome P450 CYP2C9 gene as a protecting factor for colorectal cancer susceptibility. It has been shown that CYP2C8 and CYP2C9 overlap in substrate specificity. Because CYP2C8 has the common functional polymorphisms rs11572080 and rs10509681 (CYP2C8*3), it could be speculated that part of the findings attributed to CYP2C9 polymorphisms may actually be related to the presence of polymorphisms in the CYP2C8 gene. Nevertheless, little attention has been paid to the role of the CYP2C8 polymorphism in colorectal cancer. We analyzed the influence of the CYP2C8*3 allele in the risk of developing colorectal cancer in genomic DNA from 153 individuals suffering colorectal cancer and from 298 age- and gender-matched control subjects. Our findings do not support any effect of the CYP2C8*3 allele (OR for carriers of functional CYP2C8 alleles = 0.50 (95% CI = 0.16–1.59; p = 0.233). The absence of a relative risk related to CYP2C8*3 did not vary depending on the tumor site. We conclude that the risk of developing colorectal cancer does not seem to be related to the commonest functional genetic variation in the CYP2C8 gene.

Combined effects of GSTO1 and SULT1A1 polymorphisms and cigarette smoking on urothelial carcinoma risk in a Taiwanese population

BACKGROUND/PURPOSE

Cigarette smoking is the main risk factor for urothelial carcinoma of the bladder (UCB). Glutathione S-transferase omega 1 (GSTO1) and sulfotransferase 1A1 (SULT1A1) have been reported to be associated with the metabolism of polycyclic aromatic hydrocarbons (PAHs) and aromatic amines. The aim of the present study was to investigate the combined effects of polymorphisms in GSTO1 and SULT1A1 genes and cigarette smoking on UCB risk in a Taiwanese population.

METHODS

A total of 300 patients with histopathologically confirmed UCB and 233 cancer-free controls were recruited from the Department of Urology of Tung's Taichung Metro Harbor Hospital and Taipei Medical University Hospital. A comprehensive interview was conducted to collect personal information, including demographic characteristics and cigarette smoking status. A multivariate-adjusted logistic regression was performed to estimate the risk of UCB.

RESULTS

A significantly increased risk of UCB was observed in ever smokers [odds ratio (OR) = 2.3]. The Ala/Ala genotype of the GSTO1 gene and the Arg/Arg genotype of the SULT1A1 gene were associated with a significantly increased risk of UCB, with ORs of 1.8 [95% confidence interval (CI) = 1.2-2.6] and 2.1 (95% CI = 1.6-4.5), respectively. Significantly increased UCB risks were found in heavy smokers with the Ala/Ala genotype of the GSTO1 gene (OR = 4.2) and the Arg/Arg genotype of the SULT1A1 gene (OR = 6.8). Furthermore, a significant synergistic effect in an additive model (OR = 3.5) between the GSTO1 Ala/Ala genotype and the SULT1A1 Arg/Arg genotype on UCB risk was observed.

CONCLUSION

The present study provided epidemiological evidence for a significantly increased risk of UCB in ever smokers with the Ala/Ala genotype of the GSTO1 gene and the Arg/Arg genotype of the SULT1A1 gene.

CYP1B1 Asn453Ser polymorphism and colorectal cancer risk: a meta-analysis

Studies investigating the association between cytochrome P450 1B1 (CYP1B1) Asn453Ser (453 A/G, rs1800440) polymorphism and colorectal cancer (CRC) risk report conflicting results. The aim of this study was to quantitatively summarize the evidence for such a relationship. Two investigators independently searched the Medline and Embase Databases. Summary odds ratios (ORs) and 95% confidence intervals (95% CIs) for CYP1B1 polymorphism and CRC were calculated in a fixed-effects model (the Mantel-Haenszel method) and a random-effects model (the DerSimonian and Laird method) when appropriate. The pooled ORs were performed for co-dominant model (GG vs AA, GA vs AA), dominant model (GG+GA vs AA), and recessive model (GG vs GA+AA). This meta-analysis included 7 case-control studies, which included 6375 CRC cases and 7003 controls. Overall, the variant genotypes (GG and GA) of the 453 A/G were not associated with CRC risk when compared with the wild-type AA homozygote (GG vs AA, OR=0.94, 95% CI=0.77-1.14; GA vs AA, OR=0.99, 95% CI=0.87-1.12). Similarly, no associations were found in the dominant and recessive models (dominant model, OR=0.98, 95% CI=0.87-1.09; recessive model, OR=0.94, 95% CI=0.77-1.14). When stratifying for country, study sample size, matched control and source of controls, no evidence of significant association was observed in any subgroup, except among those studies from "Canada". No publication bias was found in the present study. No association was found between the CYP1B1 Asn453Ser polymorphism and risk of CRC among Caucasians.

Systematic review and meta-analysis of the relationship between EPHX1 polymorphisms and colorectal cancer risk

BACKGROUND

Microsomal epoxide hydrolase (EPHX1) plays an important role in both the activation and detoxification of PAHs, which are carcinogens found in cooked meat and tobacco smoking. Polymorphisms at exons 3 and 4 of the EPHX1 gene have been reported to be associated with variations in EPHX1 activity. The aim of this study is to quantitatively summarize the relationship between EPHX1 polymorphisms and colorectal cancer (CRC) risk.

METHODS

Two investigators independently searched the Medline, Embase, CNKI, and Chinese Biomedicine Databases for studies published before June 2012. Summary odds ratios (ORs) and 95% confidence intervals (CIs) for EPHX1 Tyr113His (rs1051740) and His139Arg (rs2234922) polymorphisms and CRC were calculated in a fixed-effects model and a random-effects model when appropriate.

RESULTS

This meta-analysis yielded 14 case-control studies, which included 13 studies for Tyr113His (6395 cases and 7893 controls) and 13 studies for His139Arg polymorphisms (5375 cases and 6962 controls). Overall, the pooled results indicated that EPHX1 Tyr113His polymorphism was not associated with CRC risk; while the His139Arg polymorphism was significantly associated with decreased CRC risk (Arg/His vs. His/His, OR = 0.90, 95%CI = 0.83-0.98; dominant model, OR = 0.92, 95%CI = 0.85-0.99). The statistically significant association between EPHX1 His139Arg polymorphism and CRC was observed among Caucasians and population-based case-control studies. This association showed little heterogeneity and remained consistently strong when analyses were limited to studies in which genotype frequencies were in Hardy-Weinberg equilibrium, or limited to studies with matched controls. When cumulative meta-analyses of the two associations were conducted by studies' publication time, the results were persistent and robust.

CONCLUSION

This meta-analysis suggests that EPHX1 Tyr113His polymorphism may be not associated with CRC development; while the EPHX1 His139Arg polymorphism may have a potential protective effect on CRC.

Interethnic and Intraethnic Variability of CYP2C8 and CYP2C9 Polymorphisms in Healthy Individuals

Cytochrome P450 (CYP) superfamily members CYP2C8 and CYP2C9 are polymorphically expressed enzymes that are involved in the metabolic inactivation of several drugs, including, among others, antiepileptics, NSAIDs, oral hypoglycemics, and anticoagulants. Many of these drugs have a narrow therapeutic index, and growing evidence indicates a prominent role of CYP2C8 and CYP2C9 polymorphisms in the therapeutic efficacy and in the development of adverse effects among patients treated with drugs that are CYP2C8 or CYP2C9 substrates. In this review, we summarize present knowledge on human variability in the frequency of variant CYP2C8 and CYP2C9 alleles. Besides an expected interethnic variability in allele frequencies, a large intraethnic variability exists. Among Asian subjects, for example, statistically significant differences (p < 0.0001) in CYP2C9*3 allele frequencies between Chinese and Japanese individuals have been reported. In addition, individuals from East Asia present different allele frequencies for CYP2C9*2 and CYP2C9*3 compared with South Asian subjects (p < 0.0001). Among Caucasian Europeans, statistically significant differences for the frequency of CYP2C8*3, CYP2C9*2, and CYP2C9*3 exist (p < 0.0001). This indicates that Asian individuals or Caucasian European individuals cannot be considered as homogeneous groups regarding CYP2C8 or CYP2C9 allele frequencies. Caucasian American subjects also show a large variability in allele frequencies, which is likely to be related to ethnic ancestry. A higher frequency of variant CYP2C8 and CYP2C9 alleles is expected among Caucasian Americans with South European ancestry than in individuals with North European ancestry. The findings summarized in this review suggest that among individuals with Asian or European ancestry, intraethnic differences in the risk of developing adverse effects with drugs that are CYP2C8 or CYP2C9 substrates are to be expected. In addition, the observed intraethnic variability reinforces the need for proper selection of control subjects and points against the use of surrogate control groups for studies involving association of CYP2C8 or CYP2C9 alleles with adverse drug reactions or spontaneous diseases.

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.

MTHFR C677T polymorphism contributes to colorectal cancer susceptibility: evidence from 61 case-control studies

Methylenetetrahydrofolate reductase (MTHFR) is believed to be involved in folate metabolism which plays a critical role in carcinogenesis. To date, many case-control studies have investigated the association between MTHFR C677T polymorphism and colorectal cancer risk. However, the results were inconsistent. In order to derive a more precise estimation of the association, we conducted this meta-analysis. This meta-analysis recruited 61 published studies which were selected by a search of PubMed up to 31st September 2011, including 16,111 colorectal cancer cases and 23,192 controls. We used crude odds ratios (ORs) with 95 % confidence intervals (CIs) to assess the association between MTHFR C677T polymorphism and colorectal cancer susceptibility. Our results showed that MTHFR C667T polymorphism contributed to the decreased colorectal cancer risk in overall population (for TT vs. CC: OR = 0.89, 95 % CI = 0.82-0.97; for TT vs. CT/CC: OR = 0.88, 95 % CI = 0.83-0.92). In subgroup analysis by ethnicity, the results also indicated a correlation between the T allele of MTHFR C667T and the colorectal cancer risk in Asian population (for TT vs. CC: OR = 0.82, 95 % CI = 0.69-0.97; for TT vs. CT/CC: OR = 0.81, 95 % CI = 0.74-0.90). Additionally, the correlation was also observed in male subgroup in sub-analysis by gender (for TT vs. CC: OR = 0.82, 95 % CI = 0.71-0.93; for TT vs. CT/CC: OR = 0.81, 95 % CI = 0.71-0.92). In summary, our meta-analysis strongly indicated the MTHFR C667T polymorphism was associated with a reduced risk of CRC.

The polymorphisms in methylenetetrahydrofolate reductase, methionine synthase, methionine synthase reductase, and the risk of colorectal cancer

Polymorphisms in genes involved in folate metabolism may modulate the risk of colorectal cancer (CRC), but data from published studies are conflicting. The current meta-analysis was performed to address a more accurate estimation. A total of 41 (17,552 cases and 26,238 controls), 24(8,263 cases and 12,033 controls), 12(3,758 cases and 5,646 controls), and 13 (5,511 cases and 7,265 controls) studies were finally included for the association between methylenetetrahydrofolate reductase (MTHFR) C677T and A1289C, methione synthase reductase (MTRR) A66G, methionine synthase (MTR) A2756G polymorphisms and the risk of CRC, respectively. The data showed that the MTHFR 677T allele was significantly associated with reduced risk of CRC (OR = 0.93, 95%CI 0.90-0.96), while the MTRR 66G allele was significantly associated with increased risk of CRC (OR = 1.11, 95%CI 1.01-1.18). Sub-group analysis by ethnicity revealed that MTHFR C677T polymorphism was significantly associated with reduced risk of CRC in Asians (OR = 0.80, 95%CI 0.72-0.89) and Caucasians (OR = 0.84, 95%CI 0.76-0.93) in recessive genetic model, while the MTRR 66GG genotype was found to significantly increase the risk of CRC in Caucasians (GG vs. AA: OR = 1.18, 95%CI 1.03-1.36). No significant association was found between MTHFR A1298C and MTR A2756G polymorphisms and the risk of CRC. Cumulative meta-analysis showed no particular time trend existed in the summary estimate. Probability of publication bias was low across all comparisons illustrated by the funnel plots and Egger's test. Collectively, this meta-analysis suggested that MTHFR 677T allele might provide protection against CRC in worldwide populations, while MTRR 66G allele might increase the risk of CRC in Caucasians. Since potential confounders could not be ruled out completely, further studies were needed to confirm these results.

Microsomal epoxide hydrolase polymorphisms, cigarette smoking, and risk of colorectal cancer: the Fukuoka Colorectal Cancer Study

Microsomal epoxide hydrolase (EPHX1) plays an important role in the activation and detoxification of polycyclic aromatic hydrocarbons, carcinogens found in cigarette smoke. Polymorphisms in exon 3 (Y113H) and exon 4 (H139R) of the EPHX1 have been associated with enzyme activity. We investigated the risk of colorectal cancer in relation to the EPHX1 Y113H and H139R polymorphisms and assessed effect modifications of cigarette smoking and the other covariates. The interaction between the EPHX1 polymorphisms and selected genetic polymorphisms was also examined. We used data from Fukuoka Colorectal Cancer Study, a community-based case-control study, including 685 cases and 778 controls. In-person interviews were conducted to assess lifestyle factors. The EPHX1 Y113H and H139R polymorphisms were determined by the TaqMan assay and the polymerase chain reaction-restriction fragment length polymorphism, respectively. Neither of the two polymorphisms nor the imputed EPHX1 phenotype was associated with colorectal cancer risk. Cigarette smoking and alcohol intake showed no effect modification on the association with the EPHX1 polymorphisms or the imputed EPHX1 phenotype. Increased risks of colorectal cancer associated with the 113Y allele and imputed EPHX1 phenotype were observed among individuals with high body mass index (BMI; ≥25.0 kg/m(2)), but not among those with low BMI (<25.0 kg/m(2)). The risk decreased with an increasing number of the 139R allele in the null genotypes of GSTM1/GSTT1. It is unlikely that the EPHX1 polymorphisms play an important role in colorectal carcinogenesis. The observed interactions of the EPHX1 polymorphisms with BMI and the GSTM1/GSTT1 genotypes warrant further investigation.

Investigation of a possible relationship between EPHX1 gene polymorphisms and colorectal cancer in Turkish society

Metabolism of chemical carcinogens, including their activation and detoxification, plays a key role in carcinogenesis. Microsomal epoxide hydrolase (EPHX1) has an important role in the metabolism of polycyclic aromatic hydrocarbons and detoxification of procarcinogens. The aim of this study was to investigate the association between colorectal cancer (CRC) development and EPHX1 gene polymorphisms. We investigated the polymorphisms in exon 3 (T>C, Tyr113His) and exon 4 (A>G, His139Arg) of the EPHX1 gene in 68 CRC patients and 116 controls by polymerase chain reaction-restriction fragment length polymorphism. The frequencies of the Try113Try, Try113His, and His113His for EPHX1 exon 3 were 37.9%, 55.2%, and 6.9% in controls and 39.7%, 42.6%, and 17.6% in CRC patients, respectively. Frequencies of EPHX1 exon 4 genotypes were 62.1% His139His, 37.9% His139Arg, and 0% Arg139Arg in the control group and 76.5% His139His, 22.1% His139Arg, and 1.5% Arg139Arg in the patient group. Individuals carrying the EPHX1 exon 3 His113His genotype had a 2.5-fold increased risk (p=0.024), and those carrying the EPHX1 exon 4 His139Arg genotype had decreased risk of CRC compared with controls (p=0.019). Even though exon 3 Tyr113His and exon 4 His139Arg polymorphisms for EPHX1 gene appear to be important factors for CRC risk, further investigations with larger study groups are needed to fully elucidate the role of these polymorphisms in the development of CRC.

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.

Risk of renal cell carcinoma and polymorphism in phase I xenobiotic metabolizing CYP1A1 and CYP2D6 enzymes

The progressive increase in sporadic renal cell carcinoma (RCC) observed in industrialized countries supports the opinion that certain carcinogens present in the environment (tobacco smoke, drugs, pollutants, and dietary constituents) may affect the occurrence and progression of this disease in developing countries like India. The polymorphism of the enzymes involved in metabolism of such environmental factors may, therefore, confer variable propensity to RCC. The possible association between RCC and a polymorphism of the CYP1A1 and CYP2D6 genes specific to the Indian population was examined using peripheral blood DNA from 196 RCC cases and 250 population controls with detailed data of clinicopathologic characteristics for the disease. The CYP1A1 (val) "variant" genotype, which contains at least 1 copy of the CYP1A1 variant alleles, was found to be associated with a 2.03-fold [GG ver. AA/AG, unadjusted OR = 2.03; 95%CI = 1.233-3.342; P = 0.005] increase in the risk of RCC. There was also a significant association (p(trend) = 0.034) between higher frequency of RCC subjects containing at least of copy of the CYP1A1 (val) "variant" genotype with III or IV Fuhrman's grade. Whereas, the CYP2D6 polymorphism did not show any association with RCC risk [TT ver. CT/CC, unadjusted OR = 95%CI = 1.233-3.342; P = 0.005]. There was a significant association (p(trend) = 0.001) between the poor metabolizer CYP2D6 (TT) and progression towards higher pathological stage of RCC. Our data demonstrate for the first time a significant association between pharmacogenetic polymorphisms of CYP1A1 and risk of RCC development in the Indian population. The findings suggest that inter-individual variation in the phase I metabolic enzymes involved in the fictionalization and detoxification of specific xenobiotics is an important susceptibility factor for development and progression of RCC in Indians.

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.

CYP1B1 Leu432Val polymorphism and colorectal cancer risk among Caucasians: a meta-analysis

Studies investigating the association between cytochrome P450 1B1 (CYP1B1) Leu432Val (432 C/G, rs1056836) polymorphism and colorectal cancer (CRC) risk report conflicting results. The aim of this study was to quantitatively summarize the evidence for such a relationship. Two investigators independently searched the Medline, Embase, China National Knowledge Infrastructure, and Chinese Biomedicine Databases. Summary odds ratios (ORs) and 95% confidence intervals (95% CIs) for CYP1B1 polymorphism and CRC were calculated in a fixed-effects model and a random-effects model when appropriate. The pooled ORs were performed for co-dominant model (GG vs. CC, GC vs. CC), dominant model (GG + GC vs. CC), and recessive model (GG vs. GC + CC). This meta-analysis included ten case-control studies, which included 8,466 CRC cases and 9,301 controls. Overall, the variant genotypes (GG and GC) of the 432 C/G were not associated with CRC risk when compared with the wild-type CC homozygote (GG vs. CC, OR = 1.01, 95% CI = 0.93-1.10; GC vs. CC, OR = 0.97, 95% CI = 0.90-1.04), without any between-study heterogeneity. Similarly, no associations were found in the dominant and recessive models (dominant model, OR = 0.98, 95% CI = 0.92-1.05; recessive model, OR = 1.03, 95% CI = 0.96-1.11). Limiting the analysis to the studies within Hardy-Weinberg equilibrium, the results were persistent and robust. When stratifying for country, matched control and source of controls, no evidence of significant association was observed in any subgroup. No publication bias was found in the present study. No association is found between the CYP1B1 Leu432Val polymorphism and risk of CRC among Caucasians.

Polycyclic aromatic hydrocarbons and digestive tract cancers: a perspective

Cancers of the colon are most common in the Western world. In majority of these cases, there is no familial history and sporadic gene damage seems to play an important role in the development of tumors in the colon. Studies have shown that environmental factors, especially diet, play an important role in susceptibility to gastrointestinal (GI) tract cancers. Consequently, environmental chemicals that contaminate food or diet during preparation become important in the development of GI cancers. Polycyclic aromatic hydrocarbons (PAHs) are one such family of ubiquitous environmental toxicants. These pollutants enter the human body through consumption of contaminated food, drinking water, inhalation of cigarette smoke, automobile exhausts, and contaminated air from occupational settings. Among these pathways, dietary intake of PAHs constitutes a major source of exposure in humans. Although many reviews and books on PAHs and their ability to cause toxicity and breast or lung cancer have been published, aspects on contribution of diet, smoking and other factors toward development of digestive tract cancers, and strategies to assess risk from exposure to PAHs have received much less attention. This review, therefore, focuses on dietary intake of PAHs in humans, animal models, and cell cultures used for GI cancer studies along with epidemiological findings. Bioavailability and biotransformation processes, which influence the disposition of PAHs in body and the underlying causative mechanisms of GI cancers, are also discussed. The existing data gaps and scope for future studies is also emphasized. This information is expected to stimulate research on mechanisms of sporadic GI cancers caused by exposure to environmental carcinogens.

Colorectal polyp type and the association with charred meat consumption, smoking, and microsomal epoxide hydrolase polymorphisms

We determined the association between charred meat consumption, cigarette smoking, microsomal epoxide hydrolase (mEH) polymorphisms (rs1051740 and rs2234922), and colorectal adenomas and hyperplastic polyps (HPs) and explored gene-environment interactions. Men and women with colorectal adenomas (n = 519), HPs (n = 691), or concurrently with both types of polyps (n = 227) and polyp-free controls (n = 772) receiving a colonoscopy from December 2004 to September 2007 were recruited. Participants completed telephone interviews and provided buccal cell samples; genotyping of mEH was completed using Taqman assays. We conducted polytomous regression and calculated odd ratios (OR) and 95% confidence intervals. Interactions were evaluated using Wald chi-square tests. Consumption of >3 servings of charred meat per week was associated with distal HPs (OR = 2.0, 1.2-3.4) but not adenomas nor either type of proximal polyp. Heavy cigarette smoking (≥ 22 pack-years) was associated with an increased risk for colorectal adenomas (OR = 1.7, 95% CI: 1.2-2.4), HPs (OR = 2.4, 95% CI: 1.7-3.3), and both types (OR = 2.8, 95% CI: 1.8-4.3) with the strongest association for distal polyps. There was no association between mEH genotype and colorectal polyps, nor were any statistically significant gene-environment interactions identified. Future investigation of BaP exposure and colorectal neoplasia should analyze whether associations are dependent upon anatomic location.

Association between CYP1A1 polymorphism and colorectal cancer risk: a meta-analysis

Colorectal cancer is one of the most common forms of cancer and is the third leading cause of cancer-related death worldwide. Published data on the association between CYP1A1 (MspI and Ile ( 462 ) Val) polymorphisms and colorectal cancer risk are inconclusive. To address these issues, we carried out a meta-analysis of available case-control study. Online electronic searches of PubMed were performed. We identified 17 studies (6,673 colorectal cancer patients and 8,102 control subjects) that examined the association between CYP1A1 (MspI and Ile ( 462 ) Val) polymorphisms and risk of colorectal cancer. For CYP1A1 MspI polymorphism, we performed a meta-analysis from 13 studies including 5,468 cases and 6,492 controls. Overall, there was no statistically significant association between CYP1A1 MspI polymorphism and colorectal cancer susceptibility. In the subgroup analyses based on ethnicities, no statistically significant associations were observed in all genetic models. With respect to CYP1A1 Ile ( 462 ) Val polymorphism, a total of 14 studies including 6,654 cases and 7,859 controls were involved in this meta-analysis. The CYP1A1 Ile ( 462 ) Val polymorphism was associated with risk of colorectal cancer. Ethnic subgroup analyses revealed that significant associations were found in Asians and Caucasians. In summary, this meta-analysis suggests that CYP1A1 Ile ( 462 ) Val polymorphism was a low-penetrance susceptibility gene in colorectal cancer development. On the contrary, CYP1A1 MspI polymorphism does not seem capable of modifying colorectal cancer risk.

Risk of colorectal cancer associated with the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism in the Kashmiri population

Methylenetetrahydrofolate reductase (MTHFR) is a critical enzyme in folate metabolism and is involved in DNA synthesis, DNA repair and DNA methylation. The two common functional polymorphisms of MTHFR, 677 C→T and 1298 A→C, have been shown to impact various diseases, including cancer. The 677 C→T polymorphism has been widely investigated in different cancers and has been implicated as a risk factor for the development of various cancers. We investigated MTHFR C677T genotype frequency in colorectal cancer cases in the Kashmiri population and correlated this information with the known clinicopathological characters of colorectal cancer, in a case-control study. Eighty-six colorectal cancer cases were studied for MTHFR C677T polymorphism, compared to 160 controls taken from the general population, employing the PCR-RFLP technique. We found the frequency of the three different genotypes of MTHFR in our ethnic Kashmir population, i.e., CC, CT and TT, to be 68.6, 20.9 and 10.4% among colorectal cancer cases and 75.6, 16.9 and 7.5% among the general control population, respectively. There was a significant association between the MTHFR TT genotype and colorectal cancer in the higher age group. We conclude that the MTHFR C677T polymorphism slightly increases the risk for colorectal cancer development in our ethnic Kashmir population.

SULT1A1 Arg213His polymorphism and susceptibility of environment-related cancers: a meta analysis of 5,915 cases and 7,900 controls

The common genetic polymorphism for SULT1A1 is Arg213His polymorphism, which may affect the sulfation process of various environmental carcinogens and thus is suggested to be related to susceptibility of several cancers. However, studies on the association between SULT1A1 Arg213His polymorphism and cancer susceptibility are inconsistent. To assess the relationship between Arg213His polymorphism and environmental-related cancers systematically, we performed a meta analysis from 20 case-control studies including 5,915 cases and 7,900 controls. The odds ratios (ORs) and 95% confidence intervals (CIs) were used to estimate the strength of risk, we found a significant association between SULT1A1 Arg213His polymorphism and environment-related cancers (for dominant model: OR 1.22, 95% CI 1.07-1.39, P = 0.003). When stratified by ethnicity, a significant risk was observed in Asian cases, compared with controls (for dominant model: OR 1.69, 95% CI 1.17-2.43, P = 0.005). When we chose only smokers in our analysis, we also found a significantly increased risk between Arg213His polymorphism and susceptibility of environment-related cancers for participants exposed to a smoking environment. In conclusion, SULT1A1 Arg213His polymorphism, ethnicity, smoking may modulate environment-related cancer risk. Studies on gene-gene interactions in the sequential or concurrent metabolic pathway and gene-environment interactions need to be further conducted to explore the susceptibility of cancer occurrence.

Lack of association of SULT1A1 R213H polymorphism with colorectal cancer: a meta-analysis

Background

A number of case-control studies were conducted to investigate the association of SULT1A1 R213H polymorphisms with colorectal cancer (CRC) in humans. But the results were not always consistent. We performed a meta-analysis to examine the association between the SULT1A1 R213H polymorphism and CRC.

Methods and Findings

Data were collected from the following electronic databases: PubMed, Elsevier Science Direct, Excerpta Medica Database, and Chinese Biomedical Literature Database, with the last report up to September 2010. A total of 12 studies including 3,549 cases and 5,610 controls based on the search criteria were involved in this meta-analysis. Overall, no significant association of this polymorphism with CRC was found (H versus R: OR = 1.04, 95%CI = 0.94–1.16, P = 0.46; HR+HH versus RR: OR = 1.01, 95%CI = 0.92–1.11, P = 0.81; HH versus RR+HR: OR = 1.01, 95%CI = 0.74–1.38, P = 0.95; HH versus RR: OR = 1.00, 95%CI = 0.77–1.31, P = 0.98; HR versus RR: OR = 1.01, 95%CI = 0.92–1.11, P = 0.86). In subgroup analysis, we also did not find any significant association in Cauasians (H versus R: OR = 1.02, 95%CI = 0.92–1.15, P = 0.68; HR+HH versus RR: OR = 0.99, 95%CI = 0.91–1.09, P = 0.90; HH versus RR+HR: OR = 1.01, 95%CI = 0.73–1.39, P = 0.97; HH versus RR: OR = 0.99, 95%CI = 0.75–1.31, P = 0.94; HR versus RR: OR = 0.99, 95%CI = 0.90–1.09, P = 0.85). The results were not materially altered after the studies which did not fulfill Hardy-Weinberg equilibrium were excluded (H versus R: OR = 1.06, 95%CI = 0.95–1.19, P = 0.31; HR+HH versus RR: OR = 1.03, 95%CI = 0.93–1.13, P = 0.56; HH versus RR+HR: OR = 1.10, 95%CI = 0.78–1.56, P = 0.57; HH versus RR: OR = 1.09, 95%CI = 0.83–1.44, P = 0.53; HR versus RR: OR = 1.02, 95%CI = 0.92–1.13, P = 0.75).

Conclusion

This meta-analysis demonstrates that there is no association between the SULT1A1 R213H polymorphism and CRC.

Putative EPHX1 enzyme activity is related with risk of lung and upper aerodigestive tract cancers: a comprehensive meta-analysis

Background

EPHX1 is a key enzyme in metabolizing some exogenous carcinogens such as products of cigarette-smoking. Two functional polymorphisms in the EPHX1 gene, Tyr113His and His139Arg can alter the enzyme activity, suggesting their possible association with carcinogenesis risk, particularly of some tobacco-related cancers.

Methodology/Principal Findings

A comprehensive systematic review and meta-analysis was performed of available studies on these two polymorphisms and cancer risk published up to November 2010, consisting of 84 studies (31144 cases and 42439 controls) for Tyr113His and 77 studies (28496 cases and 38506 controls) for His139Arg primarily focused on lung cancer, upper aerodigestive tract (UADT) cancers (including oral, pharynx, larynx and esophagus cancers), colorectal cancer or adenoma, bladder cancer and breast cancer. Results showed that Y113H low activity allele (H) was significantly associated with decreased risk of lung cancer (OR = 0.88, 95%CI = 0.80–0.96) and UADT cancers (OR = 0.86, 95%CI = 0.77–0.97) and H139R high activity allele (R) with increased risk of lung cancer (OR = 1.18, 95%CI = 1.04–1.33) but not of UADT cancers (OR = 1.05, 95%CI = 0.93–1.17). Pooled analysis of lung and UADT cancers revealed that low EPHX1 enzyme activity, predicted by the combination of Y113H and H139R showed decreased risk of these cancers (OR = 0.83, 95%CI = 0.75–0.93) whereas high EPHX1 activity increased risk of the cancers (OR = 1.20, 95%CI = 0.98–1.46). Furthermore, modest difference for the risk of lung and UADT cancers was found between cigarette smokers and nonsmokers both in single SNP analyses (low activity allele H: OR = 0.77/0.85 for smokers/nonsmokers; high activity allele R: OR = 1.20/1.09 for smokers/nonsmokers) and in combined double SNP analyses (putative low activity: OR = 0.73/0.88 for smokers/nonsmokers; putative high activity: OR = 1.02/0.93 for smokers/ nonsmokers).

Conclusions/Significance

Putative low EPHX1 enzyme activity may have a potential protective effect on tobacco-related carcinogenesis of lung and UADT cancers, whereas putative high EPHX1 activity may have a harmful effect. Moreover, cigarette-smoking status may influence the association of EPHX1 enzyme activity and the related cancer risk.

CYP1A1 Ile462Val polymorphism contributes to colorectal cancer risk: A meta-analysis

AIM: To study the relation between CYP1A1 Ile462Val polymorphism and colorectal cancer risk by meta-analysis.

METHODS: A meta-analysis was performed to investigate the relation between CYP1A1 Ile462Val polymorphism and colorectal cancer risk by reviewing the related studies until September 2010. Data were extracted and analyzed. Crude odds ratio (OR) with 95% confidence interval (CI) was used to assess the strength of relation between CYP1A1 Ile462Val polymorphism and colorectal cancer risk.

RESULTS: Thirteen published case-control studies including 5336 cases and 6226 controls were acquired. The pooled OR with 95% CI indicated that CYP1A1 Ile462Val polymorphism was significantly related with colorectal cancer risk (Val/Val vs Ile/Ile: OR = 1.47, 95% CI: 1.16-1.86, P = 0.002; dominant model: OR = 1.33, 95% CI: 1.01-1.75, P = 0.04; recessive model: OR = 1.49, 95% CI: 1.18-1.88, P = 0.0009). Subgroup ethnicity analysis showed that CYP1A1 Ile462Val polymorphism was also significantly related with colorectal cancer risk in Europeans (Ile/Val vs Ile/Ile: OR = 1.22, 95% CI: 1.05-1.42, P = 0.008; dominant model: OR = 1.24, 95% CI: 1.07-1.43, P = 0.004) and Asians (Val/Val vs Ile/Ile: OR = 1.40, 95% CI: 1.07-1.82, P = 0.01; recessive model: OR = 1.46, 95% CI: 1.12-1.89, P = 0.005).

CONCLUSION: CYP1A1 Ile462Val may be an increased risk factor for colorectal cancer.

CYP2W1 variant alleles in Caucasians and association of the CYP2W1 G541A (Ala181Thr) polymorphism with increased colorectal cancer risk

AIMS

To detect differences in the frequency of the known nonsynonymous CYP2W1 polymorphisms between colorectal cancer patients and healthy subjects.

MATERIALS & METHODS

The study group consisted of 150 colorectal patients and 263 controls. The presence of five nonsynonymous CYP2W1 polymorphisms was analyzed by novel amplification-restriction methods.

RESULTS

Two nonsynonymous SNPs causing the amino acid substitutions Val432Ile and Gln482His were monomorphic in the population study. Two nonsynonymous SNPs previously unknown in Caucasians, 1463T (rs3808348) and 173C (no rs number assigned), were detected in the population study, although these were not associated with colorectal cancer risk. Regarding the 541G/A polymorphism (rs3735684), the 541G allele (odds ratio: 2.2; 95% CI: 1.2-4.1) and the 541GG genotype (odds ratio: 2.06; 95% CI: 1.1-3.9) were associated with increased colorectal cancer risk in the population studied. Conversely, the 173C-541A-1463C haplotype (odds ratio: 0.46; 95% CI: 0.2-0.9) showed a protective odds ratio value.

CONCLUSION

CYP2W1 variant alleles are common among Caucasian individuals and, of these, the CYP2W1 G541A (Ala181Thr) polymorphism is associated with increased colorectal cancer risk.

Interactions between cigarette smoking and selected polymorphisms in xenobiotic metabolizing enzymes in risk for colorectal cancer: A case-only analysis

The metabolism of xenobiotics is complex and involves multiple steps and multiple enzymes. Genetic variation in the genes encoding these enzymes as well as the level of exposure to the substrates of these enzymes could alter metabolism and clearance of potential carcinogens and thus alter cancer susceptibility. This study examined interaction effect between smoking and two single nucleotide polymorphisms (SNPs)-CYP1A1 c.1384A>G (p.Ile462Val) and EPHX1 c.337T>C (p.Tyr113His)-in modulating colorectal cancer (CRC) risk. The SNPs were selected a priori based on functional significance. In a case-only analysis, unconditional logistic regression was used to examine the associations between smoking and each SNP and between the two SNPs in 786 patients with nonfamilial CRC. There was significant multiplicative interaction for CRC risk between smoking and EPHX1 c.337T>C (odds ratio [OR] = 1.37, 95% confidence interval [CI] = 1.03-1.81, P = 0.03), particularly among smokers with a history of greater than 20 pack-years of smoking (OR = 1.52, 95% CI = 1.07-2.16, P = 0.02). In addition, there was gene-gene interaction between EPHX1 c.337T>C and CYP1A1 c.1384A>G (OR = 1.61, 95% CI = 1.02-2.55, P = 0.04). Smokers with any variant allele of EPHX1 were at increased risk for CRC, as were individuals with any variant allele of CYP1A1 together with any variant allele of EPHX1. Thus, the study of gene-environment and gene-gene interactions may help to identify high-risk subgroups that can be targeted for intensive smoking cessation and CRC screening interventions.

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.

Glutathione S-transferase M1 polymorphism and sporadic colorectal cancer risk: An updating meta-analysis and HuGE review of 36 case-control studies

PURPOSE

Sporadic colorectal cancer (CRC) is considered to be a multifactorial disease, in which multiple exposures to endogenous factors interact with individual genetic background in a complex manner, resulting in modulation of the risk. The glutathione S-transferase M1 gene (GSTM1) is a particularly attractive candidate for CRC susceptibility because it codes an enzyme involved in the metabolism of environmental carcinogens. However, the epidemiological findings have been inconsistent.

METHODS

To evaluate this association, we performed an extensive meta-analysis of 36 case-control studies (including 10,009 cases and 15,070 controls).

RESULTS

Overall, the combined data showed that GSTM1 deficiency is associated with a marginal effect on CRC risk (odds ratio [OR] = 1.13; 95% confidence interval [CI]: 1.03-1.23; P for heterogeneity <0.001). When stratified by race and tumor site, significant results were only observed in Caucasians (OR = 1.14, 95% CI: 1.01-1.27; P for heterogeneity <0.001), whereas no increased risk was detected in other subgroups.

CONCLUSIONS

The findings of our study support the suggestion that GSTM1 polymorphism is associated with an increased risk of CRC, especially in the Caucasian population. Further investigation into the association between GSTM1 polymorphism and the risk of CRC is warranted and should include larger sample sizes and other genetic polymorphisms in metabolism of environmental carcinogens.

Genetic polymorphisms of CYP2D6 oxidation in patients with inflammatory bowel disease

Inflammatory bowel disease (IBD) consists of ulcerative colitis and Crohn's disease, both of which are associated with increased colorectal cancer risk. The relationship between genetically determined polymorphic metabolism of exogenous substances by oxidation catalyzed by CYP2D6 isoenzyme and susceptibility to cancer has aroused great interest. We determined whether there was an association between susceptibility to inflammatory bowel disease and particularly to CYP2D6 genotypes. The study was carried out in 39 patients with IBD. The control group consisted of 129 healthy volunteers. The CYP2D6 genotypes were analyzed by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method with DNA extracted from peripheral blood. Among 39 patients with inflammatory bowel disease, extensive metabolizer (EM) genotype constituted 97.4%. One patient (2.6%) was poor metabolizer with CYP2D6*4/CYP2D6*4 genotype. Results obtained in the inflammatory bowel disease group did not differ significantly from those of the control group. Although the odds ratio for EM metabolizers was about 3.8-fold greater in the group of patients with inflammatory bowel disease, this association was not statistically significant. This data also showed no overall statistically significant association between alleles and incidence risk of inflammatory bowel disease [odds ratio (OR) of 1.36 for CYP2D6*1 allele, 0.83 for CYP2D6*3 allele, and 0.74 for CYP2D6*4 allele]. The present results suggest that EM genotype may be the risk factor of inflammatory bowel disease. Future studies are needed to confirm our assumptions on larger group of patients.

Association between dietary heterocyclic amine levels, genetic polymorphisms of NAT2, CYP1A1, and CYP1A2 and risk of colorectal cancer: a hospital-based case-control study in Japan

OBJECTIVE

Although associations between dietary HCA intake and colorectal cancer risk have been investigated, results have been suggestive but inconsistent. The aim of this hospital-based case-control study was to examine the impact of heterocyclic amine (HCA) intake on colorectal cancer risk. A further objective was to investigate the possible effect of genetic polymorphisms of NAT2, CYP1A1, and CYP1A2 on colorectal cancer.

MATERIAL AND METHODS

HCA exposure data were assessed using a self-administered food frequency questionnaire, and estimated HCA intake was verified by measuring the PhIP value in human hair. A total of 117 cases and 238 controls were included in these analyses. Odds ratios (ORs) were calculated using conditional logistic regression analysis to compare intake levels between the first and third tertiles.

RESULTS

No statistically significant increase in the risk of colorectal cancer with respect to total HCA intake was shown by analysis (OR = 0.99, 95% CI = 0.21-4.81). Furthermore, no association with risk was seen for individual HCAs, including PhIP, MeIQ, and MeIQx. Although variant alleles of CYP1A2 were associated with colorectal cancer (OR = 0.27; 95% CI = 0.07-0.99), genetic polymorphisms of NAT2, CYP1A1, and CYP1A2 did not influence the association of HCA intake with colorectal cancer.

CONCLUSIONS

In the present study in subjects with low HCA exposure and with a limited sample size, no association was found between HCA intake and colorectal cancer, or any evidence of influence by genetic polymorphisms of NAT2, CYP1A1, and CYP1A2.

GSTM1, GSTT1, GSTP1, GSTA1 and colorectal cancer risk: a comprehensive meta-analysis

Glutathione S-transferases (GSTs) catalyse reactions between glutathione and lipophilic compounds with electrophilic centres, leading to neutralisation of toxic compounds, xenobiotics and products of oxidative stress. Controversy exists about whether GST polymorphisms (GSTM1 null/present genotype, GSTT1 null/present genotype, GSTP1 Ile105Val and GSTA1 *A/*B) represent risk factors for colorectal cancer. This meta-analysis aims to examine the associations between the above-mentioned polymorphisms and colorectal cancer risk. Forty-four studies were eligible for GSTM1 (11,998 colorectal cancer cases, 17,552 controls), 34 studies for GSTT1 (8596 cases, 13,589 controls), 19 studies for GSTP1 (5421 cases, 7671 controls) and four studies for GSTA1 polymorphism (1648 cases, 2039 controls). Pooled odds ratios (ORs) were appropriately derived from fixed-effects or random-effects models. Separate analyses were conducted on Caucasian and Chinese populations. Where appropriate, sensitivity analysis concerning the deviation of genotype frequencies in controls from the Hardy-Weinberg equilibrium was performed. GSTM1 null allele carriers exhibited increased colorectal cancer risk in Caucasian populations (pooled OR=1.150, 95% confidence interval (CI): 1.060-1.248, random effects); no significant association was detected for Chinese subjects (pooled OR=1.025, 95% CI: 0.903-1.163, fixed effects). Similarly, GSTT1 null allele carriers exhibited increased colorectal cancer risk in Caucasian populations (pooled OR=1.312, 95% CI: 1.119-1.538, random effects); the association in Chinese subjects was not significant (pooled OR=1.068, 95% CI: 0.788-1.449, random effects). Concerning GSTP1 Ile105Val no significant associations were demonstrated in either race. GSTA1 *A/*B polymorphism was not associated with colorectal cancer risk. GSTM1 and GSTT1 null genotypes confer additional risk for colorectal cancer in Caucasian populations.

Colon cancer chemopreventive activities of pomegranate ellagitannins and urolithins

Pomegranate juice derived ellagitannins and their intestinal bacterial metabolites, urolithins, inhibited TCDD-induced CYP1-mediated EROD activity in vitro with IC(50) values ranging from 56.7 microM for urolithin A to 74.8 microM for urolithin C. These compounds exhibited dose- and time-dependent decreases in cell proliferation and clonogenic efficiency of HT-29 cells. Inhibition of cell proliferation was mediated through cell cycle arrest in the G(0)/G(1) and G(2)/M stages of the cell cycle followed by induction of apoptosis. These results indicate that the ellagitannins and urolithins released in the colon upon consumption of pomegranate juice in considerable amounts could potentially curtail the risk of colon cancer development, by inhibiting cell proliferation and inducing apoptosis.

Association of polymorphisms MTHFR C677T and A1298C with risk of colorectal cancer, genetic and epigenetic characteristic of tumors, and response to chemotherapy

BACKGROUND AND AIMS

The enzyme MTHFR plays an important role in folate metabolism, and folate is implicated in carcinogenesis due to its role in DNA methylation, repair, and synthesis. We analyze the relationship of MTHFR C677T and A1298C polymorphisms with biological, clinicopathological, genetic and epigenetic features of tumors, and the patient outcome after treatment with 5-FU-based chemotherapy to determine the contribution of MTHFR genotypes in the risk of colorectal cancer (CRC) and in the response to therapy.

METHODS

Genomic DNA of 143 Spanish sporadic CRC and 103 controls was analyzed by polymerase chain reaction/restriction fragment length polymorphism and sequencing.

RESULTS

The C677T polymorphism has protective effect on CRC showing TT genotype an odds ratios of 0.06 (95% confidence interval (CI): 0.10-0.32) and the CT of 0.51 (95% CI: 0.3-0.87). MTHFR A1298C polymorphism is not associated with CRC risk. Patients with 1298CC and AC genotypes exhibit worse survival than those with the wild genotype (log rank, p = 0.001), whereas C677T genotypes do not affect patient survival (log rank, p = 0.92). MTHFR 677T allele carriers responded better to 5-FU-based chemotherapy than patients with the wild CC genotype (log rank, p = 0.05). The variant C allele of A1298C affects negatively the response to 5-FU-based chemotherapy (log rank, p = 0.009).

CONCLUSIONS

The variant allele of the C677T has a protective effect on CRC development, whereas the variant allele of the A1298C does not produce any effect on disease risk. Both MTHFR polymorphisms are relevant and independent factors of patient outcome after 5FU-based treatment of CRC, and MTHFR genotyping may be of predictive benefit in selecting treatment regimens.

Glucosinolates in Brassica vegetables: the influence of the food supply chain on intake, bioavailability and human health

Glucosinolates (GLSs) are found in Brassica vegetables. Examples of these sources include cabbage, Brussels sprouts, broccoli, cauliflower and various root vegetables (e.g. radish and turnip). A number of epidemiological studies have identified an inverse association between consumption of these vegetables and the risk of colon and rectal cancer. Animal studies have shown changes in enzyme activities and DNA damage resulting from consumption of Brassica vegetables or isothiocyanates, the breakdown products (BDP) of GLSs in the body. Mechanistic studies have begun to identify the ways in which the compounds may exert their protective action but the relevance of these studies to protective effects in the human alimentary tract is as yet unproven. In vitro studies with a number of specific isothiocyanates have suggested mechanisms that might be the basis of their chemoprotective effects. The concentration and composition of the GLSs in different plants, but also within a plant (e.g. in the seeds, roots or leaves), can vary greatly and also changes during plant development. Furthermore, the effects of various factors in the supply chain of Brassica vegetables including breeding, cultivation, storage and processing on intake and bioavailability of GLSs are extensively discussed in this paper.

Dietary fat-influenced development of colon neoplasia in Apc Min mice exposed to benzo(a)pyrene

Colorectal cancer, responsible for 50,000 deaths per year, is a contributing factor for considerable mortalities in the United States. Consumption of well-done red meat and saturated fats rich in polycyclic aromatic hydrocarbons may be one of the causative factors for sporadic colon cancer. The objective of this study was to investigate whether the formation of colon tumors in adult Apc(Min) mice was influenced by the ingestion of different types of fat containing benzo(a)pyrene [B(a)P], a polycyclic aromatic hydrocarbon compound. Treatment consisted of 50 and 100 microg B(a)P/kg body weight dissolved in peanut or coconut oil (representatives of unsaturated and saturated fats, respectively) administered daily to six-week-old male Apc(Min) mice via oral gavage for sixty days. At the end of exposure, mice were sacrificed; jejunum and colons were retrieved and preserved in 10% formalin for observation for gross pathological changes. An increased prevalence of adenomas in colons of mice that ingested B(a)P through saturated dietary fat compared to unsaturated fat and controls (p < .05) was noticed. Interestingly, we also observed adenomas with high-grade dysplasia in the B(a)P + saturated fat group, and these incidences were frequent at the 100 microg/kg B(a)P dose. On the other hand, the B(a)P-alone and unsaturated-fat groups did not show significant differences in the numbers of adenomas and invasive tumors in the both jejunum and the colon. Our studies established that dietary fat, especially saturated fat, potentiates the development of colon tumors caused by B(a)P in the Apc(Min) mouse.