Microsomal epoxide hydrolase and glutathione S-transferase polymorphisms in relation to laryngeal carcinoma risk

CypA: A Potential Target of Tumor Radiotherapy and/or Chemotherapy

Cyclophilin A (CypA) is a ubiquitous and highly conserved protein. CypA, the intracellular target protein for the immunosuppressant cyclosporine A (CsA), plays important cellular roles through peptidyl-prolyl cis-trans isomerase (PPIase). Increasing evidence shows that CypA is up-regulated in a variety of human cancers. In addition to being involved in the occurrence and development of multiple tumors, overexpression of CypA has also been shown to be strongly associated with malignant transformation. Surgery, chemotherapy and radiotherapy are the three main treatments for cancer. Chemotherapy and radiotherapy are often used as direct or adjuvant treatments for cancer. However, various side effects and resistance to both chemotherapy and radiotherapy bring great challenges to these two forms of treatment. According to recent reports, CypA can improve the chemosensitivity and/or radiosensitivity of cancers, possibly by affecting the expression of drug-resistant related proteins, cell cycle arrest and activation of the mitogen-activated protein kinase (MAPK) signaling pathways. In this review, we focus on the role of CypA in cancer, its impact on cancer chemotherapeutic and radiotherapy sensitivity, and the mechanism of action. It is suggested that CypA may be a novel potential therapeutic target for cancer chemotherapy and/or radiotherapy.

Multiple logistic regression analysis predicts cancer risk among tobacco usage with glutathione S-transferase p1 genotyping in patients with head and neck cancer

INTRODUCTION

Numerous studies have been investigated to understand the association between glutathione S-transferase P1 (GSTP1) polymorphism and risk of head and neck cancer (HNC) but yielded contradictory results, and no studies could confirm polymorphism in GSTP1 and that tobacco usage increases the risk of HNCs. Therefore, this study aimed to understand the association of GSTP1 Ile105Val polymorphism with or without tobacco usage in carcinogenesis and clinicopathological characteristics of patients with HNC.

MATERIALS AND METHODS

Binary logistic regression analysis was performed to predict HNC risk with tobacco use and GSTP1 genotyping. Five predictor variables such as gender, age, tobacco usage, familial, and GSTP1 genotypes were included in the model.

RESULTS

The results of the logistic regression analysis show that the full model which considered all the five independent variables together was statistically significant, log-likelihood = -111.820, and all slopes are zero: G = 74.297, degree of freedom (DF) = 5, P = 0.000. The strongest predictor in this model is tobacco usage (odds ratio = Z = -5.16, P = 0.000).

CONCLUSION

The study concludes that multiple logistic regression analysis model could predict the risk factors in case-control studies where control samples are compromised.

Glutathione S-transferase pi 1 variant and squamous cell carcinoma susceptibility: a meta-analysis of 52 case-control studies

Background

There are several meta-analyses on the genetic relationship between the rs1695 polymorphism within the GSTP1 (glutathione S-transferase pi 1) gene and the risk of different SCC (squamous cell carcinoma) diseases, such as ESCC (oesophageal SCC), HNSCC (head and neck SCC), LSCC (lung SCC), and SSCC (skin SCC). Nevertheless, no unified conclusions have been drawn.

Methods

Herein, an updated meta-analysis was performed to evaluate the probable impact of GSTP1 rs1695 on the susceptibility to different SCC diseases under six genetic models (allele, carrier, homozygote, heterozygote, dominant, and recessive). Three online databases, namely, PubMed, WOS (Web of Science), and Embase (Excerpta Medica Database), were searched.

Results

Initially, we obtained a total of 497 articles. Based on our selection criteria, we eventually included 52 case-control studies (9763 cases/15,028 controls) from 47 eligible articles. As shown in the pooling analysis, there was no difference in the risk of overall SCC disease between cases and controls [allele, P_a (P value of association test) = 0.601; carrier, P_a = 0.587; homozygote, P_a = 0.689; heterozygote, P_a = 0.167; dominant, P_a = 0.289; dominant, P_a = 0.548]. Similar results were obtained after stratification by race (Asian/Caucasian), genotyping, control source, and disease type (ESCC/HNSCC/LSCC/SSCC) (all P_a > 0.05).

Conclusion

The rs1695 polymorphism within the GSTP1 gene is not associated with the risk of overall SCC or a specific SCC type, including ESCC, HNSCC, LSCC, and SSCC.

GSTM1 polymorphism is related to risks of nasopharyngeal cancer and laryngeal cancer: a meta-analysis

Background

Accumulating data have reported that GSTM1 polymorphism may be related to nasopharyngeal cancer (NPC) and laryngeal cancer (LC). This meta-analysis was performed to investigate the relationship between GSTM1 polymorphism and risks of NPC and LC.

Methods

Pubmed, Embase, and China National Knowledge Infrastructure (CNKI) databases were searched for potential articles. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate the relationship of GSTM1 polymorphism with the risks of NPC and LC. I²>50% or P<0.05 indicates significant heterogeneity. When heterogeneity existed, the random-effects model was used to pool data, otherwise, the fixed-effects model was adopted. Publication bias was detected by Begg’s funnel plot and Egger’s regression. Quality of each study was evaluated by Newcastle-Ottawa Scale.

Results

Thirty-two eligible articles were included. Pooled outcome suggested the significant relationship of GSTM1 null genotype with increased risk of LC (OR =1.28, 95% CI =1.05–1.54). Compared with hospital-based (HB) population, GSTM1 null genotype was also related to increased risk of LC (OR =1.38, 95% CI =1.06–1.80). Positive relationship of GSTM1 null genotype with enhanced risk of NPC was observed (OR =1.43, 95% CI =1.26–1.63). A similar trend was also observed in the subgroup analysis by source of control (population-based [PB]: OR =1.39, 95% CI =1.18–1.63; HB: OR =1.52, 95% CI =1.22–1.89).

Conclusion

GSTM1 null genotype is related to increased risk of NPC and LC.

Heavy chain single-domain antibodies to detect native human soluble epoxide hydrolase

The soluble epoxide hydrolase (sEH) is a potential pharmacological target for treating hypertension, vascular inflammation, pain, cancer, and other diseases. However, there is not a simple, inexpensive, and reliable method to estimate levels of active sEH in tissues. Toward developing such an assay, a polyclonal variable domain of heavy chain antibody (VHH) sandwich immunoassay was developed. Ten VHHs, which are highly selective for native human sEH, were isolated from a phage-displayed library. The ten VHHs have no significant cross-reactivity with human microsomal epoxide hydrolase, rat and mouse sEH, and denatured human sEH. There is a high correlation between protein levels of the sEH determined by the enzyme-linked immunosorbent assay (ELISA) and the catalytic activity of the enzyme in S9 fractions of human tissues (liver, kidney, and lung). The VHH-based ELISA appears to be a new reliable method for monitoring the sEH and may be useful as a diagnostic tool for diseases influenced by sEH. This study also demonstrates the broad utility of VHH in biochemical and pharmacological research.

Systematic Review and Meta-Analysis of the Relationship between EPHX1 Polymorphisms and the Risk of Head and Neck Cancer

Aim

To evaluate the association between the EPHX1 Tyr113His and His139Arg polymorphisms in the EPHX1 gene and the risk of head and neck cancer.

Materials and Methods

Studies on the association of EPHX1 Tyr113His and His139Arg polymorphisms with HNC performed up until June 1st, 2014, were identified using a predefined search strategy. Summary odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate the strength of these associations.

Results

In this meta-analysis, 10 case-control studies, which included 9 studies of Tyr113His (1890 cases and 1894 controls) and 10 studies of His139Arg polymorphisms (1982 cases and 2024 controls), were considered eligible for inclusion. Overall, the pooled results indicated that the EPHX1 Tyr113His polymorphism was significantly associated with increased HNC risk (Tyr/His vs. Tyr/Tyr, OR = 1.26, 95%1.02–1.57;His/His+ Tyr/His vs. Tyr/Tyr, OR = 1.29, 95% I = 1.03–1.61). However, no significant association was found between the His139Arg polymorphism and HNC risk. In the subgroup analysis, a statistically significant association between the EPHX1 Tyr113His polymorphism and HNC was observed in population-based case-control studies (PCC), which involved less than 500 participants and genotype frequencies in HWE. This association showed minimal heterogeneity after excluding studies that were determined to contribute to heterogeneity. After categorizing the studies by publication time, a sensitivity analysis and cumulative meta-analysis of the two associations were conducted, and the results of the two analyses were consistent.

Conclusion

Our meta-analysis suggests that EPHX1 Tyr113His polymorphism may be a risk factor for HNC, while the EPHX1 His139Arg polymorphism has no association with HNC risk.

Quantitative assessment of the influence of EPHX1 gene polymorphisms and cancer risk: a meta-analysis with 94,213 subjects

Purpose

Previous studies investigating the association between EPHX1 polymorphisms (Tyr113His and His139Arg) and cancer risk have yielded inconsistent results. This meta-analysis was performed to derive a more precise estimation of relationship between two EPHX1 polymorphisms and risk of different types of cancer.

Methods

Data were extracted from relevant studies detected by a systematic literature search. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to assess the strength of the association between EPHX1 polymorphisms and cancer risk.

Results

This meta-analysis carefully collected 99 studies on these two polymorphisms and cancer risk published up to March 2014, consisting of 45 studies (20,091 cases and 27,396 controls) for Tyr113His and 54 studies (19,437 cases and 27,289 controls) for His139Arg. The results in overall population did not show any significant association between these two polymorphisms and cancer risk for all genetic models. However, EPHX1 Tyr113His homozygote individuals have a significantly increased risk of cancer among Asians (homozygote model: OR =1.46, 95% CI=1.05–2.03; recessive model: OR =1.39, 95% CI =1.10–1.76) and mixed population (homozygote model: OR =1.17, 95% CI =1.02–1.34; recessive model: OR =1.17, 95% CI =1.02–1.33), but not Caucasians.

Conclusion

His/His genotype of EPHX1 Tyr113His polymorphism is a risk factor for developing caner for Asian and mixed population, while no evidence was found for the association between the EPHX1 His139Arg polymorphism and increased cancer risk.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-014-0082-9) contains supplementary material, which is available to authorized users.

GSTM3 A/B polymorphism and risk for head and neck cancer: a meta-analysis

Background

Glutathione S-transferase M3 (GSTM3) is an important member of the GSTs that plays a critical role in the development of head and neck cancer (HNC). Several studies have investigated between the GSTM3 A/B polymorphism and risk of HNC, however, the results remain controversial. The aim of this meta-analysis is to evaluate the association between the GSTM3 A/B polymorphism and the risk of HNC.

Methods

All eligible case-control studies published up to July 2013 were identified by searching PubMed and Web of Science. The HNC risk associated with the GSTM3 A/B polymorphism was estimated for each study by odds ratios (OR) together with its 95% confidence interval (CI), respectively.

Results

Fourteen studies from ten publications with 2110 patients and 2259 controls were included. Overall, the GSTM3 A/B polymorphism was associated with a decreased risk of HNC using the dominant model, homozygote comparison model and heterozygote comparison model (OR = 0.82, 95%CI: 0.71–0.94; OR = 0.67, 95%CI: 0.49–0.94; and OR = 0.84, 95%CI: 0.73–0.97, respectively); besides, in stratification analyses by ethnicity, similar results were observed in Caucasian populations. Stratification by tumor site indicated that the GSTM3 polymorphism was associated with a decreased risk of laryngeal cancer under recessive model and homozygote comparison (OR = 0.52, 95%CI: 0.30–0.89; and OR = 0.50, 95%CI: 0.29–0.87, respectively); By stratifying source of control, decreased cancer risk was observed in hospital-based population under all genetic models (OR = 0.67, 95%CI: 0.56–0.81 for the dominant model; OR = 0.66, 95%CI: 0.46–0.95 for the recessive model; OR = 0.55, 95%CI: 0.37–0.83 for the homozygote comparison model, and OR = 0.70, 95%CI: 0.58–0.84 for the heterozygote comparison model).

Conclusions

This meta-analysis suggests that the GSTM3 A/B polymorphism may be an important protective factor for HNC, especially of laryngeal cancer and Caucasian populations.

Association of GSTP1 Ile105Val polymorphism and risk of head and neck cancers: a meta-analysis of 28 case-control studies

BACKGROUND AND AIMS

The Glutathione S-transferase P1 (GSTP1) polymorphism have been considered a risk modifier for developing head and neck cancer (HNC) in many studies; however, the results of such studies are inconsistent. The aim of this study was to evaluate the possible association between the GSTP1 Ile105Val polymorphism and risk of HNC.

METHOD

We performed a search in the relevant electronic database and a meta-analysis based on 28 published case-control studies that included 6,404 cases and 6,523 controls. To take into account the possibility of heterogeneity across the studies, a Chi-square based I(2)-statistic test was performed. Crude pooled odds ratios (ORs) with 95% confidence intervals (CIs) were assessed using both fixed-effects and random-effects models.

RESULTS

The results of this meta-analysis showed that the GSTP1 Ile105Val polymorphism was not significantly associated with risk of HNC in the overall study population (pooled OR 1.00, 95% CI 0.92-1.09) or in subgroup analyses stratified by ethnicity, sample size, tumor site or publication year. Moreover, substantial evidence of heterogeneity among the studies was observed. Publication year was identified as the main cause of heterogeneity.

CONCLUSION

This meta-analysis does not support a significant association between the GSTP1 Ile105Val polymorphism and risk of HNC.

Association between GSTM1 and GSTT1 allelic variants and head and neck squamous cell cancinoma

Backgrounds

GSTM1 and GSTT1 are involved in the detoxification of carcinogens such as smoking by-products, and polymorphisms in these two genes with a result of loss of enzyme activity may increase risk of carcinogenesis. Although many epidemiological studies have investigated the association between GSTM1 or GSTT1 null genotype and head and neck squamous cell carcinoma (HNSCC), the results remain conflicting. To elucidate the overall association of GSTM1, GSTT1 and HNSCC, we included all available studies and performed this meta-analysis.

Methodology/Principal Findings

A dataset including 42 articles for GSTM1, 32 articles for GSTT1, and 15 articles for GSTM1 and GSTT1 in combination were identified by a search in PubMed. Associations beween HNSCC and polymorphisms of GSTM1 and GSTT1 alone and in combination were analysed by software RevMan 5.1. Stratification analysis on ethnicity and smoking status, sensitivity analysis, heterogeneity among studies and their publication bias were also tested. Association was found in overall analysis between HNSCC and GSTM1 and GSTT1 null genotype. Stratified by ethnicity, we found increased risks of HNSCC in carriers with GSTM1 null genotype in Asian, GSTT1 null genotype in South American, and dual null genotype in European and Asian. When stratified by smoking, a more significant association of GSTM1 null genotype with HNSCC risk was observed in smokers.

Conclusions/Significance

This meta-analysis presented additional evidence of the association between GSTM1 and GSTT1 polymorphisms and HNSCC risk.

Quantitative assessment of the association between GSTM1 null genotype and laryngeal cancer risk

Previous studies investigating the association between glutathione S-transferase M1 (GSTM1) null genotype and laryngeal cancer risk reported controversial results. Thus, a meta-analysis was performed to clarify the effect of GSTM1 null genotype on laryngeal cancer risk. A literature search was performed for all possible studies. We estimated summary odd ratio (OR) with its 95 % confidence interval (95 % CI) to assess the association. Subgroup analyses were performed by ethnicity or the sample size. 24 individual case-control studies involving a total of 2,809 laryngeal cancer cases and 4,478 controls were finally included into this meta-analysis. Meta-analyses of total 24 studies showed the GSTM1 null genotype was significantly associated with increased laryngeal cancer risk (random-effects OR = 1.44, 95 % CI 1.19-1.73, P < 0.001). Subgroup analyses by ethnicity showed that the GSTM1 null genotype was associated with increased laryngeal cancer risk in both Caucasians (fixed-effects OR = 1.17, 95 % CI 1.04-1.33, P = 0.012) and Asians (random-effects OR = 1.89, 95 % CI 1.28-2.77, P = 0.001). Also, subgroup analyses by sample size also further identified this association above. The cumulative meta-analyses showed a trend of more obvious association between GSTM1 null genotype and increased risk of laryngeal cancer as information accumulated by year. Meta-analysis of available data suggests that GSTM1 null genotype contributes to increased laryngeal cancer risk in both Caucasians and East Asians.

Glutathione S-transferase M1 gene polymorphism and laryngeal cancer risk: a meta-analysis

BACKGROUND AND OBJECTIVES

Studies investigating the association between glutathione S-transferase M1 (GSTM1) gene polymorphism and laryngeal cancer risk have reported conflicting results. The aim of the present study was to conduct a meta-analysis assessing the possible associations of GSTM1 gene polymorphism with laryngeal cancer risk.

METHODS

The relevant studies were identified through a search of PubMed, Embase, ISI Web of Knowledge and Chinese National Knowledge Infrastructure until May 2011 and selected on the basis of the established inclusion criteria for publications, then a meta-analysis was performed to quantitatively summarize association of GSTM1 polymorphism with laryngeal cancer susceptibility.

RESULTS

Seventeen studies were included in the present meta-analysis (2,180 cases and 2,868 controls). The combined results based on all studies showed that GSTM1 null genotype was associated with increased laryngeal cancer risk (OR = 1.17, 95% CI = 1.04∼1.31). When stratifying for race, GSTM1 null genotype exhibited increased laryngeal cancer risk in Caucasians (OR = 1.15, 95% CI = 1.01∼1.31), while no significant association was detected in Asians (OR = 1.25, 95% CI = 0.80∼1.96). In the subgroup analysis based on source of controls, significant associations were observed in the population-based studies (OR = 1.15, 95% CI = 1.01∼1.31) yet not in the hospital-based studies (OR = 1.25, 95% CI = 0.93∼1.67). Furthermore, in the subgroup analysis based on sample size, significant associations were also found in studies with at least 50 cases and 50 controls (OR = 1.15, 95% CI = 1.02∼1.30) but not in studies with fewer than 50 cases or 50 controls (OR = 1.46, 95% CI = 0.87∼2.46).

CONCLUSIONS

This meta-analysis supported that the GSTM1 gene polymorphism was associated with laryngeal cancer, particularly in Caucasians, and these associations varied in different subgroup, which indicated that population-based study with larger sample size was more appropriate in design of future study.

Multiple pathway-based genetic variations associated with tobacco related multiple primary neoplasms

BACKGROUND

In order to elucidate a combination of genetic alterations that drive tobacco carcinogenesis we have explored a unique model system and analytical method for an unbiased qualitative and quantitative assessment of gene-gene and gene-environment interactions. The objective of this case control study was to assess genetic predisposition in a biologically enriched clinical model system of tobacco related cancers (TRC), occurring as Multiple Primary Neoplasms (MPN).

METHODS

Genotyping of 21 candidate Single Nucleotide Polymorphisms (SNP) from major metabolic pathways was performed in a cohort of 151 MPN cases and 210 cancer-free controls. Statistical analysis using logistic regression and Multifactor Dimensionality Reduction (MDR) analysis was performed for studying higher order interactions among various SNPs and tobacco habit.

RESULTS

Increased risk association was observed for patients with at least one TRC in the upper aero digestive tract (UADT) for variations in SULT1A1 Arg²¹³His, mEH Tyr¹¹³His, hOGG1 Ser³²⁶Cys, XRCC1 Arg²⁸⁰His and BRCA2 Asn³⁷²His. Gene-environment interactions were assessed using MDR analysis. The overall best model by MDR was tobacco habit/p53(Arg/Arg)/XRCC1(Arg³⁹⁹His)/mEH(Tyr¹¹³His) that had highest Cross Validation Consistency (8.3) and test accuracy (0.69). This model also showed significant association using logistic regression analysis.

CONCLUSION

This is the first Indian study on a multipathway based approach to study genetic susceptibility to cancer in tobacco associated MPN. This approach could assist in planning additional studies for comprehensive understanding of tobacco carcinogenesis.

Lack of association between glutathione S-transferase T1 gene polymorphism and laryngeal cancer susceptibility: a meta-analysis based on 2,124 cases and 2,059 controls

Studies investigating the association between glutathione S-transferase T1 (GSTT1) gene polymorphism and laryngeal cancer susceptibility have reported conflicting results. The aim of the present study was to conduct a meta-analysis assessing the possible association of GSTT1 gene polymorphism with laryngeal cancer risk. The relevant studies were identified through a search of PubMed, Embase, ISI Web of Knowledge and Chinese National Knowledge Infrastructure until May 2011. Twelve studies were included in the present meta-analysis, which described a total of 2124 laryngeal cancer cases and 2059 controls. The overall odds ratio (OR) for GSTT1 null genotype was 1.40 (95% CI=0.90-2.16). When stratifying for race, the pooled ORs for GSTT1 null genotype were 1.07 (95% CI=0.81-1.41) in Caucasians and 5.63 (95% CI=1.00-31.83) in Asians. The pooled ORs for GSTT1 null genotype were 1.03 (95% CI=0.71-1.49) in population-based studies and 2.39 (95% CI=0.73-7.86) in hospital-based studies, stratifying for study design. This meta-analysis suggested that there was lack of association between GSTT1 gene polymorphism and laryngeal cancer risk. However, larger scale primary studies are still required to further evaluate the interaction of GSTT1 gene polymorphism with laryngeal cancer risk.

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.

Development of fluorescent substrates for microsomal epoxide hydrolase and application to inhibition studies

The microsomal epoxide hydrolase (mEH) plays a significant role in the metabolism of numerous xenobiotics. In addition, it has a potential role in sexual development and bile acid transport, and it is associated with a number of diseases such as emphysema, spontaneous abortion, eclampsia, and several forms of cancer. Toward developing chemical tools to study the biological role of mEH, we designed and synthesized a series of absorbent and fluorescent substrates. The highest activity for both rat and human mEH was obtained with the fluorescent substrate cyano(6-methoxy-naphthalen-2-yl)methyl glycidyl carbonate (11). An in vitro inhibition assay using this substrate ranked a series of known inhibitors similarly to the assay that used radioactive cis-stilbene oxide but with a greater discrimination between inhibitors. These results demonstrate that the new fluorescence-based assay is a useful tool for the discovery of structure-activity relationships among mEH inhibitors. Furthermore, this substrate could also be used for the screening chemical library with high accuracy and with a Z' value of approximately 0.7. This new assay permits a significant decrease in labor and cost and also offers the advantage of a continuous readout. However, it should not be used with crude enzyme preparations due to interfering reactions.

Association of glutathione S-transferase, EPHX, and p53 codon 72 gene polymorphisms with adult acute myeloid leukemia

Polymorphisms in genes encoding detoxification enzymes have been suggested as susceptibility factors for many solid tumors. However, their association with hematological malignancies is controversial. A case-control study was done to determine the association between glutathione S-transferase M1 (GSTM1), GSTT1, GSTP1, EPHX1, and p53 codon 72 polymorphisms as risk factors in 120 adult acute myeloid leukemia (AML) cases and 202 healthy controls by polymerase chain reaction-restriction fragment length polymorphism techniques. Data were analyzed using χ(2) and conditional logistic regression model. None of the polymorphisms studied alone was associated with increased risk for AML. However, the frequency of GSTT1 null genotype was higher among controls (28.7%) than AML cases (21.6%), which showed a protective effect of the null genotype (odds ratio = 0.58, 95% confidence interval: 0.33-1.05, p = 0.07). In a combined analysis, both EPHX1 (His113His) and GSTP1 (Ile/Val) genes imparted a fourfold risk for adult AML but did not reach statistical significance (odds ratio = 4.22, 95% confidence interval: 0.992-17.99, p = 0.05). These findings suggest that the etiology of adult AML cannot be explained by polymorphism at a single locus, perhaps because of complexity involved in the metabolism of diverse xenobiotic compounds, and therefore, multiple gene-gene interactions should be investigated to predict the risk of AML.

Role of the CYP2D6, EPHX1, MPO, and NQO1 genes in the susceptibility to acute lymphoblastic leukemia in Brazilian children

Polymorphic variations of several genes associated with dietary effects and exposure to environmental carcinogens may influence susceptibility to leukemia development. The objective of the present study was to evaluate the effect of the polymorphisms of debrisoquine hydroxylase (CYP2D6), epoxide hydrolase (EPHX1), myeloperoxidase (MPO), and quinone-oxoreductase (NQO1), which have been implicated in xenobiotic metabolism, on the risk of childhood acute lymphoblastic leukemia (ALL). We evaluated the frequency of polymorphisms in the CYP2D6 (*3 and *4), EPHX1 (*2 and *3), MPO (*2), and NQO1 (*2) genes in 206 patients with childhood ALL and in 364 healthy individuals matched for age and gender from a Brazilian population separated by ethnicity (European ancestry and African ancestry), using the PCR-RFLP method. The CYP2D6 polymorphism variants were associated with an increased risk of ALL. The EPHX1, NQO1, and MPO variant genotypes were significantly associated with a reduced risk of childhood ALL. A significantly stronger protective effect is observed when the EPHX1, NQO1, and MPO variant genotypes are combined suggesting that, CYP2D6 polymorphisms may play a role in the susceptibility to pediatric ALL, whereas the EPHX1, NQO1, and MPO polymorphisms might have a protective function against leukemogenesis.

Polymorphisms of CYP1A1 and GSTM1 and laryngeal cancer risk: evidence-based meta-analyses

PURPOSE

Previous evidence implicates CYP1A1 and GSTM1 polymorphisms as risk factors for various cancers. A number of studies have been devoted to the association of CYP1A1 or GSTM1 polymorphism with susceptibility to laryngeal carcinoma, with the results inconsistent and inconclusive. The aim of the present study was to assess the possible associations of laryngeal cancer risk with CYP1A1 genetic variation and GSTM1 null genotype respectively.

METHODS

The associated literature was acquired through deliberate searching and selected based on the established inclusion criteria for publications, then the extracted data were further analyzed using systematic meta-analyses.

RESULTS

The results showed that the overall odds ratio (OR) was 1.32 (95% CI = 1.08-1.61) for CYP1A1 Mspl polymorphism. Using subgroup analysis, the pooled ORs were 1.38 (95% CI = 0.98-1.95) in Asians and 1.29 (95% CI = 1.01-1.65) in Caucasians. For CYP1A1 exon7 polymorphism, the overall OR was 1.38 (95% CI = 0.98-1.95). The overall OR was 1.24 (95% CI = 1.03-1.49) for GSTM1 polymorphism and the pooled ORs were 1.36 (95% CI = 0.75-2.48) in Asians, 1.16 (95% CI = 0.94-1.44) in Caucasians and 1.52 (95% CI = 1.05-2.19) in Turkey population.

CONCLUSIONS

The data suggest CPY1A1 MspI polymorphism as a risk factor for laryngeal cancer in Caucasians but not in Asians. However, the results suggest a marked correlation of GSTM1 polymorphism with laryngeal cancer risk in Turkey population but not Caucasians and Asians.

Relevance of glutathione S-transferase M1 and cytochrome P450 1A1 genetic polymorphisms to the development of head and neck cancers

BACKGROUND

Cytochrome P450 (CYP) and glutathione S-transferase (GST) gene variants have been intensively investigated for their implication in the development of different neoplasms.

METHODS

In the present study, we analyzed genetic polymorphisms of CYP1A1, GSTM1, GSTP1, and GSTT1 in 127 head and neck cancer patients and 151 hospital controls.

RESULTS

No significant increase in risk in patients with the GSTM1 null genotype (OR=1.52, 95% CI: 0.93-2.49) or CYP1A1 462Val alleles (OR=1.60, 95% CI: 0.73-3.52) or GSTP1 105Val alleles (OR=0.97, 95% CI: 0.59-1.58) was observed. The GSTT1 null genotype was found in 30.5% of the controls and 21.3% of the head and neck cancer patients (p=0.15). The estimated head and neck cancer risk for the combination of either CYP1A1 Ile462Val or CYP1A1 Val462Val genotype with either GSTP1 Ile105Val or Val105Val genotype (OR=2.89, 95% CI: 0.71-11.71) and for the combination of either CYP1A1 Ile462Val or CYP1A1 Val462Val genotype with GSTT1 null genotype (OR=2.62, 95% CI: 0.64-10.85) suggested the absence of the modifying effect of combined variant alleles on head and neck cancer susceptibility. The joint effect of either CYP1A1 Ile462Val or CYP1A1 Val462Val genotype with GSTM1 null genotype significantly increased the risk of head and neck cancer (OR=7.15, 95% CI: 1.49-34.32).

CONCLUSIONS

Our findings corroborate metabolic genes interactions, especially for CYP1A1 462Val alleles and GSTM1 homozygous deletion, in the development of head and neck cancer in the investigated population groups in Poland.

CYP1A1, mEH, and GSTM1 Polymophisms and Risk of Oral and Pharyngeal Cancer: A Spanish Case-Control Study

Background. Genetic polymorphisms of drug metabolizing enzymes involved in the detoxification pathways of carcinogenic substances may influence cancer risk. Methods. Case-control study that investigates the relationship between CYP1A1 Ile/Val, exon 4 mEH, and GSTM1 null genetic polymorphism and the risk of oral and pharyngeal cancer examining the interaction between these genes, tobacco, and alcohol. 92 incident cases and 130 consecutive hospital-based controls have been included. Results. No significant associations were found for any of the genotypes assessed. The estimated risk was slightly elevated in subjects with the wild type of the mEH gene and the null GSTM1 genotype. For exon 4 mEH heterozygous polymorphism, the risk was slightly lower for heavy smokers than for light smokers. The inverse association was observed for the GSTM1 null genotype. Conclusions. The results suggest that exon 4 mEH and GSTM1 null polymorphisms might influence oral and pharyngeal cancer.

Microsomal epoxide hydrolase genotypes and the risk for head and neck cancer

BACKGROUND

Microsomal epoxide hydrolase (mEH) is an enzyme involved in the metabolism of (pre)carcinogens in tobacco smoke. We investigated whether functional genetic polymorphisms in mEH may have a risk-modifying effect on head and neck carcinogenesis.

METHODS

Blood from 429 patients with oral, pharyngeal, and laryngeal carcinoma and 419 healthy subjects was investigated for mEH polymorphisms.

RESULTS

Logistic regression analysis did not show differences in mEH genotype distributions between patients and controls, when categorized according to predicted mEH enzyme activity. Also no differences were found when evaluated according to tumor localization, sex, or tobacco consumption. A significantly higher incidence of the 139Arg/Arg variant was found in patients with hypopharyngeal carcinoma compared with controls (OR = 4.39, 95% CI = 1.45 to 13.35).

CONCLUSION

In contrast to earlier reports, we could not demonstrate a risk-modifying effect of genetic polymorphisms in mEH on head and neck carcinogenesis, except for the predicted high activity variant in patients with hypopharyngeal carcinoma.

GSTT1 and GSTM1 polymorphism in cigarette smokers with head and neck squamous cell carcinoma

Gene variability related to carcinogen activation and detoxification may interfere with susceptibility to head and neck cancer.

Aim

To investigate the relation between GSTT1 and GSTM1 null polymorphisms and the risk of head and neck squamous cell carcinoma in cigarette smokers.

Material and Method

A case-control study conducted at the Sao Jose do Rio Preto Medical School, Brazil. GSTM1 and GSTT1 null genotype frequencies were evaluated by multiplex PCR in ⁴⁵ cigarette smokers with head and neck squamous cell carcinomas and ⁴⁵ cigarette smokers without this disease.

Results

The oral cavity was the most prevalent tumor site for squamous cell carcinoma. The GSTT1 null genotype was found in 33.3% of the Experimental Group and 23.3% of the Control Group (p= 0.311). Experimental and Control Groups had GSTM1 null genotype frequencies of 35% and 48.3% (p=0.582). No association between alcohol consumption and GSTT1 and GSTMI null genotypes was found in these groups (p-values>0.05). There were more men, and alcohol consumption was prevalent in both groups.

Conclusion

In this study we were unable to show a correlation between GSTM1 and GSTT1 genotypes and the development of head and neck squamous cell carcinomas in cigarette smokers.

Association of periodontitis with GSTM1/GSTT1-null variants—A pilot study

OBJECTIVES

To analyze a possible association between glutathione-S-transferase T1 (GSTM1) and/or glutathione-S-transferase M1 (GSTM1) polymorphisms and chronic or aggressive forms of periodontitis in a Caucasian ethnic group.

DESIGN AND METHODS

Sixty-nine chronic, 14 aggressive periodontitis and 61 controls, deeply analyzed from a clinical point of view, were studied for their GSTM1 and GSTT1 polymorphisms by allelic specific PCR techniques. As a second control group, 64 blood donors were also included.

RESULTS

A significant association was found between GSTM1-null genotype and both chronic and aggressive periodontitis. The aggressive forms were associated with the double null GSTM1 and GSTT1 combination. These results were independent of the patients' age, gender, hygienic habits and smoke (evaluated as tobacco smoking yes/no, cigarettes/day and pack years) as confirmed by multivariate logistic regression analysis.

CONCLUSIONS

The GSTM1-null variant is statistically associated with the two forms of periodontitis, while the aggressive one also presents a second null variant: GSTT1.

CYP1A1, CYP2E1, GSTM1, GSTT1, EPHX1 exons 3 and 4, and NAT2 polymorphisms, smoking, consumption of alcohol and fruit and vegetables and risk of head and neck cancer

PURPOSE

As risk-modifiers of alcohol and tobacco effects, metabolic genes polymorphisms were investigated as susceptibility candidates for squamous cell carcinoma of the head and neck (SCCHN).

METHODS

A total of 210 cases and 245 hospital controls, age and gender matched, were genotyped for CYP1A1, CYP2E1, GSTM1, GSTT1, EPHX1 exons 3 and 4, and NAT2 polymorphisms. A measurement of the biological interaction among two risk factors was estimated by the attributable proportion (AP) due to interaction and its 95% confidence interval (CI).

RESULTS

SCCHN risk was associated with high-levels of alcohol intake [OR = 3.50 (95%CI: 1.93-6.35) and OR = 6.47 (95%CI: 2.92-14.35) for 19-30 g/day and >30 g/day, respectively], cigarette smoking [OR = 3.47 (95%CI: 1.88-6.41) and OR = 7.65 (95%CI: 4.20-13.90) for 1-25 and >25 pack-years of smoking, respectively] and low-fruit and vegetables consumption (OR = 2.45; 95%CI: 1.53-3.92). No differences were observed for the genotypes or haplotypes distributions among cases and controls, and no biological interaction emerged from gene-gene and gene-environment interaction analyses. An attributable proportion (AP) due to biological interaction of 0.65 (95%CI: 0.40-0.90) was detected for heavy drinkers with a low intake of fruit and vegetables, and an AP of 0.40 (95%CI: 0.10-0.72) resulted forever smokers with low fruit and vegetables consumption.

CONCLUSIONS

Even in presence of high alcohol consumption or cigarette smoking, a high intake of fruit and vegetables might prevent the development of around one quarter of SCCHN cases. The lack of interaction between the studied polymorphisms and the environmental exposures suggests that chronic consumption of tobacco and alcohol overwhelm enzyme defences, irrespective of genotype.

Glutathione S-transferase polymorphisms and the synergy of alcohol and tobacco in oral, pharyngeal, and laryngeal carcinoma

Investigations of the ability of polymorphisms in the GSTM1, GSTT1, and GSTP1 genes to alter susceptibility to head and neck squamous cell carcinoma (HNSCC) have examined gene-environment interaction in their detoxification of tobacco-associated carcinogens. Little work has been done to ask if these variant genes also modify the interaction of tobacco and alcohol in the development of HNSCC. To test this hypothesis, we conducted a case-control study, enrolling 692 incident cases of HNSCC and 753 population controls. Information about lifetime tobacco and alcohol use was ascertained through questionnaires, and genotypes for GSTM1, GSTT1, and GSTP1 were determined from constitutional DNA. Genotype frequencies were compared among cases and controls, and the association between genotypes and tobacco use was evaluated on cancer risk through logistic regression. Deletion of GSTM1 was associated with an increased risk for HNSCC [odds ratio (OR), 1.3; 95% confidence interval (95% CI), 1.0-1.6]. GSTT1 deletion was associated with a slight decreased HNSCC risk (OR, 0.8; 95% CI, 0.6-1.0). Among those with GSTM1 present, the OR of cancer for heavy smoking was 2.6 (95% CI, 1.6-4.3) compared with 4.2 for those with the GSTM1 deleted (95% CI, 2.6-6.7). The combination of consuming 10 to 20 alcohol drinks weekly and smoking >45 pack-years was associated with a 13-fold elevated risk (OR, 12.6; 95% CI, 4.0-40.2) among the GSTM1 deleted subjects compared with an OR of 3.6 (95% CI, 1.5-8.7) among the GSTM1 present individuals. These data (showing that the GSTM1 deletion affects on the tobacco and alcohol synergy) suggest that the interaction of these carcinogens is, at least in part, driven by alcohol, enhancing the carcinogenic action of tobacco smoke.

Oligo-microarray analysis reveals the role of cyclophilin A in drug resistance

Cyclophilin A (CYPA) belongs to peptidyl prolyl isomerases (PPIases), which catalyze the cis/trans isomerization of prolyl peptide bonds in cellular communication. CYPA has been implicated in several pathological processes, including cancer, inflammatory diseases, and HIV-1 infection. Up-regulation of CYPA has been found to be a common phenomenon in several tumor types, including in hepatocellular carcinoma (HCC). However, the role of CYPA in tumor cells remains unknown. We generated a stable SK-Hep1 cell line and studied the CYPA regulated genes at the transcriptome level. The microarray results reveal that CYPA can up-regulate the expression of many cytokine and drug resistance related genes. Furthermore, we showed that the elevated CYPA expression contributes to drug resistance. We postulate that the over-expression of CYPA in tumors may play a role in clinical resistance to chemotherapy.

Polymorphisms of microsomal epoxide hydrolase and glutathione S-transferase P1 in a male Turkish population

Polymorphic genes encoding drug-metabolizing enzymes may account for interindividual differences in certain types of diseases especially cancer. In this study, microsomal epoxide hydrolase (EPHX1) and glutathione S-transferase P1 (GSTP1) gene polymorphisms were determined among 133 healthy males of a Turkish population. Frequencies of EPHX1 and GSTP1 gene polymorphisms were determined by using the polymerase chain reaction-restriction fragment length polymorphism (PCR/RFLP) method. The observed genotype frequencies of EPHX1 exon 3 were Tyr113Tyr:50.4%, Tyr113His: 42.1%, His113His: 7.5% and EPHX1 exon 4 were His139His: 69.2%, His139Arg: 28.6%, Arg133Arg: 2.2%. GSTP1 exon 5 genotype frequencies were Ile105Ile: 58.7%, Ile105Val: 35.3%, Val105Val: 6.0% and GSTP1 exon 6 genotype frequencies were Ala114Ala: 85.0%, Ala114Val: 14.3%, Val114Val: 0.7%. These results reveal that the frequencies of EPHX1 and GSTP1gene polymorphisms in a small sampling of males within a Turkish population are similar to European Caucasian populations.

Polymorphism of selected enzymes involved in detoxification and biotransformation in relation to lung cancer

Available data indicate that there are significant differences in individual susceptibility to lung cancer within the human population. It is believed to be underlie by inherited genetic predispositions related to the genetic polymorphism of several enzymes involved in the detoxification and xenobiotic metabolism. In this review, we collect and discuss the evidence reported up to date on the association between lung cancer and genetic polymorphism of cytochromes P450, N-acetyltransferase, glutathione S-transferases, microsomal epoxide hydrolase, NAD(P)H:quinone oxidoreductase, myeloperoxidase and glutathione peroxidase. All these genes might appear to be candidates for lung cancer susceptibility genes, nevertheless, the present state of the art still offers only a limited explanation of the link between such polymorphisms and increased risk of lung cancer.

Relation of glutathione S-transferase genotypes (GSTM1 and GSTT1) to laryngeal squamous cell carcinoma risk

The purpose of the present study was to investigate GSTM1 and GSTT1 genotypes by using multiplex polymerase chain reaction (PCR) in patients with laryngeal squamous cell carcinoma (LSCC). The genotypes of 110 patients with LSCC and of 197 healthy subjects as the control group were determined by PCR analysis for GSTM1 and GSTT1 genes. Results showed that frequencies of GSTM1-null, GSTT1-null, and both GSTs-null genotypes were 51.8, 30, and 16.4%, respectively, in the patients with LSCC and 37.6, 15.7, and 5.6% in the control group. There was a significant difference between the genotype distributions of all GSTs in patients and in control groups (P < 0.05). The results support the hypothesis that null genotypes of GSTM1 and GSTT1 can reduce detoxification capacity of GSTs as members of the xenobiotic enzyme system. GSTM1-null, GSTT1-null, and both GSTs-null genotypes were more common in the patients with LSCC than in the control group. Patients with both GSTs-null genotypes had the highest risk for supraglottic LSCC in the early period, even if they were light-to-medium smokers. Investigation and determination of the genetic basis of LSCC may contribute to detection of risk groups and to prevent LSCC in the population.

GSTT1 and GSTM1 allelic polymorphisms in head and neck cancer patients from Italian Lazio Region

BACKGROUND

The association between head and neck squamous cell carcinoma (HNSCC) and allelic variants of glutathione S-transferase M1 (GSTM1) and -T1 (GSTT1) is currently controversial. The present study investigates the prevalences of GSTT1 and GSTM1 polymorphism in a cohort of 100 head and neck cancer patients, 100 healthy donors and 200 controls with non-neoplastic head and neck diseases from Italian Lazio Region.

METHODS

The patients with benign head and neck pathologies, as well as the healthy donors were matched for age, sex, cigarette smoke (yes/no) and alcohol consumption (yes/no). Molecular definition of GSTT1 and GSTM1 genotype has been performed by means of allele-specific PCR technique.

RESULTS

A significant association between head and neck cancer and GSTM1 null genotype was observed both considering benign disease controls (p=0.001, OR=2.613; 95% C.I.=1.48-4.62), and healthy donors (p=0.0003, OR=3.35; 95% C.I. 1.69-6.67) while no significant association was found with GSTT1 null genotype (p>or=0.14). No interactive association was observed when combining the different genotypes of the two polymorphisms. These results were confirmed after correction for daily number of cigarettes and period of tobacco exposure.

CONCLUSIONS

The present study confirms a role for genetic alterations of GSTM1 detoxifying enzyme as a risk factor for the development of HNSCC in patients from the Italian Lazio Region, independently of age, sex and other confounding variables.

EPHX1 gene polymorphisms and individual susceptibility to lung cancer

We investigated the roles of EPHX1 Tyr113His and His139Arg polymorphisms in lung cancer susceptibility in a Finnish study population comprising of 230 lung cancer cases and a large control group (n=2105). The controls were distributed into five age strata, which enabled us to examine the potential age-related changes in the putative EPHX1 at-risk genotypes in the cancer free population. Although the exon 3 slow activity associated allele (His113) containing genotypes posed a decreased lung cancer risk compared with the homozygous wild-type Tyr113/Tyr113 genotype (OR, 0.68; 95% CI, 0.49-0.94), no association was seen for the EPHX1 phenotypes interpreted from the combined exons 3 and 4 genotype data. Neither was any difference seen in the prevalence of the EPHX1 Tyr113His genotypes or interpreted EPHX1 phenotypes in the different age groups.

Epoxide hydrolases: mechanisms, inhibitor designs, and biological roles

Organisms are exposed to epoxide-containing compounds from both exogenous and endogenous sources. In mammals, the hydration of these compounds by various epoxide hydrolases (EHs) can not only regulate their genotoxicity but also, for lipid-derived epoxides, their endogenous roles as chemical mediators. Recent findings suggest that the EHs as a family represent novel drug discovery targets for regulation of blood pressure, inflammation, cancer progression, and the onset of several other diseases. Knowledge of the EH mechanism provides a solid foundation for the rational design of inhibitors, and this review summarizes the current understanding of the catalytic mechanism of the EHs. Although the overall EH mechanism is now known, the molecular basis of substrate selectivity, possible allosteric regulation, and many fine details of the catalytic mechanism remain to be solved. Finally, recent development in the design of EH inhibitors and the EH biological role are discussed.

Use of biomarkers to elucidate genetic susceptibility to cancer

Genetic variations have generally been accepted to be the major mechanism for the differences observed in susceptibility to cancer. However, extensive investigations on genotype-disease associations have not produced consistent results. The inconsistency may be caused by many factors, such as improper study design, insufficient sample size, complexity of the traits under investigation, heterogeneity of the study subjects, incorrect assumptions about the underlying genetic architecture, misclassification of the disease, improper selection of potential alleles, and overinterpretation of the data. Besides these "traditional" factors, a recent problem is that the function of many variant genotypes is unknown, especially with regard to polymorphic DNA repair genes. Therefore, in addition to the genotype-disease relationship, it may be prudent to step back and investigate the fundamental role of genetic variation in the development of cancer. The latter studies may focus on understanding the genotype-exposure interactions and evaluating genotype-health risk associations. This review will emphasize the use of relevant biomarkers and polymorphic DNA repair genes for investigations. These data will be useful for a better understanding of the complexity of disease causation and development, developing new models for human disease, and identifying pathways for prevention of cancer.

Glutathione S-transferase polymorphisms and survival from head and neck cancer

BACKGROUND

The purpose of this study was to evaluate the prognostic ability of polymorphisms of three genes involved in the metabolism of tobacco carcinogens (GSTT1, GSTM1, GSTP1) and one polymorphism of a DNA repair gene (XRCC1) for patients diagnosed with squamous cell carcinoma (SCC).

METHODS

Cox proportional hazard models were used to estimate risk of death for a prospective cohort of 190 patients.

RESULTS

Individuals with the GSTT1 functional genotype were twice as likely to die from any cause (hazard ratio [HR], 2.4; 95% confidence interval [CI], 1.13-4.97) and were three times as likely to die from SCC (HR, 3.4; 95% CI, 1.33-8.41) after adjustment for age, primary therapy, and stage of disease. The XRCC1 399 Gln genotype was predictive of disease recurrence.

CONCLUSIONS

Our findings, from one of the first studies to examine this research question, suggest that genomic markers of carcinogen metabolism and DNA repair capability may serve as prognostic indicators of disease recurrence and death.

Epoxide hydrolases: their roles and interactions with lipid metabolism

The epoxide hydrolases (EHs) are enzymes present in all living organisms, which transform epoxide containing lipids by the addition of water. In plants and animals, many of these lipid substrates have potent biologically activities, such as host defenses, control of development, regulation of inflammation and blood pressure. Thus the EHs have important and diverse biological roles with profound effects on the physiological state of the host organisms. Currently, seven distinct epoxide hydrolase sub-types are recognized in higher organisms. These include the plant soluble EHs, the mammalian soluble epoxide hydrolase, the hepoxilin hydrolase, leukotriene A4 hydrolase, the microsomal epoxide hydrolase, and the insect juvenile hormone epoxide hydrolase. While our understanding of these enzymes has progressed at different rates, here we discuss the current state of knowledge for each of these enzymes, along with a distillation of our current understanding of their endogenous roles. By reviewing the entire enzyme class together, both commonalities and discrepancies in our understanding are highlighted and important directions for future research pertaining to these enzymes are indicated.

Benzo(a)pyrene Diolepoxide (BPDE)-DNA Adduct Levels in Leukocytes of Smokers in Relation to Polymorphism of CYP1A1, GSTM1, GSTP1, GSTT1, and mEH

Benzo(a)pyrene [B(a)P] diolepoxide (BPDE)-DNA adducts were measured in the leukocytes of 41 healthy smokers using high-performance liquid chromatography coupled with a fluorimetric detector. The correlation between exposure to B(a)P through smoking and BPDE-DNA adduct levels was poor (r = 0.31), although subjects in the high exposure group [B(a)P &gt; 50 ng/d] had a slightly higher level of adducts compared with the less exposed group (mean ± SE, 1.70 ± 0.3 versus 1.09 ± 0.1; P = 0.057). We studied the effect on BPDE-DNA adducts of individual variations in genes controlling B(a)P metabolism, classifying subjects in “low-risk” and “high-risk” genotypes for smoking-related B(a)P DNA damage. The high-risk group included subjects characterized by a combination of increased B(a)P activation [cytochrome P450 1A1 (CYP1A1) MspI and/or exon 7 Ile462Val allele variants and microsomal epoxide hydrolase (mEH) fast activity] and decreased deactivation ability [presence of glutathione S-transferase M1 (GSTM1) null allele and wild-type glutathione S-transferase P1 (GSTP1)]. The low-risk group included smokers with lower B(a)P activation (wild-type CYP1A1, low or intermediate mEH activity) and higher deactivation capacity (active GSTM1, GSTP1 Ile105Val allele). Subjects in the low-risk group had lower levels of BPDE-DNA adducts compared with subjects in the high-risk genotype group; this difference was significant using two markers (CYP1A1 and GSTM1, median ± SD, 0.77 ± 1.16 versus 1.89 ± 0.39; P = 0.03) or three markers (CYP1A1, GSTM1, and GSTP1, median ± SD, 0.66 ± 0.93 versus 1.43 ± 1.17; P = 0.013). The discrimination between groups was reduced when including mEH as an additional marker (P = 0.085). In conclusion, CYP1A1, GSTM1, and GSTP1 genotyping seems to be a risk predictor of BPDE-DNA adduct formation in leukocytes.