Increased risk for acute myeloid leukaemia in individuals with glutathione S-transferase mu 1 (GSTM1) and theta 1 (GSTT1) gene defects

Genetic variability in cisplatin metabolic pathways and outcome of locally advanced head and neck squamous cell carcinoma patients

Advanced head and neck squamous cell carcinoma (HNSCC) patients have been treated with cisplatin (CDDP) chemoradiation, and the variability of treatment effects has been attributed to single nucleotide variants (SNVs) in genes of metabolic pathways. This study investigated the roles of GSTM1, GSTT1, GSTP1 c.313A>G, XPC c.2815A>C, XPD c.934G>A and c.2251A>C, XPF c.2505T>C, ERCC1 c.354C>T, MLH1 c.93G>A, MSH2 c.211+9C>G, MSH3 c.3133G>A, EXO1 c.1765G>A, TP53 c.215G>C, CASP3 c.-1191A>G and c.-182-247G>T, FAS c.-1378G>A and c.-671A>G and FASL c.-844C>T SNVs in outcome of 109 patients treated with CDDP chemoradiation. Genotypes were identified in genomic DNA by PCR-based methods. Conventional criteria and tests analyzed response and survival. Patients with XPC c.2815AC or CC had 3.43 times more chances of presenting partial response or stable disease. Patients with FAS c.-671GG, GSTM1 present plus XPC c.2815AA, or plus XPD c.934GG, or plus XPD c.2251AA, or plus TP53 c.215GC or CC, and XPD c.2251AA plus XPF c.2505TT had up to 2.70 and 2.37 times more chances of presenting tumor progression and evolving to death, respectively. Our data indicate, for the first time, preliminary evidence that combined SNVs of CDDP metabolism act as independent prognostic factors and can be used to select patients for distinct treatments.

Individual and combined effects of the GSTM1, GSTT1, and GSTP1 polymorphisms on leukemia risk: An updated meta-analysis

Background: Several meta-analyses have analyzed the association of GSTM1 present/null, GSTT1 present/null, and GSTP1 IIe105Val polymorphisms with leukemia risk. However, the results of these meta-analyses have been conflicting. Moreover, they did not evaluate the combined effects of the three aforementioned gene polymorphisms. Furthermore, they did not appraise the credibility of the positive results. Finally, many new studies have been published. Therefore, an updated meta-analysis was conducted.

Objectives: To further explore the relationship of the three aforementioned gene polymorphisms with leukemia risk.

Methods: The crude odds ratios (ORs) and 95% confidence intervals (CIs) were applied to evaluate the association of the individual and combined effects of the three aforementioned genes. Moreover, the false-positive report probability (FPRP) and Bayesian false discovery probability (BFDP) were applied to verify the credibility of these statistically significant associations.

Results: Overall, the individual GSTM1, GSTT1, and GSTP1 IIe105Val polymorphisms added leukemia risk. On combining GSTM1 and GSTT1, GSTM1 and GSTP1, and GSTT1 and GSTP1 polymorphisms, positive results were also observed. However, no significant association was observed between the combined effects of these three polymorphisms with leukemia risk in the overall analysis. Moreover, when only selecting Hardy–Weinberg equilibrium (HWE) and medium- and high-quality studies, we came to similar results. However, when the FPRP and BFDP values were applied to evaluate the credibility of positive results, the significant association was only observed for the GSTT1 null genotype with leukemia risk in Asians (BFDP = 0.367, FPRP = 0.009).

Conclusion: This study strongly suggests a significant increase in the risk of leukemia in Asians for the GSTT1 null genotype.

Association Between the Individual and Combined Effects of the GSTM1 and GSTT1 Polymorphisms and Risk of Leukemia: A Meta-Analysis

Background: Fourteen meta-analyses reported the individual effects of the GSTM1 and GSTT1 polymorphisms on leukemia risk. However, over 40 studies were not included in previously published meta-analyses. Moreover, one key aspect was that previous meta-analyses did not conduct the false-positive test on the aforementioned issues. Furthermore, previous meta-analyses did not observe the combined effects of GSTM1 present/null and GSTT1 present/null polymorphism with leukemia risk. Therefore, we conducted the current study to further analyze these associations. Objectives: This study aimed to investigate the association between the individual and combined effects of the GSTM1 present/null and GSTT1 present/null polymorphisms and the risk of leukemia. Methods: A meta-analysis was performed applying Meta-analyses of Observational Studies in Epidemiology (MOOSE) guidelines. Moreover, false-positive report probability (FPRP) and Bayesian false discovery probability (BFDP) were applied to investigate the false-positive results. Results: The individual GSTM1 and GSTT1 null genotypes and combined effects of the two genes were associated with a significantly increased leukemia risk in overall and several subgroup analyses, such as Asians, Caucasians, and so on. Then, further analysis was conducted using FPRP and BFDP. Significant associations were considered as "positive" results on the GSTM1 null genotype with leukemia risk in overall populations (FPRP < 0.001 and BFDP = 0.006), Asians (FPRP < 0.001 and BFDP < 0.001), and East Asian population (FPRP < 0.001 and BFDP = 0.002). For the GSTT1 null genotype, significant associations were regarded "positive" results in overall populations, acute myeloid leukemia (AML), Asians, and East Asian population. For the combined effects of the GSTM1 and GSTT1 polymorphisms, significant associations were also considered "positive" results in the overall analysis of Asians, Indians, and East Asian population. Conclusion: This study strongly indicates that the individual GSTM1 and GSTT1 null genotypes and combined effects of the two genes are associated with increased leukemia risk in Asians, especially in the East Asian population; the GSTT1 null genotype is associated with increased AML risk; the combined effects of the two genes are associated with increased leukemia risk in Indians.

Genetic polymorphism of drug metabolism enzymes (GSTM1, GSTT1 and GSTP1) in the healthy Malian population

Glutathione S-transferase genes, known to be highly polymorphic, are implicated in the process of phase II metabolism of many substrates, including xenobiotics, anticancer and anti-infective drugs. The detoxification activity is linked to individual genetic makeup. Therefore, the identification of alleles and genotypes in these genes within a population may help to better design genetic susceptibility and pharmacogenetic studies. We performed the present study to establish the frequencies of the GSTM1, GSTT1, and GSTP1 c. 313A > G (rs1695) polymorphisms in 206 individuals of the Malian healthy population. GSTM1 and GSTT1 were genotyped by using multiplex polymerase chain reaction, whereas genotypes of GSTP1 were identified by polymerase chain reaction followed by restriction fragment length polymorphism. The frequencies of GSTM1-null and GSTT1-null genotypes were respectively 24.3 and 41.3%. The observed genotype frequencies for GSTP1 were 25.73% homozygous wild-type AA, 49.03% heterozygous AG and 25.24% homozygous mutant GG. The frequency of GSTP1-A allele was 50.24% versus 49.76% for the GSTP1-G allele. The distribution of these three genes was homogeneous between men and women (p > 0.05). We found no statistical association between the presence of a particular profile of GSTM1 or GSTT1 with the genotypes of GSTP1 (p > 0.05). Nevertheless, we noticed that the majority of the individuals harboring the GSTM1-present or the GSTT1-present harbor also the GSTP1-AG genotype. In addition, the triple genotype GSTM1-present/GSTT1-present/AG was the most frequent with 25.2%. Our findings will facilitate future studies regarding genetic associations of multifactorial diseases and pharmacogenetic, thus opening the way to personalized medicine in our population.

Association between polymorphisms in xenobiotic detoxification-related genes with prognosis of epithelial ovarian cancer

This study aimed to evaluate whether GSTM1 and GSTT1 (presents or nulls), GSTP1 c.313A>G and NQO2 c.-102A>C polymorphisms, involved in xenobiotic detoxification pathways, alter outcomes of epithelial ovarian cancer (EOC) patients. DNA from 84 EOC patients diagnosed at the University of Campinas Academic Hospital from January 1995 and July 2007 was analyzed by polymerase chain reaction and restriction fragment length polymorphism assays. The prognostic impact of genotypes of polymorphisms on progression-free survival and overall survival (OS) of EOC patients was examined using the Kaplan-Meier probability estimates and univariate and multivariate Cox proportional hazard ratio (HR) regression analyses. The significant results of Cox analyses were validated using a bootstrap resampling study (1000 replications). At 60 months of follow-up, lower OS was seen in patients with GSTT1 null genotype (50.0 vs. 76.7 %, P = 0.02) compared with the other genotype (Kaplan-Meier estimate). This outcome remained the same in univariate Cox analysis (HR 2.22, P = 0.02). After multivariate Cox analysis, patients with GSTT1 null (HR 2.11, P = 0.04, P bootstrap = 0.04) and NQO2 AA (HR 2.13, P = 0.03, P bootstrap = 0.04) genotypes were under greater risks of progressing to death when compared with those with others genotypes. Our data suggest, for the first time, that inherited abnormalities in xenobiotic detoxification pathway related to GSTT1 and NQO2 c.-102A>C polymorphisms act as independent prognostic factors for OS of EOC patients.

Polymorphism in the SIRT1 gene and parameters of metabolic syndrome in a sample of the adult Brazilian population

ABSTRACT Objective: To evaluate whether the single nucleotide polymorphism rs7895833 (A/G) of the gene SIRT1 is associated with metabolic syndrome criteria in a sample of Brazilian adults. Methods: Serum samples and oral mucosal cells were collected from 243 subjects aged 30 to 70 years. Biochemical, hormonal, and anthropometric data were obtained. The single nucleotide polymorphism rs7895833 (A/G) was analyzed by polymerase chain reaction using the amplification refractory mutation system. Results: Among the 243 study subjects, 100 (41.15%) were classified as non-metabolic syndrome and 143 (58.85%), as metabolic syndrome. The frequency of the single nucleotide polymorphism rs7895833 (A/G) did not differ between the groups. However, 111 patients (45.67%) were overweight (body mass index: 25-29.9 kg/m2). Blood glucose, total cholesterol, triglycerides, very low density lipoprotein, low density lipoprotein, waist and hip circumferences, and blood pressure were higher in the metabolic syndrome group than in the non-metabolic syndrome group. Free thyroxine 4, grown hormone, and insulin levels were within the normal range. The metabolic conditions of the patients with metabolic syndrome indicate biochemical, anthropometric, and hormonal changes characteristic of overweight and obesity. Conclusion: The SIRT1 polymorphism rs7895833 (A/G) is not associated with the metabolic syndrome in the adult Brazilian population.

Association of GSTM1 and GSTT1 deletion polymorphisms with Pakistani aplastic anemia patients and controls and meta-analysis

Interaction of environmental and genetic elements plays a vital role in the pathogenesis of aplastic anemia (AA). Glutathione S-transferase (GST) is a key detoxifying enzyme. Absence or low levels of this enzyme may genetically predispose individuals to AA. GST genes GSTM1 and GSTT1 are polymorphic. The aim of this study was to screen Pakistani AA patients and controls for GSTM1 deletion GSTM0 and GSTT1 deletion GSTT0 and perform meta-analysis using our data and other published data regarding these polymorphisms. DNA samples from 137 patients and 220 controls were screened using multiplex polymerase chain reaction. GSTM0 emerged as susceptible genotype for AA in Pakistan with a percentage frequency of 49.6 % as compared to 30 % in controls with odds ratio (OR) of 2.25, 95 % confidence interval (CI) of 1.4-3.5 and corrected p = 0.006. The meta-analysis showed a significant association between the null genotype GSTT0 and AA in overall analysis with OR of 1.47, 95 % CI of 1.01-2.13 and p value of 0.04 in random effects model. Studies like these could play a role in understanding the underlying path in AA pathogenesis and therefore can help in designing means for prevention, diagnose and treatment.

Glutathione-S-transferase polymorphisms (GSTM1, GSTT1 and GSTP1) and acute leukemia risk in Asians: a meta-analysis

The association between glutathione-S-transferase polymorphisms (GSTM1, GSTT1 and GSTP1) and risk of acute leukemia in Asians remains controversial. This study was therefore designed to evaluate the precise association in 23 studies identified by a search of PubMed and several other databases, up to December 2013. Using random or fixed effects models odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were calculated. Heterogeneity across studies was assessed, and funnel plots were constructed to test for publication bias. The meta-analysis showed positive associations between GST polymorphisms (GSTM1 and GSTT1 but not GSTP1) and acute leukemia risk [(OR=1.47, 95% CI 1.18-1.83); (OR=1.32, 95% CI 1.07-1.62); (OR=1.01, 95% CI 0.84-1.23), respectively] and heterogeneity between the studies. The results suggested that the GSTM1 null genotype and GSTT1null genotype, but not the GSTP1 polymorphism, might be a potential risk factors for acute leukemia. Further well-designed studies are needed to confirm our findings.

Glutathione S-transferase gene polymorphisms and susceptibility to acute myeloid leukemia: meta-analyses

OBJECTIVE

A large body of evidence has shown the possible relevance of polymorphisms of the genes that encode glutathione S-transferase μ, π and θ (GSTM1, GSTP1 and GST1, respectively) to the susceptibility of acute myeloid leukemia, but the exact association still remains uncertain. Therefore, we performed a meta-analysis to derive a more precise estimation of the relationship.

METHODS

A comprehensive literature search of PubMed and Web of Knowledge electronic databases was conducted to collect relevant studies until 20 February 2014. References of the retrieved articles were also screened. The extracted data were statistically analyzed, and pooled odds ratios with 95% confidence intervals were calculated to estimate the association strength using Review Manager version 5.2.

RESULTS

Twenty-nine studies were included in the meta-analysis. The pooled analyses revealed that the GSTM1-null genotype was associated with an increased risk of acute myeloid leukemia in East Asians (P = 0.01; odds ratio = 1.22; 95% confidence interval = 1.05-1.42), and GSTT1-null genotype in Caucasians (P < 0.0001; odds ratio = 1.48; 95% confidence interval = 1.29-1.69). There was also a predilection towards the female gender for both of these polymorphisms. For GSTP1 Ile105Val polymorphism, no significant association was found under any contrast model. In addition, the presence of the double-null genotypes increased the risk of acute myeloid leukemia in both Caucasians and East Asians.

CONCLUSIONS

This meta-analysis suggested that heritable GST status could influence the risk of developing acute myeloid leukemia.

Risk effects of GST gene polymorphisms in patients with acute myeloid leukemia: a prospective study

Glutathione S-transferase (GST) enzyme levels are associated with risk of many cancers, including hematologic tumours. We here aimed to investigate the relationships between GSTM1, GSTT1 and GSTP1 polymorphisms and the risk of AML. Genotyping of GSTs was based upon duplex polymerase-chain-reactions with the confronting- two-pair primer (PCR-CTPP) method in 163 cases and 204 controls. Individuals carrying null GSTT1 genotype had a 1.64 fold risk of acute leukemia relative to a non-null genotype (P<0.05). A heavy risk was observed in those carrying combination of null genotypes of GSTM1 and GSTT1 and GSTP1 Val allele genotypes when compared with those carrying wild genotypes, with an OR (95% CI) of 3.39 (1.26-9.26) (P<0.05). These findings indicate that genetic variants of GST and especially the GSTT1 gene have a critical function in the development of AML. Our study offers important insights into the molecular etiology of AML.

Common polymorphic deletion of glutathione S-transferase theta predisposes to acquired aplastic anemia: Independent cohort and meta-analysis of 609 patients

Acquired aplastic anemia (AA) is a rare life-threatening bone marrow failure syndrome, caused by autoimmune destruction of hematopoietic stem and progenitor cells. Epidemiologic studies suggest that environmental exposures and metabolic gene polymorphisms contribute to disease pathogenesis. Several case-control studies linked homozygous deletion of the glutathione S-transferase theta (GSTT1) gene to AA; however, the role of GSTT1 deletion remains controversial as other studies failed to confirm the association. We asked whether a more precise relationship between the GSTT1 null polymorphism and aplastic anemia could be defined using a meta-analysis of 609 aplastic anemia patients, including an independent cohort of 67 patients from our institution. We searched PubMed, Embase, and the Cochrane Database for studies evaluating the association between GSTT1 null genotype and development of AA. Seven studies, involving a total of 609 patients and 3,914 controls, fulfilled the eligibility criteria. Meta-analysis revealed a significant association of GSTT1 null genotype and AA, with an OR = 1.74 (95% CI 1.31-2.31, P < 0.0001). The effect was not driven by any one individual result, nor was there evidence of significant publication bias. The association between AA and GSTT1 deletion suggests a role of glutathione-conjugation in AA, possibly through protecting the hematopoietic compartment from endogenous metabolites or environmental exposures. We propose a model whereby protein adducts generated by reactive metabolites serve as neo-epitopes to trigger autoimmunity in aplastic anemia.

Association between glutathione S-transferase T1 null genotype and risk of myelodysplastic syndromes: a comprehensive meta-analysis

Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal hematologic neoplasms, and the pathophysiology of these disorders is still unclear. Previous studies investigating the association between glutathione S-transferase Tl (GSTT1) null genotype and risk of MDS reported controversial results. We performed a comprehensive meta-analysis to clarify the effect of GSTT1 null genotype on risk of MDS. The strength of the association was measured by odds ratio (OR) with 95 % confidence interval (CI). Fifteen studies were finally included, involving a total of 1,796 cases and 2,502 controls. Subgroup analysis was performed by race. Meta-analysis of all 15 studies showed that the GSTT1 null genotype was significantly associated with an increased risk of MDS (OR = 1.47, 95 % CI 1.16-1.88, P OR = 0.002; I (2) = 54.4 %). Besides, an obvious association was also observed after adjusting the heterogeneity (OR = 1.32, 95 % CI 1.13-1.54, P OR = 0.001; I (2) = 9.0 %). Subgroup analysis by race suggested that this association existed in both Caucasians (OR = 1.40, 95 % CI 1.04-1.89, P OR = 0.027) and Asians (OR = 1.68, 95 % CI 1.00-2.81, P OR = 0.049). This meta-analysis suggests the GSTT1 null genotype is significantly associated with an increased risk of MDS in both Caucasians and Asians.

MDR-1 and GST polymorphisms are involved in myelodysplasia progression

Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal stem cell disorders characterized by abnormal hematopoietic differentiation and maturation, which progress toward acute leukemia in approximately 30% of the cases. Drug metabolism polymorphisms in Cytochrome P450 2B6 (CYP2B6), Glutathione S-transferase (GST) and Dehydrogenase Quinone 1 (NQO1) enzymes and P-glycoprotein (MDR-1) could modify enzyme activity. Thus, the aim of this study was to identify the influence of CYP2B6 G15631T, GSTT1, GSTM1, NQO1 C609T and MDR-1 C3435T polymorphisms on MDS progression. We analyzed 78 MDS patients using the PCR-RFLP and multiplex method. The frequency of GST deletions and MDR-1 CC genotype was lower in progression-free patients compared to patients with progression; GST: 17% vs. 35% (P=0.018); MDR-1 gene: 19% vs. 48% (P=0.012). We also verified the influence of GST deletions and MDR-1 C3435T on patient overall survival and found no significant difference (RR=0.75; P=0.599 and RR=0.79; P=0.594 respectively). We concluded that GSTM1 deletion may contribute toward MDS progression probably due to toxic metabolite accumulation which generates cell toxicity and DNA damage. Moreover, MDR-1 C3435T may have a protective effect against MDS progression because the expected lower expression of P-glycoprotein would lead to a higher degree of cell death. To the best of our knowledge, this is the first study showing the relationship of these polymorphisms with MDS progression.

Mutações do gene cystic fibrosis transmembrane conductance regulator e deleções dos genes glutationa S-transferase em pacientes com fibrose cística no Brasil

OBJETIVO: Determinar os efeitos que a mutação do gene cystic fibrosis transmembrane conductance regulator (CFTR) e da deleção dos genes glutationa S-transferase (GST) mu-1 (GSTM1) e teta-1 (GSTT1) têm na evolução clínica da fibrose cística (FC) em pacientes da região sudeste do Brasil. MÉTODOS: Entre março de 2002 e março de 2005, incluímos no estudo todos os pacientes com FC atendidos consecutivamente no Departamento de Pediatria do Hospital de Clínicas da Faculdade de Ciências Médicas da Universidade Estadual de Campinas. O DNA genômico de 66 pacientes com FC foi analisado por PCR e digestão com endonuclease de restrição para a identificação dos genótipos. RESULTADOS: A mutação ΔF508 do gene CFTR foi identificada em 44 (66,7%) pacientes. As deleções dos genes GSTM1, GSTT1 e da combinação nula GSTM1/GSTT1 foram identificadas em 40,9%, 15,2% e 3,0% dos pacientes, respectivamente. A mutação ΔF508 do gene CFTR foi mais comum em pacientes diagnosticados com FC antes dos 2,5 anos de idade que naqueles diagnosticados mais tarde (75,5% vs. 41,2%; p = 0,008). CONCLUSÕES: Foram observadas frequências similares da mutação ΔF508 do gene CFTR e dos genótipos GSTM1 e GSTT1 nos pacientes, independentemente do sexo, etnia ou status da doença pulmonar ou pancreática. Quando os pacientes foram estratificados por aspectos clínicos e epidemiológicos, as frequências dos genótipos GSTM1 e GSTT1 nulos foram semelhantes, sugerindo que a ausência herdada dessas vias enzimáticas não altera o curso da FC. Em contraste, a alta frequência da mutação ΔF508 no gene CFTR encontrada em pacientes mais jovens sugere que essa mutação influencia a idade no momento do diagnóstico de FC nessa região do país.

Polymorphisms in GSTM1, CYP1A1, CYP2E1, and CYP2D6 are associated with susceptibility and chemotherapy response in non-small-cell lung cancer patients

BACKGROUND

Studies of polymorphisms in CYP1A1, CYP2E1, CYP2D6, and GSTM1 and their relationship to lung cancer susceptibility and chemotherapy response have been reported, but the results are not consistent. In this study we selected four polymorphisms in these genes, several of which have previously been researched, and investigated their association with lung cancer susceptibility and chemotherapy response.

METHODS

We genotyped the four polymorphisms in a cohort composed of 217 non-small-cell lung cancer (NSCLC) patients and 198 controls. Of these, 145 advanced NSCLC patients underwent chemotherapy and were monitored for 5 years.

RESULTS

Significant differences in the GSTM1 polymorphism were observed between the case and control groups (P = 0.02). We observed a synergistic effect of smoking and GSTM1. Smokers with deficient-type GSTM1 had a 4.96-fold increased risk of developing lung cancer. Significant differences in GSTM1 and CYP1A1 polymorphisms were observed between the response and nonresponse groups (P = 0.004 and P = 0.026). Moreover, patients with deficient-type GSTM1 were superior responders to platinum drugs than those carrying wild-type GSTM1 (P = 0.014). In addition, patients carrying TT CYP1A1 responded better to nonplatinum drugs than those carrying TC and CC CYP1A1 (P = 0.01). Polymorphisms in the four enzymes had no effect on the overall survival of NSCLC patients.

CONCLUSIONS

Our findings support the hypothesis that a polymorphism in GSTM1 is associated with lung cancer susceptibility. Furthermore, polymorphisms in GSTM1 and CYP1A1 were associated with chemotherapy response. In particular, smokers carrying deficient-type GSTM1 were at a higher risk of developing lung cancer. Patients carrying deficient-type GSTM1 responded better to platinum drugs, while those with TT CYP1A1 were better responders to nonplatinum drugs.

Variations in glutathione-S-transferase genes influence risk of chronic myeloid leukemia

Glutathione S-transferases (GSTs) are phase II enzymes that detoxify hazardous xenobiotics including carcinogens. Inter-individual variations in GSTM1 and GSTT1 loci have been associated with several types of cancer, including leukemias. In this study, we investigated the possible association between GSTM1 and GSTT1 polymorphisms and susceptibility to chronic myeloid leukemia (CML) in a Turkish population. In a case-control study, 106 CML patients and 190 healthy controls were evaluated for GSTM1 and GSTT1 polymorphisms. GSTM1 null (GSTM1(-)) genotype frequencies in CML cases and controls were 45.3% and 42.6%, respectively. GSTT1 null (GSTT1(-)) genotype frequencies were 44.3% and 18.4%, respectively. The frequency of the GSTT1(-) genotype among CML patients was significantly higher than in controls [odds ratio (OR) 3.53, 95% confidence interval (CI) 2.08-6.00; P < 0.0001]. Individuals with the GSTM1(-) genotype did not have increased risk of CML [OR: 1.11; 95% CI: 0.69-1.80; P = 0.714]. The combined GSTM1(-)/GSTT1(-) genotype was significantly associated with risk of CML compared to the GSTM1(+) /GSTT1(+) genotype which was most frequent in both cases and controls [OR: 9.47; 95% CI: 3.61-24.87]. Similar findings have only been obtained in Turkish and Indian populations but not elsewhere. The GSTM1(+) /GSTT1(-) genotype was associated with a 2.5-fold increased risk compared with the GSTM1(-)/GSTT1(+) genotype, the second most frequent genotype (OR; 2.46; 95% CI: 1.17, 5.20), suggesting a complex interaction between GSTM1 and GSTT1. Our results indicate an association between the GSTT1(-) genotype, either alone or in combination with GSTM1(-) genotype, and risk of CML, suggesting a possible interaction between GSTM1 and GSTT1. These findings, which are possibly restricted to Turkey and India, warrant further research.

CYP1A1, GSTM1 and GSTT1 polymorphisms, tobacco and alcohol status and risk of head and neck squamous cell carcinoma

We examined the influence of the CYP1A1 A4889G and T6235C, GSTM1 and GSTT1 polymorphisms, involved in carcinogen metabolism, on the head and neck (HN) squamous cell carcinoma (SCC) risk. DNA from 142 HNSCC patients and 142 controls was analysed by polymerase chain reaction (PCR)-restriction fragment length polymorphism or multiplex-PCR for the polymorphisms analyses. Excesses of the CYP1A1 4889AG+GG and 4889AG+GG plus GSTT1 null genotype were seen in patients with heavy tobacco habit compared with controls (41.9% versus 26.8%, P = 0.03; 26.2% versus 10.3%, P = 0.04, respectively). Carriers of the referred genotypes and heavy tobacco consumption were under a 2.0-fold and 2.8-fold increased risks for HNSCC than others, respectively. The CYP1A1 6235TC+CC plus GSTM1 and GSTT1 null genotypes were more common in pharyngeal SCC patients than in controls (5.3% versus 0.7%, P = 0.04). Carriers of the combined genotype had 16.0-fold increased risk for the disease than others. The frequency of one null genotype of the GSTM1 or GSTT1 gene was higher in patients with pharyngeal SCC and heavy smoking status than in controls (76.3% versus 57.7%, P = 0.04). Carriers of the referred genotype and heavy tobacco status had a 2.4-fold increased risk for pharyngeal SCC than others. In contrast, the CYP1A1 6235TC+CC genotype was more common in controls than in laryngeal SCC patients (35.9% versus 21.6%, P = 0.01). Carriers of the genotype had a 0.2-fold decreased risk for the disease than others. Our data present preliminary evidence that inherited combined CYP1A1 A4889G and T6235C abnormalities and GSTM1 and GSTT1 pathways are important determinants of HNSCC, particularly pharyngeal SCC in heavy smoking individuals from south-eastern Brazil.

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.

Glutathione S-transferase mu 1 (GSTM1) and theta 1 (GSTT1) genetic polymorphisms and atopic asthma in children from Southeastern Brazil

Xenobiotics can trigger degranulation of eosinophils and mast cells. In this process, the cells release several substances leading to bronchial hyperactivity, the main feature of atopic asthma (AA). GSTM1 and GSTT1 genes encode enzymes involved in the inactivation of these compounds. Both genes are polymorphic in humans and have a null variant genotype in which both the gene and corresponding enzyme are absent. An increased risk for disease in individuals with the null GST genotypes is therefore, but this issue is controversial. The aim of this study was to investigate the influence of the GSTM1 and GSTT1 genotypes on the occurrence of AA, as well as on its clinical manifestations. Genomic DNA from 86 patients and 258 controls was analyzed by polymerase chain reaction. The frequency of the GSTM1 null genotype in patients was higher than that found in controls (60.5% versus 40.3%, p = 0.002). In individuals with the GSTM1 null genotype the risk of manifested AA was 2.3-fold higher (95%CI: 1.4-3.7) than for others. In contrast, similar frequencies of GSTT1 null and combined GSTM1 plus GSTT1 null genotypes were seen in both groups. No differences in genotype frequencies were perceived in patients stratified by age, gender, ethnic origin, and severity of the disease. These results suggest that the inherited absence of the GSTM1 metabolic pathway may alter the risk of AA in southeastern Brazilian children, although this must be confirmed by further studies with a larger cohort of patients and age-matched controls from the distinct regions of the country.

The GSTT1 polymorphism of the glutathione S-transferase system in the intratumoral microvessel density of breast cancer patients

It is well established that hypoxic microenvironment contributes to breast cancer progression by activation of transcriptional genes that promote angiogenesis. By promoting the antioxidant activity of glutathione, glutathione S-transferases (GSTs) are likely to facilitate the hypoxia-inducible factor-1α (HIF-1α) activity, therefore stimulating the angiogenesis. We investigated herein the influence of the GSTM1 and GSTT1 polymorphisms in the intratumoral angiogenesis of 87 patients with sporadic breast cancer. The intratumoral microvessel density (IMVD) of formalin-fixed paraffin-embedded tissues samples from all patients was determined by immunohistochemistry. The high IMVD was defined as a median microvessel counting higher than 18.7 after the analysis of histogram with all the results. The high IMVD was more common in patients with the GSTT1 wild genotype than in those with the GSTT1 null genotype (P = 0.04). Our results suggest, for the first time, that the GSTT1 polymorphism constitutes an inherited determinant of intratumoral angiogenesis in sporadic breast cancer.

Cyclophosphamide-metabolizing enzyme polymorphisms and survival outcomes after adjuvant chemotherapy for node-positive breast cancer: a retrospective cohort study

INTRODUCTION

Cyclophosphamide-based adjuvant chemotherapy is a mainstay of treatment for women with node-positive breast cancer, but is not universally effective in preventing recurrence. Pharmacogenetic variability in drug metabolism is one possible mechanism of treatment failure. We hypothesize that functional single nucleotide polymorphisms (SNPs) in drug metabolizing enzymes (DMEs) that activate (CYPs) or metabolize (GSTs) cyclophosphamide account for some of the observed variability in disease outcomes.

METHODS

We performed a retrospective cohort study of 350 women enrolled in a multicenter, randomized, adjuvant breast cancer chemotherapy trial (ECOG-2190/INT-0121). Subjects in this trial received standard-dose cyclophosphamide, doxorubicin and fluorouracil (CAF), followed by either observation or high-dose cyclophosphamide and thiotepa with stem cell rescue. We used bone marrow stem cell-derived genomic DNA from archival specimens to genotype CYP2B6, CYP2C9, CYP2D6, CYP3A4, CYP3A5, GSTM1, GSTT1, and GSTP1. Cox regression models were computed to determine associations between genotypes (individually or in combination) and disease-free survival (DFS) or overall survival (OS), adjusting for confounding clinical variables.

RESULTS

In the full multivariable analysis, women with at least one CYP3A4 *1B variant allele had significantly worse DFS than those who were wild-type *1A/*1A (multivariate hazard ratio 2.79; 95% CI 1.52, 5.14). CYP2D6 genotype did not impact this association among patients with estrogen receptor (ER) -positive tumors scheduled to receive tamoxifen.

CONCLUSIONS

These data support the hypothesis that genetic variability in cyclophosphamide metabolism independently impacts outcome from adjuvant chemotherapy for breast cancer.

GSTT1 and GSTM1 polymorphisms and myelodysplastic syndrome risk: a systematic review and meta-analysis

Glutathione-S-transferace polymorphisms may make hematopoietic lineage cells susceptible to genotoxicity following exposure to heavy metals or benzene. We conducted a systematic review and meta-analysis to define the effect of GSTM1 and GSTT1 null polymorphisms on MDS risk. We searched the PubMed and SCOPUS databases to identify peer-reviewed published case-control studies investigating the association between GSTT1 and/or GSTM1 null genotypes and development of MDS. Between-study heterogeneity was assessed using Cochran's Q statistic and the I(2) statistic. Odds ratios from individual studies were pooled using fixed and random effects models. Thirteen studies were considered eligible for the GSTT1 meta-analysis (1471 cases, 1907 controls) and 10 were considered eligible for the GSTM1 meta-analysis (1161 cases, 1668 controls). For the GSTT1 polymorphism, there was moderate between study heterogeneity (p(Q) = 0.01; I(2) = 52.3%) and the null genotype was significantly associated with increased risk of MDS development, random effects OR = 1.43 (95% CI, 1.09-1.89); p = 0.01. For the GSTM1 polymorphisms there was moderate between-study heterogeneity (p = 0.07; I(2) = 43.1%) and the random effects OR = 1.02 (95% CI, 0.82-1.28) was non-significant (p = 0.85). The GSTT1 null genotype is a significant risk factor for MDS development. Gene-environment interactions need to be further explored.

No contribution of GSTM1 and GSTT1 null genotypes to the risk of neutropenia due to benzene exposure in Southeastern Brazil

Exposure to benzene has been associated with haematological diseases such as neutropenia (NEB) and acute myeloid leukaemia (AML). We tested whether the null genotypes of the GSTM1 and GSTT1 genes, involved in benzene inactivation, altered the risk for NEB in southeastern Brazil. Genomic DNA from 55 NEB patients and 330 controls was analysed by multiplex-polymerase chain reaction. The frequency of the GSTM1, GSTT1 and combined null genotypes was similar in patients and controls (GSTM1, 27.3% vs. 38.8%, p = 0.16; GSTT1, 25.5% vs. 19.7%, p = 0.24; GSTM1/GSTT1, 12.7% vs. 6.7%, p = 0.26; respectively). The distribution of genotype classes in NEB patients was similar to normal controls, suggesting that GSTM1 and GSTT1 null genotypes make no specific contribution to the risk of NEB. As the GSTM1 and GSTT1 null genotypes were previously associated with increased risk for AML in Brazil and elsewhere, we hypothesise that different thresholds of chemical exposure relative to distinct GSTM1 and GSTT1 genotypes may determine whether AML or NEB manifests in benzene exposed individuals from southeastern Brazil. Although indicative, our results still require support by prospective and large scale epidemiological studies, with rigorous assessment of daily chemical exposures and control of the possible contribution of other polymorphic genes involved in benzene metabolism.

Polymorphisms of glutathione S-transferase Mu 1, glutathione S-transferase theta 1 and glutathione S-transferase Pi 1 genes in Hodgkin's lymphoma susceptibility and progression

We tested in this study whether the polymorphisms of the glutathione S-transferase Mu1 (GSTM1), glutathione S-transferase Theta 1 (GSTT1) and glutathione S-transferase Pi 1 (GSTP1), involved in metabolism of chemical agents, cell proliferation and cell survival, alter the risk for Hodgkin lymphoma (HL). Genomic DNA from 110 consecutive patients with HL and 226 controls was analysed by polymerase chain reaction and restriction digestion for the polymorphism analyses. Similar frequencies of the GSTM1 and GSTT1 genotypes were seen in patients and controls. In contrast, the frequency of the GSTP1 wild genotype (59.1%versus 36.3%, P = 0.004) was higher in patients than in controls. Individuals with the wild genotype had a 2.68 (95%CI: 1.38-5.21)-fold increased risk for the disease than others. An excess of the GSTP1 wild genotype was also observed in patients with tumors of stages III + IV when compared with those with tumors of stages I + II (39.1%versus 20.0%, P = 0.03). These results suggest that the wild allele of the GSTP1 gene is linked to an increased risk and high aggressiveness of the HL in our cases but they should be confirmed by further studies with larger cohorts of patients and controls.

A case-only study of interactions between metabolic enzyme polymorphisms and industrial pollution in childhood acute leukemia

Cancer risk is modulated by gene-environment interactions between toxic exposure and genetic variation in carcinogen metabolism. Our objective was to assess interactions between exposure to industrial pollutants and polymorphisms affecting cytochrome P450s (CYP1A1 and CYP2E1) and glutathione S-transferases (GSTP1 and GSTT) in childhood acute leukemia (AL). A case-only design was conducted in 123 Chinese children with sporadic AL. Industrial plants in the vicinity were recorded and, if present, their size and proximity to the usual place of residence of AL children was evaluated. Unconditional logistic regression analysis was performed across the AL study group adjusting for age, gender, parental education, occupation and smoking, indoor and outdoor pesticide use, presence of television sets, refrigerators, microwave ovens and furniture material in children's rooms, and electric transformers, power lines, and telecommunication transmitters within 500 m. This analysis revealed an interaction between the GSTT null allele and industrial plants within 500 m of the residences of childhood AL patients (interaction odds ratio, COR=2.96, 95% CI: 1.09-8.01). Furthermore, the COR for the interaction between GSTT null and industrial plants within 50 m was 5.99 (95% CI: 1.41-25.45). Our results suggest an association between proximity to industrial plants and the GSTT null allele in patients with childhood AL.

Familial myelodysplasia and acute myeloid leukaemia--a review

Familial occurrence of myelodysplasia (MDS) and/or acute myeloid leukaemia (AML) is rare but can provide a useful resource for the investigation of predisposing mutations in these myeloid malignancies. To date, examination of families with MDS/AML has lead to the detection of two culprit genes, RUNX1 and CEBPA. Germline mutations in RUNX1 result in familial platelet disorder with propensity to myeloid malignancy and inherited mutations of CEBPA predispose to AML. Unfortunately, the genetic cause remains obscure in most other reported pedigrees. Further insight into the molecular mechanisms of familial MDS/AML will require awareness by clinicians of new patients with relevant family histories.

Polymorphisms in transporter and phase II metabolism genes as potential modifiers of the predisposition to and treatment outcome of de novo acute myeloid leukemia in Israeli ethnic groups

Drug metabolism/disposition and transporter genes may influence predisposition or prognosis of AML (acute myeloid leukemia) patients. We analyzed polymorphisms in 3 transporters and 4 drug metabolism genes in 293 Israeli individuals (112 AML patients and 181 controls). We analyzed: ABCC3 (MRP3) C-211T; ABCG2 (BCRP) C421A; CNT1 (SLC28A1) G565A and NAT1, NAT2, and GSTT1 and GSTM1 null alleles for influence on predisposition, as well as treatment response and survival. We found that the ABCC3 C-211T polymorphism and GSTM1 null genotype have adverse prognostic significance in AML. None of the other polymorphisms studied were found to influence either predisposition or prognosis in Israeli AML patients.

GSTM1 and codon 72 P53 polymorphism in multiple myeloma

The GSTM1 and GSTT1 genes reduce the effects of exposure to cytotoxic agents. Both genes have a null variant allele in which the entire gene is absent. On the other hand, a common polymorphism of the tumour suppressor P53 gene results in either arginine (A) or proline (P) at amino-acid position 72. The A and P alleles code proteins with distinct functions in apoptosis and DNA repair and have been associated with variable risks for several cancers. However, their roles in multiple myeloma (MM) are still unknown. We tested in study whether the GSTM1, GSTT1 and P53 genotypes altered the risk for MM in Brazilian patients. Genomic DNA from 106 patients and 230 controls were analysed by polymerase chain reaction-based methods for identification of the genotypes. Similar frequencies of the GSTM1, GSTT1 and P53 genotypes were seen in patients and controls. Individuals with the distinct genotypes had similar risks for disease. In contrast, an excess of the GSTM1 null (45.1 vs 17.2%, P = 0.009), the P53 PP+AP (70.4 vs 44.8%, P = 0.041) and the GSTM1 null plus P53 PP+AP (29.6 vs 10.3%, P = 0.004) genotypes were seen in MM patients at stage III compared with those at stages I + II. Our data suggest that the GSTM1, GSTT1 and P53 genotypes do not influence the risk for MM. However, the inherited presence of the variant codon 72 P53 allele, described here for the first time, and the absence of the GSTM1 detoxification pathway, seem to act in disease progression in our country.

Increased frequencies of glutathione-S-transferase (GSTM1 and GSTT1) null genotypes in Indian patients with chronic myeloid leukemia

Inherited differences in the capacity of xenobiotic metabolizing enzymes might be an important factor in genetic susceptibility to cancer. Null genotypes of glutathione-S-transferases (GSTs) exhibit absence of enzymatic activity and are hypothesized to be at increased risk of developing cancers. The aim of the study was to examine whether null genotypes of GSTM1 and GSTT1 confer susceptibility to chronic myeloid leukemia (CML). We carried a case control study involving 80 consecutive North Indian CML patients (58 males, 22 females; age (mean+/-S.D.) 36.2+/-10.9 years) and 105 healthy individuals (59 males, 46 females; age (mean+/-S.D.) 36.8+/-11.3 years). Multiplex PCR was carried out to determine the frequency of GSTM1 and GSTT1 null genotypes. The relationship between GSTM1, GSTT1 genotypes and risk of CML was assessed by means of odds ratio (OR) with 95% confidence limits calculated by logistic regression. A test for trend (P(trend)) in increasing the risk of CML having more than one putative high-risk allele or genotype was evaluated by means of the chi-square test. There was no difference in the frequencies of the GSTM1 null genotype and the combined GSTM1 and GSTT1 null genotypes between patients and controls in the study. However, statistical significance was found with GSTT1 null genotype frequency in CML patients as compared to controls (16/80 (20%) versus 9/105 (8.5%); OR=2.67, 95% CI: 1.03-7.01). It projects a 2.67-fold increased risk for CML in individuals with GSTT1 null genotype as compared to those possessing both alleles of the gene. Our findings suggest that heritable GST status may influence the risk of developing CML.

Role of CYP2D6, CYP1A1, CYP2E1, GSTT1, and GSTM1 genes in the susceptibility to acute leukemias

Acute leukemias (ALs) are heterogeneous diseases. Functional polymorphisms in the genes encoding detoxification enzymes cause inter-individual differences, which contribute to leukemia susceptibility. The CYP2D6, CYP1A1, CYP2E1, GSTT1, and GSTM1 polymorphisms in ALL (n = 156) and AML (n = 94) patients and 140 healthy controls were genotyped by PCR and/or PCR-RFLP using blood or bone marrow samples. No association was observed between the GSTT1 gene deletion and patients (OR = 0.8, 95% CI = 0.4-1.7 for AMLs and OR = 0.9, 95% CI = 0.5-1.6 for ALLs). Patients with ALL and AML had a higher prevalence of the GSTM1 deletions compared to controls but only the difference among adult AML patients (OR = 2.1, 95% CI = 1.0-4.2) was statistically significant. The CYP2D6*3 variant allele frequency was lower in the overall acute leukemia patients (0.6%) compared to controls (P = 0.03). CYP2D6*1/*3 genotype frequency also showed a protective association in AML patients (OR = 0.09, 95% CI = 0.01-1.7; P = 0.04). We also found a risk association for CYP2E1*5 in ALL and AML (OR = 3.6, 95% CI = 1.4-9.4 and OR = 3.9, 95% CI = 1.4-10.5, respectively). No association was found for the studied CYP2D6*4, CYP1A1*2A, and GSTT1"null" variants and the risk of acute leuke-mia (ALL or AML). This case-control study suggests a contribution of CYP2E1, CYP2D6, and GSTM1 "null" variants to the development of acute leukemias.

Increased sensitivity of Hep G2 cells toward the cytotoxicity of cisplatin by the treatment of piper betel leaf extract

Piper betel leaves (PBL) are used in Chinese folk medicine for the treatment of various disorders. PBL has the biological capabilities of de-toxication, anti-oxidation and anti-mutation. In this study we first examined the effect of PBL extract on the activity of Glutathione S-transferase (GST) isoforms, and found that it inhibited total GST and the alpha class of GST (GSTA), but not the pi class of GST (GSTP), and the mu class of GST (GSTM), activity in Hep G2 cells. RT-PCR results verified a reduction in the expression of GSTA1. Next, we examined whether PBL extract could increase the sensitivity of Hep G2 cells to anti-cancer drugs. The data showed that the cytotoxicity of cisplatin was significantly enhanced by the presence of PBL extract, accompanied by a reduction in the expression of multidrug resistance protein 2 (MRP2). These effects of PBL extract were compared to its major constitute, eugenol. Although eugenol decreased MRP2 level more effectively than PBL extract, it exhibited less sensitizing effect. In conclusion, we demonstrated that PBL extract was able to increase the sensitivity of Hep G2 cells to cisplatin via at least two mechanisms, reducing the expression of MRP2 and inhibiting the activity of total GST and the expression of GSTA. The data of this study support an application of PBL as an additive to reduce drug resistance.

Glutathione S-transferase M1 and T1 null genotype frequency in chronic myeloid leukaemia

Polymorphisms associated with genes coding for glutathione S-transferase enzymes are known to influence metabolism of different carcinogens and have been associated with incidence of various types of cancer. We have determined the GST M1 and GST T1 'null' genotype frequency in 81 patients with chronic myeloid leukaemia (CML) and 123 racially and geographically matched control individuals by multiplex polymerase chain reaction (PCR). GST M1 null genotype frequencies in CML and controls were 28.4% and 27.7%, respectively. GST T1 null genotype frequencies in CML and controls were 19.8% and 7.3%, respectively. The GST T1 null genotype frequency in CML patients is significantly different from that in controls (odds ratio (OR) 3.12, 95% confidence interval (CI) 1.3-7.45, P=0.008).

Geniposide activates GSH S-transferase by the induction of GST M1 and GST M2 subunits involving the transcription and phosphorylation of MEK-1 signaling in rat hepatocytes

Geniposide, an iridoid glycoside isolated from the fruit of Gardenia jasminoides Ellis, has biological capabilities of detoxication, antioxidation, and anticarcinogenesis. We have recently found that geniposide possesses a potential for detoxication by inducing GST activity and the expression of GST M1 and GST M2 subunits. In this study, the signaling pathway of geniposide leading to the activation of GSH S-transferase (GST) was investigated. Primary cultured rat hepatocytes were treated with geniposide in the presence or absence of mitogen-activated protein kinase (MAPK) inhibitors and examined for GST activity, expression of GST M1 and M2 subunits, and protein levels of MAPK signaling proteins. Western blotting data demonstrated that geniposide induced increased protein levels of GST M1 and GST M2 (approximately 1.76- and 1.50-fold of control, respectively). The effect of geniposide on the increased protein levels of GST M1 and GST M2 was inhibited by the MEK-1 inhibitor PD98059, but not by other MAPK inhibitors. The GST M1 and GST M2 transcripts as determined by RT-PCR and GST activity were also inhibited concurrently by the MEK-1 inhibitor PD98059. The protein levels of up- and down-stream effectors of the MEK-1, including Ras, Raf, and Erk1/2, and the phosphorylation state of Erk1/2 were found to be induced by geniposide, indicating a two-phase influence of geniposide. The results suggest that geniposide induced GST activity and the expression of GST M1 and GST M2 acting through MEK-1 pathway by activating and increasing expression of Ras/Raf/MEK-1 signaling mediators.

Glutathione s-transferase polymorphisms (GSTM1, GSTP1 and GSTT1) and the risk of acute leukaemia: a systematic review and meta-analysis

Glutathione s-transferase (GST) polymorphisms (GSTM1, GSTP1 and GSTT1) have been considered as risk factors for developing acute leukaemia in a number of studies; however the overall results of such studies are inconsistent. To investigate a putative association of GST polymorphisms with the risk of acute leukaemia, we performed a systematic review and meta-analysis of 30 published case-control studies. To take into account the possibility of heterogeneity across the studies, a statistical test was performed. The pooled odds ratios (ORs) were assessed using both a fixed-effects and a random-effects model. The pooled OR of acute leukaemia risks associated with GSTM1 null genotype, GSTP1 Val105 allele and GSTT1 null genotype were 1.22 (95% confidence interval (CI) 1.07-1.38), 1.07 (95% CI 1.00-1.13) and 1.19 (95% CI 1.00-1.41), respectively. Significantly increased risk of acute lymphoblastic leukaemia associated with GSTM1 and GSTT1 null genotypes was observed. Their pooled ORs were 1.24 (95% CI 1.17-1.31) and 1.30 (95% CI 1.06-1.60), respectively. We also found substantial evidence of heterogeneity between the studies. Our results suggest that GSTM1 and GSTT1, but not GSTP1 polymorphisms, appear to be associated with a modest increase in the risk of acute lymphoblastic leukaemia. It is conceivable that GSTM1 and GSTT1 null genotypes may thus play a role in leukemogenesis. A review of the 30 case-control studies indicates that greater attention should be paid to the design of future studies.

Genetic polymorphism of CYP1A1, CYP2D6, GSTM1 and GSTT1 and susceptibility to acute lymphoblastic leukaemia in Indian children

BACKGROUND

Biotransformation plays a crucial role in carcinogen activity and many genetic polymorphisms in xenobiotic metabolising enzymes have been associated with an increased risk of cancer. Such polymorphisms can lead to considerable variation in the activities of these enzymes, which are crucial in carcinogen and drug metabolism. These variations could play a role in the risk of developing paediatric acute lymphoblastic leukaemia (ALL) by their varying action on environmental carcinogens.

PROCEDURE

The present study looked for two polymorphisms (m1 and m2) in the CYP1A1, CYP2D6*4 genes and deletions of the glutathione S-transferases (GSTM1 and GSTT1) in 118 paediatric ALL patients and 118 age matched control children. The polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) were used to study gene polymorphisms.

RESULTS

In children with ALL, CYP1A1 m1 polymorphism was evident in 42.4% of subjects and CYP1A1 m2 in 37.3%. These were significantly different from the results obtained for control children (20.3% for CYP1A1 m1 and 19.5% for m2). Subjects with CYP1A1 m1 homozygous variant had a sixfold risk and CYP1A1 m2 a fourfold risk. In contrast, CYP2D6*4 was more prevalent in the controls than in the cases. Subjects with GSTM1 deletions had increased risk of ALL (OR = 2.1, P = 0.009). The odds ratios for both CYP1A1 m1 and m2 homozygous polymorphisms being associated with childhood ALL was 5.67 (95% CI = 2.11-15.27). The odds ratios for both GSTM1 and GSTT1 deletions being associated with ALL was 2.78 (95% CI = 0.67-11.56).

CONCLUSIONS

These results suggest that genetic polymorphisms of xenobiotic metabolising enzymes appear to influence susceptibility to childhood ALL.