Genetic polymorphisms of GSTs and their association with primary brain tumor incidence

Unveiling the etiological impact of GST-M1, GST-T1, and P53 genotypic variations on brain carcinogenesis

BACKGROUND

Functional variants of glutathione-S-transferase (GST)-M1, GST-T1, p53 might modulate brain cancer risk by altering the rate of metabolism and clearance of carcinogens from the brain tissue. In this study, the role of GST-M1, GST-T1, p53 polymorphisms on brain tumor was investigated.

METHODS AND RESULTS

Brain tumor tissues of 143 patients were obtained from the Gulhane Training and Research Hospital, Department of Neurosurgery between 2019 and 2020. In the xenobiotic mechanism, the null allele frequency in the GST-T1, GST-M1 gene regions of Phase II enzymes by qPCR method were investigated. Single nucleotide polymorphism encoding Arg/Pro conversion in the p53 gene region was analyzed in 120 cases by sequence analysis method. The data were analyzed statistically with patient's demographic and clinical data. GST-M1, GST-T1, p53 genotypes of the patient group were determined. The most frequent genotype was null genotype (0/0) for GST-M1 (χ2 = 39.756, p < 0.001). GST-M1 genotype frequencies were 30.8%, 23.1%, 44.3% for 1/1, 1/0, 0/0, respectively. The most frequent genotype was GST-T1 1/1 following by GST-T1 1/0 (χ2 = 0.335, p = 0.846). GST-T1 genotype frequencies were 64.3%, 30.8%, 4.9% for 1/1, 1/0, 0/0, respectively. GST-M1 null genotype might be associated with the development of brain tumors. Genotype distribution obtained in p53 exon 4 codon 72; Arg/Arg was determined as 31 (25.8%), Arg/Pro 70 (58.3%), and Pro/Pro 19 (15.8%) in the case group, while there were 18 (38.3%), 23 (48.9%), and 6 (12.8%) respectively in the control group. However, the genotype distribution of p53 exon 4 codon 72 among tumorous tissue did not significantly vary from healthy control tissues (χ²=2.536, p = 0.281).

CONCLUSION

The null allele frequency encountered in the GST-M1, GST-T1 gene regions is consistent with the rates in the gene pool called Caucasian in the literature. GST-M1 gene polymorphism may play a crucial role in brain carcinogenesis in Turkish patients. This study based on clinical data is thought to help to understand the important epidemiological features of brain tumors.

Antioxidant and detoxycative mechanisms in central nervous system

Since the brain contains a large amount of polyunsaturated fatty acids, consumes up to 20% of oxygen used by the whole body and exhibits low antioxidants activity, it seems to be especially vulnerable to oxidative stress. The most important antioxidant enzymes are superoxide dismutase (SOD), which catalyze the dismutation of superoxide anion to hydrogen peroxide, catalase (CAT), which converts toxic hydrogen peroxide to water and oxygen, and glutathione peroxidase (Se-GSHPx), which reduces hydrogen peroxide and organic peroxides with glutathione as the cofactor. Among other detoxifying enzymes, the most significant is glutathione transferase (GST), which shows detoksyvarious catalytic activities allowing for removal of xenobiotics, reducing organic peroxides and oxidized cell components. One of the most important brain nonenzymatic antioxidants is reduced glutathione (GSH), which (individually or in cooperation with peroxidases) participates in the reduction of free radicals, repair of oxidative damage and the regeneration of other antioxidants, such as ascorbate or tocopherol. Glutathione as a cosubstrate of glutathione transferase scavenges toxic electrophilic compounds. Although the etiology of the major neurodegenerative diseases are unknown, numerous data suggest that reactive oxygen species play an important role. Even a small change in the level of antioxidants can leads to the many disorders in the CNS.

Glutathione S-transferase genes variants and glioma risk: A case-control and meta-analysis study

Background: The glutathione S-transferase (GST) genes encode enzymes that metabolize carcinogenic compounds, and their variants, GSTP1 (Ile105Val and Ala114Val), GSTT1 (null/present), and GSTM1 (null/present), reduce enzyme activity that may affect the risk of developing cerebral glioma. This study undertook a case-control study and a meta-analysis to evaluate associations between these GST gene variants and the risk of glioma. Methods: The study enrolled 384 glioma patients (194 men and 190 women; mean age, 48.3 ± 9.2 years) and 340 healthy controls (174 men and 166 women; mean age, 46.5 ± 9.8 years). The amplification refractory mutation system assay was performed to identify GST gene variants of all 724 subjects. A meta-analysis enrolled 15 studies (including our case-control results) was performed. Results: Our case-control study found that the frequency of GSTP1 Ile105Val Val/Val genotype was significantly higher in the glioma group than that in the healthy controls (11.7% vs. 6.4%) (OR=1.50; 95% CI=1.05-2.04; P=0.01); the frequency of the Val/Ile + Ile/Ile genotypes was different from glioma patients and controls (88.3% vs. 93.6%) (OR=1.47(1.04-2.10); P=0.015); there were no associations between GSTP1 Ala114Val, GSTT1 (null/present) and GSTM1 (null/present) variants and glioma risk. Our meta-analysis confirmed that the GSTP1 Ile105Val variant was associated with an overall increased glioma risk. Moreover, our meta-analysis also confirmed the GSTP1 Ala114Val and GSTT1 null/present variants were associated with an increased glioma risk in the Caucasian population, rather than the Asian population. Conclusions: This study showed that GST gene variants were associated with an increased risk of glioma with ethnic differences. Future large-scale, multi center, controlled, prospective studies are required to support these findings and to determine how these GST gene variants may affect the pathogenesis of glioma.

Role of SOD2 Ala16Val polymorphism in primary brain tumors

The present study aimed to investigate the possible association between the genetic polymorphism of the enzyme superoxide dismutase 2 (SOD2, also known as manganese-dependent SOD), Ala16Val (rs4880), and primary brain tumor risk in the Turkish population. Frequency of the SOD2 gene rs4880 polymorphism was identified in 225 Turkish individuals (120 controls and 105 patients with primary brain tumor) by polymerase chain reaction-restriction fragment length polymorphism. Subject demographics and clinical characteristics were also recorded. The findings were evaluated using logistic regression and χ² tests. Logistic regression analysis indicated that smoking did not increase the risk for primary brain tumor [odds ratio (OR)=0.77, 95% confidence interval (CI)= 0.44-1.33, χ²=0.352, P=0.860]. Similarly, there was no statistically significant difference in the family history of cancer incidence between the control subjects and the primary brain tumor patients (OR=0.81, 95% CI=0.39-1.71, χ²=0.340, P=0.560). There was no significant association of the histopathological type, genotype/allele frequencies and inheritance models of tumor with the gene variants among the patients with primary brain tumor. In summary, the results of the present study indicated that the Ala16Val polymorphism of the SOD2 gene was not associated with primary brain tumor risk in the Turkish population studied.

Glutathione S-Transferases and Cytochrome P450 Enzyme Expression in Patients with Intracranial Tumors: Preliminary Report of 55 Patients

OBJECTIVE

Intracranial tumors are one of the most frightening and difficult-to-treat tumor types. In addition to surgery, protocols such as chemotherapy and radiotherapy also take place in the treatment. Glutathione S-transferase (GST) and cytochrome P450 (CYP) enzymes are prominent drug-metabolizing enzymes in the human body. The aim of this study is to show the expression of GSTP1, GSTM1, CYP1A1, and CYP1B1 in different types of brain tumors and compare our results with those in the literature.

SUBJECTS AND METHODS

The expression of GSTP1, GSTM1, CYP1A1, and CYP1B1 was analyzed using immunostaining in 55 patients with intracranial tumors in 2016-2017. For GST and CYP expression in normal brain tissue, samples of a portion of surrounding normal brain tissue as well as a matched far neighbor of tumor tissue were used. The demographic features of the patients were documented and the expression results compared.

RESULTS

The mean age of the patients was 46.72 years; 29 patients were female and 26 were male. Fifty-seven specimens were obtained from 55 patients. Among them, meningioma was diagnosed in 12, metastases in 12, glioblastoma in 9, and pituitary adenoma in 5. The highest GSTP1, GSTM1, and CYP-1A1 expressions were observed in pituitary adenomas. The lowest GSTP1 expression was detected in glioblastomas and the lowest CYP1B1 expression in pituitary adenomas.

CONCLUSION

GSTP1 and CYP expression is increased in intracranial tumors. These results should be confirmed with a larger series and different enzyme subtypes.

Genetic variants and increased risk of meningioma: an updated meta-analysis

PURPOSE

Various genetic variants have been reported to be linked to an increased risk of meningioma. However, no confirmed conclusion has been obtained. The purpose of the study was to investigate potential meningioma-associated gene polymorphisms, based on published evidence.

MATERIALS AND METHODS

An updated meta-analysis was performed in September 2016. After electronic database searching and study screening, we selected eligible case-control studies and extracted data for meta-analysis, using Mantel-Haenszel statistics. P-values, pooled odds ratios (ORs), and 95% confidence intervals were calculated.

RESULTS

We finally selected eight genes with ten polymorphisms: MLLT10 rs12770228, CASP8 rs1045485, XRCC1 rs1799782, rs25487, MTHFR rs1801133, rs1801131, MTRR rs1801394, MTR rs1805087, GSTM1 null/present, and GSTT1 null/present. Results of meta-analyses showed that there was increased meningioma risk in case groups under all models of MLLT10 rs12770228 (all OR >1, P<0.001), compared with control groups. Similar results were observed under the allele, homozygote, dominant, and recessive models of MTRR rs1801394 (all OR >1, P<0.05), and the heterozygote and dominant models of MTHFR rs1801131 in the Caucasian population (all OR >1, P<0.05). However, no significantly increased meningioma risks were observed for CASP8 rs1045485, XRCC1 rs25487, rs1799782, MTHFR rs1801133, MTR rs1805087, or GSTM1/GSTT1 null mutations.

CONCLUSION

Our updated meta-analysis provided statistical evidence for the role of MLLT10 rs12770228, MTRR rs1801394, and MTHFR rs1801131 in increased susceptibility to meningioma.

Genetic Contribution of Polymorphisms in Glutathione S-Transferases to Brain Tumor Risk

Existing data have shown a major effect of glutathione S-transferase (GST) single-nucleotide polymorphisms on activities of detoxification-related enzymes, and it is the functional importance that leads to extensive research on the association of GST polymorphisms with the risk of developing brain tumor. Previously reported associations, nevertheless, remain inconsistent. This study aimed to reevaluate the association with new information from recent research articles. We weekly searched multiple databases, aiming to cover all studies looking at the associations being examined in this work. Eligibility of studies was evaluated based on predesigned inclusion criteria. To assess the association of GST polymorphisms with brain tumor risk, we calculated genotypic ORs by comparing the number of genotypes between cases and controls. We also detected interstudy heterogeneity, publication bias, and single studies' influence. A total of 13 research articles were identified through databases and hand search. We found significantly elevated risk of brain tumor associated with GSTT1 null status in individuals of European ethnicity (OR 1.46, 95% CI 1.12-1.92). In the analysis of GSTP1 I105V, we observed that Val/Val genotype compared to the Ile/Ile genotype was more prone to a reduced brain tumor risk (OR 0.77, 95% CI 0.64-0.93). Such major effects were similarly seen for GSTP1 A114V (OR 1.14, 95% CI 1.01-1.29 for Val/Val + Ala/Val vs. Ala/Ala). When data were limited to glioma, we found a significant elevation associated with the combination of Val/Val and Ala/Val genotypes (OR 1.18, 95% CI 1.01-1.37). However, no clear association was detected between other polymorphisms investigated and glioma. These statistical data suggest that some of the polymorphisms at GST loci are possibly associated with the genetic risk of brain tumor.

Association between glutathione S-transferase T1 null genotype and glioma susceptibility: a meta-analysis

The relationship between genetic polymorphisms of glutathione S-transferase (GST) and the development of glioma has been investigated in several epidemiologic studies. However, these studies report inconsistent results. In order to get this precise result, a meta-analysis was conducted by calculating the pooled odds ratios (OR) and the 95% confidence intervals (95 % CI). Eleven case-control research studies with a total of 2,416 glioma cases and 4,850 controls were included into this meta-analysis. The combined results based on all studies showed that there was no significant association between the GSTT1 null allele and glioma risk (OR = 1.188, 95% CI = 0.929–1.520, P(heterogeneity) = 0.003, P = 0.170). In the subgroup analysis, the same results were found in our work. There was no risk of publication bias in this meta-analysis. Our results suggest that GSTT1 null genotype was not associated with the increased risk of glioma.

The vitamin D receptor (VDR) gene polymorphisms in Turkish brain cancer patients

Objective. It has been stated that brain cancers are an increasingly serious issue in many parts of the world. The aim of our study was to determine a possible relationship between Vitamin D receptor (VDR) gene polymorphisms and the risk of glioma and meningioma. Methods. We investigated the VDR Taq-I and VDR Fok-I gene polymorphisms in 100 brain cancer patients (including 44 meningioma cases and 56 glioma cases) and 122 age-matched healthy control subjects. This study was performed by polymerase chain reaction-based restriction fragment length polymorphism (RF LP). Results. VDR Fok-I ff genotype was significantly increased in meningioma patients (15.9%) compared with controls (2.5%), and carriers of Fok-I ff genotype had a 6.47-fold increased risk for meningioma cases. There was no significant difference between patients and controls for VDR Taq-I genotypes and alleles. Conclusions. We suggest that VDR Fok-I genotypes might affect the development of meningioma.

The Upper Midwest Health Study: gliomas and occupational exposure to chlorinated solvents

OBJECTIVES

Occupational exposure to chlorinated aliphatic solvents has been associated with an increased cancer risk, including brain cancer. However, many of these solvents remain in active, large-volume use. We evaluated glioma risk from non-farm occupational exposure (ever/never and estimated cumulative exposure) to any of the six chlorinated solvents--carbon tetrachloride, chloroform, methylene chloride, trichloroethylene, tetrachloroethylene or 1,1,1--trichloroethane-among 798 cases and 1175 population-based controls, aged 18-80 years and non-metropolitan residents of Iowa, Michigan, Minnesota and Wisconsin. Methods Solvent use was estimated based on occupation, industry and era, using a bibliographic database of published exposure levels and exposure determinants. Unconditional logistic regression was used to calculate ORs adjusted for frequency matching variables age group and sex, and age and education. Additional analyses were limited to 904 participants who donated blood specimens (excluding controls reporting a previous diagnosis of cancer) genotyped for glutathione-S-transferases GSTP1, GSTM3 and GSTT1. Individuals with functional GST genes might convert chlorinated solvents crossing the blood-brain barrier into cytotoxic metabolites.

RESULTS

Both estimated cumulative exposure (ppm-years) and ever exposure to chlorinated solvents were associated with decreased glioma risk and were statistically significant overall and for women. In analyses comparing participants with a high probability of exposure with the unexposed, no associations were statistically significant. Solvent-exposed participants with functional GST genes were not at increased risk of glioma.

CONCLUSIONS

We observed no associations of glioma risk and chlorinated solvent exposure. Large pooled studies are needed to explore the interaction of genetic pathways and environmental and occupational exposures in glioma aetiology.

Glutathione S-transferase M1, T1, and P1 polymorphisms and risk of glioma: a meta-analysis

The relationship between genetic polymorphisms of glutathione S-transferase (GST) and the development of glioma has been investigated in several epidemiologic studies. However these studies report inconsistent results. In order to quantitatively summarise the evidence for such a relationship, a meta-analysis is conducted. The PubMed database was searched from inception to January 2012 to identify relevant studies that met pre-stated inclusion criteria. We also reviewed reference lists from retrieved articles. Two researchers evaluated study eligibility and extracted the data independently, and disagreements were resolved by discussion. The principal outcome measure was the odds ratio (OR) with 95 % confidence interval (CI) for the risk of glioma associated with GSTM1, GSTT1, GSTP1 I105V or GSTP1 A114V. This meta-analysis included 11 case-control studies, which included 2,404 glioma cases and 6,379 controls. The combined results based on all studies showed that there was no association between any of the GST variants and the risk of glioma (for GSTM1: pooled OR = 1.03; 95 % CI, 0.92-1.15; for GSTT1: pooled OR = 1.12; 95 % CI, 0.90-1.40; for GSTP1 I105V: pooled OR = 0.92; 95 % CI, 0.64-1.31 and for GSTP1 A114V: pooled OR = 1.14; 95 % CI, 0.97-1.34). Subgroup analyses showed that GSTP1 A114V genotype was associated with an increased risk of other histopathologic glioma except glioblastoma multiforme (GBM) (pooled OR = 1.30; 95 % CI = 1.06-1.60); no relationship was found between other GST variants and histopathologic groups. In conclusion, our meta-analysis suggests no association between GST variants and the risk of glioma. However, the significant risk elevation is present between GSTP1 A114V genotype and other histopathologic glioma except GBM.

Lack of association between GSTM1 and GSTT1 polymorphisms and brain tumour risk

OBJECTIVE

Glutathione S-transferases (GSTs) are important enzymes that are involved in detoxification of environmental carcinogens. Molecular epidemiological studies have been conducted to investigate the association between GSTM1 and GSTT1 homozygous deletion polymorphisms and brain tumours but results have been conflicting. The aim of this study was to clarify this problem using a meta-analysis.

METHODS

A total of 9 records were identified by searching the PubMed and Embase databases. Fixed- and random-effects models were performed to estimate the pooled odds ratios.

RESULTS

No significant association was found between the GSTM1 and GSTT1 homozygous deletion polymorphisms and risk of brain tumours, including glioma and meningioma. Similar negative results were also observed in both population-based and hospital-based studies.

CONCLUSION

These findings indicate that the GSTM1 and GSTT1 polymorphisms may not be related to the development of brain tumours.

Selected polymorphisms of GSTP1 and TERT were associated with glioma risk in Han Chinese

BACKGROUND

Current evidence suggests that a majority of the inherited risks play a major role in glioma susceptibility, and glioma is due to the co-inheritance of multiple low-risk variants. These variants can be identified through association studies including such as genome-wide association studies (GWAS), which has led the glioma epidemiology researchers to focus on identifying potential disease-causing factors.

METHODS

We evaluated and validated 10 tag single nucleotide polymorphisms (tSNPs) in seven genes associated with glioma susceptibility in a Han Chinese population, including 301 glioma cases and 302 controls, using a multiplexed single nucleotide polymorphism (SNP) MassEXTEND assay. We ascertained the genotypic frequencies for each tSNP in control subjects were within Hardy-Weinberg equilibrium (HWE) using an exact test, and then compared the genotype and allele frequencies of glioma patients and control subjects using the χ2 test. We then applied three genetic models (dominant, recessive, and additive) using PLINK software to assess the association of each tSNP with glioma risk.

RESULTS

We identified two tSNPs to be associated with glioma susceptibility (rs1695, GSTP1, P = 0.019; rs2853676, TERT, P = 0.039), which we confirmed using dominant and additive model analyses. The genotype &ldquo;GA&rdquo; for rs1695 was recognized to be a protective genotype for glioma (OR, 0.67; 95% CI, 0.47-0.96; P = 0.027), while the genotype &ldquo;AG&rdquo; for rs2853676 was shown to be a risk genotype for glioma (OR, 1.50; 95% CI, 1.05-2.15; P = 0.025).

CONCLUSION

Our results, and those from previous studies, suggest potential genetic contributes for GSTP1 and TERT in glioma development.

Evaluation of glutathione S-transferase P1 polymorphisms (Ile105Val and Ala114Val) in patients with small cell lung cancer

AIMS

Glutathione S-transferase P1 (GSTP1) plays an important role in cellular protection against oxidative stress and toxic chemicals. Polymorphisms within GSTP1 are associated with alterations in enzyme activity, which may lead to development of lung disease and cancer. In this study, we aimed to investigate the GSTP1 Ile105Val and Ala114Val polymorphisms in patients with small cell lung cancer (SCLC).

PATIENTS/METHODS

GSTP1 Ile105Val polymorphism in exon 5 and GSTP1 Ala114Val polymorphism in exon 6 were determined by using polymerase chain reaction-restriction fragment length polymorphism techniques in 89 patients with SCLC and 108 control patients with chronic obstructive pulmonary disease (COPD). Genotype frequencies and cigarette smoking intensities were compared among SCLC and COPD patients.

RESULTS

There were significantly less SCLC patients with variant exon 6 genotypes than COPD patients (7.9% vs. 20.4%, p=0.007), while the number of patients with variant exon 5 genotypes were comparable among groups. SCLC and COPD patients with variant exon 6 genotype showed trends toward exhibiting reduced cigarette consumption.

CONCLUSIONS

The variant GSTP1 exon 6 genotype might be conferring protection against SCLC development. Whether this effect is associated with exposure to cigarette smoking needs to be clarified.

Genetic polymorphisms of glutathione S-transferases are associated with ulcerative colitis in central China

The present study aimed to investigate the association between genetic polymorphisms of glutathione S-transferases (GSTs) and susceptibility to ulcerative colitis (UC) in central China. The prevalence of GSTM1, GSTT1, and GSTP1 gene polymorphisms were examined using polymerase chain reaction methods in 270 consecutive UC patients and 623 age- and sex-matched healthy controls. The frequencies of the GSTM1(null) and GSTT1(null) as well as GSTP1 (Val/Val) genotypes were significantly higher in UC patients than in the controls (70.74% vs. 41.74%, P = 0.0001; 64.82% vs. 47.19%, P = 0.0001; and 48.89% vs. 34.35%, P = 0.0004, respectively). When the UC patients were stratified according to clinical features, we found that the frequencies of the GSTT1(null) and GSTP1 (Val/Val) genotypes but not the GSTM1(null) genotype were significantly higher in patients with distal colitis than in extensive colitis (P = 0.0007, P = 0.001, and P = 0.271, respectively). However, these variant GST genotypes were not significantly linked to severity of the disease (P > 0.05). GST variant genotypes are strongly correlated with prevalence and extent but not with severity of UC in the Hubei Han population in central China.

Are GSTM1, GSTT1 and CAG repeat length of androgen receptor gene polymorphisms associated with risk of prostate cancer in Iranian patients?

We conducted this study to investigate whether CAG repeat length in androgen receptor gene and GSTM1 and GSTT1 polymorphisms influence prostate cancer risk in Iranian newly diagnosed cancer patients compared to age-matched BPH group and healthy individuals. DNA from 110 pathologically-confirmed prostate cancer patients, 99 age-matched men with Benign Prostatic Hyperplasia (BPH) and 100 healthy individuals were extracted and amplified by polymerase chain reaction (PCR). PCR products were examined by electrophoresis and sequencing. The mean number of CAG repeat in prostate cancer patients was significantly smaller than normal (19.9 vs 22.8; p < 0.0001) and BPH groups (19.9 vs 21.9; P < 0.0001) The mean difference between normal individuals and BPH group was also significant (21.9 vs. 22.8; P = 0.003). Presence of GSTM1 null genotype were significantly higher in cancer and BPH group vs. normal individuals (both P values < 0.0001). there was not seen association between GSTT1 null or positive genotype with cancer risk, but analysis of GSTM1 null and GSTT1 positive in combination was statistically associated with Prostate cancer risk (OR = 8.4, 95% CI 1.53-46.73). Our results showed that CAG repeat polymorphism in AR gene may act as a risk modifier and GSTM1 null genotypes also may be contributed to prostate cancer susceptibility in Iranian patients.

Relationship between genetic polymorphisms of glutathione S-transferase genes and susceptibility to ulcerative colitis in Zhejiang Han population

AIM: To investigate the association between the genetic polymorphisms of glutathione S-transferases (GSTs) genes and susceptibility to ulcerative colitis (UC) in Zhejiang Han population.

METHODS: A total of 252 patients with UC were collected from the Second Affiliated Hospital of Wenzhou Medical College and other large general hospitals in Wenzhou City. The control group was composed of 578 healthy volunteers. PCR was used to examine the prevalence of GST (M1, T1, P1) gene polymorphisms in these subjects.

RESULTS: The frequencies of GSTM1 (-), GSTT1 (-) and GSTP1 (VaL/VaL) were significantly higher in UC patients than in controls (69.45% vs 46.30%, P = 0.0003; 61.51% vs 51.39%, P = 0.007; 48.81% vs 34.61%, P < 0.0001). A further observation was made on the UC patients according to the clinical features. The frequencies of GSTT1 (-) and GSTP1 (VaL/VaL) genotypes were higher in patients with distal colitis than in those with extensive colitis (P = 0.0001 and 0.001). However, the same result was not observed for GSTM1 (-) genotype (P = 0.108). In addition, the variant genotypes of GST (M1, T1, P1) were not significantly linked to the severity of the disease (all P > 0.05).

CONCLUSION: The GST (M1, T1, P1) variant genotypes are obviously correlated with the development of UC in Zhejiang Han population.

Lack of association between glutathione S-transferase polymorphisms and primary glioma in a case-control study in Rio de Janeiro

The glutathione S-transferases (GSTs), a family of phase II isozymes, detoxify several carcinogens. Genetic variations in GSTs have been associated with increased risk for cancer due to a heritable deficiency in detoxification pathways for environmental carcinogens. Conflicting findings have been reported about the association between constitutive GST polymorphisms and gliomas in different populations. The present case-control study examined 78 patients with primary glioma and 347 controls from Rio de Janeiro. DNA was isolated from whole blood, and four genetic polymorphisms (GSTM1, GSTM3, GSTT1, and GSTP1) were determined by PCR-RFLP. The distributions of the genotypic frequencies of these polymorphisms did not differ significantly between cases and controls and were as expected by Hardy-Weinberg equilibrium (P > 0.05). Risk analysis did not show an association between GSTs and primary glioma, suggesting that these polymorphisms do not influence the risk of primary glioma, at least in this population in Rio de Janeiro, Brazil.

The Association Between Polymorphisms in Glutathione S-Transferase (GSTM1andGSTT1) and Lung Cancer Outcome

BACKGROUND

Polymorphisms in the glutathione S-transferase (GST) family may be associated with increased risk of lung cancer, somatic changes in lung tumour tissue, and survival. We evaluated survival according to GST polymorphism in lung cancer patients.

METHODS

We studied DNA polymorphisms of 81 primary lung cancer patients at 2 glutathione-related loci: GSTM1, and GSTT1 that encode glutathione S-transferase-mu, and glutathione S-transferase- square. The presences of the GSTM1 and GSTT1 genes were assayed by PCR. Kaplan-Meier with log rank tests, and Cox regression models were applied in the analysis.

RESULTS

The median age of 75 males and 6 females was 60 years. Median survival of the whole population was 8 months. In the first presentation, none of the patients with GSTT1 null genotype but 30 percent of the patients with GSTT1-positive genotype had liver metastasis (p < 0.01) but GSTT1 genotype was not associated with survival. Sputum (p < 0.01) was more common in patients with GSTM1 null genotype. Subjects with the GSTM1-null genotype had shorter survival. Using a Cox proportional hazard model, GSTM1, tumor (T) factor and thoracic irradiation status were identified as independent prognostic factors.

CONCLUSIONS

Our preliminary results showed that GSTM1-null genotype was associated with shorter survival.

Genetic Polymorphism in Glutathione Transferases (GST): Population distribution of GSTM1, T1, and P1 conjugating activity

Glutathione transferases (GST) catalyze the conjugation of glutathione (GSH) with electrophiles, many of which may otherwise interact with protein or DNA. In select cases such as halogenated solvents, GST-mediated conjugation may lead to a more toxic or mutagenic metabolite. Polymorphisms that exert substantial effects on GST function were noted in human populations for several isozymes. This analysis focuses on three well-characterized isozymes, GSTM1, T1, and P1, in which polymorphisms were extensively studied with respect to DNA adducts and cancer in molecular epidemiologic studies. The current review and analysis focused upon how polymorphisms in these GST contributed to population variability in GST function. The first step in developing this review was to characterize the influence of genotype on phenotype (enzyme function) and the frequency of the polymorphisms across major population groups for all three GST. This information was then incorporated into Monte Carlo simulations to develop population distributions of enzyme function. These simulations were run separately for GSTM1, T1, and P1, and also for the combination of these isozymes, to assess the possibility of overlapping substrate specificity. Monte Carlo simulations indicated large interindividual variability for GSTM1 and T1 due to the presence of the null (zero activity) genotype, which is common in all populations studied. Even for GSTM1 or T1 non-null individuals, there was considerable interindividual variability with a bimodal distribution of enzyme activity evident. GSTP1 polymorphisms are associated with somewhat less variability due to the absence of null genotypes. However, in all cases simulated, the estimated variability is sufficiently large to warrant consideration of GST function distributions in assessments involving GST-mediated activation or detoxification of xenobiotics. Ideally, such assessments would involve physiologically based toxicokinetic (PBTK) modeling to assess population variability in internal dose.

Meningiomas: causes and risk factors

Meningiomas are among the most common primary intracranial tumors. Although the vast majority of these tumors are considered histologically benign, the incidence of complications can be high. Few studies have investigated the causes and risk factors for meningioma; this review highlights the current state of knowledge. Gaining a better understanding of the origin of this disease is essential so that treatments and outcomes can be improved and prevention strategies can be developed.

Genetic polymorphism of glutathione S-transferase T1: a candidate genetic modifier of individual susceptibility to schizophrenia

Schizophrenia is highly heritable, but the specific genes involved remain to be determined. A genome wide scan approach has indicated that human chromosome 22q11.2 potentially influences schizophrenia susceptibility. The gene encoding glutathione S-transferase T1 (GSTT1), which pertains to phase II biotransformation enzymes, was also mapped to the above-mentioned band. The present case-control study was performed on 292 (206 males, 86 females) in-patients with schizophrenia, and a total of 292 healthy blood donors matched to the patients according to age (+/-5 years) and gender as a control group. The patients were chronic cases. The patients were diagnosed as chronic schizophrenia according to structured clinical interview using the Structured Clinical Interview for DSM-IV (clinician version) to confirm and document DSM-IV diagnosis. The GSTT1 genotypes were determined using a PCR-based method. The GSTT1 null genotype was 17.8% and 33.9% in the patients and control groups, respectively. The GSTT1 null genotype was associated with a significantly reduced risk of developing schizophrenia. On the other word, the positive GSTT1 genotype significantly increased the risk of schizophrenia. The present finding indicated that GSTT1 is a candidate gene for susceptibility to schizophrenia.

An international case-control study of glutathione transferase and functionally related polymorphisms and risk of primary adult brain tumors

BACKGROUND

Glutathione transferases (GST) detoxify environmental and endogenous compounds and levels of two polymorphic GST proteins, GSTM3 and GSTP1, are high in the brain. Previous studies of GSTM3 and GSTP1 polymorphisms and adult brain tumor risk have produced inconsistent results, whereas the GSTM3 -63 variant is newly identified and, therefore, has not yet been studied in this context. We therefore examined associations between GSTM3 -63, GSTM3 *A/*B, GSTP1 105, and GSTP1 114 variants and adult brain tumor risk and the interaction of the effects of these same polymorphisms with cigarette smoking. In addition, the enzymes NQO1 and CYP1A1 alter susceptibility to oxidative brain damage. Because there is less previous evidence for a role of NQO1, CYP1A1, GSTM1, and GSTT1 variants, we restricted analysis of these variants to a small preliminary study.

METHODS

We genotyped DNA collected for an international population-based case-control study of 725 glioma cases, 329 of which were glioblastoma cases, 546 meningioma cases and 1,612 controls. Study participants were residents of Sweden, southeast England, Denmark, and Finland.

RESULTS

We found no associations between the GSTM3, GSTP1, NQO1, CYP1A1, GSTM1, or GSTT1 polymorphisms and adult brain tumor risk with the possible exception of a weak association between the G-C (Val-Ala) GSTP1 105/114 haplotype and glioma [odds ratio (OR), 0.73; 95% confidence interval (95% CI), 0.54, 0.99], nor was there an interaction between the effects of the GSTM3 or GSTP1 polymorphisms and cigarette smoking.

CONCLUSIONS

Overall, we observed no strong evidence for an association between GST or related enzyme polymorphisms and adult brain tumor risk.

Cisplatin-induced long-term hearing impairment is associated with specific glutathione s-transferase genotypes in testicular cancer survivors

PURPOSE

Cisplatin, a cornerstone of combination chemotherapy in the treatment of testicular cancer, induces hearing impairment with considerable interindividual variations. These differences might be a result of functional polymorphisms in cisplatin-detoxifying enzymes like glutathione S-transferases (GSTs).

PATIENTS AND METHODS

We identified 173 cisplatin-treated testicular cancer survivors (TCSs) who had participated in a long-term survey that included audiometric testing and lymphocyte sampling. The hearing decibel thresholds at 4,000 Hz were categorized into leveled scales by normative decibel percentiles. Known functional polymorphisms (positive or negative) in GSTT1 and GSTM1 and codon 105 A/G (Ile/Val) in GSTP1 were analyzed by multiplex polymerase chain reaction, followed by restriction enzyme cutting, and separated by gel electrophoresis.

RESULTS

The risk of having an inferior audiometric result was more than four times higher in TCSs with 105Ile/105Ile-GSTP1 or 105Val/105Ile-GSTP1 compared with 105Val/105Val-GSTP1 (odds ratio [OR] = 4.21; 95% CI, 1.99 to 8.88; P < .001 when modeled by ordinal logistic regression [OLR]). GSTM1 positivity was detrimental for hearing ability. Two combined genotypes were associated with hearing ability. The presence of pattern 1 (GSTT1 positive, GSTM1 positive, and 105Ile/105Ile-GSTP1) was associated with hearing impairment (OR = 2.76; 95% CI, 1.35 to 5.64; P = .005, OLR). TCSs with pattern 2 (GSTT1 positive, GSTM1 positive, and 105Val/105Val-GSTP1) had better hearing ability than TCSs without this pattern (OR = 5.35; 95% CI, 2.25 to 12.76; P < .001, OLR).

CONCLUSION

The presence of both alleles of 105Val-GSTP1 offered protection against cisplatin-induced hearing impairment. Two genotype patterns with good and poor protection against cisplatin-induced ototoxicity were identified.

Polymorphisms of CYP1A1, GSTM1, GSTT1, and prostate cancer risk in Turkish population

Prostate cancer is the most common cancer among men in many countries. Although the etiology of prostate cancer largely is unknown, both genetic and environmental factors may be involved. Advanced age, androgen metabolism, and heredity-race have been reported to be possible risk factors. On the other hand, several studies indicate that genetic polymorphisms in biotransformation enzymes play a role in prostate cancer development. In this study, association of the prostate cancer risk with genotype frequencies of the Phase I (CYP1A1) and Phase II (GSTM1 and GSTT1) biotransformation enzymes was investigated in 321 Turkish individuals (152 prostate cancer patients and 169 age-matched male controls). The presence or absences of the GSTM1 and GSTT1 genes were determined by a PCR-based method. Genotypes of CYP1A1 were determined by MspI-RFLP. The prevalence of GSTM1 null genotype in the cases was 64 percent, compared to 31 percent in the control group, indicating a strong association (OR = 4.08, 95%CI = 2.50-6.69). No association was observed between either GSTT1 null genotype or CYP1A1 polymorphism and prostate cancer incidence. No statistically significant association was observed between smoking status of the patients and any of the polymorphisms studied. In conclusion, results of this study indicate that only the GSTM1 null genotype may play an important role as a risk factor for prostate cancer development in Turkish population.

The molecular epidemiology of gliomas in adults

In this paper the authors highlight recent findings from molecular epidemiology studies of glioma origin and prognosis and suggest promising paths for future research. The reasons for variation in glioma incidence according to time period of diagnosis, sex, age, ancestry and ethnicity, and geography are poorly understood, as are factors that affect prognosis. High-dose therapeutic ionizing irradiation and rare mutations in highly penetrant genes associated with certain rare syndromes—the only two established causes of glioma—can be called upon to explain few cases. Both familial aggregation of gliomas and the inverse association of allergies and immune-related conditions with gliomas have been shown consistently, but the explanations for these associations are inadequately developed or unknown. Several bio-markers do predict prognosis, but only evaluation of loss of 1p and 19q in oligodendroglial tumors are incorporated in clinical practice. Ongoing research focuses on classifying homogeneous groups of tumors on the basis of molecular markers and identifying inherited polymorphisms that may influence survival or risk. Because most cases of glioma have yet to furnish either an environmental or a genetic explanation, the greatest potential for discovery may lie in genomic studies in conjunction with continued evaluation of environmental and developmental factors. Large sample sizes and multidisciplinary teams with expertise in neuropathology, genetics, epidemiology, functional genomics, bioinformatics, biostatistics, immunology, and neurooncology are required for these studies to permit exploration of potentially relevant pathways and modifying effects of other genes or exposures, and to avoid false-positive findings. Improving survival rates for patients harboring astrocytic tumors will probably require many randomized clinical trials of novel treatment strategies.

Genetic polymorphisms of glutathione S-transferases and the risk of adult brain tumors: a meta-analysis

BACKGROUND

Studies investigating the association between genetic polymorphisms of glutathione S-transferases (GST) and risk of adult brain tumors have reported conflicting results. The rationale of this meta-analysis was to determine whether GST variants increase the susceptibility of adult brain tumors by pooling data.

METHODS

Two investigators independently searched the HuGENet database, MEDLINE, EMBASE, conference articles, and manually reviewed bibliographies of retrieved articles. Papers were included if they were observational studies investigating the influence of GSTM1, GSTT1, GSTP1 I105V, or GSTP1 A114V on the development of adult brain cancers. Potential sources of heterogeneity between studies were explored in a meta-regression.

RESULTS

We identified eight eligible studies, which included 1,630 cases of glioma, 245 cases of meningioma, and 7,151 controls. Using the random effects model, there was no association between any of the GST variants and the risk of glioma [overall odds ratio (OR), 1.08; 95% confidence interval (95% CI), 0.95-1.22]. Subgroup analyses also showed no relationship between GST variants and histopathologic groups; the overall ORs were 1.13 (95% CI, 0.88-1.43) for high-grade glioma and 1.08 (95% CI, 0.76-1.55) for low-grade glioma. A random effects meta-regression suggested that the use of in-hospital controls produced larger effect estimates in glioma than the use of population controls (overall OR, 1.30; 95% CI, 1.03-1.65). The T1 null genotype was significantly associated with a risk of meningioma (OR, 1.95; 95% CI, 1.02-3.76), but the M1 variant was not.

CONCLUSION

This study did not suggest any relationship between GST variants and risks of glioma; the T1 null genotype may influence the susceptibility of meningioma, but larger studies are needed to substantiate this relationship.