GSTM1, GSTT1, and GSTP1 polymorphisms and colorectal cancer risk in Polish nonsmokers

Association of genetic polymorphism of glutathione S-transferases with colorectal cancer susceptibility in snuff (Naswar) addicts

Abstract The current study aimed to investigate the relationship between polymorphisms in detoxifying (GSTM1, GSTT1, and GSTP1) genes and their association with colorectal cancer (CRC) in tobacco addicts of Pashtun ethnicity. Polymorphisms in the selected genes were genotyped in a case-control study consisting of 100 histologically confirmed male CRC patients and 100 birth-year and gender-matched healthy controls using the PCR−RFLP method. The GSTM1 null, and GSTT1 null genotypes were significantly contributed to the risk of CRC in the cases (OR= 3.131, 95% CI: 1.451−6.758, P = 0.004, and OR= 3.541, 95% CI: 1.716−7.306, P = 0.001, respectively), whereas the association observed for GSTP1 Val/Val (1.139, 95% CI: 0.356−3.644, P = 0.826) did not show statistical significance. The combined GSTM1 null and GSTT1 null showed a 41-fold increased risk (95% CI: 4.945−351.950, P = 0.001), while, the combined GSTM1 null and GSTP1 Ile/Val or Val/Val variant genotypes exhibited about 3-fold (95% CI: 1.196−7.414, P = 0.019) increased risk to CRC. Similarly, the combined GSTT1 null and GSTP1 Ile/Val or Val/Val variant genotypes showed about a 3-fold (95% CI: 1.285−8.101, P = 0.013) increased risk of CRC. In the combination of three GST genotypes, the GSTM1 null, GSTT1 null, and GSTP1 Ile/Val or Val/Val variant genotypes demonstrated a more than a 22-fold (95% CI: 2.441−212.106, P = 0.006) increased risk of CRC. Our findings suggest that GSTM1 and GSTT1 polymorphism and its combination with GSTP1 may be associated with CRC susceptibility in the Naswar addicted Pashtun population of Khyber Pakhtunkhwa, Pakistan.

The importance of polymorphisms in the genes encoding glutathione S-transferase isoenzymes in development of selected cancers and cardiovascular diseases

Glutathione S-transferases are a family of enzymes, whose main role is to detoxify cells from many exogenous factors, such as xenobiotics or carcinogens. It has also been proven that changes in the genes encoding these enzymes may affect the incidence of selected cancers and cardiovascular diseases. The aim of this study was to review the most important reports related to the role of glutathione S-transferases in the pathophysiology of two of the most common diseases in modern society - cancers and cardiovascular diseases. It was shown that polymorphisms in the genes encoding glutathione S-transferases are associated with the development of these diseases. However, depending on the ethnic group, the researchers obtained divergent results related to this field. In the case of the GSTP1 A/G gene polymorphism was shown an increased incidence of breast cancer in Asian women, while this relationship in European and African women was not found. Similarly. In the case of cardiovascular diseases, the differences in the influence of GSTM1, GSTT1, GSTP1 and GSTA1 polymorphisms on their development or lack of it depending on the continent were shown. These examples show that the development of the above-mentioned diseases is not only influenced by genetic changes, but their pathophysiology is more complex. The mere presence of a specific genotype within a studied polymorphism may not predispose to cancer, but in combination with environmental factors, which often depend on the place of residence, it may elevate the chance of developing the selected disease.

GSTs genetic polymorphism, gene-environment interaction and association with gallbladder cancer risk in North Indian population: A case-controlled study

AIM

In the present case-controlled study, we explored the role of genetic polymorphism in three xenobiotic metabolizing genes, GSTM1, GSTT1 and GSTP1, and their association to gallbladder cancer (GBC) risk in a North Indian population. Its etiology is influenced by genetic, food habits, lifestyle, and environmental factors. GBC incidence is significantly higher in the Gangetic belt, India. Therefore, we explored the prognostic factors in the susceptibility of GBC through gene-gene and gene-environment interaction in this region.

MATERIAL AND METHODS

Genetic polymorphism was analyzed in 108 GBC patients from Kamala Nehru Memorial Cancer Hospital, Prayagraj and 142 matched controls. GSTM1 and GSTT1 genotypes were analyzed by multiplex PCR method, while restriction fragment length polymorphism (RFLP) was performed to analyze GSTP1 genotypes. Logistic regression analysis calculating the odds ratio (OR) and 95% confidence interval (CI) was performed to analyze the GBC risk.

RESULTS

GSTT1 (null) genotype was at a significantly higher risk and susceptible to GBC (OR = 2.044, CI = 1.225-3.411, P = 0.006), while GSTM1 and GSTP1 genotypes did not show any association to GBC risk. After sex stratification, females diagnosed with GBC had higher GSTT1 (null) genotype (OR = 2.754, CI = 1.428-5.310, P = 0.003) compared to males. GBC patients dwelling in rural areas show higher GSTT1 (null) genotype with two-fold GBC risk (OR = 2.031, CI = 1.200-3.439, P = 0.008). Further, GBC patients with histopathology of adenocarcinoma also showed higher GSTT1 (null) genotype (OR = 2.113, CI = 1.248-3.578, P = 0.005). Gene-gene interaction between GSTT1 (non-null)/GSTP1 (Ile/Val + Val/Val), enhance the GBC risk (OR = 1.840, CI = 1.135-2.982, P = 0.013).

CONCLUSIONS

The present study suggests that GSTT1 (null) genotype has higher susceptibility and risk towards GBC in North Indian population. Female patients, patients with histopathology of adenocarcinoma and rural dwelling GBC patients have higher GSTT1 (null) genotypes and may be at risk of developing GBC. The genotype combination GSTT1 (non-null)/GSTP1 (Ile/Val + Val/Val) has increased GBC susceptibility and may be considered as 'at risk' genotypes for GBC in North Indians.

Association between Glutathione S-Transferases Gene Variants and COVID-19 Severity in Previously Vaccinated and Unvaccinated Polish Patients with Confirmed SARS-CoV-2 Infection

As the outcome of COVID-19 is associated with oxidative stress, it is highly probable that polymorphisms of genes related to oxidative stress were associated with susceptibility and severity of COVID-19. The aim of the study was to assess the association of glutathione S-transferases (GSTs) gene polymorphisms with COVID-19 severity in previously vaccinated and unvaccinated Polish patients with confirmed SARS-CoV-2 infection. A total of 92 not vaccinated and 84 vaccinated patients hospitalized due to COVID-19 were included. The WHO COVID-19 Clinical Progression Scale was used to assess COVID-19 severity. GSTs genetic polymorphisms were assessed by appropriate PCR methods. Univariable and multivariable analyses were performed, including logistic regression analysis. GSTP1 Ile/Val genotype was found to be associated with a higher risk of developing a severe form of the disease in the population of vaccinated patients with COVID-19 (OR: 2.75; p = 0.0398). No significant association was observed for any of the assessed GST genotypes with COVID-19 disease severity in unvaccinated patients with COVID-19. In this group of patients, BMI > 25 and serum glucose level > 99 mg% statistically significantly increased the odds towards more severe COVID-19. Our results may contribute to further understanding of risk factors of severe COVID-19 and selecting patients in need of strategies focusing on oxidative stress.

Glutathione S-Transferase P1 Genetic Variant's Influence on the HbA1c Level in Type Two Diabetic Patients

GST (glutathione S-transferases) are capable of influencing glucose homeostasis, probably through regulation of the response to oxidant stress. The aim of our study was to investigate the relationship between GSTP1 gene polymorphism and glycated hemoglobin (HbA1c) levels in type two diabetic (T2D) patients. A total of 307 T2D patients were included. Analysis of the GSTP1 gene polymorphism (rs1695) was conducted using the TaqMan qPCR method endpoint genotyping. HbA1c was determined using a COBAS 6000 autoanalyzer. A univariable linear regression and multivariable linear regression model were used to investigate the association between mean HbA1c level and GSTP1 gene polymorphism, age at T2D diagnosis, T2D duration, therapy with insulin, gender, BMI, smoking status. GSTP1 Val/Val genotype, age at T2D diagnosis, T2D duration and therapy with insulin were statistically significant contributors to HbA1c levels (p < 0.05). Multivariable regression analysis revealed that GSTP1 (Val/Val vs. Ile/Ile) was associated with higher HbA1c even after adjustment for variables that showed a statistically significant relationship with HbA1c in univariable analyses (p = 0.024). The results suggest that GSTP polymorphism may be one of the risk factors for higher HbA1c in T2D patients. Our study is limited by the relatively small sample size, cross-sectional design, and lack of inclusion of other oxidative stress-related genetic variants.

Comparative frequency distribution of glutathione S-transferase mu (GSTM1) and theta (GSTT1) allelic forms in Himachal Pradesh population

Background

Glutathione S-transferases (GSTs) are a class of important Phase II detoxification enzymes that catalyze the conjugation of glutathione and xenobiotic compounds (environmental carcinogens, pollutants and drugs) to protect against oxidative stress. GSTT1 and GSTM1 genetic polymorphisms have been extensively studied, and null genotypes or homozygous deletions have been reported in various populations. Previous studies have suggested that those who are homozygous null at the GSTM1 or GSTT1 loci are more susceptible and have a higher risk of cancers linked to environmental pollutants and drug-induced toxicity. Our study focused on GSTM1 and GSTT1 null allele frequency in the Doon population of Himachal Pradesh (India) with a comparison across other Inter and Intra-Indian ethnic groups to predict variation in the possible susceptible status.

Material and methods

Genomic DNA samples were extracted from 297 healthy unrelated individuals by a ReliaPrep™ Blood gDNA Miniprep kit (Promega, USA), and genotyped for allelic variation in GSTM1 and GSTT1 genotypes by multiplex polymerase chain reaction. Fisher's exact test was applied using SPSS.20 to analyze the genotypic distribution of GSTM1 and GSTT1 null alleles in male and female of Doon region (Solan) Himachal Pradesh.

Results

In our study, the frequency distribution of the homozygous null genotypes of GSTM1, GSTT1 individually as well as combined was found as 33.3%, 32% and 9%, respectively. Upon gender-wise comparison, a non-significant distribution (p > 0.05) for null genotypes of GSTM1 (32.8% and 35.4%, OR-0.77, 95% CI 0.42–1.41), GSTT1 (33.2% and 27.7%, OR-1.12, 95% CI 0.63–2.0) individually and combined GSTM1 and GSTT1 (10.8% and 3.7%, OR-0.31, 95% CI 0.07–1.42) were observed in studied population.

Conclusions

In our studied population, the frequency of GSTM1 null genotypes was found deviated from Inter- and Intra-Indian ethnic groups. However, the frequency of homozygous null type of GSTT1 was not significantly different, when compared to previous Indian studies, comparison with global ethnic groups showed deviation. Thus, our study has highlighted possible susceptibility risk to various xenobiotics in the Doon population of Himachal Pradesh, India.

Influence of GSTM1, GSTT1, and GSTP1 genetic polymorphisms on disorders in transplant patients: a systematic review

The glutathione-S-transferase (GST) enzymes are phase II isoenzymes responsible for protection against free radicals and xenobiotics. Since these proteins are described as polymorphic, polymorphisms in genes that encode them may alter enzymatic function and contribute to oxidative stress. In this context, such polymorphisms were already associated with several diseases and multiple therapeutic outcomes. A systematic review was performed to evaluate studies regarding the association between polymorphisms in three genes encoding enzymes of the GST family - GSTM1, GSTT1, and GSTP1 - and disorders in transplant patients. A total of 125 articles on which inclusion and exclusion criteria were applied were identified at PubMed database. Thirty-two studies met the target criteria and were included in the review. The mechanisms by which GST genotypes influence the development of disorders in transplant patients differ by disorder: they may participate in it by decreasing metabolism of drugs administered to patients undergoing transplantation, then exposing them to greater toxicity; by decreasing the repair ability against oxidative stress; or by encoding proteins that may be recognized as foreign, setting of an alloimmune reaction. Although some results are better established - such as GSTM1 null genotype's role in the development of toxicity events in transplant patients - others require further evidences, as GST influence on the development of pulmonary decline and posttransplant diabetes mellitus (PTDM). The importance of investigating these associations lies in a personalized medicine, in which the high-risk genotype patient has its treatment individualized and its care for prophylaxis and surveillance increased, potentially reducing this population's morbimortality.

Cytokinesis-block micronucleus cytome (CBMN-CYT) assay and its relationship with genetic polymorphisms in welders

Fumes generated in the welding process are composed of micrometric and nanometric particles that form when metal fumes condense. The International Agency for Research on Cancer established that many compounds derived from the welding process are carcinogenic to humans. Still, there are few studies related to the role of genetic polymorphisms. This work aimed to analyze the influence of OGG1 Ser326Cys, XRCC1 Arg280His, XRCC1 Arg194Thr, XRCC1 Arg399Gln, XRCC3 Thr241Met, GSTM1, and GSTT1 gene polymorphisms on DNA damage of 98 subjects occupationally exposed to welding fumes and 100 non exposed individuals. The results showed that individuals exposed to welding fumes with XRCC3 Thr241Thr, XRCC3 Thr241Met, and GSTM1 null genotypes demonstrated a significantly higher micronucleus frequency in lymphocytes. In contrast, individuals with XRCC1 Arg399Gln and XRCC1 Gln399Gln genotypes had significant levels of NPBs. OGG1 326 Ser/Cys, OGG1 326 Cys/Cys, XRCC1 194Arg/Thr, XRCC1 194Thr/Thr, and GSTT1 null genotypes exhibited significantly higher apoptotic values. Also, XRCC1 194Arg/Trp, XRCC1 194Thr/Thr, and GSTM1 null genotype carriers had higher necrotic levels compared to XRCC1 194Arg/Arg and GSTM1 nonnull carriers. Compositional analysis revealed the presence of iron, manganese, silicon as well as particles smaller than 2 μm that adhere to each other and form agglomerates. These results may be associated with a mixture of components, such as nitrogen dioxide, carbon monoxide, and metallic fumes, leading to significant DNA damage and cell death processes. These findings demonstrated the importance of the association between individual susceptibility and DNA damage levels due to occupational exposure to welding fumes; and constitute one of the first studies carried out in exposed workers from Colombia.

Up-regulation of GSTT1 in serous ovarian cancer associated with resistance to TAXOL / carboplatin

Serous ovarian cancer (SOC) is the most common women cancer and the leading cause of cancer-related mortality among the gynaecological malignancies. Although effective chemotherapeutics combined with surgery are developed for the treatment, the five-year survival rate is unsatisfactory due to chemoresistance. To overcome this shortcoming of chemotherapy, we established taxol and carboplatin resistant SOC cell lines for the understandings of the molecular and cellular mechanisms of chemoresistance. Here, we found that these chemoresistant cell lines showed less viability and proliferation, due to more cells arrested at G0/G1 phase. Glutathione-S-transferases-theta1 (GSTT1) was significantly upregulated in these chemoresistant cells, along with other chemoresistant genes. Meanwhile, GSTT1 expression was also significantly upregulated in the SOC patient tissues after taxol treatment, indicating this upregulation was physiologically relevant to chemotherapy. Further, suppression of GSTT1 expression by shRNA in SOC cell lines led to more sensitivity to drug treatment, through increasing divided cells and promoting cell death. Moreover, the expression of DNA topoisomerase 1 (Topo I) was in synergy with that of GSTT1 in the chemoresistant cells, and GSTT1 can bind to Topo I in vitro, which suggested GSTT1 could function through DNA repair mechanism during chemoresistance. In summary, our data imply that GSTT1 may be a potential biomarker or indicator of drug resistance in serous ovarian cancer.

Investigation of the relationship between GSTM1 gene variations and serum trace elements, plasma malondialdehyde levels in patients with colorectal cancer

BACKGROUND

The aim of this study is to investigate of the relationship between GSTM1 gene variations and serum trace elements, plasma malondialdehyde levels in patient with colorectal cancer. Mateials and Methods. Genotype distributions of GSTM1 gene variations were determined using real-time polymerase chain reaction method. Serum trace element levels were determined using atomic absorption spectrophotometer method and plasma MDA levels were measurement by spectrophotometric method.

RESULTS

Serum Cu levels, plasma MDA levels and Cu/Zn ratio were determined significantly higher in the group of CRC patient carrying the GA heterozygous genotype of the GSTM1 (rs 112,778,559) gene variation compared to healthy controls (p < 0.05). Serum Cu, Zn levels, plasma MDA levels and Cu/Zn ratio were determined significantly higher in patients carrying GG homozygous genotype of the GSTM1 (rs 112778559) gene variation compared to healthy controls carrying same genotype (p < 0.05). Serum Cu, Zn levels, plasma MDA levels and Cu/Zn ratio were determined significantly higher in the group of CRC patient carrying the GG homozygous genotype of the GSTM1 (rs 12068997) gene variation compared to healthy controls (p < 0.05). On the other hand, serum Se levels were detected significantly lower in CRC patients carrying GA heterozygous and GG homozygous genotypes for GSTM1 (rs 112,778,559) and (rs 12,068,997) gene variations compared to healthy controls (p < 0.05).

CONCLUSION

In our study, the evaluation of serum Cu, Zn and Se trace element levels and plasma MDA levels according to GSTM1 gene variations genotype distributions were enabled to obtain important biomarkers in terms of CRC development and progression.

Role of ABCB1 and glutathione S-transferase gene variants in the association of porphyria cutanea tarda and human immunodeficiency virus infection

In Argentina, porphyria cutanea tarda (PCT) is strongly associated with infection with human immunodeficiency virus (HIV); however, whether the onset of this disease is associated with HIV infection and/or the antiretroviral therapy has not been determined. The ABCB1 gene variants c.1236C>T, c.2677G>T/A and c.3435C>T affect drug efflux. The GSTT1 null, GSTM1 null and GSTP1 (c.313A>G) gene variants alter Glutathione S-transferase (GST) activity, modifying the levels of xenobiotics. The aim of the present study was to evaluate the role of genetic variants in initiation of PCT and to analyze the genetic basis of the PCT-HIV association. Control individuals, and HIV, PCT and PCT-HIV patients were recruited, PCR-restriction fragment length polymorphism was used to genotype the ABCB1 and GSTP1 variants, and multiplex PCR was used to study the GSTM1 and GSTT1 variants. The high frequency of c.3435C>T (PCT and PCT-HIV) and c.1236C>T (PCT) suggested that the onset of PCT were not specifically related to HIV infection or antiretroviral therapy for these variants. c.2677G>T/A frequencies in the PCT-HIV patients were higher compared with the other groups, suggesting that a mechanism involving antiretroviral therapy served a role in this association. PCT-HIV patients also had a high frequency of GSTT1 null and low frequency for GSTM1 null variants; thus, the genetic basis for PCT onset may involve a combination between the absence of GSTT1 and the presence of GSTM1. In conclusion, genes encoding for proteins involved in the flow and metabolism of xenobiotics may influence the PCT-HIV association. The present study is the first to investigate the possible role of GST and ABCB1 gene variants in the triggering of PCT in HIV-infected individuals, to the best of our knowledge, and may provide novel insights into the molecular basis of the association between PCT and HIV.

Glutathione S-transferases gene polymorphism influence on the age of diabetes type 2 onset

INTRODUCTION

Type 2 diabetes (T2D) is a multifactorial disease affecting mostly adults older than 40 years. The aim of the study was to examine GST gene polymorphism influence on the risk of T2D, especially in young adults.

RESEARCH DESIGN AND METHODS

200 diabetic patients and 221 healthy controls participated in this study. Three GST gene polymorphism have been analyzed: GSTP1 (single-nucleotide polymorphism Ile₁₀₅Val), homozygous deletion of GSTT1 (null/null) and GSTM1 (null/null), using TaqMan real-time quantitative PCR.

RESULTS

The distribution of examined polymorphisms was similar in patient group and control group. Statistically significant differences were demonstrated for the combination of GSTP1 Val/Val and GSTT1 null/null genotypes between patients diagnosed before 40 years of age and healthy people (12.5% vs 0.9%, p=0.016). Moreover, all three examined gene polymorphism together (GSTP1 Val/Val, GSTM1nul/null and GSTT1 null/null genotype) was observed in 12.5% of patients diagnosed before 40 years of age and in 0.5% of healthy individuals (p=0.013).

CONCLUSION

In conclusion, the results suggest that GST polymorphism may be one of the risk factors for developing T2D at a younger age than the T2D population average.

Individual and combined effects of GSTM1 and GSTT1 polymorphisms on colorectal cancer risk: an updated meta-analysis

BACKGROUND

The presence or absence of glutathione S-transferase M1 gene (GSTM1) and glutathione S-transferase T1 gene (GSTT1) polymorphisms, and their combined effects have been suggested as a risk factor for colorectal cancer (CRC). However, the results are inconsistent.

OBJECTIVES

An updated meta-analysis was performed to solve the controversy.

METHODS

Meta-analyses of Observational Studies in Epidemiology (MOOSE) guidelines were used.

RESULTS

Overall, the GSTM1 null genotype was associated with an increased CRC risk in Caucasians (odds ratio (OR) = 1.14, 95% confidence interval (CI): 1.05-1.23), Asians (OR = 1.19, 95% CI: 1.08-1.32), high-quality studies (OR = 1.12, 95% CI: 1.06-1.18). Moreover, the GSTM1 null genotype was also associated with an increased colon cancer risk (OR = 1.32, 95% CI: 1.16-1.51). The GSTT1 null genotype was also associated with an increased CRC risk in Asians (OR = 1.08, 95% CI: 1.02-1.15) and Caucasians (OR = 1.24, 95% CI: 1.09-1.41). Moreover, The GSTT1 null genotype was associated with an increased rectal cancer risk (OR = 1.13, 95% CI: 1.01-1.27, I2 = 8.3%) in subgroup analysis by tumor location. Last, the GSTM1 null/GSTT1 null genotype was associated with an increased CRC risk in Asians.

CONCLUSION

This meta-analysis indicates that the GSTM1 and GSTT1 null genotypes are associated with increased CRC risk in Asians and Caucasians, and the GSTM1 null/GSTT1 null genotype was associated with increased CRC risk in Asians.

CORRELATION ANALYSIS OF GSTP1 GENE POLYMORPHISM WITH MORBIDITY OF PRIMARY METASTATIC COLORECTAL CANCER

Colorectal cancer (CRC) is one of the most common malignancies. Susceptibility to malignant processes is mediated by genetically driven differences in the effectiveness of detoxification of potential carcinogens. One of the factors that may influence the risk of CRC is the glutathione-S-transferase (GST) gene family that encodes glutathione transferase enzymes. The GSTP1 gene is expressed both in normal and pathological conditions. Determining its specific alleles may be a marker of CRC. The aim of the research – to study GSTP1 gene polymorphism, which is likely to be more common among patients with primary metastatic colorectal cancer compared with healthy population. Materials and methods. The study involved 12 patients with primary metastatic colorectal cancer aged 43 to 72 years, the control group was represented by a sample of 31 people without cancer. Results. The incidence of advanced CRC in the presence of GSPT1 Val / Val (aa) polymorphism is statistically significantly higher than in the presence of Ile / Ile (AA) and Ile / Val (Aa) GSPT1 polymorphism. Conclusions. Among people with GSTP1 Val / Val (aa) polymorphism, primary CRC is 4.4 times more likely than among people with GSPT1 Ile / Ile (AA) and Ile / Val (Aa) polymorphisms, which are statistically significant (P < 0.05). The obtained results indicate the possibility of conducting a genetic study of GSTP1 polymorphism to form groups of potential risk of CRC.

The Influence of Red Meat on Colorectal Cancer Occurrence Is Dependent on the Genetic Polymorphisms of S-Glutathione Transferase Genes

BACKGROUND

It is postulated that both individual genotype and environmental factors such as diet may modify the risk of developing colorectal cancer (CRC). The influences of GST gene polymorphism and red meat intake on CRC occurrence in the Polish population were analyzed in this study.

METHODS

Genotyping was performed with the qPCR method.

RESULTS

A high frequency of meat consumption was associated with an over 2-fold increase in the risk of colorectal cancer odds ratio (OR) adjusted for sex and age = 2.4, 95% confidence interval (CI); 1.3-4.4). However, after analyzing the genetic profiles, in the absence of polymorphisms of all three analyzed genes, there was no association between a high frequency of meat consumption and the occurrence of CRC. In the case of GSTM1 gene polymorphism, the high frequency of meat consumption increased the risk of CRC by almost more than 4 times (OR adjusted for sex and age = 3.8, 95% CI: 1.6-9.1). For GSTP1 gene polymorphism, a 3-fold increase in CRC risk was observed with a high frequency of meat consumption (OR adjusted for sex and age = 3.4, 95% CI: 1.4-8.1). In the case of GSTT1 gene polymorphism, the increase in risk of CRC was not statistically significant (OR adjusted for sex and age = 1.9, 95% CI: 0.4-8.5).

CONCLUSIONS

The frequency of red meat intake in non-smokers increases the risk of colon cancer in the case of GST gene polymorphisms.