Genotype and Phenotype of Glutathione-S-Transferase in Patients with Head and Neck Carcinoma

Gstm1/Gstt1 is essential for reducing cisplatin ototoxicity in CBA/CaJ mice

Cisplatin is a widely used chemotherapeutic agent. However, its clinical utility is limited because of cisplatin-induced ototoxicity. Glutathione S-transferase (GST) was found to play a vital role in reducing cisplatin ototoxicity in mice. Deletion polymorphisms of GSTM1 and GSTT1, members of the GST family, are common in humans and are presumed to be associated with cisplatin-induced hearing impairment. However, the specific roles of GSTM1 and GSTT1 in cisplatin ototoxicity are not completely clear. Here, under cisplatin treatment, simultaneous deletion of Gstm1 and Gstt1 lead to a more profound hearing loss in CBA/CaJ mice (Gstm1/Gstt1-DKO) than in wild-type mice. The Gstm1/Gstt1-DKO mice, in which phase II detoxification genes were upregulated, exhibited more severe oxidative stress and higher outer hair cell apoptosis in the cochleae than the control mice. Thus, our study revealed that Gstm1 and Gstt1 protect auditory hair cells from cisplatin-induced ototoxicity in the CBA/CaJ mice, and genetic screening for GSTM1 and GSTT1 polymorphisms could help determine a standard cisplatin dose for cancer patients undergoing chemotherapy.

Glutathione S-transferase M1 and T1 genes deletion polymorphisms and blood pressure control among treated essential hypertensive patients in Burkina Faso

OBJECTIVE

Glutathione S-transferases have been associated with experimental resistance to some drugs. The present study investigated the factors associated with blood pressure control in patients with essential hypertension, especially the role of GSTT1 and GSTM1 genes polymorphisms. This cross-sectional study in Burkina Faso consisted of 200 patients with essential hypertension and under treatment.

RESULTS

In the present study, 57.5% (115/200) of patients had their hypertension under control. No statistically significant difference was found between controlled and uncontrolled groups for anthropometric and biochemical parameters as well as for GSTT1 or GSTM1 gene polymorphisms (all p > 0.05). Current alcohol consumption (OR = 3.04; CI 1.88-6.13; p < 0.001), Physical inactivity (OR = 3.07; CI 1.71-5.49; p < 0.001), severe hypertension before any treatment (Grade III [OR = 3.79; CI 2.00-7.17; p < 0.001]) and heart damage (OR = 3, 14; CI 1.59-6.02; p < 0.001) were statistically more frequent in uncontrolled essential hypertensive patients than controlled hypertensive patients.

Homozygous deletion of both GSTM1 and GSTT1 genes is associated with higher CD4+ T cell counts in Ghanaian HIV patients

Glutathione S-transferase (GST) family of enzymes are involved in a two-stage detoxification process of a wide range of environmental toxins, carcinogens and xenobiotics. The GST enzymes play important roles in oxidative stress pathways, and polymorphisms in the GSTM1 and GSTT1 genes mediate susceptibility and outcome in different diseases. Human immunodeficiency virus (HIV) infection is associated with oxidative stress, but there is limited data on the frequency of deleted GSTM1 and GSTT1 genes in HIV/AIDS patients and their effect on progression among Ghanaians. This study sought to investigate the association between homozygous deletion of GSTM1 and GSTT1 genes (both null deletion) with HIV/AIDS disease progression in Ghanaian patients. HIV-infected individuals on antiretroviral therapy (ART), ART-naïve HIV patients, and HIV seronegative individuals were recruited for the study. HIV/AIDS disease progression was assessed by measuring CD4+ cell count and viral load of the patients, and GST polymorphism was determined by amplifying the GSTT1 and GSTM1 genes using multiplex PCR, with CYP1A1 gene as an internal control. The mean CD4+ count of patients that were naïve to ART (298 ± 243 cells/mm3) was significantly lower than that of patients on ART (604 ± 294 cells/mm3), and viral load was significantly lower in the ART-experienced group (30379 ± 15073 copies/mm3) compared to the ART-naïve group (209882 ± 75045 copies/mm3). Frequencies of GSTM1 and GSTT1 deletions were shown to be 21.9% and 19.8%, respectively, in the HIV patients, and patients with homozygous deletion of both GSTM1 and GSTT1 were more likely to have their CD4+ count rising above 350 cells/mm3 (OR = 6.44, 95% CI = 0.81-51.49, p = 0.039) suggesting that patients with homozygous deletion of GSTM1 and GSTT1 genes have slower disease progression. The findings of this study show that double deletion of glutathione S-transferases M1 and T1 is statistically associated with normal CD4+ count in patients diagnosed with HIV/AIDS. Further study is required to investigate the clinical importance of the both null deletion in HIV patients.

Functional compensation of glutathione S-transferase M1 (GSTM1) null by another GST superfamily member, GSTM2

The gene for glutathione-S-transferase (GST) M1 (GSTM1), a member of the GST-superfamily, is widely studied in cancer risk with regard to the homozygous deletion of the gene (GSTM1 null), leading to a lack of corresponding enzymatic activity. Many of these studies have reported inconsistent findings regarding its association with cancer risk. Therefore, we employed in silico, in vitro, and in vivo approaches to investigate whether the absence of a functional GSTM1 enzyme in a null variant can be compensated for by other family members. Through the in silico approach, we identified maximum structural homology between GSTM1 and GSTM2. Total plasma GST enzymatic activity was similar in recruited individuals, irrespective of their GSTM1 genotype (positive/null). Furthermore, expression profiling using real-time PCR, western blotting, and GSTM2 overexpression following transient knockdown of GSTM1 in HeLa cells confirmed that the absence of GSTM1 activity can be compensated for by the overexpression of GSTM2.

Expression of glutathione S-transferase M2 in stage I/II non-small cell lung cancer and alleviation of DNA damage exposure to benzo[a]pyrene

Glutathione S-transferases (GSTs) are a family of inducible enzymes that are important in carcinogen detoxification. GST-Mu class is showing the high activity towards most polycyclic aromatic hydrocarbon (PAH) epoxide. Our objective is to clarify the expression of GST-M2 in non-small-cell lung carcinoma (NSCLC) patients and to determine the role of GST-M2 in protecting against DNA damage. We detected changes in GST-M2 expression at mRNA levels with a panel of lung cell lines and clinical samples of malignant and paired adjacent non-malignant tissues from 50 patients with stage I or II non-small-cell lung carcinoma using real-time RT-PCR. Comet assay and gamma-H2AX were used to clarify whether DNA damaged was protected by GST-M2. Our data demonstrate that the expression of GST-M2 in tumor tissues is significantly lower than in paired adjacent non-malignant tissues (p=0.016). Loss of GST-M2 is closely associated with age, gender, T value, N value and cell differentiation (p<0.05) in early stage I/II patients. Downregulation of GST-M2 is mediated through aberrant hypermethylation in lung cancer cell lines. Protection against B[a]P-induced DNA damage by GST-M2 in lung cancer cells was detected by Comet assay and gamma-H2AX. In conclusion, DNA hypermethylation altered and reduced GST-M2 expression that resulted in susceptible to benzo[a]pyrene (B[a]P) induced DNA damage. It implies that GST-M2 reduction occurs prior to tumorigenesis.

Meta-analysis and pooled analysis of GSTM1 and CYP1A1 polymorphisms and oral and pharyngeal cancers: a HuGE-GSEC review

The association of GSTM1 and CYP1A1 polymorphisms and oral and pharyngeal cancers was assessed through a meta-analysis of published case-control studies and a pooled analysis of both published and unpublished case-control studies from the Genetic Susceptibility to Environmental Carcinogens database (http://www.upci.upmc.edu/research/ccps/ccontrol/index.html ). Thirty publications used in the meta-analysis included a total of 7783 subjects (3177 cases and 4606 controls); 21 datasets, 9397 subjects (3130 cases and 6267 controls) were included in the pooled analysis. The GSTM1 deletion was 2-fold more likely to occur in African American and African cases than controls (odds ratio: 1.7, 95% confidence interval: 0.9-3.3), although this was not observed among whites (odds ratio: 1.0, 95% confidence interval: 0.9-1.1). The meta-analysis and pooled analysis showed a significant association between oral and pharyngeal cancer and the CYP1A1 MspI homozygous variant (meta-ORm2/m2: 1.9, 95% confidence interval: 1.4-2.7; Pooled ORm2m2: 2.0, 95% confidence interval: 1.3-3.1; ORm1m2 or [infi]m2m2: 1.3, 95% confidence interval: 1.1-1.6). The association was present for the CYP1A1 (exon 7) polymorphism (ORVal/Val: 2.2, 95% confidence interval: 1.1-4.5) in ever smokers. A joint effect was observed for GSTM1 homozygous deletion and the CYP1A1 m1m2 variant on cancer risk. Our findings suggest that tobacco use and genetic factors play a significant role in oral and pharyngeal cancer.

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

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

Aim

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

Material and Method

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

Results

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

Conclusion

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

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

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

Genetic polymorphisms of microsomal epoxide hydroxylase and glutathione S-transferases M1, T1 and P1, interactions with smoking, and risk for esophageal (Barrett) adenocarcinoma

BACKGROUND

The aim of this case-control study was to test the hypothesis that polymorphisms of the microsomal epoxide hydroxylase (mEH) and glutathione S-transferase (GST) genes modulate the susceptibility to esophageal adenocarcinoma (EADC) associated with smoking.

METHODS

Cases included patients with gastroesophageal reflux disease (GERD) (n=126), Barrett esophagus (BE) (n=125), and EADC (n=56); controls comprised 95 strictly asymptomatic individuals. Genomic DNA was extracted from blood samples, and PCR-based assays were used to genotype mEH (slow allele, fast allele, predicted activity) and GSTM1, GSTT1 and GSTP1. Logistic regression was used to study associations between smoking and genotype, adjusting for age, gender and alcohol consumption.

RESULTS

Relative to asymptomatic controls, no significant differences were found for the distribution of mEH and GST polymorphic variants in cases with GERD, BE or EADC. Smoking was a risk factor for EADC, especially when cigarette exposure was greater than 30 pack-years (adjusted odds ratio [OR] 6.11, 95% confidence interval [CI] 2.2-17.32; P=0.001). The strong association between smoking and EADC was seen preferentially in patients with the active allele of either GSTM1 (OR 7.9, 95% CI 1.14-54.76; P=0.003) or GSTT1 (OR 3.2, 95% CI 1.23-8.35; P=0.004).

CONCLUSIONS

Cigarette smoking is an independent risk factor for EADC, and in particular for heavy smokers. The strong statistical association between smoking and risk for EADC in individuals with the active allele of either GSTM1 or GSTT1 may have potential clinical application in endoscopic surveillance programs to identify individuals with BE at increased risk for progression to EADC.

Molecular Prognosticators and Genomic Instability in Papillary Thyroid Cancer

OBJECTIVES/HYPOTHESIS

Tumor progression has been attributed to the accumulation of DNA damage concurrent with selection of advantageous mutations; this DNA damage may result from failure to maintain genomic integrity or from susceptibility to carcinogens. Glutathione S-transferases (GSTs), enzymes that metabolize many carcinogens, may play a role in preserving genome integrity. The objectives of this study are to assess the relationship of GST genotypes with prognosis, clinicopathologic parameters, and genomic instability in papillary thyroid cancer.

STUDY DESIGN

Prospective analysis.

METHODS

GSTM1 and GSTT1 genotypes of 35 matched normal and papillary thyroid cancer specimens were determined by polymerase chain reaction (PCR) using primers specific for the coding sequences of each gene. Genomic instability was measured by intersimple sequence repeat PCR for each tumor/normal pair and compared with the GAMES prognostic scoring system and clinicopathologic parameters including age, extrathyroidal extension, tumor grade, size, stage metastasis, sex, and smoking history.

RESULTS

GSTM1 and GSTT1 null genotypes were found in the normal tissues of 46% and 45%, respectively. No gene losses were detected in the tumor specimens. A significant association between the GSTM1 null genotype and increased risk of recurrence and death was observed. Elevated GII correlated with smoking and tumor stage but not with GST genotype.

CONCLUSION

The association of GSTM1 null genotype with intermediate and high risk GAMES categories suggests that GSTM1 provides some protection against disease progression. However, this protection does not confer resistance to disease onset. GST genotyping may be a useful adjunct prognosticator with GAMES.