Associations of CYP1A1, GSTM1 and GSTT1 polymorphisms with lung cancer susceptibility in a Northern Indian population

Effects of Glutathione S-Transferases (GSTM1, GSTT1 and GSTP1) gene variants in combination with smoking or drinking on cancers: A meta-analysis

BACKGROUND

This meta-analysis aimed to systematically summarize the association between cancer risks and glutathione s-transferases (GSTs) among smokers and drinkers.

METHODS

Literature was searched through PubMed, Web of Science, CNKI, and WANFANG published from 2001 to 2022. Stata was used with fixed-effect model or random-effect model to calculate pooled odds ratios (ORs) and the 95% confidence interval (95% CI). Sensitivity and heterogeneity calculations were performed, and publication bias was analyzed by Begg and Egger's test. Regression analysis was performed on the correlated variables about heterogeneity, and the false-positive report probabilities (FPRP) and the Bayesian False Discovery Probability (BFDP) were calculated to assess the confidence of a statistically significant association.

RESULTS

A total of 85 studies were eligible for GSTs and cancer with smoking status (19,604 cases and 23,710 controls), including 14 articles referring to drinking status (4409 cases and 5645 controls). GSTM1-null had significant associations with cancer risks (for smokers: OR = 1.347, 95% CI: 1.196-1.516, P < .001; for nonsmokers: OR = 1.423, 95% CI: 1.270-1.594, P < .001; for drinkers: OR = 1.748, 95% CI: 1.093-2.797, P = .02). GSTT1-null had significant associations with cancer risks (for smokers: OR = 1.356, 95% CI: 1.114-1.651, P = .002; for nonsmokers: OR = 1.103, 95% CI: 1.011-1.204, P = .028; for drinkers: OR = 1.423, 95% CI: 1.042-1.942, P = .026; for nondrinkers: OR = 1.458, 95% CI: 1.014-2.098, P = .042). Negative associations were found between GSTP1rs1695(AG + GG/AA) and cancer risks among nondrinkers (OR = 0.840, 95% CI: 0.711-0.985, P = .032).

CONCLUSIONS

GSTM1-null and GSTT1-null might be related cancers in combination with smoking or drinking, and GSTP1rs1695 might be associated with cancers among drinkers.

Association of xenobiotic-metabolizing genes polymorphisms with cervical cancer risk in the Tunisian population

BACKGROUND

Host genetic characteristics and environmental factors interactions may play a crucial role in cervical carcinogenesis. We investigated the impact of functional genetic variants of four xenobiotic-metabolizing genes (AhR, CYP1A1, GSTM1, and GSTT1) on cervical cancer development in Tunisian women.

METHODS

The AhR gene polymorphism was analyzed using the tetra-primer ARMS-PCR, whereas the CYP1A1 polymorphism genotypes were identified by PCR-RFLP. A multiplex ligation-dependent polymerase chain reaction approach was applied for the analysis of GSTM1 and GSTT1 polymorphisms.

RESULTS

The homozygous A/A genotype of the AhR gene (rs2066853) and the heterozygous T/C genotype of the CYP1A1 SNP (CYP1A1-MspI) appeared to be associated with an increased risk of cervical tumorigenesis (OR^a = 2.81; OR^a = 5.52, respectively). Furthermore, a significantly increased risk of cervical cancer was associated with the GSTT1 null genotype (OR^a = 2.65). However, the null GSTM1 genotype showed any significant association with the risk of cervical cancer compared to the wild genotype (OR^a = 1.18; p = 0.784). Considering the combined effect, we noted a significantly higher association with cancer risk for individuals with at least two high-risk genotypes of CYP1A1/GSTT1 (OR^a = 4.2), individuals with at least two high-risk genotypes of CYP1A1/GSTT1/AhR (OR^a = 11.3) and individuals with at least two high-risk genotypes of CYP1A1/GSTM1/GSTT1/AhR exploitation low-risk genotype as a reference.

CONCLUSION

This study indicated that the single-gene contribution and the combined effect of xenobiotic-metabolizing gene polymorphisms (AhR, CYP1A1-MspI, GSTM1, and GSTT1) may have a considerable association with increased cervical cancer risk.

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.

Higher order genes interaction in DNA repair and cytokine genes polymorphism and risk to lung cancer in North Indians

Context

Lung cancer pathological process involves cumulative effects exerted by gene polymorphism(s), epigenetic modifications, and alterations in DNA repair machinery. Further, DNA damage due to oxidative stress, chronic inflammation, and the interplay between genetic and environmental factors is also an etiologic milieu of this malignant disease.

Aims

The present study aims to assess the prognostic value of DNA repair, cytokines, and GST gene polymorphism in lung cancer patients who had not received any neoadjuvant therapy.

Materials and Methods

In this case-control study, 127 cases and 120 controls were enrolled. DNA from the blood samples of both patients and controls was used to genotype XRCC1Arg399Gln, XPDLys751Gln, and interleukin-1 (IL-1β) genes by polymerase chain reaction (PCR)-restriction fragment length polymorphism method, whereas multiplex PCR was performed to genotype GSTT1 and GSTM1.

Results

Binary logistic regression analysis showed that XRCC1Arg399Gln-mutant genotype (Gln/Gln, odds ratio [OR] = 4.6, 95% confidence interval [CI]: 2.2-9.6) and GSTT1 null (OR = 2.7, 95% CI: 1.6-4.5) were linked to cancer susceptibility. Generalized multidimensional reduction analysis of higher order gene-gene interaction using cross-validation testing (CVT) accuracy showed that GSTT1 (CVT 0.62, P = 0.001), XPD751 and IL-1β (CVT 0.6, P = 0.001), and XRCC1399, XPD751, and interleukin-1 receptor antagonists (IL-1RN) (CVT 0.98, P = 0.001) were single-, two-, and three-factor best model predicted, respectively, for lung cancer risk. Classification and regression tree analysis results showed that terminal nodes which contain XRCC1399-mutant genotype (AA) had increased the risk to lung cancer.

Conclusion

The present study demonstrated that XRCC1399 (Gln/Gln), GSTT1, and IL-1RN allele I, I/II served as the risk genotypes. These genes could serve as the biomarkers to predict lung cancer risk.

Genetic Polymorphisms of Xenobiotic Metabolizing Genes (GSTM1, GSTT1, GSTP1), Gene-Gene Interaction with Association to Lung Cancer Risk in North India; A Case Control Study

Aim: In this case control study involving, 220 human subjects; polymorphisms in xenobiotic metabolizing genes (GST-M1, -T1 and -P1) and their association to lung cancer risk is being analysed among smokers and nonsmokers. GSTM1 or GSTT1 gene polymorphism and amino acid changes in GSTP1 have been correlated and may be associated to lung cancer risk. Other factor includes exposure to environmental pollutants and life style choices. We have explored gene-gene and gene-environment interaction in the aetiology of lung cancer risk among north Indian population. Patients and Methods: For the study we have collected 120 lung cancer patient blood samples from Kamala Nehru Memorial Cancer Hospital, Allahabad, Uttar Pradesh and 100 matched controls. DNA was isolated and GST-M1 and - T1 genotyping were assessed by multiplex PCR whereas the GSTP1 polymorphism was analysed using restriction fragment length polymorphism. The risk of lung carcinogenesis was assessed using logistic regression analysis calculating the odd ratio (OR) with 95% confidence interval (CI). Results: The risk of lung carcinogenesis was three fold higher for null GSTT1 (OR=3.045, 95%CI=1.750-5.301, p-value <0.001) genotype; whereas other two types; GSTM1 (OR= 1.342, 95% CI=0.788-2.284, p-value=0.270) and GSTP1 (OR=0.806, 95% CI=0.526-1.236, p-value=0.323) showed no association to lung cancer susceptibility respectively. Smokers diagnosed with lung cancer had more null genotypes for GSTT1 (OR=4.773, 95%CI=1.939-11.751, p<0.001). The ‘at risk’ genotype combination GSTM1 (null) /GSTT1 (null) (OR=1.76, 95%CI; 0.920-3.370, p-value=0.03) showed increased susceptibility to lung cancer risk. The genotype combination of GSTT1 (null)/GSTP1 (Ile/Ile) (p=0.009) was associated with increased lung cancer risk. Conclusion: The results of this study suggest that; GSTT1 null genotype were more susceptible for lung cancer risk and smoking increases the susceptibility for lung cancer several folds among the North Indian population. Gene-gene interaction for null genotypes of GSTM1 and GSTT1 were correlated with higher risk of having lung cancer.

Association of 12 polymorphic variants conferring genetic risk to lung cancer in Indian population: An extensive meta-analysis

Candidate gene as well as genome-wide association studies identified several polymorphic variants to be associated with lung cancer worldwide including in India. However, contradictory results have failed to estimate the overall effect of the polymorphic variants on the disease. Textmining was conducted on PubMed following specific search strings to gather all the publications related to genetic association with lung cancer in India. Out of 211 PubMed hits only 30 studies were selected for meta-analysis following specific inclusion criteria. Heterogeneity between studies was calculated by Cochran's Q-test (P < 0.05) and heterogeneity index (I² ). Publication bias was visualized by funnel plots and Egger's regression test. For each variant, following a fixed-effect model, summary odds ratio (OR) along with 95% confidence interval (CI) was estimated. The meta-analysis revealed three polymorphic variants viz. 'deletion polymorphism (del1) (OR = 1.39, 95% CI = 1.03-1.87, P = 0.027) in GSTT1', 'deletion polymorphism (del2) (OR = 1.30, 95% CI = 1.01-1.67, P = 0.038) in GSTM1' and 'rs1048943 (OR = 1.98, 95% CI = 1.27-3.10, P = 0.002) in CYP1A1' to be associated with lung cancer. However, after multiple testing correction, only rs1048943 was found to be significantly associated (P value = 0.0321) with lung cancer. None of the polymorphic variants showed any evidence of heterogeneity between studies or of publication bias. Our meta-analysis revealed strong association of rs1048943 in CYP1A1, but a suggestive association of deletion polymorphisms in GSTT1 and GSTM1 with lung cancer, which provides a comprehensive insight on the overall effect of the polymorphic variants, reported in various case-control studies on Indian population, on the risk of lung cancer development. Environ. Mol. Mutagen. 58:688-700, 2017. © 2017 Wiley Periodicals, Inc.

Metabolic Phase I (CYPs) and Phase II (GSTs) Gene Polymorphisms and Their Interaction with Environmental Factors in Nasopharyngeal Cancer from the Ethnic Population of Northeast India

Multiple genetic and environmental factors and their interaction are believed to contribute in the pathogenesis of Nasopharyngeal Cancer (NPC). We investigate the role of Metabolic Phase I (CYPs) and Phase II (GSTs) gene polymorphisms, gene-gene and gene-environmental interaction in modulating the susceptibility to NPC in Northeast India. To determine the association of metabolic gene polymorphisms and environmental habits, 123 cases and 189 controls blood/swab samples were used for PCR and confirmed by Sanger sequencing. Analysis for GSTM1 and GSTT1 gene polymorphism was done by multiplex PCR. The T3801C in the 3'- flanking region of CYP1A1 gene was detected by PCR-RFLP method. The Logistic regression analysis was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI). The GSTM1 null genotype alone (OR = 2.76) was significantly associated with NPC risk (P < 0.0001). The combinations of GSTM1 null and GSTT1 null genotypes also higher, 3.77 fold (P < 0.0001), risk of NPC, while GSTM1 null genotype along with CYP1A1 T3801C TC + CC genotype had 3.22 (P = 0.001) fold risk. The most remarkable risk was seen among individual carrying GSTM1 null, GSTT1 null genotypes and CYP1A1 T3801C TC + CC genotypes (OR = 5.71, P = 0.001). Further; analyses demonstrate an enhanced risk of NPC in smoked meat (OR = 5.56, P < 0.0001) and fermented fish consumers (OR = 5.73, P < 0.0001) carrying GSTM1 null genotype. An elevated risk of NPC was noted in smokers (OR = 12.67, P < 0.0001) and chewers (OR = 5.68, P < 0.0001) with GSTM1 null genotype. However, smokers had the highest risk of NPC among individuals carrying GSTT1 null genotype (OR = 4.46, P = 0.001) or CYP1A1 T3801C TC + CC genotype (OR = 7.13, P < 0.0001). The association of null genotypes and mutations of metabolic neutralizing genes along with the environmental habits (tobacco smokers and chewers, smoke meat, fermented fishes) can be used as a possible biomarker for early detection and preventive measure of NPC.

CYP1A1 and GSTP1 gene variations in breast cancer: a systematic review and case-control study

In first part of this study, a systematic review was designed to explore the involvement of CYP1A1 and GSTP1 genes in breast cancerogenesis. Based on systematic review, we designed a study to screen CYP1A1 and GSTP1 genes for mutation and their possible association with breast carcinogenesis. A total of 400 individuals were collected and analyzed by PCR-SSCP. After sequence analysis of coding region of CYP1A1 we identified eleven mutations in different exons of respective gene. Among these eleven mutations, ~3 folds increased breast cancer risk was found associated with Asp82Glu mutation (OR 2.99; 95% CI 1.26-7.09), with Ser83Thr mutation (OR 2.99; 95% CI 1.26-7.09) and with Glu86Ala mutation (OR 3.18; 95% CI 1.27-7.93) in cancer patients compared to controls. Furthermore, ~4 folds increase in breast cancer risk was found associated with Asp347Glu, Phe398Tyr and 5178delT mutations (OR 3.92; 95% CI 1.35-11.3) in patients compared to controls. The sequence analysis of GSTP1 resulted in identification of total five mutations. Among these five mutations, ~3 folds increase in breast cancer risk was observed associated with 1860G>A mutation, with 1861-1876delCAGCCCTCTGGAGTGG mutation (OR 2.70; 95% CI 1.10-6.62) and with 1861C>A mutation (OR 2.97; 95% CI 1.01-8.45) in cancer patients compared to controls. Furthermore, ~5 folds increase in breast cancer risk was associated with 1883G>T mutation (OR 4.75; 95% CI 1.46-15.3) and ~6 folds increase in breast cancer risk was found associated with Iso105Val mutation (OR 6.43; 95% CI 1.41-29.3) in cancer patients compared to controls. Our finding, based on systematic review and experimental data suggest that the polymorphic CYP1A1 and GSTP1 genes may contribute to risk of developing breast cancer.

CYP1A1 MspI Polymorphism and Cervical Carcinoma Risk in the Multi-Ethnic Population of Malaysia: a Case-Control Study

BACKGROUND

Tobacco smoking is considered a risk factor for cervical cancer development due to the presence of tobacco based carcinogenic metabolites in cervical cells of female smokers. In this study, we investigated the role of the T3801C (MspI) polymorphism of CYP1A1, a gene encoding an enzyme necessary for the initiation of tobacco based carcinogen metabolism, on cervical cancer risk. The T to C substitution may alter CYP1A1 activities, potentially elevating cervical cancer risk. Since results of gene-disease association studies vary according to the study population, the multi-ethnic population of Malaysia provides an excellent representative cohort for identifying and comparing the cervical cancer risk among the 3 major ethnics in Southeast Asia in relation to CYP1A1 MspI polymorphism.

MATERIALS AND METHODS

A total of 195 Thin Prep Pap smear samples from HPV negative and cancer free females were randomly selected as controls while 106 formalin fixed paraffin embedded samples from females with invasive cervical cancer were randomly selected for the cases group. The polymorphisms were identified using restriction fragment length polymorphism (RFLP) PCR.

RESULTS

We found no significant associations between CYP1A1 MspI polymorphism and cervical cancer in the general Malaysian female population. However, upon ethnic stratification, the variant C/C genotype was significantly associated with a 4.66-fold increase in cervical cancer risk in Malay females (95% CI= 1.21-17.9; p=0.03). No significant association was observed in the Chinese and Indian females. Additionally, there were no significant associations in the dominant model and allele frequency model analysis in both the general and ethnically stratified female population of Malaysia.

CONCLUSIONS

Our findings suggest that the C/C genotype of CYP1A1 MspI polymorphism is associated with the development of cervical carcinoma in the Malay females of Malaysia.

Influence of the CYP1A1 T3801C Polymorphism on Tobacco and Alcohol-Associated Head and Neck Cancer Susceptibility in Northeast India

BACKGROUND

Tobacco and alcohol contain or may generate carcinogenic compounds related to cancers. CYP1A1 enzymes act upon these carcinogens before elimination from the body. The aim of this study was to investigate whether CYP1A1 T3801C polymorphism modulates the relationship between tobacco and alcohol- associated head and neck cancer (HNC) susceptibility among the northeast Indian population.

MATERIALS AND METHODS

One hundred and seventy histologically confirmed HNC cases and 230 controls were included within the study. The CYP1A1 T3801C polymorphism was determined using PCR-RFLP, and the results were confirmed by DNA sequencing. Logistic regression (LR) and multifactor dimensionality reduction (MDR) approaches were applied for statistical analysis.

RESULTS

The CYP1A1 CC genotype was significantly associated with HNC risk (P=0.045). A significantly increased risk of HNC (OR=6.09; P<0.0001) was observed in individuals with combined habits of smoking, alcohol drinking and tobacco-betel quid chewing. Further, gene-environment interactions revealed enhanced risks of HNC among smokers, alcohol drinkers and tobacco-betel quid chewers carrying CYP1A1 TC or CC genotypes. The highest risk of HNC was observed among smokers (OR=7.55; P=0.009) and chewers (OR=10.8; P<0.0001) carrying the CYP1A1 CC genotype. In MDR analysis, the best model for HNC risk was the three-factor model combination of smoking, tobacco-betel quid chewing and the CYP1A1 variant genotype (CVC=99/100; TBA=0.605; P<0.0001); whereas interaction entropy graphs showed synergistic interaction between tobacco habits and CYP1A1.

CONCLUSIONS

Our results confirm that the CYP1A1 T3801C polymorphism modifies the risk of HNC and further demonstrated importance of gene-environment interaction.

Assessment of perception of medical students in regard to links between tobacco or alcohol use and cancer

BACKGROUND

The aim of this study was to assess cancer awareness among medical students in Saudi Arabia toward tobacco and alcohol use as risk factors.

MATERIALS AND METHODS

A cross-sectional survey from October to December 2014, covering 1200 medical students, was performed.

RESULTS

Of the total, 975 (81.25%) responded. The male to female ratio was 1.00:7.125. 96/975 (9.8%) had smoked tobacco in their lifetime, and 51/975 (5.23%) were alcoholic beverage consumers. On asking them whether tobacco smoking and alcohol consumption can cause cancer, only 4/975 (0.4%) and 14/975 (1.43%) answered no for smoking and alcohol, respectively.

CONCLUSIONS

The prevalence of smoking and alcohol use is very low among medical students, which might be due to high female contribution besides social stigma. The prevalence of second-hand smoke (SHS) was found to be very high in Hail region.

Pharmacophore Development for Anti-Lung Cancer Drugs

Lung cancer is one particular type of cancer that is deadly and relatively common than any other. Treatment is with chemotherapy, radiation therapy and surgery depending on the type and stage of the disease. Focusing on drugs used for chemotherapy and their associated side effects, there is a need to design and develop new anti-lung cancer drugs with minimal side effects and improved efficacy. The pharmacophore model appears to be a very helpful tool serving in the designing and development of new lead compounds. In this paper, pharmacophore analysis of 10 novel anti-lung cancer compounds was validated for the first time. Using LigandScout the pharmacophore features were predicted and 3D pharmacophores were extracted via VMD software. A training set data was collected from literature and the proposed model was applied to the training set whereby validating and verifying similar activity as that of the most active compounds was achieved. Therefore pharmacophore develoipment could be recommended for further studies.

Epidermal growth factor receptor mutations in Japanese men with lung adenocarcinomas

BACKGROUND

Epidermal growth factor receptor (EGFR) mutations play a vital role in the prognosis of patients with lung adenocarcinoma. Such somatic mutations are more common in women who are non-smokers with adenocarcinoma and are of Asian origin. However, to our knowledge, there are few studies that have focused on men.

MATERIALS AND METHODS

One hundred and eighty-four consecutive patients (90 men and 94 women) of resected lung adenocarcinoma were studied retrospectively.

RESULTS

EGFR mutations were positive in 48.9% and negative (wild type) in 51.1%. Overall mutation was significant in women (66.0% vs. 32.2%) compared with men (p<0.001). For overall patients, EGFR mutation status was associated with gender, pStage, pT status, lepidic dominant histologic subtype, pure or mixed ground-glass nodule type on computed tomography and smoking status. However, in men, EGFR mutation status was only associated with lepidic dominant histologic subtype and not the other variables. Interestingly, the Brinkman index of men with mutant EGFR also did not differ from that for the wild type (680.0±619.3 vs. 813.1±552.1 p=0.1077).

CONCLUSIONS

The clinical characteristics of men with lung adenocarcinoma related to EGFR mutation are not always similar to that of overall patients. Especially we failed to find the relationship between EGFR mutations and smoking status in men.

Meta-analysis of the association between the rs8034191 polymorphism in AGPHD1 and lung cancer risk

BACKGROUND

Possible associations between the single nucleotide polymorphism (SNP) rs8034191 in the aminoglycosidephosphotransferase domain containing 1 (AGPHD1) gene and lung cancer risk have been studied by many researchers but the results have been contradictory.

MATERIALS AND METHODS

A computerized search for publications on rs8034191 and lung cancer risk was performed. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to assess the association between rs8034191 and lung cancer risk with 13 selected case-control studies. Sensitivity analysis, test of heterogeneity, cumulative meta-analysis, and assessment of bias were also performed.

RESULTS

A significant association between rs8034191 and lung cancer susceptibility was found using the dominant genetic model (OR=1.344, 95% CI: 1.285-1.406), the additive genetic model (OR=1.613, 95% CI: 1.503-1.730), and the recessive genetic model (OR=1.408, 95% CI: 1.319-1.503). Moreover, an increased lung cancer risk was found with all genetic models after stratification of ethnicity.

CONCLUSIONS

The association between rs8034191 and lung cancer risk was significant using multiple genetic models, suggesting that rs8034191 is a risk factor for lung cancer. Further functional studies of this polymorphism and lung cancer risk are warranted.

Expression of CYP1A1 and GSTP1 in human brain tumor tissues in Pakistan

Most of the exogenous and endogenous chemical compounds are metabolized by enzymes of xenobiotic processing pathways, including the phase I cytochrome p450 species. Carcinogens and their metabolites are generally detoxified by phase II enzymes like glutathione-S-transferases (GST). The balance of enzymes determines whether metabolic activation of pro-carcinogens or inactivation of carcinogens occurs. Under certain conditions, deregulated expression of xenobiotic enzymes may also convert endogenous substrates to metabolites that can facilitate DNA adduct formation and ultimately lead to cancer development. In this study, we aimed to test the association between deregulation of metabolizing genes and brain tumorigenesis. The expression profile of metabolizing genes CYP1A1 and GSTP1 was therefore studied in a cohort of 36 brain tumor patients and controls using Western blotting. In a second part of the study we analyzed protein expression of GSTs in the same study cohort by ELISA. CYP1A1 expression was found to be significantly high (p<0.001) in brain tumor as compared to the normal tissues, with ~4 fold (OR=4, 95%CI=0.43-37) increase in some cases. In contrast, the expression of GSTP1 was found to be significantly low in brain tumor tissues as compared to the controls (p<0.02). This down regulation was significantly higher (OR=0.05, 95%CI=0.006-0.51; p<0.007) in certain grades of lesions. Furthermore, GSTs levels were significantly down-regulated (p<0.014) in brain tumor patients compared to controls. Statistically significant decrease in GST levels was observed in the more advanced lesions (III-IV, p<0.005) as compared to the early tissue grades (I-II). Thus, altered expression of these xenobiotic metabolizing genes may be involved in brain tumor development in Pakistani population. Investigation of expression of these genes may provide information not only for the prediction of individual cancer risk but also for the prevention of cancer.

The associations between two vital GSTs genetic polymorphisms and lung cancer risk in the Chinese population: evidence from 71 studies

BACKGROUND

The genetic polymorphisms of glutathione S-transferase (GSTs) have been suspected to be related to the development of lung cancer while the current results are conflicting, especially in the Chinese population.

METHODS

Data on genetic polymorphisms of glutathione S-transferase Mu 1 (GSTM1) from 68 studies, glutathione S-transferase theta 1 (GSTT1) from 17 studies and GSTM1-GSTT1 from 8 studies in the Chinese population were reanalyzed on their association with lung cancer risk. Odds ratios (OR) were pooled using forest plots. 9 subgroups were all or partly performed in the subgroup analyses. The Galbraith plot was used to identify the heterogeneous records. Potential publication biases were detected by Begg's and Egger's tests.

RESULTS

71 eligible studies were identified after screening of 1608 articles. The increased association between two vital GSTs genetic polymorphisms and lung cancer risk was detected by random-effects model based on a comparable heterogeneity. Subgroup analysis showed a significant relationship between squamous carcinoma (SC), adenocarcinoma (AC) or small cell lung carcinoma (SCLC) and GSTM1 null genotype, as well as SC or AC and GSTT1 null genotype. Additionally, smokers with GSTM1 null genotype had a higher lung cancer risk than non-smokers. Our cumulative meta-analysis demonstrated a stable and reliable result of the relationship between GSTM1 null genotype and lung cancer risk. After the possible heterogeneous articles were omitted, the adjusted risk of GSTs and lung cancer susceptibility increased (fixed-effects model: ORGSTM1 = 1.23, 95% CI: 1.19 to 1.27, P<0.001; ORGSTT1 = 1.18, 95% CI: 1.10 to 1.26, P<0.001; ORGSTM1-GSTT1 = 1.33, 95% CI: 1.10 to 1.61, P = 0.004).

CONCLUSIONS

An increased risk of lung cancer with GSTM1 and GSTT1 null genotype, especially with dual null genotype, was found in the Chinese population. In addition, special histopathological classification of lung cancers and a wide range of gene-environment and gene-gene interaction analysis should be taken into consideration in future studies.