Combined Effect of Smoking and Polymorphisms in Tobacco Carcinogen-Metabolizing Enzymes CYP1A1 and GSTM1 on the Head and Neck Cancer Risk in North Indians

Genic-intergenic polymorphisms of CYP1A genes and their clinical impact

The humancytochrome P450 1A (CYP1A) subfamily genes, CYP1A1 and CYP1A2, encoding monooxygenases are critically involved in biotransformation of key endogenous substrates (estradiol, arachidonic acid, cholesterol) and exogenous compounds (smoke constituents, carcinogens, caffeine, therapeutic drugs). This suggests their significant involvement in multiple biological pathways with a primary role of maintaining endogenous homeostasis and xenobiotic detoxification. Large interindividual variability exist in CYP1A gene expression and/or catalytic activity of the enzyme, which is primarily due to the existence of polymorphic alleles which encode them. These polymorphisms (mainly single nucleotide polymorphisms, SNPs) have been extensively studied as susceptibility factors in a spectrum of clinical phenotypes. An in-depth understanding of the effects of polymorphic CYP1A genes on the differential metabolic activity and the resulting biological pathways is needed to explain the clinical implications of CYP1A polymorphisms. The present review is intended to provide an integrated understanding of CYP1A metabolic activity with unique substrate specificity and their involvement in physiological and pathophysiological roles. The article further emphasizes on the impact of widely studied CYP1A1 and CYP1A2 SNPs and their complex interaction with non-genetic factors like smoking and caffeine intake on multiple clinical phenotypes. Finally, we attempted to discuss the alterations in metabolism/physiology concerning the polymorphic CYP1A genes, which may underlie the reported clinical associations. This knowledge may provide insights into the disease pathogenesis, risk stratification, response to therapy and potential drug targets for individuals with certain CYP1A genotypes.

Association between the CYP1A1 MspI polymorphism and risk of head and neck cancer: a meta-analysis

The studies recommended the relationship between lots of polymorphisms with the head and neck cancers (HNCs) risk. Herein, we reported the association between the CYP1A1 MspI polymorphism and the risk of HNC in an updated meta-analysis. The PubMed/MEDLINE, Web of Science, Cochrane Library, and Scopus databases were searched until March 31, 2021, without any restrictions. Odds ratios (ORs) and 95% confidence intervals (CIs) were applied to assess a relationship between CYP1A1 MspI polymorphism and the HNC risk based on five applied genetic models by RevMan 5.3 software. Other analyses (sensitivity analysis, meta-regression, and bias analysis) were performed by CMA 2.0 software. Trial sequential analysis (TSA) was done by TSA software (version 0.9.5.10 beta). Among the databases and other sources, 501 recorded were identified that at last, 29 studies were obtained for the analysis. The pooled ORs were 1.28 (95%CI 1.09, 1.51; P = 0.003), 1.68 (95%CI 1.16, 2.45; P = 0.007), 1.24 (95%CI 1.03, 1.50; P = 0.02), 1.26 (95%CI 1.07, 1.48; P = 0.005), and 1.66 (95%CI 1.27, 2.16; P = 0.0002) for allelic, homozygous, heterozygous, recessive, and dominant models, respectively. Therefore, the m2 allele and m1/m2 and m2/m2 genotypes had significantly increased risks in HNC patients. With regards to stable results and enough samples, the findings of the present meta-analysis recommended that there was an association between CYP1A1 MspI polymorphism and the HNC risk.

Genetic susceptibility of CYP1A1 gene and risk of pesticide exposure in prostate cancer

BACKGROUND

The etiology of prostate cancer (PCa) is multi-factorial including environmental and genetic factors. Present study evaluates the association between level of pesticides, stress level and CYP1A1 gene polymorphism with PCa patients.

METHODS

A case control study was conducted with 102 PCa patients and age match symptomatic (n= 107) and asymptomatic benign prostatic hyperplasia (BPH, n= 70) patients. Pesticide level was characterized by Gas Chromatography. The oxidative stress and scavenging mechanisms were determined by biochemical method. Two polymorphisms of CYP1A1 gene, rs4646903 and rs1048943, were analyzed by polymerase chain reaction (PCR) followed by restriction fragment length polymorphism and allele specific PCR method.

RESULTS

Higher level of pesticide namely beta-hexachlorocyclohexane (β-HCH), Malathion, Chlorpyrifos and Fenvalerate were found in PCa group (all p value: < 0.05). Kruskal Wallis H test depicted that level of β-HCH and Malathion significantly correlated with higher grade of PCa (all p< 0.05). The PCa Patients with simultaneously low antioxidant activity and high stress level tended to suffer worst clinical outcomes. Dominant model of rs4646903 and rs1048943 suggested that substitution is associated with a higher risk of PCa (OR: 2.2, CI: 1.6-3.8, p: 0.009 and OR: 1.95, CI: 1.1-3.4, p: 0.026; respectively) and this risk was also influenced by smoking and pesticide exposure.

CONCLUSION

Environmental and genetic factors are reported to raise risk; person with high level of these pesticides especially in high risk genotype might be more susceptible to PCa.

Leptin -2548 G/A polymorphisms are associated to clinical progression of oral cancer and sensitive to oral tumorization in nonsmoking population

Oral cancer is causally associated with environmental carcinogens, and the susceptibility to carcinogen-mediated tumorigenesis is proposed to be genotype-dependent. Leptin (LEP) and leptin receptor (LEPR) both play a crucial role in the mediation of physiological reactions and carcinogenesis and may serve as a candidate biomarker of oral cancer. The current case-control study aimed to examine the effects of LEP -2548 G/A (rs7799039), LEPR K109R (rs1137100), and LEPR Q223R (rs1137101) single-nucleotide polymorphisms (SNPs) with or without interacting to environmental carcinogens on the risk for oral squamous cell carcinoma. The SNPs of three genetic allele, from 567 patients with oral cancer and 560 healthy controls in Taiwan were analyzed. The results shown that the patients with polymorphic allele of LEP -2548 have a significant low risk for the development of clinical stage (A/G: adjusted odds ratio [AOR] = 0.670, 95% confidence interval [CI] = 0.454-0.988, P < 0.05; A/G + G/G: AOR = 0.676, 95% CI = 0.467-0.978, P < 0.05) compared to patients with ancestral homozygous A/A genotype. In addition, an interesting result was found that the impact of LEP -2548 G/A SNP on oral carcinogenesis in subjects without tobacco consumption is higher than subjects with tobacco consumption. These results suggest that the genetic polymorphism of LEP -2548 G/A (rs7799039), LEPR K109R (rs1137100), and LEPR Q223R (rs1137101) were not associated to the susceptibility of oral cancer; SNP in LEP -2548 G/A showed a poor clinicopathological development of oral cancer; population without tobacco consumption and with polymorphic LEP -2548 G/A gene may significantly increase the risk to have oral cancer.

Tobacco smoking, alcohol drinking, betel quid chewing, and the risk of head and neck cancer in an East Asian population

BACKGROUND

The smoking prevalence among men in China is high, but the head and neck cancer incidence rates are low. This study's purpose was to investigate the impact of tobacco, betel quid, and alcohol on head and neck cancer risk in East Asia.

METHODS

A multicenter case-control study (921 patients with head and neck cancer and 806 controls) in East Asia was conducted. The odds ratio (OR) and 95% confidence interval (CI) were estimated using logistic regression.

RESULTS

Head and neck cancer risks were elevated for tobacco (OR = 1.58), betel quid (OR = 8.23), and alcohol (OR = 2.29). The total attributable risk of tobacco and/or alcohol was 47.2%. Tobacco/alcohol appeared to account for a small proportion of head and neck cancer among women (attributable risk of 2.2%). Betel quid chewing alone accounted for 28.7% of head and neck cancer.

CONCLUSIONS

Betel quid chewing is the strongest risk factor for oral cavity cancer in this Chinese population. Alcohol may play a larger role for head and neck cancer in this population than in European or U.S.

POPULATIONS

The association of the CYP1A1 Ile462Val polymorphism with head and neck cancer risk: evidence based on a cumulative meta-analysis

Objective

The aim of this study was to address the association between the Ile462Val polymorphism in the gene encoding cytochrome P450 1A1 (CYP1A1) and the risk of head and neck cancer (HNC).

Materials and methods

The Medline/PubMed, EMBASE, and Web of Science databases were searched. The strength of the association was evaluated by calculating the odds ratio (OR) with a 95% confidence interval (CI).

Results

Overall, we observed an increased risk of HNC in patients with the Ile/Val+Val/Val genotype compared to those with the Ile/Ile genotype among the 6,367 cases and 6,395 controls evaluated in the 34 eligible studies, with a pooled OR of 1.284 (95% CI: 1.119–1.473). In addition, we observed an increased risk of HNC in patients with the Ile/Val+Val/Val genotype compared to those with the Ile/Ile genotype in the subgroup analyses (OR =1.362, 95% CI: 1.102–1.685 for laryngeal cancer; OR =1.519, 95% CI: 1.253–1.843 for pharyngeal cancer; OR =1.371, 95% CI: 1.111–1.693 for Asians; and OR =1.329, 95% CI: 1.138–1.551 for patients in studies using hospital-based controls).

Conclusion

This cumulative meta-analysis suggests that the CYP1A1 Ile462Val polymorphism might contribute to the risk of HNC, particularly for pharyngeal cancer and laryngeal cancer.

CYP1A1 MspI polymorphism and the risk of oral squamous cell carcinoma: Evidence from a meta-analysis

Numerous case-control studies have investigated whether the CYP1A1 gene polymorphism is involved in the occurrence of oral squamous cell carcinoma (OSCC); however, the conclusions are inconsistent. In order to further explore the correlation and obtain a strong conclusion, a meta-analysis was performed to systematically assess the association between the CYP1A1 MspI polymorphism and risk of OSCC. In the present meta-analysis, the odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) were used to assess the association. The statistical analyses were performed with STATA 11.0 software. The heterogeneity was assessed by Q test and I²test. The final analysis included 10 studies of 1,505 cases and 1,967 controls. The overall results suggested that the CYP1A1 MspI polymorphism was significantly associated with an increased risk of OSCC (CC+TC vs. TT: OR, 1.31; 95% CI, 1.01-1.70; P=0.043; CC vs. TC+TT: OR, 2.38; 95% CI, 1.58-3.58; P<0.001; CC vs. TT: OR, 2.52; 95% CI, 1.60-3.96; P<0.001; and C vs. T: OR, 1.45; 95% CI, 1.15-1.83; P<0.001). In a stratified analysis by ethnicity, a statistically significant correlation existed in the Asian population, but not mixed-race and Caucasian populations. In conclusion, despite several limitations, the present meta-analysis established that the CYP1A1 MspI polymorphism may be a risk factor for OSCC, particularly among the Asian population.

CYP1A1 rs1048943 and rs4646903 polymorphisms associated with laryngeal cancer susceptibility among Asian populations: a meta-analysis

Many studies have investigated the association between CYP1A1 rs1048943 and rs4646903 polymorphisms and laryngeal cancer risk, but their results have been inconsistent. The PubMed and CNKI were searched for case–control studies published up to 01 July 2015. Data were extracted and pooled odds ratios (OR) with 95% confidence intervals (CI) were calculated. In this meta‐analysis, we assessed 10 published studies involving comprising 748 laryngeal cancer cases and 1558 controls of the association between CYP1A1 rs1048943 and rs4646903 polymorphisms and laryngeal cancer risk. For CYP1A1 rs1048943 of the homozygote G/G and G allele carriers (A/G + G/G) versus A/A, the pooled ORs were 1.77 (95% CI = 1.28–2.81, P = 0.007 for heterogeneity) and 1.86 (95% CI = 1.45–2.40, P = 0.000 for heterogeneity). For CYP1A1 rs4646903 of the homozygote G/G and G allele carriers (A/G + G/G) versus A/A, the pooled ORs were 1.53 (95% CI = 1.31–2.21, P = 0.012 for heterogeneity) and 1.33(95% CI = 1.04–1.71, P = 0.029 for heterogeneity). In the stratified analysis by ethnicity, the significantly risks were found among Asians for both the G allele carriers and homozygote G/G. However, no significant associations were found in Caucasian population all genetic models. These results from the meta‐analysis suggest that CYP1A1 rs1048943 and rs4646903 polymorphisms contribute to risk of laryngeal cancer among Asian populations.

Tobacco carcinogen-metabolizing genes CYP1A1, GSTM1, and GSTT1 polymorphisms and their interaction with tobacco exposure influence the risk of head and neck cancer in Northeast Indian population

Genetic polymorphisms in tobacco-metabolizing genes may modulate the risk of head and neck cancer (HNC). In Northeast India, head and neck cancers and tobacco consumption remains most prevalent. The aim of the study was to investigate the combined effect of cytochrome P450 1A1 (CYP1A1) T3801C, glutathione S-transferases (GSTs) genes polymorphisms and smoking and tobacco-betel quid chewing in the risk of HNC. The study included 420 subjects (180 cases and 240 controls) from Northeast Indian population. Polymorphisms of CYP1A1 T3801C and GST (M1 & T1) were studied by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) and multiplex PCR, respectively. Logistic regression (LR) and multifactor dimensionality reduction (MDR) approach were applied for statistical analysis. LR analysis revealed that subjects carrying CYP1A1 TC/CC + GSTM1 null genotypes had 3.52-fold (P < 0.001) increase the risk of head and neck squamous cell carcinoma (HNSCC). Smokers carrying CYP1A1 TC/CC + GSTM1 null and CYP1A1 TC/CC + GSTT1 null genotypes showed significant association with HNC risk (odds ratio [OR] = 6.42; P < 0.001 and 3.86; P = 0.005, respectively). Similarly, tobacco-betel quid chewers carrying CYP1A1 TC/CC + GSTM1 null genotypes also had several fold increased risk of HNC (P < 0.001). In MDR analysis, the best model for HNSCC risk was the four-factor model of tobacco-betel quid chewing, smoking, CYP1A1 TC/CC, and GSTM1 null genotypes (testing balance accuracy [TBA] = 0.6292; cross-validation consistency [CVC] = 9/10 and P < 0.0001). These findings suggest that interaction of combined genotypes of carcinogen-metabolizing genes with environmental factors might modulate susceptibility of HNC in Northeast Indian population.

Association of CYP1A1 and GSTM1 Polymorphisms With Oral Cancer Susceptibility: A Meta-Analysis

Our meta-analysis was aimed to evaluate the association of CYP1A1 and glutathione-S-transferase M1 (GSTM1) polymorphisms with oral cancer susceptibility.The related articles were searched in PubMed, Embase, and CNKI databases. Fifty eligible studies were included in our meta-analysis. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to evaluate the relationship of CYP1A1 (rs4646903 and rs1048943) and GSTM1 polymorphisms with oral cancer risk. A random-effects model or fixed-effects model was employed depending on the heterogeneity.In overall analysis, CYP1A1 rs4646903 polymorphism was associated with the risk of oral cancer (CC vs TT: OR 1.65, 95% CI 1.33-2.05; CC vs TC+TT: OR 1.77, 95% CI 1.48-2.11; C vs T: OR 1.17, 95% CI 1.07-1.28), whereas rs1048943 showed no obvious association with oral cancer susceptibility. Moreover, subgroup analysis by ethnicity demonstrated that rs4646903 and rs1048943 both related with increased risk of oral cancer in Asians. Moreover, the analysis based on source of control suggested that rs4646903 could increase the risk for oral cancer in both population- and hospital-based populations, whereas no remarkable relationship of rs1048943 with oral cancer susceptibility was observed. For GSTM1 gene, null genotype appeared to be a risk factor for oral cancer (null vs present: OR 1.23, 95% CI 1.12-1.34), which was also proved in the subgroup analysis.The results demonstrated that CYP1A1 rs4646903 and null genotype of GSTM1 polymorphisms might serve as risk factors for oral cancer.

GSTM1 null polymorphisms and oral cancer risk: a meta-analysis

Many studies have examined the association between the GSTM1 null gene polymorphism and oral cancer risk in various populations, but their results have been inconsistent. To assess this relationship more precisely, a meta-analysis was performed. The PubMed and Embase databases were searched for case-control studies published up to May 2013. Data were extracted and pooled odds ratio (OR) with 95% confidence intervals (CI) were calculated. Ultimately, 39 studies, comprising of 4,704 oral cancer cases and 7,090 controls, were included. Overall, for null versus present, the pooled OR was 1.29 (95% CI = 1.20-1.40), and the heterogeneity was found in all studies. In the stratified analysis by ethnicity, significant risks were found among Asians (OR = 1.39, 95% CI = 1.27-1.53; P = 0.000 for heterogeneity), but not in Caucasians (OR = 0.99, 95% CI = 0.83-1.18; P = 0.677 for heterogeneity). In conclusion, this meta-analysis demonstrates that the GSTM1 null gene polymorphism may be an increased risk of oral cancer in Asians but not in Caucasians.

Functional CYP1A1 genetic variants, alone and in combination with smoking, contribute to development of head and neck cancers

CYP1A1 plays an essential role in pathogenesis of head and neck cancers. Functional CYP1A1 Ile462Val and MspI single nucleotide polymorphisms (SNP) are considered to have significant effects on risk of head and neck cancers. Several case-control studies have examined how these genetic polymorphisms are involved in development of this group of malignancies, but the conclusions are inconsistent. Therefore, we conducted this meta-analysis to systematically examine the associations between these functional genetic variants and head and neck cancer risk. A total of 28 studies are eligible for CYP1A1 Ile462Val SNP (4639 patients and 4701 controls), and 22 studies for MspI SNP (4168 patients and 4638 controls). Pooled odds ratios (ORs) and the 95% confidence interval (95% CI) were appropriately calculated using either fixed-effect model or random-effect model. There was no association between Ile462Val polymorphism and head and neck cancer risk (OR = 1.23, 95% CI = 0.99-1.53, P = 0.062). However, in a stratified analysis, a statistically significant correlation between this SNP and pharyngeal cancer risk was observed (OR = 1.76, 95% CI = 1.32-2.33, P < 0.001). For MspI SNP, our data indicated that carriers of TC and CC genotypes had a 34% increased risk to develop head and neck cancers compared to TT carriers (95% CI = 1.15-1.57, P < 0.001). This effect was even more pronounced in smokers (OR = 2.98, 95% CI = 1.69-5.26, P < 0.001), demonstrating that gene-smoking interaction intensifying carcinogenesis may exist. These findings reveal that the functional CYP1A1 MspI genetic variant, alone and in combination with smoking, plays a more important role in pathogenesis of head and neck cancers.

Cathepsin B SNPs elevate the pathological development of oral cancer and raise the susceptibility to carcinogen-mediated oral cancer

Oral cancer is causally associated with environmental carcinogens, and the susceptibility to carcinogen-mediated tumorigenesis is proposed to be genotype-dependent. Cathepsin B (CTSB) is a lysosomal cysteine protease and may serve as a candidate biomarker of oral cancer. The current study aimed to explore the influences of three single nucleotide polymorphisms (SNPs) in CTSB gene, combined with environmental carcinogens on the risk and clinicopathological development of oral cancer. Three SNPs of CTSB, CTSB C76G (rs12338), CTSB A4383C (rs13332), and CTSB A8422G (rs8898), from 444 male patients with oral cancer and 426 control participants (males not diagnosed with cancer) in Taiwan were analyzed. These three CTSB SNPs all exhibited insignificant (P > 0.05) effects on the risk of oral cancer. However, the risk for developing the poor clinical stage of moderately or poorly differentiated cells was significantly (P < 0.001) increased to 3.325-fold in patients with oral cancer carrying the polymorphic genotype of rs8898 compared to patients with the ancestral genotype. Additionally, while considering the exposure of environmental carcinogens, the presence of these three CTSB SNPs, combined with betel quid chewing [adjusted odds ratio (AOR) was 36.570, 21.772, and 43.962 for rs12338, rs13332, and rs8898, respectively] and/or tobacco use (AOR was 3.794, and 8.972 for rs12338 and rs13332, respectively), robustly elevated the susceptibility to oral cancer. These results suggest that the genetic polymorphism of CTSB A8422G (rs8898) was associated with a high risk for the clinicopathological development of oral cancer and CTSB gene polymorphisms may increase the susceptibility to environmental carcinogens-mediated oral cancer.

Impact of interleukin-8 gene polymorphisms and environmental factors on oral cancer susceptibility in Taiwan

OBJECTIVES

Interleukin-8 (IL-8), which is an angiogenic chemokine with a high expression level in tumor tissues, plays important roles in developing many human malignancies including oral squamous cell carcinoma (OSCC). This study was designed to examine the association of IL-8 gene polymorphisms with the susceptibility and clinicopathological characteristics of OSCC.

METHODS

A total of 270 patients with OSCC and 350 healthy control subjects were recruited. Four single nucleotide polymorphisms (SNPs) of IL-8 genes were analyzed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) genotyping analysis.

RESULTS

Results showed that four IL-8 SNPs (-251 T/A, +781 C/T, +1633 C/T, and +2767 A/T) were not associated with oral cancer susceptibility as well as clinicopathological parameters. But among 345 smokers, IL-8 polymorphisms carriers with betel quid chewing were found to have a 17.41- to 23.14-fold risk to have oral cancer compared to IL-8 wild-type carriers without betel quid chewing. Among 262 betel quid chewers, IL-8 polymorphisms carriers with smoking have a 10.54- to 20.44-fold risk to have oral cancer compared to those who carried wild type without smoking.

CONCLUSIONS

Our results suggest that the combination of IL-8 gene polymorphisms and environmental carcinogens might be highly related to the risk of oral cancer.

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

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

Interactions among genetic variants in tobacco metabolizing genes and smoking are associated with head and neck cancer susceptibility in North Indians

It is becoming clearly evident that single gene or single environmental factor cannot explain susceptibility to diseases with complex etiology such as head and neck cancer. In this study, we applied the multifactor dimensionality reduction method to explore potential gene-environment and gene-gene interactions that may contribute to predisposition to head and neck cancer in the North Indian population. We genotyped 203 patients with head and neck cancer and 201 healthy controls for 13 functional polymorphisms in genes coding for tobacco metabolizing enzymes; CYP1A1, CYP2A13, GSTM1, and UGT1A7 using polymerase chain reaction-restriction fragment length polymorphism method, real-time polymerase chain reaction quantitative assay, and denaturing high-performance liquid chromatography followed by direct sequencing. We found that GSTM1 copy number variations were the most influential factor for head and neck cancer. We also observed significant gene-gene interactions among GSTM1 copy number variants, CYP1A1 T3801C and UGT1A7 T622C variants among smokers. Multifactor dimensionality reduction approach showed that the three-factor model, including smoking status, CYP1A1 T3801C, and GSTM1 copy number variants, conferred more than fourfold increased risk of head and neck cancer (odds ratio 4.89; 95% confidence interval: 3.15-7.32, p < 0.01). These results support the hypothesis that genetic variants in tobacco metabolizing genes may contribute to head and neck cancer risk through gene-gene and gene-environmental interactions.

Glutathione S-transferase M1 (GSTM1) and glutathione S-transferase T1 (GSTT1) null polymorphisms, smoking, and their interaction in oral cancer: a HuGE review and meta-analysis

The association between glutathione S-transferase M1 (GSTM1) and glutathione S-transferase T1 (GSTT1) null polymorphisms and oral cancer is not consistent across studies, and data on their interaction with smoking in oral cancer are lacking. The authors systematically searched PubMed and SciVerse Scopus for case-control studies examining the association between null genotypes of the GSTM1 and GSTT1 genes and oral cancer. Twenty-eight case-control studies published in English were identified. Summary odds ratios were derived via random-effects models. The summary odds ratio for the GSTM1 null genotype was 1.43 in Asians (95% confidence interval (CI): 1.14, 1.78; P < 0.01, I (2) = 73%) and 0.98 in Caucasians (95% CI: 0.76, 1.28; P = 0.91, I (2) = 0%). Case-only analysis of 6 studies (552 cases) showed an inverse multiplicative interaction between GSTM1 null polymorphisms and smoking (ever/high levels of smoking vs. never/low levels) (odds ratio (OR) = 0.51, 95% CI: 0.32, 0.82; P = 0.01, I (2) = 34%). The GSTT1 null genotype was not significantly associated with oral cancer in Asians (OR = 1.07, 95% CI: 0.82, 1.38; P = 0.63, I (2) = 65%) or Caucasians (OR = 1.04, 95% CI: 0.41, 2.65; P = 0.93, I (2) = 55%). In conclusion, the GSTM1 null genotype may be associated with a higher risk of oral cancer in Asians but not in Caucasians, and this effect may be modified by smoking status. The GSTT1 null genotype may not be associated with oral cancer.

Impact of uPA system gene polymorphisms on the susceptibility of environmental factors to carcinogenesis and the development of clinicopathology of oral cancer

BACKGROUND

The levels of urokinase plasminogen activator (uPA) system in tumor tissues are implicated as prognostic biomarkers in a wide range of malignancies. However, their possible impact on the risk and prognosis of oral cancer and the susceptibility of environmental carcinogens to oral cancer remains poorly investigated.

METHODS

The genetic polymorphisms of uPA, uPA receptor (uPAR), and plasminogen activator inhibitor (PAI)-1 were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 253 patients with oral cancer and 344 healthy controls.

RESULTS

There was no significant effect of uPA system genes on the susceptibility of oral cancer; however, the impact of uPA system gene polymorphisms on the susceptibility of betel nut and tobacco consumptions to oral cancer was revealed, except for that of uPAR gene polymorphism on tobacco consumption. Patients with oral cancer with at least one 5G allele of PAI-1 gene have a low risk for the development of clinical stage III or IV (p ≤ 0.05) and lymph node metastasis (p ≤ 0.05) compared with those with 4G/4G homozygotes.

CONCLUSIONS

Our results suggest that the combination of uPA system gene polymorphisms and environmental carcinogens was related to the risk of oral cancer, and the genetic polymorphism of PAI-1 was associated with a low risk to the clinicopathological development of oral cancer.