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

Elevated exposure to polycyclic aromatic hydrocarbons (PAHs) may trigger cancers in Pakistan: an environmental, occupational, and genetic perspective

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic compounds which are emitted through incomplete combustion of organic materials, fossil fuels, consumption of processed meat, smoked food, and from various industrial activities. High molecular mass and mobility make PAHs widespread and lethal for human health. A cellular system in human detoxifies these toxicants through specialized enzymatic machinery called xenobiotic-metabolizing (CYP450) and phase-II (GSTs) enzymes (XMEs). These metabolizing enzymes include cytochromes P450 family (CYP1, CYP2), glutathione s-transferases, and ALDHs. Gene polymorphisms in XMEs encoding genes can compromise their metabolizing capacity to detoxify ingested carcinogens (PAHs etc.) that may lead to prolong and elevated exposure to ingested toxicants and may consequently lead to cancer. Moreover, PAHs can induce cancer through reprograming XMEs' gene functions by altering their epigenetic markers. This review article discusses possible interplay between individual's gene polymorphism in XMEs' genes, their altered epigenetic markers, and exposure to PAHs in cancer susceptibility in Pakistan.

Association of Glutathione-S-Transferases M1 and T1 Deletional Variants with Development of Oral Squamous Cell Carcinoma: A Study in the South-East of Iran

Background:

The role of genetic polymorphisms in genes of Glutathione-S-transferases (GST) enzymes in susceptibility to oral cavity cancers is controversial. Oral Squamous Cell Carcinoma (OSCC) is the most common oral cavity neoplasm. Aimed to evaluate the potential impacts of two well-known null variants residing in the gene encoding GSTM1 and GSTT1 enzymes of OSCC patients in the southeast of Iran.

Methods:

In a case-control design, 113 individuals (50 OSCC patients, and 63 healthy subjects) were included. DNA was extracted using paraffin-embedded tissues. GST genotyping was carried out using multiplex PCR.

Results:

In 113 participants, 41 (36.3%) and 72 (63.7%) were males and females respectively. No significant difference was recognized for distribution of GSTM1 (P=0.11) and GSTT1 (P=0.28) null genotypes between OSCC patients (58%, and 24% respectively) and healthy controls (42.9% and 15.9% respectively). Also, no significant difference was noted regarding the frequency of GSTM1 null genotype in different histological grades, however, those patients with more aggressive disease (poorly differentiated or grade III) revealed with a significantly higher ratio (66.7%) of GSTT1 null genotype (P=0.002). The highest odds ratio for OSCC was related to combined null genotypes for GSTM1 and GSTT1 (OR=2.5, 95% CI: 0.7-9.2), however, this was not statistically significant finding (P=0.15).

Conclusion:

Null genotypes polymorphisms were more common in OSCC than healthy individuals. GSTT1 null genotype may be an important genetic factor in the progression of OSCC.

Preliminary Study of the GSTM1 Null Polymorphism and History of Tobacco Smoking among Oral Cancer Patients in Northeastern Thailand

Risks with GSTM1 genotypes and potential roles of smoking in the susceptibility to oral squamous cell carcinoma (OSCC) were studied in Northeastern Thailand. Study subjects were 79 histologically-confirmed OSCC cases (31 men, 48 women) and 79 age- and sex-matched healthy controls ranging in age from 25 to 84 years. GSTM1 genotyping was achieved by two independent PCR assays. The GSTM1 null allele and the homozygous genotype did not increase risk of OSCC vs the wild type allele and the remaining genotypes. When the focus was on the smoking habit, male subjects who smoked ≥10 or ≥35 years were at significantly increased risk for OSCC with adjusted ORs of 4.88 [95%CI, 1.41-16.87, p=0.012] or 4.94 [95%CI, 1.62-15.12, p=0.005], respectively. A higher risk for OSCC was found for smoking amount; those who smoked >5 or >10 pack-years were at a higher risk with adjusted OR of 4.46 [95%CI; 1.45-13.74, p=0.009] or 3.89 [95%CI; 1.34-11.28, p=0.012], respectively. There are certain smoking patterns that give greater risks and thus both smoking duration and pack-years should be taken into consideration in tobacco related cancer prevention.

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.

Prevalence of glutathione S-transferase M1 null polymorphism in tobacco users, oral leukoplakia and oral squamous cell carcinoma patients in South Indian population: A polymerase chain reaction study

Context:

Tobacco abuse is a well-known risk factor for potentially malignant disorders as well as oral squamous cell carcinoma (SCC). Factors that influence tobacco-exposed individuals developing a malignancy may include a combination of total tobacco exposure and genetic susceptibility.

Aim:

This study was undertaken to determine the prevalence of the glutathione S-transferase M1 (GSTM1) null polymorphism in oral leukoplakia and oral SCC patients in South Indian population.

Settings and Design:

This case-control study was conducted in hospital setting on South Indian population.

Materials and Methods:

Totally, 280 subjects with a history of tobacco use, oral leukoplakia, oral SCC were included in this study. Three milliliter of blood was collected and transported under cold cycle and taken for evaluation of GSTM1 null polymorphism using Multiplex Polymerase Chain Reaction.

Results and Discussion:

On comparing the prevalence of GSTM1 null polymorphism among the group with subjects with habits and no oral lesions, oral leukoplakia and oral SCC, it was observed that there was a statistically significant association between GSTM1 null polymorphism and the different groups (P < 0.01).

Conclusion:

The lack of GSTM1 activity would make the oral tissues more susceptible to action of tobacco carcinogens and to the development of a high-grade level of dysplasia in oral leukoplakia and thereby increases the susceptibility of lesion to undergo malignant changes.

Clinical application of genetics to guide prevention and treatment of oral diseases

Dental care costs in the United States exceed $100 billion annually. Personalized medicine efforts in dentistry are driven by potentially compelling clinical utility and cost-effectiveness prospects in the major diseases of periodontitis, caries, and oral cancers. This review discusses progress and challenges identifying genetic markers and showing clinical utility in dentistry. Genome-wide association studies (GWAS) of chronic periodontitis (CP) identified no significant variants, but CDKN2BAS variants on chromosome 9 were significantly associated with aggressive periodontitis. Stratifying patients by interleukin (IL)-1 gene variants, smoking and diabetes differentiated CP prevention outcomes. Dental caries' GWAS identified significant signals in LYZL2, AJAp1, and KPNA4; and efforts are ongoing to identify genetic factors for multiple caries phenotypes. Trials of molecularly targeted therapies are in progress for oral, head, and neck squamous cell carcinomas (OHNSCC) and results have been promising but limited in their effectiveness. Current opportunities and challenges for molecular targeting for OHNSCC are discussed.