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

Interaction of cytochrome P450s with environmental risk factors increases their expression and risk to head and neck cancer

To investigate the role of interaction of tobacco metabolizing polymorphic cytochrome P450s (CYPs) and glutathione S-transferase M1 (GSTM1) with environmental risk factors in modifying the susceptibility to head and neck squamous cell carcinoma (HNSCC), a case-control study with 1250 proven cases of HNSCC and equal number of healthy controls was planned. A small but significant increase in the risk to HNSCC (1-2 fold) in the cases with variant genotypes of CYPs (1A1 or 1B1 or 2E1) increased several folds (up to 13 fold) in regular tobacco or alcohol users. This several fold increase in risk could be due to more than multiplicative interaction observed between the risk genotypes of CYPs and tobacco or alcohol. A synergistic effect was also observed between tobacco as well as alcohol users among cases with risk genotypes of CYPs and GSTM1 that resulted in a further increase in risk (up to 29 fold) to HNSCC. Interestingly, the increase in the risk in tobacco users among cases with variant genotypes of CYPs or a combination of CYPs & GSTM1 (-) was associated with a higher mRNA expression of CYPs when compared to nontobacco users in controls with wild type of genotypes of CYPs & GSTM1. The data suggest that the interaction of genetic and environmental risk factors leads to increased expression of CYPs which may increase the levels of tobacco-derived carcinogens thereby modifying the risk to HNSCC.

Familial cancer risk in family members and spouses of patients with early-onset head and neck cancer

BACKGROUND

Reported patterns of familial aggregation of head and neck cancer (HNC) vary greatly, with many studies hampered by the limited number of subjects.

METHODS

Altogether 923 early-onset (≤40 years old) HNC probands, their first-degree relatives, spouses, and siblings' offspring were ascertained. Cumulative risk and standardized incidence ratios (SIRs) were estimated.

RESULTS

Of all early-onset HNC families, only 21 (2.3%) had familial HNC cancers at any age and less than five familial early onset HNC cancers among first-degree relatives. The cumulative risk of HNC for siblings by age 60 (0.52%) was at population level (0.33%). No increased familial risk of early-onset HNC could be discerned in family members (SIR 2.68, 95% CI 0.32-9.68 for first-degree relatives).

CONCLUSIONS

Our study indicates that the cumulative and relative familial risk of early-onset HNC is modest in the Finnish population and, at most, only a minor proportion of early-onset HNCs are due solely to inherited genetic mutations.

New insights of CYP1A in endogenous metabolism: a focus on single nucleotide polymorphisms and diseases

Cytochrome P450 1A (CYP1A), one of the major CYP subfamily in humans, not only metabolizes xenobiotics including clinical drugs and pollutants in the environment, but also mediates the biotransformation of important endogenous substances. In particular, some single nucleotide polymorphisms (SNPs) for CYP1A genes may affect the metabolic ability of endogenous substances, leading to some physiological or pathological changes in humans. This review first summarizes the metabolism of endogenous substances by CYP1A, and then introduces the research progress of CYP1A SNPs, especially the research related to human diseases. Finally, the relationship between SNPs and diseases is discussed. In addition, potential animal models for CYP1A gene editing are summarized. In conclusion, CYP1A plays an important role in maintaining the health in the body.

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.

Role of CYP1A1, ABCG2, CYP24A1 and VDR gene polymorphisms on the evaluation of cardiac iron overload in thalassaemia patients

OBJECTIVES

Iron-burden-induced arrhythmia and heart failure are among the leading causes of morbidity and mortality in β-thalassaemia major patients. T2* cardiac magnetic resonance remains the only reliable noninvasive method for the heart iron excess assessment. We explored the role of single nucleotide polymorphisms involved in vitamin D metabolism, transport and activity and in deferasirox (DFX) metabolism on cardiac iron burden.

PATIENTS AND METHODS

One hundred and five β-thalassaemia patients, treated with DFX, were enrolled in the present study. Drug plasma Ctrough was measured by a high-performance liquid chromatography-ultraviolet method. Allelic discrimination was carried out using the real-time PCR.

RESULTS

CYP1A1*1189 CC, ABCG2 421 GA, CYP24A1 8620 GG and VDR TaqI CC single nucleotide polymorphisms influenced T2* values. Age, serum ferritin, ABCG2 421 GA, ABCG2 1194 +928 TC/CC, CYP24A1 22776 TT and VDR TaqI TC/CC were retained in linear regression model.

CONCLUSION

Our results suggested, for the first time, the role of DFX and vitamin D pharmacogenetics on cardiac iron overload.

A novel NOTCH3 mutation identified in patients with oral cancer by whole exome sequencing

Oral cancer is a serious disease caused by environmental factors and/or susceptible genes. In the present study, in order to identify useful genetic biomarkers for cancer prediction and prevention, and for personalized treatment, we detected somatic mutations in 5 pairs of oral cancer tissues and blood samples using whole exome sequencing (WES). Finally, we confirmed a novel nonsense single-nucleotide polymorphism (SNP; chr19:15288426A>C) in the NOTCH3 gene with sanger sequencing, which resulted in a N1438T mutation in the protein sequence. Using multiple in silico analyses, this variant was found to mildly damaging effects on the NOTCH3 gene, which was supported by the results from analyses using PANTHER, SNAP and SNPs&GO. However, further analysis using Mutation Taster revealed that this SNP had a probability of 0.9997 to be 'disease causing'. In addition, we performed 3D structure simulation analysis and the results suggested that this variant had little effect on the solubility and hydrophobicity of the protein and thus on its function; however, it decreased the stability of the protein by increasing the total energy following minimization (-1,051.39 kcal/mol for the mutant and -1,229.84 kcal/mol for the native) and decreasing one stabilizing residue of the protein. Less stability of the N1438T mutant was also supported by analysis using I-Mutant with a DDG value of -1.67. Overall, the present study identified and confirmed a novel mutation in the NOTCH3 gene, which may decrease the stability of NOTCH3, and may thus prove to be helpful in cancer prognosis.

Oral cancer: Deregulated molecular events and their use as biomarkers

Oral Cancer (OC) is a subset of head and neck cancer (HNC) with an annual worldwide incidence of 275,000 cases. OC remains a significant burden worldwide in terms of diagnosis, treatment and prognosis. Despite desirable outcomes in early diagnosed OCs and treatment advances most OCs are detected in advanced stages. The 5-year survival rate of early-stage disease is ∼80% and that of late-stage disease is only ∼20%. Recurrence and chemoresistance from a treatment point of view and pain and disfiguration are important factors contributing to the high morbidity and mortality of OC. Furthermore the process of oral carcinogenesis is complex and not yet fully understood. Consequently numerous potential biomarkers have been hypothesised though controversial results across the board hamper their clinical implementation. Of greatest advantage would be biomarkers signalling early events preceeding OC. Biomarker targets predominately involve deregulated molecular events that participate in cell signalling, growth, survival, motility, angiogenesis and cell cycle control but can also use changes in metabolic genes to discriminate healthy form disease state. Promising potential biomarkers include the growth signalling oncogenes, Epidermal Growth Factor Receptor and Cyclin D1, the anti-growth signalling components p53 and p21, apoptotic effectors such as Bcl-2 and also components involved in immortalisation, angiogenesis, invasion and metastasis processes. Translation of these potential biomakers to the patients is closer than ever though few issues remain to be resolved. Firstly large clinical trials are needed to validate their clinical applicability but also standardised methods of collection, storage and processing methods are needed to minimise variability.

Epistasis Test in Meta-Analysis: A Multi-Parameter Markov Chain Monte Carlo Model for Consistency of Evidence

Conventional genome-wide association studies (GWAS) have been proven to be a successful strategy for identifying genetic variants associated with complex human traits. However, there is still a large heritability gap between GWAS and transitional family studies. The "missing heritability" has been suggested to be due to lack of studies focused on epistasis, also called gene-gene interactions, because individual trials have often had insufficient sample size. Meta-analysis is a common method for increasing statistical power. However, sufficient detailed information is difficult to obtain. A previous study employed a meta-regression-based method to detect epistasis, but it faced the challenge of inconsistent estimates. Here, we describe a Markov chain Monte Carlo-based method, called "Epistasis Test in Meta-Analysis" (ETMA), which uses genotype summary data to obtain consistent estimates of epistasis effects in meta-analysis. We defined a series of conditions to generate simulation data and tested the power and type I error rates in ETMA, individual data analysis and conventional meta-regression-based method. ETMA not only successfully facilitated consistency of evidence but also yielded acceptable type I error and higher power than conventional meta-regression. We applied ETMA to three real meta-analysis data sets. We found significant gene-gene interactions in the renin-angiotensin system and the polycyclic aromatic hydrocarbon metabolism pathway, with strong supporting evidence. In addition, glutathione S-transferase (GST) mu 1 and theta 1 were confirmed to exert independent effects on cancer. We concluded that the application of ETMA to real meta-analysis data was successful. Finally, we developed an R package, etma, for the detection of epistasis in meta-analysis [etma is available via the Comprehensive R Archive Network (CRAN) at https://cran.r-project.org/web/packages/etma/index.html].

Association between an insertion/deletion polymorphism in IL-1A gene and cancer risk: a meta-analysis

Purpose

Previous studies have reported the association of an insertion/deletion (Ins/Del) polymorphism (rs3783553) in the 3′ untranslated region of interleukin-1A (IL-1A) with the risk of cancer, such as oral squamous cell carcinoma, nasopharyngeal carcinoma, and cervical carcinoma. However, the results are still inconsistent. The present meta-analysis aimed to clarify the association of IL-1A rs3783553 polymorphism with cancer risk.

Methods

All eligible studies were selected from PubMed, Web of Science, and Chinese National Knowledge Infrastructure up to September 2, 2015. Summary odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate cancer risk.

Results

A total of ten case–control studies with 4,514 cases and 6,689 controls were included this meta-analysis. We found that IL-1A rs3783553 polymorphism was significantly associated with cancer risk (Ins/Ins + Ins/Del vs Del/Del: OR =0.79, 95% CI =0.67–0.92; Ins/Ins vs Del/Del: OR =0.61, 95% CI =0.47–0.79; Ins/Ins vs Ins/Del + Del/Del: OR =0.67, 95% CI =0.55–0.83; Ins vs Del: OR =0.81, 95% CI =0.72–0.92). In the stratified analyses, significant effects were found among Asian populations (Ins/Ins + Ins/Del vs Del/Del: OR =0.81, 95% CI =0.69–0.95) and cervical carcinoma (Ins/Ins vs Del/Del: OR =0.51, 95% CI =0.34–0.76; Ins/Ins vs Ins/Del + Del/Del: OR =0.52, 95% CI =0.35–0.78).

Conclusion

Our meta-analysis suggests that the IL-1A rs3783553 polymorphism contributes to susceptibility to cancer. However, well-designed studies with larger sample sizes are required to verify the results.