Association of the MTHFR C677T polymorphism with primary brain tumor risk

MTHFR C677T and A1298C Polymorphisms in Breast Cancer, Gliomas and Gastric Cancer: A Review

Folate (vitamin B9) is found in some water-soluble foods or as a synthetic form of folic acid and is involved in many essential biochemical processes. Dietary folate is converted into tetrahydrofolate, a vital methyl donor for most methylation reactions, including DNA methylation. 5,10-methylene tetrahydrofolate reductase (MTHFR) is a critical enzyme in the folate metabolism pathway that converts 5,10-methylenetetrahydrofolate into 5-methyltetrahydrofolate, which produces a methyl donor for the remethylation of homocysteine to methionine. MTHFR polymorphisms result in reduced enzyme activity and altered levels of DNA methylation and synthesis. MTHFR polymorphisms have been linked to increased risks of several pathologies, including cancer. Breast cancer, gliomas and gastric cancer are highly heterogeneous and aggressive diseases associated with high mortality rates. The impact of MTHFR polymorphisms on these tumors remains controversial in the literature. This review discusses the relationship between the MTHFR C677T and A1298C polymorphisms and the increased risk of breast cancer, gliomas, and gastric cancer. Additionally, we highlight the relevance of ethnic and dietary aspects of population-based studies and histological stratification of highly heterogeneous tumors. Finally, this review discusses these aspects as potential factors responsible for the controversial literature concerning MTHFR polymorphisms.

Association between miRNA polymorphisms and susceptibility to brain tumors: A meta-analysis

BACKGROUND

Previous studies have demonstrated that single-nucleotide polymorphisms (SNPs) in miRNAs are related to the susceptibility to brain tumors, but the conclusions remain controversial. This study was to perform a meta-analysis to re-assess the associations between miRNA SNPs and brain tumor risk.

METHODS

Relevant studies were identified in the databases of PubMed and the Cochrane Library databases. Pooled odds ratio (OR) and 95% confidence interval (95% CI) were calculated to assess the relationships between SNPs and the risk of brain tumors under various genetic models by the STATA software.

RESULTS

Five studies, containing 2275 cases, and 2323 controls, were included, 4 of which evaluated miR-196a2 (rs11614913), 3 for miR-146a (rs2910164) and 2 for miR-499 (rs3746444) and miR-149 (rs2292832), respectively. The meta-analysis indicated that the GG genotype carriers of miR-146a were more susceptible to brain tumors compared with GC genotype carriers (OR = 1.19, 95%CI = 1.01-1.41, P = .036). No significant associations were observed between the SNPs of other miRNAs and the risk of brain tumors. Furthermore, all miRNA polymorphisms did not show significant associations with the risk of glioma subgroup in any genetic models, while meta-analysis of non-glioma subgroup could not be performed due to low statistical power and analysis of only 1 study.

CONCLUSION

Our study suggests that miR-146a polymorphism may modify the risk for brain tumors, but which type (glioma or benign non-glioma tumors) should be verified with large sample size.

Folate and Its Impact on Cancer Risk

PURPOSE OF REVIEW

Research has evaluated the potential impact of folate on cancer risk with conflicting findings. Studies have demonstrated increased risk, no effect, and decreased risk. This review summarizes findings of mixed results between folate intake, serum levels, gene polymorphisms, and cancer risk based on meta-analyses from the past five years.

RECENT FINDING

Low or deficient folate status is associated with increased risk of many cancers. Folic acid supplementation and higher serum levels are associated with increased risk of prostate cancer. Gene polymorphisms may impact risk in certain ethnic groups. Folate has been studied extensively due to its role in methylation and nucleotide synthesis. Further prospective studies are needed to clarify optimal levels for nutrient remediation and risk reduction in those at risk, as well as elucidate the association between high intake, high serum levels, and prostate cancer risk. Future considerations for cancer risk may include gene interactions with nutrients and environmental factors.

Association of Single Nucleotide Polymorphisms (SNPs) in Genes Encoding for Folate Metabolising Enzymes with Glioma and Meningioma in Indian Population

Background:

The association of primary brain tumors with Single Nucleotide polymorphisms (SNPs) in genes of folate metabolising enzymes have been reported to vary among different ethnic population. Here, we have studied the association of SNPs of folate metabolizing genes with the primary brain tumors (glioma and meningioma) in North Indian population.

Methods:

SNPs of genes coding for folate metabolizing enzymes was carried out in 288 study population from North India [Glioma (n=108), Meningioma (n=76) and healthy-control (n=104)]. The allele-specific polymerase chain reaction (ARMS-PCR) was used to analyse the SNP A1298C of the MTHFR (Methylenetetrahydrofolate-reductase) and the SNP A66G of the methionine synthase reductase (MTRR) genes. The PCR-RLFP (Restriction Fragment Length Polymorphism) was used to analyse the SNP C677T of the Methylene tetrahydrofolate-reductase and the SNP A2756G of the methionine-synthase (MTR) genes. Serum homocysteine, vitamin B₁₂ and folate levels were evaluated in controls/patients serum using Chemiluminescence immunoassay and the levels were correlated with SNPs genotype.

Results:

The CC genotype of MTHFR A1298C was observed to have reduced risk of having meningioma than AA genotype (odd ratio=0.62, 95%CI 0.32-0.97, p=0.03). Similarly, the AG genotype of MTRR A66G showed reduced risk of glioma than AA genotype (odd ratio=0.56, 95%CI 0.32-0.97, p=0.039). Furthermore, in patients with AA genotype of MTR A2756G and CT genotype of MTHFR C677T showed higher serum homocysteine level than GG genotype (8.6 µmol/L, p=0.048) and CC genotype (11.2µmol/L, p=0.039) respectively.

Conclusion:

Our findings provide an insight into the risk association of SNPs in MTHFR A1298C and MTRR A66G genes with glioma/meningioma patients. Further studies are needed to evaluate their clinical implications.

Genetic variants and increased risk of meningioma: an updated meta-analysis

PURPOSE

Various genetic variants have been reported to be linked to an increased risk of meningioma. However, no confirmed conclusion has been obtained. The purpose of the study was to investigate potential meningioma-associated gene polymorphisms, based on published evidence.

MATERIALS AND METHODS

An updated meta-analysis was performed in September 2016. After electronic database searching and study screening, we selected eligible case-control studies and extracted data for meta-analysis, using Mantel-Haenszel statistics. P-values, pooled odds ratios (ORs), and 95% confidence intervals were calculated.

RESULTS

We finally selected eight genes with ten polymorphisms: MLLT10 rs12770228, CASP8 rs1045485, XRCC1 rs1799782, rs25487, MTHFR rs1801133, rs1801131, MTRR rs1801394, MTR rs1805087, GSTM1 null/present, and GSTT1 null/present. Results of meta-analyses showed that there was increased meningioma risk in case groups under all models of MLLT10 rs12770228 (all OR >1, P<0.001), compared with control groups. Similar results were observed under the allele, homozygote, dominant, and recessive models of MTRR rs1801394 (all OR >1, P<0.05), and the heterozygote and dominant models of MTHFR rs1801131 in the Caucasian population (all OR >1, P<0.05). However, no significantly increased meningioma risks were observed for CASP8 rs1045485, XRCC1 rs25487, rs1799782, MTHFR rs1801133, MTR rs1805087, or GSTM1/GSTT1 null mutations.

CONCLUSION

Our updated meta-analysis provided statistical evidence for the role of MLLT10 rs12770228, MTRR rs1801394, and MTHFR rs1801131 in increased susceptibility to meningioma.

Adult brain cancer in the U.S. black population: a Surveillance, Epidemiology, and End Results (SEER) analysis of incidence, survival, and trends

Background

Despite much epidemiological research on brain cancer in the United States, the etiology for the various subtypes remains elusive. The black population in the United States currently experiences lower incidence but higher survival rates when compared to other races. Thus, the aim of this study is to analyze the trends in incidence and survival for the 6 most common primary brain tumors in the black population of the United States.

Material/Methods

The Surveillance, Epidemiology, and End Results (SEER) database was utilized in this study to analyze the incidence and survival rates for the 6 most common brain tumor subtypes. Joinpoint 3.5.2 software was used to analyze trends in the incidence of diagnosis from 1973 to 2008. A Kaplan-Meier curve was generated to analyze mean time to death and survival at 60 months.

Results

Joinpoint analysis revealed that per year the incidence of brain cancer in the U.S. black population increased by 0.11 between 1973 and 1989. After this period, a moderate decrease by 0.06 per annum was observed from 1989 to 2008. Lymphoma was the most common primary tumor subtype for black individuals ages 20–34, and glioblastoma was identified as the most common tumor subtype for black individuals in the age groups of 35–49, 50–64, 65–79, and 80+.

Conclusions

This population-based retrospective study of brain cancer in black adults in the United States revealed significant sex and age differences in the incidence of the 6 most common brain tumor subtypes from 1973 to 2008.

Reproductive factors in relation to risk of brain tumors in women: an updated meta-analysis of 27 independent studies

Previous studies on the association between reproductive factors and brain tumor risk in women have provided inconclusive findings. Thus, an updated meta-analysis was performed to obtain more precise risk estimates for brain tumor regarding several common reproductive factors. A comprehensive literature search for relevant publications in the PubMed and Embase databases was carried out from their inception up to June 20, 2014. Pooled relative risks (RRs) with corresponding 95% confidence intervals (CIs) were calculated. There were 27 independent studies with a total of 12,129 cases and 1,433,915 controls included into the present meta-analysis. We found that an elevated risk of brain tumors (RR=1.17, 95% CI 1.06-1.29, P=0.002), particularly glioma (RR=1.33, 95% CI 1.15-1.54, P<0.001), was related to older age at menarche. Interestingly, stratified analysis by type of brain tumors showed that the longer duration of breast feeding was associated with the risk of meningioma negatively but glioma positively (for meningioma: RR=0.76, 95% CI 0.64-0.91, P=0.002; for glioma: RR=1.70, 95% CI 1.14-2.55, P=0.010). No significant association was observed when estimating the roles of other reproductive factors including parity, age at first birth, menopausal status, and age at menopause in brain tumorigenesis. Our study suggests that older age at menarche is a risk factor of brain tumors and glioma in particular. Additionally, more studies are warranted to further elucidate roles and mechanisms of common reproductive factors in the risk of brain tumors.

Association between telomerase reverse transcriptase rs2736100 polymorphism and risk of glioma

BACKGROUND

Epidemiological studies have been conducted to investigate the association of telomerase reverse transcriptase (TERT) rs2736100 polymorphism with glioma risk. The aim of the present study was to evaluate the association of TERT rs2736100 polymorphism with glioma risk using a meta-analysis approach.

MATERIALS AND METHODS

All eligible studies were identified through a search of PubMed, EMBASE, China National Knowledge Infrastructure, Database of Chinese Scientific and Technical Periodicals, and China Biology Medical literature database before January 2014. The association between the TERT rs2736100 polymorphism and glioma risk was estimated by odds ratio (OR) and 95% confidence interval (CI).

RESULTS

A total of nine case-control studies including 9411 cases and 13,708 controls were eventually collected. Overall, we found that TERT rs2736100 polymorphism was significantly associated with the risk of glioma (OR = 1.29, 95% CI 1.24-1.34, P < 0.001). In the subgroup analysis based on ethnicity, the significant association was found in Caucasians (OR = 1.29, 95% CI 1.24-1.34, P < 0.001). In subgroup analyses by histology, the associations were significant in glioblastoma (OR = 1.45, 95% CI 1.32-1.60, P < 0.001), astrocytoma (OR = 1.41, 95% CI 1.26-1.58, P < 0.001), and oligodendroglioma (OR = 1.20, 95% CI 1.05-1.37, P = 0.008).

CONCLUSIONS

Taken together, these data suggested that TERT rs2736100 polymorphism may contribute to glioma susceptibility.

Association of methionine synthase rs1801394 and methionine synthase reductase rs1805087 polymorphisms with meningioma in adults: A meta-analysis

Several epidemiological studies suggested that methionine synthase (MTRR) rs1801394 and methionine synthase reductase (MTR) rs1805087 polymorphisms may be involved in the risk of meningioma in adults; however, the results from different case-control studies have been inconsistent. Therefore, we performed a meta-analysis to investigate the association of MTRR and MTR polymorphisms with meningioma. PubMed, Web of Knowledge, China National Knowledge Infrastructure and Wanfang databases were searched up to October 30, 2013 and 3 publications, involving 7 case-control studies, were finally included. Following data extraction, a meta-analysis was conducted using Stata 12.0 software. The pooled results based on the fixed effects model demonstrated that the MTRR rs1801394 polymorphism was associated with an increased risk of meningioma [odds ratio (OR)=1.18, 95% confidence interval (CI): 1.05–1.32 for G vs. A; OR=1.41, 95% CI: 1.12–1.77 for GG vs. AA; OR=1.08, 95% CI: 0.94–1.33 for AG vs. AA; OR=1.19, 95% CI: 1.01–1.40 for (AG+GG) vs. AA; and OR=1.32, 95% CI: 1.07–1.63 for GG vs. (AG+AA)]; however, an association between the MTR rs1805087 polymorphism and the risk of meningioma was not identified [OR=0.99, 95% CI: 0.88–1.12 for G vs. A; OR=1.09, 95% CI: 0.80–1.48 for GG vs. AA; OR=0.95, 95% CI: 0.82–1.11 for AG vs. AA; OR=0.97, 95% CI: 0.84–1.13 for (AG+GG) vs. AA; and OR=1.09, 95% CI: 0.80–1.48 for GG vs. (AG+AA)]. Therefore, the currently available evidence suggests that the MTRR rs1801394 polymorphism may increase the risk of meningioma, whereas the MTRR rs1801394 polymorphism is not associated with meningioma.