Methylenetetrahydrofolate reductase polymorphisms modify BRCA1-associated breast and ovarian cancer risks

Methylenetetrahydrofolate reductase gene polymorphisms in the risk of polycystic ovary syndrome and ovarian cancer

Polymorphisms of methylenetetrahydrofolate reductase (MTHFR) in hormone metabolism pathways might cause metabolic disturbances and contribute to the development of polycystic ovary syndrome (PCOS) and ovarian cancer, but the published studies were inconsistent. The aim of the present study was to evaluate the MTHFR C677T (rs1801133) and A1298C (rs1801131) gene polymorphisms in the risk of PCOS and ovarian cancer by meta-analysis. A comprehensive electronic search was conducted in databases for studies published from 1995 to 2020. The pooled ORs were calculated by Revman 5.2 software. Twenty-nine articles including 45 case–control studies were included. We found that MTHFR C677T polymorphisms were correlated with elevated PCOS risk (TT vs. CT+CC: OR = 1.41, 95%CI = 1.20–1.67; TT+CT vs. CC: OR = 1.54, 95%CI = 1.07–2.22; CT vs. CC+TT: OR = 1.18, 95%CI 1.04–1.33; TT vs. CC: OR = 1.47, 95%CI = 1.03–2.11; T vs. C: OR = 1.25, 95%CI = 1.06–1.47), which were more obvious in Middle Eastern subgroup. MTHFR A1298C polymorphisms were also associated with overall PCOS susceptibility (CC vs. AC+AA: OR = 2.55, 95% CI = 1.61–4.03; CC+AC vs. AA: OR = 1.84, 95%CI = 1.04–3.28; CC vs. AA: OR = 2.66, 95%CI = 1.68–4.22; C vs. A: OR = 1.67, 95%CI = 1.03–2.71), which were mainly reflected in Asian subjects. For ovarian cancer, MTHFR C677T polymorphisms were only related with elevated ovarian cancer risk in Asian population, while no significant association was found for A1298C polymorphisms. This meta-analysis suggested that MTHFR C677T and MTHFR A1298C polymorphisms were correlated with elevated PCOS risk. MTHFR C667T only posed a higher risk for ovarian cancer in Asians instead of other populations, while MTHFR A1298C polymorphisms were not related to ovarian cancer risk. Further studies are needed to validate the conclusion.

Association of MTHFR 677C>T Polymorphism with Susceptibility to Ovarian and Cervical Cancers: A Systematic Review and Meta-Analysis

Background:

Previous studies have evaluated the impact of MTHFR 677C>T polymorphism on susceptibility to ovarian and cervical cancers in women, but the conclusions are still controversial. To get a more precise evaluation of the association between MTHFR 677C>T polymorphism and risk of ovarian and cervical cancers, we performed a meta-analysis of the association of all eligible studies.

Methods:

A comprehensive search performed in PubMed, Google Scholar, CNKI, and Web of Science databases to identify the relevant studies up to October 15, 2018. The strength of the association was estimated by odds ratios (OR) with 95% confidence interval (CI).

Results:

A total of 27 case-control studies including eleven studies with 4990 cases 7730 controls on ovarian cancer and 16 studies with 4990 cases and 7730 controls on cervical cancer were selected. Pooled data revealed that the MTHFR 677C>T polymorphism not significantly associated with an increased risk of ovarian and cervical cancers under all five genetic models. However, stratified analysis by ethnicity showed that the MTHFR 677C>T polymorphism was significantly associated with risk of ovarian cancer in Asians. No publication bias was found in the current meta-analysis.

Conclusions:

The results of this meta-analysis proposes that the MTHFR 677C>T polymorphism may not play a role in development of ovarian and cervical cancers in overall population. Further well-designed studies are necessary to clarify the precise role of the MTHFR 677C>T polymorphism on ovarian and cervical cancers risk.

Epigenetics of breast cancer: Modifying role of environmental and bioactive food compounds

SCOPE

Reduced expression of tumor suppressor genes (TSG) increases the susceptibility to breast cancer. However, only a small percentage of breast tumors is related to family history and mutational inactivation of TSG. Epigenetics refers to non-mutational events that alter gene expression. Endocrine disruptors found in foods and drinking water may disrupt epigenetically hormonal regulation and increase breast cancer risk. This review centers on the working hypothesis that agonists of the aromatic hydrocarbon receptor (AHR), bisphenol A (BPA), and arsenic compounds, induce in TSG epigenetic signatures that mirror those often seen in sporadic breast tumors. Conversely, it is hypothesized that bioactive food components that target epigenetic mechanisms protect against sporadic breast cancer induced by these disruptors.

METHODS AND RESULTS

This review highlights (i) overlaps between epigenetic signatures placed in TSG by AHR-ligands, BPA, and arsenic with epigenetic alterations associated with sporadic breast tumorigenesis; and (ii) potential opportunities for the prevention of sporadic breast cancer with food components that target the epigenetic machinery.

CONCLUSIONS

Characterizing the overlap between epigenetic signatures elicited in TSG by endocrine disruptors with those observed in sporadic breast tumors may afford new strategies for breast cancer prevention with specific bioactive food components or diet.

Investigation of Methylenetetrahydrofolate Reductase C677T Polymorphism and Human Papilloma Virus Genotypes in Iranian Breast Cancer

Breast cancer (BC) is the leading cause of death among Iranian women. Development of BC is a multistep process, arising from genetic changes such as methylenetetrahydrofolate reductase (MTHFR) polymorphism and infection with human papillomavirus (HPV). In this study, we investigated HPV genotypes associated with BCs and its relation with MTHFR C677T polymorphism for early detection of familial BCs. A total of 84 archival BC samples from Iran were collected. Verification of each cancer reported in a relative was sought through the pathology reports of the hospital records. Then, DNA was extracted from all samples by standard methods and HPV genotypes and MTHFR C677T polymorphism genotypes were analyzed using multiplex polymerase chain reaction (PCR) and amplification-refractory mutation system (ARMS)-PCR. Finally, data analysis was performed using version 7 of the Epi Info™ 2012 software and test chi-square (x2) for trend. The frequencies of the CC, TC, and TT genotypes of MTHFR (C677T) were 0.53, 0.38, and 0.09 in familial BC patients, and 0.46, 0.51, and 0.03, respectively, in nonfamilial BC patients. Furthermore, HPV DNA typing identified 29 infections and C677T TT genotype was significantly associated with an increased risk of familial BC in the study population. Our results demonstrate that infection with HPV was prevalent among Iranian women with familial BC. Finally, the testing of C677T GG genotype in combination with HPV genotyping as molecular markers can be helpful in the early diagnosis of Iranian familial BCs by PCR.

MTHFR C677T polymorphism and breast, ovarian cancer risk: a meta-analysis of 19,260 patients and 26,364 controls

Objective

Previous studies have found that many gene variations can be detected in both breast cancer and ovarian cancer, which is beneficial for the elaboration of the molecular origin of breast and ovarian cancer. Furthermore, many studies have explored the association of methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism with the risk of breast cancer and/or ovarian cancer; however, the results remained inconclusive. Therefore, this study conducted a systematic review and meta-analysis to evaluate the association between MTHFR C677T polymorphism and the risk of breast and ovarian cancer.

Materials and methods

A total of 50 studies with 19,260 cases and 26,364 controls including 39 studies for breast cancer and 8 studies for ovarian cancer were identified on searching through PubMed, Embase, Web of Science, China National Knowledge Infrastructure, WanFang, and Database of Chinese Scientific and Technical Periodicals (VIP). Allele model, dominant model, recessive model, homozygous model, and co-dominant model were applied to evaluate the association of MTHFR C677T polymorphism with breast cancer and/or ovarian cancer risk. Moreover, the odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to assess the strength of the association between MTHFR C677T polymorphism and breast and ovarian cancer risk.

Results

A significantly increased breast cancer risk was observed in the overall analysis (for C vs T, OR =1.19, CI: 1.12–1.28, P<0.05; for CC vs TT, OR =1.20, CI: 1.10–1.23, P<0.05; for (CT+CC) vs TT, OR =1.19, CI: 1.11–1.27, P<0.05; for CC vs (CT+TT), OR =1.19, CI: 1.79–1.95, P<0.05), while no significantly increased ovarian cancer risk was detected. In the subgroup analysis based on ethnicity, a significant association of breast cancer and/or ovarian cancer risk with MTHFR C677T polymorphism was observed in Asians. Interestingly, there was no significant association between MTHFR C677T polymorphism and ovarian cancer risk in Caucasians, whereas a significantly increased risk of breast cancer was found in Caucasians.

Conclusion

This meta-analysis demonstrates that MTHFR C677T polymorphism may be a risk factor for breast and ovarian cancer, especially in Asians.

Association of MTHFR (C677T) Gene Polymorphism With Breast Cancer in North India

BACKGROUND

Breast cancer is one of the most common malignancies in women and is associated with a variety of risk factors. The functional single-nucleotide polymorphism (SNP) C677T in the gene encoding 5,10-methylenetetrahydrofolate reductase (MTHFR) may lead to decreased enzyme activity and affect the chemosensitivity of tumor cells. This study was designed to investigate the association of MTHFR gene polymorphism (SNP) in the pathogenesis of breast cancer among the North Indian women population.

MATERIALS AND METHODS

Genotyping was performed by polymerase chain reaction (PCR) using genomic DNA, extracted from the peripheral blood of subjects with (275 cases) or without (275 controls) breast cancer. Restriction fragment length polymorphism was used to study C677T polymorphism in the study groups.

RESULTS

The distribution of MTHFR (C677T) genotype frequencies, ie, CC, TT, and CT, among the patients was 64.7%, 2.18%, and 33.09%, respectively. In the healthy control group, the CC, TT, and CT frequencies were 78.91%, 1.09%, and 20.1%, respectively. The frequencies of C and T alleles were 81.2% and 18.7%, respectively, in the patient subjects, while they were 88.9% and 11.09%, respectively, among the healthy control group. Frequencies of the CT genotype and the T allele were significantly different (P = 0.007 and P = 0.005, respectively) between the control and the case subjects.

CONCLUSION

This study shows an association of the CT genotype and the T allele of the MTHFR (C667T) gene with increased genetic risk for breast cancer among Indian women.

Lack of association between MTHFR C677T polymorphism and breast cancer risk in Ahvaz, west south-Iran

Background:

Association between C677T polymorphism of the methylenetetrahydrofolate reductase (MTHFR), a key enzyme involved in folate metabolism and DNA methylation, and breast cancer risk are inconsistent. We investigated in a case-control study, possible effect of the common MTHFR C677T polymorphism on breast cancer risk in a sample of Iranian patients.

Materials and Methods:

The study subjects comprised of 123 breast cancer cases and 110 cancer-free control, who were matched for age and body mass index (BMI). C677T genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. Lipid profile was measured in all subjects by standard method.

Results:

The genotypes distributions (CC, CT, and TT) were 55.3, 39, and 5.7% in breast cancer cases and 51.8, 44.5, and 3.6% in controls. Chi square analysis revealed that there was no significant association between breast cancer risk and MTHFR genotypes and alleles. Additionally, no significant association was observed between C677T genotypes and biochemistry parameters. A multinomial logistic regression model with MTHFR genotypes, lipid profiles, BMI and age as covariates revealed that there is no significant association between MTHFR genotypes and risk of breast cancer, but higher values of LDL and HDL significantly increase risk of breast cancer.

Conclusions:

Our findings do not support the hypothesis that genetic variation in the MTHFR C677T polymorphism is implicated in the breast cancer risk in a sample of Iranian patients.

The methylenetetrahydrofolate reductase C677T polymorphism and breast cancer risk in Asian populations

BACKGROUND

Methylenetetrahydrofolate (MTHFR) is the key enzyme of the folate metabolic pathway and several studies have pointed to association between the MTHFR C677T polymorphism and breast cancer risk. Although significant association was observed in some studies, in others no clear link could be established.

OBJECTIVE

A meta-analysis of published Asian case control studies was therefor carried out to shed further light on any C677T breast cancer association.

MATERIALS AND METHODS

PubMed, Springer Link, Google Scholar and Elsevier databases were searched for case control studies of associations between MTHFR C677T polymorphism and breast cancer risk. Odds ratios (ORs) with 95% confidence intervals (CIs) were estimated to assess the association. A total of 36 studies including 8,040 cases and 10,008 controls were included in the present meta-analysis.

RESULTS

Overall, a significantly elevated breast cancer risk was associated with the T allele and TT genotype in homozygote comparison and dominant genetic models when all studies were pooled into the meta-analysis (T vs C (allele contrast model): OR=1,23, 95%CI=1.13-1.37, p=0.000 ; TT vs CC(homozygote model): OR=1.38, 95%CI=1.16-1.63, p=0.0003; TT+CT vs CC (dominant model): OR=1.12, 95%CI=1.01-1.23, p=0.02).

CONCLUSIONS

The present meta-analysis strongly suggested a significant association between the MTHFR C677T polymorphism and risk of breast cancer in Asian populations.

Genomic medicine and risk prediction across the disease spectrum

Genomic medicine is based on the knowledge that virtually every medical condition, disease susceptibility or response to treatment is caused, regulated or influenced by genes. Genetic testing may therefore add value across the disease spectrum, ranging from single-gene disorders with a Mendelian inheritance pattern to complex multi-factorial diseases. The critical factors for genomic risk prediction are to determine: (1) where the genomic footprint of a particular susceptibility or dysfunction resides within this continuum, and (2) to what extent the genetic determinants are modified by environmental exposures. Regarding the small subset of highly penetrant monogenic disorders, a positive family history and early disease onset are mostly sufficient to determine the appropriateness of genetic testing in the index case and to inform pre-symptomatic diagnosis in at-risk family members. In more prevalent polygenic non-communicable diseases (NCDs), the use of appropriate eligibility criteria is required to ensure a balance between benefit and risk. An additional screening step may therefore be necessary to identify individuals most likely to benefit from genetic testing. This need provided the stimulus for the development of a pathology-supported genetic testing (PSGT) service as a new model for the translational implementation of genomic medicine in clinical practice. PSGT is linked to the establishment of a research database proven to be an invaluable resource for the validation of novel and previously described gene-disease associations replicated in the South African population for a broad range of NCDs associated with increased cardio-metabolic risk. The clinical importance of inquiry concerning family history in determining eligibility for personalized genotyping was supported beyond its current limited role in diagnosing or screening for monogenic subtypes of NCDs. With the recent introduction of advanced microarray-based breast cancer subtyping, genetic testing has extended beyond the genome of the host to also include tumor gene expression profiling for chemotherapy selection. The decreasing cost of next generation sequencing over recent years, together with improvement of both laboratory and computational protocols, enables the mapping of rare genetic disorders and discovery of shared genetic risk factors as novel therapeutic targets across diagnostic boundaries. This article reviews the challenges, successes, increasing inter-disciplinary integration and evolving strategies for extending PSGT towards exome and whole genome sequencing (WGS) within a dynamic framework. Specific points of overlap are highlighted between the application of PSGT and exome or WGS, as the next logical step in genetically uncharacterized patients for whom a particular disease pattern and/or therapeutic failure are not adequately accounted for during the PSGT pre-screen. Discrepancies between different next generation sequencing platforms and low concordance among variant-calling pipelines caution against offering exome or WGS as a stand-alone diagnostic approach. The public reference human genome sequence (hg19) contains minor alleles at more than 1 million loci and variant calling using an advanced major allele reference genome sequence is crucial to ensure data integrity. Understanding that genomic risk prediction is not deterministic but rather probabilistic provides the opportunity for disease prevention and targeted treatment in a way that is unique to each individual patient.

Methylenetetrahydrofolate Reductase A1298C Polymorphism and Breast Cancer Risk: A Meta-analysis of 33 Studies

Methylenetetrahydrofolate reductase (MTHFR) enzyme is essential for DNA synthesis and DNA methylation, and its gene polymorphisms have been implicated as risk factors for birth defects, neurological disorders, and different types of cancers. Several studies have investigated the association between the MTHFR A1298C polymorphism and breast cancer (BC) risk, but the results were inconclusive. To assess the risk associated with MTHFR A1298C polymorphism, a comprehensive meta-analysis was performed. PubMed, Google Scholar, Elsevier and Springer Link databases were searched for case-control studies relating the association between MTHFR A1298C polymorphism and BC risk and estimated summary odds ratios (ORs) with confidence intervals (CIs) for assessment. Up to January 2014, 33 case-control studies involving 15,919 BC patients and 19,700 controls were included in the present meta-analysis. The results showed that the A1298C polymorphism was not associated with BC risk in all the five genetic models (C vs. A allele (allele contrast): OR = 0.99, 95% confidence interval (CI): 0.93–1.05; AC versus AA (heterozygote/codominant): OR = 0.97, 95% CI: 0.89–1.04; CC versus AA (homozygote): OR = 0.99, 95% CI: 0.91–1.06; CC + AC versus AA (dominant model): OR = 0.97, 95% CI: 0.90–1.05; and CC versus AC + AA (recessive model): OR = 0.99, 95% CI: 0.91–1.07). The present meta-analysis did not support any association between the MTHFR A1298C polymorphism and BC risk.

Controversial roles of methylenetetrahydrofolate reductase polymorphisms and folate in breast cancer disease

Breast cancer (BC) represents a highly heterogeneous tumour at both the clinical and molecular levels. Single-nucleotide polymorphisms (SNPs) of the folate-metabolising enzyme methylenetetrahydrofolate-reductase (MTHFR) may modify the association between folate intake and BC and influence plasma folate concentration. The role of folate in BC is equivocal, association studies between the common MTHFR SNPs C677T and A1298C and BC risk are controversial. In this study, I have reviewed observed associations between folate intake, as well as its blood levels, and BC. The purpose of this review is to analyse the role of folate and the two SNPs associated with reduced enzyme activity in BC. I explored the most relevant and updated work that emphasises positive and negative associations among these variables. My findings indicate that no definitive conclusions can be drawn from the studies on this topic. However, this manuscript highlights variables that could be useful to explore in further association analyses.

A meta-analysis of genotypes and haplotypes of methylenetetrahydrofolate reductase gene polymorphisms in breast cancer

The association between methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and breast cancer risk has been extensively explored, but their results are conflicting rather than conclusive. To derive a more precise estimation, we carried out not only an updated meta-analysis but also a combined analysis based on all the available studies estimating the association between MTHFR C677T and/or A1298C and breast cancer risk. With respect to C677T polymorphism, the results suggested that 677T allele was associated with significantly elevated breast cancer risk in overall analysis (T vs. C: OR 1.073, 95 % CI 1.028-1.120; TT vs. CC: OR 1.177, 95 % CI 1.072-1.293; TT vs. CC + CT: OR 1.175, 95 % CI 1.073-1.288); Stratifying by ethnicity, significantly increased risk was only found in East Asians (T vs. C: OR 1.150, 95 % CI 1.039-1.273; TT vs. CC: OR 1.441, 95 % CI 1.145-1.814; TT vs. CC + CT: OR 1.413, 95 % CI 1.148-1.739); When stratified by menopausal status, statistically significant association was found for postmenopausal women (CT + TT vs. CC: OR 1.092, 95 % CI 1.011-1.179). In regard to A1298C polymorphism, no significant associations were found between the polymorphism and breast cancer risk. With respect to MTHFR haplotypes, significantly elevated breast cancer risk was associated with 677T-1298C for overall result (OR 1.498, 95 % CI 1.143-1.962) and for Caucasians (OR 2.088, 95 % CI 1.277-3.416) when compared with 677C-1298A; Haplotype 677C-1298C might provide higher protection than 677C-1298A in East Asians (OR 0.840, 95 % CI 0.742-0.949). The combined genotypes for C677T and A1298C produced a significant OR for the 677TT/1298AC relative to 677CC/1298AA in overall population (OR 2.047, 95 % CI 1.275-3.288); When stratified by ethnicity, significant ORs were only found for East Asians (677CC/1298CC vs. 677CC/1298AA: OR 0.686, 95 % CI 0.478-0.985; 677TT/1298AC vs. 677CC/1298AA: OR 2.181, 95 % CI 1.179-4.035). The findings suggest that the MTHFR C677T polymorphism but not A1298C, and some variants on their combined genotypes or haplotypes may be involved with the development of breast cancer.

The methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and tumor risk: evidence from 134 case-control studies

Methylenetetrahydrofolate reductase (MTHFR) is an important enzyme involved in folate metabolism, which is essential for DNA synthesis and methylation. Genetic variations in the MTHFR gene seem to contribute to a decreased activity of MTHFR, ultimately confer increased susceptibility to cancer. As the most extensively studied polymorphism, MTHFR C677T polymorphism was shown to contribute to cancer susceptibility but the results were inconsistent. The authors performed a meta-analysis including 134 studies (46,207 cases and 69,160 controls) to address the issue. Odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were used to assess the association. Overall, a significant elevated risk of cancer was associated with the MTHFR C677T polymorphism in T-allele versus C-allele comparison (OR = 1.06, 95% CI 1.02-1.11, P(heterogeneity) < 0.001), homozygote model (OR = 1.08, 95% CI 1.01-1.17, P(heterogeneity) < 0.001) and dominant model (OR = 1.05, 95% CI 1.00-1.10, P(heterogeneity) < 0.001). In the stratified analyses, significantly increased cancer risks were indicated among Asians in all genetic models except for heterozygote model. Further analysis revealed that C677T was significantly associated with an increased risk of esophageal and stomach cancer. This meta-analysis supports an association between the MTHFR C677T polymorphism and increased risk of esophageal and stomach cancer, especially among Asians. Additionally, more high-quality studies and that the covariates responsible for heterogeneity should be controlled to obtain a more conclusive response about the function of MTHFR C677T in cancer.

Folate intake and MTHFR polymorphism C677T is not associated with ovarian cancer risk: evidence from the meta-analysis

Folate is essential for DNA synthesis and methylation and implicated in the process of carcinogenesis. Several studies inconclusively suggested increased folate intake may reduce ovarian cancer risk. Studies concerning the association between C677T polymorphism in methylenetetrahydrofolate reductase (MTHFR), an important enzyme in folate metabolism, and ovarian cancer risk also resulted in no agreement. The meta-analysis was conducted based on current studies to assess the association between folate intake, the MTHFR C667T polymorphism and ovarian cancer risk. 1,158 cases out of 217,309 participants from four cohort studies, 4,519 cases and 6,031 controls from four case-control studies about folate intake along with 5,617 cases and 9,808 controls from 10 publications concerning the polymorphism were pooled, respectively. We detected no significant association between total folate (RR = 1.04, 95 % confidence interval (CI) = 0.87-1.23) or dietary folate (RR = 0.88, 95 % CI = 0.75-1.05) intake and ovarian cancer risk, and also no significant relationship was found between MTHFR C677T polymorphism and ovarian cancer risk (TT vs. CC: odds ratio (OR) = 1.15, 95 % CI = 0.90-1.46; CT vs. CC: OR = 1.04, 95 % CI = 0.94-1.16). Our analysis indicated neither folate intake nor MTHFR C677T polymorphism is related to altered susceptibility of ovarian cancer.

Relationships among MTHFR a1298c gene polymorphisms and methylation status of Dact1 gene in transitional cell carcinomas

OBJECTIVES

The purpose of this study was to determine the relationship between methylation status of the Dact1 gene and MTHFR a1298c polymorphic forms in transitional cell carcinoma tissues in a Chinese population.

METHODS

Polymorphisms of folate metabolism enzyme gene MTHFR were assessed by restrictive fragment length polymorphism (RFLP) methods and PCR-based DNA methylation analysis was used to determine the CpG island methylation status of the Dact1 gene. Associations between the methylation status of the Dact1 gene and clinical characteristics, as well as MTHFR a1298c polymorphisms, were analyzed.

RESULTS

aberrant methylation of the Dact1 gene was found in 68.3% of cancer tissues and 12.4% of normal tissues,. The methylation rate of the Dact1 gene in cancer tissues was significantly higher in patients with lymph node metastasis than in those without lymph node metastasis (46.3% vs. 17.2%, P = 0.018). No association was found between aberrant DNA methylation and selected factors including sex, age, tobacco smoking, alcohol consumption and green tea consumption. After adjusting for potential confounding variables, variant allele of MTHFR a1298c was found to be associated with methylation of the Dact1 gene. Compared with wild type CC, the odds ratio was 4.33 (95% CI: 1.06-10.59) for AC and 4.95 (95% CI: 1.18-12.74) for AA. The N stage in TNM staging and the occurrence of lymph node metastasis were associated with an MTHFR 1298 AAμAC genotype (P<0.05).

CONCLUSION

MTHFR 1298 AC and AA genotypes might help maintain a normal methylation status of the Dact1 gene, aberrant CpG island methylation of which is closely related to the genesis and progression of transitional cell carcinoma.

Genotyping analysis and ¹⁸FDG uptake in breast cancer patients: a preliminary research

Background

Diagnostic imaging plays a relevant role in the care of patients with breast cancer (BC). Positron Emission Tomography (PET) with 18F-fluoro-2-deoxy-D-glucose (FDG) has been widely proven to be a clinical tool suitable for BC detection and staging in which the glucose analog supplies metabolic information about the tumor. A limited number of studies, sometimes controversial, describe possible associations between FDG uptake and single nucleotide polymorphisms (SNPs). For this reason this field has to be explored and clarified. We investigated the association of SNPs in GLUT1, HIF-1a, EPAS1, APEX1, VEGFA and MTHFR genes with the FDG uptake in BC.

Methods

In 26 caucasian individuals with primary BC, whole-body PET-CT scans were obtained and quantitative analysis was performed by calculating the maximum Standardized Uptake Value normalized to body-weight (SUVmax) and the mean SUV normalized to body-weight corrected for partial volume effect (SUVpvc). Human Gene Mutation Database and dbSNP Short Genetic Variations database were used to analyze gene regions containing the selected SNPs. Patient genotypes were obtained using Sanger DNA sequencing analysis performed by Capillary Electrophoresis.

Results

BC patients were genotyped for the following nine SNPs: GLUT1: rs841853 and rs710218; HIF-1a: rs11549465 and rs11549467; EPAS1: rs137853037 and rs137853036; APEX1: rs1130409; VEGFA: rs3025039 and MTHFR: rs1801133. In this work correlations between the nine potentially useful polymorphisms selected and previously suggested with tracer uptake (using both SUVmax and SUVpvc) were not found.

Conclusions

The possible functional influence of specific SNPs on FDG uptake needs further studies in human cancer. In summary, this is the first pilot study, to our knowledge, which investigates the association between a large panel of SNPs and FDG uptake specifically in BC patients. This work represents a multidisciplinary and translational medicine approach to study BC where, the possible correlation between SNPs and tracer uptake, may be considered to improve personalized cancer treatment and care.

Lack of significance of the BRCA2 promoter methylation status in different genotypes of the MTHFR a1298c polymorphism in ovarian cancer cases in Iran

OBJECTIVE

Promoter methylation, which can be regulated by MTHFR activity, is associated with silencing of genes. In this study we evaluated the methylation status (type) of the BRCA2 promoter in ovarian cancer patients carrying different genotypes of the MTHFR gene (A or C polymorphisms at position 1298).

METHODS

The methylation type of the BRCA2 promoter was evaluated using bisulfate-modified DNA in methylation- specific PCR and the MTHFRa1278c polymorphism was assessed by PCR-RFLP.

RESULTS

Analysis of the BRCA2 promoter methylation type of cases showed that 7 out of 60 cases (11.7%) were methylated while the remaining 53 (88.3%) were unmethylated. In methylated cases, one out of the 7 cases had a CC genotype and the remaining 6 methylated cases had an AC genotype. The AA genotype was absent. In unmethylated cases, 34, 18, and one out of these had AC, AA and CC genotype, respectively.

CONCLUSION

There was no significant relationship between the methylation types of the BRCA2 promoter in different genotypes of MTHFRa1298c polymorphism in ovarian cancer; p=0.255. There was no significant relation between the methylation types of the BRCA2 promoter in different genotypes of the MTHFRa1298c polymorphism in ovarian cancer.

A literature review of MTHFR (C677T and A1298C polymorphisms) and cancer risk

5,10-Methlenetetrahydrofolate reductase (MTHFR) is one of the most important enzymes for folate metabolism. This enzyme is mapped on chromosome 1, which is located at the end of the short arm (1p36.3). The C677T and A1298C are MTHFR polymorphisms that decrease in vitro MTHFR enzyme activity. Folate metabolism plays a key role in cell metabolism. These reactions are associated with purine-pyrimidine synthesis: DNA, RNA, and protein methylation. Polymorphism is also a factor in biodiversity, and be affected by ethnic heritage and geographic locale. In the case of unknown outcomes, not only should all geographical regions be investigated to ascertain biodiversity, but all populations as well to fully understand the variations in the effect. PUBMED was searched from January 2006 to December 2011 to develop an investigatory pursuit strategy. MTHFR, cancer, C677T, A1298C, and polymorphisms were key words used to focus the search. The literature review included all published relevant cancer types and MTHFR polymorphisms for that 5 years period. All selected polymorphisms data for cancer types was listed in tables for easy access and retrieval.

MTHFR polymorphisms and ovarian cancer risk: a meta-analysis

The C677T and A1298C polymorphisms of methylenetetrahydrofolate reductase (MTHFR) have been reported to alter the risk of ovarian cancer. However, the results are still inconclusive. For better understanding of the effect of these two polymorphisms on ovarian cancer risk, a meta-analysis was performed. An extensive search was performed to identify all case-control studies investigating such association. The strength of association between these two polymorphisms and ovarian cancer risk was assessed by odds ratio (OR) with the corresponding 95 % confidence interval (95 % CI). 3,496 cases and 3,631 controls for C677T polymorphism and 3,280 cases and 3,346 controls for A1298C polymorphism were included in this meta-analysis. The results suggested that there were no significant associations between C677T and A1298C polymorphisms and ovarian cancer risk in overall comparisons in all genetic models (For C677T: TT vs. CC: OR = 0.94, 95 % CI = 0.71-1.24, P = 0.65; CT vs. CC: OR = 1.03, 95 % CI = 0.93-1.14, P = 0.57; TT/CT vs. CC: OR = 1.01, 95 % CI = 0.88-1.16, P = 0.87; TT vs.

CC/CT

OR = 0.93, 95 % CI = 0.72-1.20, P = 0.58. For A1298C: CC vs. AA: OR = 1.05, 95 % CI = 0.88-1.25, P = 0.65; CA vs. AA: OR = 0.98, 95 % CI = 0.88-1.08, P = 0.66; CC/CA vs. AA: OR = 0.99, 95 % CI = 0.90-1.09, P = 0.85; CC vs. AA/CA: OR = 1.06, 95 % CI = 0.90-1.26, P = 0.46). Subgroup analysis based on ethnicities and influence analysis did not perturb the results. In conclusion, the results of this meta-analysis indicate that the MTHFR C677T and A1298C polymorphisms are not associated with ovarian cancer risk, especially in Caucasians.

Association of PHB 1630 C>T and MTHFR 677 C>T polymorphisms with breast and ovarian cancer risk in BRCA1/2 mutation carriers: results from a multicenter study

BACKGROUND

The variable penetrance of breast cancer in BRCA1/2 mutation carriers suggests that other genetic or environmental factors modify breast cancer risk. Two genes of special interest are prohibitin (PHB) and methylene-tetrahydrofolate reductase (MTHFR), both of which are important either directly or indirectly in maintaining genomic integrity.

METHODS

To evaluate the potential role of genetic variants within PHB and MTHFR in breast and ovarian cancer risk, 4102 BRCA1 and 2093 BRCA2 mutation carriers, and 6211 BRCA1 and 2902 BRCA2 carriers from the Consortium of Investigators of Modifiers of BRCA1 and BRCA2 (CIMBA) were genotyped for the PHB 1630 C>T (rs6917) polymorphism and the MTHFR 677 C>T (rs1801133) polymorphism, respectively.

RESULTS

There was no evidence of association between the PHB 1630 C>T and MTHFR 677 C>T polymorphisms with either disease for BRCA1 or BRCA2 mutation carriers when breast and ovarian cancer associations were evaluated separately. Analysis that evaluated associations for breast and ovarian cancer simultaneously showed some evidence that BRCA1 mutation carriers who had the rare homozygote genotype (TT) of the PHB 1630 C>T polymorphism were at increased risk of both breast and ovarian cancer (HR 1.50, 95%CI 1.10-2.04 and HR 2.16, 95%CI 1.24-3.76, respectively). However, there was no evidence of association under a multiplicative model for the effect of each minor allele.

CONCLUSION

The PHB 1630TT genotype may modify breast and ovarian cancer risks in BRCA1 mutation carriers. This association need to be evaluated in larger series of BRCA1 mutation carriers.

Opportunities and challenges for nutritional proteomics in cancer prevention

Knowledge gaps persist about the efficacy of cancer prevention strategies based on dietary food components. Adaptations to nutrient supply are executed through tuning of multiple protein networks that include transcription factors, histones, modifying enzymes, translation factors, membrane and nuclear receptors, and secreted proteins. However, the simultaneous quantitative and qualitative measurement of all proteins that regulate cancer processes is not practical using traditional protein methodologies. Proteomics offers an attractive opportunity to fill this knowledge gap and unravel the effects of dietary components on protein networks that impinge on cancer. The articles presented in this supplement are from talks proffered in the "Nutrition Proteomics and Cancer Prevention" session at the American Institute for Cancer Research Annual Research Conference on Food, Nutrition, Physical Activity and Cancer held in Washington, DC on October 21 and 22, 2010. Recent advances in MS technologies suggest that studies in nutrition and cancer prevention may benefit from the adoption of proteomic tools to elucidate the impact on biological processes that govern the transition from normal to malignant phenotype; to identify protein changes that determine both positive and negative responses to food components; to assess how protein networks mediate dose-, time-, and tissue-dependent responses to food components; and, finally, for predicting responders and nonresponders. However, both the limited accessibility to proteomic technologies and research funding appear to be hampering the routine adoption of proteomic tools in nutrition and cancer prevention research.

Folate intake and methylenetetrahydrofolate reductase gene polymorphisms as predictive and prognostic biomarkers for ovarian cancer risk

Folic acid and methylenetetrahydrofolate reductase (MTHFR) may affect the development of human cancer. However, few studies have evaluated folate intake and MTHFR in susceptibility to and prognosis of patients with ovarian cancer. We conducted a prospective case-control study in 215 ovarian cancer patients and 218 controls (all Chinese) between Jan. 2004 and Jan. 2007. MTHFR C677T genotyping was done by PCR-RFLP. All patients were followed up until Dec. 2010. We found a 2.43-fold increased risk of ovarian cancer among MTHFR 677TT carriers, and a decreased risk of ovarian cancer in individuals with high folate intake (OR = 0.54, 95% CI = 0.32-0.94). Cox regression survival analysis showed that among the ovarian cancer patients, those carrying the 677TT genotype had a higher risk of death (HR = 2.17, 95% CI = 1.20-4.79), while high folate intake was associated with a lower risk of death (HR = 0.43, 95% CI = 0.33-0.88). Moreover, MTHFR 677CC carriers with higher folate intake showed a lower risk of death from ovarian cancer (HR = 0.32, 95% CI = 0.27-0.82). In summary, high folate intake may lessen susceptibility and improve the prognosis of ovarian cancer patients, while the MTHFR 677TT genotype appears to increase ovarian cancer risk and worsen its prognosis in a Chinese population.

Folate and choline metabolism gene variants in relation to ovarian cancer risk in the Polish population

Data indicates that genetic factors alone do not account for ovarian tumorigenesis, suggesting that epigenetic status additionally affects this process. Therefore, we assessed the possible contribution of polymorphic variants of genes that may affect DNA methylation to the risk of ovarian cancer incidence in the Polish population. Using PCR-RFLP and HRM analyses, we studied the distribution of BHMT (rs3733890), MTHFD1 (rs2236225), MTHFR (rs1801133), MTR (rs1805087), MTRR (rs1801394) and TCN2 (rs1801198) genotypes and alleles in patients with ovarian cancer (n = 136) and controls (n = 160). Moreover, using DNA and methylation-specific PCR (MSP) we also determined the methylation of the Cadherin 13 (CDH13) promoter in cancerous tissue from these patients. We did not observe a significant association between all studied gene variants and the incidence of ovarian cancer. The lowest P (trend) = 0.1226 was observed for the MTHFR Ala222Val polymorphism. Moreover, the lowest P = 0.0772 was found in the comparison of MTHFR Ala/Ala versus Val/Val and Val/Ala genotypes in patients and control groups. The multifactor dimensionality reduction analysis also did not indicate a significant interactive genetic effect on ovarian cancer incidence for all analyzed SNPs. However, we observed frequent methylation of the CDH13 promoter in approximately 21% (29/136) patients with ovarian carcinomas. Our results might suggest that the selected polymorphic gene variants may not contribute to ovarian cancer incidence.

Association of the functional polymorphism C677T in the methylenetetrahydrofolate reductase gene with colorectal, thyroid, breast, ovarian, and cervical cancers

BACKGROUND

Polymorphisms of the gene encoding methylenetetrahydrofolate reductase (MTHFR) have been studied widely in various cancers, excluding thyroid cancer. However, reports on the association of various polymorphisms with certain cancers are contradictory.

MATERIALS AND METHODS

We have investigated whether the prevalence of the most common polymorphism (C677T) in the MTHFR gene has any link with various cancers, using genomic DNA and polymerase chain reaction restriction fragment length polymorphism (PCRRFLP) analysis.

RESULTS

The frequency of the heterozygous variant (677CT) but not that of 677TT was found to be significantly higher in colorectal cancer cases than in controls (p < 0.039; odds ratio 2.35 and 95% confidence interval 1.02-5.415). The frequencies for 677CT were 11.0 and 5.0% in colorectal cancer samples and controls, respectively. In ovarian cancer, the frequency of the 677TT variant was 6.0% which differed significantly (p < 0.026) from the control value of 1.0%. However, the frequencies of the variants in cervical, thyroid, and breast cancer cases did not differ from controls.

CONCLUSIONS

Our data taken together with other reports indicates that the polymorphism C677T of MTHFR is a risk factor for developing colorectal cancer but not cervical, thyroid, and breast cancers. The present study also reconfirms that frequencies of the variants are not gender-specific.

MTHFR polymorphisms and breast cancer risk

INTRODUCTION

Two functional single nucleotide polymorphisms (SNPs) in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene, C677T and A1298C, lead to decreased enzyme activity and affect chemosensitivity of tumour cells.

MATERIAL AND METHODS

We evaluated these two common polymorphisms and breast cancer risk association in an Iranian sporadic breast cancer population-based case-control study of 294 breast cancer cases and 306 controls using a PCR-RFLP-based assay.

RESULTS

Analyses of affected and controls show that homozygote genotype MTHFR 677CC has the highest frequency in both groups (28.3% in patients and 25.3% in control group). Genotype MTHFR 677CT and genotype MTHFR 1298AC were found to be statistically significant risk factors in our population (odds ratio: 1.6, 95% CI: 1.019-2.513, p = 0.041; and odds ratio: 2.575, 95% CI: 1.590-4.158, p = 0.001 respectively).

CONCLUSIONS

We can conclude based on the results of our study that a significant association between breast cancer and C677T and A1298C polymorphism might exist.

Lack of association between methylenetetrahydrofolate reductase gene A1298C polymorphism and breast cancer susceptibility

Published data on the association between methylenetetrahydrofolate reductase gene (MTHFR) A1298C polymorphism and breast cancer risk are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed. Medline, PubMed, Embase, and Web of Science were searched. Crude ORs with 95% CIs were used to assess the strength of association between the MTHFR A1298C polymorphism and breast cancer risk. The pooled ORs were performed for co-dominant model (AC vs. AA, CC vs. AA), dominant model (CC+AC vs. AA), and recessive model (CC vs. AC+AA), respectively. A total of 26 studies including 12,244 cases and 15,873 controls were involved in this meta-analysis. Overall, no significant associations were found between MTHFR A1298C polymorphism and breast cancer risk when all studies pooled into the meta-analysis (AC vs. AA: OR=0.99, 95% CI 0.94-1.05; CC vs. AA: OR 0.99, 95% CI 0.90-1.09; dominant model: OR=0.99, 95% CI 0.95-1.04; and recessive model: OR=0.98, 95% CI 0.90-1.08). In the subgroup analysis by ethnicity or study design, still no significant associations were found for all comparison models. In conclusion, this meta-analysis suggests that the MTHFR A1298C polymorphism may be not associated with breast cancer development. However, large sample and representative population-based studies with homogeneous breast cancer patients and well matched controls are warranted to confirm this finding.

MTHFR polymorphisms in relation to ovarian cancer risk

OBJECTIVE

Folate has been hypothesized to influence carcinogenesis due to its dual role in DNA methylation, which regulates gene expression, and synthesis of purine and thymidylate, which is vital for DNA repair. Thus, we examined ovarian cancer risk in relation to two functional polymorphisms (C677T and A1298C) in the MTHFR gene.

METHODS

We genotyped the C677T (rs1801133) and A1298C (rs1801131) MTHFR polymorphisms in 1642 cases and 2068 controls from three studies, the New England Case Control Study (NEC), Nurses' Health Study (NHS), and Mayo Clinic Ovarian Cancer Case Control Study (MAY).

RESULTS

Overall, we observed no association between either SNP and ovarian cancer risk (pooled C677T p(trend)=0.59 and A1298C p(trend)=0.58). Significant associations (C677T p(trend)=0.001, A1298C p(trend)=0.02) between these MTHFR SNPs and serous ovarian cancer risk were observed in the NEC study, but were not replicated in the NHS and MAY studies.

CONCLUSIONS

MTHFR SNPs C677T and A1298C are not associated with ovarian cancer risk. Our results highlight the need for validation of genetic findings.

MTHFR C677T and postmenopausal breast cancer risk by intakes of one-carbon metabolism nutrients: a nested case-control study

Introduction

The C677T polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene has been hypothesized to increase breast cancer risk. However, results have been inconsistent, and few studies have reported the association by menopausal status or by intakes of nutrients participating in one-carbon metabolism. Our aims were to investigate whether MTHFR C677T was associated with postmenopausal breast cancer risk and whether this relation was modified by intakes of folate, methionine, vitamins B₂, B₆, and B₁₂, and alcohol.

Methods

We studied 318 incident breast cancer cases and 647 age- and race-matched controls participating in a nested case-control study of postmenopausal women within the VITamins And Lifestyle (VITAL) cohort. Genotyping was conducted for MTHFR C677T and dietary and supplemental intakes were ascertained from a validated questionnaire. Adjusted odds ratios (OR) and 95% confidence intervals (CI) were calculated using unconditional logistic regression.

Results

We observed a 62% increased risk of breast cancer among postmenopausal women with the TT genotype (OR = 1.62; 95% CI: 1.05 to 2.48). Women with a higher number of variant T alleles had higher risk of breast cancer (P for trend = 0.04). Evidence of effect-modification by intakes of some B vitamins was observed. The most pronounced MTHFR-breast cancer risks were observed among women with the lowest intakes of dietary folate (P for interaction = 0.02) and total (diet plus supplemental) vitamin B₆ (P for interaction = 0.01), with no significant increased risks among women with higher intakes.

Conclusions

This study provides support that the MTHFR 677TT genotype is associated with a moderate increase in risk of postmenopausal breast cancer and that this risk may be attenuated with high intakes of some one-carbon associated nutrients.

Dietary intake of folate, vitamin B6, and vitamin B12, genetic polymorphism of related enzymes, and risk of breast cancer: a case-control study in Brazilian women

Background

Several studies have determined that dietary intake of B vitamins may be associated with breast cancer risk as a result of interactions between 5,10-methylenetetrahydrofolate reductase (MTHFR) and methionine synthase (MTR) in the one-carbon metabolism pathway. However, the association between B vitamin intake and breast cancer risk in Brazilian women in particular has not yet been investigated.

Methods

A case-control study was conducted in São Paulo, Brazil, with 458 age-matched pairs of Brazilian women. Energy-adjusted intakes of folate, vitamin B₆, and vitamin B₁₂ were derived from a validated Food Frequency Questionnaire (FFQ). Genotyping was completed for MTHFR A1298C and C677T, and MTR A2756G polymorphisms. A logistical regression model was used to calculate odds ratios (ORs) and 95% confidence intervals (95% CIs).

Results

Neither dietary intake of folate, vitamin B₆, or vitamin B₁₂ nor MTHFR polymorphisms were independently associated with breast cancer risk. Analysis stratified by menopausal status showed a significant association between placement in the highest tertile of folate intake and risk of breast cancer in premenopausal women (OR = 2.17, 95% CI: 1.23–3.83; P_trend = 0.010). The MTR 2756GG genotype was associated with a higher risk of breast cancer than the 2756AA genotype (OR = 1.99, 95% CI = 1.01–3.92; P_trend = 0.801), and statistically significant interactions with regard to risk were observed between the MTHFR A1298C polymorphism and folate (P = 0.024) or vitamin B₆ (P = 0.043), and between the MTHFR C677T polymorphism and folate (P = 0.043) or vitamin B₁₂ (P = 0.022).

Conclusion

MTHFR polymorphisms and dietary intake of folate, vitamin B₆, and vitamin B₁₂ had no overall association with breast cancer risk. However, increased risk was observed in total women with the MTR 2756GG genotype and in premenopausal women with high folate intake. These findings, as well as significant interactions between MTHFR polymorphisms and B vitamins, warrant further investigation.

Methionine-dependence phenotype in the de novo pathway in BRCA1 and BRCA2 mutation carriers with and without breast cancer

Methionine-dependence phenotype (MDP) refers to the reduced ability of cells to proliferate when methionine is restricted and/or replaced by its immediate precursor homocysteine. MDP is a characteristic of human tumors in vivo, human tumor cell lines, and normal somatic tissue in some individuals. It was hypothesized that MDP is a risk factor for developing breast cancer in BRCA (BRCA1 and BRCA2) germline mutation carriers. To test the hypothesis, human peripheral blood lymphocytes of BRCA carriers with and without breast cancer and healthy non-carrier relatives (controls) were cultured for 9 days in medium containing either 0.1 mmol/L L-methionine or 0.2 mmol/L D,L-homocysteine, with the ratio of viable cell growth in both types of medium after 9 days used to calculate the methionine-dependence index (MDI), a measure of MDP. We also tested whether MDP was associated with common polymorphisms in methionine metabolism. Viable cell growth, MDI, and polymorphism frequency in MTRR (A66G and C524T) and MTHFR (A1298C and A1793G) did not differ among the study groups; however, MDI tended to be higher in BRCA carriers with breast cancer than those without and was significantly increased in MTHFR 677T allele carriers relative to wild-type carriers (P=0.017). The presence of MTR A2756G mutant allele and MTHFR C677T mutant allele in carriers was associated with increased breast cancer risk [odds ration, 3.2 (P=0.16; 95% confidence interval, 0.76-13.9) and 3.9 (P=0.09; 95% confidence interval, 0.93-16.3), respectively]. The results of this study support the hypothesis that defects in methionine metabolism may be associated with breast cancer risk in BRCA carriers.

Do BRCA1 modifiers also affect the risk of breast cancer in non-carriers?

We studied whether or not single nucleotide polymorphisms (SNPs), which have been shown to modify the risk of breast cancer in women with a BRCA1 mutation, are associated with cancer risk in unselected (non-hereditary) breast cancer patients. We genotyped seven SNPs in six distinct genes (PHB, RAD51, ITGB3, TGFB1, VEGF, MTHFR) in 1100 unselected Polish breast cancer patients and 1100 controls. The frequencies of genotypes were similar in cases and controls. In a subgroup analysis, we found a positive association between the homozygous genotype PHB 1630C/T and medullary breast cancer (odds ratio (OR)=4.0, 95% confidence interval (CI) 1.1-14.0). PHB 1630C/T was also associated with tumours negative for oestrogen receptor (OR=2.2, 95% CI 1.13-4.4) or progesterone receptor (OR=2.8, 95% CI 1.4-5.8). Our results show that, in general, the single nucleotide polymorphisms which modify the risk of hereditary breast cancer in Poland do not modify the risk of sporadic breast cancer. The PHB 1630 C/T single nucleotide polymorphism was associated with breast cancers with clinical features typical for BRCA1-positive tumours and is deserving of further study.

The VEGF_936_C>T 3'UTR polymorphism reduces BRCA1-associated breast cancer risk in Polish women

The vascular endothelial growth factor (VEGF) plays a crucial role in the initiation of angiogenesis, which is an important stage in tumor development. A functional 936_C>T polymorphism in the VEGF gene and its association with sporadic breast cancer risk has been analyzed in various studies yielding conflicting results. To analyze the role of this polymorphism in modifying hereditary breast and ovarian cancer risks, we conducted a case-control study and genotyped 755 Polish BRCA1 carriers, including 319 breast cancer cases, 146 ovarian cancer cases, and 290 unaffected controls. The results revealed an association of the CT+TT genotypes with a reduced breast cancer risk (OR(adj) 0.63, 95% CI, 0.41-0.98; OR(clustered) 0.63, 95% CI, 0.48-0.83), and a potential effect on ovarian cancer risk (OR(adj) 0.62, 95% CI, 0.33-1.18; OR(clustered) 0.62, 95% CI, 0.47-0.83). Thus, the 936_C>T polymorphism appears to modify disease risks in BRCA1 carriers.

The methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and cancer risk: The Croatian case–control study

OBJECTIVES

Methylation abnormalities appear to be important for the pathogenesis of many cancer types. Since methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in the methylation process catalyzing reduction of 5,10-methylenetetrahydrofolate to 5-methyl-tetrahydrofolate, C677T polymorphism, which decreases enzyme activity, may be associated with cancer susceptibility. The aim of this work was to investigate the distribution of MTHFR C677T polymorphism between various types of cancer and cancer-free controls and to assess if there is a difference in frequency.

MATERIALS AND METHODS

269 Cancer cases (95 prostate cancer, PC; 81 head and neck, HN; and 93 breast cancers, BC) and 102 healthy controls, free of cancer, were genotyped for C677T MTHFR polymorphism using the PCR-RFLP method.

RESULTS

There was no overall difference in C677T genotype distribution between total cancer cohort and controls (p=0.064). However, a significant difference and protective OR was found for the C/T genotype (OR=0.574, 95% CI=0.352-0.935). In a comparison of different cancer types and respective controls, genotype frequencies were significantly different between head and neck carcinoma and controls (p=0.004), again with protective role of C/T genotype (OR=0.356, 95% CI=0.189-0.671). Moderate overrepresentation of C/T was found in respective male controls when compared with prostate cancer patients (p value was 0.074 for C/T vs. C/C comparison). The OR for heterozygous C/T genotype in prostate cancer group was 0.404, pointing to its putative protective role. Genotype and allelic frequencies did not differ significantly between 93 breast cancer patients and their 65 age-matched female controls.

CONCLUSION

Our data indicate that the C677T MTHFR polymorphism does not significantly contribute to the inherited genetic susceptibility to breast and prostate cancer, while we show some evidence for possible genetic contribution of this polymorphism to the development of head and neck carcinoma.

Methylenetetrahydrofolate reductase (MTHFR) and breast cancer risk: a nested-case-control study and a pooled meta-analysis

BACKGROUND

A reduced activity of methylenetetrahydrofolate reductase (MTHFR) due to frequent C677T polymorphism affects DNA synthesis, repair and methylation and may be implicated in breast cancer risk.

METHODS

We conducted a nested case-control study within a phase III prevention trial of tamoxifen. After a median follow-up of 81.2 months, 79 of the 5,408 hysterectomised women aged 35-70 years, who had received either tamoxifen 20 mg/day or placebo for 5 years, developed breast cancer. A total of 46 breast cancer cases and 80 unaffected controls matched to treatment allocation, years from randomization (+/-2 years) and age at randomization (+/-5 years), underwent genotyping for MTHFR C677T polymorphism using real time PCR.

RESULTS

The MTHFR 677 genotype frequencies for CC, CT, TT in breast cancer cases were 30%, 44% and 26%, respectively, and 35%, 51%, 14% in controls. We observed a borderline significant odds ratio of 2.51 (95% CI, 0.96-6.55) of breast cancer in subjects with 677TT genotype, with no further association after stratifying for age and treatment group. A meta-analysis of 18 studies, including our own, showed an increased risk of breast cancer in premenopausal women with 677TT genotype, with an odds ratio of 1.42 (95% CI, 1.02-1.98).

CONCLUSIONS

Our study lends support to a positive association between the MTHFR variant homozygous allele 677TT and breast cancer risk. Additional studies are warranted to provide further insight into the role of folate metabolism deficiency and breast cancer.

Integrin beta3 Leu33Pro polymorphism increases BRCA1-associated ovarian cancer risk

Integrins are heterodimeric transmembrane glycoproteins that function as key adhesion and cell signalling receptors. A functional polymorphism in the integrin beta3 subunit encoded by the ITGB3 gene, Leu33Pro, has been shown to modify a variety of traits of beta3-expressing cells. To analyse the role of this functional polymorphism in modifying BRCA1-associated ovarian and breast cancer risks, a case-control study was performed among Polish BRCA1 mutation carriers including 319 breast cancer cases, 146 ovarian cancer cases and 290 controls unaffected by breast and ovarian cancer, in situ breast cancer or any other kind of cancer. Genotyping analysis was performed using PCR-based restriction fragment length polymorphism analysis. Odds ratios were calculated using univariate and multivariate logistic regression, taking into account a series of confounding variables, including the presence of related study subjects, that potentially could have biased any association. The results revealed that the ITGB3_Leu33Pro polymorphism was associated with a 2.5-fold increased risk of ovarian cancer, whereas no association with breast cancer risk was found. Thus, it appears that the ITGB3_Leu33Pro polymorphism may potentially increase the risk of ovarian cancer in Polish women with an inherited BRCA1 mutation.