Population-level diversity in the association of genetic polymorphisms of one-carbon metabolism with breast cancer risk

Role of apoptosis and autophagy in folic acid-induced cytotoxicity of human breast cancer cells in vitro

Obstacles to the successful treatment of breast cancer patients with chemotherapeutic agents can be overcome with effective new strategies. It is still unclear how folic acid affects the onset and spread of breast cancer. The purpose of this study was to determine how folic acid affected the apoptotic and autophagic pathways of the breast cancer cell lines MCF-7 and MDA-MB-231. In the present study, folic acid was applied to MCF-7 and MDA-MB-231 breast cancer cell lines at different concentrations and for different durations. MTT analysis was used to investigate cytotoxic activity. All groups underwent the Tunel staining procedure to identify apoptosis and the immunofluorescence staining approach to identify the autophagic pathway. 24-hour folic acid values were accepted as the most appropriate cytotoxic dose. In MCF-7, cell cycle arrest was observed in the S phase and MDA-MB-231 G1/G0 phases. When apoptotic TUNEL staining was evaluated in both cell lines, folic acid significantly increased apoptosis. While a significant difference was observed between the groups in terms of Beclin 1 immunoreactivity in the MDA-MB-231 cell line, there was no significant difference in the MCF-7 cell line. In addition, statistical significance was not observed LC3 immunoreactivity in both cell lines. In the study, it was observed that folic acid induced autophagy at the initial stage in the MDA-MB-231 cell line but had no inductive effect in the MCF-7 cell line. In conclusion, our findings showed that folic acid has a potential cytotoxic and therapeutic effect on MCF-7 and MDA-MB-231 breast cancer cell lines.

Genetic polymorphisms and gene expression of one-carbon metabolizing enzymes and their relation to breast cancer

Background

Breast cancer is considered the leading cause of cancer-related death among Egyptian women (15.41%). One of the common BC risk factors is the genetic factor. One-carbon metabolism is one of the pathways reported to increase BC risk by influencing DNA synthesis and methylation. Methyl tetrahydrofolate reductase (MTHFR), thymidylate synthase (TYMS) and DNA methyltransferase (DNMT) enzymes are key enzymes in one-carbon metabolism directly and through influencing folate metabolism. We aimed to study the association of the gene expression level and polymorphisms of MTHER C677T (rs1801133), TYMS (rs45445694), TYMS 3′UTR 1494del6 and ΔDNMT3B − 149C>T with breast cancer risk in a sample of Egyptian women.

Methods

This study was conducted on one hundred female breast cancer patients. Genotyping and gene expression of the MTHFR and TYMS (1494del6, rs45445694) and DNMT3B genes were performed.

Results

There was no significant difference (OR 1.493; 95% CI 0.78–2.84; P = 0.288) in the frequency of the MTHFR (C677T) genotypes between breast cancer patients and control subjects and no significant difference in the frequency of the MTHFR mutant T allele. TYMS tandem repeats showed a significant difference (OR 2.232; CI 1.21–4.12; P = 0.01) in the frequency of the genotype 2R/3R among breast cancer patients and control subjects; however, the frequency of the 2R allele was not significantly different from that of the 3R allele (OR 1.461; 95% CI 0.96–2.21; P = 0.073). TYMS 3′-UTR 1494del6 showed a significant difference in the distribution of (+ 6/ + 6), (+ 6/− 6) and (− 6/− 6) genotypes between the patient and control groups (P ≤ 0.001*), and its corresponding mutant allele showed P value ≤ 0.001, 95% CI = 1.64–3.76 and OR = 2.483. The expression of MTHFR was downregulated by 0.62-fold in all malignant tissues compared to normal adjacent tissues (0.57 ± 0.20, P < 0.001*). On the other hand, no significant difference (P = 0.143) in the expression level of TYMS was found. Gene expression of DNMT3B was upregulated by 1.65-fold in all breast cancerous tissue samples compared with the control normal adjacent tissue with mean ± SD of 1.81 ± 0.63. (P ≤ 0.001*).

Conclusion

The current study showed that the 2R/3R TYMS allele and DNMT3B (− 149C>T) SNP are associated with a high risk of breast cancer and that there is a correlation between the 3′-UTR 1494del6 polymorphism (genotype − 6/− 6) and breast cancer risk. A significant reduction was found in the MTHFR gene expression level in BC compared with control tissues, and the DNMT3B (− 149C>T) SNP did affect the DNMT3B expression level.

Effects of methylenetetrahydrofolate reductase single-nucleotide polymorphisms on breast, cervical, ovarian, and endometrial cancer susceptibilities

Background

Recent studies identifying methylenetetrahydrofolate reductase (MTHFR) polymorphisms associated with breast cancer (BC), ovarian cancer (OC), cervical cancer, and endometrial cancer (EC) have reported conflicting results and been underpowered. To clarify the correlation between MTHFR mutations and these common female malignancies, we conducted a comprehensive meta-analysis incorporating all eligible publications.

Methods

Relevant reports published before January 20, 2020, were retrieved from PubMed, Embase, the Cochrane Library, and the China National Knowledge Infrastructure databases. The odds ratio and 95% confidence interval summaries for the MTHFR 677C/T and 1298A/C polymorphisms in BC, OC, cervical cancer, and EC were estimated.

Results

A total of 171 studies comprising 56,675 cancer cases and 67,559 controls were included. The results showed a markedly elevated risk of cancer susceptibility related to MTHFR 677C/T based on all genetic models. Similarly, we identified a significant correlation between 1298A/C mutation and cancer risk based on overall comparisons among all models, except the heterozygous model. Moreover, subgroup analysis by cancer type revealed a significantly increased risk of BC associated with 677C/T in the five models and of cervical cancer associated with 1298A/C in some models. Based on ethnicity, significant associations were observed between Asian, African, and mixed populations for 677C/T and the Asian population for 1298A/C. With regard to the sample type used for analysis, we detected a positive association between using blood as the DNA source and cancer risk for 677C/T in all genetic models and for 1298A/C in some genetic models. Further stratification of the results revealed that a notably increased risk was associated with the use of polymerase chain reaction-restriction fragment-length polymorphism or TaqMan as the genotyping method, as well as with the use of population-or hospital-based groups as the controls for 677C/T and 1298A/C, respectively.

Conclusion

This meta-analysis suggests that MTHFR 677C/T and 1298A/C polymorphisms correlate with the risk of common gynecological cancers, with these findings potentially applicable for overall comparisons of related data.

A comprehensive meta-analysis and a case-control study give insights into genetic susceptibility of lung cancer and subgroups

Reports of genetic association of polymorphisms with lung cancer in the Indian subcontinent are often conflicting. To summarise and replicate published evidence for association with lung cancer and its subgroups. We performed a meta-analysis of candidate associations on lung cancer, its histological subtypes and smoking status in the Indian subcontinent following PRISMA guidelines. Multiple testing corrections were done by the Benjamini-Hochberg method through assessment of significance at a false discovery rate of 10%. We genotyped and investigated rs1048943/CYP1A1 in a case-control sample from eastern India, followed by its global meta-analysis using a similar protocol. Meta-analysis of 18 variants of 11 genes reported in 39 studies (7630 cases and 8169 controls) showed significant association of rs1048943/CYP1A1 [2.07(1.49-2.87)] and rs4646903/CYP1A1 [1.48(1.93-1.95)] with overall lung cancer risk at 10% FDR, while nominal association (p < 0.05) was observed for del1/GSTT1, del2/GSTM1, rs1695/GSTP1 and rs17037102/ DKK2. Subtype analysis showed a significant association of del1/GSTT1 with adenocarcinoma, rs4646903/CYP1A1 with squamous carcinoma, and rs1048943/CYP1A1 with both. Association of rs4646903/CYP1A1 in smokers and effect modification by meta-regression analysis was observed. Genotyping of rs1048943/CYP1A1 that presented significant heterogeneity (p < 0.1) revealed an association with adenocarcinoma among eastern Indian smokers, while a global meta-analysis in 10458 cases and 10871 controls showed association with lung cancer and its subgroups. This study identified the susceptibility loci for lung cancer and its covariate-subgroups.

Variants of Genes Involved in Metabolism of Folate Among Patients with Breast Cancer: Association of TYMS 3R Allele with Susceptibility to Breast Cancer and Metastasis

Background & Objective:

Breast cancer (BC) is known to be the most prevalent cancer among women. One-carbon metabolism disturbance might play an important role in the etiology of BC. The present study aimed to investigate the thymidylate synthase (TYMS), 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR), and methionine synthase reductase (MTRR) variants as good candidates for studying the role of genetic variants of folate metabolizing enzymes in the risk of BC.

Methods:

The present case-control study includes 100 BC patients and 141 healthy females. The TYMS 2R/3R (rs34743033), MTR c.2756A>G (rs1805087), and MTRR c.66A>G (rs1801394) variants were detected by polymerase chain reaction (PCR), PCR-restriction fragment length polymorphism (RFLP), and a designed amplification-refractory mutation system (ARMS) method, respectively.

Results:

The 3R allele of TYMS enhanced the risk of BC by 2.84-fold (P<0.001). In the presence of TYMS 3R/3R, compared to TYMS 2R/3R, there was a trend toward enhancing the risk of metastasis by 4.15-fold (95% CI: 0.96-17.85, P=0.055). The frequencies of MTR c.2756A>G and MTRR c.66A>G variants were not significantly different among patients and controls.

Conclusion:

We observed that the TYMS 3R is a risk allele for susceptibility to BC and this allele may increase the risk of metastasis in BC patients. .

Association of folate intake and plasma folate level with the risk of breast cancer: a dose-response meta-analysis of observational studies

Epidemiological studies showing the correlation between folate and the breast cancer risk have revealed inconsistent results. Hence, we conducted a dose-response meta-analysis of observational studies to obtain more reliable conclusions. We searched PubMed and Embase for studies published before April 2019 and identified 39 studies on folate intake and 12 studies on plasma folate level. The combined odds ratios (ORs) and 95% confidence intervals (CIs) were extracted to estimate the breast cancer risk. Folate intake was inversely correlated with the breast cancer risk when the highest and lowest categories (OR = 0.85, 95% CI = 0.79-0.92) were compared, and the dose-response result showed that folate intake had a linear correlation with the breast cancer risk. Moreover, a higher folate intake correlated with a lower breast cancer risk in premenopausal women (OR = 0.80, 95% CI = 0.66-0.97), but not in postmenopausal women (OR = 0.94, 95% CI = 0.83-1.06). However, plasma folate levels were not correlated with the breast cancer risk (OR = 0.98, 95% CI = 0.82-1.17). Folate intake was negatively correlated with the breast cancer risk; however, its practical clinical significance requires further study. Furthermore, additional folate supplements should be considered carefully.

MassARRAY-based single nucleotide polymorphism analysis in breast cancer of north Indian population

Background

Breast Cancer (BC) is associated with inherited gene mutations. High throughput genotyping of BC samples has led to the identification and characterization of biomarkers for the diagnosis of BC. The most common genetic variants studied are SNPs (Single Nucleotide Polymorphisms) that determine susceptibility to an array of diseases thus serving as a potential tool for identifying the underlying causes of breast carcinogenesis.

Methods

SNP genotyping employing the Agena MassARRAY offers a robust, sensitive, cost-effective method to assess multiple SNPs and samples simultaneously. In this present study, we analyzed 15 SNPs of 14 genes in 550 samples (150 cases and 400 controls). We identified four SNPs of genes TCF21, SLC19A1, DCC, and ERCC1 showing significant association with BC in the population under study.

Results

The SNPs were rs12190287 (TCF21) having OR 1.713 (1.08–2.716 at 95% CI) p-value 0.022 (dominant), rs1051266 (SLC19A1) having OR 3.461 (2.136–5.609 at 95% CI) p-value 0.000000466 (dominant), rs2229080 (DCC) having OR 0.6867 (0.5123–0.9205 at 95% CI) p-value 0.0116 (allelic) and rs2298881 (ERCC1) having OR 0.669 (0.46–0.973 at 95% CI), p-value 0.035 (additive) respectively. The in-silico analysis was further used to fortify the above findings.

Conclusion

It is further anticipated that the variants should be evaluated in other population groups that may aid in understanding the genetic complexity and bridge the missing heritability.

A meta-analysis and in silico analysis of polymorphic variants conferring breast cancer risk in the Indian subcontinent

Background: Genetic association studies on breast cancer on the Indian subcontinent have yielded conflicting results, and the precise effect of these variants on breast cancer pathogenesis is not known. Methods: Genomic variants, as obtained from selected studies from the Indian subcontinent, were subjected to random-effects and fixed-effect meta-analysis. Functional annotation of the relevant variants was done through a tried and tested in silico pipeline. Results: We found rs4646903/CYP1A1, rs1799814/CYP1A1, rs61886492/GCPII, del2/GSTM1, rs4680/COMT and rs1801394/MTRR to be associated with breast cancer. The del2/GSTM1 holds the association in premenopausal women. Conclusions: This is the first study of its kind from the Indian subcontinent analysing the extent of association of variants across populations followed by their functional annotation in the disease pathway.

C677T and A1298C methylenetetrahydrofolate reductase polymorphisms and breast cancer susceptibility among Latinos: a meta-analysis

BACKGROUND

Previous meta-analyses have shown an ethnic dependency of the C677T and the A1298C methylenetetrahydrofolate reductase (MTHFR) polymorphisms, with no focus on the Latino population. For Latinos, many studies have examined these polymorphisms and breast cancer susceptibility, yielding no concise result. Therefore, we undertook this meta-analysis to determine the effect these polymorphisms have on breast cancer risk for Latinos.

METHODS

PubMed, EBSCO, LILACS, Scopus, and Latin American-specific databases were searched for studies exploring the association between the MTHFR polymorphisms and breast cancer susceptibility in Latinos until January 2019. Genotype distributions were extracted and, depending on the level heterogeneity determined by the ψ²-based Q test and the I² test, fixed-effects or random-effects models were used to calculate pooled odds ratios (ORs) with 95% confidence intervals (95% CIs) for the heterozygous, homozygous, dominant, recessive, and allelic genetic models. No publication bias was detected by the Begg-Mazumdar's test and Egger's test.

RESULTS

Of the 280 retrieved publications, 9 studies were included: 9 for the C677T polymorphism and 5 for the A1298C polymorphism. For the C677T polymorphism, there was an elevated risk for the homozygous (OR 1.42, 95% CI 1.05-1.92), the dominant (OR 1.16, 95% CI 1.02-1.31), the recessive (OR 1.33, 95% CI 1.01-1.75), and the allelic model (OR 1.17, 95% CI 1.03-1.33, p < 0.01). No association between the A1298C polymorphism and the risk to develop breast cancer was determined.

CONCLUSION

The results indicated that, for Latinos, the C677T polymorphism is associated with a significant risk for developing breast cancer, whereas the A1289C polymorphism does not.

Significant association between ERCC2 and MTHR polymorphisms and breast cancer susceptibility in Moroccan population: genotype and haplotype analysis in a case-control study

Background

Genetic determinants of breast cancer (BC) remained largely unknown in the majority of Moroccan patients. The purpose of this study was to explore the association of ERCC2 and MTHFR polymorphisms with genetic susceptibility to breast cancer in Moroccan population.

Methods

We genotyped ERCC2 polymorphisms (rs1799793 (G934A) and rs13181 (A2251C)) and MTHFR polymorphisms (rs1801133 (C677T) and rs1801131 (A1298C)) using TaqMan SNP Genotyping Assays. Genotypes were compared in 151 BC cases and 156 population-matched controls. Allelic, genotypic and haplotype associations with the risk and clinicopathological features of BC were assessed using logistic regression analyses.

Results

ERCC2-rs1799793-AA genotype was associated with high risk of BC compared to wild type genotype (recessive model: OR: 2.90, 95% CI: 1.34–6.26, p = 0.0069) even after Bonferroni correction (p < 0,0125). MTHFR rs1801133-TT genotype was associated with increased risk of BC (recessive model, OR: 2.49, 95% CI: 1.17–5.29, p = 0.017) but the association turned insignificant after Bonferroni correction. For the rest of SNPs, no statistical associations to BC risk were detected.

Significant association with clinical features was detected for MTHFR-rs1801133-TC genotype with early age at diagnosis and familial BC. Following Bonferroni correction, only association with familial BC remained significant. MTHFR-rs1801131-CC genotype was associated with sporadic BC. ERCC2-rs1799793-AA genotype correlated with ER+ and PR+ breast cancer. ERCC2-rs13181-CA genotype was significantly associated large tumors (T ≥ 3) in BC patients. None of these associations passed Bonferroni correction.

Haplotype analysis showed that ERCC2 A-C haplotype was significantly associated with increased BC risk (OR: 3.71, 95% CI: 1.7–8.12, p = 0.0002 and p = 0.0008 before and after Bonferroni correction, respectively) and positive expression of ER and PR in BC patients. ERCC2 G-C haplotype was correlated with PR negative and larger tumor (T4). We did not find any MTHFR haplotypes associated with BC susceptibility. However, the less common haplotype MTHFR T-C was more frequent in young patients and in familial breast cancer, while MTHFR C-C haplotype was associated with sporadic BC form.

Conclusions

Our findings are a first observation of association between ERCC2 SNPs and breast cancer in Moroccan population. The results suggested that ERCC2 and MTHFR polymorphisms may be reliable for assessing risk and prognosis of BC in Moroccan population.

Correlations of EZH2 and SMYD3 gene polymorphisms with breast cancer susceptibility and prognosis

The aim of the present study was to investigate the correlation of enhancer of Zeste homolog 2 (EZH2) and SET and MYND domain containing 3 (SMYD3) gene polymorphisms with breast cancer susceptibility and prognosis. A total of 712 patients with breast cancer and 783 healthy individuals were selected. Normal breast epithelial cells MCF-10A and breast cancer cells MCF-7, MDA-MB-231, T47D, and Bcap-37 were cultured. Polymerase chain reaction (PCR)-restriction fragment length polymorphism method was applied for genotyping. Reverse-transcription quantitative PCR (RT-qPCR) and Western blotting were used to examine EZH2 and SMYD3 expression in breast cancer tissues and cells. The risk factors and prognostic factors for breast cancer were estimated. The C allele of EZH2 rs12670401 (odds ratio (OR) =1.255, 95% confidence interval (95% CI): 1.085-1.452), T allele of EZH2 rs6464926 (OR =1.240, 95% CI: 1.071-1.435), and three alleles of SMYD3 variable number of tandem repeats (VNTRs) (OR =1.305, 95% CI: 1.097-1.552) could increase susceptibility to breast cancer. Combined genotypes of EZH2 rs12670401 (TC + CC) and EZH2 rs6464926 (CT + TT) were associated with breast cancer susceptibility. Breast cancer tissues had higher EZH2 and SMYD3 expression. EZH2 rs12670401, EZH2 rs6464926, age of menarche, and menopausal status were associated with breast cancer susceptibility. Patients with TT genotype of EZH2 rs12670401 or with CC genotype of EZH2 rs6464926 had higher overall survival (OS). EZH2 rs12670401, EZH2 rs6464926, and clinical staging were independent prognostic factors for breast cancer. SMYD3 VNTR polymorphism exhibited no association with susceptibility and prognosis. EZH2 rs12670401 and rs6464926 polymorphisms, EZH2 and SMYD3 expression, clinical staging, lymph node metastasis, human epidermal growth factor receptor-2 (HER2) status, and metastasis may be correlated with breast cancer susceptibility and prognosis.

Genetic susceptibility to breast cancer risk associated with inorganic arsenic exposure

OBJECTIVE

To evaluate whether the association between breast cancer (BC) and inorganic arsenic (iAs) exposure is modulated by selected polymorphisms in iAs metabolism.

METHODS

A population based case-control (1016/1028) study was conducted in Northern Mexico. Urinary arsenic metabolites were measured by High Performance Liquid Chromatography. Metabolites percentages and methylation ratios, were estimated. Genotypes of selected polymorphisms were determined by allelic discrimination. The interaction between polymorphisms and iAs metabolites percentages and methylation ratios on BC was assessed with unconditional logistic regression models.

RESULTS

A significant interaction (p=0.002) between MTR c.2756A>G polymorphism and percentage dimethylarsinic acid (DMA) on BC was found; BC risk related with %DMA was lower in AG+GG carriers than in AA carriers. No other significant interactions were found.

CONCLUSION

MTR c.2756A>G polymorphism may confer protection for BC associated with iAs exposure. Further research is warranted to elucidate the potential involvement of other polymorphisms in iAs-related BC.