Plasma homocysteine as a metabolic risk factor for breast cancer: findings from a case-control study in Taiwan

The Associations between Intakes of One-Carbon Metabolism-Related Vitamins and Breast Density among Young Women

BACKGROUND

Folate is the primary methyl donor and B vitamins are cofactors for one-carbon metabolism that maintain DNA integrity and epigenetic signatures implicated in carcinogenesis. Breast tissue is particularly susceptible to stimuli in early life. Only limited data are available on associations of one-carbon metabolism-related vitamin intake during youth and young adulthood with breast density, a strong risk factor for breast cancer.

METHODS

Over 18 years in the DISC and DISC06 Follow-up Study, diets of 182 young women were assessed by three 24-hour recalls on five occasions at ages 8 to 18 years and once at 25 to 29 years. Multivariable-adjusted linear mixed-effects regression was used to examine associations of intakes of one-carbon metabolism-related vitamins with MRI-measured percent dense breast volume (%DBV) and absolute dense breast volume (ADBV) at ages 25 to 29 years.

RESULTS

Folate intake in youth was inversely associated with %DBV (Ptrend = 0.006) and ADBV (Ptrend = 0.02). These inverse associations were observed with intake during post-, though not premenarche. In contrast, premenarche vitamin B2 intake was positively associated with ADBV (Ptrend < 0.001). Young adult folate and vitamin B6 intakes were inversely associated with %DBV (all Ptrend ≤ 0.04), whereas vitamins B6 and B12 were inversely associated with ADBV (all Ptrend ≤ 0.04).

CONCLUSIONS

Among these DISC participants intakes of one-carbon metabolism-related vitamins were associated with breast density. Larger prospective studies among diverse populations are needed to replicate these findings.

IMPACT

Our results suggest the importance of one-carbon metabolism-related vitamin intakes early in life with development of breast density and thereby potentially breast cancer risk later in life.

GSH-activatable camptothecin prodrug-loaded gold nanostars coated with hyaluronic acid for targeted breast cancer therapy via multiple radiosensitization strategies

Breast cancer has overtaken lung cancer to rank as the top malignant tumor in terms of incidence. Herein, a gold nanostar (denoted as AuNS) is used for loading disulfide-coupled camptothecin-fluorophore prodrugs (denoted as CPT-SS-FL) to form a nanocomposite of AuNS@CPT-SS-FL (denoted as AS), which, in turn, is further encapsulated with hyaluronic acid (HA) to give the final nanoplatform of AuNS@CPT-SS-FL@HA (denoted as ASH). ASH effectively carries the prodrug and targets the CD44 receptor on the surface of tumor cells. The endogenously overexpressed glutathione (GSH) in tumor cells breaks the disulfide bond to activate the prodrug and release the radiosensitizer drug camptothecin (CPT) and the fluorescence imaging reagent rhodamine derivative as a fluorophore (FL). The released FL can track the precise release position of the radiosensitizer camptothecin in tumor cells in real time. The AuNS has strong X-ray absorption and deposition ability due to the high atomic coefficient of elemental Au (Z = 79). At the same time, the AuNS can alleviate the tumor microenvironment (TME) hypoxia through its mild photothermal therapy (PTT). Therefore, through the multiple radiosensitizing effects of GSH depletion, the high atomic coefficient of Au, and hypoxia alleviation, accompanied by the radiosensitizer camptothecin, the designed ASH nanoplatform can effectively induce strong immunogenic cell death (ICD) at the tumor site via radiosensitizing therapy combined with PTT. This work provides a new way of constructing a structurally compact and highly functionalized hierarchical system toward efficient breast cancer treatment through ameliorating the TME with multiple modalities.

Plasma One-Carbon Metabolism-Related Micronutrients and the Risk of Breast Cancer: Involvement of DNA Methylation

Findings of epidemiologic studies focusing on the association between one-carbon metabolism-related micronutrients and breast cancer risk, along with the involvement of DNA methylation, have been inconsistent and incomprehensive. We conducted a case-control study in China including 107 paired participants and comprehensively detected 12 plasma one-carbon metabolism-related micronutrients. Genomic DNA methylation was measured using an 850 K chip and differential methylation probes (DMPs) were identified. Multivariate logistic regression was performed to estimate the associations between plasma micronutrients and the odds of breast cancer. The mediation of selected DMPs in micronutrient breast cancer associations was examined using mediation analyses. An inverse association of plasma folate, methionine cycling-related micronutrients (methionine, S-adenosylmethionine, and S-adenosylhomocysteine), and all micronutrients in the choline metabolism and enzymatic factor groups, and a positive association of methionine cycling-related cysteine with breast cancer risk were observed. Nine micronutrients (methionine, cysteine, SAM, folate, choline, betaine, P5P, vitamins B2, and B12) were related to global or probe-specific methylation levels (p < 0.05). The selected DMPs mediated the micronutrient breast cancer associations with an average mediation proportion of 36.43%. This study depicted comprehensive associations between circulating one-carbon metabolism-related micronutrients and breast cancer risk mediated by DNA methylation.

The Impact of Homocysteine on the Risk of Hormone-Related Cancers: A Mendelian Randomization Study

Background: Aberrant homocysteine level is associated with metabolic disorders and DNA damage, which may be involved in the carcinogenesis of hormone-related cancers, but clinical results of observational studies are controversial. In this study, we investigated the causal relationships between plasma homocysteine and breast cancer (BRCA), prostate cancer (PrCa), and renal cell carcinoma (RCC) using Mendelian randomization (MR) analyses.

Design and Methods: To investigate the putative causal associations between homocysteine and the aforementioned three types of cancers, a two-sample MR study was employed for the study. The primary strategy for summary data analyses was the inverse-variance-weighted (IVW) approach. In our study, the single-nucleotide polymorphisms (SNPs) excluded confounding factors through Linkage Disequilibrium (LD). Phenoscanner tests were the instrumental variants (IVs), homocysteine was the exposure, and BRCA, PrCa, and RCC were the outcomes. Single-nucleotide polymorphisms associated with homocysteine were extracted from a large genome-wide association study (GWAS) meta-analysis of European participants (n = 44,147). Summary Statistics of BRCA were obtained from the latest and largest GWAS meta-analysis comprising of 82 studies from Breast Cancer Association Consortium (BCAC) studies, including women of European ancestry (133,384 cases and 113,789 controls); we obtained summary-level data from the GWAS meta-analysis of PrCa comprising 79,148 cases and 61,106 controls of European ancestry, and the dataset of RCC was a sex-specific GWAS meta-analysis comprising of two kidney cancer genome-wide scans for men (3,227 cases and 4,916 controls) and women (1,992 cases and 3,095 controls) of European ancestry. The MR-Egger and weight median analyses were applied for the pleiotropy test.

Results: The results showed null associations between plasma homocysteine levels and overall BRCA (effect = 0.97, 95% CI: 0.90–1.06, P = 0.543), overall PrCa (effect = 1.01, 95% CI: 0.93–1.11, P = 0.774), RCC in men (effect = 0.99, 95% CI: 0.73–1.34, P = 0.929), and RCC in women (effect = 0.89, 95% CI: 0.61–1.31, P = 0.563).

Conclusions: We found no putative causal associations between homocysteine and risk of BRCA, PrCa, and RCC.

A Computational Approach for Pathway-Based Systemic Drug Influence

Drug repositioning is a well-known method used to reduce the time, cost, and development risks involved in bringing a new drug to the market. The rapid expansion of high-throughput datasets has enabled computational research that can suggest new potential uses for existing drugs. Some computational methods allow the prediction of potential drug targets of a given disease from a systematic network. Despite numerous efforts, the path of many drugs’ efficacy in the human body remains unclear. Therefore, the present study attempted to understand drug efficacy by systematically focusing on functional gene sets. The purpose of this study was to carry out modeling to identify systemic gene networks (called drug paths) in drug-specific pathways. In our results, we found five different paths for five different drugs.

Time-dependent interactions of blood platelets and cancer cells, accompanied by extramedullary hematopoiesis, lead to increased platelet activation and reactivity in a mouse orthotopic model of breast cancer - implications for pulmonary and liver metastasis

Aging has become a significant risk factor for several diseases, including breast cancer.

Platelet activation and platelet-cancer cell aggregate fractions were found to increase with tumor progression in a mouse model of breast cancer. At advanced stages of tumor development, platelets from mice with breast cancer were hyperreactive to low agonist concentrations and hyporeactive to high ones. Platelet activation and reactivity were strongly associated with breast cancer metastasis in the lungs and extramedullary hematopoiesis in the liver. A greater fraction of platelet aggregates was observed in 4T1-injected mice at the advanced stages of breast cancer. In vitro, platelet activation was elevated after incubation with 4T1 cells, and thrombin-stimulated platelets formed aggregates with 4T1 cells. Neither GPIbα, nor GPIIb/IIIa blocking antibodies, were able to affect platelet-cancer cell aggregation in vitro.

The primed circulating platelets became more sensitive to subthreshold stimuli at advanced stages of tumor development, and the formation of platelet-cancer cell aggregates increased with cancer progression. Our findings demonstrate that the age-associated progression of breast cancer cells is connected with increased platelet functioning, and that it can be manifested by the increased number of metastases and extramedullary hematopoiesis in a time-dependent-manner.

Serum Homocysteine, VEGF and TGF-β1 dynamic change in colorectal cancer patients prior and post-operation

Background: The aim of the study was to evaluate the serum homocysteine (Hcy), vascular endothelial growth factor (VEGF) and transforming growth factor β1 (TGF-β1) dynamic change in colorectal cancer patients pre- and post-operation.

Material and methods: One hundred and eighteen CRC patients treated with surgery (CRC group) and 56 healthy controls (Control group) were included in this work. The serum Hcy, VEGF TGF-β1 were examined by enzymatic cycle and enzyme-linked immunosorbent assay (ELISA) of the two groups. We followed patients for 12 months and out of the 118 CRC patients, 14 patients had recurrent disease. Serum Hcy, VEGF and TGF-β1 were measured before and after surgery and repeated every 2 months.

Results Serum Hcy, VEGF and TGF-β1 were 16.20 ± 4.79 μmol/L, 492.36 ± 97.32 pg/ml, 29.23 ± 7.47 pg/ml for the CRC group and 8.98 ± 3.02 μmol/L, 315.21 ± 56.28 pg/ml, 7.69 ± 2.31 pg/ml for the control groups. Serum Hcy, VEGF and TGF-β1 was significantly (p<0.05) lower after surgery in both recurrent and nonrecurrent CRC patients (p<0.05). Interestingly, serum Hcy, VEGF and TGF-β1 gradually increased with time.

Conclusion Serum Hcy, VEGF and TGF-β1 levels are elevated in CRC patients and may correlated with the post-operative disease recurrence.

Plasma Riboflavin and Vitamin B-6, but Not Homocysteine, Folate, or Vitamin B-12, Are Inversely Associated with Breast Cancer Risk in the European Prospective Investigation into Cancer and Nutrition-Varese Cohort

BACKGROUND

One-carbon metabolism-important for DNA stability and integrity-may play a role in breast carcinogenesis. However, epidemiologic studies addressing this issue have yielded inconsistent results.

OBJECTIVE

We prospectively investigated associations between breast cancer and plasma folate, riboflavin, vitamin B-6, vitamin B-12, and homocysteine in women recruited to the Varese (Italy) cohort of the EPIC (European Prospective Investigation into Cancer and Nutrition) study.

METHODS

We performed a nested case-control study on women aged 35-65 y at recruitment with a median body mass index of 25.3 kg/m(2) who gave blood samples in 1987-1992 and again in 1993-1998. Breast cancer cases identified by 31 December 2009 were individually matched to controls. RRs of breast cancer (and subtypes defined by hormone receptor status) with 95% CIs were estimated by unconditional logistic regression, controlling for matching factors and breast cancer risk factors.

RESULTS

After a median of 14.9 y, 276 breast cancer cases were identified and matched to 276 controls. Increasing plasma vitamin B-6 was associated with decreased risk of overall (RR: 0.78; 95% CI: 0.63, 0.96 for 1-SD increase), premenopausal (RR: 0.66; 95% CI: 0.48, 0.92 for 1-SD increase), estrogen receptor-positive (RR: 0.79; 95% CI: 0.63, 1.00 for 1-SD increase), and progesterone receptor-positive (RR: 0.72; 95% CI: 0.55, 0.95 for 1-SD increase) breast cancers. Increased plasma vitamin B-6 was also associated with decreased breast cancer risk in alcohol consumers (≥7 g/d) compared with consumption of <7 g/d or nonconsumption (RR: 0.71; 95% CI: 0.51, 0.99). High plasma riboflavin was associated with significantly lower risk in premenopausal women (RR: 0.45; 95% CI: 0.21, 0.94; highest compared with the lowest quartile, P trend = 0.021). Plasma homocysteine, folate, and vitamin B-12 were not associated with breast cancer risk.

CONCLUSIONS

High plasma vitamin B-6 and riboflavin may lower breast cancer risk, especially in premenopausal women. Additional research is necessary to further explore these associations.

Haplotypes of the MTHFR gene are associated with an increased risk of breast cancer in a Han Chinese population in Gansu province

Elevated homocysteine levels are a risk factor for breast cancer, although the mechanism underlying this effect is unknown. Genome-wide association studies were used to systematically identify genetic variants which were significantly associated with the circulating homocysteine concentration. To examine the role of homocysteine-related variants in the occurrence of breast cancer, we investigated the association between these variants and breast cancer in a Han Chinese population. Five variants of genome-wide significant homocysteine-related genes were selected for the analysis in a case-control study, with a total of 487 patients with breast cancer and 605 controls. We found that none of the studied polymorphisms were related to the altered breast cancer risk. In the haplotypic analysis, the 5,10-methylenetetrahydrofolate reductase (MTHFR) haplotypes rs12085006A/rs1999594G/rs1801133C (OR = 3.44, 95% CI = 1.58-7.50, P = 0.0019) and rs12085006A/rs1999594G/rs1801133T (OR = 16.21, 95% CI = 2.19- 120.32, P = 0.0065) were significantly associated with an increased breast cancer risk when compared with the wild-type haplotype. Both of the risky MTHFR haplotypes were correlated with decreased MTHFR gene expression and elevated homocysteine concentrations, indicating a genetic component for hyperhomocysteinemia. The MTHFR haplotypes reconstructed with homocysteine-related variants were associated with the occurrence of breast cancer. This finding further emphasizes the importance of homocysteine metabolism genes in breast carcinogenesis and highlights the interplay of diet, genetics, and human cancers. © 2016 IUBMB Life, 68(7):526-534, 2016.

Long-term stability of cancer biomarkers in human serum: biomarkers of oxidative stress and redox status, homocysteine, CRP and the enzymes ALT and GGT

AIM

Five frequently used biomarkers in cancer research and epidemiological studies were tested for their assay stability upon storage of serum for 12 months at -20 and -70/-80°C.

MATERIALS & METHODS

The biomarker assays include reactive oxygen metabolites (ROM), the total thiol levels (TTL), homocysteine (HCy), C-reactive protein (HS-CRP) and two liver enzymes, alanine aminotransferase (ALT) and γ-glutamyltransferase (GGT).

RESULTS

The assays for ROM, HCy, HS-CRP and GGT were stable in human serum samples at the two temperatures tested. The two other assays TTL and ALT, however, showed statistically significant differences in their stability between -20 and -80°C.

CONCLUSION

Therefore, storage at -80°C is advised to maintain a reliable assay outcome when serum samples have to be stored for longer periods.

Micronutrients Involved in One-Carbon Metabolism and Risk of Breast Cancer Subtypes

Background

Vitamins involved in one-carbon metabolism are hypothesized to influence breast cancer (BC) risk. However, epidemiologic studies that examined associations between B vitamin intake and BC risk have provided inconsistent results. We prospectively examined, in the Italian ORDET cohort, whether B vitamin consumption was associated with risk of BC and BC subtypes.

Methods

After a mean follow-up of 16.5 years, 391 BCs were diagnosed among 10,786 cohort women. B vitamin intakes were estimated from food frequency questionnaires. Cox proportional hazard models adjusted for energy intake and confounders, estimated hazard ratios (HR) with 95% confidence intervals (CIs) for BC according to intake.

Results

RRs were 0.61 (95% CI 0.38–0.97 highest vs. lowest quartile; P trend 0.025) for thiamine; 0.48 (95% CI 0.32–0.71; P trend <0.001) for riboflavin; 0.59 (95% CI 0.39–0.90; P trend 0.008) for vitamin B6, and 0.65 (95% CI 0.44–0.95; P trend 0.021) for folate. As regards risk of BC subtypes, high riboflavin and folate were significantly associated with lower risk of estrogen receptor positive (ER+) and progesterone receptor positive (PR+) cancers, and high thiamine was associated with lower risk of ER-PR- cancers. High riboflavin was associated with lower risk of both HER2+ and HER2- cancers, high folate with lower risk of HER2- disease, and high thiamine with HER2+ disease.

Conclusions

These findings support protective effects of thiamine and one-carbon metabolism vitamins (folate, riboflavin, and vitamin B6) against BC in general; while folate may also protect against ER+PR+ and HER2- disease; and thiamine against ER-PR-, and HER2+ disease.

Folate intake and the risk of breast cancer: a systematic review and meta-analysis

There is conflicting epidemiological evidence on the role of folate and breast cancer risk. We conducted a systematic review and quantitative meta-analysis of folate intake and folate blood levels and the risk of breast cancer. Four electronic databases (Medline, PubMed, Embase, and Current Contents Connect) were searched to April 11, 2014, with no language restrictions for observational studies that measured folate intake or blood levels and the risk of breast cancer. The meta-analysis of dietary folate intake comprising 36 studies with 34,602 cases, and a total sample size of 608,265 showed a decreased risk of breast cancer, with an odds ratio (OR) of 0.84 [95 % confidence interval (CI) 0.77-0.91]. When stratified by menopausal status and by study design, none of the meta-analyses of prospective studies showed any statistically significant decrease in the risk of breast cancer. The meta-analysis of total folate showed no statistically significant association with breast cancer OR of 0.98 (95 % CI 0.91-1.07). There was no significant association between either dietary or total folate intake and breast cancer when stratified by hormonal receptor status. The meta-analysis of blood folate levels found no significant association with the risk of breast cancer, with an OR of 0.86 (95 % CI 0.60-1.25). Breast cancer does not appear to be associated with folate intake, and this did not vary by menopausal status or hormonal receptor status. Folate blood levels also do not appear to be associated with breast cancer risk.

Higher dietary folate intake reduces the breast cancer risk: a systematic review and meta-analysis

Background:

Many epidemiological studies have investigated the association between folate intake, circulating folate level and risk of breast cancer; however, the findings were inconsistent between the studies.

Methods:

We searched the PubMed and MEDLINE databases updated to January, 2014 and performed the systematic review and meta-analysis of the published epidemiological studies to assess the associations between folate intake level, circulating folate level and the overall risk of breast cancer.

Results:

In all, 16 eligible prospective studies with a total of 744 068 participants and 26 205 breast cancer patients and 26 case–control studies with a total of 16 826 cases and 21 820 controls that have evaluated the association between folate intake and breast cancer risk were identified. Pooled analysis of the prospective studies and case–control studies suggested a potential nonlinearity relationship for dietary folate intake and breast cancer risk. Prospective studies indicated a U-shaped relationship for the dietary folate intake and breast cancer risk. Women with daily dietary folate intake between 153 and 400 μg showed a significant reduced breast cancer risk compared with those <153 μg, but not for those >400 μg. The case–control studies also suggested a significantly negative correlation between the dietary folate intake level and the breast cancer risk. Increased dietary folate intake reduced breast cancer risk for women with higher alcohol intake level, but not for those with lower alcohol intake. No significant association between circulating folate level and breast cancer risk was found when the results of 8 identified studies with 5924 participants were pooled.

Conclusions:

Our studies suggested that folate may have preventive effects against breast cancer risk, especially for those with higher alcohol consumption level; however, the dose and timing are critical and more studies are warranted to further elucidate the questions.

Systemic chemotherapy interferes in homocysteine metabolism in breast cancer patients

BACKGROUND

Hyperhomocysteinemia in breast cancer (BC) patients can be a risk factor for thromboembolic events. This study aimed to evaluate homocysteine and its cofators (folic acid and vitamin B12) concentrations and platelet count at diagnosis of BC, 3 and 6 months after the beginning of chemotherapy treatment and to correlate them with clinical data.

METHODS

Thirty-five BC patients were included; blood samples were obtained by venipuncture. Plasmatic Hcy and cofactors concentrations were measured by competitive chemiluminescent enzyme immunoassay method. Platelet count was done using an automated analyzer. Statistical analysis was performed using the software SPSS.

RESULTS

During chemotherapy, homocysteine (P = 0.032) and vitamin B12 (P < 0.001) concentrations increased, while folate and platelets decreased (P < 0.001). Among the clinical data, the menopausal status showed significant positive correlation (P = 0.022) with homocysteine concentration increase.

CONCLUSIONS

Evaluation of homocysteine concentrations during chemotherapy is extremely important because their levels increase during chemotherapy treatment, thus increasing the risk of thromboembolism development.

Plasma total homocysteine level in association with folate, pyridoxine, and cobalamin status among Iranian primary breast cancer patients

Recently the elevated plasma total homocysteine (tHcy) concentration has been concerned as the secondary feature of tumoral proliferation and enhances the likelihood of thrombogenesis in cancer patients. The objective of this study was to determine the associations between folate, cobalamin, and pyridoxine with fasting plasma tHcy concentration in breast cancer (BC) patients. The intake levels of nutrients were assessed using a validated food frequency questionnaire in 141 newly diagnosed BC patients. The plasma tHcy and pyridoxal-5-phosphate were measured using high performance liquid chromatography with fluorescence detector. Plasma tHcy levels were observed to be significantly higher among BC participants with Stage III where the plasma concentrations of folate was also comparatively less (P < 0.05) than other stages. Dietary pyridoxine was even being consumed less at this stage (P < 0.05). The plasma, dietary, and residual variables of folate were inversely correlated with plasma tHcy concentration (P < 0.05). Dietary cobalamin was also associated negatively with tHcy (P < 0.05). The odds ratio of comparing the highest tertile of plasma cobalamin (>394 pmol/l) and folate (>11.4 ng/ml) vs. the lowest categories were associated with reduced odds of high tHcy occurrence with 0.20 (95% confidence interval: 0.04-0.98) and 0.14 (95% confidence interval: 0.03-0.64), respectively. In conclusion, nutrition-related methyl-group insufficiency could lead to imbalance in tHcy metabolism, as a possible cancer marker.

The association between subclinical atherosclerosis and uterine fibroids

Objective(s)

To explore the atherogenic hypothesis of uterine fibroids among Chinese women.

Methods

In a case-control study, 335 patients confirmed by ultrasound or hysterectomy surgery and 539 controls were enrolled between October 1, 2009 and April 1, 2012. Unconditional logistic regressions were used to calculate the odds ratios (ORs) for the associations of subclinical atherogenic and cardiovascular risk parameters with uterine fibroids in the overall case group and hysterectomy-confirmed case group, respectively.

Results

Higher level of ankle-brachial index (ABI) was independently associated with increased odds of uterine fibroids. The odds of UF among women in the highest tertile of ABI were 1.88 times higher (95%CI: 1.17, 3.02, P_trend = 0.008) compared to those in the lowest tertile. The serum concentration of homocysteine was inversely related to fibroids (middle vs. low: OR 0.56, 95%CI: 0.36, 0.85; high vs. low: OR 0.50, 95% CI: 0.32, 0.79; P_trend = 0.002). In the hysterectomy-confirmed group, an inverse association was suggested between high-density lipoprotein cholesterol (HDL-C) and fibroids (OR 0.46, 95% CI: 0.25, 0.84, P_trend = 0.014). Moreover, the effect of homocysteine concentration was not observed in this group.

Conclusion(s)

These findings suggest that women with uterine fibroids might have an increased risk of subclinical atherosclerosis.

Prediagnostic plasma pyridoxal 5'-phosphate (vitamin b6) levels and invasive breast carcinoma risk: the multiethnic cohort

BACKGROUND

Evidence from experimental and epidemiologic studies suggests that vitamin B6 may reduce the risk of breast cancer.

METHODS

We examined the association of prediagnostic plasma concentrations of pyridoxal-5'-phosphate (PLP), an active form of vitamin B6, with postmenopausal breast cancer risk in a case-control study nested in the multiethnic cohort in Hawaii and Southern California, including 706 cases and 706 controls matched on date of birth, ethnicity, study site, date of blood draw, time of blood draw, hours of fasting before blood draw, and use of menopausal hormones. OR and 95% confidence intervals (CI) were calculated using conditional logistic regression models.

RESULTS

Women with plasma PLP concentrations in the highest quartile had a 30% reduced risk of invasive breast cancer (CI: 0.50-0.98) as compared with the women in the lowest PLP quartile (P for trend = 0.02). The association seemed to be limited in cases with hormone receptor-positive tumors (P for heterogeneity = 0.04); and remained unchanged in the analysis restricted to women with blood samples collected more than one year before cancer diagnosis (OR = 0.69; CI: 0.48-0.99; P for trend = 0.03).

CONCLUSIONS

These data suggest that higher circulating levels of vitamin B6 are associated with a reduced risk of invasive postmenopausal breast cancer.

IMPACT

These results, in combination with information from two other prospective studies, suggest a role for vitamin B6 in the prevention of postmenopausal breast cancer. Additional studies are needed to further investigate potential heterogeneity of the vitamin B6 association with breast cancer risk by tumor hormone receptor status.

Dietary intake of vitamin B(6) and risk of breast cancer in Taiwanese women

BACKGROUND

B vitamins, including vitamin B(6), are coenzymes that are important for DNA integrity and stability. Deficiencies in B vitamins may promote tumor carcinogenesis.

METHODS

We examined the association of dietary vitamin B(6) intake with overall breast cancer risk and breast cancers stratified by hormone receptor status. This case-control study included 391 breast cancer cases and 782 control subjects enrolled at the Tri-Service General Hospital in Taipei, Taiwan. Energy-adjusted intake of vitamin B(6) was derived from a food frequency questionnaire. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression.

RESULTS

As compared with women in the lowest tertile, the multivariate-adjusted ORs for breast cancer among women in the second and highest tertiles of vitamin B(6) intake were 0.78 (95% CI, 0.64-2.52) and 0.64 (0.26-0.92), respectively. In addition, higher vitamin B(6) intake was associated with a significantly lower risk of developing ER-negative breast tumors.

CONCLUSIONS

Our findings suggest that higher intake of vitamin B(6) is associated with a reduction in breast cancer risk, particularly ER-negative tumors.

Dietary folate, vitamin B6, vitamin B12 and methionine intake and the risk of breast cancer by oestrogen and progesterone receptor status

Few studies have evaluated the relationship between the consumption of dietary folate and one-carbon metabolism-related nutrients and breast cancer risk defined by oestrogen receptor (ER) and progesterone receptor (PR) status. The objective of the present study was to examine the associations between dietary folate, vitamin B6, vitamin B12, and methionine intake and the risk of breast cancer by ER and PR status among Chinese women in Guangdong. A hospital-based case–control study was conducted from June 2007 to August 2008, with 438 cases and 438 age (5-year interval)- and residence (rural/urban)-matched controls. Dietary intake information was assessed using a validated FFQ administered through a face-to-face interview. Unconditional logistic regression models were used to calculate multivariate-adjusted OR and 95 % CI. A significant inverse association was found between dietary folate and vitamin B6 intake and breast cancer risk. The adjusted OR of the highest v. the lowest quartile were 0·32 (95 % CI 0·21, 0·49; Ptrend < 0·001) for dietary folate and 0·46 (95 % CI 0·30, 0·69; Ptrend < 0·001) for vitamin B6. No associations were observed for vitamin B12 and methionine intake. A significant inverse association between dietary folate intake and breast cancer risk was observed in all subtypes of ER and PR status. These findings suggest that dietary folate and vitamin B6 intakes were inversely associated with breast cancer risk. The inverse association did not differ by ER and/or PR status.

Dietary B vitamin and methionine intakes and breast cancer risk among Chinese women

Methionine, folate, vitamin B(6), vitamin B(12), niacin, and riboflavin intakes may be related to breast carcinogenesis. These associations may vary by breast cancer type. Using the prospective cohort Shanghai Women's Health Study (1997-2008) including 718 Chinese breast cancer cases, the authors evaluated baseline dietary intake of these factors and breast cancer risk and whether the associations varied by menopausal status and estrogen receptor (ER) and progesterone receptor (PR) status. They estimated associations using hazard ratios and 95% confidence intervals from Cox proportional hazards regression models and stratified analyses by menopausal status and ER/PR status. Lowest quantile of intake was used as the comparison group. For postmenopausal women, dietary intakes of methionine and B vitamins were not associated with breast cancer risk. For premenopausal women, higher intake of folate was associated with decreased breast cancer risk (hazard ratio = 0.58, 95% confidence interval: 0.34, 0.99 for the highest vs. lowest quintile of intake). Only niacin intake was associated with ER+/PR+ breast cancer risk (hazard ratio = 1.62, 95% confidence interval: 1.07, 2.46; P for trend = 0.04 for the highest vs. lowest quartile of intake). Findings support the hypothesis that high folate intake may reduce breast cancer risk and that the association may vary by menopausal and ER/PR status.

Vitamin D decreases risk of breast cancer in premenopausal women of normal weight in subtropical taiwan

Background

Evidence for an association between vitamin D status and breast cancer is now more convincing, but is uncertain in subtropical areas like Taiwan. This hospital-based case-control study examined the relationship of breast cancer with vitamin D intake and sunlight exposure.

Methods

A total of 200 incident breast cancer cases in a Taipei hospital were matched with 200 controls by date of interview and menopausal status. Information on risk factors for breast cancer was collected in face-to-face interviews and assessed with reference to vitamin D intake (foods and nutrients) and sunlight exposure. Vitamin D intake was divided into quartiles, and threshold effect was evaluated by comparing Q2–Q4 with Q1.

Results

After controlling for age, education, parity, hormone replacement therapy, body mass index (BMI), energy intake, menopausal status, and daily sunlight exposure, the risk of breast cancer in participants with a dietary vitamin D intake greater than 5 µg per day was significantly lower (odds ratio [OR], 0.48; 95% confidence interval [CI], 0.24–0.97) than that of participants with an intake less than 2 µg per day. In analysis stratified by menopausal status and BMI, both dietary vitamin D and total vitamin D intakes were associated with a protective effect among premenopausal women. There was a significant linear trend for breast cancer risk and dietary vitamin D intake in premenopausal women (P = 0.02). In participants with a BMI lower than 24 kg/m² (ie, normal weight), dietary vitamin D intake was inversely related to breast cancer risk (P for trend = 0.002), and a threshold effect was apparent (Q2–Q4 vs Q1: OR, 0.46; 95% CI, 0.23–0.90).

Conclusions

Vitamin D had a protective effect against breast cancer in premenopausal women of normal weight in subtropical Taiwan, especially an intake greater than 5 µg per day.

Plasma homocysteine and cysteine and risk of breast cancer in women

Homocysteine and cysteine are associated with oxidative damage and metabolic disorders, which may lead to carcinogenesis. Observational studies assessing the association between circulating homocysteine or cysteine and breast cancer are very limited, and findings have been inconsistent. We prospectively evaluated plasma levels of homocysteine and cysteine in relation to breast cancer risk among 812 incident cases of invasive breast cancer and 812 individually matched control subjects from 28,345 women in the Women's Health Study; these women were >or=45 years old, provided blood samples, and had no history of cancer and cardiovascular disease at baseline. Logistic regression controlling for matching factors and risk factors for breast cancer was used to estimate relative risks (RR) and 95% confidence intervals (95% CI). All statistical tests were two sided. Homocysteine levels were not associated with overall risk for breast cancer. However, we observed a positive association between cysteine levels and breast cancer risk; the multivariate RR for the highest quintile group relative to the lowest quintile was 1.65 (95% CI, 1.04-2.61; P for trend = 0.04). In addition, women with higher levels of homocysteine and cysteine were at a greater risk for developing breast cancer when their folate levels were low (P for interaction = 0.04 and 0.002, respectively). Although our study offers little support for an association between circulating homocysteine and overall breast cancer risk, higher homocysteine levels may be associated with an increased risk for breast cancer among women with low folate status. The increased risk of breast cancer associated with high cysteine levels warrants further investigation.

MTHFR polymorphisms, dietary folate intake and breast cancer risk in Chinese women

To evaluate the relationship between dietary folate intake and genetic polymorphisms of 5,10-methylenetetrahydrofolate reductase (MTHFR) with reference to breast cancer risk, we conducted a case-control study with 669 cases and 682 population-based controls in the Jiangsu Province of China. MTHFR C677T and A1298C genotypes were identified using PCR-RFLP (restrictrion fragment length polymorphism) methods. Dietary folate intake was assessed using an 83-item food frequency questionnaire. Odds ratios (ORs) were estimated with an unconditional logistic model. The frequencies of MTHFR C677T C/C, C/T and T/T genotypes were 32.37, 48.88 and 18.75% in cases and 37.66, 48.24 and 14.10% in controls, respectively. The difference in distribution was significant (chi(2)=6.616, P=0.037), the T/T genotype being associated with an elevated OR (adjusted for age, menopausal status, body mass index (BMI), income, work intensity and status of smoking and drinking) for breast cancer (1.62, 95% confidence interval (95% CI): 1.14-2.30). The frequencies of MTHFR A1298C A/A, A/C and C/C were 71.47, 27.08 and 1.44% in cases and 68.11, 30.13 and 1.76% in controls, respectively, with no significant differences being found (chi(2)=1.716, P=0.424). A significant inverse relationship was observed between folate intake and breast cancer risk. Compared with the lowest tertile of folate intake, the adjusted OR for breast cancer in the top tertile was 0.70 (95% CI: 0.53-0.92). However, no significant interaction was observed between folate intake and the MTHFR C677T polymorphism. Among individuals with the MTHFR A1298C A/A genotype, adjusted ORs for breast cancer were 0.89 (0.62-1.27) and 1.69 (1.20-2.36) for the second to the third tertile of folate intake compared with the highest folate intake group (tread test, P=0.0008). The findings of this study suggest that MTHFR genetic polymorphisms and dietary intake of folate may modify susceptibility to breast cancer.

Folate and one-carbon metabolism nutrients from supplements and diet in relation to breast cancer risk

BACKGROUND

Few epidemiologic studies have examined very high intakes of folate and whether consumption of nutrients involved in one-carbon metabolism is associated with breast cancer risk.

OBJECTIVE

We prospectively examined whether the consumption of folate and nutrients involved in one-carbon metabolism (methionine, riboflavin, and vitamins B-6 and B-12) from self-reported intakes of diet (in year before baseline) and supplements (averaged over 10 y before baseline) were associated with the incidence of breast cancer and breast cancer tumor characteristics.

DESIGN

Participants were 35,023 postmenopausal women aged 50-76 y in the VITamins And Lifestyle (VITAL) cohort study; breast cancer was diagnosed in 743 of these women between baseline (2000-2002) and 2006. Cox proportional hazards models were used to estimate multivariable-adjusted relative risks (RRs) and 95% CIs.

RESULTS

Women consuming > or =1272 dietary folate equivalents (DFE)/d of total folate (10-y average) had a 22% decrease in breast cancer risk compared with women consuming < or =345 DFE/d (RR: 0.78; 95% CI: 0.61, 0.99; P for trend = 0.05). A greater benefit was observed for estrogen-receptor (ER) negative than for ER+ breast cancers (RR: 0.38; 95% CI: 0.18, 0.80; P for trend = 0.02; P = 0.02 for the difference between ER- and ER+). Neither current intakes of folate nor current or long-term intakes of other one-carbon nutrients were significantly associated with breast cancer risk. Multivitamin use attenuated the increased risk of breast cancer associated with alcohol drinking (P for interaction = 0.02).

CONCLUSIONS

Our study of predominantly supplement users suggests that high intakes of folate averaged over 10 y do not increase breast cancer risk, but may be protective, particularly against ER- breast cancers.

Association of polymorphisms in one-carbon metabolism genes and postmenopausal breast cancer incidence

The interconversion of folates by the one-carbon metabolism pathway is essential for the synthesis of precursors used in DNA synthesis, repair, and methylation. Perturbations in this pathway can disrupt these processes and are hypothesized to facilitate carcinogenesis. We investigated associations of 25 candidate polymorphisms in nine one-carbon metabolism genes with risk of postmenopausal breast cancer using 502 cases and 505 controls from the Cancer Prevention II Nutrition Cohort. Four single nucleotide polymorphisms (SNP) in three different genes were significantly associated with breast cancer. The nonsynonymous R134K SNP in methylenetetrahydrofolate dehydrogenase/methenyltetrahydrofolate cyclohydrolase/formyltetrahydrofolate synthase [MTHFD1; odds ratio (OR), 1.40; 95% confidence interval (95% CI), 1.06-1.85 for CT + TT] and an intronic SNP in formyltetrahydrofolate dehydrogenase (FTHFD; OR, 2.23; 95% CI, 1.09-4.54 for CC) were associated with a significant increase in risk. Significantly decreased risk was associated with an intronic SNP in FTHFD (OR, 0.75; 95% CI, 0.58-0.98 for CT + CC) and the A360A SNP in cystathionine beta-synthase (CBS; OR, 0.63; 95% CI, 0.41-0.96 for TT). The presence of at least one variant from both the methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C SNPs was also associated with increased risk (OR, 2.16; 95% CI, 1.34-3.48 for 677 CT + TT/1,298 AC + CC). Investigations into interactions of the associated SNPs with each other and with dietary factors yielded inconclusive results. Our findings indicate that genetic variation in multiple one-carbon metabolism genes may influence risk of postmenopausal breast cancer and may involve changes in methyl donor synthesis. However, larger studies are needed to further examine gene/gene and gene/diet interactions in this pathway.

Folate and risk of breast cancer: a meta-analysis

BACKGROUND

Epidemiologic findings are inconsistent concerning risk for breast cancer associated with low folate intake or blood folate levels. We performed a meta-analysis of prospective and case-control studies to examine folate intake and levels in relation to risk of breast cancer.

METHODS

We searched MEDLINE for studies of this association that were published in any language from January 1, 1966, through November 1, 2006. Study-specific risk estimates were pooled by use of a random-effects model. All statistical tests were two-sided.

RESULTS

Folate intake in increments of 200 microg/day was not associated with the risk of breast cancer in prospective studies (estimated summary relative risk [RR] = 0.97, 95% confidence interval [CI] = 0.88 to 1.07, for dietary folate [eight studies; 302,959 participants and 8367 patients with breast cancer], and RR = 1.01, 95% CI = 0.97 to 1.05, for total folate [six studies; 306,209 participants and 8165 patients with breast cancer]) but was statistically significantly inversely associated with risk in case-control studies (estimated summary odds ratio [OR] = 0.80, 95% CI = 0.72 to 0.89, for dietary folate [13 studies; 8558 case patients and 10,812 control subjects], and OR = 0.93, 95% CI = 0.81 to 1.07, for total folate [three studies; 2184 case patients and 3233 control subjects]). High blood folate levels versus low levels were not statistically significantly associated with the risk of breast cancer in prospective studies (OR = 0.81, 95% CI = 0.59 to 1.10 [three studies]) or in case-control studies (OR = 0.41, 95% CI = 0.15 to 1.10 [two studies]). Among the two prospective studies and two case-control studies that stratified by alcohol consumption, high folate intake (comparing the highest with the lowest category) was associated with a statistically significant decreased risk of breast cancer among women with moderate or high alcohol consumption (summary estimate = 0.51, 95% CI = 0.41 to 0.63) but not among women with low or no alcohol consumption (summary estimate = 0.95, 95% CI = 0.78 to 1.15). Few studies examined whether the relation between folate intake and breast cancer was modified by intakes of methionine or vitamins B6 and B12, and the findings were inconsistent.

CONCLUSION

No clear support for an overall relationship between folate intake or blood folate levels and breast cancer risk was found. Adequate folate intake may reduce the increased risk of breast cancer that has been associated with moderate or high alcohol consumption.