Folate and carcinogenesis: developing a unifying hypothesis

Activation of progesterone receptor is essential for folic acid-regulated cancer cell proliferation and migration

We previously demonstrated that activation of progesterone receptor (PR) is essential for folic acid (FA)-inhibited proliferation in colorectal cancer cell lines. In the present study, we further investigated whether the requirement of PR activation for the FA-regulated cell proliferation and migration is a general phenomenon for all cancer cell lines or specific for colorectal cancer cell lines only. Initially, we examined the expression of PR in various cancer cell lines using Western blot analyses and RT-PCR technique, and then investigated the effects of FA on these cancer cell lines. Our data showed that the effects of FA on proliferation and migration only occurred in the PR positive (+) cancer cell lines, but not the PR negative (-) cancer cell lines, and these effects were abolished by pre-treatment with the PR specific inhibitor, Org 31710. On the other hand, FA significantly reduced the proliferation and migration in the PR (-) cancer cell lines transfected with PR pcDNA. However, FA did not significantly affect the proliferation and migration in the PR-transefected Hep-3B cell line, which does not express endogenous PR and FA receptor (FR). Since we previously showed that FA-regulated proliferation in colorectal and breast cancer cell lines through the cSrc-mediated pathway, we conducted immunoprecipitation assay to demonstrate that PR formed a complex with FR and cSrc, but FR did not directly associate with cSrc. Taken together, these findings suggest that the requirement of PR activation for the FA-regulated cell proliferation and migration is a general phenomenon for all cancer cell lines.

The Role of Circulating Protein and Metabolite Biomarkers in the Development of Pancreatic Ductal Adenocarcinoma (PDAC): A Systematic Review and Meta-analysis

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) has a poor prognosis, and this is attributed to it being diagnosed at an advanced stage. Understanding the pathways involved in initial development may improve early detection strategies. This systematic review assessed the association between circulating protein and metabolite biomarkers and PDAC development.

METHODS

A literature search until August 2020 in MEDLINE, EMBASE, and Web of Science was performed. Studies were included if they assessed circulating blood, urine, or salivary biomarkers and their association with PDAC risk. Quality was assessed using the Newcastle-Ottawa scale for cohort studies. Random-effects meta-analyses were used to calculate pooled relative risk.

RESULTS

A total of 65 studies were included. Higher levels of glucose were found to be positively associated with risk of developing PDAC [n = 4 studies; pooled relative risk (RR): 1.61; 95% CI: 1.16-2.22]. Additionally, an inverse association was seen with pyridoxal 5'-phosphate (PLP) levels (n = 4 studies; RR: 0.62; 95% CI: 0.44-0.87). Meta-analyses showed no association between levels of C-peptide, members of the insulin growth factor signaling pathway, C-reactive protein, adiponectin, 25-hydroxyvitamin D, and folate/homocysteine and PDAC risk. Four individual studies also reported a suggestive positive association of branched-chain amino acids with PDAC risk, but due to differences in measures reported, a meta-analysis could not be performed.

CONCLUSIONS

Our pooled analysis demonstrates that higher serum glucose levels and lower levels of PLP are associated with risk of PDAC.

IMPACT

Glucose and PLP levels are associated with PDAC risk. More prospective studies are required to identify biomarkers for early detection.

The role of nutrition in space exploration: Implications for sensorimotor, cognition, behavior and the cerebral changes due to the exposure to radiation, altered gravity, and isolation/confinement hazards of spaceflight

Multi-year crewed space exploration missions are now on the horizon; therefore, it is important that we understand and mitigate the physiological effects of spaceflight. The spaceflight hazards-radiation, isolation, confinement, and altered gravity-have the potential to contribute to neuroinflammation and produce long-term cognitive and behavioral effects-while the fifth hazard, distance from earth, limits capabilities to mitigate these risks. Accumulated evidence suggests that nutrition has an important role in optimizing cognition and reducing the risk of neurodegenerative diseases caused by neuroinflammation. Here we review the nutritional perspective of how these spaceflight hazards affect the astronaut's brain, behavior, performance, and sensorimotor function. We also assess potential nutrient/nutritional countermeasures that could prevent or mitigate spaceflight risks and ensure that crewmembers remain healthy and perform well during their missions. Just as history has taught us the importance of nutrition in terrestrial exploration, we must understand the role of nutrition in the development and mitigation of spaceflight risks before humans can successfully explore beyond low-Earth orbit.

Vitamin B6, vitamin B12 and methionine and risk of pancreatic cancer: a meta-analysis

Background

Nutrients involved in one-carbon metabolism may play a key role in pancreatic carcinogenesis. The aim of this study was to examine the association between pancreatic cancer risk and intake or blood levels of vitamins B6, B12 and methionine via meta-analysis.

Methods

A systematic search was performed in PubMed, Web of Knowledge and Chinese National Knowledge Infrastructure (CNKI) up to April 2020 to identify relevant studies. Risk estimates and their 95% confidence intervals (CIs) were retrieved from the studies and combined by a random-effect model.

Results

A total of 18 studies were included in this meta-analysis on the association of vitamin B6, B12 and methionine with pancreatic cancer risk. The combined risk estimate (95% CI) of pancreatic cancer for the highest vs lowest category of vitamin B6 intake and blood pyridoxal 5′-phosphate (PLP, active form of vitamin B6) levels was 0.63 (0.48–0.79) and 0.65 (0.52–0.79), respectively. The results indicated a non-linear dose-response relationship between vitamin B6 intake and pancreatic risk. Linear dose–response relationship was found, and the risk of pancreatic cancer decreased by 9% for every 10 nmol/L increment in blood PLP levels. No significant association were found between pancreatic cancer risk and vitamin B12 intake, blood vitamin B12 levels, methionine intake and blood methionine levels.

Conclusion

Our study suggests that high intake of vitamin B6 and high concentration of blood PLP levels may be protective against the development of pancreatic cancer. Further research are warranted to confirm the results.

Circulating unmetabolized folic acid and 5-methyltetrahydrofolate and risk of breast cancer: a nested case-control study

BACKGROUND/OBJECTIVES

Folates found in natural foods are thought to protect against cancer. However, folic acid (FA), a synthetic form of folate used in supplements and fortified foods, may increase breast cancer risk if present in unmetabolized form (UMFA) in the circulation. This study examined the associations of serum UMFA and 5-methyltetrahydrofolate (5-mTHF), the predominant form of circulating folate, with breast cancer risk.

SUBJECTS/METHODS

We conducted a nested case-control study in a prospective cohort. In total, 553 cases of invasive breast cancer, diagnosed before mandatory FA fortification of grain in the US in 1998, were individually-matched to 1059 controls. Serum UMFA and 5-mTHF were measured using liquid chromatography-tandem mass spectrometry in stored serum samples, and 5-mTHF was corrected for storage degradation.

RESULTS

Serum UMFA was not associated with breast cancer risk: the percentage of women with detectable levels of UMFA was similar in cases and controls (18% and 20%, respectively; p = 0.46). Two tag-SNPs in the promoter region of the FA-metabolizing gene were also not associated with risk. There was a marginally significant inverse association of 5-mTHF_corrected with breast cancer risk (odds ratio for the highest vs. lowest quintile = 0.69, 95% CI = 0.49 to 0.97; p_trend = 0.08).

CONCLUSIONS

Circulating UMFA was not associated with breast cancer risk. These results apply to countries without mandatory FA food fortification. Studies are needed in countries with mandatory fortification, where levels of UMFA are much higher than in our study.

Determinants of folate and vitamin B12 plasma levels in the French E3N-EPIC cohort

PURPOSE

Impaired B vitamin status has been identified as a risk factor for major chronic diseases. This study aims at examining the determinants of plasma folate and vitamin B12 concentrations, considering lifestyle factors and MTHFR polymorphisms.

METHODS

A total of 988 women aged 40-65 years from the French E3N cohort were investigated. Intakes of folate and vitamin B12 were assessed using food frequency questionnaires, and plasma concentrations were measured by microbiological assay. Dietary scores were computed to summarize folate and vitamin B12 dietary sources. MTHFR-C677T and MTHFR-A1298C were determined by Kaspar assay. Pearson's partial correlation coefficients and multivariable linear regression models were used to assess correlations between main determinants and plasma folate and vitamin B12 levels.

RESULTS

The partial correlation coefficient between dietary intakes and plasma folate was 0.19 (p value <0.001) and 0.08 (p value = 0.008) for vitamin B12. Dietary scores were the main determinant of B vitamin plasma concentrations with a percent change per unit increase of 12.64% (p value <0.001) for folate and 7.6% (p value <0.001) for vitamin B12. Homozygous (T/T) or heterozygous (C/T) women for MTHFR-C677T had lower plasma folate concentrations [C/T: -6.48% (p value = 0.038) and T/T: -15.89% (p value <0.001)] compared to women carrying the C/C genotype. Other determinants of B vitamin plasma concentration include: smoking status for folate, and age and hormone replacement therapy for vitamin B12.

CONCLUSIONS

We confirmed previous findings on the role of diet as main determinant of folate and vitamin B12 plasma concentrations. However, the impact of genetic polymorphisms and lifestyle factors on plasma B vitamin concentrations should not be neglected.

Unmetabolized Folic Acid, Tetrahydrofolate, and Colorectal Adenoma Risk

In a randomized trial of folic acid supplementation for the prevention of colorectal adenomas, we previously found indications of increased risk during later treatment and follow-up. This could have been due to the unmetabolized folic acid (UFA) or natural reduced and methylated folates (mF) to which it is metabolized. In post hoc analyses, we measured mF (the sum of 5-methyl-tetrahydrofolate and 4-alfa-hydroxy-5-methyl-THF) and UFA concentrations in the serum of 924 participants. Using binomial regression models with a log link, we assessed the associations between plasma mF or UFA and adenoma occurrence. We found no association between plasma mF or UFA and overall adenoma risk. However, during later follow-up, the prespecified, composite endpoint of high-risk findings (advanced or multiple adenomas) was positively associated with plasma mF (P_{linear trend} = 0.009), with a 58% increased risk for participants in the upper versus lowest quartile. An irregular association was seen with plasma UFA, with suggestions of an inverse trend (P_{linear trend}=0.049). A modest, significant inverse association was also seen between mF and risk of serrated lesions, with a 39% lower risk for upper versus lower quartile participants (P_{linear trend} = 0.03). In conclusion, during the later follow-up period in which folic acid supplementation was previously seen to increase the risk of advanced and multiple adenomas, higher serum mF was associated with a higher risk of multiple and/or advanced adenomas, but no clear indication that UFA played a direct role. There were indications that higher mF was associated with reduced risk of serrated polyps. Cancer Prev Res; 10(8); 451-8. ©2017 AACR.

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.

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.

Folic acid inhibits COLO-205 colon cancer cell proliferation through activating the FRα/c-SRC/ERK1/2/NFκB/TP53 pathway: in vitro and in vivo studies

To investigate the molecular mechanism underlying folic acid (FA)-induced anti-colon caner activity, we showed that FA caused G0/G1 arrest in COLO-205. FA activated the proto-oncogene tyrosine-protein kinase Src (c-SRC)-mediated signaling pathway to enhance nuclear factor of kappa light polypeptide gene enhancer in B-cells (NFκB) nuclear translocation and binding onto the tumor protein p53 (TP53) gene promoter, and up-regulated expressions of TP53, cyclin-dependent kinase inhibitor 1A (CDKN1A) and cyclin-dependent kinase inhibitor 1B (CDKN1B). Knock-down of TP53 abolished FA-induced increases in the levels of CDKN1A and CDKN1B protein and G0/G1 arrest in COLO-205. Knock-down of folate receptor alpha (FRα) abolished FA-induced activations in the c-SRC-mediated pathway and increases in the levels of CDKN1A, CDKN1B and TP53 protein. These data suggest that FA inhibited COLO-205 proliferation through activating the FRα/c-SRC/mitogen-activated protein kinase 3/1 (ERK1/2)/NFκB/TP53 pathway-mediated up-regulations of CDKN1A and CDKN1B protein. In vivo studies demonstrated that daily i.p. injections of FA led to profound regression of the COLO-205 tumors and prolong the lifespan. In these tumors, the levels of CDKN1A, CDKN1B and TP53 protein were increased and von willebrand factor (VWF) protein levels were decreased. These findings suggest that FA inhibits COLO-205 colon cancer growth through anti-cancer cell proliferation and anti-angiogenesis.

Dietary folate intake and breast cancer risk: European prospective investigation into cancer and nutrition

BACKGROUND

There is limited evidence on the association between dietary folate intake and the risk of breast cancer (BC) by hormone receptor expression in the tumors. We investigated the relationship between dietary folate and BC risk using data from the European Prospective Investigation into Cancer and Nutrition (EPIC).

METHODS

A total of 367993 women age 35 to 70 years were recruited in 10 European countries. During a median follow-up of 11.5 years, 11575 women with BC were identified. Dietary folate intake was estimated from country-specific dietary questionnaires. Cox proportional hazards regression models were used to quantify the association between dietary variables and BC risk. BC tumors were classified by receptor status. Subgroup analyses were performed by menopausal status and alcohol intake. Intake of other B vitamins was considered. All statistical tests were two-sided.

RESULTS

A borderline inverse association was observed between dietary folate and BC risk (hazard ratio comparing top vs bottom quintile [HRQ5-Q1] = 0.92, 95% CI = 0.83 to 1.01, P trend = .037). In premenopausal women, we observed a statistically significant trend towards lower risk in estrogen receptor-negative BC (HRQ5-Q1 = 0.66, 95% CI = 0.45 to 0.96, P trend = .042) and progesterone receptor-negative BC (HRQ5-Q1 = 0.70, 95% CI = 0.51 to 0.97, P trend = .021). No associations were found in postmenopausal women. A 14% reduction in BC risk was observed when comparing the highest with the lowest dietary folate tertiles in women having a high (>12 alcoholic drinks/week) alcohol intake (HRT3-T1 = 0.86, 95% CI = 0.75 to 0.98, P interaction = .035).

CONCLUSIONS

Higher dietary folate intake may be associated with a lower risk of sex hormone receptor-negative BC in premenopausal women.

Association of 677 C>T (rs1801133) and 1298 A>C (rs1801131) polymorphisms in the MTHFR gene and breast cancer susceptibility: a meta-analysis based on 57 individual studies

OBJECTIVE

The 677 C>T and 1298 A>C polymorphisms of methylenetetrahydrofolate reductase (MTHFR) gene have been widely reported and considered to have a significant effect on breast cancer risk, but the results are inconsistent. A meta-analysis based on 57 eligible studies was carried out to clarify the role of MTHFR gene polymorphisms in breast cancer.

METHODS AND RESULTS

Eligible articles were identified by searching databases including PubMed, Web of Science, EMBASE, CNKI and CBM for the period up to August 2012. Finally, a total of 57 studies were included in this meta-analysis. Crude ORs with 95% CIs were used to assess the association between the MTHFR polymorphisms and breast cancer risk. The pooled ORs were performed with additive model, dominant model and recessive model, respectively. Subgroup analysis was also performed by ethnicity. The statistical heterogeneity across studies was examined with χ2-based Q-test. A meta-analysis was performed using the Stata 12.0 software. Overall, the 677 C allele was significantly associated with breast cancer risk (OR = 0.942, 95%CI = 0.898 to 0.988) when compared with the 677 T allele in the additive model, and the same results were also revealed under other genetic models. Simultaneously, the 1298 A allele was not associated with the breast cancer susceptibility when compared with the 1298 C allele (OR = 0.993, 95%CI = 0.978 to 1.009). Furthermore, analyses under the dominant, recessive and the allele contrast model yielded similar results.

CONCLUSIONS

The results of this meta-analysis suggest that 677 C>T polymorphism in the MTHFR gene may contribute to breast cancer development. However, the 1298 A>C polymorphism is not significantly associated with increased risks of breast cancer.

Associations of dietary folate, Vitamins B6 and B12 and methionine intake with risk of breast cancer among African American and European American women

African American (AA) women are more likely than European American (EA) women to be diagnosed with breast cancer at younger ages and to develop poor prognosis tumors. However, these racial differences are largely unexplained. Folate and other methyl-group nutrients may be related to breast carcinogenesis, but few studies have examined these associations in AA populations. We examined the associations of dietary intake of these nutrients with breast cancer risk overall, by menopausal and estrogen receptor (ER) status among 1,582 AA (749 cases) and 1,434 EA (744 cases) women using data from a case-control study, the Women's Circle of Health Study. Unconditional multivariable logistic regression models were used to compute odds ratios (ORs) and 95% confidence intervals (CIs) for the association of each nutrient and breast cancer risk. In AA women, inverse associations were observed for natural food folate intake among premenopausal women (fourth vs. first quartile: OR = 0.57, 95% CI, 0.33-1.00; p for trend = 0.06) and for ER-positive tumors (fourth vs. first quartile: OR = 0.58, 95% CI, 0.36-0.93; p for trend = 0.03), whereas in EA women, a positive association was observed for intake of synthetic folate (fourth vs. first quartile: OR = 1.53, 95% CI, 1.06-2.21; p for trend = 0.03). Our findings suggest that natural food folate intake is inversely associated with breast cancer risk and that this association may vary by race, menopausal status or ER status. The finding of an increased risk observed among EA women with the highest intake of synthetic folate from fortified foods warrants further investigation.

Proteomic changes induced by histone demethylase JMJD3 in TNF alpha-treated human monocytic (THP-1) cells

JMJD3, a Jumonji C family histone demethylase, plays an important role in the regulation of inflammation induced by the transcription factor nuclear factor-kappa B (NF-κB) in response to various stimuli. JMJD3 is a histone-3 lysine-27 trimethylation (H3K27me3) demethylase, a histone mark associated with transcriptional repression and activation of a diverse set of genes. The present study assessed stable JMJD3 knockdown (KD)-dependent proteomic profiling in human leukemia monocyte (THP-1) cells to analyze the JMJD3-mediated differential changes of marker expression in inflammatory cells. To analyze the protein expression profile of tumor necrosis factor-alpha (TNF-α)-stimulated JMJD3-kd THP-1 cells, we employed matrix-assisted-laser-desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS). Additionally, Ingenuity Pathways Analysis (IPA) was applied to establish the molecular networks. A comparative proteomic profile was determined in TNF-α-treated both of JMJD3-kd THP-1 cells and THP-1 scrambled (sc) cells. The expression of tripartite motif protein (TRIM5), glutathione peroxidase (GPx), glia maturation factor-γ (GMFG), caspase recruitment domain family, member 14 (CARMA2), and dUTP pyrophosphatase were significantly down-regulated, whereas heat shock protein beta-1 (HspB1) and prohibition were significantly up-regulated in JMJD3-kd THP-1 cells. The molecular and signaling networks of the differentially expressed proteins in JMJD3-kd THP-1 cells were determined by IPA. The molecular network signatures and functional proteomics obtained in this study may facilitate the suppression of different key inflammatory regulators through JMJD3-attenuation, which would be crucial to evaluate potential therapeutic targets and to elucidate the molecular mechanism of JMJD3-kd dependent effects in THP-1 cells.

Micronutrient intake and risk of prostate cancer in a cohort of middle-aged, Danish men

PURPOSE

Micronutrients may protect against prostate cancer. However, few studies have had high-quality assessment of both dietary and supplemental consumption of micronutrients, rendering possible different source-specific effects difficult to discern. This study evaluates associations between intake of vitamin C, E, folate, and beta-carotene and prostate cancer risk, focusing on possible different effects of dietary, supplemental, or total intake and on potential effect modification by alcohol intake and BMI.

METHODS

Danish prospective cohort study of 26,856 men aged 50-64 years with questionnaire-based information on diet, supplements, and lifestyle. Hazard ratios (HRs) for prostate cancer associated with micronutrient intake were calculated using Cox proportional hazard analyses.

RESULTS

During follow-up (1993-2010), 1,571 prostate cancer cases were identified. Supplemental folic acid was inversely associated with prostate cancer risk, notably on a continuous scale [HR 0.88 (95 % CI 0.79-0.98) per 100 μg increase/day]. The risk reduction was largely confined to non-aggressive tumors [HR 0.71 (0.55-0.93) per 100 μg increase/day]. No influence on prostate cancer risk was observed for dietary folate or for the other studied micronutrients, regardless of source. We found no significant effect modification by alcohol intake and BMI in relation to any micronutrient.

CONCLUSION

Our study may indicate an inverse association between folic acid and prostate cancer; however, the inverse association was confined to supplemental folic acid and non-aggressive prostate cancer and may thus be a chance finding. Further studies are warranted to evaluate our findings.

Redefining the impact of nutrition on breast cancer incidence: is epigenetics involved?

Breast cancer incidence is rising worldwide with an increase in aggressive neoplasias in young women. Possible factors involved include lifestyle changes, notably diet that is known to make an impact on gene transcription. However, among dietary factors, there is sufficient support for only greater body weight and alcohol consumption whereas numerous studies revealing an impact of specific diets and nutrients on breast cancer risk show conflicting results. Also, little information is available from middle- and low-income countries. The diversity of gene expression profiles found in breast cancers indicates that transcription control is critical for the outcome of the disease. This suggests the need for studies on nutrients that affect epigenetic mechanisms of transcription, such as DNA methylation and post-translational modifications of histones. In the present review, a new examination of the relationship between diet and breast cancer based on transcription control is proposed in light of epidemiological, animal and clinical studies. The mechanisms underlying the impact of diets on breast cancer development and factors that impede reaching clear conclusions are discussed. Understanding the interaction between nutrition and epigenetics (gene expression control via chromatin structure) is critical in light of the influence of diet during early stages of mammary gland development on breast cancer risk, suggesting a persistent effect on gene expression as shown by the influence of certain nutrients on DNA methylation. Successful development of breast cancer prevention strategies will require appropriate models, identification of biological markers for rapid assessment of preventive interventions, and coordinated worldwide research to discern the effects of diet.

Immunomodulation in young laying hens by dietary folic acid and acute immune responses after challenge with Escherichia coli lipopolysaccharide

We investigated the effects of dietary folic acid (FA) supplementation on immunological parameters in young laying hens under acute conditions of lipopolysaccharide (LPS) challenge. Twenty-four Shaver White laying hens at 24 wk were fed 2 diets in a completely randomized design. The diets were wheat-soybean based, with either 0 or 4 mg of supplemental FA per kilogram of diet. At 32 wk of age, 6 hens from each dietary treatment were injected intravenously with 8 mg/kg of BW of either LPS or saline. Four hours after injection, blood was collected and the hens were euthanized to obtain spleen and cecal tonsils. Heterophil:lymphocyte ratio, CD3+, CD4+, CD8+ T cells, and CD4+:CD8+ cells in the blood and spleen were not affected by dietary FA. Relative to saline-injected hens, LPS-injected hens had fewer (P < 0.05) CD3+, CD4+, CD8+, and CD4+:CD8+ cells in the blood, and no difference was found in the spleen. Total protein, albumin, and globulin were found to be higher (P < 0.05) in FA-supplemented hens compared with the control. However, total protein, albumin, and globulins decreased (P < 0.05) in the LPS-injected hens compared with the saline control. Expression of interleukin (IL)-1β in cecal tonsils decreased (P < 0.05) in FA-supplemented hens, but no dietary influence was found on the expression of other genes in both the spleen and cecal tonsils. Lipopolysaccharide upregulated (P < 0.05) expression of IL-10 and interferon (IFN)-γ in the spleen, and IL-1β, IL-10, and IFN-γ in the cecal tonsils, whereas the expression of Toll-like receptor (TLR)-4 and IL-8 was not influenced by LPS in the spleen and cecal tonsils. There was a diet × challenge interaction for total IgG, and cytokines IL-1β and IL-18 in the spleen as well as IL-18 in the cecal tonsils. In conclusion, there were few interactions of dietary FA and LPS; however, FA increased biochemical constituents, enhanced generation of total IgG, as well as exhibiting pleoitropic effects in inflammatory responses.

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.

Diet, epigenetics, and cancer

Cancer encompasses a highly heterogeneous group of diseases. It has been thought that transition from promotion to progression in carcinogenesis may be driven primarily by epigenetic abnormalities. Diet is known to play crucial roles in cancer etiology and has an important role in epigenetics. Current knowledge in the interrelationship among cancer, nutrition and epigenetics is reviewed.

Folate intake and breast cancer mortality in a cohort of Swedish women

Folate may influence breast cancer development and progression through its role in one-carbon metabolism. However, epidemiologic data on the relation between folate and breast cancer survival are limited. We investigated whether dietary folate intake was associated with survival in 3,116 women diagnosed with breast cancer in the population-based Swedish Mammography Cohort. Participants completed a 67-item food frequency questionnaire in 1987. Cox proportional hazard models were used to calculate hazard ratios (HRs) and 95% confidence intervals (95% CIs) for death from breast cancer and death from any cause. During 25,716 person-years of follow-up from 1987 to 2008, there were 852 deaths with 381 breast cancer deaths. Dietary folate intake was inversely associated with breast cancer and overall mortality. Women in the highest quartile of folate intake had a multivariable HR (95% CI) of death from breast cancer of 0.78 (0.58-1.03) compared to those in the lowest quartile (P (trend) = 0.03). The corresponding HR (95% CI) for death from any cause was 0.79 (0.66-0.96; P (trend) = 0.004). The protective association between dietary folate intake and breast cancer death was strongest among those with ER-negative tumors (HR = 0.42; 95% = CI 0.22-0.79; P (trend) = 0.01) comparing the highest to lowest quartile. Our findings suggest that folate intake before breast cancer diagnosis may improve breast cancer and overall survival. While these findings need to be confirmed in future studies, they do offer assurance that dietary folate intake at the levels observed in our population does not unfavorably affect survival after breast cancer.

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.

Dietary factors and pancreatic cancer: the role of food bioactive compounds

Pancreatic cancer is the fourth leading cause of cancer mortality among both men and women in the United States with a 5-year survival rate of only 4%. Several dietary factors may influence the risk of developing pancreatic cancer and its recurrence. Some of these factors may offer innovative therapies for prevention of this disease. The goal of this review is to provide an overview of pancreatic cancer, as well as current knowledge on the epidemiological, in vitro, in vivo, and clinical studies conducted about this disease using various dietary agents. The main focus is on food-based approaches for preventing this disease particularly, citrus fruits, and foods containing flavonoids, curcumin, folate and vitamin D.

Plasma folate studies in HIV-positive patients at the Lagos university teaching hospital, Nigeria

INTRODUCTION

In various studies globally, the prevalence of anemia in persons with HIV infection range from 10 to 20% at initial presentation, and anemia is diagnosed in 70 to 80% of these patients over the course of HIV disease. The etiology of anemia in this group of patients has not been fully established, thus a need to evaluate the role of plasma folate as a possible etiological factor.

OBJECTIVE

This study was set to determine plasma folate levels in newly diagnosed, treatment naïve, HIV-positive patients, and relate this to other hematological changes.

MATERIALS AND METHODS

A total of 200 participants were recruited for this study, of which 100 were HIV positive, treatment naive patients who were recruited at the point of registration and 100 were HIV-negative subjects (controls). 5 ml of venous blood was collected and plasma extracted for folic acid estimation by HPLC. A full blood count, CD4 and Viral load were estimated.

RESULTS

Mean ages for control and study group were 38 ± 2.3 and 32 ± 1.7 years, respectively. Mean plasma folate concentration among the study group (5.04 μg/l) was significantly lower than that for the control group (15.89 μg/l; P = 0.0002). Prevalence of anemia among the study group was 72% (144 of 200), with a mean hemoglobin (Hb) concentration of 9.5 g/dl compared with mean Hb of 13.0 g/dl among the control group (P = 0.002). Plasma folate correlated positively with CD4 cell count (r = 0.304, P<0.05) and inversely with the viral load (r = -0.566; P<0.05).

CONCLUSION

Plasma folate level is a predictor of anemia in early HIV infections.

Enhanced one-carbon flux towards DNA methylation: Effect of dietary methyl supplements against gamma-radiation-induced epigenetic modifications

Radiation exposure poses a major risk for workers in the nuclear power plants and other radiation related industry. In this context, we demonstrate that gamma-radiation is an efficient DNA demethylating agent and its injurious effect can be minimized by dietary methyl supplements (folate, choline and vitamin B12). To elucidate the possible underlying mechanism(s), male Swiss mice were maintained on normal control diet (NCD) and methyl-supplemented diet (MSD). After 2 weeks of NCD and MSD dietary regimen, we exposed the animals to gamma-radiation (2, 4 and 6Gy) and investigated the profile of downstream metabolites and activity levels of one-carbon (C(1)) flux generating enzymes. In MSD fed and irradiated animals, hepatic folate levels increased (P<0.01), while hepatic homocysteine levels decreased (P<0.01) compared to NCD fed and irradiated animals. Although hepatic folate level increased significantly in MSD fed animals (P<0.01), it showed a decrease in response to high doses of gamma-irradiation. Under these conditions, a marked suppression of S-adenosylmethionine (SAM) levels occurred in NCD fed and irradiated animals, suggesting reduced conversion of homocysteine to SAM. Concomitant with decline in liver SAM Pool, activities of DNA methyltransferase (Dnmt, that methylates DNA) and methionine synthase (MSase, that regenerates methionine from homocysteine) were both decreased in NCD fed and irradiated mice. However, in MSD fed and irradiated mice, they were increased. These results strongly indicated that increased levels of dnmt and MSase may enhance C(1) flux towards DNA methylation reactions in MSD fed animals. These results were confirmed and further substantiated by measuring genomic DNA methylation levels, which were maintained at normal levels in MSD fed and irradiated mice compared to NCD fed and irradiated animals (P<0.01). In conclusion, our results suggest that maintenance of genomic DNA methylation under gamma-radiation stress might be a very dynamic, progressive diet dependent process that could involve increased one-carbon flux through various C(1) metabolites.

Intake of folate, vitamins B6, B12 and methionine and risk of pancreatic cancer in a large population-based case-control study

OBJECTIVE

Folate and other methyl-group nutrients may play a key role in pancreatic carcinogenesis through their effects on DNA integrity. We examined the association between pancreatic cancer and intake of folate, vitamins B(6), B(12) and methionine in a large population-based case-control study.

METHODS

Risk factor data were collected during in-person interviews with 532 pancreatic cancer cases diagnosed in 1995-1999 and 1,701 frequency-matched controls in the San Francisco Bay Area. Dietary history and supplement use were obtained using a semi-quantitative food-frequency questionnaire developed at Harvard University. Adjusted unconditional logistic regression was used to compute odds ratios (OR) and 95% confidence intervals (CI) as estimates of the relative risk.

RESULTS

Total folate intake was inversely associated with pancreatic cancer (5th vs. 1st quintile: OR = 0.67, 95% CI = 0.48-0.93, p (trend) = 0.04). Increased vitamin B(12) from food was positively associated with pancreatic cancer although risk estimates for quintiles 3-5 were similar (5th vs. 1st quintile: OR = 1.9, 95% CI = 1.3-2.6, p (trend) = 0.001). Intake of vitamin B(6) or methionine was not associated with pancreatic cancer risk.

CONCLUSIONS

Our study provided some support for an inverse association between folate intake and pancreatic cancer risk. The increased pancreatic cancer risk with vitamin B(12) intake from food warrants further investigation.

DNA methylation, an epigenetic mechanism connecting folate to healthy embryonic development and aging

Experimental studies demonstrated that maternal exposure to certain environmental and dietary factors during early embryonic development can influence the phenotype of offspring as well as the risk of disease development at the later life. DNA methylation, an epigenetic phenomenon, has been suggested as a mechanism by which maternal nutrients affect the phenotype of their offspring in both honeybee and agouti mouse models. Phenotypic changes through DNA methylation can be linked to folate metabolism by the knowledge that folate, a coenzyme of one-carbon metabolism, is directly involved in methyl group transfer for DNA methylation. During the fetal period, organ-specific DNA methylation patterns are established through epigenetic reprogramming. However, established DNA methylation patterns are not immutable and can be modified during our lifetime by the environment. Aberrant changes in DNA methylation with diet may lead to the development of age-associated diseases including cancer. It is also known that the aging process by itself is accompanied by alterations in DNA methylation. Diminished activity of DNA methyltransferases (Dnmts) can be a potential mechanism for the decreased genomic DNA methylation during aging, along with reduced folate intake and altered folate metabolism. Progressive hypermethylation in promoter regions of certain genes is observed throughout aging, and repression of tumor suppressors induced by this epigenetic mechanism appears to be associated with cancer development. In this review, we address the effect of folate on early development and aging through an epigenetic mechanism, DNA methylation.

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.

Gastric cancer in relation to the intake of nutrients involved in one-carbon metabolism among MTHFR 677 TT carriers

BACKGROUND

DNA methylation is an important epigenetic process for transcriptional control of human genome including those genes involved in cancer initiation and progression. Clinical studies have suggested that biological explanation to the protective effect of some nutrients could be linked with the DNA methylation. Folate is a primary methyl donor nutrient; it has been shown to play a key role in DNA methylation, repair and synthesis, by acting as co-factors and/or substrates in this metabolic pathway. Likewise, activity of a key enzyme, the methylenetetrahydrofolate reductase (MTHFR) has also been shown to influence DNA methylation. Overall, these findings support the notion that dietary intake as well as genetic factors play a role in one-carbon metabolism.

AIM OF THE STUDY

This study is to evaluate the dietary intake of nutrients involved in one-carbon metabolism and the genotype of MTHFR 677 C > T with respect to GC risk.

METHODS

We carried out in January 2004 a population-based case-control study in the metropolitan area of Mexico City. A total of 248 histological confirmed GC patients were recruited from nine tertiary hospitals, along with 478 age and sex-matched controls. Nutrient intake was estimated from food frequency questionnaire; the MTHFR 677C > T genotype was determined by PCR-RFLP analysis.

RESULTS

A significant reduction in diffuse GC risk was observed for MTHFR 677 TT genotype among individuals with high consumption of folate (OR = 0.23; 95% CI 0.06-0.84), choline (OR = 0.55; 95% CI 0.33-0.9) and Vitamin B(6) (OR = 0.59; 95% CI 0.36-0.96) compared to MTHFR 677 CC + CT carriers. Among subjects with low consumption of methionine, a reduced risk of diffuse GC was also detected (OR = 0.40; 95% CI 0.16-0.97). In contrast, carriers of the MTHFR 677 TT genotype with a low consumption of folate had a significant increased risk of intestinal GC (OR = 1.88 95% CI 1.02-3.47). A folate-MTHFR 677 C > T interaction in the borderline of significance (P = 0.055) was detected.

CONCLUSIONS

It is probable that GC prevention requires dietary recommendations according to the individual genotype; nevertheless, the available information to this respect is still very limited.

Vitamin supplement use and risk for breast cancer: the Shanghai Breast Cancer Study

OBJECTIVE

The influence of vitamin supplements on breast cancer risk is unclear and the interactive effects of dietary and supplemental sources are unknown. This study investigated (1) the association between self-reported vitamin supplement use (multivitamin, A, B, C, and E) and breast cancer and (2) the combined effect of vitamin supplements in relation to dietary vitamin intakes on breast cancer risk.

METHODS

The Shanghai Breast Cancer Study was a population-based case-control study conducted in Shanghai in 1996-1998 (Phase I) and 2002-2004 (Phase II). Participants were aged 25-64 (Phase I) and 20-70 years (Phase II). The analyses included 3,454 incident breast cancer cases and 3,474 controls. Unconditional logistic regression models were used to determine adjusted odds ratios (ORs) for breast cancer risk associated with vitamin supplement use.

RESULTS

Overall, breast cancer risk was not related to any vitamin supplement intake. However, a 20% reduction in breast cancer risk was observed with vitamin E supplement use among women with low-dietary vitamin E intake (OR = 0.8; 95% confidence interval (CI), 0.6-1.0). A non-significant 20% risk reduction was observed among vitamin B supplement users with low B dietary intake (OR = 0.8; 95% CI, 0.6-1.1). Frequent use of a vitamin B supplement was adversely associated with breast cancer risk among those with high dietary vitamin B intake (OR = 1.4; 95% CI: 0.9-2.1; P for interaction = 0.07).

CONCLUSIONS

This study suggests that vitamins E and B supplements may confer protection against breast cancer among women who have low dietary intake of those vitamins.

Plasma folate, vitamin B-6, vitamin B-12, and risk of breast cancer in women

BACKGROUND

B vitamins such as folate, vitamin B-6, and vitamin B-12 are coenzymes that are important for DNA integrity and stability. Deficiency in these B vitamins may promote tumor carcinogenesis.

OBJECTIVE

We prospectively evaluated plasma concentrations of folate, pyridoxal 5-phosphate (PLP; the principal active form of vitamin B-6), and vitamin B-12 in relation to breast cancer risk.

DESIGN

We included 848 incident cases of invasive breast cancer identified as of 31 March 2004, and 848 individually matched control subjects from 28 345 women in the Women's Health Study aged > or =45 y who provided blood samples and had no history of cancer and cardiovascular disease at baseline in 1993. Logistic regression controlling for matching factors and other risk factors for breast cancer was used to estimate relative risks (RRs) and 95% CIs. All statistical tests were 2 sided.

RESULTS

Plasma concentrations of folate, PLP, and vitamin B-12 were not associated with overall risk of breast cancer. Women in the highest quintile group relative to those in the lowest quintile had multivariate RRs of 1.42 (95% CI: 1.00, 2.02) for plasma folate (P for trend = 0.21), 0.91 (95% CI: 0.63, 1.30) for plasma PLP (P for trend = 0.48), and 1.29 (95% CI: 0.92, 1.82) for plasma vitamin B-12 (P for trend = 0.18). However, higher plasma folate concentrations were moderately associated with an increased risk of developing premenopausal breast cancer (P for trend = 0.04) and for developing estrogen receptor (ER)-positive or progesterone receptor (PR)-positive breast tumors (P for trend < or = 0.06). Conversely, an inverse association was seen between plasma PLP and postmenopausal breast cancer (P for trend = 0.04).

CONCLUSIONS

Data from this study suggest that B vitamins, including folate, vitamin B-6, and vitamin B-12, may confer little or no reduction in overall risk of developing breast cancer. The observed positive associations of folate status with risk of developing premenopausal breast cancer and ER-positive or PR-positive tumors are unexpected. Additional research is needed to elucidate the role of folate in breast cancer development.

Polymorphisms in one-carbon metabolism and trans-sulfuration pathway genes and susceptibility to bladder cancer

We have previously reported significant inverse associations between bladder cancer risk and dietary intake of vitamins B2, B6, B12, folate and protein in a hospital-based bladder cancer case-control study conducted in Spain (1,150 cases;1,149 controls). Because these dietary factors are involved in the one-carbon metabolism pathway, we evaluated associations between bladder cancer risk and 33 single nucleotide polymorphisms (SNPs) in 8 genes (CBS, CTH, MTHFR, MTR, MTRR, SHMT1, SLC19A1 and TYMS) and interactions with dietary variables involved in this pathway. Two SNPs in the CTH gene were significantly associated with bladder cancer risk. OR (95% CI) for heterozygous and the homozygous variants compared to homozygous wild-type individuals were: 1.37 (1.04-1.80) IVS3-66 A > C and 1.22 (1.02-1.45) IVS10-430 C > T. Because the CTH gene is important for glutathione synthesis, we examined interactions with the GSTM1 gene, which codes for glutathione S-transferase muu. Increased risk for individuals with the IVS10-430 CT or TT genotype was limited to those with the GSTM1 null genotype (p-interaction = 0.02). No other SNPs were associated with risk of bladder cancer. These findings suggest that common genetic variants in the one-carbon pathway may not play an important role in the etiology of bladder cancer. However, our results provide some evidence that variation in glutathione synthesis may contribute to risk, particularly among individuals who carry a deletion in GSTM1. Additional work is needed to comprehensively evaluate genomic variation in CTH and related genes in the trans-sulfuration pathway and bladder cancer risk.

Folate and colorectal cancer: an evidence-based critical review

Currently available evidence from epidemiologic, animal, and intervention studies does not unequivocally support the role of folate, a water-soluble B vitamin and important cofactor in one-carbon transfer, in the development and progression of colorectal cancer (CRC). However, when the portfolio of evidence from these studies is analyzed critically, the overall conclusion supports the inverse association between folate status and CRC risk. It is becoming increasingly evident that folate possesses dual modulatory effects on colorectal carcinogenesis depending on the timing and dose of folate intervention. Folate deficiency has an inhibitory effect whereas folate supplementation has a promoting effect on the progression of established colorectal neoplasms. In contrast, folate deficiency in normal colorectal mucosa appears to predispose it to neoplastic transformation, and modest levels of folic acid supplementation suppress, whereas supraphysiologic supplemental doses enhance, the development of cancer in normal colorectal mucosa. Several potential mechanisms relating to the disruption of one-carbon transfer reactions exist to support the dual modulatory role of folate in colorectal carcinogenesis. Based on the lack of compelling supportive evidence and on the potential tumor-promoting effect, routine folic acid supplementation should not be recommended as a chemopreventive measure against CRC at present.

Folate, vitamin B12 and postmenopausal breast cancer in a prospective study of French women

OBJECTIVE

Adequate folate intake may be important for breast cancer prevention. Its protective effect may be influenced by factors associated with folate metabolism. We sought to evaluate folate intake in relation to breast cancer risk and examine whether the relation is affected by alcohol and intake of vitamin B(2) and B(12).

METHODS

A prospective cohort analysis of folate intake was conducted among 62,739 postmenopausal women in the French E3N cohort who had completed a validated food frequency questionnaire in 1993. During nine years' follow-up, 1,812 cases of pathology-confirmed breast cancer were documented through follow-up questionnaires. Nutrients were categorized in quintiles and energy-adjusted using the regression-residual method. Cox model-derived relative risks (RRs) were adjusted for known breast cancer determinants.

RESULTS

The multivariate RR for extreme quintiles of folate intake was 0.78 (95% CI: 0.67-0.90; p-trend = 0.001) [Median intake for Q(1) = 296 microg/day and Q(5) = 522 microg/day]. There was no evidence to support effect modification by alcohol or B(2) intake. The decreasing trend was most marked in women with higher folate and vitamin B(12 )intake. However, test for interaction was not statistically significant (p = 0.29).

CONCLUSIONS

High folate intake was associated with decreased breast cancer risk. Vitamin B(12) intake may modify this association.

Photodegradation of folic acid during extracorporeal photopheresis

BACKGROUND

Photodegradation of folic acid (FA) by ultraviolet (UV) radiation is a well-documented photochemical reaction, and decreased serum levels of FA have been found in patients receiving photochemotherapy (psoralen plus UVA). During extracorporeal photopheresis (ECP) leucocytes and plasma are subjected to 8-methoxypsoralen (8-MOP) plus UVA.

OBJECTIVES

To investigate whether ECP leads to the photodegradation of FA in the extracorporeal system.

METHODS

In 30 patients undergoing ECP on two consecutive days the FA levels were measured in the extracorporeal collected plasma prior to and after UVA exposure. Healthy donor plasma was exposed to 8-MOP and increasing doses of UVA in vitro. In five patients serum folate levels were determined before and after ECP.

RESULTS

We found a mean reduction of 44% and 46% on the first and second day of treatment, respectively. This effect could be reproduced in vitro: the irradiation of healthy donor plasma with UVA led to a dose-dependent reduction of FA of up to 54.75% at 16 J cm(-2). This was independent of the presence of 8-MOP and the base concentration of 5-methyltetrahydrofolate; minimal changes were observed for vitamin B(12) and homocysteine, not undergoing photodegradation. Serum folate levels did not change significantly before and after ECP.

CONCLUSIONS

We conclude that extracorporeal exposure of plasma to UVA during ECP leads to photodegradation of FA. Further investigations are required to determine the biological effects of folate photoproducts and whether clinically relevant loss of FA might be a consequence of ECP.

Folate, vitamin B(6), and vitamin B(12) intake and the risk of breast cancer among Mexican women

BACKGROUND

High intake of folate, vitamin B(6), and vitamin B(12) have been hypothesized to lower the risk for breast cancer. We conducted a population-based case-control study to evaluate the risk for breast cancer among Mexican women with relatively low vitamin intakes.

METHODS

We included 475 women (median age, 53 years; range, 23-87 years) diagnosed with incident breast cancer through six hospitals in Mexico City and interviewed them to obtain data on breast cancer risk factors and their usual diet using a food frequency questionnaire. We selected 1,391 (median age, 49 years; range, 18-82 years) controls from the Mexico City population using a national sampling frame.

RESULTS

Compared with women in the lowest quartile, the odds ratio for breast cancer for women in the highest quartile of folate intake was 0.64 [95% confidence intervals (CI), 0.45-0.90; P, test for trend = 0.009] and 0.32 (95% CI, 0.22-0.49; P, test for trend < 0.0001) for vitamin B(12) intake. Among postmenopausal women, intakes of folate and vitamin B(12) were associated with a lower risk of breast cancer and those associations were stronger than among premenopausal women. The inverse association of folate and breast cancer was stronger among women who consumed a high level of vitamin B(12) as compared with women consuming diets low in vitamin B(12). No association was observed for vitamin B(6) intake.

CONCLUSIONS

In this population, high intakes of folate and vitamin B(12) were independently associated with decreased breast cancer risk, particularly among postmenopausal women.

A comparison of folic acid deficiency-induced genomic instability in lymphocytes of breast cancer patients and normal non-cancer controls from a Chinese population in Yunnan

We hypothesized that the genomic response to folate deficiency might be different between breast cancer cases and healthy subjects. To test this hypothesis, we performed a comprehensive study on the genotoxic and cytotoxic effects of in vitro folic acid (FA) deficiency on primary human lymphocytes from 19 breast cancer patients and 20 age-matched healthy females from Yunnan, China using the cytokinesis-block micronucleus assay. Lymphocytes from the volunteers were cultured in RPMI1640 medium containing 30, 120 or 240 nM FA for 9 days. The results showed that 30 nM FA was associated with increased frequencies of micronucleated binucleated cell (MNed BNC), nucleoplasmic bridges (NPB), nuclear buds (BUD), apoptosis (APO) and necrosis (NEC) relative to 120 and 240 nM FA (P<0.001) in lymphocytes of case and control groups in vitro, however there were no significant differences between the 120 and 240 nM FA within each sampling group. The case group showed significantly higher frequencies of MNed BNC than control at 120 and 240 nM FA (P<0.05-0.001) but not at 30 nM FA (P=0.052). NEC was significantly higher in breast cancer group than control at all concentrations of FA (P<0.005). FA concentration explained 60, 39, 39, 52 and 71% of the variance of MNed BNC, NPB, BUD, APO and NEC, respectively compared with breast cancer status which only explained 6 and 7% of the variance of MNed BNC and NEC(Two way ANOVA, P<0.0001). Difference of difference analysis showed that breast cancer cases were not abnormally sensitive to the genome-damaging effect of folate deficiency. We concluded that (i) increased concentrations of FA abolished the genome-damaging effect of FA deficiency in lymphocytes of both breast cancer patients and controls to a similar extent and (ii) FA concentration is much more important than breast cancer status in determining genomic instability and cell death.

Genetic and epigenetic interactions between folate and aging in carcinogenesis

Folate is among the most strongly implicated dietary components to convey protection against colon cancer, and diminished folate status is associated with an enhanced risk of colon cancer. Age is also regarded as one of the most important risk factors for colonic carcinogenesis. It is therefore of considerable interest to determine whether the process of aging influences folate metabolism in the colon and whether folate supplementation might prevent the procarcinogenic effects associated with aging. Recent studies in our laboratory demonstrated that the colonic mucosa of elder rats is more susceptible to folate depletion than that of young rats. Depletion of folate results in a shift in the forms of folate in the colon as well as increased uracil incorporation into DNA, a purported mechanism for colonic carcinogenesis. However, modest folate supplementation eliminates evidence of inadequate folate status in the colons of elder rats, suggesting that the relation between age and folate status in the colon might be one mechanism by which aging modulates colorectal cancer risk. Interactions between folate and aging also affect a spectrum of epigenetic and genetic phenomena such as uracil misincorporation, DNA methylation, protein methylation, mitochondrial deletion, and critical gene expression, which could be related to carcinogenesis. Aging and inadequate dietary folate may interact and collectively induce derangements in folate metabolism, thereby provoking subsequent molecular aberrations, which may enhance carcinogenesis. However, folate supplementation appears to reverse these adverse effects of aging, which is potentially of substantial import because the latter is an unmodifiable risk factor.

Effects of dietary folate on the development and progression of mammary tumors in rats

Epidemiologic studies have suggested that dietary intake and blood levels of folate may be inversely related to the risk of breast cancer. However, epidemiologic evidence has not been consistent nor has it provided unequivocal support for this purported inverse relationship. Recent evidence has also raised a concern that folate supplementation may promote carcinogenesis if provided after neoplastic foci are established in the target organ. This study investigated the effect of dietary folate deficiency and supplementation on the development and progression of mammary tumors in the N-methyl-N-nitrosourea (MNU) rat model. Weanling, female Sprague-Dawley rats were fed diets containing 0, 2 (control) or 8 mg folic acid/kg diet during the initiation or the promotion phase of MNU-induced mammary tumorigenesis. At necropsy, all macroscopic mammary tumors were identified and histologically confirmed. Dietary folate deficiency and supplementation provided during the initiation phase did not significantly modulate the development of mammary tumors. In contrast, dietary folate deficiency provided during the promotion phase significantly inhibited the rate of appearance, incidence, mean volume and weight of adenocarcinomas compared with the control and supplemental diets. Folate supplementation provided during the promotion phase did not significantly modulate mammary tumorigenesis compared with the control group. These data indicate that moderate folate deficiency inhibits, whereas dietary folate supplementation at four times the basal dietary requirement does not promote, the progression of MNU-induced mammary neoplastic foci in this rat model. However, the limitations associated with the route and dose of MNU administration preclude a definitive conclusion concerning the effect of folate status on the initiation of MNU-induced mammary tumorigenesis.

Modulation of enzymes involved in folate dependent one-carbon metabolism by gamma-radiation stress in mice

The role of various enzymes in folate dependent one-carbon metabolism, which are involved in mobilizing the folate pool for DNA synthesis and the DNA methylation reaction, was investigated. Male Swiss mice (6 weeks old) were subjected to 2, 5 and 7 Gy total body gamma-irradiation. The animals were killed at intervals of 24, 48, 72, 96, 120 and 192 h and the livers were removed. Using a 12000 x g supernatant of 10% tissue homogenate, the activities of dihydrofolate reductase, thymidylate synthase and methylenetetrahydrofolate reductase were determined. The profiles of these folate enzymes were correlated to DNA damage by monitoring p53 protein profile and by comet tail moment analysis. A significant increase in activity of dihydrofolate reductase and thymidylate synthase was observed up to 96 h post-irradiation and the activity subsided thereafter, reaching control value after 192 h. A sharp decline in methylenetetrahydrofolate reductase activity was observed until 192 h after irradiation. Total folates declined by 54% after 96 h following irradiation, and p53 protein concentration in nuclei increased after irradiation, proportionate to radiation dose, and subsided slowly. Thus results indicate a significant drop in total folate levels and rise in p53 protein concentration in the liver after total body gamma-irradiation. It may appear that, under radiation stress conditions, levels of enzymes involved in one-carbon metabolism for DNA repair, are modulated up to a certain time interval, in a dose specific manner. It may also appear that the requirements of folate for nucleotide base synthesis seem to be met at the expense of other one-carbon transfer reactions.

Folate deficiency inhibits the proliferation of primary human CD8+ T lymphocytes in vitro

Folate is required for one-carbon transfer reactions and the formation of purines and pyrimidines for DNA and RNA synthesis. Deficiency of folate can lead to many clinical abnormalities, including macrocytic anemia, cardiovascular diseases, birth defects, and carcinogenesis. The nucleotide imbalance due to folate deficiency causes cell cycle arrest in the S phase and uracil misincorporation into DNA, which may result in DNA double-strand breaks during repair. The role of folate in the immune system has not been fully characterized. We cultured PHA-activated human T lymphocytes in varying concentrations of folate, and measured proliferation, cell cycle, apoptosis, uracil misincorporation, and proportions of Th cells (CD4(+)) and cytotoxic T (CD8(+)) cells. Folate deficiency reduced proliferation of T lymphocytes, induced cell cycle arrest in the S phase, induced apoptosis, and increased the level of uracil in DNA. Folate deficiency also increased the CD4(+) to CD8(+) ratio due to a marked reduction of CD8(+) cell proliferation. Folate or nucleoside repletion of folate-deficient cells rapidly restored T lymphocyte proliferation and normal cell cycle, reduced the DNA uracil content, and lowered the CD4(+) to CD8(+) ratio. These data suggest that folate status may affect the immune system by reducing the capacity of CD8(+) cells to proliferate in response to activation.

MTHFR polymorphisms, dietary folate intake, and breast cancer risk: results from the Shanghai Breast Cancer Study

Folate plays an important role in DNA methylation, synthesis, and repair; intake has been associated with breast cancer. The folate-metabolizing enzyme, methylenetetrahydrofolate reductase (MTHFR) is polymorphic at nucleotides 677 (C-->T) and 1298 (A-->C), resulting in allozymes with decreased activity. We evaluated these two common polymorphisms and their effects on the folate intake and breast cancer risk association in a population-based case-control study of 1144 breast cancer cases and 1236 controls using a PCR-RFLP-based assay. All subjects completed in-person interviews, which included a food frequency questionnaire. Unconditional logistic regression models were used to calculate odds ratios and their 95% confidence intervals, after adjusting for potential confounding factors. Cases and controls were similar in the distribution of MTHFR polymorphisms at codons 677 (41.4% cases and 41.8% controls carried the T allele) and 1298 (17.6% cases and 17.5% controls carried the C allele). An inverse association of breast cancer risk with folate intake was observed in all genotype groups, particularly among subjects with the 677TT genotype. Compared with those with the 677CC genotype and high folate, the adjusted odds ratios (95% confidence intervals) associated with low folate intake were 1.94 (1.15-3.26), 2.17 (1.34-3.51), and 2.51 (1.37-4.60) for subjects who had CC, CT, and TT genotypes (p for interaction, 0.05). No modifying effect of A1298C genotypes on the association of folate intake with breast cancer risk was observed. Results of this study suggest that the MTHFR C677T polymorphisms may modify the association between dietary folate intake and breast cancer risk.

Interaction between Genetic Variations in DNA Repair Genes and Plasma Folate on Breast Cancer Risk

Folate status has been inversely associated with breast cancer risk. Because folate deficiency can cause DNA damage, such as uracil misincorporation, single strand breaks, and double strand breaks, genetic polymorphisms in base excision repair and double strand break repair genes may lead to variation in DNA repair proficiency and modify the effect of folate on breast cancer risk. We prospectively investigated the a priori hypothesized interaction between plasma folate levels and five nonsynonymous polymorphisms in the XRCC1, XRCC2, and XRCC3 genes on breast cancer risk in a nested case-control study within the Nurses' Health Study (712 case-control pairs). Suggestive evidence of interaction was seen for two of these polymorphisms. Compared with the reference group of non-carriers in the lowest quartile of plasma folate, the reduction in risk (66%) was statistically significant among XRCC1 194Trp carriers in the highest quartile (multivariate odds ratio, 0.34; 95% confidence interval, 0.16–0.72). The inverse association between XRCC1 194Trp and breast cancer risk was attenuated by lower plasma folate status. The inverse association between plasma folate level and breast cancer risk was stronger among 194Trp carriers (P, trend = 0.01) than non-carriers (P, trend = 0.09). We also observed that the positive association between the XRCC2 188His allele and breast cancer risk was only significant in women in the lowest plasma folate quartile (carriers versus non-carriers; multivariate odds ratio, 2.04; 95% confidence interval, 1.05–3.97), and this excess risk was abolished among those with higher plasma folate levels. Moreover, the inverse association between plasma folate level and breast cancer risk was stronger among XRCC2 188His carriers (P, trend = 0.004) than non-carriers (P, trend = 0.09). Although none of the statistical tests for interaction was significant, these data give some support for the hypothesis that genetic variations in DNA repair genes may modify the relation between plasma folate level and breast cancer risk.

Physical activity interventions in the prevention and treatment of paediatric obesity: systematic review and critical appraisal

Interventions for prevention and treatment of childhood obesity typically target increases in physical activity and, more recently, reductions in physical inactivity (sedentary behaviour such as television viewing). However, the evidence base for such strategies is extremely limited. The main aim of the present review was to update the systematic review and critical appraisal of evidence in the light of the recent rapid expansion of research in this area. Randomised controlled trials (RCT) that targeted activity or inactivity, that followed up children or adolescents for at least 1 year and that included an objective weight-related outcome measure were included. Trials were appraised using previously published criteria (Harbour & Miller, 2001), and literature search strategies described previously (Reilly et al. 2002) were updated to May 2002. A total of four new RCT, two new systematic reviews and one meta-analysis were identified. The evidence base has increased markedly since the completion of earlier reviews, although high-quality evidence is still lacking. The evidence on childhood obesity prevention is not encouraging, although promising targets for prevention are now clear, notably reduction in sedentary behaviour. There is stronger evidence that targeting activity and/or inactivity might be effective in paediatric obesity treatment, but doubts as to the generalisability of existing interventions, and the clinical relevance of the interventions is unclear. Further research in settings outside the USA is urgently needed, and two ongoing RCT in Scotland are summarised.