Björn Gylling

Low Folate Levels Are Associated with Reduced Risk of Colorectal Cancer in a Population with Low Folate Status

Background: A diet rich in folate is associated with a reduced colorectal cancer risk, whereas the role of circulating levels is less clear. The aim of this study was to relate prediagnostic plasma folate, vitamin B12, and homocysteine concentrations to the risk of colorectal cancer. Methods: This was a prospective case–control study of 331 cases and 662 matched controls nested within the population-based Northern Sweden Health and Disease Study. Median follow-up time from recruitment to diagnosis was 10.8 years. Results: Plasma folate concentrations were positively related to colorectal cancer risk; multivariate odds ratios were 1.62 [95% confidence intervals (CI), 1.08–2.42] and 1.42 (95% CI, 0.94–2.21) for the middle and highest versus lowest tertile, respectively. In subjects with follow-up <10.8 years, a statistically significant doubled risk was observed for the middle and highest versus lowest tertile, whereas findings for longer follow-up times were null. A positive risk relationship was also observed for tumor stage III–IV but not I–II. Plasma vitamin B12 concentrations were inversely associated with rectal cancer risk. Homocysteine was not significantly related to colorectal cancer risk. Conclusions: In this population-based, nested case–control study, low plasma folate concentrations were associated with a reduced colorectal cancer risk. This protective role was mainly observed in subjects with higher tumor stage or shorter follow-up time between recruitment and diagnosis. Low circulating folate status may protect against colorectal cancer or suppress progression of preneoplastic or neoplastic lesions. Impact: These findings may have relevance for the ongoing debate about mandatory folic acid fortification of flour. Cancer Epidemiol Biomarkers Prev; 23(10); 2136–44. ©2014 AACR.

Pre-diagnostic meat and fibre intakes in relation to colorectal cancer survival in the European Prospective Investigation into Cancer and Nutrition

Improvements in colorectal cancer (CRC) detection and treatment have led to greater numbers of CRC survivors, for whom there is limited evidence on which to provide dietary guidelines to improve survival outcomes. Higher intake of red and processed meat and lower intake of fibre are associated with greater risk of developing CRC, but there is limited evidence regarding associations with survival after CRC diagnosis. Among 3789 CRC cases in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort, pre-diagnostic consumption of red meat, processed meat, poultry and dietary fibre was examined in relation to CRC-specific mortality (n 1008) and all-cause mortality (n 1262) using multivariable Cox regression models, adjusted for CRC risk factors. Pre-diagnostic red meat, processed meat or fibre intakes (defined as quartiles and continuous grams per day) were not associated with CRC-specific or all-cause mortality among CRC survivors; however, a marginal trend across quartiles of processed meat in relation to CRC mortality was detected (P 0·053). Pre-diagnostic poultry intake was inversely associated with all-cause mortality among women (hazard ratio (HR)/20 g/d 0·92; 95 % CI 0·84, 1·00), but not among men (HR 1·00; 95 % CI 0·91, 1·09) (P for heterogeneity=0·10). Pre-diagnostic intake of red meat or fibre is not associated with CRC survival in the EPIC cohort. There is suggestive evidence of an association between poultry intake and all-cause mortality among female CRC survivors and between processed meat intake and CRC-specific mortality; however, further research using post-diagnostic dietary data is required to confirm this relationship.

Untangling the role of one-carbon metabolism in colorectal cancer risk: a comprehensive Bayesian network analysis

The role of one-carbon metabolism (1CM), particularly folate, in colorectal cancer (CRC) development has been extensively studied, but with inconclusive results. Given the complexity of 1CM, the conventional approach, investigating components individually, may be insufficient. We used a machine learning-based Bayesian network approach to study, simultaneously, 14 circulating one-carbon metabolites, 17 related single nucleotide polymorphisms (SNPs), and several environmental factors in relation to CRC risk in 613 cases and 1190 controls from the prospective Northern Sweden Health and Disease Study. The estimated networks corresponded largely to known biochemical relationships. Plasma concentrations of folate (direct), vitamin B6 (pyridoxal 5-phosphate) (inverse), and vitamin B2 (riboflavin) (inverse) had the strongest independent associations with CRC risk. Our study demonstrates the importance of incorporating B-vitamins in future studies of 1CM and CRC development, and the usefulness of Bayesian network learning for investigating complex biological systems in relation to disease.

Biomarkers of folate and vitamin B12 and breast cancer risk: Report from the EPIC cohort.

Epidemiological studies have reported inconsistent findings for the association between B vitamins and breast cancer (BC) risk. We investigated the relationship between biomarkers of folate and vitamin B12 and the risk of BC in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Plasma concentrations of folate and vitamin B12 were determined in 2,491 BC cases individually matched to 2,521 controls among women who provided baseline blood samples. Multivariable logistic regression models were used to estimate odds ratios by quartiles of either plasma B vitamin. Subgroup analyses by menopausal status, hormone receptor status of breast tumors (estrogen receptor [ER], progesterone receptor [PR] and human epidermal growth factor receptor 2 [HER2]), alcohol intake and MTHFR polymorphisms (677C > T and 1298A > C) were also performed. Plasma levels of folate and vitamin B12 were not significantly associated with the overall risk of BC or by hormone receptor status. A marginally positive association was found between vitamin B12 status and BC risk in women consuming above the median level of alcohol (ORQ4‐Q1 = 1.26; 95% CI 1.00–1.58; Ptrend = 0.05). Vitamin B12 status was also positively associated with BC risk in women with plasma folate levels below the median value (ORQ4‐Q1 = 1.29; 95% CI 1.02–1.62; Ptrend = 0.03). Overall, folate and vitamin B12 status was not clearly associated with BC risk in this prospective cohort study. However, potential interactions between vitamin B12 and alcohol or folate on the risk of BC deserve further investigation.

Biomarkers of folate and vitamin B12, alcohol intake and breast cancer risk: report from the EPIC cohort

Epidemiological studies have reported inconsistent findings for the association between B vitamins and breast cancer (BC) risk. We investigated the relationship between biomarkers of folate and vitamin B12 and the risk of BC in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Plasma concentrations of folate and vitamin B12 were determined in 2,491 BC cases individually matched to 2,521 controls among women who provided baseline blood samples. Multivariable logistic regression models were used to estimate odds ratios by quartiles of either plasma B vitamin. Subgroup analyses by menopausal status, hormone receptor status of breast tumors (estrogen receptor [ER], progesterone receptor [PR] and human epidermal growth factor receptor 2 [HER2]), alcohol intake and MTHFR polymorphisms (677C > T and 1298A > C) were also performed. Plasma levels of folate and vitamin B12 were not significantly associated with the overall risk of BC or by hormone receptor status. A marginally positive association was found between vitamin B12 status and BC risk in women consuming above the median level of alcohol (ORQ4‐Q1 = 1.26; 95% CI 1.00–1.58; Ptrend = 0.05). Vitamin B12 status was also positively associated with BC risk in women with plasma folate levels below the median value (ORQ4‐Q1 = 1.29; 95% CI 1.02–1.62; Ptrend = 0.03). Overall, folate and vitamin B12 status was not clearly associated with BC risk in this prospective cohort study. However, potential interactions between vitamin B12 and alcohol or folate on the risk of BC deserve further investigation.

Components of One-carbon Metabolism Other than Folate and Colorectal Cancer Risk.

Background: Despite extensive study, the role of folate in colorectal cancer remains unclear. Research has therefore begun to address the role of other elements of the folate-methionine metabolic cycles. This study investigated factors other than folate involved in one-carbon metabolism, i.e., choline, betaine, dimethylglycine, sarcosine, and methionine and relevant polymorphisms, in relation to the risk of colorectal cancer in a population with low intakes and circulating levels of folate. Methods: This was a prospective case–control study of 613 case subjects and 1,190 matched control subjects nested within the population-based Northern Sweden Health and Disease Study. We estimated odds ratios (OR) by conditional logistic regression, and marginal risk differences with weighted maximum likelihood estimation using incidence data from the study cohort. Results: Higher plasma concentrations of methionine and betaine were associated with modest colorectal cancer risk reductions (OR [95% confidence interval {CI}] for highest versus lowest tertile: 0.76 [0.57, 0.99] and 0.72 [0.55, 0.94], respectively). Estimated marginal risk differences corresponded to approximately 200 fewer colorectal cancer cases per 100,000 individuals on average. We observed no clear associations between choline, dimethylglycine, or sarcosine and colorectal cancer risk. The inverse association of methionine was modified by plasma folate concentrations (OR [95% CI] for highest/lowest versus lowest/lowest tertile of plasma methionine/folate concentrations 0.39 [0.24, 0.64], Pinteraction = 0.06). Conclusions: In this population-based, nested case–control study with a long follow-up time from baseline to diagnosis (median: 8.2 years), higher plasma concentrations of methionine and betaine were associated with lower colorectal cancer risk. See Video Abstract at http://links.lww.com/EDE/B83.

One-carbon metabolism biomarkers and genetic variants in relation to colorectal cancer risk by KRAS and BRAF mutation status

Disturbances in one-carbon metabolism, intracellular reactions involved in nucleotide synthesis and methylation, likely increase the risk of colorectal cancer (CRC). However, results have been inconsistent. To explore whether this inconsistency could be explained by intertumoral heterogeneity, we evaluated a comprehensive panel of one-carbon metabolism biomarkers and some single nucleotide polymorphisms (SNPs) in relation to the risk of molecular subtypes of CRC defined by mutations in the KRAS and BRAF oncogenes. This nested case-control study included 488 CRC cases and 947 matched controls from two population-based cohorts in the Northern Sweden Health and Disease Study. We analyzed 14 biomarkers and 17 SNPs in prediagnostic blood and determined KRAS and BRAF mutation status in tumor tissue. In a multivariate network analysis, no variable displayed a strong association with the risk of specific CRC subtypes. A non-synonymous SNP in the CTH gene, rs1021737, had a stronger association compared with other variables. In subsequent univariate analyses, participants with variant rs1021737 genotype had a decreased risk of KRAS-mutated CRC (OR per allele = 0.72, 95% CI = 0.50, 1.05), and an increased risk of BRAF-mutated CRC (OR per allele = 1.56, 95% CI = 1.07, 2.30), with weak evidence for heterogeneity (Pheterogeneity = 0.01). This subtype-specific SNP association was not replicated in a case-case analysis of 533 CRC cases from The Cancer Genome Atlas (P = 0.85). In conclusion, we found no support for clear subtype-specific roles of one-carbon metabolism biomarkers and SNPs in CRC development, making differences in CRC molecular subtype distributions an unlikely explanation for the varying results on the role of one-carbon metabolism in CRC development across previous studies. Further investigation of the CTH gene in colorectal carcinogenesis with regards to KRAS and BRAF mutations or other molecular characteristics of the tumor may be warranted.

Dietary folate intake and pancreatic cancer risk: Results from the European Prospective Investigation into Cancer and Nutrition: Dietary folate intake and pancreatic cancer risk

Pancreatic cancer (PC) has an exceptionally low survival rate and primary prevention strategies are limited. Folate plays an important role in one‐carbon metabolism and has been associated with the risk of several cancers, but not consistently with PC risk. We aimed to investigate the association between dietary folate intake and PC risk, using the standardised folate database across 10 European countries. A total of 477,206 participants were followed up for 11 years, during which 865 incident primary PC cases were recorded. Folate intake was energy‐adjusted using the residual method. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards models. In multivariable analyses stratified by age, sex, study centre and adjusted for energy intake, smoking status, BMI, educational level, diabetes status, supplement use and dietary fibre intake, we found no significant association between folate intake and PC risk: the HR of PC risk for those in the highest quartile of folate intake (≥353 μg/day) compared to the lowest (<241 μg/day) was 0.81 (95% CI: 0.51, 1.31; ptrend = 0.38). In current smokers, a positive trend was observed in PC risk across folate quartiles [HR = 4.42 (95% CI: 1.05, 18.62) for ≥353 μg/day vs. <241 μg/day, ptrend = 0.01]. Nonetheless, there was no significant interaction between smoking and dietary folate intake (pinteraction = 0.99). We found no association between dietary folate intake and PC risk in this large European study.

One-carbon metabolite ratios as functional B-vitamin markers and in relation to colorectal cancer risk: Functional B-vitamin markers and CRC risk

One‐carbon metabolism biomarkers are easily measured in plasma, but analyzing them one at a time in relation to disease does not take into account the interdependence of the many factors involved. The relative dynamics of major one‐carbon metabolism branches can be assessed by relating the functional B‐vitamin marker total homocysteine (tHcy) to transsulfuration (total cysteine) and methylation (creatinine) outputs. We validated the ratios of tHcy to total cysteine (Hcy:Cys), tHcy to creatinine (Hcy:Cre) and tHcy to cysteine to creatinine (Hcy:Cys:Cre) as functional markers of B‐vitamin status. We also calculated the associations of these ratios to colorectal cancer (CRC) risk. Furthermore, the relative contribution of potential confounders to the variance of the ratio‐based B‐vitamin markers was calculated by linear regression in a nested case–control study of 613 CRC cases and 1,190 matched controls. Total B‐vitamin status was represented by a summary score comprising Z‐standardized plasma concentrations of folate, cobalamin, betaine, pyridoxal 5′‐phosphate and riboflavin. Associations with CRC risk were estimated using conditional logistic regression. We found that the ratio‐based B‐vitamin markers all outperformed tHcy as markers of total B‐vitamin status, in both CRC cases and controls. In addition, associations with CRC risk were similar for the ratio‐based B‐vitamin markers and total B‐vitamin status (approximately 25% lower risk for high vs. low B‐vitamin status). In conclusion, ratio‐based B‐vitamin markers were good predictors of total B‐vitamin status and displayed similar associations as total B‐vitamin status with CRC risk. Since tHcy and creatinine are routinely clinically analyzed, Hcy:Cre could be easily implemented in clinical practice.

Heterogeneity of Colorectal Cancer Risk Factors by Anatomical Subsite in 10 European Countries: A Multinational Cohort Study.

Background & Aims Colorectal cancer located at different anatomical subsites may have distinct etiologies and risk factors. Previous studies that have examined this hypothesis have yielded inconsistent results, possibly because most studies have been of insufficient size to identify heterogeneous associations with precision. Methods In the European Prospective Investigation into Cancer and Nutrition study, we used multivariable joint Cox proportional hazards models, which accounted for tumors at different anatomical sites (proximal colon, distal colon, and rectum) as competing risks, to examine the relationships between 14 established/suspected lifestyle, anthropometric, and reproductive/menstrual risk factors with colorectal cancer risk. Heterogeneity across sites was tested using Wald tests. Results After a median of 14.9 years of follow-up of 521,330 men and women, 6291 colorectal cancer cases occurred. Physical activity was related inversely to proximal colon and distal colon cancer, but not to rectal cancer (P heterogeneity = .03). Height was associated positively with proximal and distal colon cancer only, but not rectal cancer (P heterogeneity = .0001). For men, but not women, heterogeneous relationships were observed for body mass index (P heterogeneity = .008) and waist circumference (P heterogeneity = .03), with weaker positive associations found for rectal cancer, compared with proximal and distal colon cancer. Current smoking was associated with a greater risk of rectal and proximal colon cancer, but not distal colon cancer (P heterogeneity = .05). No heterogeneity by anatomical site was found for alcohol consumption, diabetes, nonsteroidal anti-inflammatory drug use, and reproductive/menstrual factors. Conclusions The relationships between physical activity, anthropometry, and smoking with colorectal cancer risk differed by subsite, supporting the hypothesis that tumors in different anatomical regions may have distinct etiologies.