5,10-Methylenetetrahydrofolate reductase polymorphisms and the risk of pancreatic cancer

The Association Between Serum Riboflavin and Flavin Mononucleotide With Pancreatic Cancer: Findings From a Prospective Cohort Study

OBJECTIVES

Vitamin B2 (riboflavin) has a prime role in metabolic reactions imperative to cell cycle and proliferation. We investigated the associations between serum concentrations of riboflavin flavin mononucleotide with the risk of pancreatic cancer in a nested case-control study involving 58 cases and 104 matched controls.

METHODS

The Singapore Chinese Health Study, an ongoing prospective cohort study of 63,257 Chinese Singaporeans. Conditional logistic regression method was used to evaluate these associations with adjustment for potential confounders including the level of education, body mass index, smoking status, alcohol consumption, history of diabetes, serum cotinine and pyridoxal 5'-phosphate, estimated glomerular filtration rate, and total methyl donors (ie, the sum of serum choline, betaine, and methionine).

RESULTS

The risk of pancreatic cancer increased with increasing level of serum riboflavin in a dose-dependent manner, especially in men (Ptrend = 0.003). The odds ratio (95% confidence intervals) of pancreatic cancer for the second and third tertiles of serum riboflavin, compared with the lowest tertile, were 9.92 (1.65-59.77) and 25.59 (3.09-212.00), respectively. This positive association was stronger in individuals with a longer follow-up period (≥7 years).

CONCLUSIONS

The findings suggest a potential role of riboflavin in the development of pancreatic cancer, especially in men.

The association of MTHFR (rs1801133) with hypertension in an indigenous south African population

Aims: The current study sought to investigate the association between the methylenetetrahydrofolate reductase (MTHFR) variant (rs1801133) and the risk of developing hypertension (HTN) in an indigenous South African population.

Methods: A total of 442 participants (hypertensive, n = 279 and non-hypertensive, n = 163) from the indigenous tribe residing in Mthatha, Eastern Cape (South Africa) were recruited. HTN was defined as a systolic (SBP) and diastolic blood pressure (DBP) of ≥130/80 mmHg following American Heart Association guidelines. The genotyping of MTHFR (rs1801133) was assessed using MassARRAY^® System. Thereafter, the association between rs1801133 in various genetic models and HTN was determined by logistic regression model analysis. Furthermore, the interaction between rs1801133 and selected risk factors on HTN was performed using the open-source multifactor dimensionality reduction (MDR).

Results: The low frequency of the T allele (5%) was also observed when compared with the C allele (95%) in both cases and controls. After adjusting for confounding factors (gender, smoking status, BMI, and blood glucose levels), there were no significant associations were observed between rs1801133 and the risk of HTN in all genetic models: genotypic (OR 0.75, 95% CI 0.29–1.95, p = 0.56), dominant (OR 0.86, 95% CI 0.35–2.16, p = 0.75), co-dominant (OR 1.33, 95% CI 0.51–3.48, p = 0.55) and allelic (OR 0.80, 95% CI 0.49–1.62, p = 0.70) in logistic regression analysis. However, a significant interaction was reported among rs1801133, age, and gender (p < 0.0001) with the risk of HTN.

Conclusion: The present study reports on the lack of association between MTHFR (rs1801133) and the risk of HTN in an indigenous South African tribe. However, an interaction between gender, age, and rs1801133 was observed. Thus, future studies with a large sample size are required to further validate these findings.

Validation of genome-wide association study-identified single nucleotide polymorphisms in a case-control study of pancreatic cancer from Taiwan

Background

Due to differences in genetic background, it is unclear whether the genetic loci identified by the previous genome-wide association studies (GWAS) of pancreatic cancer also play significant roles in the development of pancreatic cancer among the Taiwanese population.

Methods

This study aimed to validate the 25 pancreatic cancer GWAS-identified single nucleotide polymorphisms (SNPs) in a case-control study (278 cases and 658 controls) of pancreatic cancer conducted in Taiwan. Statistical analyses were conducted to determine the associations between the GWAS-identified SNPs and pancreatic cancer risk. Gene-environment interaction analysis was conducted to evaluate the interactions between SNPs and environmental factors on pancreatic cancer risk.

Results

Among the 25 GWAS-identified SNPs, 7 (rs2816938 (~ 11 kb upstream of NR5A2), rs10094872 (~ 28 kb upstream of MYC), rs9581943 (200 bp upstream of PDX1) and 4 chromosome 13q22.1 SNPs: rs4885093, rs9573163, rs9543325, rs9573166) showed a statistically significant association with pancreatic cancer risk in the current study. Additional analyses showed two significant gene-environment interactions (between poor oral hygiene and NR5A2 rs2816938 and between obesity and PDX1 rs9581943) on the risk of pancreatic cancer.

Conclusions

The current study confirmed the associations between 7 of the 25 GWAS-identified SNPs and pancreatic risk among the Taiwanese population.

Furthermore, pancreatic cancer was jointly influenced by lifestyle and medical factors, genetic polymorphisms, and gene-environment interaction. Additional GWAS is needed to determine the genetic polymorphisms that are more relevant to the pancreatic cancer cases occurring in Taiwan.

Association of MTHFR gene polymorphisms with pancreatic cancer: meta-analysis of 17 case-control studies

BACKGROUND

Pancreatic cancer (PC) is a seriously malignant tumor with a low 5-year survival rate. The relationship between methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and PC has been reported by several studies. However, the results were controversial. Thus, we conducted a meta-analysis to summarize available data on MTHFR gene and PC.

METHODS

We searched PubMed, Embase, Web of Science, Wanfang, CNKI databases prior to July 2019. Data were analyzed by RevMan 5.3 and STATA 12.0 software. Odds ratio (OR) and 95% confidence interval (CI) were used to evaluate the strength of the association. Subgroup analysis, sensitivity analysis and assessment of publication bias were performed in this study.

RESULTS

Ten articles with 17 reports (10 for C677T, 7 for A1298C) were eligible for inclusion in the meta-analysis (1864 cases and 3165 controls for C677T, and 1488 cases and 1946 controls for A1298C). Our meta-analysis detected that C677T was associated with PC for three genetic models (allele model: OR = 1.24, 95% CI: 1.00-1.53, P = 0.047; recessive model: OR = 1.39, 95% CI: 1.04-1.86, P = 0.027; homozygous model: OR = 1.60, 95% CI: 1.04-2.45, P = 0.034). In the stratified analyses according to ethnicity, source of controls and genotyping method, significant association was observed in genotyping method subgroup. For the A1298C polymorphism, no significant association was observed either in overall analysis or in subgroup analysis under all genetic models.

CONCLUSIONS

MTHFR gene C677T rather than A1298C polymorphism may be associated with PC. Larger sample size studies should be performed to find the association between MTHFR gene and PC.

Genetic polymorphisms and pancreatic cancer risk: A PRISMA-compliant systematic review and meta-analysis

BACKGROUNDS

Previous investigations yielded inconsistent results for the associations between pancreatic cancer (PC) risk and genetic polymorphisms. The study aimed to perform a systematic review and meta-analysis of studies exploring association of some genetic polymorphisms and PC risk.

METHODS

We systematically searched on PubMed and Web of Science for association of genetic polymorphisms and PC risk published from 1969 to January 2019. We computed the multivariate odd ratio (OR) and 95% confidence intervals (CI), comparing different genetic types.

RESULTS

The present meta-analysis showed significant associations between deoxyribonucleic acid (DNA) repair gene (X-ray repair cross-complementing group 1 (XRCC1) Arg399GIn and Arg194Trp, excision repair cross complementation 1 (ERCC1) rs11615 and rs3212986, ERCC2 rs13181) polymorphisms and PC risk.

CONCLUSIONS

Because of the limited sample size and ethnicity enrolled in the present meta-analysis, further larger scaled studies should be performed to demonstrate the association.

The role of the folate pathway in pancreatic cancer risk

BACKGROUND

Pancreatic cancer is the third leading cause of cancer related deaths in the United States. Several dietary factors have been identified that modify pancreatic cancer risk, including low folate levels. In addition to nutrition and lifestyle determinants, folate status may be influenced by genetic factors such as single nucleotide polymorphisms (SNPs). In the present study, we investigated the association between folate levels, genetic polymorphisms in genes of the folate pathway, and pancreatic cancer.

METHODS

Serum and red blood cell (RBC) folate levels were measured in pancreatic cancer and control subjects. Genotypes were determined utilizing Taqman probes and SNP frequencies between cases and controls were assessed using Fisher's exact test. Logistic regression was used to estimate the odds ratio (OR) and corresponding 95% confidence intervals (CIs) to measure the association between genotypes and pancreatic cancer risk. The association between folate levels and SNP expression was calculated using one-way ANOVA.

RESULTS

Mean RBC folate levels were significantly lower in pancreatic cancer cases compared to unrelated controls (508.4 ± 215.9 ng/mL vs 588.3 ± 229.2 ng/mL, respectively) whereas serum folate levels were similar. Irrespective of cancer status, several SNPs were found to be associated with altered serum folate concentrations, including the D919G SNP in methionine synthase (MTR), the L474F SNP in serine hydroxymethyl transferase 1 (SHMT1) and the V175M SNP in phosphatidyl ethanolamine methyltransferase (PEMT). Further, the V allele of the A222V SNP and the E allele of the E429A SNP in methylene tetrahydrofolate reductase (MTHFR) were associated with low RBC folate levels. Pancreatic cancer risk was found to be significantly lower for the LL allele of the L78R SNP in choline dehydrogenase (CHDH; OR = 0.29; 95% CI 0.12-0.76); however, it was not associated with altered serum or RBC folate levels.

Folate metabolism genetic polymorphisms and meningioma and glioma susceptibility in adults

Polymorphic variants of genes involved in folate metabolism are implicated in the susceptibility to meningioma and glioma, but the results from published articles are controversial and inconclusive. Therefore, we performed this meta-analysis including all studies available to evaluate the relationship between folate metabolism genetic polymorphisms and the susceptibility to meningioma and glioma in adults. We searched the literature in PubMed, EMBASE and Cochrane Central Library for relevant articles published up to August 2016. The odds ratios (ORs) and the corresponding 95% confidence intervals (95%Cls) were used to evaluate the associations of two folate metabolism genetic variants MTRR A66G (rs1801394) and MTHFR A1298C (rs1801131) with the risk of meningioma and glioma in adults. We found significant association of MTHFR A1298C (rs1801131) variant genotypes with increased incidence of meningioma and glioma in this study population (CA vs. AA: OR=1.22, P<0.001; CA+CC vs. AA: OR=1.18, P=0.002). Moreover, we found that MTRR A66G (rs1801394) variant genotypes was associated with increased risk of meningioma and glioma (G vs. A: OR=1.11, P=0.020; GG vs. AA+AG: OR=1.17, P=0.043; GG vs. AA: OR=1.22, P=0.023). In conclusion, our meta-analysis suggests that two folate metabolism genetic variants MTRR A66G (rs1801394) and MTHFR A1298C (rs1801131) contribute to genetic susceptibility to meningioma and glioma in adults.

Associations between polymorphisms in folate-metabolizing genes and pancreatic cancer risk in Japanese subjects

Background

Evidence supporting the associations between folate metabolizing gene polymorphisms and pancreatic cancer has been inconclusive. We examined their associations in a case-control study of Japanese subjects.

Methods

Our case-control study involved 360 newly diagnosed pancreatic cancer cases and 400 frequency-matched, non-cancer control subjects. We genotyped four folate metabolizing gene polymorphisms, including two polymorphisms (rs1801133 and rs1801131) in the methylenetetrahydrofolate (MTHFR) gene, one polymorphism (rs1801394) in the 5-methyltetrahydrofolate-homocysteine methyltransferase reductase (MTRR) gene and one polymorphism (rs1805087) in the 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR) gene. Genotyping was performed using Fluidigm SNPtype assays. Unconditional logistic regression methods were used to estimate odds ratios (ORs) and 95 % confidence intervals (CIs) for the associations between folate metabolizing gene variants and pancreatic cancer risk.

Results

Overall we did not observe a significant association between these four genotypes and pancreatic cancer risk. For rs1801133, compared with individuals with the CC genotype of MTHFR C677T, the OR for those with the CT genotype and TT genotype was 0.87 (0.62-1.22) and 0.99 (0.65-1.51), respectively. For rs1801131, individuals with the CC genotype had approximately 1.2-fold increased risk compared with those with the AA genotype, but the association was not statistically significant. In analyses stratified by smoking and drinking status, no significant associations were noted for C677T genotypes. No significant interactions were observed with smoking and drinking with respect to pancreatic cancer risk.

Conclusions

Our data did not support the hypothesis that MTHFR polymorphisms or other polymorphisms in the folate metabolizing pathway are associated with pancreatic cancer risk.

Polymorphisms of MTHFR and susceptibility to oesophageal adenocarcinoma in a Caucasian United Kingdom population

AIM: To identify if methylene tetra-hydrofolatereductase (MTHFR) C677T polymorphisms are associated with oesophageal adenocarcnomas in a Caucasian population and to test whether folic acid and homocysteine levels are linked with cancer risk.

METHODS: A case control study comprising of 58 non cancer and 48 cancer patients, MTHFR C667T genotyping was made and serum folate, homocysteine and vitamin B12 levels were made. Tumour stage, differentiation and survival was recorded. A P value of less than 0.05 was taken to be significant. The χ² used to compare discrete variables and the Mantel-Cox was used to compare survival. A P value less than 0.05 was deemed to be significant.

RESULTS: MTHFR polymorphisms is associated with an increased risk of several cancers. A link between MTHFR C677T polymorphisms and oesophageal squamous cell carcinoma and gastric cardia adenocarcinoma has been demonstrated in at risk Chinese populations. In a Western European population the role of the MTHFR gene has not previously been investigated in the setting of oesophageal adenocarcinoma. No association between folic acid levels and cancer patients was found. The unstable MTHFR 667 TT genotype occurred in 11% cancers and 7% controls, but statistical significance was not reached, homocysteine levels and folic acid levels were not affected, cancer patients with TT genotype displayed a trend for a shorter survival 7 mo vs 20 mo. Serum vitamin B12 levels were higher in the cancer group. The MTHFR 667 TT genotype is much lower than previous population studies.

CONCLUSION: We conclude that serum folic acid and MTHFR polymorphisms are not associated with an increased risk of oesophageal adenocarcinoma, although cancers with unstable TT genotype may indicate a more aggressive disease course.

MTHFR C677T polymorphism and pancreatic cancer risk: a meta-analysis

BACKGROUND

Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in the metabolism of folate, and the role of the MTHFR C677T polymorphism in pancreatic carcinogenesis is still controversial.

METHOD

A literature search was performed using Pubmed and CNKI databases for published studies through May 2012. We performed a meta-analysis of all relevant case-control studies that examined the association between MTHFR C677T polymorphism and pancreatic cancer risk.

RESULTS

Finally, 9 individual case-control studies with a total of 1,299 pancreatic cancer cases and 2,473 controls were included into this meta-analysis.

RESULTS

This meta- analysis showed there was an obvious association between MTHFR C677T polymorphism and pancreatic cancer risk in East Asians (for allele model, OR = 1.67, 95%CI 1.11-2.51; For homozygote model, OR = 2.77, 95%CI 1.40-5.48; for recessive model, OR = 1.96, 95%CI 1.54-2.50; for dominant model, OR = 2.11, 95%CI 1.01-4.41). However, no significant association was found in Caucasians.

CONCLUSION

The MTHFR C677T polymorphism is associated with pancreatic cancer risk, and a race-specific effect may exist in this association. More studies with a larger sample size are needed to further clarify this association.

Interplay between smoking-induced genotoxicity and altered signaling in pancreatic carcinogenesis

Despite continuous research efforts directed at early diagnosis and treatment of pancreatic cancer (PC), the status of patients affected by this deadly malignancy remains dismal. Its notoriety with regard to lack of early diagnosis and resistance to the current chemotherapeutics is due to accumulating signaling abnormalities. Hoarding experimental and epidemiological evidences have established a direct correlation between cigarette smoking and PC risk. The cancer initiating/promoting nature of cigarette smoke can be attributed to its various constituents including nicotine, which is the major psychoactive component, and several other toxic constituents, such as nitrosamines, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, and polycyclic aromatic hydrocarbons. These predominant smoke-constituents initiate a series of oncogenic events facilitating epigenetic alterations, self-sufficiency in growth signals, evasion of apoptosis, sustained angiogenesis, and metastasis. A better understanding of the molecular mechanisms underpinning these events is crucial for the prevention and therapeutic intervention against PC. This review presents various interconnected signal transduction cascades, the smoking-mediated genotoxicity, and genetic polymorphisms influencing the susceptibility for smoking-mediated PC development by modulating pivotal biological aspects such as cell defense/tumor suppression, inflammation, DNA repair, as well as tobacco-carcinogen metabolization. Additionally, it provides a large perspective toward tumor biology and the therapeutic approaches against PC by targeting one or several steps of smoking-mediated signaling cascades.

Epidemiology and potential mechanisms of tobacco smoking and heavy alcohol consumption in pancreatic cancer

Tobacco smoking represents an important known cause of ductal pancreatic adenocarcinoma. Recent data from pooled analyses in consortia involving multiple case-control and cohort studies suggest that heavy (but not moderate or light) alcohol consumption also may increase pancreatic cancer risk. Animal and human evidence indicate that tobacco carcinogens and metabolites may act in concert and have both genetic and epigenetic effects at early and later stages in pancreatic tumorigenesis. One of the more important tobacco-related carcinogens, NNK, probably acts via multiple pathways. Heavy alcohol consumption may increase pancreatic cancer risk by potentiating the effects of other risk factors such as tobacco smoking, poor nutrition, and inflammatory pathways related to chronic pancreatitis, but also may have independent genetic and epigenetic effects. Animal and human studies of tobacco- and alcohol-related pancreatic carcinogenesis suggest multi-modal, overlapping mechanistic pathways. Tobacco smoking and heavy alcohol consumption are preventable exposures, and their avoidance would substantially decrease the burden of pancreatic cancer worldwide.

Polymorphisms and haplotypes in methylenetetrahydrofolate reductase gene and head and neck squamous cell carcinoma risk

Functional polymorphisms in genes encoding enzymes involved in folate metabolism might modulate head and neck carcinoma risk because folate participates in DNA methylation and synthesis. We therefore conducted a case-control study of 853 individuals (322 head and neck cancer cases and 531 non-cancer controls) to investigate associations among MTHFR C677T and MTHFR A1298C polymorphisms and head and neck squamous cell carcinoma risk. Interactions between these two polymorphisms and risk factors and clinical histopathological parameters were also evaluated. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was used to genotype the polymorphisms and Chi-square test and multiple logistic regression were used for statistical analyses. The variables age≥49 years, male gender, tobacco habits and alcohol consumption, MTHFR 1298 AC or CC genotypes, combined genotypes with two or more polymorphic alleles and 677T and 1298C polymorphic alleles were associated with increased risk for this disease (P<0.05). Furthermore, we found that 1298 AC or CC genotypes were associated with age≥49 years, tobacco and alcohol habits (P<0.05). Regarding clinical histopathological parameters, the A1298C polymorphism was more frequent in patients with oral cavity as primary site (P<0.05). MTHFR polymorphisms may contribute for increase risk for head and neck carcinoma and the variables age≥49 years, male gender, tobacco and alcohol habits were associated with MTHFR 1298AC or CC genotypes, confirming that individuals with these variables and MTHFR A1298C polymorphism has higher risk for this disease.

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.

An overview of genetic polymorphisms and pancreatic cancer risk in molecular epidemiologic studies

Background

Although pancreatic cancer has been extensively studied, few risk factors have been identified, and no validated biomarkers or screening tools exist for early detection in asymptomatic individuals. We present a broad overview of molecular epidemiologic studies that have addressed the relationship between pancreatic cancer risk and genetic polymorphisms in several candidate genes and suggest avenues for future research.

Methods

A comprehensive literature search was performed using the PubMed database.

Results

Overall, individual polymorphisms did not seem to confer great susceptibility to pancreatic cancer; however, interactions of polymorphisms in carcinogen-metabolizing genes, DNA repair genes, and folate-metabolizing genes with smoking, diet, and obesity were shown in some studies. The major problem with these studies is that, due to small sample sizes, they lack sufficient statistical power to explore gene–gene or gene–environment interactions. Another important challenge is that the measurement of environmental influence needs to be improved to better define gene–environment interaction. It is noteworthy that 2 recent genome-wide association studies of pancreatic cancer have reported that variants in ABO blood type and in 3 other chromosomal regions are associated with risk for this cancer, thus providing new insight into pancreatic cancer etiology.

Conclusions

As is the case in other complex diseases, common, low-risk variants in different genes may act collectively to confer susceptibility to pancreatic cancer in individuals with repeated environmental exposures, such as smoking and red meat intake. Clarification of gene–gene and gene–environmental interaction is therefore indispensable for future studies. To address these issues, a rigorously designed molecular epidemiologic study with a large sample is desirable.

Review of studies on metabolic genes and cancer in populations of African descent

Genetic polymorphisms described for a number of enzymes involved in the metabolism of tobacco carcinogens and alcohol have been linked to increase cancer risk. Racial disparities in cancer between whites and populations of African descent are well documented. In addition to differences in access to health care, both environment and genetic factors and their interaction may contribute to the increased cancer risk in minority populations. We reviewed the literature to identify case-control studies that included subjects of African descent. Meta-analyses investigating the association of genetic polymorphisms in tobacco metabolic genes and cancer were performed. Although several genes and cancers have been studied, only one or two studies per gene for each cancer site have been published, with the exception of breast (CYP1A1 and CYP1B1), lung (GSTM1, CYP1A1, and NQO1), and prostate (CYP3A4 A293G and CYP17). Marginal statistically significant associations were observed for CYP3A4 A293G and CYP17 5'UTR polymorphisms and prostate cancer. Our findings support the need for additional genetic association studies of breast, prostate, and lung cancers that include a larger number of minority participants. Because incidence and mortality rates for these cancers rank highest among populations of African descent, concentrated research in these areas are warranted.

Epidemiology of pancreatic cancer: an overview

Pancreatic cancer, although infrequent, has an exceptionally high mortality rate, making it one of the four or five most common causes of cancer mortality in developed countries. The incidence of pancreatic cancer varies greatly across regions, which suggests roles for lifestyle factors, such as diet, or environmental factors, such as vitamin D exposure. Smoking is the most common known risk factor, and is the cause of 20-25% of all pancreatic tumors. Alcohol does not seem to be a risk factor, unless it leads to chronic pancreatitis, which is a probable risk factor. Long-standing diabetes increases the risk of pancreatic cancer, but can also be an early manifestation of pancreatic tumors. 5-10% of patients with pancreatic cancer have an underlying germline disorder, while the remaining percentage of cancer cases is thought to be caused by somatic mutations. Some individual studies suggest that mutations in various polymorphic genes can lead to small increases in the risk of pancreatic cancer, but these findings need to be replicated. Rising prevalence of smoking in developing countries, improved diagnosis and increasing population longevity are all likely to increase the global burden of pancreatic cancer in the coming decades.

The inherited genetic component of sporadic pancreatic adenocarcinoma

Pancreatic cancer, like many other complex diseases, has genetic and environmental components to its etiology. It is likely that relatively common genetic variants with modest effects on pancreatic cancer risk play an important role in both familial and sporadic forms of the disease, either individually or in interaction with environmental factors. The relatively high frequency of such variants means that they could potentially explain a substantial portion of disease risk. Here we summarize the findings published to date from genetic association studies. In general, very few low-penetrance variants have been identified and those that have require replication in independent studies. Possible gene-environment interactions arising from these studies also require replication. More comprehensive approaches are needed to make progress, including global analyses of biologically sound pathways and genome-wide association studies. Large sample sizes are required to do this appropriately and multi-study consortia make this possible. A number of consortia of pre-existing studies have already been formed, and these will facilitate the identification of further low-penetrance variants and gene-environment interaction. However, these approaches do not substitute for the design of novel, sufficiently powered studies that apply uniform criteria to case selection, the acquisition of environmental exposure information, and to biological sample collection.

MTHFR C677T polymorphism in chronic pancreatitis and pancreatic adenocarcinoma

Chronic pancreatitis and pancreatic adenocarcinoma are extensively studied as common and potentially lethal disorders. However, their causes and genetic background in most cases remain unclear. The C677T polymorphism in 5',10'-methylenetetrahydrofolate reductase (MTHFR) gene may modulate the risk of pancreatic disorders. In this study, we tested whether MTHFR C677T polymorphism is associated with chronic pancreatitis and pancreatic adenocarcinoma in the Serbian population. DNA was extracted from blood samples of 51 chronic pancreatitis patients, 21 pancreatic adenocarcinoma patients, and a control group consisting of 50 healthy smokers. The MTHFR C677T polymorphism was analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. Although, no statistically significant differences were observed in the distribution of MTHFR genotype or allele frequencies between patients and control groups, the results showed an increased frequency of homozygotes for MTHFR C677T polymorphism in chronic pancreatitis patients (14%) and a decreased frequency in pancreatic adenocarcinoma patients (5%) in comparison to the control group (8%). We speculate that the MTHFR C677T polymorphism could act as a possible risk factor for chronic pancreatitis and a possible protective factor in pancreatic adenocarcinoma. This observation needs further investigation in prospective studies on a larger number of patients, in which the effect of other genetic and environmental factors should also be taken into consideration.

His595Tyr polymorphism in the methionine synthase reductase (MTRR) gene is associated with pancreatic cancer risk

BACKGROUND & AIMS

This study attempts to elucidate a part of the genetic predisposition to the sporadic invasive ductal adenocarcinoma of the pancreas focusing on the genes implicated in the gene-environment interactions in carcinogenesis.

METHODS

First, 227 single nucleotide polymorphisms (SNPs) of 46 genes were genotyped on 198 cases and 182 controls. The SNPs, which showed a significant association, were further genotyped on additional samples to perform a joint analysis (total 317 cases vs 1232 controls). The gene selected by joint analysis was resequenced for a high-density SNP typing and a haplotype analysis on 702 cases and 785 controls. Function of the risk and wild-type haplotypes was assessed using cells transfected with complementary DNA (cDNA).

RESULTS

The joint analysis with multiple testing adjustment identified 2 SNPs on the methionine synthase reductase (MTRR) gene: rs162049 (intronic SNP), Fisher exact test, P = .0018; OR, 1.33; 95% CI: 1.11-1.60 and rs10380 (His595Tyr), Fisher exact test, P = .0063; OR, 1.45; 95% CI: 1.11-1.88. The SNPs remained significant in the recessive model after the permutation test for multiple testing (rs162049, P = .024; rs10380, P = .023) in the high-density analysis. Stable transfectants of the risk haplotype MTRR cDNA showed significantly elevated homocysteine levels in a culture medium, a lower level of the LINE-1 methylation, and a lower expression of the MTRR protein than did the transfectants with the wild-type haplotype cDNA.

CONCLUSIONS

Our study suggested a common missense SNP of the MTRR gene as a novel pancreatic cancer susceptibility factor with a functional significance in folate-related metabolism and the genome-wide methylation status.

Folate pathway genetic polymorphisms and susceptibility of central nervous system tumors in Thai children

BACKGROUND

Folate is an important micronutrient molecule participating in DNA synthesis, methylation and repair mechanisms. Genetic polymorphisms in folate pathway related enzymes including methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C, methionine synthase (MTR) A2756G, thymidylate synthase (TS) 28-bp tandem repeat, and reduced folate carrier (RFC) G80A have been shown to be associated with increased susceptibility for several cancers. The aim of the present study was to evaluate whether single nucleotide polymorphisms in the genes encoding enzymes of the folate pathway predispose to any CNS tumors in Thai children.

METHODS

In the present case-control study, we investigated these polymorphisms in genomic DNA from peripheral blood mononuclear cells in 73 Thai children with various types of central nervous system tumors and in 205 age and sex matched controls.

RESULTS

Thirty-one out of 73 patients were diagnosed with glial tumors (astrocytoma, oigodendroglioma and ependymoma), 28 with embryonal CNS tumors (medulloblastoma, pinealoblastoma and primitive neuroectodermal tumor), 13 with germ cell tumors and 1 with meningioma. We found that the homozygous CC allele of MTHFR A1298C conferred an increased risk of embryonal CNS tumors (OR: 3.9; 95% CI: 1.3-11.4, p=0.02).

CONCLUSION

Our findings thus suggest that folate metabolism may play a role in the pathogenesis of certain specific subtypes of pediatric brain tumor in Thai children, especially embryonal CNS tumors.

Myeloperoxidase and superoxide dismutase polymorphisms are associated with an increased risk of developing pancreatic adenocarcinoma

BACKGROUND

Pancreatic cancer risk has been linked to chronic pancreatitis and periodontitis, suggesting a role for inflammation in disease etiology. Myeloperoxidase (MPO) and superoxide dismutase (SOD2) are enzymes that regulate reactive oxygen species and contain recognized single nucleotide polymorphisms (SNPs) that confer altered enzyme activity.

METHODS

One hundred twenty-two patients with pancreatic cancer and 331 age- and sex-matched controls were analyzed for polymorphisms of the MPO - guanine 463 adenine (-G463A) and the SOD2 alanine (Ala)-to-valine (Val) polymorphism at codon 16 (Ala16Val) genes. Cases and controls were analyzed for associations between these polymorphisms, adjusting for sex, age, history of alcohol use and smoking history.

RESULTS

The variant A allele of MPO -G463A was associated with a lower risk of pancreatic cancer (adjusted odds ratio [OR] for pancreatic cancer, 0.57; 95% confidence interval [95% CI], 0.4-0.9; P = .02). The SOD2 homozygous variant genotype (Val/Val) was associated with a greater risk of pancreatic cancer (adjusted OR, 1.96; 95% CI, 1.0-3.8; P = .04). Compared with individuals who carried both low-risk alleles (A/- and Ala/-), significantly more cases than controls carried both high-risk genotypes (G/G and Val/Val; adjusted OR, 4.31; 95% CI, 1.8-10; P = .001), or 1 high-risk genotype (adjusted OR, 1.96; 95% CI, 1.1-3.4; P = .01).

CONCLUSIONS

Polymorphisms of the inflammatory pathway genes MPO -G463A and SOD2 Ala16Val are associated with elevated pancreatic cancer risk. Oxidative stress may play an important role in pancreatic cancer carcinogenesis.

Plasma folate, vitamin B6, vitamin B12, and homocysteine and pancreatic cancer risk in four large cohorts

Folate deficiency induces DNA breaks and may alter cellular capacity for mutation and epigenetic methylation. Few studies have examined the influence of one-carbon nutrients on pancreatic cancer risk, although recent studies suggest a potential protective effect for one-carbon nutrients from food sources, but not from supplements. We conducted a prospective nested case-control study to examine plasma concentrations of folate, vitamin B6 [whose main circulating form is pyridoxal-5'-phosphate (PLP)], vitamin B12, and homocysteine in relationship to pancreatic cancer, using four large prospective cohorts. Multivariable adjusted odds ratios (OR) and 95% confidence intervals (95% CI) were calculated using conditional logistic regression. All statistical tests were two sided. Among 208 cases and 623 controls, we observed no association between folate, PLP, vitamin B12, or homocysteine and pancreatic cancer risk. Comparing the highest to lowest quartiles of plasma concentration, the ORs were 1.20 (95% CI, 0.76-1.91) for folate, 0.80 (95% CI, 0.51-1.25) for B6, 0.91 (95% CI, 0.57-1.46) for B12, and 1.43 (95% CI, 0.90-2.28) for homocysteine. In analyses restricted to nonusers of multivitamins, we observe a modest inverse trend between folate, PLP, and B12 and pancreatic cancer risk. In contrast, no such inverse associations were observed among study subjects who reported multivitamin supplement use. Among all participants, plasma levels of folate, B6, B12, and homocysteine were not associated with a significant reduction in the risk of pancreatic cancer. Among participants who obtain these factors exclusively through dietary sources, there may be an inverse relation between circulating folate, B6, and B12 and risk.

Association of Methylenetetrahydrofolate Reductase Polymorphism and the Risk of Squamous Cell Carcinoma in Renal Transplant Patients

The relative risk of developing cutaneous squamous cell carcinoma (SCC) is significantly increased after organ transplantation. We investigated the genetic association of SCC in two pathways associated with cancer risks, with the potential for modification by vitamin supplementation. A total of 367 renal transplant recipients (117 with SCC and 250 without any skin cancer) were genotyped for key polymorphisms in the folate pathway (methylene tetrahydrofolate reductase; MTHFR:C677T), and the vitamin D pathway (vitamin D receptor: Intron8G/T;). Individuals carrying the MTHFR 677T allele had a marked increase in risk of SCC (adjusted odds ratio=2.54, P=0.002, after adjustment for age, ender, skin type, sun exposure score, and immunosuppression duration; lower 95% confidence boundary odds ratio of 1.41). In contrast, vitamin D receptor polymorphisms were not significantly associated. Folate-sensitive pathways may play a critical role in the elevated rate of SCC in renal transplant recipients.

Methionine and vitamin B6 intake and risk of pancreatic cancer: a prospective study of Swedish women and men

BACKGROUND & AIMS

It has been hypothesized that dietary factors involved in methyl group metabolism, such as methionine, folate, and vitamin B(6), may modify cancer risk. We have previously reported an inverse association between folate intake and pancreatic cancer risk in a prospective population-based cohort of Swedish women and men. In the present study, we used data from this prospective study to examine whether methionine and vitamin B(6) intakes were associated with the incidence of exocrine pancreatic cancer.

METHODS

Our study population comprised 81,922 Swedish women and men, aged 45-83 years, who were free from cancer and completed a self-administered food-frequency questionnaire in 1997. We used Cox proportional hazards models to estimate rate ratios with 95% confidence intervals (CI), adjusted for age, sex, education, smoking, body mass index, diabetes, and intakes of total energy and dietary folate.

RESULTS

During a mean follow-up of 7.2 years, through June 2005, 147 incident cases of pancreatic cancer were diagnosed. Methionine intake was significantly inversely associated with risk of pancreatic cancer, whereas no significant association was observed for dietary or total vitamin B(6) intake. The multivariate rate ratios comparing the highest with the lowest quartile of methionine intake were 0.44 (95% CI, 0.26-0.73; P for trend = .0005) in women and men combined, 0.59 (95% CI, 0.28-1.21; P for trend = .07) in women, and 0.32 (95% CI, 0.15-0.65; P for trend = .002) in men.

CONCLUSIONS

These findings suggest that higher methionine intake may reduce the risk of pancreatic cancer.

Dietary factors and biomarkers involved in the methylenetetrahydrofolate reductase genotype-colorectal adenoma pathway

BACKGROUND & AIMS

Methylenetetrahydrofolate reductase (MTHFR) is involved in intracellular folate homeostasis and metabolism. We assessed 2 polymorphisms in the MTHFR gene (C677T and A1298C) in relation to colorectal adenoma recurrence and conducted analyses to investigate their joint effects with plasma and dietary markers of folate status.

METHODS

We prospectively analyzed data from 1598 individuals genotyped for the C677T polymorphism and 1583 with data on A1298C.

RESULTS

Among nonusers of multivitamin supplements, compared with wild-type carriage, higher odds of recurrence were observed for those with the 677 TT variant (odds ratio [OR], 1.66; 95% confidence interval [CI], 1.04-2.63) and a nonsignificant increase was observed among those with the 1298 CC variant (OR, 1.50; 95% CI, 0.93-2.40). Diplotype analyses among nonusers of multivitamins showed that individuals who carry the MTHFR 677TT_1298AA or 677CC_1298CC combination were significantly more likely to have a recurrence compared with those with the double wild-type (OR, 2.05 for TT_AA and 1.85 for CC_CC). Higher odds of recurrence were observed among participants with low folate intake or plasma folate and the 677 TT or 1298 CC variants compared with those with lower levels and the wild-type or heterozygous genotypes. Stronger associations were shown for the combination of high homocysteine and the 677 TT variant (OR, 2.29; 95% CI, 1.00-5.26) but not the 1298 CC variant (OR, 1.09; 95% CI, 0.39-3.01).

CONCLUSIONS

We propose that the effect of the MTHFR genotypes on increasing risk of adenoma recurrence in the presence of a low folate status is through their increase in homocysteine concentrations, which in turn could result in DNA hypomethylation via pathways involving S-adenosylhomocysteine.

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

Methylenetetrahydrofolate reductase (MTHFR), a key regulatory enzyme in the metabolism of folate, is suspected to play a role in the etiology of cancer, via its effects on DNA methylation and nucleotide synthesis. In this study we have investigated the effect of two functional polymorphisms of the MTHFR gene, MTHFR_677_C > T and MTHFR_1298_A > C, on breast and ovarian cancer risk in Polish BRCA1 mutation carriers. The study included 319 breast cancer cases, 146 ovarian cancer cases and 290 controls unaffected by breast and ovarian cancer, in situ breast cancer or any other kind of cancer. Genotyping analysis was performed using polymerase chain reaction followed by restriction fragment length polymorphism analysis. Odds ratios (OR) were calculated using univariate and multivariate logistic regression taking into account a series of confounding variables that potentially could have biased any association. The results revealed that the MTHFR_677_C > T change was associated with an increased risk of breast and ovarian cancer. The MTHFR_1298_A > C polymorphism was only associated with a decrease in breast cancer risk. Together, it appears that functional polymorphisms in the MTHFR gene modify the risk of breast and may potentially alter the risk of ovarian cancer in women with an inherited predisposition.

Folate intake, MTHFR polymorphisms, and risk of esophageal, gastric, and pancreatic cancer: a meta-analysis

BACKGROUND & AIMS

Increasing evidence suggests that a low folate intake and impaired folate metabolism may be implicated in the development of gastrointestinal cancers. We conducted a systematic review with meta-analysis of epidemiologic studies evaluating the association of folate intake or genetic polymorphisms in 5,10-methylenetetrahydrofolate reductase (MTHFR), a central enzyme in folate metabolism, with risk of esophageal, gastric, or pancreatic cancer.

METHODS

A literature search was performed using MEDLINE for studies published through March 2006. Study-specific relative risks were weighted by the inverse of their variance to obtain random-effects summary estimates.

RESULTS

The summary relative risks for the highest versus the lowest category of dietary folate intake were 0.66 (95% confidence interval [CI], 0.53-0.83) for esophageal squamous cell carcinoma (4 case-control), 0.50 (95% CI, 0.39-0.65) for esophageal adenocarcinoma (3 case-control), and 0.49 (95% CI, 0.35-0.67) for pancreatic cancer (1 case-control, 4 cohort); there was no heterogeneity among studies. Results on dietary folate intake and risk of gastric cancer (9 case-control, 2 cohort) were inconsistent. In most studies, the MTHFR 677TT (variant) genotype, which is associated with reduced enzyme activity, was associated with an increased risk of esophageal squamous cell carcinoma, gastric cardia adenocarcinoma, noncardia gastric cancer, gastric cancer (all subsites), and pancreatic cancer; all but one of 22 odds ratios were >1, of which 13 estimates were statistically significant. Studies of the MTHFR A1298C polymorphism were limited and inconsistent.

CONCLUSIONS

These findings support the hypothesis that folate may play a role in carcinogenesis of the esophagus, stomach, and pancreas.

Selected polymorphisms of DNA repair genes and risk of pancreatic cancer

BACKGROUND

Genetic variants of DNA repair genes may contribute to pancreatic carcinogenesis. O(6)-methylguanine-DNA methyltransferase (MGMT) is the major protein that removes alkylating DNA adducts, and apurinic/apyrimidinic endonuclease 1 (APE1) and X-ray repair cross-complementing group 1 (XRCC1) play important roles in the base excision repair pathway.

METHODS

We investigated the association between polymorphisms of MGMT (Leu(84)Phe and Ile(143)Val), APE1 (Asp(148)Glu), and XRCC1 (Arg(194)Trp and Arg(399)Gln) and risk of pancreatic cancer in a case-control study. Exposure information from 384 patients with primary pancreatic ductal adenocarcinoma and 357 cancer-free healthy controls were collected and genomic DNAs were genotyped for five markers. Controls were frequency matched to patients by age at enrollment (+/-5 years), gender, and race. We estimated odds ratios (ORs) and 95% confidence intervals (CIs) by using unconditional logistic regression models.

RESULTS

There was no significant main effect or interaction with smoking of these genetic variants on the risk of pancreatic cancer. However, the XRCC1(194) polymorphism had a significant interaction with the APE1(148) (p=0.005) or MGMT(84) polymorphism (p=0.02) in modifying the risk of pancreatic cancer.

CONCLUSIONS

This study suggests that polymorphisms of genes involved in the repair of alkylating DNA adduct and DNA base damage may play a role in modulating the risk of pancreatic cancer. Larger studies are required to validate these preliminary findings. The mechanism of the combined genotype effects remains to be elucidated.

Genotype/phenotype of familial pancreatic cancer

It is estimated that 5% to 10% of pancreatic cancer cases are attributable to hereditary factors. We believe that the number of cases that are genetic in etiology are even greater, however, based not on a classic autosomal dominant pattern of inheritance but rather when one takes into account low-penetrant inherited susceptibility factors. There is also a growing recognition that the development of pancreatic cancer in pancreatic cancer-prone families is dependent not only on genetic variables but on nongenetic factors. The aim of this article is to review the challenges in identifying pancreatic cancer-prone families and how environmental factors interact with genetic factors in these families.

Using high-throughput SNP technologies to study cancer

Identifying genes involved in the development of cancer is crucial to fully understanding cancer biology, for developing novel therapeutics for cancer treatment and for providing methods for cancer prevention and early diagnosis. The use of polymorphic markers, in particular single nucleotide polymorphisms (SNPs), promises to provide a comprehensive tool for analysing the human genome and identifying those genes and genomic regions contributing to the cancer phenotype. This review summarizes the various analytical methodologies in which SNPs are used and presents examples of how each of these methodologies have been used to locate genes and genomic regions of interest for various cancer types. Additionally many of the current SNP-analysing technologies will be reviewed with particular attention paid to the advantages and disadvantages of each and how each technology can be applied to the analysis of the genome for identifying cancer-related genes.

Folate intake and pancreatic cancer incidence: a prospective study of Swedish women and men

BACKGROUND

Epidemiologic evidence supports an association between high folate intake and reduced risk of some cancers, in particular colorectal cancer. However, epidemiologic data concerning the relationship between folate and pancreatic cancer risk are sparse. We examined the association between folate intake and risk of pancreatic cancer in a population-based prospective study of Swedish women and men.

METHODS

We prospectively followed 81,922 women and men in the Swedish Mammography Cohort and the Cohort of Swedish Men who were cancer-free and completed a 96-item food-frequency questionnaire in 1997. Cox proportional hazards models were used to estimate multivariable rate ratios (RRs) with 95% confidence intervals (CIs). All statistical tests were two-sided.

RESULTS

A total of 135 incident pancreatic cancer cases were diagnosed during a mean follow-up of 6.8 years. In multivariable analyses controlling for age, smoking, fruit and vegetable consumption, and other potential confounders, dietary and total folate intakes were statistically significantly inversely associated with risk of pancreatic cancer. The multivariable rate ratios of pancreatic cancer for those in the highest category of folate intake (> or = 350 microg/day) compared with the lowest category of intake (< 200 microg/day) were 0.25 (95% CI = 0.11 to 0.59; Ptrend = .002) for dietary folate and 0.33 (95% CI = 0.15 to 0.72; Ptrend = .01) for total folate (combining dietary and supplemental sources). Folic acid from supplements was not associated with pancreatic cancer (for > or = 300 microg/day compared with 0 microg/day of supplemental folic acid, multivariable RR = 1.02; 95% CI = 0.56 to 1.88). The sex- and age-standardized incidence rates of pancreatic cancer per 100,000 person-years were 41 for the lowest and 18 for the highest category of dietary folate intake.

CONCLUSION

Our results suggest that increased intake of folate from food sources, but not from supplements, may be associated with a reduced risk of pancreatic cancer.