Reduced folate carrier gene G80A polymorphism is associated with an increased risk of gastroesophageal cancers in a chinese population

Polymorphisms in solute carrier genes (SLC19A1, SLCO1B1, and SLCO1B3) predicts survival and toxicity in North Indian lung cancer patients undergoing platinum-based doublet chemotherapy

WHAT IS KNOWN AND OBJECTIVE

Solute Carrier (SLC) transporters are known mediators of drug disposition that facilitate the influx of substrates and various chemotherapeutic agents into cells. Polymorphisms in the SLC19A1, SLCO1B1, and SLCO1B3 gene influence the prognosis in the cancer patients, but little is known about their role in lung cancer in Asians. So, the current study aims to investigate the polymorphisms in SLC19A1, SLCO1B1, and SLCO1B3 genes in Northern Indian lung cancer patients.

METHODS

Patients with lung cancer who had a confirmed histology and cytology diagnosis were enrolled in the study. SLC polymorphisms were assessed by Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) for variations in SLC19A1 (G⁸⁰ A), SLCO1B1 (A³⁸⁸ G, T⁵²¹ C), and SLCO1B3 (A^1683-5676 G).

RESULTS AND DISCUSSION

Our results showed that mutant genotype for SLC19A1 G⁸⁰ A polymorphism had higher median survival time (MST) compared to wild genotype. ADCC patients with mutant genotype showed better survival compared to wild genotype for SLC19A1 G⁸⁰ A. SCLC patients G⁸⁰ A polymorphism showed increased survival in patients with mutant genotype (p = 0.04). In SLCO1B3, A^1683-5676 G patients carrying heterozygous alleles and administered with platinum and docetaxel showed inferior survival (p = 0.006). In T⁵²¹ C variant, patients with carrier genotype had reduced chances of developing anaemia (p = 0.04). Patients with SLC19A1 and SLCO1B3 variants showed lower incidence of thrombocytopenia and nephrotoxicity.

WHAT IS NEW AND CONCLUSION

Our findings imply that Solute Carrier gene polymorphisms modulate the overall survival in lung cancer patients undergoing platin-based doublet chemotherapy, also these polymorphisms have a modifying impact on the associated adverse events/toxicity.

Detection of Potential Mutated Genes Associated with Common Immunotherapy Biomarkers in Non-Small-Cell Lung Cancer Patients

Microsatellite instability (MSI), high tumor mutation burden (TMB-H) and programmed cell death 1 ligand 1 (PD-L1) expression are hot biomarkers related to the improvement of immunotherapy response. Two cohorts of non-small-cell lung cancer (NSCLC) were collected and sequenced via targeted next-generation sequencing. Drug analysis was then performed on the shared genes using three different databases: Drugbank, DEPO and DRUGSURV. A total of 27 common genes were mutated in at least two groups of TMB-H-, MSI- and PD-L1-positive groups. AKT1, SMAD4, SCRIB and AXIN2 were severally involved in PI3K-activated, transforming growth factor beta (TGF-β)-activated, Hippo-repressed and Wnt-repressed pathways. This study provides an understanding of the mutated genes related to the immunotherapy biomarkers of NSCLC.

The establishment, development and future of the Chinese environmental mutagen society

It has been 40 years since the Chinese Environmental Mutagen Society (CEMS) was established in 1981. Now, it has grown a first-level national society in China, which has 15 professional committees and more than 5000 members. Over the past 40 years, the CEMS has been making many contributions to advance the research of environmental mutagens in China and cultivate professional talents in this field. In the twenty-first century, looking back on what the CEMS has gone through and accomplished, and in light of the major changes in our tasks and mission in the new era, we must plan well for the future, to overcome our shortcomings, to embrace greater development of the CEMS.

Polymorphisms in MTHFR, MTR, RFC1 and CßS genes involved in folate metabolism and thyroid cancer: a case-control study

INTRODUCTION

Polymorphisms in genes coding enzymes involved in folate metabolism may cause alterations in this metabolic pathway and contribute to carcinogenesis, because folate is essential for DNA synthesis, methylation and repair. The objective of this study was to investigate the association of MTHFR 677C>T (rs1801133), MTR 2756A>G (rs1805087), RFC1 80A>G (rs1051266) and CßS 844ins(68) (no rs#) polymorphisms and thyroid cancer development. The association of these polymorphisms with demographic risk factors and clinical histopathological parameters was also evaluated.

MATERIAL AND METHODS

The study is a case-control analysis with a total of 462 individuals (151 patients and 311 controls). Polymerase chain reaction-restriction fragment length polymorphism technique was used for genotyping. The χ² and multiple logistic regression were utilized for statistical analysis.

RESULTS

The polymorphisms analysis revealed an association between the MTHFR 677C>T polymorphism (OR = 2.87, 95% CI: 1.50-5.48, p < 0.01, codominant model), (OR = 1.76, 95% CI: 1.18-2.64, p < 0.01, dominant model), (OR = 2.37, 95% CI: 1.28-4.39, p < 0.01, recessive model) and thyroid cancer. RFC1 80A>G polymorphism also was associated with thyroid cancer under recessive mode of inheritance (OR = 1.55; 95% CI: 1.02-2.38; p = 0.04); however, this polymorphism showed Hardy-Weinberg disequilibrium in the control group (χ² = 24.71, p < 0.001). Furthermore, alcohol (OR = 1.56, 95% CI: 1.36-1.89, p < 0.01) and tobacco consumption (OR = 1.97, 95% CI: 1.28-3.04, p < 0.01) were associated with increased risk for thyroid cancer. The MTR 2756A>G polymorphism showed an association with tumor extent (OR = 2.69, 95% CI: 1.27-5.71, p < 0.01) and aggressiveness (OR = 4.51, 95% CI: 1.67-12.1, p < 0.01).

CONCLUSIONS

MTHFR 677C>T is significantly associated with increased risk for thyroid cancer and MTR 2756A>G is associated with tumor extent and aggressiveness. In addition, alcohol and tobacco consumption were associated with increased risk of thyroid cancer. These results may contribute to a better prognosis for thyroid cancer.

The RFC1 80G>A, among Common One-Carbon Polymorphisms, Relates to Survival Rate According to DNA Global Methylation in Primary Liver Cancers

Polymorphisms within one-carbon metabolism genes have been largely studied in relation to cancer risk for the function of this pathway in nucleotide synthesis and DNA methylation. Aims of this study were to explore the possible link among several common functional gene polymorphisms within one-carbon metabolism and survival rate in primary liver cancers, i.e., hepatocellular carcinoma and cholangiocarcinoma, and to assess the additional effect of global DNA methylation on survival rate and mortality risk. Forty-seven primary liver cancer patients were genotyped for ten polymorphisms: DHFR 19bp ins/del, TS 2rpt-3rpt, MTHFD1 1958G>A, MTHFR 677C>T, MTR 2756A>G, MTRR 66A>G, RFC1 80G>A, SHMT1 1420C>T, BHMT 716 A>G, TC II 776C>G. Methylation was determined in peripheral blood mononuclear cells (PBMCs) DNA as methylcytosine (mCyt) content using LC/MS/MS. Among the polymorphisms analysed, the RFC1 80G>A (rs1051266) influenced the survival rate in primary liver cancers. The RFC1 80AA was associated to a significantly reduced survival rate (22.2%) as compared to both GG and GA genotypes (61.5% and 76% respectively, p = 0.005). When the cancer patients were stratified according to the mCyt median value as high (>5.34%) or low (≤5.34%), the concomitant presence of AA genotype and low mCyt level led to a significantly worse survival rate as compared to the G allele carriership (p<0.0001) with a higher Hazard Ratio (HR = 6.62, p = 0.001). The subjects carrying the AA genotype in association with high mCyt did not show a significant difference in survival rate as compared with the G allele carriers (p = 0.919). The RFC1 80G>A polymorphism influenced the survival rate, and the presence of RFC1 80AA genotype with low global methylation in PBMCs DNA was associated with poorer prognosis and higher mortality risk, therefore highlighting novel molecular signatures potentially helpful to define prognostic markers for primary liver cancers.

A Study of Single Nucleotide Polymorphisms of the SLC19A1/RFC1 Gene in Subjects with Autism Spectrum Disorder

Autism Spectrum Disorder (ASD) is a group of neurodevelopmental disorders with complex genetic etiology. Recent studies have indicated that children with ASD may have altered folate or methionine metabolism, suggesting that the folate–methionine cycle may play a key role in the etiology of ASD. SLC19A1, also referred to as reduced folate carrier 1 (RFC1), is a member of the solute carrier group of transporters and is one of the key enzymes in the folate metabolism pathway. Findings from multiple genomic screens suggest the presence of an autism susceptibility locus on chromosome 21q22.3, which includes SLC19A1. Therefore, we performed a case-control study in a Japanese population. In this study, DNA samples obtained from 147 ASD patients at the Kanazawa University Hospital in Japan and 150 unrelated healthy Japanese volunteers were examined by the sequence-specific primer-polymerase chain reaction method pooled with fluorescence correlation spectroscopy. p < 0.05 was considered to represent a statistically significant outcome. Of 13 single nucleotide polymorphisms (SNPs) examined, a significant p-value was obtained for AA genotype of one SNP (rs1023159, OR = 0.39, 95% CI = 0.16–0.91, p = 0.0394; Fisher’s exact test). Despite some conflicting results, our findings supported a role for the polymorphism rs1023159 of the SLC19A1 gene, alone or in combination, as a risk factor for ASD. However, the findings were not consistent after multiple testing corrections. In conclusion, although our results supported a role of the SLC19A1 gene in the etiology of ASD, it was not a significant risk factor for the ASD samples analyzed in this study.

The association between RFC1 G80A polymorphism and cancer susceptibility: Evidence from 33 studies

Aberrant folate metabolism is closely related to tumorigenesis. Genetic variations in the Reduced folate carrier 1 (RFC1) may alter the progress of folate metabolism, and thereby cause the initiation and progress of the cancer. Considerable studies have performed to investigate the association between RFC1 G80A (rs1051266) polymorphism and cancer susceptibility, but the conclusions were conflicting. Therefore, we conducted a meta-analysis to reevaluate the association of RFC1 G80A polymorphism with cancer risk. PubMed and EMBASE were searched for eligible studies. The association of RFC1 G80A polymorphism and cancer risk was evaluated by the pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs). The significant association was found between RFC1 G80A polymorphism and hematological malignance susceptibility (A vs. G: OR=1.11, 95%CI=1.003-1.23, P=0.045; GA vs. GG: OR=1.18, 95%CI=1.06-1.31, P=0.002; AA+GA vs. GG: OR=1.18, 95%CI=1.07-1.29, P=0.001). Stratified analysis by ethnicity indicated that the association became more prominent among Caucasians (GA vs. GG: OR=1.28, 95%CI=1.12-1.45, P<0.001; AA+GA vs. GG: OR=1.21, 95%CI=1.08-1.36, P=0.001). In term of the cancer type, this polymorphism significantly increased the risk of acute lymphoblast leukemia (GA vs. GG: OR=1.13, 95%CI=1.001-1.28, P=0.048; AA+GA vs. GG: OR=1.28, 95%CI=1.13-1.46, P<0.001) and acute myeloid leukemia (GA vs. GG: OR=2.57, 95%CI=1.37-4.85, P=0.003). No significant association between RFC1 G80A polymorphism and overall solid cancer risk was observed, but a protective association with digestive cancer risk was found (GA vs. GG: OR=0.89, 95%CI= 0.81-0.99, P=0.030). The comprehensive meta-analysis encouraged the notion that RFC1 G80A polymorphism may play an important role in hematopoietic system malignance. These findings need further validation in the large multicenter investigations.

Dietary folate, one-carbon metabolism-related genes, and gastric cancer risk in Korea

SCOPE

We evaluated the interactions between polymorphisms involved in one-carbon metabolism-related genes and dietary folate intake in gastric cancer risk within the Korean population through a hospital-based case-control study.

METHODS AND RESULTS

A total of 542 controls and 271 cases were included. Genotype data were selected from data produced by the Affymetrix Axiom(®) Exome 319 Array. We considered seven single nucleotide polymorphisms (SNPs) of five genes whose SNPs are located in the coding region with a minor allele frequency > 5%: MTHFR (G1793A, A1298C, C677T), MTR A2756G, MTRR A66G, SHMT1 C1420T, and SLC19A1 G80A. Our study found that MTR A2756G was associated with a decreased gastric cancer risk. MTHFR G1793A showed a statistically significant interaction between dietary folate intake and gastric cancer.

CONCLUSION

Our results suggest that MTR A2756G is significantly associated with gastric cancer risk, and that MTHFR G1793A statistically interacts with dietary folate intake. Our findings indicate that gene-folate interactions may contribute to gastric cancer risk.

Association between folate metabolism-related polymorphisms and colorectal cancer risk

Folate has essential roles in DNA synthesis, repair and methylation. Folate metabolism-related gene variants may modulate the levels of this vitamin and affect the cancer risk. Thus, whether these polymorphisms play an important role in carcinogenesis, particularly colorectal cancer (CRC) development, has been a subject interest. The present study investigated the association between polymorphisms in the methylenetetrahydrofolate reductase (MTHFR), thymidylate synthase (TS) and the reduced folate carrier 1 (RFC1) genes and CRC risk. Polymorphisms in MTHFR (677C>T and 1298A>C), TS [1494del6 and the TS enhancer region (TSER)] and RFC1 (-43T>C, 80G>A and 696C>T) were characterized using polymerase chain reaction-restriction fragment length polymorphism in 477 CRC cases and 514 controls. Although no polymorphisms were significantly associated with the CRC risk in the overall sample, significant associations between folate metabolism-related polymorphisms and CRC risk were identified in the stratified analyses. The MTHFR 677CT/1298AC and MTHFR 1298AC+CC/TSER 2R3R genotypes in the presence of plasma folate levels ≤4.12 ng/ml were associated with significantly increased CRC risk. In addition, individuals with the MTHFR 677TT/TSER 3R3R or MTHFR 677/TSER 3R3R/TS 1494 0bp6bp+6bp6bp genotypes and diabetes mellitus (DM) were at an increased risk for CRC. Therefore, the data suggest that i) MTHFR polymorphisms combined with low plasma folate levels and ii) polymorphisms in folate metabolism-related genes combined with metabolic syndrome risk factors (hypertension and DM) increase the odds of developing CRC.

Association of reduced folate carrier-1 (RFC-1) polymorphisms with ischemic stroke and silent brain infarction

Stroke is the second leading cause of death in the world and in South Korea. Ischemic stroke and silent brain infarction (SBI) are complex, multifactorial diseases influenced by multiple genetic and environmental factors. Moderately elevated plasma homocysteine levels are a major risk factor for vascular diseases, including stroke and SBI. Folate and vitamin B12 are important regulators of homocysteine metabolism. Reduced folate carrier (RFC), a bidirectional anion exchanger, mediates folate delivery to a variety of cells. We selected three known RFC-1 polymorphisms (-43C>T, 80A>G, 696T>C) and investigated their relationship to cerebral infarction in the Korean population. We used the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method to analyze associations between the three RFC-1 polymorphisms, disease status, and folate and homocysteine levels in 584 ischemic stroke patients, 353 SBI patients, and 505 control subjects. The frequencies of the RFC-1 -43TT, 80GG, and 696CC genotypes differed significantly between the stroke and control groups. The RFC-1 80A>G substitution was also associated with small artery occlusion and SBI. In a gene-environment analysis, the RFC-1 -43C>T, 80A>G, and 696T>C polymorphisms in the ischemic stroke group had combined effects with all environmental factors. In summary, we found that the RFC-1 -43C>T, 80A>G, and 696T>C polymorphisms may be risk factors for ischemic stroke.

Folate-related polymorphisms in gastrointestinal stromal tumours: susceptibility and correlation with tumour characteristics and clinical outcome

The folate metabolism pathway has a crucial role in tumorigenesis as it supports numerous critical intracellular reactions, including DNA synthesis, repair, and methylation. Despite its importance, little is known about the influence of the folate pathway on gastrointestinal stromal tumour (GIST), a rare tumour with an incidence ranging between 6 and 19.6 cases per million worldwide. The importance of folate metabolism led us to investigate the influence of polymorphisms in the genes coding folate-metabolising enzymes on GIST susceptibility, tumour characteristics and clinical outcome. We investigated a panel of 13 polymorphisms in 8 genes in 60 cases and 153 controls. The TS 6-bp deletion allele (formerly rs34489327, delTInsTTAAAG) was associated with reduced risk of GIST (OR=0.20, 95% CI 0.05-0.67, P=0.0032). Selected polymorphisms in patients stratified by age, gender, and other main molecular and clinical characteristics showed that few genotypes may show a likely correlation. We also observed a significant association between the RFC AA/AG genotype and time to progression (HR=0.107, 95% CI 0.014-0.82; P=0.032). Furthermore, we observed a tendency towards an association between the SHMT1 variant allele (TT, rs1979277) and early death (HR=4.53, 95% CI 0.77-26.58, P=0.087). Aware of the strengths and limitations of the study, these results suggest that polymorphisms may modify the risk of GIST and clinical outcome, pointing to the necessity for further investigations with information on folate plasma levels and a larger study population.

Reduced folate carrier-1 G80a gene polymorphism is associated with neuroblastoma's development

Neuroblastoma is a malignant embryonal tumor of neural crest cells that give rise to the sympathetic nervous system, responsible for 10-70% of all cases of childhood cancer. Because of its early appearance, it has been suggested that risk factors active in the prenatal can be associated with the pathogenesis of neuroblastoma. The aim of this study was to investigate whether the genetic polymorphisms MTHFR C677T and A1298C, MTR A2756G, TYMS 2R/3R and SLC19A1 G80A, involved in folate metabolism, increase the risk of neuroblastoma in Brazilian children. This study comprised 31 Brazilian children (0-14 years old) diagnosed with neuroblastoma compared with 92 controls. Investigation of polymorphisms MTHFR C677T, MTR A2756G and SLC19A1 A80G was performed using PCR-RFLP, the TYMS 2R/3R using PCR and MTHFR A1298C using AS-PCR. The SLC19A1 A80A genotype was significantly associated with the development of neuroblastoma, compared with the control group (Williams G-Test = 0.0286; OR = 5.1667; 95% CI = 1.4481-18.4338; p = 0.0175). When analyzed together, the 80AG+AA genotypes showed a trend toward association (OR = 3.3033; 95% CI = 1.0586-10.3080; p = 0.0563). Our results suggest that individuals carriers of genotype AA for the SLC19A1 gene present risk for the development of neuroblastoma and possibly have difficulty in absorption of folic acid by the cells, and this may adversely affect the metabolism of folate causing genomic instability and promoting the development of cancer. This is the first retrospective/prospective study to examine the relationship between polymorphisms of folate pathway genes and risk of neuroblastoma.

Serum folic acid and RFC A80G polymorphism in Alzheimer's disease and vascular dementia

Low level of vitamin B12 and folic acid has been reported to play an important role in the pathogenesis of Alzheimer's disease (AD) and vascular dementia (VaD). Serum folic acid and vitamin B12 were assayed in 80 AD and 50 VaD cases and in 120 healthy controls. The reduced folate carrier (RFC1) gene, rs1051266, which encodes the RFC 1, protein was analyzed for polymorphism by polymerase chain reaction-restriction fragment length polymorphism. It was observed that the patients having folic acid <8.45 ng/mL had 2.4 (95% confidence interval [CI]: 1.4-4.5) times higher odds of having AD and 2.1 (95% CI: 1.1-4.2) times higher odds of having VaD than patients having folic acid ≥8.45 ng/mL. Serum vitamin B12 level did not show any such statistically significant effect in altering the odds. No direct association was found between variant (G) allele or genotype of rs1051266 with AD and VaD cases. On serum folate level no association was observed with gene polymorphism.

Polymorphisms in genes involved in folate metabolism modify the association of dietary and circulating folate and vitamin B-6 with cervical neoplasia

High folate intake has been suggested as an important factor in cancer prevention; however, previous studies on the relation among folate intake, serum folate, and plasma homocysteine (hcy) are controversial. We conducted a hospital-based, case-control study in Brazil investigating associations between dietary and circulating vitamins B-6 and B-12 and folate, hcy, genotypes of folate-metabolizing enzyme methylenetetrahydrofolate reductase (MTHFR C677T, A1298C), 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR A2756G), methionine synthase reductase (MTRR A66G), and reduced folate carrier (RFC1 G80A) and risk of cervical intraepithelial neoplasia (CIN) grades 1 (CIN1), 2 (CIN2), and 3 (CIN3). The study was composed by 453 controls, 140 CIN1, 126 CIN2, and 231 CIN3. We investigated the joint effects of genetic variants of folate-related genes using genetic risk scores (GRSs) by summing the number of risk alleles for CIN1 and CIN2+ (CIN2 and CIN3 cases). The OR (95% CI) for CIN1 and CIN2+ per each risk allele were 1.29 (1.01, 1.65) and 1.22 (1.01, 1.46), respectively. An association between folate intake and CIN2+ was observed only after stratification according to GRS: crude OR (95% CI) for lower folate intake and GRS ≥ 4 was 1.67 (0.92, 3.04) (P-trend < 0.001) compared with higher folate intake (above the median) and GRS ≤ 3. The CIN2+ risk of lower serum vitamin B-6 and GRS ≥ 4 was 2.14 (0.92, 5.02) (P-trend = 0.05) and lower serum folate (below the median) and GRS ≥ 4 was 0.49 (0.20, 1.17) (P-trend = 0.05) after adjustment for confounding variables and human papillomavirus infection. Our data suggest that polymorphisms in genes related to folate metabolism modify the association of dietary and circulating folate and vitamin B-6 with cervical neoplasia.

Comprehensive evaluation of one-carbon metabolism pathway gene variants and renal cell cancer risk

Introduction

Folate and one-carbon metabolism are linked to cancer risk through their integral role in DNA synthesis and methylation. Variation in one-carbon metabolism genes, particularly MTHFR, has been associated with risk of a number of cancers in epidemiologic studies, but little is known regarding renal cancer.

Methods

Tag single nucleotide polymorphisms (SNPs) selected to produce high genomic coverage of 13 gene regions of one-carbon metabolism (ALDH1L1, BHMT, CBS, FOLR1, MTHFR, MTR, MTRR, SHMT1, SLC19A1, TYMS) and the closely associated glutathione synthesis pathway (CTH, GGH, GSS) were genotyped for 777 renal cell carcinoma (RCC) cases and 1,035 controls in the Central and Eastern European Renal Cancer case-control study. Associations of individual SNPs (n = 163) with RCC risk were calculated using unconditional logistic regression adjusted for age, sex and study center. Minimum p-value permutation (Min-P) tests were used to identify gene regions associated with risk, and haplotypes were evaluated within these genes.

Results

The strongest associations with RCC risk were observed for SLC19A1 (P_min-P = 0.03) and MTHFR (P_min-P = 0.13). A haplotype consisting of four SNPs in SLC19A1 (rs12483553, rs2838950, rs2838951, and rs17004785) was associated with a 37% increased risk (p = 0.02), and exploratory stratified analysis suggested the association was only significant among those in the lowest tertile of vegetable intake.

Conclusions

To our knowledge, this is the first study to comprehensively examine variation in one-carbon metabolism genes in relation to RCC risk. We identified a novel association with SLC19A1, which is important for transport of folate into cells. Replication in other populations is required to confirm these findings.

Genes involved with folate uptake and distribution and their association with colorectal cancer risk

Folate status is an important predictor of colorectal cancer risk. Common genetic variants in genes involved in regulating cellular folate levels might also predict risk, but there are limited data on this issue. We conducted a family-based case-control association study of variants in four genes involved in folate uptake and distribution: FOLR1, FPGS, GGH and SLC19A1, using 1,750 population-based and 245 clinic-based cases of pathologically confirmed colorectal cancer and their unaffected relatives participating in the Colon Cancer Family Registries. Standardized questionnaires, administered to all participants, collected information on risk factors and diet. Standard molecular techniques were used to determine microsatellite instability (MSI) status on cases. tagSNPs (n = 29) were selected based on coverage as assessed by pairwise r2. We found no evidence that tagSNPs in these genes were associated with risk of colorectal cancer. For the SLC19A1-rs1051266 (G80A, Arg27His) missense polymorphism, the A/A genotype was not associated with risk of colorectal cancer using population-based (OR = 1.00; 95% CI = 0.81-1.23) or clinic-based (OR = 0.75; 95% CI = 0.44-1.29) families compared to the G/A and G/G genotypes. We found no evidence that the association between any tagSNP and CRC risk was modified by multivitamin use, folic acid use and dietary folate intake and total folate intake. The odds ratios were similar, irrespective of MSI status, tumor subsite and family history of colorectal cancer. In conclusion, we found no significant evidence that genetic variants in FOLR1, GGH, FPGS and SLC19A1 are associated with the risk of colorectal cancer.

The reduced folate carrier (RFC1) 80G > A and folate hydrolase 1 (FOLH1) 1561C > T polymorphisms and the risk of colorectal cancer: a nested case-referent study

OBJECTIVE

Polymorphisms in genes involved in folate uptake and metabolism may affect folate status and, thereby, the risk of cancer. In this nested case-referent study, we related two such polymorphisms, reduced folate carrier (RFC1) 80G > A and folate hydrolase 1 (FOLH1) 1561C > T, to the risk of colorectal cancer, taking into account pre-diagnostic plasma folate and total homocysteine concentrations and the MTHFR 677C > T polymorphism, which were analysed in a previous study.

MATERIAL AND METHODS

Subjects were 220 cases and 414 matched referents from the population-based Northern Sweden Health and Disease Study.

RESULTS

The RFC1 80A-allele was associated with reduced plasma folate and elevated plasma total homocysteine concentrations, but the result was statistically significant only for folate. In contrast, the FOLH1 1561T-allele was associated with higher plasma folate and reduced plasma total homocysteine concentrations, and the result was statistically significant only for homocysteine. Neither polymorphism was related to the risk of colorectal cancer, either in univariate analysis or after adjusting for body mass index, current smoking, recreational and occupational physical activity and alcohol intake. Further adjustment for folate or homocysteine status or the MTHFR 677C > T polymorphism did not affect risk estimates. Subjects with the RFC1 80AA genotype in combination with low plasma folate concentrations or the MTHFR 677TT genotype had a reduced risk of colorectal cancer of borderline statistical significance.

CONCLUSIONS

These findings suggest that although the RFC1 80G > A and FOLH1 1561C > T polymorphisms may influence folate status, they are not likely to have a major independent role in the development of colorectal cancer.

GG genotype of cyclin D1 G870A polymorphism is associated with non-cardiac gastric cancer in a high-risk region of China

OBJECTIVE

Cyclin D1 (CCND1) is a regulatory protein involved in the cell cycle of both normal and neoplastic cells. Polymorphism of this gene at codon 242 in exon 4 (A870G) has an impact on the risk of several human cancers. The purpose of this study was to study the relation between the CCND1 A870G gene polymorphism and the risk of non-cardiac gastric cancer in a Chinese population.

MATERIAL AND METHODS

The study population consisted of 159 patients with non-cardiac gastric cancer and 162 cancer-free controls. CCND1 870A/G polymorphism was genotyped by a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay and sequencing.

RESULTS

CCND1 genotype distribution among the patients was significantly different from that among controls; AA (odds ratio (OR)=0.348, 95% CI: 0.163-0.742) and GA (OR=0.715, 95% CI: 0.506-1.012) genotypes were significantly lower in the gastric cancer patients than in the controls when subjects with the GG genotype served as the reference category. In other words, the risk of gastric cancer for subjects with the GG genotype was 2.8 times that of subjects with the AA genotype, and 1.4 times that of subjects with the GA genotype. Furthermore, in the stratification analyses, the risk of GG genotype was more evident in subjects >or=60 years of age and those positive for Helicobacter pylori (H. pylori) infection.

CONCLUSIONS

The CCND1870 GG genotype is associated with an increased risk for non-cardiac gastric cancer in patients in a high-risk area of China. Larger studies with multiple polymorphisms are needed to verify this finding and the function of this polymorphism needs to be further investigated.

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.

Genetic polymorphisms and esophageal cancer risk

The aim of this paper is to review and evaluate, in a comprehensive manner, the published data regarding the contribution of genetic polymorphisms to risk of esophageal cancer, including squamous cell carcinoma (SCC) and adenocarcinoma, in humans. All relevant studies available in MEDLINE and published before February 2007 were identified. Studies carried out in humans and that compared esophageal cancer patients with at least 1 standard control group were considered for analysis. One-hundred studies and 3 meta-analyses were identified. Eighty (80%) studies were conducted in Asian countries, particularly China including Taiwan (60 (60%) studies). The most intensively examined genes were those encoding carcinogen metabolic enzymes. The most widely studied gene was GSTM1 (15 studies), followed by ALDH2 (11 studies). ALDH2, MTHFR C677T, CYP1A1 Ile/Val, CYP1A1MspI, CYP2E1, GSTP1, GSTM1 and GSTT1 were examined by meta-analyses and significant relations were found between ALDH2*1*2 and the CYP1A1 Val allele and increased risk of esophageal cancer. In addition, increased risk of esophageal SCC was consistently associated with the ADH2*1*2 and the p53 codon 72 Pro/Pro genotypes. Cohort studies that simultaneously consider multiple genetic and environmental factors possibly involved in esophageal carcinogenesis are needed to ascertain not only the relative contribution of these factors to tumor development but also the contributions of their putative interactions.

Polymorphisms of MTHFD, plasma homocysteine levels, and risk of gastric cancer in a high-risk Chinese population

PURPOSE

Accumulative evidence suggests that folate has a protective effect on gastric cancer. The methylenetetrahydrofolate dehydrogenase (MTHFD) plays an important role in folate and homocysteine metabolisms, and polymorphisms of MTHFD may result in disturbance of the folate-mediated homocysteine pathway. The aim of this study is to test the hypothesis that genetic variants of MTHFD and plasma homocysteine levels are associated with risk of gastric cancer and modulated by genotypes of methylenetetrahydrofolate reductase (MTHFR).

EXPERIMENTAL DESIGN

We genotyped G1958A and T401C in MTHFD and C677T in MTHFR and detected total plasma homocysteine (tHcy) levels in a case-control study of 589 gastric cancer cases and 635 cancer-free controls in a high-risk Chinese population.

RESULTS

The variant genotypes of MTHFD 1958AA and 401CC were associated with a significantly increased risk of gastric cancer [adjusted odds ratio (OR), 2.05; 95% confidence interval (95% CI), 1.34-3.13 for 1958AA; adjusted OR, 1.43; 95% CI, 1.14-1.80 for 401CC] compared with 1958GG/GA and 401TT/TC genotypes, respectively. Both of the effects were more evident in the subjects carrying MTHFR 677CT/TT genotypes. The average tHcy level was significantly higher in gastric cancer cases than in controls (P < 0.01), and the upper quartile of tHcy (>13.6 micromol/L) was associated with an 82% significantly increased risk of gastric cancer, compared with the lowest quartile of tHcy (<or=8.0 micromol/L; adjusted OR, 1.82; 95% CI, 1.20-2.75).

CONCLUSIONS

The strong associations between MTHFD variants and the plasma tHcy levels and gastric cancer risk suggest, for the first time, a possible gene-environment interaction between genetic variants of folate-metabolizing genes and high tHcy levels in gastric carcinogenesis.

TGFB1 and TGFBR2 functional polymorphisms and risk of esophageal squamous cell carcinoma: a case-control analysis in a Chinese population

PURPOSE

Transforming growth factor beta1 (TGF-beta1) and its receptor II (TGF-betaRII) are two key components of TGF-beta signaling and play an important role in carcinogenesis. Several functional polymorphisms were identified in TGFB1 and TGFBR2 and associated with elevated serum or plasma level of TGF-beta1 and enhanced transcription activity of TGFBR2. This population-based case-control study was to evaluate the contribution of functional polymorphisms in TGFB1 C-509T, Leu10Pro and TGFBR2 G-875A to the risk of esophageal squamous cell carcinoma (ESCC).

METHODS

Genotyping was performed using the primer-introduced restriction analysis-PCR assay in 255 ESCC cases and 704 cancer-free controls in a Chinese population.

RESULTS

The variant genotypes (-509CT/TT) of TGFB1 C-509T were associated with a 63% significantly decreased risk of ESCC (adjusted OR = 0.37, 95% CI = 0.27-0.50) compared with -509CC wild-type homozygote. In addition, a moderately decreased risk of ESCC was related to -875GA (adjusted OR = 0.70, 95% CI = 0.49-0.99) but not -875AA genotype (adjusted OR = 1.09, 95% CI = 0.51-2.35) in TGFBR2, compared with -875GG common genotype. Furthermore, subjects carrying variant genotypes either or both of TGFB1 C-509T and TGFBR2 G-875A had a significantly reduced risk of ESCC (adjusted OR = 0.37, 95% CI = 0.26-0.53 for either one variant genotype and adjusted OR = 0.30, 95% CI = 0.19-0.48 for both variant genotypes) in a dose-response manner (chi (trend) (2) = 33.87, P < 0.001) compared with subjects with both wild-type genotypes.

CONCLUSIONS

These results are consistent with our previous findings in gastric cancer and support the hypothesis that genetic variants in TGFB1 and TGFBR2 may modulate the risk of ESCC.