Folate Pathway Genes Research Articles

Possible selection of host folate pathway gene polymorphisms in patients with malaria from a malaria endemic region in North East India

Recent studies in experimental mice have shown that mild deficiency of methylenetetrahydrofolate reductase (MTHFR) enzyme confers protection against malaria, thus providing an important basis for the hypothesis that MTHFR polymorphism, i.e. C677T, might have been subjected to selection pressure against malaria. The present study was undertaken in a malaria endemic region in North East India to assess whether a similar selection advantage exists for other genes in folate metabolism pathway. A total of 401 subjects including 131 symptomatic malaria, 97 asymptomatic malaria and 173 normal healthy controls were analysed for nine polymorphisms (single-nucleotide polymorphisms [SNPs] in eight genes and insertion/deletion in one gene): MTHFR C677T, methionine synthase reductase (MTRR) A66G, glutamate carboxypeptidase II (GCPII) C1561T, cystathionine beta-synthase (CBS) 844ins68, reduced folate carrier-1 (RFC-1) G80A, serine hydroxymethyltransferase (SHMT) C1420T, methionine synthase (MTR) A2756G, MTHFR G1793A (D 919G), glycine N-methyltransferase (GNMT) 1289 by PCR-RFLP technique. Differences in frequencies of genotype distribution of each polymorphic marker between these groups were evaluated. MTRR A2756G, SHMT C1420T, GCPII C1561T, MTRR A2756G and GNMT C1289T and RFC1 G80A polymorphisms showed significantly different prevalence between different groups analyzed. No significant differences were seen in the distribution of other polymorphisms. The study gives a clue for the possible selection of specific polymorphisms in the genes involved in the folate metabolism pathway by malaria parasite.

Distinct effects of folate pathway genes MTHFR and MTHFD1L on ruminative response style: a potential risk mechanism for depression.

Alterations in the folate pathway have been related to both major depression and cognitive inflexibility; however, they have not been investigated in the genetic background of ruminative response style, which is a form of perseverative cognition and a risk factor for depression. In the present study, we explored the association of rumination (measured by the Ruminative Responses Scale) with polymorphisms of two distinct folate pathway genes, MTHFR rs1801133 (C677T) and MTHFD1L rs11754661, in a combined European white sample from Budapest, Hungary (n=895) and Manchester, United Kingdom (n=1309). Post hoc analysis investigated whether the association could be replicated in each of the two samples, and the relationship between folate pathway genes, rumination, lifetime depression and Brief Symptom Inventory depression score. Despite its functional effect on folate metabolism, the MTHFR rs1801133 showed no effect on rumination. However, the A allele of MTHFD1L rs11754661 was significantly associated with greater rumination, and this effect was replicated in both the Budapest and Manchester samples. In addition, rumination completely mediated the effects of MTHFD1L rs11754661 on depression phenotypes. These findings suggest that the MTHFD1L gene, and thus the C1-THF synthase enzyme of the folate pathway localized in mitochondria, has an important effect on the pathophysiology of depression through rumination, and maybe via this cognitive intermediate phenotype on other mental and physical disorders. Further research should unravel whether the reversible metabolic effect of MTHFD1L is responsible for increased rumination or other long-term effects on brain development.

Increased MTHFR promoter methylation in mothers of Down syndrome individuals

Despite that advanced maternal age at conception represents the major risk factor for the birth of a child with Down syndrome (DS), most of DS babies are born from women aging less than 35 years. Studies performed in peripheral lymphocytes of those women revealed several markers of global genome instability, including an increased frequency of micronuclei, shorter telomeres and impaired global DNA methylation. Furthermore, young mothers of DS individuals (MDS) are at increased risk to develop dementia later in life, suggesting that they might be “biologically older” than mothers of euploid babies of similar age.Mutations in folate pathway genes, and particularly in the methylenetetrahydrofolate reductase (MTHFR) one, have been often associated with maternal risk for a DS birth as well as with risk of dementia in the elderly. Recent studies pointed out that also changes in MTHFR methylation levels can contribute to human disease, but nothing is known about MTHFR methylation in MDS tissues.We investigated MTHFR promoter methylation in DNA extracted from perypheral lymphocytes of 40 MDS and 44 matched control women that coinceived their children before 35 years of age, observing a significantly increased MTHFR promoter methylation in the first group (33.3±8.1% vs. 28.3±5.8%; p=0.001). In addition, the frequency of micronucleated lymphocytes was available from the women included in the study, was higher in MDS than control mothers (16.1±8.6‰ vs. 10.5±4.3‰; p=0.0004), and correlated with MTHFR promoter methylation levels (r=0.33; p=0.006).Present data suggest that MTHFR epimutations are likely to contribute to the increased genomic instability observed in cells from MDS, and could play a role in the risk of birth of a child with DS as well as in the onset of age related diseases in those women.

Targeting MTHFD2 in Acute Myeloid Leukemia

Alterations in differentiation pathways contribute to the development of acute myeloid leukemia (AML). Differentiation therapy with all-trans retinoic acid (ATRA) has dramatically altered the treatment of acute promyelocytic leukemia, transforming it from a nearly fatal disease to a curable one. We set out to identify cellular pathways that contribute to AML differentiation, with the goal of identifying new therapeutic targets. We analyzed gene expression data from AML cell lines treated with phorbol 12-myristate 13-acetate (PMA), ATRA, Vitamin D, the BET inhibitor JQ1 and the DOT1L inhibitor EPZ00477, treatments known to induce AML differentiation and impair growth. Folate-mediated one-carbon metabolism was one of only three metabolic pathways altered by these compounds, with expression of MTHFD2 consistently downregulated with each compound.MTHFD2 is an NAD-dependent, bi-functional mitochondrial methylenetetrahydrofolate dehydrogenase and cyclohydrolase. It is differentially expressed in embryonic and transformed tissues and is upregulated in myeloid progenitors. MTHFD2 is the most differentially expressed metabolic enzyme in cancer cells versus normal cells, including normal proliferating cells. We thus investigated the role of MTHFD2 in myeloid malignancy. First, we demonstrated using ChIP-qPCR, MYC knockdown and MYC inhibition with a BET inhibitor, that MYC directly regulates MTHFD2 expression in AML. Knockdown of MTHFD2 with two shRNAs confirmed to have on-target activity, induced myeloid differentiation in AML cell lines, as measured by Cd11b expression, morphologic changes and induction of a previously validated AML differentiation gene expression signature. MTHFD2 knockdown decreased cell growth in AML cell lines, as well as decreased colony formation in methylcellulose in both AML cell lines and primary patient blasts. AML cells transduced with these two MTHFD2-directed shRNAs demonstrated attenuated growth in an orthotopic mouse model of AML. Furthermore, three MTHFD2-directed shRNAs prolonged survival in an MLL-AF9 mouse leukemia model. Additionally, using a doxycycline inducible shRNA system, we demonstrated that two miR30-shRNAs directed against MTHFD2 decreased AML burden in mice with established disease and prolonged survival.To identify biomarkers of response to MTHFD2 suppression, we used single sample Gene Set Enrichment Analysis (ssGSEA) to identify primary patient AML samples enriched for gene expression signatures of folate-mediated one-carbon metabolism and MTHFD2. We found in both independent data sets that the cluster of patients enriched for expression of the one-carbon folate pathway gene signatures was also enriched for patients with FLT3-ITD mutations, a subset of AML with a particularly poor prognosis. In addition, in an shRNA screen targeting 11,194 genes and performed in 216 cancer cell lines, including 17 AML lines, FLT3-ITD was a biomarker of response to MTHFD2 knockdown. We next validated that while MTHFD2 suppression induced measureable differentiation in all six AML cell lines examined, it induced the most robust induction of apoptosis in FLT3-ITD mutant AML. The mitochondrial one-carbon folate pathway is thought to contribute to cellular oxidative balance by providing reducing power in the form of NAD(P)H, and suppression of MTHFD2 was previously shown to increase ROS levels. Indeed, suppression of MTHFD2 led to a marked increase in ROS in the FLT3-ITD positive AML cell lines in which apoptosis was induced.In summary, a decrement in MTHFD2 expression was found at the center of multiple AML perturbations that impair AML growth and induce differentiation. Our data support MTHFD2 as an AML dependency and FLT3-ITD as a potential biomarker of response. We thus provide critical preclinical evidence for targeting of MTHFD2 as a therapeutic strategy in AML. DisclosuresStone:Celgene: Consultancy; Merck: Consultancy. DeAngelo:Celgene: Consultancy; Pfizer: Consultancy; Incyte: Consultancy; Agios: Consultancy; Novartis: Consultancy; Ariad: Consultancy; Bristol Myers Squibb: Consultancy; Amgen: Consultancy. Stegmaier:Novartis Pharmaceuticals: Consultancy.

Folate metabolic pathway single nucleotide polymorphisms: a predictive pharmacogenetic marker of methotrexate response in Indian (Asian) patients with rheumatoid arthritis.

We evaluated the pharmacogenetic influence of genetic polymorphisms in folate pathway genes in Indian rheumatoid arthritis patients receiving methotrexate (MTX). Twelve polymorphisms within nine folate pathway genes were analyzed for association with MTX response in 322 Indian rheumatoid arthritis (RA) patients and MTX pharmacokinetics in 94 RA patients. Polymorphisms in GGH, SHMT1 and TS were associated with MTX-related adverse events while SNPs in MTHFR and RFC1/SLC19A1 were associated with MTX efficacy. TS5'UTR and SHMT1 polymorphisms were associated with higher plasma levels of MTX. Polymorphisms in folate-MTX pathway genes contribute to MTX response and affect MTX concentrations in Indian RA patients. A toxicogenetic index could identify patients who develop adverse events to MTX.

2192 Expression analysis of folate pathway genes with putative impact on leucovorin metabolism in patients with colorectal cancer

2192 Expression analysis of folate pathway genes with putative impact on leucovorin metabolism in patients with colorectal cancer

Polymorphisms in maternal folate pathway genes interact with arsenic in drinking water to influence risk of myelomeningocele.

Arsenic induces neural tube defects in many animal models. Additionally, studies have shown that mice with specific genetic defects in folate metabolism and transport are more susceptible to arsenic-induced neural tube defects. We sought to determine whether 14 single-nucleotide polymorphisms in genes involved in folate metabolism modified the effect of exposure to drinking water contaminated with inorganic arsenic and posterior neural tube defect (myelomeningocele) risk. Fifty-four mothers of children with myelomeningocele and 55 controls were enrolled through clinical sites in rural Bangladesh in a case-control study of the association between environmental arsenic exposure and risk of myelomeningocele. We assessed participants for level of myelomeningocele, administered questionnaires, conducted biological and environmental sample collection, and performed genotyping. Inductively coupled plasma mass spectrometry was used to measure inorganic arsenic concentration in drinking water. Candidate single-nucleotide polymorphisms were identified through review of the literature. Drinking water inorganic arsenic concentration was associated with increased risk of myelomeningocele for participants with 4 of the 14 studied single-nucleotide polymorphisms in genes involved in folate metabolism: the AA/AG genotype of rs2236225 (MTHFD1), the GG genotype of rs1051266 (SLC19A1), the TT genotype of rs7560488 (DNMT3A), and the GG genotype of rs3740393 (AS3MT) with adjusted odds ratio of 1.13, 1.31, 1.20, and 1.25 for rs2236225, rs1051266, rs7560488, and rs3740393, respectively. Our results support the hypothesis that environmental arsenic exposure increases the risk of myelomeningocele by means of interaction with folate metabolic pathways.

Polymorphisms of Genes Involved in the Folate Metabolic Pathway Impact the Occurrence of Unexplained Recurrent Pregnancy Loss.

Low levels of folate combined with high levels of homocysteine may cause unexplained recurrent pregnancy loss (URPL). However, the relationships between polymorphisms in genes of the folate metabolic pathway and URPL remain controversial. We conducted a case-control study to explore polymorphisms of the major folate pathway genes, including methylenetetrahydrofolate reductase (MTHFR) 677C>T, MTHFR 1298A>C, methionine synthase (MTR) 2756A>G, methionine synthase reductase (MTRR) 66A>G and reduced folate carrier 1 (RFC-1) 80A>G, and their associations with URPL. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to determine the distributions of MTHFR, MTR and RFC-1 polymorphisms, and the results were validated using direct sequencing. The polymorphisms in MTRR were determined using direct sequencing. Haplotypes were analyzed using SHEsis, an online tool for biological analysis. We found that the MTHFR 677T allele and the 677T/1298A/2756A/66A/80G haplotype were risk factors for URPL, while the MTR 2756G allele and the 677C/1298A/2756A/66A/80A haplotype exhibited protective effects on susceptibility to URPL in a Chinese Han population from the Hangzhou area.

The genetics of folate metabolism and maternal risk of birth of a child with Down syndrome and associated congenital heart defects.

Almost 15 years ago it was hypothesized that polymorphisms of genes encoding enzymes involved in folate metabolism could lead to aberrant methylation of peri-centromeric regions of chromosome 21, favoring its abnormal segregation during maternal meiosis. Subsequently, more than 50 small case-control studies investigated whether or not maternal polymorphisms of folate pathway genes could be risk factors for the birth of a child with Down syndrome (DS), yielding conflicting and inconclusive results. However, recent meta-analyses of those studies suggest that at least three of those polymorphisms, namely MTHFR 677C>T, MTRR 66A>G, and RFC1 80G>A, are likely to act as maternal risk factors for the birth of a child with trisomy 21, revealing also complex gene-nutrient interactions. A large-cohort study also revealed that lack of maternal folic acid supplementation at peri-conception resulted in increased risk for a DS birth due to errors occurred at maternal meiosis II in the aging oocyte, and it was shown that the methylation status of chromosome 21 peri-centromeric regions could favor recombination errors during meiosis leading to its malsegregation. In this regard, two recent case-control studies revealed association of maternal polymorphisms or haplotypes of the DNMT3B gene, coding for an enzyme required for the regulation of DNA methylation at centromeric and peri-centromeric regions of human chromosomes, with risk of having a birth with DS. Furthermore, congenital heart defects (CHD) are found in almost a half of DS births, and increasing evidence points to a possible contribution of lack of folic acid supplementation at peri-conception, maternal polymorphisms of folate pathway genes, and resulting epigenetic modifications of several genes, at the basis of their occurrence. This review summarizes available case-control studies and literature meta-analyses in order to provide a critical and up to date overview of what we currently know in this field.

Polymorphisms in folate pathway genes are not associated with somatic nondisjunction in turner syndrome.

Folate metabolism dysfunction can lead to DNA hypomethylation and abnormal chromosomal segregation. Previous investigations of this association have produced controversial results. Here we performed a case-control study in patients with Turner syndrome (TS) to determine the effects of genetic polymorphisms of folate pathway genes as potential risk factors for somatic chromosomal nondisjunction. TS is a useful model for this investigation because patients with TS show a high frequency of chromosome mosaicism. Here we investigated the possible association of polymorphisms of the MTHFR gene with TS risk, which has been previously investigated with controversial results. We also examined the effects of MTR, RFC1, and TYMS gene polymorphisms in TS for the first time. The risk was evaluated according to allelic and genotype (independent and combined) frequencies among 70 patients with TS and 144 age-matched healthy control subjects. Polymorphism genotyping was performed by PCR, PCR-RFLP, and PCR-ASA. The polymorphisms MTHFR 677C>T and 1298A>C, MTR 2756A>G, RFC1 80G>A, and TYMS 2R/3R-alone or in combinations-were not associated with the risk of chromosomal aneuploidy in TS. In conclusion, our present findings did not support a link between impaired folate metabolism and abnormal chromosome segregation leading to somatic nondisjunction in TS patients.

The association of folate pathway and DNA repair polymorphisms with susceptibility to childhood acute lymphoblastic leukemia

Genetic factors may play an important role in susceptibility to childhood acute lymphoblastic leukemia (ALL). The aim of our study was to evaluate the associations of genetic polymorphisms in folate pathway and DNA repair genes with susceptibility to ALL. In total, 121 children with ALL and 184 unrelated healthy controls of Slovenian origin were genotyped for 14 polymorphisms in seven genes of folate pathway, base excision repair and homologous recombination repair (TYMS, MTHFR, OGG1, XRCC1, NBN, RAD51, and XRCC3). In addition, the exon 6 of NBN was screened for the presence of mutations using denaturing high performance liquid chromatography. Twelve polymorphisms were in Hardy–Weinberg equilibrium in controls and their genotype frequencies were in agreement with those reported in other Caucasian populations. Among the investigated polymorphisms and mutations, NBN Glu185Gln significantly decreased susceptibility to B-cell ALL (p=0.037), while TYMS 3R allele decreased susceptibility to T-cell ALL (p=0.011). Moreover, significantly decreased susceptibility to ALL was observed for MTHFR TA (p=0.030) and RAD51 GTT haplotypes (p=0.016). Susceptibility to ALL increased with the increasing number of risk alleles (ptrend=0.007). We also observed significant influence of hOGG–RAD51 and NBN–RAD51 interactions on susceptibility to ALL. Our results suggest that combination of several polymorphisms in DNA repair and folate pathways may significantly affect susceptibility to childhood ALL.

Expression of Folate Pathway Genes in Stage III Colorectal Cancer Correlates with Recurrence Status Following Adjuvant Bolus 5-FU-Based Chemotherapy.

Colorectal cancer is commonly treated with 5-fluorouracil and 5-formyltetrahydrofolate (leucovorin). Metabolic action of leucovorin requires several enzymatic steps that are dependent on expression of corresponding coding genes. To identify folate pathway genes with possible impact on leucovorin metabolism, a retrospective study was performed on 193 patients with stage III colorectal cancer. Relative expression of 22 genes putatively involved in leucovorin transport, polyglutamation and metabolism was determined in tumor and mucosa samples using quantitative real-time polymerase chain reaction. After surgery, patients received adjuvant 5-fluorouracil-based bolus chemotherapy with leucovorin during six months, and were followed for 3 to 5 years. Cox regression analysis showed that high tumoral expression of the genes SLC46A1/PCFT (proton-coupled folate transporter) and SLC19A1/RFC-1 (reduced folate carrier 1) correlated significantly (p < 0.001 and p < 0.01, respectively) with a decreased risk of recurrent disease, measured as disease-free survival (DFS). These two genes are involved in the transport of folates into the cells and each functions optimally at a different pH. We conclude that SLC46A1/PCFT and SLC19A1/RFC-1 are associated with DFS of patients with colorectal cancer and hypothesize that poor response to 5-fluorouracil plus leucovorin therapy in some patients may be linked to low expression of these genes. Such patients might need a more intensified therapeutic approach than those with high gene expression. Future prospective studies will determine if the expression of any of these genes can be used to predict response to leucovorin.

CBS c.844ins68 Polymorphism Frequencies in Control Populations: Implications on Nonsyndromic Cleft Lip with or without Cleft Palate

Nonsyndromic cleft lip with or without cleft palate (NSCLP) is a common birth defect with substantial clinical and social impact. Folate deficiency is one of the factors that have been associated with increased risk for NSCLP. Polymorphisms in folate and homocysteine pathway genes may act as susceptibility factors. The objective of this study was to evaluate prevalence estimates of cystathionine beta-synthase (CBS) insertion of 68-bp (c.844ins68) polymorphisms and their correlation with NSCLP. A total of 236 unrelated individuals from seven Indian populations and an additional 355 cases with NSCLP and 357 controls without NSCLP were included in this study. We investigated the CBS c.844ins68 polymorphism in all samples. Genotyping was performed with polymerase chain reaction and electrophoresis. The data were statistically analyzed using the chi-square test. The CBS c.844ins68 allele is present in six of the seven populations analyzed, and allele frequencies range from 1.5% in Balija to 9.1% in Sugali populations. The CBS c.844ins68 polymorphism showed a significant protective effect on NSCLP at both genotype (WW versus WI: odds ratio [OR] = 0.54, 95% confidence interval [CI] = 0.31 to 0.95, P = .149) and allele levels (W versus I: OR = 0.56, 95% CI = 0.32 to 0.96, P = .033). The current study observed significant differences in the frequency of the CBS 844ins68 allele across populations. There is a significant association between CBS c.844ins68 polymorphism and cleft lip and palate in the Indian population. Additional studies are warranted to identify the functional variants in the genes controlling homocysteine as etiological contributors to the formation of oral clefts.

Folate pathway gene polymorphisms, maternal folic acid use, and risk of childhood acute lymphoblastic leukemia.

Several studies suggest that maternal folic acid supplementation before or during pregnancy protects against childhood acute lymphoblastic leukemia (ALL). We investigated associations between ALL risk and folate pathway gene polymorphisms, and their modification by maternal folic acid supplements, in a population-based case-control study (2003-2007). All Australian pediatric oncology centers provided cases; controls were recruited by national random digit dialing. Data from 392 cases and 535 controls were included. Seven folate pathway gene polymorphisms (MTHFR 677C>T, MTHFR 1298A>C, MTRR 66A>G, MTR 2756 A>G, MTR 5049 C>A, CBS 844 Ins68, and CBS 2199 T>C) were genotyped in children and their parents. Information on prepregnancy maternal folic acid supplement use was collected. ORs were estimated with unconditional logistic regression adjusted for frequency-matched variables and potential confounders. Case-parent trios were also analyzed. There was some evidence of a reduced risk of ALL among children who had, or whose father had, the MTRR 66GG genotype: ORs 0.60 [95% confidence interval (CI) 0.39-0.91] and 0.64 (95% CI, 0.40-1.03), respectively. The ORs for paternal MTHFR 677CT and TT genotypes were 1.41 (95% CI, 1.02-1.93) and 1.81 (95% CI, 1.06-3.07). ORs varied little by maternal folic acid supplementation. Some folate pathway gene polymorphisms in the child or a parent may influence ALL risk. While biologically plausible, underlying mechanisms for these associations need further elucidation. Folate pathway polymorphisms may be related to risk of childhood ALL, but larger studies are needed for conclusive results.

Highlights of This Issue

Bonn and colleagues investigated the effect of physical activity after a prostate cancer diagnosis in a large cohort. Statistically significantly lower overall mortality rates were found among men engaged in walking/bicycling ≥20 min/day, performing household work ≥1 h/day, or exercising ≥1 h/week, compared to less active men. Higher levels of physical activity were associated with reduced rates of overall and prostate cancer–specific mortality, further strengthening previous results indicating beneficial effects of physical activity on survival among men with prostate cancer.Fecal immunochemical testing (FIT) is one of the primary screening tests for colorectal cancer. Clarke and colleagues performed a meta-analysis to determine if uptake of FIT screening differs between men and women. Nineteen studies met the authors' inclusion criteria. Male FIT uptake was significantly lower than female uptake and this male/female difference persisted regardless of study design, screening organization, number of samples, age range, and setting. Further investigation is required to identify the factors that influence male nonparticipation in FIT screening.Milne and colleagues investigated associations between pediatric acute lymphoblastic leukemia (ALL) risk and folate pathway gene polymorphisms and their modification by maternal folic acid supplements. Seven folate pathway gene polymorphisms were genotyped in 392 pediatric ALL cases and pre-pregnancy maternal folic acid supplement use information was collected. The authors report some folate-pathway gene polymorphisms in the child or parent may influence ALL risk. Folate pathway polymorphisms may be related to risk of childhood ALL, but larger studies are needed for conclusive results.Schmit and colleagues searched for miRNA-related polymorphisms contributing to colorectal cancer etiology using the Axiom miRNA Target Site Genotyping Array containing 237,858 markers. The study included 596 cases from the Molecular Epidemiology of Colorectal Cancer study. The authors identified twenty-three markers with P values less than 5.0E–04 and replicated a previously published locus within the 3′-untranslated region of the insulin receptor gene INSR. This study demonstrates the potential for a miRNA-targeted genome-wide association study to identify candidate susceptibility loci and prioritize them for functional characterization.

Folate pathway gene MTHFR C677T polymorphism and risk of lung cancer in Asian populations.

Previous studies concerning the association between the 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism with lung cancer in Asian populations have provided inconclusive findings. A meta-analysis was performed to investigate a more reliable association between MTHFR C677T polymorphism and lung cancer in Asians. A comprehensive search was conducted to identify all case-control studies of MTHFR polymorphisms and lung cancer in Asia, using odds ratios (ORs) with 95% confidence intervals (CIs) to assess the strength of any association. Meta-analysis results suggested that the MTHFR C677T polymorphism contributed to an increased lung cancer risk in Asian populations (for T vs C: OR=1.11, 95%CI=1.0-1.23; for CT vs CC: OR= 1.1, 95%CI= 0.95-1.2 ; for TT+CT vs CC: OR=1.13, 95%CI=1.0-1.30; for TT vs CC: OR=1.25, 95%CI=1.01-1.30; for TT vs CT+CC: OR=1.16, 95%CI=1.0-1.36). MTHFR C677T polymorphism is significantly associated with lung cancer in Asians.

Genetic determinants involved in p-aminosalicylic acid resistance in clinical isolates from tuberculosis patients in northern China from 2006 to 2012.

p-Aminosalicylic acid (PAS) is an important compound for treating multidrug-resistant tuberculosis (TB). Previous studies showed that thyA mutations are often related to PAS resistance in clinical isolates. We performed a systematic analysis of isolate genotypes and detected mutations in three folate pathway genes (folC, thyA, and ribD) in 61.1% (127/208) of PAS-resistant isolates, including 11 double mutants. This result expands our knowledge about the distribution and frequency of mutations related to PAS resistance in mycobacterial clinical isolates.

Influence of the folate pathway and transporter polymorphisms on methotrexate treatment outcome in osteosarcoma.

Osteosarcoma is the most common primary bone malignancy that occurs mostly in adolescents. Treatment protocols usually include multiagent preoperative and postoperative chemotherapy based on methotrexate, cisplatin, doxorubicin and ifosfamide. Despite a favourable prognosis, there are considerable interindividual differences in treatment outcome. Genetic variability of enzymes involved in the metabolism and transport of methotrexate could contribute towards observed differences in response to chemotherapy. Our aim was to evaluate how polymorphisms in the folate pathway and transporter genes influence treatment outcome in osteosarcoma patients. In total, 44 osteosarcoma patients treated with methotrexate were genotyped for eleven polymorphisms in four folate pathway and five folate transporter genes. Cox regression was used in survival analysis. Logistic regression was used to assess the influence of polymorphisms on treatment efficacy and toxicity and nonparametric tests were used to determine the influence on serum methotrexate levels. Polymorphic SLCO1B1 rs4149056 and rs11045879 alleles were associated with significantly higher serum methotrexate area under the curve (P=0.001 and 0.011, respectively). Carriers of at least one polymorphic SLCO1B1 rs4149056 and rs11045879 allele tended to have longer event-free survival compared with patients with two wild-type alleles [P=0.040, hazard ratio (HR)=0.26, 95% confidence interval (CI)=0.07-0.94; and P=0.034, HR=0.20, 95% CI=0.05-0.89, respectively]. Compared with the most common haplotype, carriers of both polymorphic alleles had significantly longer event-free survival (P=0.009, HR=0.27, 95% CI=0.10-0.72). We have shown that SLCO1B1 polymorphisms influence methotrexate disposition and survival in methotrexate-treated osteosarcoma patients and therefore might serve as pharmacogenetic markers of treatment outcome.

Abstract 2228: Folate-related genes polymorphism and risk of pediatric acute lymphoplastic leukemia

Abstract Background: Childhood acute lymphoblastic leukemia (ALL) is the most common malignancy affecting children, constituting about 30% of all cancers among children. It constitutes about 75% of pediatric acute leukemia with peak incidence between ages 3 and 4. The assertion that ALL may have a genetic basis has long been pursued through association studies based on candidate genes as folate metabolism. Polymorphisms in folate pathway genes may influence the susceptibility to acute lymphoblastic leukemia. Increased risk of ALL was observed in reduced folate carrier protein (RFC1) 80GA variant carriers. A 1.4-fold reduction in ALL risk was observed for carriers of the methyl tetrahydrofolate reductase (MTHFR) 677T allele. Objectives: this study was carried out to evaluate the contribution of MTHFR C677T and RFC1 80GA gene polymorphism and susciptability of childhood acute lymphoblastic leukemia. Materials &amp;Methods: DNA was isolated from 200 children, divided into 2 groups, group I included 100 pediatric ALL patients and group II included 100 healthy donors as controls. Genotyping of MTHFR C677T and RFC1 G80A was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) using Hinf I and HhaI restriction endonuclease respectively. Results: MTHFR 677T allele carriers were significantly lower in ALL cases (46%) than healthy controls (56%). Reduction in ALL risk was observed for heterozygous (CT) or homozygous (TT) carriers of the MTHFR 677T allele (OR 0.8; 95% CI, 0.9-1.5; P &amp;lt; 0.002). RFC1 80A allelic carriers have an increased susceptibility to ALL. Risk was increased 2.0 times (OR 3.5; 95% CI, 1.5-4.8 ; P .02) for A-allelic carriers. Conclusion: our data suggested that the MTHFR gene variants are associated with decreased ALL rate and risk. the reduced risk associated with the MTHFR C677T polymorphisms may be the result of changed intracellular folate redistribution. the results of our study also supported the suggestion that RFC1 G80A RFC1 G80A single nucleotide polymorphism contributed to increase the susceptibility and the development of pediatric ALL. Citation Format: Nermin Raafat, Amal Gharib, Usama Elsafy, Tamer Hassan. Folate-related genes polymorphism and risk of pediatric acute lymphoplastic leukemia. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2228. doi:10.1158/1538-7445.AM2014-2228

Interaction Between Snps In Folate Pathway Genes and Environment Increase Neural Tube Defects Risk

Evaluation of: Liu J, Qi J, Yu X et al. Investigations of single nucleotide polymorphisms in folate pathway genes in Chinese families with neural tube defects. J. Neurol. Sci. 337, 61–66 (2014). This study investigated the interactions between SNPs in folate metabolism pathway genes and environmental risk factors on the etiology of neural tube defects (NTDs). Samples from a total of 609 NTD cases were collected from 602 families, 1106 parental samples were collected as controls. A total of 28 SNPs in 12 folate pathway genes were genotyped. Environmental factors included folate supplementation, gestational diabetes mellitus (GDM) and medicine administration before and during pregnancy. Case–parental control and transmission/disequilibrium tests (TDTs) were conducted according to environment cofactor stratification. The MTHFR 677C&gt;T genotype interacts with low folate level and GDM, increasing the occurrence of NTDs. MTR (known as MTHM in the paper under evaluation) 501A&gt;G interacts with GDM, promoting NTDs risk. BHMT 716G&gt;A, in the case of no folate supplementation, contributed to the etiology of NTDs.