Association of microRNA Polymorphisms with Toxicities Induced by Methotrexate in Children with Acute Lymphoblastic Leukemia

Methotrexate (MTX), a structurally related substance to folic acid, is an important chemotherapeutic agent used for decades in the treatment of pediatric acute lymphoblastic leukemia (ALL) and other types of cancer as non-Hodgkin lymphomas and osteosarcomas. Despite the successful outcomes observed, the primary drawback is the variability in the pharmacokinetics and pharmacodynamics between patients. The main adverse events related to its use are nephrotoxicity, mucositis, and myelosuppression, especially when used in high doses. The potential adverse reactions and toxicities associated with MTX are a cause for concern and may lead to dose reduction or treatment interruption. Genetic variants in MTX transport genes have been linked to toxicity. Pharmacogenetic studies conducted in the past focused on single nucleotide polymorphisms (SNPs) in the coding and 5'-regulatory regions of genes. Recent studies have demonstrated a significant role of microRNAs (miRNAs) in the transport and metabolism of drugs and in the regulation of target genes. In the last few years, the number of annotated miRNAs has continually risen, in addition to the studies of miRNA polymorphisms and MTX toxicity. Therefore, the objective of the present study is to investigate the role of miRNA variants related to MTX adverse effects.

Association Between the Individual and Combined Effects of the GSTM1 and GSTT1 Polymorphisms and Risk of Leukemia: A Meta-Analysis

Background: Fourteen meta-analyses reported the individual effects of the GSTM1 and GSTT1 polymorphisms on leukemia risk. However, over 40 studies were not included in previously published meta-analyses. Moreover, one key aspect was that previous meta-analyses did not conduct the false-positive test on the aforementioned issues. Furthermore, previous meta-analyses did not observe the combined effects of GSTM1 present/null and GSTT1 present/null polymorphism with leukemia risk. Therefore, we conducted the current study to further analyze these associations.

Objectives: This study aimed to investigate the association between the individual and combined effects of the GSTM1 present/null and GSTT1 present/null polymorphisms and the risk of leukemia.

Methods: A meta-analysis was performed applying Meta-analyses of Observational Studies in Epidemiology (MOOSE) guidelines. Moreover, false-positive report probability (FPRP) and Bayesian false discovery probability (BFDP) were applied to investigate the false-positive results.

Results: The individual GSTM1 and GSTT1 null genotypes and combined effects of the two genes were associated with a significantly increased leukemia risk in overall and several subgroup analyses, such as Asians, Caucasians, and so on. Then, further analysis was conducted using FPRP and BFDP. Significant associations were considered as “positive” results on the GSTM1 null genotype with leukemia risk in overall populations (FPRP < 0.001 and BFDP = 0.006), Asians (FPRP < 0.001 and BFDP < 0.001), and East Asian population (FPRP < 0.001 and BFDP = 0.002). For the GSTT1 null genotype, significant associations were regarded “positive” results in overall populations, acute myeloid leukemia (AML), Asians, and East Asian population. For the combined effects of the GSTM1 and GSTT1 polymorphisms, significant associations were also considered “positive” results in the overall analysis of Asians, Indians, and East Asian population.

Conclusion: This study strongly indicates that the individual GSTM1 and GSTT1 null genotypes and combined effects of the two genes are associated with increased leukemia risk in Asians, especially in the East Asian population; the GSTT1 null genotype is associated with increased AML risk; the combined effects of the two genes are associated with increased leukemia risk in Indians.

Cancer risk and nullity of Glutathione-S-transferase mu and theta 1 in occupational pesticide workers

Occupational exposure to pesticides has been associated with adverse health conditions, including genotoxicity and cancer. Nullity of GSTT1/GSTM1 increases the susceptibility of pesticide workers to these adverse health effects due to lack of efficient detoxification process created by the absence of these key xenobiotic metabolizing enzymes. However, this assertion does not seem to maintain its stance at all the time; some pesticide workers with the null genotypes do not present the susceptibility. This suggests the modulatory role of other confounding factors, genetic and environmental conditions. Pesticides, aggravated by the null GSTT1/GSTM1, cause genotoxicity and cancer through oxidative stress and miRNA dysregulation. Thus, the absence of these adverse health effects together with the presence of null GSTT1/GSTM1 genotypes demands further explanation. Also, understanding the mechanism behind the protection of cells - that are devoid of GSTT1/GSTM1 - from oxidative stress constitutes a great challenge and potential research area. Therefore, this review article highlights the recent advancements in the presence and absence of cancer risk in occupational pesticide workers with GSTT1 and GSTM1 null genotypes.

Involvement of MTHFR rs1801133 in the Susceptibility of Acute Lymphoblastic Leukemia: A Preliminary Study

BACKGROUND

Acute lymphoblastic leukemia (ALL), a common blood cancer, is characterized by the interaction between genetic and environmental factors. Several variants of the Methylenetetrahydrofolate reductase (MTHFR), mainly the C677T (rs1801133), may affect susceptibility to ALL.

AIM OF THE STUDY

The authors conducted this case-control study to evaluate the relationship between this variant of the MTHFR gene and the risk of ALL.

MATERIALS AND METHODS

Forty-one patients with ALL and 35 non-ALL controls recruited in this study were genotyped utilizing polymerase chain reaction-restriction fragment length polymorphism methodology.

RESULTS

The MTHFR 677CT genotype was significantly more frequently found in patients with ALL having a 2-fold increase in risk (P <0.01).

CONCLUSION

Our results suggest that rs1801133 of MTHFR is a predictive risk marker to ALL in Tunisian ALL.

Lack of Impact of the A1298C MTHFR on the Risk of Childhood Acute Lymphoblastic Leukemia: Evidence from a Meta-analysis

To clarify the effect of the A1298C variant of methylenetetrahydrofolate reductase (MTHFR) gene on the risk of acute lymphoblastic leukemia (ALL), an updated meta-analysis was performed. Electronic literature search was carried out in PubMed to collect relevant articles. Pooled odds ratios (OR) and stratification analysis were achieved under different genetic comparison models, age and ethnicity. A total of 46 articles including 7020 cases and 12,114 controls were enrolled. Overall, no significant association was observed for the MTHFR A1298C variant on the risk of ALL in any genetic model test, when all the studies pooled together (OR ~ 1 0.91; p > 0.05). In subgroup analyses stratified by age and ethnicity, the MTHFR A1298C reduce the risk of ALL in adult under allele contrast (OR = 0.88; [0.72; 1.09], p = 0.23) mainly in Caucasian populations. The present meta-analysis provides evidence that the A1298C variant of MTHFR gene is unlikely to be a major risk gene for childhood ALL.

The prevalence and clinical relevance of 2R/2R TYMS genotype in patients with gastrointestinal malignancies treated with fluoropyrimidine-based chemotherapy regimens

Introduction

The prevalence of 2R/2R TYMS genotype is variable but estimated to be around 20–30% in Caucasians. The clinical relevance of TYMS 2R/2R genotype in predicting severe fluoropyrimidine-related adverse events (FrAE) is controversial. Here, we explored the prevalence and clinical relevance of 2R/2R TYMS genotype.

Methods

Between 2011 and 2018, 126 patients were genotyped for TYMS. FrAEs were graded according to CTCAE version 5.0. Fisher’s exact test was used for statistical analysis.

Results

The prevalence of TYMS 2R/2R genotype was 24.6%. Among patients with TYMS genotypes (N = 71) that predict decreased TS expression, 2R/2R TYMS genotype was the most common TYMS genotype seen in female (57%) and African American (60%) patients. Among patients with genotypes that predict increased TS expression (N = 55), 12 patients had grade 3–4 FrAEs (22%), while among patients with genotypes that predict decreased TS expression (N = 71), 30 patients had grade 3–4 FrAEs (42%) (p = 0.0219). Compared to patients with genotypes predicting increased TS expression, 17 out of 31 patients (55%) with TYMS 2R/2R genotype had grade 3–4 FrAEs (p = 0.0039) and 15 out 40 patients (38%) with TYMS 2R/3RC and TYMS 3RC/3RC genotype had grade 3–4 FrAEs (p = 0.1108).

Conclusion

The prevalence of TYMS 2R/2R genotype was 24.6%, and it had a unique sex and ethnic distribution. Polymorphism in the promoter region of TYMS gene that predicts decreased TS expression due to 2R/2R variant was associated with grade 3–4 FrAEs. These data suggest that genotyping patients who are not DPD deficient for TYMS might identify patients at risk of severe FrAEs.

Assessment of the relationship between methylenetetrahydrofolate reductase polymorphism and acute lymphoblastic leukemia: Evidence from an updated meta-analysis

OBJECTIVE

The methylenetetrahydrofolate reductase gene C677T polymorphism is closely related to the acute lymphoblastic leukemia. Several case-control studies have investigated this association; however, no conclusions could be drawn. A comprehensive updated meta-analysis is established to explain these contradictions and clarify the overall impact of this variant on the susceptibility to acute lymphoblastic leukemia.

METHODS

Electronic searches were conducted to select published studies prior to June 2018. Pooled odds ratios and stratification analysis were performed under different genetic comparison models, age, and ethnicity.

RESULTS

Totally, 66 case-control studies including 9619 acute lymphoblastic leukemia cases and 17,396 controls were selected. Our analyses showed that methylenetetrahydrofolate reductase C677T polymorphism was protective mainly in Asian and European countries, under all genetic models and regardless of age, but leukemogenic in mixed population.

CONCLUSION

Thus, C677T polymorphism may be a promising acute lymphoblastic leukemia biomarker, but they should be interpreted with caution considering other factors such as folic acid intake, gene-gene and gene-environment interactions.

GSTT1 and GSTM1 null variants in Mestizo and Amerindian populations from northwestern Mexico and a literature review

The GSTT1 and GSTM1 genes are key molecules in cellular detoxification. Null variants in these genes are associated with increase susceptibility to developing different types of cancers. The aim of this study was to determine the prevalence of GSTT1 and GSTM1 null genotypes in Mestizo and Amerindian individuals from the Northwestern region of Mexico, and to compare them with those reported worldwide. GSTT1 and GSTM1 null variants were genotyped by multiplex PCR in 211 Mestizos and 211 Amerindian individuals. Studies reporting on frequency of GSTT1 and GSTM1 null variants worldwide were identified by a PubMed search and their geographic distribution were analyzed. We found no significant differences in the frequency of the null genotype for GSTT1 and GSM1 genes between Mestizo and Amerindian individuals. Worldwide frequencies of the GSTT1 and GSTM1 null genotypes ranges from 0.10 to 0.51, and from 0.11 to 0.67, respectively. Interestingly, in most countries the frequency of the GSTT1 null genotype is common or frequent (76%), whereas the frequency of the GSMT1 null genotype is very frequent or extremely frequent (86%). Thus, ethnic-dependent differences in the prevalence of GSTT1 and GSTM1 null variants may influence the effect of environmental carcinogens in cancer risk.

Associations of NQO1 C609T and NQO1 C465T polymorphisms with acute leukemia risk: a PRISMA-compliant meta-analysis

Objective

The NAD(P)H:quinone oxidoreductase (NQO1) C609T and C465T polymorphisms have been widely thought to be associated with the risk of acute leukemia (AL) in recent years, but the correlations are still unclear. A meta-analysis is generally acknowledged as one of the best methods for secondary research, and so it was applied in this study with the aim of elucidating how the NQO1 C609T and C465T polymorphisms are related to the risk of AL.

Methods

Relevant studies were searched in the PubMed, EMBASE, CNKI, and Wanfang databases, and the obtained data were analyzed using Stata (version 12.1). The allele-contrast model was applied, and odds ratios (ORs) with 95% confidence intervals (CIs) were used to evaluate relationship strengths. Meta-regression was used to identify sources of heterogeneity, and subgroup analyses were conducted. Publication bias was analyzed using funnel plots, with the trim-and-fill method used to analyze the effect of publication bias on pooled results. In addition, sensitivity analysis, the fail-safe number method, and cumulative analysis by publication year were performed to measure the stability of the obtained results.

Results

This meta-analysis included 28 relevant studies involving 5,953 patients and 8,667 controls. Overall, the C609T polymorphism was associated with the risk of acute lymphoblastic leukemia (ALL; OR =1.18, 95% CI =1.00–1.39, P=0.05). Meanwhile, race was found to be a potential source of heterogeneity for the relationship between the C609T polymorphism and acute myeloid leukemia (AML) risk, and the subgroup analysis identified the C609T polymorphism as a risk factor for AML in Asians (OR =1.34, 95% CI =1.03–1.74, P=0.03). The number of studies about C465T polymorphism was too small to pool the data.

Conclusion

There are increased risks of ALL in all subjects and of AML in Asians for carriers of the NQO1 C609T polymorphism. Further studies are needed to verify the associations of the C465T polymorphism with the risk of AL.

TSER polymorphism is not associated with risk of pediatric acute lymphoblastic leukemia: A meta-analysis

BACKGROUND

Accumulating studies have explored the effect of thymidylate synthase enhancer region (TSER) variation on risk of pediatric acute lymphoblastic leukemia (ALL) with controversial results. Therefore, this quantitative meta-analysis was performed to assess synthetically the association of TSER variation with susceptibility to develop pediatric ALL.

METHODS

The PubMed, ScienceDirect, Google Scholar, Wanfang Database, and China National Knowledge Infrastructure were systematically retrieved to obtain the published case-control studies about the relationship between TSER variation and pediatric ALL risk. The quality assessment of the included studies was preformed and relevant information was collected. Odds ratios (ORs) and 95% confidence intervals (CIs) were applied to evaluate the strength of association.

RESULTS

This meta-analysis finally included 2681 children with ALL and 3854 matched controls from 11 investigations. The quantitative synthesis results found no significant association between TSER variation and susceptibility to pediatric ALL in overall comparisons under 5 genetic models (2R/3R vs 3R/3R: OR = 0.95, 95% CI = 0.84-1.07, P = 0.41; 2R/2R vs 3R/3R: OR = 0.99, 95% CI = 0.84-1.16, P = 0.90; 2R2R vs 3R/3R+2R/3R: OR = 1.05, 95% CI = 0.92-1.21, P = 0.45; 2R/3R+2R/2R vs 3R/3R: OR = 0.97, 95% CI = 0.87-1.09, P = 0.63; 2R vs 3R: OR = 1.03, 95% CI = 0.92-1.15, P = 0.61). Similarly, there was no significant association existed in the stratification analyses according to ethnicity, control source, and quality score.

CONCLUSION

This meta-analysis shows that TSER variation is not related to the development risk of pediatric ALL.

Association of methylenetetrahydrofolate reductase gene-gene interaction and haplotype with susceptibility to acute lymphoblastic leukemia in Chinese children

The aim of this study was to investigate the association of methylenetetrahydrofolate reductase (MTHFR) gene polymorphism and additional gene-gene interaction with acute lymphoblastic leukemia (ALL) risk. Logistic regression was performed to investigate the association between two single nucleotide polymorphisms (SNPs) within MTHFR gene and ALL risk and additional gene-gene interaction between rs1801133 and rs1801131. The minor allele of rs1801133 and rs1801131 is associated with decreased ALL risk, OR (95% CI) were 0.61 (0.38-0.89), and 0.68 (0.50-0.96), respectively. We also found a significantly interaction between the two SNPs, participants with rs1801133 - CT or TT and rs1801131 - AC or CC genotype have the lowest ALL risk, compared with participants with rs1801133 - CC and rs1801131 - AA genotype, OR (95% CI) was 0.32 (0.12-0.63). We did not find any haplotype between the rs1801133 and rs1801131 associated with ALL risk. rs1801133 and rs1801131 within MTHFR gene and their interaction were both associated with ALL risk in Chinese children.

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.

Genetic susceptibility in childhood acute leukaemias: a systematic review

Acute leukaemias (AL) correspond to 25-35% of all cancer cases in children. The aetiology is still sheltered, although several factors are implicated in causality of AL subtypes. Childhood acute leukaemias are associated with genetic syndromes (5%) and ionising radiation as risk factors. Somatic genomic alterations occur during fetal life and are initiating events to childhood leukaemia. Genetic susceptibility has been explored as a risk factor, since environmental exposure of the child to xenobiotics, direct or indirectly, can contribute to the accumulation of somatic mutations. Hence, a systematic review was conducted in order to understand the association between gene polymorphisms and childhood leukaemia risk. The search was performed in the electronic databases PubMed, Lilacs, and Scielo, selecting articles published between 1995 and 2013. This review included 90 case-control publications, which were classified into four groups: xenobiotic system (n = 50), DNA repair (n = 16), regulatory genes (n = 15), and genome wide association studies (GWAS) (n = 9). We observed that the most frequently investigated genes were: NQO1, GSTM1, GSTT1, GSTP1, CYP1A1, NAT2, CYP2D6, CYP2E1, MDR1 (ABCB1), XRCC1, ARID5B, and IKZF1. The collected evidence suggests that genetic polymorphisms in CYP2E1, GSTM1, NQO1, NAT2, MDR1, and XRCC1 are capable of modulating leukaemia risk, mainly when associated with environmental exposures, such as domestic pesticides and insecticides, smoking, trihalomethanes, alcohol consumption, and x-rays. More recently, genome wide association studies identified significant associations between genetic polymorphisms in ARID5B e IKZF1 and acute lymphoblastic leukaemia, but only a few studies have replicated these results until now. In conclusion, genetic susceptibility contributes to the risk of childhood leukaemia through the effects of gene-gene and gene-environment interactions.

Prenatal recruitment of participants for a birth cohort study including cord blood collection: results of a feasibility study in Bremen, Germany

BACKGROUND

Prospective birth cohort studies comprising follow up of children from pregnancy or birth over a long period of time, and collecting various biological samples at different times through the life-course offer a promising approach to enhance etiologic knowledge of various diseases. Especially for those where early lifetime exposures and conditions are thought to play an important role. The collection and storage of biological samples is a critical component in epidemiological studies, notably for research regarding prenatal exposures to various environmental factors as well as for DNA extraction. Our feasibility study for a birth cohort within the scope of etiology of childhood leukemia with prospective sampling of mothers and their future newborns aimed to investigate the willingness of pregnant women to participate in a birth cohort study involving collection of blood and umbilical cord blood samples. The overall aim was to develop practice-based research recommendations for a possible German birth cohort study.

METHODS

The study was conducted in Bremen, Germany, between January 2012 and March 2013. Pregnant women were eligible for recruitment if (i) their expected date of delivery was during the study recruitment phase (September 2012-February 2013), (ii) they planned to give birth at the cooperating hospital's obstetric unit and (iii) their knowledge of the German language was sufficient to understand study materials, details of participation and to fill out the prenatal self-administered questionnaire. Maternal blood and umbilical cord blood samples to be used for later research activities were collected and stored at a stem cell bank already collaborating with the hospital. 22 primary care gynecologists were invited to enroll pregnant women for the study and cooperation with one hospital was established. Expectant women were recruited during the last trimester of pregnancy, either during one of their prenatal care visits at their primary care gynecologist or later on in hospital by the attending obstetricians or project staff.

RESULTS

Of the 22 invited primary care gynecologists requested to enroll pregnant women for the study, 8 gynecologists actually collaborated. A total of 200 eligible women were invited to participate in the study, 48 (24%) of whom agreed. 34 women were enrolled by primary care gynecologists, with one gynecologist enrolling 26 women. Twelve of 14 women recruited via hospitals were enrolled by study staff. A total of 41 women consented to the collection of umbilical cord blood and maternal blood samples, and samples could be stored for 54% of them. Reason for non-participation were the uncertainty whether or not the full study would be conducted and the fact that the participants were not willing to decide for their children whether or not genetic information (cord blood) can be stored for research purposes.

CONCLUSION

Enrolling parents in a birth cohort study that includes biosampling is a challenge, but participation can be improved through close collaboration with primary care gynecologists and maternity hospitals. Cord blood collection may impede participation, especially when maternity hospitals offer an alternative option for cord blood donation.

The association of methylenetetrahydrofolate reductase genotypes with the risk of childhood leukemia in Taiwan

Background

Acute lymphoblastic leukemia (ALL) is the most prevalent type of pediatric cancer, the causes of which are likely to involve an interaction between genetic and environmental factors. To evaluate the effects of the genotypic polymorphisms in methylenetetrahydrofolate reductase (MTHFR) on childhood ALL risk in Taiwan, two well-known polymorphic genotypes of MTHFR, C677T (rs1801133) and A1298C (rs1801131), were analyzed to examine the extent of their associations with childhood ALL susceptibility and to discuss the MTHFR genotypic contribution to childhood ALL risk among different populations.

Methodology/Principal Findings

In total, 266 patients with childhood ALL and an equal number of non-cancer controls recruited were genotyped utilizing PCR-RFLP methodology. The MTHFR C677T genotype, but not the A1298C, was differently distributed between childhood ALL and control groups. The CT and TT of MTHFR C677T genotypes were significantly more frequently found in controls than in childhood ALL patients (odds ratios=0.60 and 0.48, 95% confidence intervals=0.42–0.87 and 0.24–0.97, respectively). As for gender, the boys carrying the MTHFR C677T CT or TT genotype conferred a lower odds ratio of 0.51 (95% confidence interval=0.32–0.81, P=0.0113) for childhood ALL. As for age, those equal to or greater than 3.5 years of age at onset of disease carrying the MTHFR C677T CT or TT genotype were of lower risk (odds ratio= 0.43 and 95% confidence interval=0.26–0.71, P=0.0016).

Conclusions

Our results indicated that the MTHFR C677T T allele was a protective biomarker for childhood ALL in Taiwan, and the association was more significant in male patients and in patients 3.5 years of age or older at onset of disease.

Association between MTHFR C677T polymorphism and risk of acute lymphoblastic leukemia: a meta-analysis based on 51 case-control studies

Background

Studies and systematic reviews have reached inconsistent conclusions on the role of 5, 10-methylenetetrahydrofolate reductase (MTHFR) polymorphism C677T in acute lymphoblastic leukemia (ALL) risk.

Material/Methods

The present meta-analysis comprising of 51 case-control studies, including 7892 cases and 14 280 controls was performed to reevaluate the association between MTHFR C677T polymorphism and ALL risk.

Results

Statistical differences were found in the dominant model (TT+CT vs. CC, odd ratio (OR)=0.89, 95% CI, 0.79–1.00, P=0.04) and the CT vs. CC (OR=0.89, 95% CI, 0.80–1.00, P=0.05), but not in the allele contrast model (T vs. C, OR=0.92, 95% CI, 0.84–1.01, P=0.08), additive model (TT vs. CC, OR=0.87, 95% CI, 0.73–1.05, P=0.15), or recessive model (TT vs. CT+CC, OR=0.94, 95% CI, 0.81–1.10, P=0.44) in overall populations. In the subgroup analyses stratified by age (children and adults) and ethnicity (Asian and Caucasian), no significant associations between MTHFR C677T polymorphism and ALL risk were observed.

Conclusions

The current study found no sufficient evidence of a protective role of MTHFR C677T polymorphism in ALL susceptibility.

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

BACKGROUND

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).

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

IMPACT

Folate pathway polymorphisms may be related to risk of childhood ALL, but larger studies are needed for conclusive results.

Glutathione-S-transferase polymorphisms (GSTM1, GSTT1 and GSTP1) and acute leukemia risk in Asians: a meta-analysis

The association between glutathione-S-transferase polymorphisms (GSTM1, GSTT1 and GSTP1) and risk of acute leukemia in Asians remains controversial. This study was therefore designed to evaluate the precise association in 23 studies identified by a search of PubMed and several other databases, up to December 2013. Using random or fixed effects models odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were calculated. Heterogeneity across studies was assessed, and funnel plots were constructed to test for publication bias. The meta-analysis showed positive associations between GST polymorphisms (GSTM1 and GSTT1 but not GSTP1) and acute leukemia risk [(OR=1.47, 95% CI 1.18-1.83); (OR=1.32, 95% CI 1.07-1.62); (OR=1.01, 95% CI 0.84-1.23), respectively] and heterogeneity between the studies. The results suggested that the GSTM1 null genotype and GSTT1null genotype, but not the GSTP1 polymorphism, might be a potential risk factors for acute leukemia. Further well-designed studies are needed to confirm our findings.

Multiple analytical approaches demonstrate a complex relationship of genetic and nongenetic factors with cisplatin- and carboplatin-induced nephrotoxicity in lung cancer patients

Background. Cisplatin and carboplatin cause nephrotoxicity by forming platinum-DNA adducts and lead to cell death. Methods. One-hundred and sixteen Taiwanese lung cancer patients who received cisplatin or carboplatin more than twice were recruited, and their genotypes were determined. The risk of renal dysfunction, injury to the kidney, failure of kidney function, loss of kidney function, and end-stage kidney disease (RIFLE) criteria were used to evaluate the occurrence of nephrotoxicity. A logistic regression, multiple regression with a classification and regression tree (CART), and the Framingham study risk score were used to analyze interactions between genetic and nongenetic factors in producing platinum-induced nephrotoxicity. Results. ERCC1 118C and TP53 72Arg polymorphisms were associated with increased risks of platinum-induced nephrotoxicity. Other risk factors found included the platinum type, baseline serum creatinine (Scr), coadministration of vinorelbine, and the number of chemotherapy cycles. The overall prediction rate of the CART was 82.7%, with a sensitivity of 0.630 and specificity of 0.896. The Framingham study risk prediction model contained 7 factors. Its prediction rate was 84.5%, with a sensitivity of 0.643 and specificity of 0.909. Conclusions. Genetic polymorphisms of ERCC1 and TP53 are risk factors for nephrotoxicity. The CART analysis may provide a clinically applicable model to predict the risk of cisplatin- and carboplatin-induced nephrotoxicity.

Glutathione-S-transferase polymorphism and acute lymphoblastic leukemia (ALL) in north Indian children: a case-control study and meta-analysis

Various studies on association of glutathione S-transferase (GST) polymorphisms and childhood acute lymphoblastic leukemia (ALL) have yielded conflicting results. We examined this association among north Indian children and conducted an updated meta-analysis to overcome sample size-related limitations. GSTM1, GSTP1 and GSTT1 genotypes in 100 children with ALL and 300 healthy controls were compared. GSTT1 null mutation (odds ratio (OR) 2.54, 95% confidence interval (CI) 1.50-4.32) and GSTP1 homozygous mutation (OR 3.13, 95%CI 1.48-6.59) were found to increase the risk of childhood ALL, while GSTM1 did not alter the risk. Meta-analysis included 22, 10 and 20 studies examining the association of childhood ALL with GSTM1, GSTP1 and GSTT1 genotypes, respectively. Only GSTM1 genotype (OR 1.29, 95%CI 1.10-1.62) was associated with increased risk in the overall analysis. However, both GSTM1 (OR 1.54, 95%CI 1.12-2.10) and GSTT1 (OR 1.63, 95%CI 1.32-1.99) null genotypes were associated with increased risk in Asian subjects. The risk of developing childhood ALL was not associated with GSTP1 genotype.

Effects of the NQO1 609C>T polymorphism on leukemia susceptibility: evidence from a meta-analysis

A functional polymorphism in the NQO1 gene, featuring a 609C>T substitution,leading to proline to serine amino-acid and enzyme activity changes, has been implicated in cancer risk. However, individually published investigations showed inconclusive results, especially for leukemia. In this study, we therefore performed a meta- analysis of 21 publications with a total of 3,634 cases and 4,827controls, mainly for leukemia. We summarized the data on the association between the NQO1 609C>T polymorphism and risk of leukemia and performed subgroup analyses by ethnicity and leukemia type. We found that the variant TT homozygous genotype o was associated with a modestly increased risk of leukemia (TT versus CT/CC: OR = 1.23, 95%CI = 1.00 - 1.51, heterogeneity = 0.76; I2 = 0%). Following further stratified analyses, increased risk was only observed in subgroups of Caucasians. This meta-analysis suggests that the NQO1 609T allele is a high-penetrance risk factor for leukemia in Caucasians. The effect on leukemia may be modified by ethnicity and leukemia type, and the small sample sizes of the subgroup analyses suggest that further larger studies are needed.

MTHFR gene polymorphism in acute lymphoblastic leukemia among North Indian children: a case-control study and meta-analysis updated from 2011

Studies on the association of methylenetetrahydrofolate reductase (MTHFR) genotype in childhood acute lymphoblastic leukemia (ALL) have yielded conflicting results. The present study examines this association in north Indian children with ALL and includes an updated meta-analysis. MTHFR (677 and 1298) genotype of children with ALL and healthy adult controls were done by the PCR-restriction fragment length polymorphism (PCR-RFLP) method and were compared using various models of inheritance. A total of 150 patients and 300 controls were included. The 677T allele was found protective (odds ratio (OR) 0.21, 95% confidence interval (CI) 0.04-0.94), whereas 1298C allele led to an increase in risk (OR 4.44, 95% CI 2.19-8.99) of childhood ALL. Meta-analysis included 31 and 27 studies examining the association of 677 and 1298 genotypes, respectively. The 677 C -> T polymorphism was protective (OR 0.90, 95% CI 0.82-0.99). Protection was more pronounced in folate-sufficient populations as compared with those not covered by folate fortification guidelines. The 1298A->C polymorphism was associated with a marginal increase in risk (OR 1.19, 95% CI 1.01-1.40).

Association between NQO1 C609T polymorphism and acute lymphoblastic leukemia risk: evidence from an updated meta-analysis based on 17 case-control studies

PURPOSE

Quinone oxidoreductase (NQO1) C609T polymorphisms have been implicated in acute lymphoblastic leukemia (ALL) risk, but previously published studies were inconsistent and recent meta-analyses were not adequate. The aim of this study was to determine more precise estimations for the relationship between the NQO1 C609T polymorphism and the risk of ALL.

METHODS

Electronic searches for all publications were conducted on association between this variant and ALL in several databases updated in May 2013. The quality of studies was evaluated using the Newcastle-Ottawa Scale. Crude odds ratios (ORs) with 95 % confidence intervals (CIs) were used to assess the strength of the association. Seventeen studies were identified, including 2,264 ALL patients and 3,798 controls.

RESULTS

Overall, significantly elevated ALL risk was associated with NQO1 C609T variant genotypes when all of the studies were pooled into the meta-analysis (TT vs. CC: OR 1.46, 95 % CI 1.18-1.79; dominant model: OR 1.45, 95 % CI 1.19-1.77). In the subgroup analysis by ethnicity, significantly increased risks were found for non-Asians (T/T vs. C/C: OR 1.74, 95 % CI 1.29-2.36; dominant model: T/T + C/T vs. C/C: OR 1.7, 95 % CI 1.27-2.29). When stratified by adult or children studies, statistically significantly elevated risks were found among adult studies (codominant model: C/T vs. C/C: OR 1.38, 95 % CI 1.02-1.87; dominant model: T/T + C/T vs. C/C: OR 1.52, 95 % CI 1.18-1.97) and children studies (recessive model: T/T vs. C/T + C/C: OR 1.34, 95 % CI 1.05-1.7).

CONCLUSIONS

Our results indicate that the C609T polymorphism of the NQO1 gene is an important genetic risk factor in ALL.

GSTT1 genetic polymorphism and susceptibility to childhood acute lymphoblastic leukemia: a meta-analysis

Glutathione S-transferase T1 (GSTT1) genetic polymorphism has been considered as a risk factor for developing malignant diseases including acute lymphoblastic leukemia; however, the results from previous studies are inconsistent. We performed a meta-analysis of 16 published studies to investigate the association between GSTT1 null variant and risk of acute lymphoblastic leukemia in childhood. Between-study heterogeneity was assessed using the I (2) statistic method. Odds ratios (ORs) with corresponding 95 % confidence intervals (95 %CI) were pooled to assess the association. Those 16 studies were from 14 publications and included a total of 2,424 cases and 3,447 controls. Meta-analysis of a total of 16 studies showed that GSTT1 null variant was significantly associated with risk of childhood acute lymphoblastic leukemia (fixed-effect OR = 1.22, 95 %CI 1.07-1.39, P = 0.003, I (2) = 35 %). Subgroup analysis showed that GSTT1 null variant was significantly associated with risk of childhood acute lymphoblastic leukemia in Asians (fixed-effect OR = 1.47, 95 %CI 1.16-1.85, P = 0.001, I (2) = 0 %). However, there was no obvious association in both Caucasians (random-effect OR = 1.07, 95 %CI 0.83-1.38, P = 0.59, I (2) = 53 %) and Africans (random-effect OR = 0.99, 95 %CI 0.31-3.10, P = 0.98, I (2) = 72 %). Therefore, the GSTT1 null variant is significantly associated with susceptibility to childhood acute lymphoblastic leukemia in Asians.

GSTM1 and GSTT1 null polymorphisms and childhood acute leukemia risk: evidence from 26 case-control studies

Several molecular epidemiological studies have been conducted to examine the association between glutathione S-transferase mu-1 (GSTM1) and glutathione S-transferase theta-1 (GSTT1) null polymorphisms and childhood acute leukemia; however, the conclusions remain controversial. We performed an extensive meta-analysis on 26 published case-control studies with a total of 3252 cases and 5024 controls. Crude odds ratios (ORs) with 95% confidence interval were used to assess the strength of association between childhood acute leukemia risk and polymorphisms of GSTM1 and GSTT1. With respect to GSTM1 polymorphism, significantly increased risk of childhood acute leukemia was observed in the overall analysis (OR = 1.30; 95%CI, 1.11-1.51). Furthermore, a stratification analysis showed that the risk of GSTM1 polymorphism are associated with childhood acute leukemia in group of Asians (OR = 1.94; 95%CI, 1.53-2.46), Blacks (OR = 1.76; 95%CI, 1.07-2.91), ALL (OR = 1.33; 95%CI, 1.13-1.58), '< 100 cases and <100 controls' (OR = 1.79; 95%CI, 1.21-2.64), '≥ 100 cases and ≥ 100 controls' (OR = 1.25; 95%CI, 1.02-1.52), and population-based control source (OR = 1.40; 95%CI, 1.15-1.69). With respect to GSTT1 polymorphism, significant association with childhood acute leukemia risk was only found in subgroup of Asian. This meta-analysis supports that GSTM1 null polymorphism is capable of causing childhood acute leukemia susceptibility.

Roles of genetic polymorphisms in the folate pathway in childhood acute lymphoblastic leukemia evaluated by Bayesian relevance and effect size analysis

In this study we investigated whether polymorphisms in the folate pathway influenced the risk of childhood acute lymphoblastic leukemia (ALL) or the survival rate of the patients. For this we selected and genotyped 67 SNPs in 15 genes in the folate pathway in 543 children with ALL and 529 controls. The results were evaluated by gender adjusted logistic regression and by the Bayesian network based Bayesian multilevel analysis of relevance (BN-BMLA) methods. Bayesian structure based odds ratios for the relevant variables and interactions were also calculated. Altogether 9 SNPs in 8 genes were associated with altered susceptibility to ALL. After correction for multiple testing, two associations remained significant. The genotype distribution of the MTHFD1 rs1076991 differed significantly between the ALL and control population. Analyzing the subtypes of the disease the GG genotype increased only the risk of B-cell ALL (p = 3.52×10⁻⁴; OR = 2.00). The GG genotype of the rs3776455 SNP in the MTRR gene was associated with a significantly reduced risk to ALL (p = 1.21×10⁻³; OR = 0.55), which resulted mainly from the reduced risk to B-cell and hyperdiploid-ALL. The TC genotype of the rs9909104 SNP in the SHMT1 gene was associated with a lower survival rate comparing it to the TT genotype (80.2% vs. 88.8%; p = 0.01). The BN-BMLA confirmed the main findings of the frequentist-based analysis and showed structural interactional maps and the probabilities of the different structural association types of the relevant SNPs especially in the hyperdiploid-ALL, involving additional SNPs in genes like TYMS, DHFR and GGH. We also investigated the statistical interactions and redundancies using structural model properties. These results gave further evidence that polymorphisms in the folate pathway could influence the ALL risk and the effectiveness of the therapy. It was also shown that in gene association studies the BN-BMLA could be a useful supplementary to the traditional frequentist-based statistical method.

Association of methylenetetrahydrofolate dehydrogenase 1 polymorphisms with cancer: a meta-analysis

Background

Studies investigating the association between single-nucleotide polymorphisms (SNPs) of the methylenetetrahydrofolate dehydrogenase 1 (MTHFD1) and cancer risk report conflicting results. To derive a more precise estimation of the relationship between MTHFD1 polymorphisms and cancer risk, the present meta-analysis was carried out.

Methodology/Principal Findings

A comprehensive search was conducted to determine all the eligible studies about MTHFD1 polymorphisms and cancer risk. Combined odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of the association between the MTHFD1 polymorphisms and cancer risk. We investigated by meta-analysis the effects of 2 polymorphisms in MTHFD1: G1958A (17 studies, 12348 cases, 44132 controls) and G401A (20 studies, 8446 cases, 14020 controls). The overall results indicated no major influence of these 2 polymorphisms on cancer risk. For G1958A, a decreased cancer risk was found in acute lymphoblastic leukemia (ALL)/Asians (the dominant: OR = 0.74, 95% CI = 0.58–0.94, P = 0.01; allelic: OR = 0.80, 95% CI = 0.65–0.99, P = 0.04) and other cancers (recessive: OR = 0.80, 95% CI = 0.66–0.96, P = 0.02). For G401A, the data showed that MTHFD1 G401A polymorphism was associated with a decreased colon cancer risk under dominant model (OR = 0.89, 95% CI = 0.80–0.99, P = 0.04).

Conclusions

The results suggest that MTHFD1 G1958A polymorphism might be associated with a decreased risk of ALL and other cancers. Meanwhile, the MTHFD1 G401A might play a protective role in the development of colon cancer. Large-scale and well-designed case-control studies are necessary to validate the risk identified in the present meta-analysis.

Polymorphisms in xenobiotic metabolizing genes (EPHX1, NQO1 and PON1) in lymphoma susceptibility: a case control study

Background

The interplay between genetic susceptibility and carcinogenic exposure is important in the development of haematopoietic malignancies. EPHX1, NQO1 and PON1 are three genes encoding proteins directly involved in the detoxification of potential carcinogens.

Methods

We have studied the prevalence of three functional polymorphisms affecting these genes rs1051740 EPHX1, rs1800566 NQO1 and rs662 PON1 in 215 patients with lymphoma and 214 healthy controls.

Results

Genotype frequencies for EPHX and NQO1 polymorphisms did not show any correlation with disease. In contrast, the GG genotype in the PON1 polymorphism was found to be strongly associated with the disease (15.3% vs. 4.7%; OR = 3.7 CI (95%): 1.8-7.7; p < 0.001). According to the pathological diagnosis this association was related to follicular (p = 0.004) and diffuse large B-cell (p = 0.016) lymphomas.

Conclusions

Despite the fact that further confirmation is needed, this study shows that the PON1 GG genotype in rs662 polymorphism could be a risk factor for B-cell lymphomas.

High order interactions of xenobiotic metabolizing genes and P53 codon 72 polymorphisms in acute leukemia

Polymorphisms in xenobiotic metabolizing genes are associated with altered metabolism of carcinogens in acute leukemia (AL). This study applied two data mining approaches to explore potential interactions among P53 and xenobiotic metabolizing genes in 230 AL patients [131 acute myeloid leukemia (AML) and 99 acute lymphoblastic leukemia (ALL)] and 199 controls. Individually, none of the genotypes showed significant associations with AML risk. However, in ALL the CYP1A12A TC genotype was associated with increased risk (OR = 2.02; 95% CI = 1.14-3.58; P = 0.01), whereas the GSTM1 null genotype imparted reduced risk (OR = 0.55; 95% CI = 0.31-0.96; P = 0.03). In classification and regression tree analysis, combinations of GSTM1 present, CYP1A12C AA or GG, EPHX1 exon3 TC, and EPHX1 exon4 AA or GG genotype strongly enhanced the risk of AML (OR = 5.89; 95% CI = 1.40-26.62; P = 0.01). In ALL, combinations of CYP1A12A TT, P53 GG or CC and GSTP1 AG genotypes conferred the highest risk (OR = 4.19; 95% CI = 1.45-12.25; P = 0.004). In multifactor dimensionality reduction analysis, a four locus model (GSTP1, P53, EPHX1 exon3, and CYP1A12A) was the best predictor model for ALL risk. The association between this model and ALL risk remained true even at low prior probabilities of 0.01% (false positive report probability = 0.05). Interaction entropy interpretations of the best model of ALL revealed that two-way interactions were mostly synergistic. These results suggest that high order gene-gene interactions play an important role in AL risk.

Methylenetetrahydrofolate reductase polymorphisms and risk of acute lymphoblastic leukemia-evidence from an updated meta-analysis including 35 studies

Background

5,10-methylenetetrahydrofolate reductase (MTHFR) variants, C677T and A1298C, have been reported to be associated with decreased risk of acute lymphoblastic leukemia (ALL). However, results derived from individually underpowered studies are conflicting. We carried out an updated meta-analysis on the association between MTHFR polymorphisms and ALL risk.

Methods

Relevant publications were searched through PUBMED and EMBASE databases. The associations between MTHFR C677T and A1298C polymorphisms and the risk of ALL were evaluated by odds ratios (ORs). The heterogeneity and publication bias were estimated. Meta-regression analysis was performed to evaluate the potential sources of heterogeneity.

Results

C677T polymorphism was associated with a reduced risk of ALL (allele contrast: OR_RE = 0.91, 95% CI: 0.83-0.99). Subgroup analysis showed MTHFR C677T variant was associated with decreased susceptibility to ALL in children and Caucasians. Meta-regression showed the logOR for the association between T allele and ALL increased as sex ratio (M/F) in the case group increased (P = 0.01). Regarding A1298C polymorphism, no significant association was observed (allele contrast: OR_RE = 1.01, 95% CI: 0.91-1.11). There was no publication bias for C677T or A1298C polymorphism.

Conclusions

The present meta-analysis suggests that the C677T polymorphism, not A1298C, in MTHFR gene is associated with a decreased risk of ALL, particularly among children and Caucasians subjects. Our findings suggest that the influence of the C677T polymorphism on ALL susceptibility is modified by sex ratio in cases (M/F). Since folate intake may be a possible confounding factor, including this factor in future prospective studies is warranted. Further meta-analysis studies should be at least stratified for folate levels and gender to give more powerful and informative results.

Folic acid supplementation, MTHFR and MTRR polymorphisms, and the risk of childhood leukemia: the ESCALE study (SFCE)

PURPOSE

Fetal folate deficiency may increase the risk of subsequent childhood acute leukemia (AL), since folates are required for DNA methylation, synthesis, and repair, but the literature remains scarce. This study tested the hypothesis that maternal folic acid supplementation before or during pregnancy reduces AL risk, accounting for the SNPs rs1801133 (C677T) and rs1801131 (A1298C) in MTHFR and rs1801394 (A66G) and rs1532268 (C524T) in MTRR, assumed to modify folate metabolism.

METHODS

The nationwide registry-based case-control study, ESCALE, carried out in 2003-2004, included 764 AL cases and 1,681 controls frequency matched with the cases on age and gender. Information on folic acid supplementation was obtained by standardized telephone interview. The genotypes were obtained using high-throughput platforms and imputation for untyped polymorphisms. Odds ratios (OR) were estimated using unconditional regression models adjusted for potential confounders.

RESULTS

AL was significantly inversely associated with maternal folic acid supplementation before and during pregnancy (OR = 0.4; 95 % confidence interval: [0.3-0.6]). MTHFR and MTRR genetic polymorphisms were not associated with AL. However, AL was positively associated with homozygosity for any of the MTHFR polymorphisms and carriership of both MTRR variant alleles (OR = 1.6 [0.9-3.1]). No interaction was observed between MTHFR, MTRR, and maternal folate supplementation.

CONCLUSION

The study findings support the hypothesis that maternal folic acid supplementation may reduce the risk of childhood AL. The findings also suggest that the genotype homozygous for any of the MTHFR variants and carrying both MTRR variants could be a risk factor for AL.

A meta-analysis of MTHFR C677T and A1298C polymorphisms and risk of acute lymphoblastic leukemia in children

BACKGROUND

Methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms have been implicated in childhood acute lymphoblastic leukemia (ALL) risk, but previously published studies were inconsistent and recent meta-analyses were not adequate.

PROCEDURES

In a meta-analysis of 21 publications with 4,706 cases and 7,414 controls, we used more stringent inclusion method and summarized data on associations between MTHFR C677T and A1298C polymorphisms and childhood ALL risk.

RESULTS

We found an overall association between 677T variant genotypes and reduced childhood ALL risk. Specifically, in the dominant genetic model, an association was found in a fixed-effect (TT + CT vs. CC: OR = 0.92; 95% CI = 0.85-0.99) but not random-effect model, whereas such an association was observed in both homozygote genetic model (TT vs. CC: OR = 0.80; 95% CI = 0.70-0.93 by fixed effects and OR = 0.78; 95% CI = 0.65-0.93 by random effects) and recessive genetic model (TT vs. CC + CT: OR = 0.83; 95% CI = 0.72-0.95 by fixed effects and OR = 0.84; 95% CI = 0.73-0.97 by random effects). These associations were also observed in subgroups by ethnicity: for Asians in all models except for the dominant genetic model by random effect and for Caucasians in all models except for the recessive genetic model. However, the A1298C polymorphism did not appear to have an effect on childhood ALL risk.

CONCLUSIONS

These results suggest that the MTHFR C677T, but not A1298C, polymorphism is a potential biomarker for childhood ALL risk.

The association between two polymorphisms in the TS gene and risk of cancer: a systematic review and pooled analysis

Thymidylate synthase (TS) is an important enzyme involved in folate metabolism and catalyzes methylation of deoxyuridine monophosphate to deoxythymidine monophosphate, which is essential for DNA replication. Thymidylate synthase enhancer region (TSER) and TS1494del6, two functionally important and ethnically diverse polymorphisms mapping to its gene region, are the most extensively studied. Considering the potential influence of altering TS activity, it is plausible that TS polymorphisms might play a role in the development of cancer. Although the effects of TS polymorphisms on susceptibility to human cancer have been investigated in many studies, the results remain conflicting rather than conclusive. To resolve these conflicts, we performed a quantitative synthesis of the evidence on the association between these two polymorphisms and cancer risk, including 63 studies (19,707 cases and 27,398 controls) for TSER polymorphism and 39 studies (13,489 cases and 16,297 controls) for TS1494del6 polymorphism. Our meta-analysis suggested that these two polymorphisms are not associated with cancer risk when all studies were pooled together. In the stratified analyses, we found that individuals with 2R/2R genotype had a significantly higher cancer risks among Asians (2R/2R vs. 3R/3R: odds ratio [OR] = 1.24, 95% confidence interval (95% CI) = 1.05-1.45; recessive model: OR = 1.23, 95% CI = 1.05-1.44). Further analyses revealed that 2R/2R genotype was significantly associated with an increased risk of gastroesophageal cancer among Asians, whereas it might provide protecting effects against colorectal cancer risk in a dominant genetic model for Caucasians. Additionally, TS1494del6 polymorphism may contribute to genetic susceptibility of breast cancer among Asians.

Thymidylate synthase polymorphisms and hematological cancer risk: a meta-analysis

Previous studies on the association of Thymidylate synthase (TYMS) polymorphisms with risk of hematological malignancies have produced conflicting results. The purpose of this meta-analysis was to define the effect of TYMS 5'-untranslated enhanced region (TSER) and 3'-untranslated region (TS3'-UTR) polymorphisms on the risk of hematological malignancies. Seventeen articles were identified as eligible in the case of TSER (2R > 3R) polymorphism (4511 cases and 6113 controls) and seven articles in the case of TS3'-UTR (1494del6) polymorphism (2721 cases and 3761 controls). The overall results suggested that either TSER or TS3'-UTR polymorphism was not associated with the risk of hematological malignancies. In stratified analyses, significantly decreased acute lymphoblastic leukemia (ALL) risk was found in adults (2R/3R vs. 2R/2R: odds ratio [OR] = 0.64, 95% confidence interval [CI]: 0.43-0.97), but increased ALL risk was observed in children (3R/3R vs. 2R/2R: OR = 1.46, 95% CI: 1.03-2.06). Increased non-Hodgkin lymphoma risk was found in the Caucasian population (2R/3R vs. 2R/2R: OR = 1.31, 95% CI: 1.10-1.56). Protective effects of the TS3'-UTR polymorphism (-6 bp/-6 bp) on hematological malignancies were found in a homozygote model and recessive model when the source of controls was stratified as hospital based. In conclusion, the TYMS TSER polymorphism may contribute to a susceptibility to risk of ALL in children and non-Hodgkin lymphoma in Caucasians, but protection from ALL risk in adults. The TS3'-UTR polymorphism (-6 bp/-6 bp) may have a protective effect in hematological malignancies.

Variants of the MTHFR gene and susceptibility to acute lymphoblastic leukemia in children: a synthesis of genetic association studies

BACKGROUND

Acute lymphoblastic leukemia (ALL) is a complex disease with genetic background. The genetic association studies (GAS) that investigated the association between ALL and the MTHFR C677T and A1298C gene variants have produced contradictory or inconclusive results.

MATERIALS AND METHODS

In order to decrease the uncertainty of estimated genetic risk effects, a meticulous meta-analysis of published GAS related the variants in the MTFHR gene with susceptibility to ALL was conducted. The risk effects were estimated based on the odds ratio (OR) of the allele contrast and the generalized odds ratio (OR(G)). Cumulative and recursive cumulative meta-analyses were also performed.

RESULTS

The analysis showed marginal significant association for the C677T variant, overall [OR=0.91 (0.82-1.00) and OR(G)=0.89 (0.79-1.01)], and in Whites [OR=0.88 (0.77-0.99) and OR(G)=0.85 (0.73-0.99)]. The A1298C variant produced non-significant results. For both variants, the cumulative meta-analysis did not show a trend of association as evidence accumulates and the recursive cumulative meta-analysis indicated lack of sufficient evidence for denying or claiming an association.

CONCLUSION

The current evidence is not sufficient to draw definite conclusions regarding the association of MTHFR variants and development of ALL.