A systematic review and meta-analysis of MTHFR polymorphisms in methotrexate toxicity prediction in pediatric acute lymphoblastic leukemia

Glutathione S-transferase gene polymorphisms and susceptibility to chronic myeloid leukemia

Glutathione S-transferase (GST), a phase II metabolizing enzyme, plays an important role in the cellar defense system, and its activity may modulate leukemia risk. A large body of evidence has shown the possible relevance of functional polymorphisms of the genes that encode GSTs μ, π, and θ (GSTM1, GSTP1, and GST1, respectively) to the genetic susceptibility of chronic myeloid leukemia (CML). Because of the lack of available conclusive data, we performed a meta-analysis of all relevant available studies to derive a more precise estimation of the relationship. A comprehensive literature search of PubMed and Web of Knowledge electronic databases was conducted to collect relevant studies until December 20, 2013, and the extracted data were statistically analyzed using Review Manager version 5.2. Finally, 16 eligible studies were identified in the literature. The GSTT1 null genotype was associated with an increased risk of CML, as were the double null GSTT1 and GSTM1 genotypes. These findings suggest that heritable GST status influences the risk of developing CML and that more attention should be paid to carriers of these susceptibility genes.

Methylenetetrahydrofolate reductase gene polymorphisms contribute to acute myeloid leukemia and chronic myeloid leukemia susceptibilities: evidence from meta-analyses

PURPOSE

The expression of methylenetetrahydrofolate reductase (MTHFR) is associated with acute myeloid leukemia (AML) and chronic myeloid leukemia (CML). Most studies have linked the common functional C677T and A1298C polymorphisms of the MTHFR gene and susceptibility to AML and CML, but the results were not consistent. The aim of the present study was to derive a more precise estimation of the relationship.

METHODS

Meta-analyses assessing the association of MTHFR C677T and A1298C variations with AML and CML were conducted. Eligible articles were identified from the PubMed and EMBASE databases. All statistical analyses were conducted using Review Manager Software.

RESULTS

10 and 10 studies were included in the meta-analysis about the role of C677T polymorphism on the AML and CML risks, respectively; 6 and 4 studies were included about the role of A1298C polymorphism on the AML and CML risks, respectively. Overall, both the C677T and A1298C polymorphisms were significantly associated with CML risk under the recessive model (P=0.04, OR=1.35, 95% CI=1.02-1.79 for C677T and P=0.003, OR=2.17, 95% CI=1.29-3.63 for A1298C). In addition, the risk of CML was higher in 1298CC genotype carriers than in 1298AA genotype carriers (P=0.004, OR=2.17, 95%=1.28-3.69). Conversely, the overall data failed to indicate a significant association of C677T or A1298C polymorphisms with AML risk under any model.

CONCLUSIONS

The findings provide evidence that C677T and A1298C polymorphisms are risk factors for CML risk.

Effect of polymorphisms within methotrexate pathway genes on methotrexate toxicity and plasma levels in adults with hematological malignancies

Aim: Pharmacogenetics of methotrexate (MTX) contributes to interindividual differences in toxicity. We aimed to evaluate the impact of SNPs within the MTX pathway genes on MTX-induced toxicity and MTX plasma levels at 48 h following treatment in Asian adults with acute lymphoblastic leukemia or non-Hodgkin lymphoma. Patients & methods: Patients (n = 71) were genotyped for MTHFR C677T, MTHFR A1298C, SLC19A1 G80A, ABCG2 C421A and ABCB1 C3435T using the Sequenom MassARRAY® platform. Plasma MTX concentrations at 48 h were measured by fluorescence polarization immunoassay. Results: Forty-eight patients had hematopoietic toxicity, 51 had hepatic toxicity and 36 had mucositis. Patients homozygous for MTHFR 677TT were associated with increased risk of both hematopoietic (odds ratio [OR]: 9.03; 95% CI: 2.28–36.16; p = 0.002) and hepatic (OR: 3.92; 95% CI: 1.01–15.11; p = 0.036) toxicities. Hepatic toxicity was associated with SLC19A1 G80A (OR: 5.27, 95% CI: 1.21–22.72; p = 0.032) and ABCB1 C3435T (OR: 8.62; 95% CI: 1.96–37.57; p = 0.004). However, polymorphisms in MTHFR A1298C and ABCG2 C421A were not associated with any of the toxicities, and mucositis was not associated with any polymorphisms of the MTX pathway genes. Patients with MTHFR C677T and ABCB1 C3435T polymorphisms appear to have significantly higher MTX plasma concentrations (p < 0.05). Conclusion: Our results in Asian adults provides evidence for the contribution pharmacogenetics to the toxicity of high-dose MTX and plasma MTX concentrations at 48 h following treatment in patients with acute lymphoblastic leukemia or non-Hodgkin lymphoma. These results will contribute towards the effort of MTX therapy individualization.

Original submitted 24 April 2014; Revision submitted 6 June 2014

Clinically relevant pharmacogenomic testing in pediatric practice

Clinicians and patients continue to convey interest in personalized medicine. The objective of personalized medicine is to improve healthcare by tailoring disease prevention, diagnosis, and treatment strategies for individuals based on their unique clinical history and genetic composition. This article offers an overview of pharmacogenomics, discusses caveats specific to pharmacogenomics in pediatric populations, provides evidence-based recommendations for pediatric clinicians, and offers insight regarding the future role of pharmacogenomics testing in pediatric medicine. Reviews of the current literature and thoughtful discussions are presented regarding the pharmacogenomics of antidepressants, codeine and oncologic, asthma, and immunomodulatory pharmacotherapies.

Pharmacogenetics of childhood acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the major pediatric cancer in developed countries. Although treatment outcome has improved owing to advances in chemotherapy, there is still a group of patients for which therapy fails while some patients experience severe toxicity. In the last few years, several pharmacogenetic studies have been performed to search for markers of outcome and toxicity in pediatric ALL. However, to date, TPMT is the only pharmacogenetic marker in ALL with clinical guidelines for drug dosing. In this article, we will provide an overview of the most important findings carried out in pharmacogenetics for pediatric ALL, such as the interest drawn by methotrexate transporters in the context of methotrexate treatment. Even if most of the studies are centered on coding genes, we will also point to new approaches focusing on noncoding regions and epigenetic variation that could be interesting for consideration in the near future.

Association between reduced folate carrier G80A polymorphism and methotrexate toxicity in childhood acute lymphoblastic leukemia: a meta-analysis

Abstract Methotrexate (MTX) is a key component of chemotherapeutic regimens for childhood acute lymphoblastic leukemia (ALL), and enters the cell via active transport mediated by the reduced folate carrier (RFC1). A major single-nucleotide polymorphism of the RFC1 gene, G80A, which affects the activity of RFC1, may influence MTX toxicity in pediatric ALL. We collected all studies that investigated the association of RFC1 G80A polymorphism and MTX toxicity in pediatric ALL, and found inconsistency among their results. The aim of this meta-analysis was to summarize all of these studies in order to clarify the correlation between the RFC1 G80A polymorphism and MTX toxicity in pediatric ALL. A recessive model demonstrated no influence of the RFC1 G80A genotype on MTX toxicity. In conclusion, the RFC1 G80A polymorphism does not seem to be a good marker of MTX-related toxicity in pediatric ALL.

Pharmacogenomics and pharmacoepigenomics in pediatric medicine

In the past several years, human genetics studies have progressed from monogenic to complex and common diseases because of the advancement in technologies. There is increased knowledge of the pharmacokinetics and pharmacogenomics of the drugs in adults as well as in children. These technological developments provided new diagnostic, prognostic, and therapeutic opportunities. We are now in a position to address many additional ambitious questions. For instance, in clinical medicine, interindividual variation in drug response is a major problem. Some of the heterogeneity of drug safety and efficacy among individuals can be explained by pharmacogenomics. It has also the potential to improve the treatment in both adults and children. In pediatrics however, there is ontogeny and metabolic capacity in children is different compared to adults. Several specific developmental changes may underlie some of the variability in drug response seen in children. They may also be responsible for adverse drug reactions (ADRs). Therefore, much of the diversity in drug effects cannot be explained by studying the genomic diversity alone. It is necessary to include the effect of growth (involves variations in gene expression) along with genetic differences when explaining the variability in treatment response. In this respect epigenomics may expand the scope of pharmacogenomics towards optimization of drug therapy. Future studies must focus on periods of maturation of the drug-metabolizing enzymes and polymorphisms in their genes by using candidate gene approach, gene expression analysis, genome-wide haplotype mapping, and proteomics. The integration of genetic data and clinical phenotypes along with the role of other factors is necessary to evaluate both efficacy and ADRs of any drug. It may require extensive genetic epidemiological studies spanning over many years.