Impact of genetic polymorphisms on chemotherapy toxicity in childhood acute lymphoblastic leukemia

Pharmacogenetics of pediatric acute lymphoblastic leukemia in Uruguay: adverse events related to induction phase drugs

In Uruguay, the pediatric acute lymphoblastic leukemia (ALL) cure rate is 82.2%, similar to those reported in developed countries. However, many patients suffer adverse effects that could be attributed, in part, to genetic variability. This study aims to identify genetic variants related to drugs administered during the induction phase and analyze their contribution to adverse effects, considering individual genetic ancestry. Ten polymorphisms in five genes (ABCB1, CYP3A5, CEP72, ASNS, and GRIA1) related to prednisone, vincristine, and L-asparaginase were genotyped in 200 patients. Ancestry was determined using 45 ancestry informative markers (AIMs). The sample ancestry was 69.2% European, 20.1% Native American, and 10.7% African, but with high heterogeneity. Mucositis, Cushing syndrome, and neurotoxicity were the only adverse effects linked with genetic variants and ancestry. Mucositis was significantly associated with ASNS (rs3832526; 3R/3R vs. 2R carriers; OR: = 6.88 [1.88-25.14], p = 0.004) and CYP3A5 (non-expressors vs. expressors; OR: 4.55 [1.01-20.15], p = 0.049) genes. Regarding Cushing syndrome, patients with the TA genotype (rs1049674, ASNS) had a higher risk of developing Cushing syndrome than those with the TT genotype (OR: 2.60 [1.23-5.51], p = 0.012). Neurotoxicity was significantly associated with ABCB1 (rs9282564; TC vs. TT; OR: 4.25 [1.47-12.29], p = 0.007). Moreover, patients with <20% Native American ancestry had a lower risk of developing neurotoxicity than those with ≥20% (OR: 0.312 [0.120-0.812], p = 0.017). This study shows the importance of knowing individual genetics to improve the efficacy and safety of acute lymphoblastic leukemia.

Mucin (MUC) Family Influence on Acute Lymphoblastic Leukemia in Cancer and Non-Cancer Native American Populations from the Brazilian Amazon

The mucin (MUC) family includes several genes aberrantly expressed in multiple carcinomas and mediates diverse pathways essentials for oncogenesis, in both solid and hematological malignancies. Acute Lymphoblastic Leukemia (ALL) can have its course influenced by genetic variants, and it seems more frequent in the Amerindian population, which has been understudied. Therefore, the present work aimed to investigate the MUC family exome in Amerindian individuals from the Brazilian Amazon, in a sample containing healthy Native Americans (NAMs) and indigenous subjects with ALL, comparing the frequency of polymorphisms between these two groups. The population was composed of 64 Amerindians from the Brazilian Amazon, from 12 different isolated tribes, five of whom were diagnosed with ALL. We analyzed 16 genes from the MUC family and found a total of 1858 variants. We compared the frequency of each variant in the ALL vs. NAM group, which led to 77 variants with a significant difference and, among these, we excluded those with a low impact, resulting in 63 variants, which were distributed in nine genes, concentrated especially in MUC 19 (n = 30) and MUC 3A (n = 18). Finally, 11 new variants were found in the NAM population. This is the first work with a sample of native Americans with cancer, a population which is susceptible to ALL, but remains understudied. The MUC family seems to have an influence on the development of ALL in the Amerindian population and especially MUC19 and MUC3A are shown as possible hotspots. In addition, the 11 new variants found point to the need to have their clinical impact analyzed.

Insights into Asparaginase from Endophytic Fungus Lasiodiplodia theobromae: Purification, Characterization and Antileukemic Activity

Endobiotic fungi are considered as a reservoir of numerous active metabolites. Asparaginase is used as an antileukemic drug specially to treat acute lymphoblastic leukaemia. The presented study aims to optimize the media conditions, purify, characterize, and test the antileukemic activity of the asparaginase induced from Lasiodiplodia theobromae. The culture medium was optimized using an experiment designed by The Taguchi model with an activity ranging from 10 to 175 IU/mL. Asparaginase was induced with an activity of 315 IU/mL. Asparaginase was purified with a specific activity of 468.03 U/mg and total activity of 84.4 IU/mL. The purified asparaginase showed an approximate size of 70 kDa. The purified asparaginase showed an optimum temperature of 37 °C and an optimum pH of 6. SDS reduced the activity of asparaginase to 0.65 U/mL while the used ionic surfactants enhanced the enzyme activity up to 151.92 IU/mL. The purified asparaginase showed a K_m of 9.37 µM and V_max of 127.00 µM/mL/min. The purified asparaginase showed an IC₅₀ of 35.2 ± 0.7 IU/mL with leukemic M-NFS-60 cell lines and CC₅₀ of 79.4 ± 1.9 IU/mL with the normal WI-38 cell line. The presented study suggests the use of endophytic fungi as a sustainable source for metabolites such as asparaginase, provides an opportunity to develop a facile, eco-friendly, cost-effective, and rapid synthesis of antileukemic drugs, which have the potential to be used as alternative and reliable sources for potent anticancer agents.

Population Pharmacokinetics of High-Dose Methotrexate in Chinese Pediatric Patients With Acute Lymphoblastic Leukemia

High-dose methotrexate (HD-MTX) is widely used in pediatric acute lymphoblastic leukemia (ALL) treatment regimens. In this study, we aimed to develop a population pharmacokinetic (PK) model of HD-MTX in Chinese pediatric patients with ALL for designing personalized dosage regimens. In total, 4,517 MTX serum concentration data for 311 pediatric patients with ALL, aged 0.75–15.2 years and under HD-MTX treatment, were retrospectively collected at a tertiary Children’s Hospital in China. The non-linear mixed-effect model was used to establish the population PK model, using NONMEM software. The potential covariate effects of age, body weight, and biochemical measurements (renal and liver function) on MTX PK disposition were investigated. The model was then evaluated using goodness-of-fit, visual predictive check. MTX PK disposition was described using a three-compartment model reasonable well. Body weight, implemented as a fixed allometric function on all clearance and volume of distribution parameters, showed a substantial improvement in model fit. The final population model demonstrated that the MTX clearance estimate in a typical child with body weight of 19 kg was 6.9 L/h and the central distribution of volume estimate was 20.7 L. The serum creatinine significantly affected the MTX clearance, with a 0.97% decrease in clearance per 1 μmol/L of serum creatinine. Other covariates (e.g., age, sex, bilirubin, albumin, aspartate transaminase, concomitant medication) did not significantly affect PK properties of MTX. The proposed population PK model could describe the MTX concentration data in Chinese pediatric patients with ALL. This population PK model combined with a maximum a posteriori Bayesian approach could be used to estimate individual PK parameters, and optimize personalized MTX therapy in target patients, thus aiming to reduce toxicity and improve treatment outcomes.

Influence of genetic variants in asparaginase pathway on the susceptibility to asparaginase-related toxicity and patients' outcome in childhood acute lymphoblastic leukemia

BACKGROUND

Asparaginase (ASNase) is a key component in the treatment protocols of childhood acute lymphoblastic leukemia (ALL). Asparagine synthetase (ASNS) and the basic region leucine zipper activating transcription factor 5 (ATF5) mediate the anti-leukemic effect of ASNase. Only a few reports studied the association between polymorphisms in these genes and treatment-related toxicity and response. Therefore, the current study aimed to investigate the association of ASNS and ATF5 polymorphisms with the susceptibility to ASNase-related toxicity and disease outcome in a population of childhood ALL Egyptian patients.

METHODS

In this study, 88 children with ALL were enrolled and genotyped for ASNS T629A and ATF5 C362T polymorphisms using allelic discrimination assay.

RESULTS

The studied polymorphisms did not associate with hypersensitivity or thrombosis, while the ATF5 C362T polymorphism was associated significantly with decreased ASNase-associated pancreatitis (AAP) risk under the dominant model. Patients carrying TT/CT genotypes of ATF5 C362T polymorphism had a significantly better overall survival (OS) and longer event-free survival (EFS) compared to patients with CC genotype. Multivariate analysis confirmed the independent prognostic value of the ATF5 C362T dominant model.

CONCLUSION

ATF5 362TT and CT genotypes were associated with decreased risk to develop AAP and better disease outcome demonstrating a low risk for events and superior survival.

Genetic Analysis of Pharmacogenomic VIP Variants of ABCB1, VDR and TPMT Genes in an Ethnically Isolated Population from the North Caucasus Living in Jordan

Background:

Differences in individual responses to the same medications remarkably differ among populations. A number of genes that play integral roles in drug responses have been designated as very important pharmacogenes (VIP), as they are responsible for differences in drug safety, efficacy, and adverse drug reactions among certain ethnic groups. Identifying the polymorphic distribution of VIP in a range of ethnic groups will be conducive to population-based personalized medicine.

Objective:

The aim of the current study is to identify the polymorphic distribution of VIP regarding the Chechen minority group from Jordan and compare their allele frequencies with other populations.

Methods:

A total of 131 unrelated Chechen individuals from Jordan were randomly recruited for blood collection. Identification of allelic and genotypic frequencies of eleven VIP variants within the genes of interest (ABCB1, VDR and TPMT) was carried out by means of the MassARRAY®System (iPLEX GOLD).

Results:

Within ABCB1, we found that the minor allele frequencies of the rs1128503 (A: 0.43), rs2032582 (A: 0.43), rs1045642 (A: 0.43). For VDR, the minor allele frequencies of rs11568820 (T: 0.18), rs1540339 (T: 0.30), rs1544410 (T: 0.41), rs2228570 (T: 0.24), rs3782905 (C: 0.28) and rs7975232 (C: 0.45). Finally, the minor allele frequencies for the TPMT rs1142345 and rs1800460 polymorphisms were found to be (C: 0.02) and (T: 0.01), respectively.

Conclusion:

Significant differences in allelic frequencies of eleven ABCB1, VDR and TPMT VIP variants were found between Jordanian Chechens and other populations. In our study, most populations that are similar to Chechens are those from South Asian, European (Finnish) and European, including: Utah residents with Northern and Western European ancestry, Toscani in Italia, Mexican ancestry in Los Angeles and Circassian from Jordan. The level of similarity between Chechens and those populations means that they might have shared high levels of gene flow in the past. The results obtained in this study will contribute to the worldwide pharmacogenomic databases and provide valuable information for future studies and better individualized treatments.

Genetic markers for treatment-related pancreatitis in a cohort of Hispanic children with acute lymphoblastic leukemia

PURPOSE

Treatment-related pancreatitis (TRP) is a serious complication occurring in children with acute lymphoblastic leukemia (ALL). Those affected are at high risk for severe organ toxicity and treatment delays that can impact outcomes. TRP is associated with asparaginase, a standard therapeutic agent in childhood ALL. Native American ancestry, older age, high-risk leukemia, and increased use of asparaginase are linked to pancreatitis risk. However, dedicated genetic studies evaluating pancreatitis in childhood ALL include few Hispanics. Thus, the genetic basis for higher risk of pancreatitis among Hispanic children with ALL remains unknown.

METHODS

Cases of children with ALL treated in from 1994 through 2013 were reviewed and identified 14, all Hispanic, who developed pancreatitis related to asparaginase therapy. Forty-six controls consisting of Hispanic children treated on the same regimens without pancreatitis were selected for comparison. Total DNA isolated from whole blood was used for targeted DNA sequencing of 23 selected genes, including genes associated with pancreatitis without ALL and genes involved in asparagine metabolism.

RESULTS

Non-synonymous polymorphisms and frameshift deletions were detected in 15 genes. Most children with TRP had variants in ABAT, ASNS, and CFTR. Notably, children with TRP harbored many more CFTR variants (71.4%) compared with controls (39.1%). Among these, V470M (rs213950) was most frequent (OR 4.27, p = 0.025).

CONCLUSIONS

This is the first study of genetic factors in treatment-related pancreatitis in Hispanic children with ALL. Identifying correlative variants in ethnically vulnerable populations may improve screening to identify which patients with ALL are at greatest risk for pancreatitis.

Pharmacogenomic and Pharmacotranscriptomic Profiling of Childhood Acute Lymphoblastic Leukemia: Paving the Way to Personalized Treatment

Personalized medicine is focused on research disciplines which contribute to the individualization of therapy, like pharmacogenomics and pharmacotranscriptomics. Acute lymphoblastic leukemia (ALL) is the most common malignancy of childhood. It is one of the pediatric malignancies with the highest cure rate, but still a lethal outcome due to therapy accounts for 1%⁻3% of deaths. Further improvement of treatment protocols is needed through the implementation of pharmacogenomics and pharmacotranscriptomics. Emerging high-throughput technologies, including microarrays and next-generation sequencing, have provided an enormous amount of molecular data with the potential to be implemented in childhood ALL treatment protocols. In the current review, we summarized the contribution of these novel technologies to the pharmacogenomics and pharmacotranscriptomics of childhood ALL. We have presented data on molecular markers responsible for the efficacy, side effects, and toxicity of the drugs commonly used for childhood ALL treatment, i.e., glucocorticoids, vincristine, asparaginase, anthracyclines, thiopurines, and methotrexate. Big data was generated using high-throughput technologies, but their implementation in clinical practice is poor. Research efforts should be focused on data analysis and designing prediction models using machine learning algorithms. Bioinformatics tools and the implementation of artificial i Lack of association of the CEP72 rs924607 TT genotype with intelligence are expected to open the door wide for personalized medicine in the clinical practice of childhood ALL.

Inhibition of NAMPT sensitizes MOLT4 leukemia cells for etoposide treatment through the SIRT2-p53 pathway

NAMPT (Nicotinamide phosphoribosyltransferase) catalyses the rate-limiting step in the NAD biosynthesis from nicotinamide and thereby regulates the activity of NAD-dependent enzymes. Cancer cells are highly dependent on NAD for energy and DNA repair processes and are assumed to be more susceptible to an inhibition of NAD synthesis than non-transformed cells. We aimed to investigate whether or not inhibition of NAMPT with its specific inhibitor FK866 can sensitize leukemia cells for chemotherapeutic agents. NAMPT protein abundance, enzymatic activity and NAD concentrations were significantly higher in Jurkat and Molt-4 leukemia cell lines compared to normal peripheral blood mononuclear cells. Combination of etoposide and FK866 caused increased cell death in leukemia cell lines compared to etoposide alone. Etoposide decreased protein abundance of NAD-dependent deacetylases SIRTUIN1. After combining etoposide and FK866 treatment SIRTUIN2 was further decreased and accumulation and acetylation of the downstream target p53 was further enhanced in MOLT4 cells. Concomitantly, protein abundance of p21 and cleaved BAX was increased. Targeting NAMPT could be a novel therapeutic strategy to enhance the efficacy of chemotherapeutic agents such as etoposide against leukemia.

Dihydrofolate Reductase Genetic Polymorphisms Affect Methotrexate Dose Requirements in Pediatric Patients With Acute Lymphoblastic Leukemia on Maintenance Therapy

We have aimed to determine the effect of polymorphisms in regulatory regions of the DHFR gene in relation to methotrexate (MTX) dose adjustments and drug-induced toxicity in children on maintenance therapy for acute lymphoblastic leukemia (ALL). In total, 41 children diagnosed with ALL were screened for 3 tag-single nucleotide polymorphisms in the DHFR promoter (C-1610G, C-680G/T, A-317G) and an intronic 19-bp insertion/deletion. Genotypes were analyzed in relation to dose requirements and toxicity. The percentage of MTX dose administered (with respect to protocol-recommended values) was affected by DHFR polymorphisms. Carriers of the -680AA genotype displayed a median percentage of 44.08 (interquartile range=34.69), compared with 77.98 (interquartile range=33.90) for CC and CA carriers (P=0.01). The number of counts within white blood cell therapeutic range (2.0 to 3.0×10/L) was higher for -680AA carriers than for CC/CA carriers (P=0.003). With regard to toxicity, carriers of the -680AA genotype displayed more treatment interruptions than CC/CG carriers (P=0.03), as well as more episodes of severe neutropenia (P=0.04) and higher number of blood counts with elevated levels (>400 mg/dL) of lactate dehidrogenase (P=0.04). Overall, our findings suggest that the identification of DHFR polymorphisms in the promoter region of the gene may be helpful in tailoring MTX doses for ALL pediatric patients on maintenance therapy.

Pharmacogenomics in pediatric acute lymphoblastic leukemia: promises and limitations

Despite the significant advances achieved in pediatric acute lymphocytic leukemia (ALL) treatment, adverse side effects of drugs remain a challenging issue. Numerous ALL pharmacogenomic studies have been conducted to elucidate the predisposing genetic factors for their development. Plausible pharmacogenomic data are available for the osteonecrosis associated with glucocorticoids, the neurotoxicity associated with vincristine and the cardiotoxicity related to anthracyclines. However, these data have not been fully translated into the clinic due to several limitations, most importantly the lack of reliable evidence. The most robust pharmacogenomics data are those for thiopurines and methotrexate use, with evidence-based preemptive testing recommendations for the former. Pharmacogenomics has a significant potential utility in pediatric ALL treatment regimens. In this review, gaps and limitations in this field are emphasized, which may provide a useful guide for future research design.

Association Between Combined Presence of Hepatitis C Virus and Polymorphisms in Different Genes With Toxicities of Methotrexate and 6-Mercaptopurine in Children With Acute Lymphoblastic Leukemia

BACKGROUND

The aim of the present study is to determine the correlation of hepatitis C virus (HCV) infection and polymorphisms in different genes with toxicity of either methotrexate (MTX) or 6-mercaptopurine (6-MP) administered to children with acute lymphoblastic leukemia (ALL).

PROCEDURE

One hundred children with low-risk ALL, who were treated according to the St. Jude Total therapy XV, were recruited. The recruited children were receiving MTX and 6-MP during maintenance phase. Patients were excluded from the study if they had other types of leukemia. Genotyping analyses for the thiopurine methyltransferase (TPMT), methylenetetrahydrofolate reductase (MTHFR), and glutathione S-transferase (GST) genes were performed using a combination of polymerase chain reaction (PCR) and PCR-RFLP (where RFLP is restriction fragment length polymorphism) protocols. Relevant clinical data on adverse drug reactions were collected objectively (blinded to genotypes) from the patient medical records.

RESULTS

There was a significant correlation between the combined presence of HCV and TPMT*3B G460A gene polymorphisms and grades 2-4 hepatotoxicity as aspartate aminotransferase (AST) elevation (P < 0.04). The same observation was seen when comparing either the presence of HCV alone or the presence of the gene polymorphism alone. A significant association between the combined presence of HCV and MTHFR C677T polymorphism and grades 2-4 hepatotoxicity as alanine aminotransferase (ALT), AST, and alkaline phosphatase (ALP) elevation was observed (P values <0.001, 0.02, and 0.001, respectively). The presence of HCV infection had a significant negative effect on hepatic transaminases.

CONCLUSIONS

The present data support a role for combining analysis of genetic variation in drug-metabolizing enzymes and the presence of HCV in the assessment of specific drugs toxicities in multiagent chemotherapeutic treatment regimens.

A single day of 5-azacytidine exposure during development induces neurodegeneration in neonatal mice and neurobehavioral deficits in adult mice

The present study was undertaken to evaluate the immediate and long-term effects of a single-day exposure to 5-Azacytidine (5-AzaC), a DNA methyltransferase inhibitor, on neurobehavioral abnormalities in mice. Our findings suggest that the 5-AzaC treatment significantly inhibited DNA methylation, impaired extracellular signal-regulated kinase (ERK1/2) activation and reduced expression of the activity-regulated cytoskeleton-associated protein (Arc). These events lead to the activation of caspase-3 (a marker for neurodegeneration) in several brain regions, including the hippocampus and cortex, two brain areas that are essential for memory formation and memory storage, respectively. 5-AzaC treatment of P7 mice induced significant deficits in spatial memory, social recognition, and object memory in adult mice and deficits in long-term potentiation (LTP) in adult hippocampal slices. Together, these data demonstrate that the inhibition of DNA methylation by 5-AzaC treatment in P7 mice causes neurodegeneration and impairs ERK1/2 activation and Arc protein expression in neonatal mice and induces behavioral abnormalities in adult mice. DNA methylation-mediated mechanisms appear to be necessary for the proper maturation of synaptic circuits during development, and disruption of this process by 5-AzaC could lead to abnormal cognitive function.

Pharmacogenetics and induction/consolidation therapy toxicities in acute lymphoblastic leukemia patients treated with AIEOP-BFM ALL 2000 protocol

Drug-related toxicities represent an important clinical concern in chemotherapy, genetic variants could help tailoring treatment to patient. A pharmacogenetic multicentric study was performed on 508 pediatric acute lymphoblastic leukemia patients treated with AIEOP-BFM 2000 protocol: 28 variants were genotyped by VeraCode and Taqman technologies, deletions of GST-M1 and GST-T1 by multiplex PCR. Toxicities were derived from a central database: 251 patients (49.4%) experienced at least one gastrointestinal (GI) or hepatic (HEP) or neurological (NEU) grade III/IV episode during the remission induction phase: GI occurred in 63 patients (12.4%); HEP in 204 (40.2%) and NEU in 44 (8.7%). Logistic regression model adjusted for sex, risk and treatment phase revealed that ITPA rs1127354 homozygous mutated patients showed an increased risk of severe GI and NEU. ABCC1 rs246240 and ADORA2A rs2236624 homozygous mutated genotypes were associated to NEU and HEP, respectively. These three variants could be putative predictive markers for chemotherapy-related toxicities in AIEOP-BFM protocols.

Impact of single nucleotide polymorphisms of cytarabine metabolic genes on drug toxicity in childhood acute lymphoblastic leukemia

BACKGROUND

Cytarabine (cytosine arabinoside, ara-C) is a chemotherapeutical agent used in the treatment of pediatric acute lymphoblastic leukemia (ALL). Adverse drug reactions, such as interpatient variability in sensitivity to ara-C, are considerable and may cause difficulties during chemotherapy. Single nucleotide polymorphisms (SNPs) can play a significant role in modifying nucleoside-drug pharmacokinetics and pharmacodynamics and thus the development of adverse effects. Our aim was to determine whether polymorphisms in genes encoding transporters and enzymes responsible for the metabolism of ara-C are associated with toxicity and clinical outcome in a patient population with childhood ALL.

PROCEDURE

We studied 8 SNPs in the CDA, DCK, DCTD, SLC28A3, and SLC29A1 genes in 144 patients with childhood acute lymphoblastic leukemia treated according to ALLIC BFM 1990, 1995 and 2002 protocols.

RESULTS

DCK rs12648166 and DCK rs4694362 SNPs were associated with hematologic toxicity (OR = 2.63, CI 95% = 1.37-5.04, P = 0.0036 and OR = 2.53, CI 95% = 1.34-4.80, P = 0.0044, respectively).

CONCLUSIONS

Our results indicate that DCK polymorphisms might be important genetic risk factors for hematologic toxicity during ALL treatment with ara-C. Individualized chemotherapy based on genetic profiling may help to optimize ara-C dosing, leading to improvements in clinical outcome and reduced toxicity.

An analysis of the therapeutic benefits of genotyping in pediatric hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation is a high-risk procedure that is offered, with curative intent, to patients with malignant and nonmalignant disease. The clinical benefits of personalization of therapy by genotyping have been demonstrated by the reduction in transplant related mortality from donor-recipient HLA matching. However, defining the relationship between genotype and transplant conditioning agents is yet to be translated into clinical practice. A number of the therapeutic agents used in stem cell transplant preparative regimens have pharmacokinetic parameters that predict benefit of incorporating pharmacogenomic data into dosing strategies. Busulfan, cyclophosphamide, thio-TEPA and etoposide have well-described drug metabolism pathways, however candidate gene studies have identified there is a gap in the identification of pharmacogenomic data that can be used to improve transplant outcomes. Incorporating pharmacogenomics into pharmacokinetic modeling may demonstrate the therapeutic benefits of genotyping in transplant preparative regimen agents.

Pharmacogenetics predictive of response and toxicity in acute lymphoblastic leukemia therapy

Acute lymphoblastic leukemia (ALL) is a relatively rare disease in adults accounting for no more than 20% of all cases of acute leukemia. By contrast with the pediatric population, in whom significant improvements in long term survival and even cure have been achieved over the last 30years, adult ALL remains a significant challenge. Overall survival in this group remains a relatively poor 20-40%. Modern research has focused on improved pharmacokinetics, novel pharmacogenetics and personalized principles to optimize the efficacy of the treatment while reducing toxicity. Here we review the pharmacogenetics of medications used in the management of patients with ALL, including l-asparaginase, glucocorticoids, 6-mercaptopurine, methotrexate, vincristine and tyrosine kinase inhibitors. Incorporating recent pharmacogenetic data, mainly from pediatric ALL, will provide novel perspective of predicting response and toxicity in both pediatric and adult ALL therapies.

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