Host genetic variants of ABCB1 and IL15 influence treatment outcome in paediatric acute lymphoblastic leukaemia

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.

The role of interleukin-15 in the development and treatment of hematological malignancies

Cytokines are a vital component of the immune system that controls the activation and growth of blood cells. However, chronic overexpression of cytokines can trigger cellular events leading to malignant transformation. The cytokine interleukin-15 (IL-15) is of particular interest, which has been shown to contribute to the development and progression of various hematological malignancies. This review will provide an overview of the impact of the immunopathogenic function of IL-15 by studying its role in cell survival, proliferation, inflammation, and treatment resistance. We will also review therapeutic approaches for inhibiting IL-15 in blood cancers.

Association of GATA3 Polymorphisms With Minimal Residual Disease and Relapse Risk in Childhood Acute Lymphoblastic Leukemia

BACKGROUND

Minimal residual disease (MRD) after induction therapy is one of the strongest prognostic factors in childhood acute lymphoblastic leukemia (ALL), and MRD-directed treatment intensification improves survival. Little is known about the effects of inherited genetic variants on interpatient variability in MRD.

METHODS

A genome-wide association study was performed on 2597 children on the Children's Oncology Group AALL0232 trial for high-risk B-cell ALL. Association between genotype and end-of-induction MRD levels was evaluated for 863 370 single nucleotide polymorphisms (SNPs), adjusting for genetic ancestry and treatment strata. Top variants were further evaluated in a validation cohort of 491 patients from the Children's Oncology Group P9905 and 6 ALL trials. The independent prognostic value of single nucleotide polymorphisms was determined in multivariable analyses. All statistical tests were 2-sided.

RESULTS

In the discovery genome-wide association study, we identified a genome-wide significant association at the GATA3 locus (rs3824662, odds ratio [OR] = 1.58, 95% confidence interval [CI] = 1.35 to 1.84; P = 1.15 × 10-8 as a dichotomous variable). This association was replicated in the validation cohort (P = .003, MRD as a dichotomous variable). The rs3824662 risk allele independently predicted ALL relapse after adjusting for age, white blood cell count, and leukemia DNA index (P = .04 and .007 in the discovery and validation cohort, respectively) and remained prognostic when the analyses were restricted to MRD-negative patients (P = .04 and .03 for the discovery and validation cohorts, respectively).

CONCLUSION

Inherited GATA3 variant rs3824662 strongly influences ALL response to remission induction therapy and is associated with relapse. This work highlights the potential utility of germline variants in upfront risk stratification in ALL.

ABCB1, ABCG2, ABCC1, ABCC2, and ABCC3 drug transporter polymorphisms and their impact on drug bioavailability: what is our current understanding?

INTRODUCTION

Interindividual differences in drug response are a frequent clinical challenge partly due to variation in pharmacokinetics. ATP-binding cassette (ABC) transporters are crucial determinants of drug disposition. They are subject of gene regulation and drug-interaction; however, it is still under debate to which extend genetic variants in these transporters contribute to interindividual variability of a wide range of drugs.

AREAS COVERED

This review discusses the current literature on the impact of genetic variants in ABCB1, ABCG2 as well as ABCC1, ABCC2, and ABCC3 on pharmacokinetics and drug response. The aim was to evaluate if results from recent studies would increase the evidence for potential clinically relevant pharmacogenetic effects.

EXPERT OPINION

Although enormous efforts have been made to investigate effects of ABC transporter genotypes on drug pharmacokinetics and response, the majority of studies showed only weak if any associations. Despite few unique results, studies mostly failed to confirm earlier findings or still remained inconsistent. The impact of genetic variants on drug bioavailability is only minor and other factors regulating the transporter expression and function seem to be more critical. In our opinion, the findings on the so far investigated genetic variants in ABC efflux transporters are not suitable as predictive biomarkers.

Intracellular vincristine levels in lymphoblasts affect treatment outcome in childhood B-lymphoblastic leukaemia: Ma-Spore ALL 2010 study

AIMS

Vincristine (VCR) is a key drug in the successful multidrug chemotherapy for childhood acute lymphoblastic leukaemia (ALL). However, it remains unclear how VCR pharmacokinetics affects its antileukaemic efficacy. The objective of this study is to explore the VCR pharmacokinetic parameters and intracellular VCR levels in an up-front window of Ma-Spore ALL 2010 (MS2010) study.

METHODS

We randomised 429 children with newly diagnosed ALL to 15-minute vs 3-hour infusion for the first dose of VCR to study if prolonging the first dose of VCR infusion improved response. In a subgroup of 115 B-ALL and 20 T-ALL patients, we performed VCR plasma (n = 135 patients) and intracellular (n = 66 patients) pharmacokinetic studies. The correlations between pharmacokinetic parameters and intracellular VCR levels with early treatment response, final outcome and ABCB1 genotypes were analysed.

RESULTS

There was no significant difference between 15-minute and 3-hour infusion schedules in median Day 8 peripheral or bone marrow blast response. Plasma VCR pharmacokinetic parameters did not predict outcome. However, in B-ALL, Day 33 minimal residual disease (MRD) negative patients and patients in continuous complete remission had significantly higher median intracellular VCR_24h levels (P = .03 and P = .04, respectively). The median VCR_24h intracellular levels were similar among the common genetic subtypes of ALL (P = .4). Patients homozygous for wild-type ABCB1 2677GG had significantly higher median intracellular VCR_24h (P = .04) than 2677TT.

CONCLUSION

We showed that in childhood B-ALL, the intracellular VCR_24h levels in lymphoblasts affected treatment outcomes. The intracellular VCR_24h level was independent of leukaemia subtype but dependent on host ABCB1 G2677T genotype.

ABCB1 Polymorphisms and Cold Pressor Pain Responses: Opioid-Dependent Patients on Methadone Maintenance Therapy

BACKGROUND

Methadone is a substrate of the P-glycoprotein efflux transporter, which is encoded by ABCB1 (MDR1), and thus, ABCB1 polymorphisms may influence the transport of methadone at the blood-brain barrier, affecting its adverse effects.

OBJECTIVES

This study investigated the association between ABCB1 polymorphisms and cold pressor pain responses among opioid-dependent patients on methadone maintenance therapy (MMT).

METHODS

Malay male opioid-dependent patients receiving MMT (n = 148) were recruited. Cold pressor pain responses (pain threshold, pain tolerance, and pain intensity) were measured at 0, 2, 4, 8, 12, and 24 hours post-methadone dose. DNA was extracted from whole blood and genotyped for ABCB1 polymorphisms including 1236C>T (rs1128503), 2677G>T/A (rs2032582), and 3435C>T (rs1045642) using the allelic discrimination real-time polymerase chain reaction. Repeated-measure analysis of variance between-group analysis was used to compare the three cold pressor pain responses and ABCB1 polymorphisms (1236C>T, 2677G>T/A, and 3435C>T) according to genotypes and allelic additive models, genotype dominant and recessive models, haplotypes, and diplotypes.

RESULTS

Patients with 2677 GG or 2677G allele had the lowest pain threshold compared with 2677G>T/A genotypes or alleles (p = .007 and .002, respectively). Haplotype analysis showed a significant association between ABCB1 haplotypes and pain threshold (p = .02). Patients with 2677G allele had the lowest pain tolerance compared to those with 2677T and 2677A alleles (2677G < 2677T < 2677A allele carriers; p = .05). In terms of pain intensity scores, patients with 2677 GG or 2677G allele had the highest scores compared to other 2677G>T/A genotypes or alleles (p = .04 and .008, respectively). Haplotype analysis revealed a significant difference between patients with CGC haplotype and those without this haplotype (p = .02).

DISCUSSION

To the best of our knowledge, this study provides the first evidence that ABCB1 polymorphisms are associated with cold pressor pain responses among Malay male patients with opioid dependence on MMT. The results may provide an initial prediction on heightened pain sensitivity or hyperalgesia for individuals who are carriers of the ABCB1 polymorphisms.

Clinical significance of the ABCB1 and ABCG2 gene expression levels in acute lymphoblastic leukemia

OBJECTIVES

Acute lymphoblastic leukemia (ALL) is a clonal disease that accounts for 20% of acute leukemias in adults. A high percentage of adult patients (ranging from 70 to 80%) reach complete remission; however, the 5-year survival rate is only 20-40%. One of the main obstacles to treatment success is the drug resistance of leukemic cells. Therefore, our research group analyzed the ABCB1 and ABCG2 gene expression levels in 61 patients diagnosed with ALL and assessed whether the levels affected the clinical parameters and 40-month survival rate.

METHODS

The ABCB1 and ABCG2 gene expression levels were analyzed using real-time polymerase chain reaction in 61 patients diagnosed with ALL and 99 healthy donors as controls. The association between ABCB1 and ABCG2 gene expression levels and clinical variables was determined using the Chi-square test and Fisher's exact test. Overall survival (OS) was determined using the Kaplan-Meier method.

RESULTS

The results showed high ABCB1 and ABCG2 gene levels, which were 4.5 and 2.3 times the levels of healthy donors, respectively. A total of 52% of the study patients expressed high ABCB1 levels and were significantly associated with the high-risk patient group and a decreased 40-month survival rate of 78%. Only 49% of the patients expressed high ABCG2 gene levels. No association was found between the clinical parameters and the ABCG2 gene expression levels.

CONCLUSIONS

Early detection of ABCB1 gene expression levels could be important for the diagnosis and monitoring of ALL patients.

Association of germline genetic variants in RFC, IL15 and VDR genes with minimal residual disease in pediatric B-cell precursor ALL

Minimal residual disease (MRD) enables reliable assessment of risk in acute lymphoblastic leukemia (ALL). However, little is known on association between MRD status and germline genetic variation. We examined 159 Caucasian (Slavic) patients with pediatric ALL, treated according to ALL-IC-BFM 2002/2009 protocols, in search for association between 23 germline polymorphisms and MRD status at day 15, day 33 and week 12, with adjustment for MRD-associated clinical covariates. Three variants were significantly associated with MRD: rs1544410 in VDR (MRD-day15); rs1051266 in RFC (MRD-day33, MRD-week12), independently and in an additive effect with rs10519613 in IL15 (MRD-day33). The risk alleles for MRD-positivity were: A allele of VDR (OR = 2.37, 95%CI = 1.07–5.21, P = 0.03, MRD-day15); A of RFC (OR = 1.93, 95%CI = 1.05–3.52, P = 0.03, MRD-day33 and MRD-week12, P < 0.01); A of IL15 (OR = 2.30, 95%CI = 1.02–5.18, P = 0.04, MRD-day33). The risk for MRD-day33-positive status was higher in patients with risk alleles in both RFC and IL15 loci than in patients with risk alleles in one locus or no risk alleles: 2 vs. 1 (OR = 3.94, 95% CI = 1.28–12.11, P = 0.024), 2 vs. 0 (OR = 6.75, 95% CI = 1.61–28.39, P = 0.012). Germline variation in genes related to pharmacokinetics/pharmacodynamics of anti-leukemic drugs and to anti-tumor immunity of the host is associated with MRD status and might help improve risk assessment in ALL.

ABCB1 polymorphisms correlate with susceptibility to adult acute leukemia and response to high-dose methotrexate

The aim of this study is to investigate the association of ABCB1 polymorphisms with susceptibility to adult acute leukemia, and the influence of ABCB1 polymorphisms on the efficacy of high-dose methotrexate (HDMTX). ABCB1 polymorphisms in 178 acute leukemia patients (case group) and 150 healthy subjects (control group) were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. All patients received HDMTX therapy. Correlation analysis was performed to explore the associations of ABCB1 polymorphisms with MTX concentration and efficacy of MTX therapy. All statistical analyses were conducted with SPSS 19.0 software. The frequency of TT genotype and T allele on ABCB1 3435C > T in case group were significantly higher than the control group (P < 0.05), while no statistical difference between the two groups was observed in genotypic distribution and allele frequencies of ABCB1 2677G > T/A (P > 0.05). Furthermore, 24-h MTX concentration of patients carrying TT and TA genotypes on 2677G > T/A was higher than carriers with other genotypes (P < 0.05), and 24-h MTX concentration of patients with TT and CT genotypes on 3435C > T was also apparently higher than carriers with CC genotype (P < 0.05). In addition, ABCB1 polymorphisms were connected with increased risk of liver dysfunction and infection (P < 0.05). Complete remission (CR) rate in patients carrying GG on 2677G > T/A was markedly lower than carriers with non-GG genotype (P < 0.05). ABCB1 3435C > T polymorphisms may be associated with susceptibility to acute leukemia, and ABCB1 polymorphisms might be a sensitive indicator for predicting efficacy of MTX therapy in the treatment of acute leukemia.