Resistance of bcr-abl-positive acute lymphoblastic leukemia to daunorubicin is not mediated by mdr1 gene expression

Evaluation of the pharmacokinetics of prednisolone in paediatric patients with acute lymphoblastic leukaemia treated according to Dutch Childhood Oncology Group protocols and its relation to treatment response

Glucocorticoids form the backbone of paediatric acute lymphoblastic leukaemia (ALL) treatment. Many studies have been performed on steroid resistance; however, few studies have addressed the relationship between dose, concentration and clinical response. The aim of the present study was to evaluate the pharmacokinetics of prednisolone in the treatment of paediatric ALL and the correlation with clinical parameters. A total of 1028 bound and unbound prednisolone plasma concentrations were available from 124 children (aged 0–18 years) with newly diagnosed ALL enrolled in the Dutch Childhood Oncology Group studies. A population pharmacokinetic model was developed and post hoc area under the curve (AUC) was tested against treatment outcome parameters. The pharmacokinetics of unbound prednisolone in plasma was best described with allometric scaling and saturable binding to proteins. Plasma protein binding decreased with age. The AUC of unbound prednisolone was not associated with any of the disease parameters or treatment outcomes. Unbound prednisolone plasma concentrations correlated with age. No effect of exposure on clinical treatment outcome parameters was observed and does not substantiate individualised dosing. Poor responders, high‐risk and relapsed patients showed a trend towards lower exposure compared to good responders. However, the group of poor responders was small and requires further research.

In vitro effect of curcumin in combination with chemotherapy drugs in Ph+ acute lymphoblastic leukemia cells

Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL), is characterized by the t(9;22)(q34q11) that generates the BCR-ABL protein with uncontrolled tyrosine kinase activity. Recently, a connection between BCR-ABL signaling with NF-κB activation mediated by CK2 has been hypothesized. Approximately 95% of patients with Ph+ ALL have the BCR-ABLp190 isoform, which causes aggressive leukemia with a high rate of chemotherapy resistance. Therefore, the use of compounds that could improve the efficacy of chemotherapy drugs is of particular interest. Curcumin is an active chemical in turmeric with antineoplastic potential; it regulates protein-kinases by modulating downstream molecular pathways. The present study evaluated the effect of curcumin in combination with the chemotherapeutic drugs vincristine, imatinib and daunorubicin in the human OP-1 cell line. Several doses of the chemotherapy drugs were examined, and the effects were evaluated following 12, 24 and 48 h of exposure. The interaction between the chemotherapy drugs and curcumin was determined by the dose-effect curve, which generated a combination index (CI); these data were represented in isobolograms. In addition, the individual effect of each drug was compared with its effect in combination with curcumin on cell viability, apoptosis degree, NF-κB activation and gene expression changes. The present study observed that curcumin potentiates the efficacy of vincristine and imatinib, generating an additive/synergistic effect in a dose- and time-dependent manner. These combinations significantly increased the apoptosis degree, decreased the activation of NF-κB and the expression of its regulated genes. Conversely treatment with daunorubicin + curcumin combination produced an antagonistic/additive effect in a dose-dependent manner, and this combination significantly increased the apoptosis degree. However, this effect seems not to be associated with NF-κB activity, as no significant changes were observed in its activation or in the expression of the genes that it regulates. The results of the present study demonstrate that curcumin may be used as an adjuvant agent for chemotherapy in patients with Ph+ ALL.

Mapping genes that contribute to daunorubicin-induced cytotoxicity

Daunorubicin is an anthracycline antibiotic agent used in the treatment of hematopoietic malignancies. Toxicities associated with this agent include myelosuppression and cardiotoxicity; however, the genes or genetic determinants that contribute to these toxicities are unknown. We present an unbiased genome-wide approach that incorporates heritability, whole-genome linkage analysis, and linkage-directed association to uncover genetic variants contributing to the sensitivity to daunorubicin-induced cytotoxicity. Cell growth inhibition in 324 Centre d' Etude du Polymorphisme Humain lymphoblastoid cell lines (24 pedigrees) was evaluated following treatment with daunorubicin for 72 h. Heritability analysis showed a significant genetic component contributing to the cytotoxic phenotypes (h2 = 0.18-0.63 at 0.0125, 0.025, 0.05, 0.1, 0.2, and 1.0 mumol/L daunorubicin and at the IC50, the dose required to inhibit 50% cell growth). Whole-genome linkage scans at all drug concentrations and IC50 uncovered 11 regions with moderate peak LOD scores (> 1.5), including 4q28.2 to 4q32.3 with a maximum LOD score of 3.18. The quantitative transmission disequilibrium tests were done using 31,312 high-frequency single-nucleotide polymorphisms (SNP) located in the 1 LOD confidence interval of these 11 regions. Thirty genes were identified as significantly associated with daunorubicin-induced cytotoxicity (P < or = 2.0 x 10(-4), false discovery rate < or = 0.1). Pathway and functional gene ontology analysis showed that these genes were overrepresented in the phosphatidylinositol signaling system, axon guidance pathway, and GPI-anchored proteins family. Our findings suggest that a proportion of susceptibility to daunorubicin-induced cytotoxicity may be controlled by genetic determinants and that analysis using linkage-directed association studies with dense SNP markers can be used to identify the genetic variants contributing to cytotoxicity.

Multiple drug resistance protein (MDR-1), multidrug resistance-related protein (MRP) and lung resistance protein (LRP) gene expression in childhood acute lymphoblastic leukemia

CONTEXT

Despite the advances in the cure rate for acute lymphoblastic leukemia, approximately 25% of affected children suffer relapses. Expression of genes for the multiple drug resistance protein (MDR-1), multidrug resistance-related protein (MRP), and lung resistance protein (LRP) may confer the phenotype of resistance to the treatment of neoplasias.

OBJECTIVE

To analyze the expression of the MDR-1, MRP and LRP genes in children with a diagnosis of acute lymphoblastic leukemia via the semiquantitative reverse transcription polymerase chain reaction (RT-PCR), and to determine the correlation between expression and event-free survival and clinical and laboratory variables.

DESIGN

A retrospective clinical study.

SETTING

Laboratory of Pediatric Oncology, Department of Pediatrics, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Brazil.

METHODS

Bone marrow aspirates from 30 children with a diagnosis of acute lymphoblastic leukemia were assessed for the expression of messenger RNA for the MDR-1, MRP and LRP genes by semi-quantitative RT-PCR.

RESULTS

In the three groups studied, only the increased expression of LRP was related to worsened event-free survival (p = 0.005). The presence of the common acute lymphoblastic leukemia antigen (CALLA) was correlated with increased LRP expression (p = 0.009) and increased risk of relapse or death (p = 0.05). The relative risk of relapse or death was six times higher among children with high LRP expression upon diagnosis (p = 0.05), as confirmed by multivariate analysis of the three genes studied (p = 0.035).

DISCUSSION

Cell resistance to drugs is a determinant of the response to chemotherapy and its detection via RT-PCR may be of clinical importance.

CONCLUSIONS

Evaluation of the expression of genes for resistance to antineoplastic drugs in childhood acute lymphoblastic leukemia upon diagnosis, and particularly the expression of the LRP gene, may be of clinical relevance, and should be the object of prospective studies.