Abbreviations: ABCC1, ATP-binding cassette, sub-family C, member 1; ALL, acute lymphoblastic leukemia; BFM, Berlin-Frankfurt-Münster; ECHO, echocardiography; LV, left ventricular; LVEDD, left ventricular end-diastolic-dimension; LVESD, left ventricular endsystolic dimension; LVFS, left ventricular fractional shortening; MRP1: multidrug resistanceassociated protein 1. 2 AbstractAnthracyclines are potent cytostatic drugs the correct dosage of which is critical to aviod possible cardiac side effects. ABCC1 (MRP1) is expressed in the heart and takes part in the detoxification and protection of the cells from toxic effects of xenobiotics, including anthracyclines. Our objective was to search for associations between left ventricular function and single nucleotide polymorphisms of the ABCC1 gene in children who received anthracycline chemotherapy. We analyzed data of 235 pediatric patients with acute lymphoblastic leukemia. Patients were followed up by echocardiography (median follow up 6.3 years). Nine polymorphisms in the ABCC1 gene were genotyped. The ABCC1 rs3743527TT genotype and rs3743527TT-rs246221TC/TT genotype combination were found to be associated with lower left ventricular fractional shortening (LVFS) after chemotherapy. Our results suggest that genetic variants in the ABCC1 gene could influence anthracycline induced left ventricular dysfunction.

Inter-individual differences in toxic symptoms and pharmacokinetics of highdose methotrexate (MTX) treatment may be caused by genetic variants in the MTX pathway. Correlations between polymorphisms and pharmacokinetic parameters and the occurrence of hepato-and myelotoxicity were studied. Single nucleotide polymorphisms (SNPs) of the ABCB1, ABCC1, ABCC2, ABCC3, ABCC10, ABCG2, GGH, SLC19A1 and NR1I2 genes were analyzed in 59 patients with osteosarcoma. Univariate association analysis and Bayesian network-based Bayesian univariate and multilevel analysis of relevance (BN-BMLA) were applied. Rare alleles of 10 SNPs of ABCB1, ABCC2, ABCC3, ABCG2 and NR1I2 genes showed a correlation with the pharmacokinetic values and univariate association analysis. The risk of toxicity was associated with five SNPs in the ABCC2 and NR1I2 genes. Pharmacokinetic parameters were associated with four SNPs of the ABCB1, ABCC3, NR1I2, and GGH genes, and toxicity was shown to be associated with ABCC1 rs246219 and ABCC2 rs717620 using the univariate and BN-BMLA method. BN-BMLA analysis detected relevant effects on the AUC 0-48 in the following SNPs: ABCB1 rs928256, ABCC3 rs4793665, and GGH rs3758149. In both univariate and multivariate analyses the SNPs ABCB1 rs928256, ABCC3 rs4793665, GGH rs3758149, and NR1I2 rs3814058 SNPs were relevant. These SNPs should be considered in future dose individualization during treatment.

BackgroundWe carried out a candidate gene association study in pediatric acute lymphoblastic leukemia (ALL) to identify possible genetic risk factors in a Hungarian population.MethodsThe results were evaluated with traditional statistical methods and with our newly developed Bayesian network based Bayesian multilevel analysis of relevance (BN-BMLA) method. We collected genomic DNA and clinical data from 543 children, who underwent chemotherapy due to ALL, and 529 healthy controls. Altogether 66 single nucleotide polymorphisms (SNPs) in 19 candidate genes were genotyped.ResultsWith logistic regression, we identified 6 SNPs in the ARID5B and IKZF1 genes associated with increased risk to B-cell ALL, and two SNPs in the STAT3 gene, which decreased the risk to hyperdiploid ALL. Because the associated SNPs were in linkage in each gene, these associations corresponded to one signal per gene. The odds ratio (OR) associated with the tag SNPs were: OR = 1.69, P = 2.22x10-7 for rs4132601 (IKZF1), OR = 1.53, P = 1.95x10-5 for rs10821936 (ARID5B) and OR = 0.64, P = 2.32x10-4 for rs12949918 (STAT3). With the BN-BMLA we confirmed the findings of the frequentist-based method and received additional information about the nature of the relations between the SNPs and the disease. E.g. the rs10821936 in ARID5B and rs17405722 in STAT3 showed a weak interaction, and in case of T-cell lineage sample group, the gender showed a weak interaction with three SNPs in three genes. In the hyperdiploid patient group the BN-BMLA detected a strong interaction among SNPs in the NOTCH1, STAT1, STAT3 and BCL2 genes. Evaluating the survival rate of the patients with ALL, the BN-BMLA showed that besides risk groups and subtypes, genetic variations in the BAX and CEBPA genes might also influence the probability of survival of the patients.ConclusionsIn the present study we confirmed the roles of genetic variations in ARID5B and IKZF1 in the susceptibility to B-cell ALL. With the newly developed BN-BMLA method several gene-gene, gene-phenotype and phenotype-phenotype connections were revealed. We showed several advantageous features of the new method, and suggested that in gene association studies the BN-BMLA might be a useful supplementary to the traditional frequentist-based statistical method.

We carried out a detailed comparative study of the pharmacokinetics and toxicity of methotrexate (MTX) and 7-hydroxy-methotrexate (7-OH-MTX) after high-dose intravenous methotrexate (HD-MTX) in children with acute lymphoblastic leukemia (ALL). Overall, 65 children were treated with 5 g/m2/24 h MTX and 88 children were treated with 2 g/m2/24 h MTX according to ALL-BFM 95 and ALL IC-BFM 2002 protocols (mean age: 6.4 years, range 1.0-17.9 years). A total of 583 HD-MTX courses were analyzed. Serum MTX and 7-OH-MTX levels were measured at 24, 36, and 48 h, and cerebrospinal fluid (CSF) MTX levels were determined 24 h after the initiation of the infusion. The area under the concentration-time curve was calculated. Hepatotoxicity, nephrotoxicity, and bone marrow toxicity were estimated by routine laboratory tests. We investigated pharmacokinetics and toxicity in distinct age groups (< 6 and > 14 years). 5 g/m2/24 h treatments resulted in higher serum and CSF MTX and 7-OH-MTX levels (P < 0.05). The CSF penetration rate of MTX was independent of the MTX dose [2.3% (95% confidence interval: 1.7-2.5%) vs. 2.8% (95% confidence interval: 2.4-3%)]. The CSF MTX concentration was correlated with the 24 h MTX serum level (r = 0.38, P < 0.0001). Repeated treatments did not alter MTX or 7-OH-MTX levels. 7-OH-MTX levels were correlated with nephrotoxicity (r = 0.36, P < 0.0001). Higher MTX levels and toxicity occurred more frequently in children aged older than 14 years (P < 0.05). Therapeutic serum and CSF MTX concentrations can be achieved more reliably with 5 g/m2/24 h treatments. To predict the development of toxicity, monitoring of the level of the 7-OH-MTX is useful. Monitoring of pharmacokinetics is essential to prevent the development of severe adverse events in adolescents.