Inter-individual variation of several cytochrome P450 2D6 splice variants in human liver.

To examine the possibility that inter-individual differences in splicing partially explain the observed differences in CYP2D6 activity, we amplified its full-length cDNA in 96 human liver RNA samples and discovered five splice variants: intron 5 retention, intron 6 retention, intron 5 and intron 6 double retention, exon 3 skipping, and partial intron 1 retention. All of the CYP2D6 splice variants we identified are probably nonfunctional transcripts. Substantial inter-individual variation in the proportions of the CYP2D6 transcript represented by splice variants, measured by real-time PCR, suggests that the presence of these splice variants contributes to the population variation in CYP2D6 activity.

Combination of early perinatal factors to identify near-term and term neonates for neuroprotection.

Objective: To determine early predictors of abnormal outcome at > or =24 months' age in neonates at risk for hypoxic-ischemic brain injury.

Study Design: A prospective cohort study with developmental follow-up of > or =24 months. Infants were selected based on risk factors, and neurologic outcome was determined.

Folate pathway gene expression differs in subtypes of acute lymphoblastic leukemia and influences methotrexate pharmacodynamics.

The ability of leukemia cells to accumulate methotrexate polyglutamate (MTXPG) is an important determinant of the antileukemic effects of methotrexate (MTX). We measured in vivo MTXPG accumulation in leukemia cells from 101 children with acute lymphoblastic leukemia (ALL) and established that B-lineage ALL with either TEL-AML1 or E2A-PBX1 gene fusion, or T-lineage ALL, accumulates significantly lower MTXPG compared with B-lineage ALL without these genetic abnormalities or compared with hyperdiploid (fewer than 50 chromosomes) ALL. To elucidate mechanisms underlying these differences in MTXPG accumulation, we used oligonucleotide microarrays to analyze expression of 32 folate pathway genes in diagnostic leukemia cells from 197 children.

Lymphoid gene expression as a predictor of risk of secondary brain tumors.

Gene expression profiles are tissue-specific but may also reflect germ-line-driven expression patterns across tissue types. Previously, using a targeted pharmacologic approach, we identified germ-line polymorphisms in a single gene (thiopurine methyltransferase) associated with the risk of irradiation- and chemotherapy-induced secondary brain tumors in children with acute lymphoblastic leukemia (ALL). To identify additional candidate genetic risk factors, in identically treated patients, we compared the gene expression profiles of diagnostic ALL blasts of those who did develop irradiation-associated brain tumors (n = 9) with the profiles from those who did not (n = 33).

Pharmacogenetic risk factors for osteonecrosis of the hip among children with leukemia.

Purpose: One of the adverse effects of therapy for acute lymphoblastic leukemia (ALL) is osteonecrosis of the hip. Putative risk factors for osteonecrosis have included being female, white race, and older age. Our goal was to define possible genetic risk factors for osteonecrosis among children treated for newly diagnosed ALL.

Gene-expression patterns in drug-resistant acute lymphoblastic leukemia cells and response to treatment.

Background: Childhood acute lymphoblastic leukemia (ALL) is curable with chemotherapy in approximately 80 percent of patients. However, the cause of treatment failure in the remaining 20 percent of patients is largely unknown.

Methods: We tested leukemia cells from 173 children for sensitivity in vitro to prednisolone, vincristine, asparaginase, and daunorubicin.

Acute lymphoblastic leukemia with TEL-AML1 fusion has lower expression of genes involved in purine metabolism and lower de novo purine synthesis.

Because de novo purine synthesis (DNPS) is a target of widely used antileukemic agents (eg, methotrexate, mercaptopurine), we determined the rate of DNPS and the expression of genes involved in purine metabolism in different subtypes of acute lymphoblastic leukemia (ALL). Among 113 children with newly diagnosed ALL, lymphoblasts with the TEL-AML1 translocation had significantly lower DNPS than all other genetic subtypes of B-lineage ALL or T-lineage ALL (352 +/- 57 versus 1001 +/- 31 or versus 1315 +/- 76 fmol/nmol/h, P <.0001).

Effects of prednisone and genetic polymorphisms on etoposide disposition in children with acute lymphoblastic leukemia.

Etoposide is a substrate for P-glycoprotein, CYP3A4, CYP3A5, and UGT1A1. Glucocorticoids modulate CYP3A and P-glycoprotein in preclinical models, but their effect on clinical etoposide disposition is unknown. We studied the pharmacokinetics of etoposide and its catechol metabolite in children with acute lymphoblastic leukemia, along with polymorphisms in CYP3A4, CYP3A5, MDR1, GSTP1, UGT1A1, and VDR.

Treatment-specific changes in gene expression discriminate in vivo drug response in human leukemia cells.

To elucidate the genomics of cellular responses to cancer treatment, we analyzed the expression of over 9,600 human genes in acute lymphoblastic leukemia cells before and after in vivo treatment with methotrexate and mercaptopurine given alone or in combination. Based on changes in gene expression, we identified 124 genes that accurately discriminated among the four treatments. Discriminating genes included those involved in apoptosis, mismatch repair, cell cycle control and stress response.

Neurobiologic risk score and long-term developmental outcomes of premature infants, birth weight less than 1,250 grams.

Objective: To determine whether neurobiologic risk score (NBRS) would continue to correlate with developmental outcomes.

Method: An observational cohort consisting of 258 surviving infants who returned to the follow-up clinic with a mean age 22 months' corrected age. Both univariate and multivariate analysis were performed to identify risk factors and to assess the predictive value of NBRS.

Efficacy and safety of tolazoline for treatment of severe hypoxemia in extremely preterm infants.

Objective: To determine the efficacy of tolazoline as a rescue treatment for hypoxemia in preterm infants with respiratory distress syndrome.

Methods: Retrospective chart review on case series of infants weighing < 750 g at birth who received tolazoline during a severe hypoxemic episode while receiving maximal ventilator support for respiratory distress syndrome. A slow bolus infusion of low dose tolazoline (0.