LAB-PEDIATRICS LABORATORY RESEARCH

0 PL-03. PHARMACOLOGIC INHIBITION OF EZH2 SUPPRESSES SELF-RENEWAL AND INDUCES RADIATION SENSITIVITY IN ATYPICAL RHABDOID TERATOID TUMOR CELLS Irina Alimova 1 University of Nottingham , Nottingham, United Kingdom 2 PL-02. MOLECULAR CHARACTERIZATION OF MUTATED HISTONE H3.3 IN PEDIATRIC GLIOBLASTOMA Sebastian Bender 3 University of Colorado , Denver, Aurora, CO 4 The Children's Hospital Colorado , Aurora, CO 5 PL-01. IDENTIFICATION OF NOVEL FUSION GENES IN PEDIATRIC HIGH-GRADE GLIOMA Diana Carvalho 6 Life and Health Sciences Research Institute, University of Minho , Braga, Portugal 7 Great Ormond Street Hospital , London, United Kingdom 8 PL-04. INHIBITION OF CYCLIN-DEPENDENT KINASE 6 SUPPRESSES CELL GROWTH AND ENHANCES RADIATION SENSITIVITY IN MEDULLOBLASTOMA CELLS Susan Whiteway 9 Hospital San Joan de Deu , Barcelona, Spain 10 Complejo Hospitalario de Navarra , Pamplona, Spain 11 University Hospital of Navarra , Pamplona, Spain 12 PL-05. DELTA-24-RGD IN COMBINATION WITH SALINOMYCIN FOR THE TREATMENT OF HIGH-GRADE PEDIATRIC GLIOMAS Enric Xipell 13 The University of Texas MD Anderson Cancer Center , Houston, TX 14 Department of Histopathology, Great Ormond Street Hospital for Children NHS Trust , London, United Kingdom 15 PL-11. EPIGENETIC GENOME-WIDE ANALYSIS IDENTIFIES BEX1 AS A CANDIDATE TUMOR SUPPRESSOR GENE IN PEDIATRIC EPENDYMOMA Katherine Karakoula 16 Department of Neurosurgery, Great Ormond Street Hospital for Children NHS Trust , London, United Kingdom 17 Brain Tumour UK Neuro-Oncology Research Centre, University of Wolverhampton , Wolverhampton, United Kingdom 18 PL-10. TARGETING THE NOTCH AND MTOR PATHWAYS IN DIFFUSE INTRINSIC PONTINE GLIOMA Marianne Hutt 19 Michigan State University College of Medicine , East Lansing, MI 20 Cedars-Sinai Medical Center and the David Geffen School of Medicine, University of California , Los Angeles, Los Angeles, CA 21 Cedars-Sinai Medical Center, Department of Neurosurgery , Los Angeles, CA 22 Cedars-Sinai Medical Center , Los Angeles, CA 23 PL-16. BLOCKADE OF T CELL TRANSFORMING GROWTH FACTOR-BETA SIGNALING MITIGATES MEDULLOBLASTOMA PROGRESSION IN TRANSGENIC MICE Rachelle Levy Published by Oxford University Press on behalf of the Society for Neuro-Oncology 2012. - Chromosomal rearrangements resulting in novel fusion genes are among the most prevalent form of genetic alterations known in cancer, and numerous examples exist in both adult and childhood malignancies. To date, however, none have been reported in pediatric high-grade glioma (pHGG), so we have undertaken to search for novel structural rearrangements using three distinct techniques. Firstly, we took a candidate approach and screened a series of 83 pHGG for the fusion previously described in adult glioblastoma between PDGFRA and KDR (VEGFR2) at 4q12. Using RT-PCR and sequencing, we identified the second reported instance of KDR:PDGFRA in a single case of glioblastoma (age 1.2 years). Next, we applied the iCNA algorithm to identify copy number aberrations with intragenic breakpoints using Affymetrix 500K SNP data from a cohort of 100 pHGG, identifying two candidates arising from genomic amplification and intrachromosomal rearrangement in an analogous mechanism to KDR:PDGFRA. We finemapped the breakpoints using custom Agilent oligonucleotide arrays and characterized the fusions DHX57:MAP4K3 (2p22) and CSGALNACT2:RET (10q11) in cases of anaplastic astrocytoma (2 years) and recurrent glioblastoma (12.8 years), respectively. Finally, we sequenced the entire genomes of five pediatric glioma cell lines at .30 coverage using the Illumina HiSeq2000 platform, and screened for rearrangements using the BreakDancer (BD) package. We identified a median of 165 intragenic structural variants per genome that were filtered based on BD confidence score, number and orientation of reads and by visual inspection using IGV software. Candidate fusions being systematically validated and screened in our pHGG cohorts include interchromosomal rearrangements resulting in TULP4:RPTOR (t6;17 - SF188), GORASP2:CDADC1 (t2;13 - KNS42) and C15ORF57:CBX3 (t15;7 - UW479). These data highlight the presence of hitherto unrecognized fusion genes in pHGG which may play important roles in the unique biology of the tumors as well as provide excellent candidates for novel therapeutic strategies. Recently, we and others identified the first recurrent somatic mutations in a histone gene (H3F3A) in one-third of pediatric glioblastoma (pedGBM), the most devastating brain tumor in childhood. The observed mutations in H3F3A, coding for the non-canonical histone variant H3.3, led to amino acid substitutions at two critical residues of the histone tail (K27M and G34R), at or near sites of important post-translational modifications. Furthermore, we have shown that pedGBMs carrying K27M or G34R mutations are characterized by distinct gene expression and DNA methylation profiles. This clearly shows that different signalling pathways predominate in K27M or G3 (...truncated)