3371

TNC

150-225|GMEM|GP|HXB|JI|TN|TN-C;tenascin C;TNC;tenascin C

GP 150-225|cytotactin|glioma-associated-extracellular matrix antigen|hexabrachion (tenascin)|myotendinous antigen|neuronectin|tenascin|tenascin-C isoform 14/AD1/16

9q33

protein-coding

PURPOSE: The molecular pathogenesis of pediatric ependymoma remains unclear. Ourstudy was designed to identify genetic changes implicated in ependymoma progression. PATIENTS AND METHODS: We characterized 59 ependymoma samples (33 atdiagnosis and 26 at relapse) using array-comparative genomic hybridization (aCGH). Specific chromosomal imbalances were confirmed by fluorescent in situ hybridization, and candidate genes were assessed by real-time quantitative polymerase chain reaction (qPCR), immunohistochemistry, sequencing, and in vitrofunctional studies. RESULTS: aCGH analysis revealed a significant increase in genomic imbalances on relapse compared with diagnosis, such as gain of 9qter and1q (54% v 21% and 12% v 0%, respectively) and loss of 6q (27% v 6%). Supervised tumor classification showed that gain of 9qter was associated with tumor recurrence, age older than 3 years, and posterior fossa location. Using a candidate-gene strategy, we found an overexpression of two potential oncogenes at the locus 9qter: Tenascin-C and Notch1. Moreover, Notch pathway analysis (qPCR) revealed overexpression of Notch ligands, receptors, and target genes (Hes-1, Hey2, and c-Myc), and downregulation of Notch repressor Fbxw7. We confirmed by immunohistochemistry the overexpression of Tenascin-C and Hes-1. We detected Notch1 missense mutations in 8.3% of the tumors (only in the posterior fossa location and in case of 9q33-34 gain). Furthermore, inhibition of Notch pathway with a gamma-secretase inhibitor impaired the growth of ependymoma stem cell cultures. CONCLUSION: The activation of the Notch pathway and Tenascin-C seem tobe important events in ependymoma progression and may represent future targets for therapy. We report, to our knowledge for the first time, recurrent oncogenicmutations in pediatric posterior fossa ependymomas.