PM-09 * ESTABLISHMENT AND MOLECULAR CHARACTERIZATION OF PATIENT-DERIVED XENOGRAFT MODELS OF PEDIATRIC BRAIN TUMORS

Abstract

Brain tumors are the leading cause of cancer-related mortality in childhood. Based on the many recent genomic studies, we know now that multiple molecular subtypes of brain cancers exist that are not only biologically but also clinically highly distinct. These findings may lead to novel treatment strategies. For this we need better preclinical models that correctly reflect the proper tumor (sub)type. Orthotopic patient-derived xenograft (PDX) models generated by intracranial injection of primary patient material into the brain of NOD scid gamma (NSG) mice offer the unique possibility to test novel substances in primary patient tissue in an in vivo environment. Prior to drug selection and testing, extensive molecular characterizations are needed to learn about targetable oncogenic drivers in each model. Therefore, we aim to generate a large repertoire of PDX models reflecting the many different molecular subtypes of pediatric brain cancer. For each established PDX model, we perform DNA methylation profiling, gene expression profiling, low-coverage whole genome sequencing and whole exome sequencing and compare these data with the matching primary tumor. Thus far, as a collaborative effort between different laboratories, we have established and fully characterized 34 PDX models from 1 atypical teratoid rhabdoid tumor (ATRT), 4 ependymoma, 9 glioblastoma, 18 medulloblastoma, and 2 primitive neuroectodermal tumors (PNET). Molecular analysis of all available PDX models identified a clear overrepresentation of most aggressive tumors such as models characterized by MYC- or MYCN amplification. Other, less aggressive cancers, like Wnt medulloblastoma, are underrepresented. For in vivo imaging during treatment of PDX models we created luciferase labeled PDX sublines. Our data demonstrate that PDX models retain characteristics of the primary human tumors from which they were derived. These reagents provide an unprecedented resource to study tumor biology and pave the way for improving treatment strategies of malignant pediatric brain tumors.