SC-02 * MODELING PEDIATRIC GBM USING NEURAL STEM CELL-DERIVED TUMORS WITH DIVERGENT BEHAVIOR

Abstract

Pediatric GBM can exhibit a diversity of cell behaviors and responses to therapy despite similar oncogenic drivers. The reasons for this are often unclear. Using a murine model for GBM based on the oncogenic transformation of neural progenitor cells we sought to generate tumors with diverse cell behaviors despite being driven by a common oncogene. Using in vivo tumor phenotype as evidence of divergent tumor behavior, we isolated two tumor lines with different phenotypes. Tumor progenitor cell (TPC) line-A was highly proliferative and resulted in rapid lethality (median overall survival of 22 days) vs. TPC-B that was less proliferative and exhibited a more prolonged survival (median overall survival of 33 days). Interestingly, TPC-A invaded in perivascular fashion in vivo. In contrast, TPC-B tumors invaded diffusely, as single cells. Transcriptional profiling revealed an enrichment of mesenchymal GBM subtype genes in TPC-A (normalized enrichment score of 1.5) and proneural GBM subtype genes in TPC-A (normalized enrichment score of 2.6). Consistent with the gene expression data, TPC-A exhibited increased activation of Stat3 (pY705) relative to TPC-B. Furthermore, while both clones expressed hEGFRvIII, TPC-A cells showed higher levels of EGFR activation (pY1173 and pY1068), than TPC-B cells. In vitro, TPC-A expanded at a higher rate than TPC-B and expressed Prominin-1 (CD133). TPC-B cells were Prominin-1 negative, but more prone to adhere to ECM components than TPC-A, and invaded more extensively in vitro. Moreover, under differentiation conditions, TPC-A failed to differentiate and continuously proliferated. TPC-B differentiated to cells of neuronal, astrocytic, and oligodendrocytic lineages. Interestingly, these lines also exhibited differential response to therapy. In the current project we demonstrate how transduction of neurospheres can be used to generate tumor lines with vastly different cell behaviors, reflective of different pediatric GBM, and that these lines are useful for both mechanistic and preclinical studies.