IM-10: EFFECTS OF T-CELL TGF-β SIGNALING ABROGATION ON SURVIVAL IN PEDIATRIC GLIOMA

We have been investigating the effects of immune system modulation on brain tumor survival in animal models of pediatric malignancies. For example, TGF-β is produced by various tumor types and dampens the response of the immune system, preventing recognition of tumor cells. Thus, we crossed mice with T-cell-specific TGF-β blockade (CD4-TGFβRII-DNR) with a mouse model of medulloblastoma (SmoA1 transgenic mice) and analyzed offspring. We noted dramatic infiltration of T cells into the tumor and coincident improvement in survival of these mice. Furthermore, there was a striking change in T cell phenotype—notably a large increase in memory T cells in double transgenic mice, which are in principle able to mount anti-tumor immunity. We've been employing a novel piggyBac model of forebrain glioma to rapidly generate tumors from patient driver genes. Interestingly, using genome-wide analysis, many members of the TGF-β ligand family are upregulated by tumor cells and these secreted ligands appear to be the principle immunosuppressive molecules expressed by the tumor propagating population. Given the survival-promoting role of T cell TGF-β signaling blockade in our medulloblastoma model, we have generated de novo tumors in CD4-TGFβRII-DNR mice using our in vivo piggyBac system and are investigating the applicability of this strategy in pediatric forebrain glioma.