IT-14 MESENCHYMAL GLIOMA STEM CELL EXPRESS ICOSL

Human glioblastoma is the most aggressive human primary brain tumor and is currently incurable. Immunitherapies have the pontential to target glioma and glioma stem cells (GSCs) that are resistant to conventional thepies. We previously identified and characterized two mutually exclusive GSC subtypes with distinct dysregulated signaling pathways. Analysis of mRNA profiles distinguished proneural (PN) from mesenchymal (Mes) GSCs and revealed a pronounced correlation with the corresponding PN or Mes HGGs. Here we show the expression of Inducible costimulator-ligand (ICOSL) by glioma cells in vitro and in vivo. We identified that Mes GSCs specificaly expressd ICOSL, however, PN GSCs did not express it. Further, immunohistochemical analysis of human brain tumors demonstrates the expression of ICOSL around the vessels. ICOSL is a member of the B7 family of costimulatory molecules related to CD80/CD86, regulates CD4 as well as CD8 T-cell responses via interaction with its receptor, ICOS, on activated T cells. ICOSL could be a novel target for immunotherapy.