Cells specific to the central nervous system such as microglia have been shown to be able to contribute to active immune suppression via release of molecules such as FASL and B7-H1 which drive apoptosis of T-cells.42,43 Further research to identify the mechanisms driving poor response of our PDX models in orthotopic contexts will provide new insights into specific therapies to modulate immune response for CNS tumors. Here, FASLG is linked to central nervous system neoplasm.