The latter is the result of a multitude of means by which glioblastoma hijacks the immune system including the kynurenine-tryptophan (IDO-TDO1) pathway, expression of pro-mitogenic, immunosuppressive EVs, the release of anti-inflammatory cytokines, and manipulation of checkpoint proteins (e.g., PD-1, CTLA-4). This evidence concerns the gene CTLA4 and glioblastoma.