GBM cells deliver immunosuppressive proteins such as CD73, CD39, programmed cell death ligand 1 (PD-L1), and cytotoxic T lymphocyte-associated protein 4 (CTLA-4) into the local microenvironment through extracellular vesicles, leading to immune cell function impairment and tumor progression (49). Here, CTLA4 is linked to neoplasm.