CTLA4 and glioblastoma: Immune checkpoint inhibitor (ICI) therapy, such as anti-programmed cell death protein- (PD-) 1 or cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) inhibitors, which have made breakthroughs in solid tumors with a higher TMB [6, 7], is in clinical trial in GBM [8, 9].