CTLA4 and glioblastoma: As targeting macrophages with CSF1Ri or blocking negative immune checkpoint regulators like PD1, PD-L1 or CTLA4 are not sufficient as stand-alone therapies to improve the outcome in GBM patients, combining these strategies, also in conjunction with standard chemo- and radiation therapies or other immunotherapies are highly anticipated as they may hold great potential for improving the treatment of gliomas (138).