CTLA4 and glioblastoma: Investigation of checkpoint inhibition of PD-1 and CTLA-4 on their own as well as in combination in wildtype and CD73-deficient mice confirmed the hypothesized role of CD73 in GBM: Therapeutical outcome was superior when both checkpoints were targeted in combination as opposed to single administration, which seems plausible as they are often co-expressed in glioblastoma.