HAVCR2 and glioblastoma: Flow cytometry analysis of 21 GBM samples and matched peripheral blood identified LAG-3, TIM3, TIGIT, and CD39 as possible immunotherapeutic targets beyond PD-1 and CTLA-4; T cells co-expressing PD-1, LAG-3, TIGIT, and CD39 proved unable to produce IFNγ, IL-2, or TNFα [43].