TREM2 and glioblastoma: Similarly, TREM2 is highly expressed in glioblastoma (GBM), and its expression is consistent with the expression of inhibitory immune checkpoints such as PD-L1, PD-L2, and Galectin-9, suggesting that TREM2 may inhibit T cell-mediated immune responses by regulating the expression of immune checkpoints, thereby promoting glioma cell immune escape (21).