CD274 and cancer: pSTAT3 + reactive astrocytes hinder the access of CD8 + cytotoxic T cells to cancer cells by increasing the expression of specific immunosuppressive molecules, such as programmed cell death-1 ligand 1 (PD-L1), VEGF-A, lipocalin-2, and tissue inhibitor of metalloproteinases-1 (TIMP-1).