In solid tumors, T cells face formidable barriers imposed by the immunosuppressive tumor microenvironment (TME), including loss of MHC expression, recruitment of tolerogenic APCs, secretion of inhibitory cytokines (e.g., TGF-β, IL-10), and upregulation of immune checkpoint ligands such as PD-L1 [85]. The gene discussed is CD274; the disease is neoplasm.