CD274 and cancer: Moreover, CAFs contribute to immune evasion by expressing immune checkpoint ligands such as cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and programmed death-ligand 1 (PD-L1), which engage effector T cells Cancer cells secrete paracrine factors such as IL-1, which activate NF-κB signaling and the expression of leukemia inhibitory factor (LIF) in iCAFs.