TNF and cancer: Programmed Death-Ligand 1 (PD-L1), Tumor Necrosis Factor (TNF), Fas Ligand (FasL) and TNF-Related Apoptosis-Inducing Ligand (TRAIL) are the main exosomal ligands and their receptors are located on the surface of tumor cells, becoming potential targets for cancer therapies [27,28] (Figure 3).