FAS and cancer: Cancer-associated exosomes not only shuttle immune regulatory molecules such as PD-L1, TRAIL, TGF-β, IL-10, FasL, galectin-9, HSP72, and PGE2 to exert an immunosuppressive effect, but they also to trigger the Fas/FasL pathway and induce apoptosis in CD8+ T cells [145,146,206,207,208,209,210].