CD28 and hepatocellular carcinoma: CD137 is a TNFR-family member with costimulatory function that was originally identified as an inducible molecule expressed on activated CD8+ and CD4+ T cells.10 To evaluate the observed metabolic activity of CD137+CD8+ T cell in HCC microenvironment, we developed CD28 or CD137 CART cells to test the different effects of costimulation signaling.