CD28 and hepatocellular carcinoma: provided a new CAR screening platform that may facilitate CAR-NK design and showed that the in vitro cytotoxicity against hepatocellular carcinoma (HCC) cells was greater with DNAM-1-2B4-glypican 3 (GPC3)-targeted CAR-NK cells than with anti-GPC3 CAR-NK cells containing other co-stimulatory domains (CD3ζ, CD28-CD3ζ, DNAM-1-CD3ζ and 2B4-CD3ζ) (33).