KLRK1 and cancer: A series of tumour-specific antigens, such as Glypican 3 (GPC3), epidermal growth factor receptor variant III (EGFRvIII), c-Met, PD-L1, CD133, NK group 2 member D (NKG2D) ligands (NKG2DL) and some viral-derived cancer antigens, have been explored and used to construct CAR-T cells against HCC [21–23].