PDCD1 and hepatocellular carcinoma: Besides the PD1/PD-L1-dependent mechanism, recurrent HCC cells that expressed a high level of stemness marker genes tend to express a lower level of HLA molecules and resulting potentially in less neoantigen presentation, which facilitate their evasion from adaptive immunity.125 To overcome this, innate immune cells such as cytokine-induced killer cells, a form of CD3+ and CD56+ natural killer (NK) cells, which targets and eradicates LCSCs through an NK group 2D ligand-dependent mechanism might be employed instead.126