The activation of NKG2D receptors can promote the release of multiple active proteins from NK cells, such as perforin and granzymes, and can also induce the expression of tumor necrosis factor (TNF) ligand interferon-gamma (IFN-γ) to induce apoptosis of hepatocarcinoma and is beneficial to clean up the tumor (Figure 6). Here, PRF1 is linked to neoplasm.