GDF2 and neoplasm: Compared with HepG2.2.15 tumour‐bearing mice, treatment with NK cells exerted better anti‐tumour effects on HepG2 and HepG2.2.15‐BMP9 tumour‐bearing mice (Figure 6B top panel; 6C, D red icon) and a greater number of infiltrating NK cells (Figure 6E, red icon, Supporting Information Figure S7B).