MAPK1 and lung adenocarcinoma: To further confirm that ERK is a downstream effector of MAP4K4 signaling in lung adenocarcinoma cells, we transfected MAP4K4‐knockdown cells with plasmid expressing constitutively active ERK2L73P/S151D, and the results showed that overexpression of active ERK2 antagonized MAP4K4 downregulation‐mediated inhibition of cell functions (Fig. 3D–F).