CREB1 and esophageal squamous cell carcinoma: More importantly, knockout of CREB1 markedly diminished the inhibitory effect of imperatorin on invasion and metastasis of ESCC cells in vitro and in vivo, whereas the repressed sensitivity of CREB1‐knockout ESCC cells to imperatorin was restored upon re‐overexpression of wild‐type CREB1, but not the CREB1 mutant (K304E/K305E) (Figure 6).