Knockdown of PAK4 can suppress cell proliferation, migration, and invasion of ESCC. (A) Endogenous PAK4 expression was efficiently decreased by shRNA targeting PAK4 (shpak4‐1 and shpak4‐2) in EC109 and KYSE450 cells, as detected by Western blot analysis. The proliferation of EC109 and KYSE450 cells stably infected with shpak4‐1, shpak4‐2, or shmock was examined using a cell viability assay (B) and a soft agar colony formation assay (C). The asterisks indicate that the rate of cell proliferation in shpak4 EC109 and KYSE450 cells was significantly lower than that in shmock EC109 and KYSE450 cells (*p < .05, **p < .01, ***p < .001). Data are shown as the mean ± SD from triplicate experiments. The migration and invasion of EC109 and KYSE450 cells infected with shpak4‐1, shpak4‐2, or shmock were examined by wound healing assay (D) and Transwell invasion assay (E). The asterisks indicate that the cell migration and invasion in shpak4 EC109 and KYSE450 cells were significantly lower than that in shmock EC109 and KYSE450 cells (*p < .05, **p < .01, ***p < .001). Data are shown as the mean ± SD from triplicate experiments. ESCC, esophageal squamous cell carcinoma [Color figure can be viewed at wileyonlinelibrary.com]