Figure 2. USP22 silencing inhibits in vitro GC cell proliferation. (A) Representative images show USP22 expression in BGC-823 and HGC-27 cells that were transfected with 100 nM siNC, siUSP22-1, or siUSP22-2 cultured for 24 h. Untransfected (mock) GC cells were used as controls. β-actin was used as an endogenous control. (B) MTT assay results show viability of siNC or siUSP22-1 transfected GC cells at days 1, 2, 3, and 4. (C) Flow cytometry analysis shows the effects of USP22 knockdown in GC cells. The percentage of G1, S-, and G2M cells in siNC or siUSP22-1 transfected GC cells are shown in the histogram plots. (D) EdU assay results show cell proliferation status of siNC or siUSP22-1 transfected GC cells. The plots show the percentage of EdU-positive cells in various samples. Magnification: 100×. (E) Histograms (right) show the total number of colonies in BGC-823 and HGC-27 cells that are uninfected (Mock) or infected with lentiviruses carrying pLKO.1 or pLKO.1-shUSP22 vectors. Representative images of colony formation assay are also shown. Note: Data are expressed as mean ± SD of three replicates; *p < 0.05; **p < 0.01 compared with mock or siNC group in (B–D); *p < 0.05 compared with the mock or pLKO.1 group in (E).