Fig. 1

Bmi-1 positively regulates stem cell-like properties of gastric cancer cells. a Tumorigenic spheres are derived from SGC7901 gastric cancer cell line in serum-free media containing EGF and bFGF (upper panel) and overexpressed stem cell markers including Bmi-1, Oct-4, Sox-2, Nanog, CD44, and CD133 (lower panel). The expression of stem cell markers in the cell lysis was analyzed by Western blot. PC parental cells, SC spheroid cells. b Bmi-1 overexpression upregulates the expression of stem cell markers Oct-4, Sox-2, Nanog, CD44, and CD133 in SGC7901 cells (left panel) and Bmi-1 knockdown downregulates the expression of stem cell markers in MNK45 cells (right panel). The expression of Bmi-1 and stem cell markers in the cell lysis was analyzed by Western blot. c Bmi-1 overexpression improves microsphere formation in SGC7901 cells (left panel), and Bmi-1 knockdown inhibits microsphere formation in MNK45 cells (right panel). Microsphere formation was tested by serum-free suspension culture (left upper panel) and quantified (left lower panel) in Bmi-1 overexpressing cells (Bmi-1) and control cells (vector) and picture of microsphere (right upper panel) and quantified (right lower panel) in Bmi-1 knockdown cells (Bmi-1i) and control cells (Ctrli). d Bmi-1 overexpression increases drug resistance in SGC7901 cells (IC50: 0.45 μg/ml in overexpression group vs. 0.13 μg/ml in control group, left panel) and Bmi-1 knockdown decreases drug resistance to EPI in MNK45 cells (IC50: 0.11 μg/ml in siRNA group vs. 0.28 μg/ml in control group, right panel). Cell viability after treatment with increasing doses of EPI for 48 h was determinated with CCK-8. e Bmi-1 overexpression promotes migration potential in SGC7901 cells (left panel), and Bmi-1 knockdown inhibits migration ability in MNK45 cells (right panel). Migration ability of cells was detected by Transwell Assay and then photographed (upper pane) and quantified (lower panel). Error bars in all panels represent the mean ± standard deviation (SD). (*P < 0.05, **P < 0.01 as compared with control)