Effects of PIK3R3 knockdown on cell cycle progression and cell signaling of HGC27 GC cells. (A) The effect of PIK3R3 knockdown on cell cycle progression in HGC27 cells. The cells were cultured in complete medium for 48 h or 24 h followed by another 24 h in serum free medium after siRNA transfection. The cells then were harvested for cell cycle analysis. The data are expressed as means ± S.D. from three independent experiments. The significance was assessed by paired student’s t-test. *P < 0.05 and **P < 0.01 compared with control. (B) Western blot analysis of the effects of PIK3R3 knockdown on cell signaling. Total cell extracts were probed with antibodies to cyclin D1, phospho-Rb (p-Rb), PCNA, phospho-AKT (p-AKT), phospho-mTOR (p-mTOR), PIK3R3, actin (loading control) as indicated.