Figure 2

NDRG2 inhibits cell proliferation and reduces the intracellular glucose levels of breast cancer cells. (A) T-47D, MCF-7, Bcap37, MDA-MB-231 and SK-BR-3 cells were collected for the extraction of proteins and analysed for N-myc downstream-regulated gene 2 (NDRG2) expression by immunoblotting. (B) SK-BR-3 cells with low NDRG2 expression were infected by an adenovirus carrying NDRG2 (Ad-NDRG2) or negative control LacZ (Ad-LacZ), and T-47D cells with high NDRG2 were transfected with small interfering RNA targeting NDRG2 (NDRG2 siRNA) or negative control siRNA (Con siRNA). Thereafter proteins were extracted from these cells and analysed by immunoblotting. β-actin was used as a loading control. Before being cultured in 25 mM high-glucose (H.G.) or 5.5 mM low-glucose (L.G.) medium, SK-BR-3 cells were infected by Ad-NDRG2 (C) and T-47D cells were transfected by NDRG2 siRNA (D). Cell proliferation was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay for 1 to 5 days. (C) and (D) The data presented are means ± SD for three independent experiments; error bars represent SD from 8 replicative wells. (C) *P < 0.05 and **P < 0.01 versus H.G. Ad-LacZ. ^#P < 0.05 versus L.G. Ad-LacZ. (D) *P < 0.05 versus H.G. Con siRNA. (E) and (F) SK-BR-3 cells were cultured to glucose medium at concentrations of 0, 5, 25, 50 and 100 mM for 24 hours, and then the protein or mRNA was extracted for analysis by immunoblotting (E) or real-time PCR (F). β-actin was used as a loading control. The data presented are means ± SD; error bars represented SD from 3 replicative wells. *P < 0.05 and **P < 0.01 versus control group. (G) SK-BR-3 or (H) T-47D cells, respectively, were infected with Ad-NDRG2 or transfected NDRG2 siRNA and cultured in a high-glucose medium (25 mM) for 48 hours. Next, cell glucose concentrations were measured. (G) and (H) The data presented are means ± SD of three independent experiments; error bars represent SD from 8 replicative wells. *P < 0.05 and **P < 0.01 versus control group.