CCAAT enhancer binding protein β has a crucial role in regulating breast cancer cell growth via activating the TGF-β-Smad3 signaling pathway

The aim of the present study was to examine the effect of CCAAT enhancer binding protein beta (C/EBP beta) on human breast cancer cells. The plasmids pCDH-C/EBP beta and pLKO.1-shC/EBP beta were constructed and were infected into MDA-MB-468 cells, to provide C/EBP beta overexpressing and C/EBP beta knockdown cells, respectively. Cell viability, cell cycle and apoptosis were observed by MTT assay and flow cytometry analysis. Protein expression levels of C/EBP beta, TGF-beta 1, P-Smad3 and Smad3 were detected by western blotting. MTT assay showed that the absorbance of MDA-MB-468 cells in the pCDH-C/EBP beta group was increased, whereas that in the pLKO.1-shC/EBP beta group was decreased, compared with the respective control at 48 and 72 h. Flow cytometric analysis indicated that the percentage of cells in the G2 phase was significantly increased in the pCDH-C/EBP beta group (P<0.05) and decreased in the pLKO.1-shC/EBP beta group compared with the respective control group. The proportion of apoptotic cells was decreased in the pCDH-C/EBP beta group and increased in the pLKO.1-shC/EBP beta group compared with the controls. The scratch-wound assay revealed that MDA-MB-468 cells depleted of C/EBP beta exhibited reduced motility compared with the control cells. Moreover, western blotting demonstrated that pCDH-C/EBP beta increased transforming growth factor (TGF)beta 1 and P-Smad3 protein expression and decreased Smad3 protein expression, whereas pLKO.1-shC/EBP beta decreased TGF beta 1 and P-Smad3 protein expression and increased Smad3 protein expression levels. The present study demonstrated that C/EBP beta has a crucial role in regulating breast cancer cell growth through activating TGF-beta-Smad3 signaling. These findings suggest that C/EBP beta may be a potential therapeutic target for breast cancer; however, in vivo studies are required to confirm this.