By inhibiting Ras/Raf/ERK and MMP-9, knockdown of EpCAM inhibits breast cancer cell growth and metastasis.

Epithelial cell adhesion molecule (EpCAM) is a type I transmembrane protein that is expressed in the majority of normal epithelial tissues and is overexpressed in most epithelial cancers including breast cancer, where it plays an important role in cancer progression. However, the mechanism by which EpCAM promotes the progression of breast cancer is not understood. In this study, we found that EpCAM expression was increased in tumor tissue from breast cancer patients compared to healthy patients. Overexpression of EpCAM in breast cancer cells enhanced tumor cell growth in vitro and increased invasiveness, whereas small interfering RNA-mediated silencing of EpCAM (si-EpCAM) had the opposite effect. EpCAM knockdown led to decreased phosphorylation of Raf and ERK, suppression of malignant behavior of breast cancer cells, and inhibition of the Ras/Raf/ERK signaling pathway. Furthermore, si-EpCAM-mediated invasion and metastasis of breast carcinoma cells required the downregulation of matrix metalloproteinase-9 (MMP-9) through inhibition of this signaling pathway. In conclusion, our data show that knockdown of EpCAM can inhibition breast cancer cell growth and metastasis via inhibition of the Ras/Raf/ERK signaling pathway and MMP-9.