EMMPRIN (extracellular matrix metalloproteinase inducer, EMN, CD147) is a member of the immunoglobulin superfamily expressed in numerous cell types both as a soluble and a membrane-spanning glycoprotein. It is involved in many physiological processes, as well as in cancer. This study addresses mechanisms of crosstalk between EMN-driven cancer-related cellular responses and the canonical Wnt-pathway in MCF-7 breast carcinoma cells. Genetic knockdown of EMN in MCF-7 resulted in characteristic changes in cellular shape, organization of the actin cytoskeleton and malignancy profile, indicating that EMN expression represses cell motility, but, in contrast, exerts a stimulatory effect on cell proliferation and invasive properties. Increased invasiveness coincided with elevated expression of Wnt-target genes and established invasion driver matrix metalloproteinase MMP14. Activation of the downstream Wnt-pathway by means of heterologous β-catenin and/or TCF-4 expression, through inhibition of GSK-3β by LiCl treatment, or by cell stimulation with insulin-like growth factor-1 (IGF-1) resulted in increased EMN expression. EMN over-expression raised the ratio of the two opposing Wnt pathway-driven transcription factors Sp1 and Sp5, leading to stimulation of the EMN promoter. Furthermore, the EMN promoter was activated by a feed-forward circuit involving an EMN-dependent drop in expression of the repressive signal transducer and activator of transcription 1 (STAT1). Taken together, we show that the influence of EMMPRIN on malignancy-related properties of breast cancer cells is functionally connected to both Wnt- and JAK/STAT pathways.
Keywords: Breast cancer; EMN; Feed-forward regulation; STAT1; Sp5; Wnt pathway.