IMP3 plays an important role in tumor invasion and metastasis, to which epithelial to mesenchymal transition (EMT) also contributes. The purpose of this study was to investigate whether IMP3 can regulate invasion and metastasis through EMT in breast cancers. The protein expression levels of IMP3 and EMT markers were analyzed by immunohistochemistry in 180 paraffin-embedded human breast tissue samples. There was an inverse correlation of IMP3 with E-cadherin protein expression (P = 0.042). IMP3 expression directly correlated with both Slug (P = 0.004) and vimentin (P < 0.001). Changes in E-cadherin, vimentin, and Slug mRNA and protein levels were examined by quantitative real-time reverse polymerase chain reaction (qRT-PCR) and western blotting. Overexpression of IMP3 reduced the expression of E-cadherin and upregulated Slug and vimentin in transfected cells. In contrast, knocking down IMP3 had the opposite expression of the three proteins. Ribo-immunoprecipitation qPCR revealed that IMP3 binds Slug mRNA directly. In a transwell assay, overexpression of Slug rescued the cell migration and invasion caused by silencing IMP3 in MDA-MB-231 cells. On the other hand, knockdown of Slug in T47D-IMP3 cells could also have the opposite change. Our results strengthen the association of IMP3 with the regulation of EMT. Slug is a functional target of IMP3. IMP3 could therefore promote invasion and migration through the EMT in breast cancer cells.
Keywords: Insulin-like growth factor II (IGF-II) mRNA binding protein 3 (IMP3); breast cancer; epithelial-mesenchymal transition; metastasis; ribo-immunoprecipitation.