Signaling through ShcA is required for TGF- and Neu/ErbB-2 induced breast cancer cell motility and invasion

Departments of, Biochemistry, Medicine and Anatomy and Cell Biology, McGill University, Montréal, Québec, Canada

^* To whom correspondence should be addressed. Email: peter.siegel{at}mcgill.ca.

	Abstract

Cooperation between the Neu/ErbB-2 and TGF- signaling pathways enhances the invasive and metastatic capabilities of breast cancer cells; however, the underlying mechanisms mediating this synergy have yet to be fully explained. We demonstrate that TGF- induces migration and invasion of mammary tumor explants expressing an activated Neu/ErbB-2 receptor, which requires signaling from autophosphorylation sites located in the C-terminus. Systematic analysis of mammary tumor explants expressing Neu/ErbB-2 add-back receptors that couple to distinct signaling molecules, has mapped the synergistic effect of TGF- induced motility and invasion to signals emanating from tyrosine residues 1226/1227 and 1253 of Neu/ErbB-2. Given that the ShcA adaptor protein is known to interact with Neu/ErbB-2 through these residues, we investigated the importance of this signaling molecule in TGF- induced cell motility and invasion. Reduction of ShcA expression rendered cells expressing activated Neu/ErbB-2, or add-back receptors signaling specifically through tyrosines 1226/1227 or 1253, unresponsive to TGF- induced motility and invasion. In addition, a dominant negative form of ShcA, lacking its three known tyrosine phosphorylation sites, completely abrogates TGF- induced migration and invasion of breast cancer cells expressing activated Neu/ErbB-2. Our results implicate signaling through the ShcA adaptor as a key component in the synergistic interaction between these pathways.