Abstract LB-239: The Rho GEF, GEF-H1, is regulated by and activates Rho in response to 3-D collagen matrix density in breast epithelial cells

Abstract

Abstract Cell interactions with the extracellular matrix (ECM) have a profound influence on carcinoma progression, invasion, and metastasis. We and others have established that breast epithelial cells sense and respond to the stiffness of their ECM environment using the small GTPase Rho, however the exact signaling mechanism has not been identified. In addition to Rho, focal adhesion kinase (FAK) has been linked to mechanosensing, and studies from our lab have revealed FAK as a key mediator of breast tumor progression. We have found that mammary specific deletion of FAK results in tumors that are neither locally invasive nor metastatic. Expression analysis from FAK−/− tumors demonstrated that a number of Rho regulatory molecules were regulated by FAK. Of particular interest, mRNA for the Rho GEF, GEF-H1, was significantly decreased in FAK−/− mammary tumors. While relatively little is known about GEF-H1, it has been implicated in the crosstalk between microtubules and the actin cytoskeleton, positioning it as a potential regulator of Rho-mediated contractility. While it is established that Rho activity is regulated by matrix stiffness, Rho regulatory molecules that modulate signaling in 3D matrices, and specifically in response to changes in matrix stiffness, have yet to be identified. Here we demonstrate that the Rho specific exchange factor, GEF-H1, is activated by and in turn regulates Rho activation as well as Rho-mediated contractility in breast epithelial cells in response to 3D matrix density. Because we have demonstrated that extracellular signal-regulated kinase (ERK) is activated in response to increased 3D collagen matrix density, and others have shown that ERK signaling modulates GEF-H1 exchange activity for RhoA, we are investigating whether ERK mediates mechanosignaling to GEF-H1. Additional studies are underway to determine the role of GEF-H1 in 3D breast cell invasion. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-239.