Abstract LB-231: p 190RhoGAP-B is required for rho down-regulation and ductal morphogenesis of breast epithelial cells in compliant collagen gels

Breast epithelial cells cultured in compliant (floating), but not stiff (attached), 3-dimensional collagen gels differentiate into tubules. While the mechanisms of breast ductal morphogenesis are not well understood, we have previously shown that this process requires down-regulation of the small GTPase Rho in compliant collagen gels. In this study we sought to better define the signaling pathways regulating Rho activity when epithelial cells are cultured in compliant vs. stiff 3D collagen gels. Of the known Rho regulators, expression of p190RhoGAP has been detected at the terminal end buds in the mouse mammary gland, suggesting that proper breast development in vivo requires Rho down-regulation through this protein. Therefore, we specifically investigated the role of p190RhoGAP in ductal morphogenesis. We found that shRNA against p190RhoGAP-B, but not p190RhoGAP-A, blocked down-regulation of Rho activity and inhibited tubule formation in T47D cells cultured in compliant 3D collagen gels. Additionally, both Rho and p190RhoGAP-B co-localized with the adherens junction protein, p120-catenin at sites of cell-cell adhesion when cultured in 3D collagen gels. Similar to our results with p190B knockdown, shRNA against p120-catenin resulted in disruption of ductal morphogenesis and disregulation of Rho activity in cells cultured in compliant 3D collagen gels. Interestingly, we found that the association between p190RhoGAP-B and p120-catenin, which has been shown by others to play a role in Rho regulation, increases in compliant vs. stiff collagen gels. Interaction between p190RhoGAP-B is not mediated by Rho, as it does not require the Rho binding domain of p120-catenin. Together these results demonstrate that p190RhoGAP-B is required for Rho regulation and ductal morphogenesis of breast epithelial cells in floating collagen gels through a mechanism that may involve p 120-catenin. 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-231.