This interaction induced autonomous acquisition of chemoresistance. The presence of stromal cells within patient’s tumour might be predictive of chemoresistance. The specific interaction between cancer cells and stromal cells might be targeted during chemotherapy. Poster No. 89 Extracellular Matrix Regulation of EGRR Activity: Hyaluronan Alters Epidermal Growth Factor Receptor-Dependent Cell Morphology Jeanne Louderbough

1 , Joyce Schroeder1 1 Department of Molecular & Cellular Biology, University of Arizona, Tucson, AZ, USA EGFR is an important regulator of breast cancer progression and is capable of integrating multireceptor signaling pathways to promote metastasis. Through these interactions, CP673451 chemical structure EGFR is subject to extensive regulatory cues from the extracellular matrix (ECM), of which the extracellular glycoprotein hyaluronan (HA) is a major component. In mammary tumors, HA is deposited in the stromal compartment surrounding tumor epithelium where it functions in both biomechanical support and, through binding check details to the adhesion receptor CD44, modulates intracellular

signaling. We have used a 3D AZD2281 concentration collagen culture system in which HA is either polymerized into a collagen matrix to mimic epithelial-stromal interactions or provided soluble in the media (sHA). We have found that collagen-embedded HA (eHA) inhibits EGFR activation and alters cell morphology by inhibiting filopodia formation while soluble HA promotes these events. The ability of cells to spread on a collagen matrix is also impaired on eHA, demonstrating a novel function for eHA in regulating

cell morphology and membrane dynamics. Inhibition of EGFR and alterations to cell morphology are due to cell-matrix interactions, as collagen polymerization is unaltered by eHA. EGFR interaction with the HA receptor, CD44, is impaired on eHA suggesting that this is a mechanism by which HA regulates EGFR activity. Furthermore, given the ability of EGFR to alter cell morphology on a matrix, we have examined the ability of erbB ligands to regulate cell morphology on diverse matrix substrates and have found that these ligands induce collagen-dependent changes indicative of EMT. These findings highlight a novel role for eHA as a protective molecule when encountered in the collagen matrix MG-132 nmr during cancer progression, while reinforcing the tumor promoting effects of sHA, and demonstrate the ability of the ECM to alter erbB-dependent EMT. Poster No. 90 Regulation of Invadopodia Formation by Hypoxia-Induced NHE-1 Activity Fabrice Lucien 1 , Dominique Arsenault1, Claire M. Dubois1 1 Immunology Division, University of Sherbrooke, Sherbrooke, QC, Canada Most tumors are characterized by an acidic and hypoxic microenvironment that promotes metastasis. The Na+/H+ exchanger (NHE-1) plays an important role in the regulation of pH homeostasis. It has been demonstrated that NHE-1 is constitutively active in tumor cells, promoting cell invasion, but the mechanisms are not defined.