Dissipation monitoring for assessing EGF-induced changes of cell adhesion

Epidermal growth factor (EGF)-induced cell de-adhesion has been implicated as a critical step of normal embryonic development, wound repair, inflammatory response, and tumor cell metastasis. Like many other cellular processes, this cell de-adhesion exhibits a complex, time-dependent pattern. A comprehensive understanding of this process requires a quantitative, real-time assessment of cell-substrate interactions at the molecular level. We employed the quartz crystal microbalance with dissipation monitoring (QCM-D) to successfully track the EGF-induced changes in energy dissipation factor, Delta D, of a monolayer of MCF10A cells in real time. This time-dependent Delta D response correlates well both qualitatively and quantitatively with sequential events of a rapid disassembly, transition, and slow reassembly of focal adhesions of the cells in response to EGF exposure. Based on this strong correlation, we utilized the QCM-D to demonstrate that this dynamic focal-adhesion restructuring is regulated temporally by the downstream pathways of EGFR signaling such as the PI3K, MAPK/ERK, and PLC pathways. Because the QCM-D is a noninvasive technique, this novel approach potentially has a broad range of applications in the fundamental study of cellular processes, such as cell signaling and trafficking and mechanotransduction, and holds promise for drug and biomarker screening. (C) 2012 Elsevier B.V. All rights reserved.