Abstract C55: Detachment of epithelial cells is driven by myosin-based contractility and RhoA

Abstract

Abstract Metastasis requires shedding and migration of individual cells from the tumor. In tumors of epithelial origin, cells often maintain strong cell-cell interactions that must be disassembled prior to cell detachment. Remodeling of cell-cell adhesions occurs during epithelial-mesenchymal transition (EMT), a developmental process where individual cells are triggered to detach and migrate to distant sites by developmental signaling programs. It is thought that inappropriate activation of EMT drives metastasis, particularly by allowing detachment and migration of cancer cells. While much is known about migration and invasion, how cell-cell junctions are detached remains poorly understood. Here we sought to examine how changes in adhesion and contractility are coupled to drive detachment of individual epithelial cells during hepatocyte growth factor (HGF)/ scatter factor-induced EMT. We find that HGF signaling actually increases cell-cell adhesion between cells in suspension, suggesting that changes in cell-cell adhesion are not enough to drive epithelial scattering. Instead, cell-substrate adhesion seems to play a bigger role. Cell-substrate adhesion increases upon HGF stimulation and alterations in the pliability of the subtratum alter cells' ability to undergo scattering. Interestingly, scattering is impaired in cells expressing both active and inactive RhoA mutants. While this also indicates a role for important changes in cell-substrate adhesion during cell-cell detachment, RhoA also affects myosin-based contractility. We sought to examine how myosin-based contractility contributes to cell-cell detachment. Inhibition of Rho kinase or myosin II induces the same effect on cells, namely initiation of cell spreading and an inability to rupture cell-cell adhesions in response to HGF treatment. Interestingly, when cell spreading is induced by transient treatment of cells with blebbistatin, blebbistatin washout results in cellular events that closely resemble HGF-induced epithelial scattering. This suggests that global suppression and subsequent induction of myosin II activity may be sufficient to rupture cell-cell adhesions. Such experiments also suggest a role for RhoA, as blebbistatin-induced scattering is not fully completed in cells expressing a dominant-negative RhoA mutant. Taken together, these results suggest that cell-cell detachment is controlled by contractility, with a contribution by RhoA-mediated changes in cell adhesion. Citation Format: Jacob Peter Hoj, Kendra Fullmer, John Davis, David Morrell, MDH Hansen. Detachment of epithelial cells is driven by myosin-based contractility and RhoA. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr C55.