An EpCAM/Trop2 mechanostat differentially regulates individual and collective migration of human carcinoma cells
EpCAM and its close relative Trop2 are well-known markers of carcinoma, but the potential role of these cell surface proteins in cancer metastasis remains unclear. They are known, however, to downregulate myosin-dependent contractility, a key parameter involved in cell adhesion and migration. We investigate here the morphogenetic impact of the high EpCAM and Trop2 levels typically found in epithelial breast cancer cells, using spheroids of MCF7 cells as an in vitro model. Intriguingly, EpCAM depletion stimulated spheroid cohesive spreading, while Trop2 depletion had the opposite effect. Combining cell biological and biophysical approaches, we demonstrate that while EpCAM and Trop2 both contribute to moderate cell contractility, their depletions differentially impact on the process of "wetting" a substrate, here both matrix and neighboring cells, by affecting the balance of cortical tension at cell and tissue interfaces. These distinct phenotypes can be explained by partial enrichment at specific interfaces. Differential distribution and antagonistic loss-of-function phenotypes are also observed in two other breast cancer cell lines with very different characteristics, suggesting that these are general properties of these two regulators. Our data are consistent with a simple model in which the EpCAM-Trop2 pair acts as a mechanostat that tunes local cortical tension, thus influencing a spectrum of adhesive and migratory behaviours.