Abstract
Epithelial cells contact each other and the extracellular matrix via cell junctions, establishing mechanochemical barriers. During collective delamination, epithelia-derived tumors detach from the tissue with a directionality that dictates their malignancy. How cell junctions contribute to this process and how the directionality of delamination is regulated remains unknown. We used the Drosophila Ras [V12] carcinoma model and found that the loss of septate junctions in epithelial cells triggers apoptosis, whereas in Ras [V12] -cells promotes collective delamination. We found that apical and basal delamination differ in cell identity, polarity, and junctional remodeling, occurring exclusively in squamous and pseudostratified epithelia, respectively. We performed mathematical simulations using a 2D agent-based model and found that tissue architecture and preferential adhesion between mutant cells and with wild-type neighbors regulate the directionality of delamination. Apical delamination initiates with cells constricting apically, emitting apical protrusions, and forming an apical neck via preferential adhesion to collectively detach from the tissue.
