Mechanisms controlling extrusion Apoptotic stimuli through caspases and mechanosensing of a crowded state through Piezo determine whether a cell is going to extrude or not. A cell fated to extrude signals to its neighbors, via a lipid called sphingosine-1-phosphate (S1P). S1P binds its cognate receptor S1P2 on surrounding cells, inducing the formation of an actomyosin cable basolaterally to squeeze the extruding cell up and out of the epithelium. What might happen if extrusion is dysregulated? Too much extrusion or defects in the extrusion pathway may lead to inflammatory disease. On the other hand, cancer cells may lose the ability to apically extrude and be forced to go basally, leading to invasion.