Loss of contact inhibition of locomotion in the absence of JAM-A promotes entotic cell engulfment.

Entosis is a cell competition process during which tumor cells engulf other tumor cells. It is initiated by metabolic stress or by loss of matrix adhesion, and it provides the winning cell with resources derived from the internalized cell. Using micropatterns as substrates for single cell migration, we find that the depletion of the cell adhesion receptor JAM-A strongly increases the rate of entosis in matrix-adherent cells. The activity of JAM-A in suppressing entosis depends on phosphorylation at Tyr280, which is a binding site for C-terminal Src kinase, and which we have previously found to regulate tumor cell motility and contact inhibition of locomotion (CIL). Loss of JAM-A triggers entosis in matrix-adherent cells but not matrix-deprived cells. Our findings strongly suggest that the increased motility and the perturbed CIL response after the depletion of JAM-A promote entotic cell engulfment, and they link a dysregulation of CIL to entosis in breast cancer cells.