Cell extrusion in development and cancer, what MARCKS the difference for epithelial integrity?

Cell extrusion is an active mechanism to eliminate non-viable or supernumerary cells in healthy epithelia. It also plays a role in carcinogenesis, both in tumor growth (apical extrusion) and metastasis (basal extrusion). Embryonic tissues like the neuroepithelium, on the other hand, present rates of proliferation comparable to that of carcinomas, without the occurrence of cell extrusion. However, the downregulation or phosphorylation of actin modulating proteins like MARCKS, causes extensive neuroepithelial apical cell extrusion. As changes in MARCKS proteins phosphorylation and expression have also been correlated to carcinogenesis, we propose here an integrated model for their functions in epithelial integrity.