Cancer Cell Polarity and Extrusion

Cell polarity is the asymmetric localization of key membranes, proteins, and organelles needed for optimal cell function. Polarity is intrinsic to single cells but can also be influenced by external environmental cues, such as neighboring cell contacts in epithelia and the extracellular matrix. Given that most solid tumors arise from epithelia, it may not be surprising that defects in polarity are frequently noted in cancer formation and progression. In this review, we examine how cell polarity, an essential cornerstone of epithelial function, depends on reinforced cell–cell contacts as epithelia reach homeostatic densities and how its dysregulation can contribute to epithelial dysplasia and cancer. As cell extrusion, an essential driver of epithelial apoptosis conserved in all epithelioid tissues, acts as a vital tumor suppressor, we also investigate how this prodeath pathway can be converted into a proinvasive pathway when polarity is misregulated.