Epithelial cells make up one of the four basic types of tissues found in animals. In addition to forming the skin that covers our body, epithelial cells can be found surrounding organs and glands. They serve a variety of functions that include protection, secretion, and absorption. Cell turnover refers to the process by which older cells are replaced by younger ones. This generally occurs through the death of older cells by apoptosis and birth of younger cells by stem cell differentiation. Because epithelial cells are readily exposed to the external environment, it’s understandable that they would undergo a high turnover rate. The maintenance of a steady turnover rate is important for ensuring that a constant number of epithelial cells remain. If there are too few, the protective barrier is broken and results in higher risks of infection and inflammation. If there are too many, the excessive number of cells can result in cancer.
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Since carcinomas are the most common type of cancer, understanding the mechanisms controlling epithelial cell turnover may uncover novel targets for cancer treatment. Recently, researchers from the Huntsman Cancer Institute have shown that mechanical tension is one factor that controls epithelial cell death and division. They identified a specific protein, Piezo1, that translates the cellular tension felt into biological effects. Specifically, when epithelial cells are crowded, the tension that results causes Piezo1 to activate extrusion pathways, which essentially squeeze the extra cells out of the epithelial sheet for death by apoptosis. On the other hand, when epithelial cells are lacking in number, the tension results in stretching of the cells, which causes Piezo1 to stimulate cell division through the upregulation of cyclin B, a key player in promoting mitosis, the cell division process that leads to tissue growth.
The results of this study suggest that Piezo1 may be a potential target for manipulating epithelial cell numbers. Current carcinoma treatments involve invasive techniques like surgery, but this treatment could be avoided entirely if Piezo1 ends up being a druggable target. Confirming its druggability may be difficult, but the idea that such regulators exist is promising in terms of discovering new cancer therapeutics.