Normal development of hair follicles of the skin results from the carefully regulated balance of differentiation and proliferation through which hair follicles are continually grow and shed. A tight equilibrium between divisions and differentiation fuels the production of the new hair growth. Almost nothing is known about how this happens, and yet the step is a critical one. If there are too few rounds of division, hair growth stops prematurely; if there are too many rounds, tumors can arise. The hair follicle is thought to be the origin of basal cell carcinomas, trichofolliculumas and pilomatricomas. Recent evidence suggests that growth factor signaling pathways through PI3K play a key role in hair follicle proliferation and malignancy. Although canonical signaling through AKT has significant importance in mediating PI3K pathway in many cancers, there a paucity of evidence that disruption of AKT isoforms effects growth and differentiation in the context of hair follicles. Recent reports indicate a more prominent and novel role for the serum- and glucocorticoid-regulated kinases (SGK) in modulating growth factor-stimulated proliferation in hair follicles of the skin. ? ?
