Regulation of keratinocyte function by growth factors.

Various kinds of growth factors are involved in the regulation of human keratinocyte function. Among them, the epidermal growth factor (EGF) family and the transforming growth factor-beta (TGF-beta) family play central roles, providing dual-mode regulation of keratinocyte growth through the proliferation-stimulating effect of EGF and the proliferation-inhibiting effect of TGF-beta. Human keratinocytes synthesize four EGF family growth factors, TGF-alpha, amphiregulin, HB-EGF and epiregulin, which efficiently regulate keratinocyte growth and differentiation via auto- and cross-induction pathways. Human keratinocytes also synthesize TGF-beta1 and TGF-beta2, which are potent inhibitors of human keratinocytes. These intrinsic EGF family growth factors and TGF-betas are responsible for the autonomous growth regulation of keratinocytes.