Figure 2

Expression and function of matriptase in normal epidermal structures and pathogenic misexpression during squamous cell carcinogenesis. (A) In the epidermis, matriptase (blue) is strictly confined to the transitional cells undergoing terminal differentiation into dead corneocytes (squames) and the first layer of corneocytes, where it regulates the proteolytic release of filaggrin monomers and filaggrin S-100 domain from profilaggrin to facilitate cornified envelope formation and epidermal lipid extrusion. (B) In early anagen and anagen hair follicles, matriptase (blue) is expressed in proliferating hair matrix cells, precortex cells, cortex cells, and the hair shaft, where it promotes hair growth and hair eruption. Expression of matriptase is also observed in sebocytes of the hair follicle sebaceous gland. (C) In multistage epidermal squamous cell carcinogenesis, matriptase (blue) becomes expressed in rapidly proliferating keratin-5-positive basal keratinocytes during the progression of epidermal lesions from hyperplasia to dysplasia, and the protease is widely expressed in the tumor cells of malignant lesions.