Matriptase expression in the normal and neoplastic mast cells.

Matriptase, a type II transmembrane serine protease, is distributed in almost all normal human epithelium. Several studies have demonstrated that matriptase expression is correlated with tumor progression in epithelium-derived cancer cells. Mast cells, which originate from pluripotent hematopoietic cells in the bone marrow, can produce and store almost cellular-specific neutral serine proteases, such as tryptase and chymase, and are functionally involved in both the immediate hypersensitivity response and anaphylactic shock. Mast cells are significantly increased in several neoplasms, indicating that they most likely play a role in degrading the tissue matrix. Recently, trypsin has been revealed to activate the latent matriptase on the surface of several human cancer cell lines, suggesting that matriptase and trypsin cooperatively function in extracellular proteolysis. In our study, almost all mast cells in tissues throughout the body stained positive for matripase. Matripase was also found in neoplastic mast cells. To our knowledge, this is the first time that matriptase has been shown to be expressed by mast cells. Therefore, we suggest that this expression of matriptase may not only be useful as an additional marker for mast cells but also be involved in their physiopathological function.