| [ Summary ] |
Proteases have been believed to be prerequisite for cancer cell invasion and metastasis. Basic research has confirmed this concept. However, in human cancer tissue, various types of cells express proteases. To overcome this situation, a two-step theory has been proposed ; cancer cells express activators of proforms of proteases, and then, utilize these enzymes for their own invasion, through the extracellular matrix or formation of distant metastasis. The author adds other aspects ; i.e., proteases as host reactions per se. This includes matrix turnover and immune reactions. Proteases have many biological functions and, therefore, we need to cautiously consider their function. |