CATHEPSIN-B AND HUMAN TUMOR PROGRESSION

Cathepsin B has been implicated in progression of various human tumors . Overexpression of cathepsin B mRNA, increased cathepsin B staining a nd elevated cathepsin B activity have been found in different human ca ncers. These occur especially at the invasive edges of cancers, sugges ting a role for cathepsin B in tumor invasion. In some tumors, mRNA ex pression and protein staining for cathepsin B correlate with clinical progression. Cathepsin B can facilitate tumor progression directly thr ough degradation of components of the basement membrane and extracellu lar matrix. In vitro studies show that cathepsin B may exert its degra dative effects intracellularly or extracellularly, depending on the ce ll type and location of cathepsin B. Cathepsin B can also facilitate t umor progression indirectly through activation of other latent proteas es and/or degradation of protein inhibitors of other proteases. Thus c athepsin B may be an integral component of the proteolytic cascade lin ked to malignant progression of human tumors.