Tissue cathepsins as tumor markers.

In the metastatic process, proteolytic enzymes play an important role in mediating passage of the malignant cell through the cell membrane. The cathepsins are ubiquitous lysosomal proteases and are classified both functionally and according to their active site. Cathepsin D, cathepsin B and to a lesser extent other cathepsins have been described as prognostic markers in cancer. Measurements of cathepsin D in breast tissue may be significant in predicting recurrence as well as disease free and overall survival. Reported differences concerning the role of cathepsin D as a prognostic marker may be related in part to the methodology used and the employment in the assays of antibodies prepared to different portions of the molecule. The general consensus is that elevated concentrations of cathepsin D in breast cancer tissue are highly significant indicators of the potential for recurrence. Cathepsin B, which catalyzes the degradation of laminin, may play a role in the rupture of the basement membrane and may be of importance in pancreatic and colorectal cancer.