Human
cathepsin L along with
cathepsin S, K, and V are collectively known as
cathepsin L-like
proteases due to their high homology. The overexpression and aberrant activity of each of these
proteases has been implicated in
tumorigenesis. These
proteases contain propeptide domains that can potently inhibit both their cognate
protease and other
proteases within the
cathepsin L-like subfamily. In this investigation, we have produced the
cathepsin S propeptide recombinantly and have shown that it is a potent inhibitor of the peptidolytic, elastinolytic, and gelatinolytic activities of the
cathepsin L-like
proteases. In addition, we show that this
peptide is capable of significantly attenuating
tumor cell invasion in a panel of human
cancer cell lines. Furthermore, fusion of an
IgG Fc-domain to the COOH terminus of the propeptide resulted in a chimeric
protein with significantly enhanced ability to block
tumor cell invasion. This Fc fusion
protein exhibited enhanced stability in cell-based assays in comparison with the unmodified propeptide species. This approach for the combined inhibition of the
cathepsin L-like
proteases may prove useful for the further study in
cancer and other conditions where their aberrant activity has been implicated. Furthermore, this strategy for simultaneous inhibition of multiple
cysteine cathepsins may represent the basis for novel
therapeutics to attenuate
tumorigenesis.