Simultaneous targeting of CD44 and MMP9 catalytic and hemopexin domains as a therapeutic strategy

Abstract

Crosstalk of the oncogenic matrix metalloproteinase-9 (MMP9) and one of its ligands, CD44, involves cleavage of CD44 by the MMP9 catalytic domain, with the CD44-MMP9 interaction on the cell surface taking place through the MMP9 hemopexin domain (PEX). This interaction promotes cancer cell migration and invasiveness. In concert, MMP9-processed CD44 induces the expression of MMP9, which degrades ECM components and facilitates growth factor release and activation, cancer cell invasiveness, and metastasis. Since both MMP9 and CD44 contribute to cancer progression, we have developed a new strategy to fully block this neoplastic process by engineering a multi-specific inhibitor that simultaneously targets CD44 and both the catalytic and PEX domains of MMP9. Using a yeast surface display technology, we first obtained a high-affinity inhibitor for the MMP9 catalytic domain, which we termed C9, by modifying a natural non-specific MMP inhibitor, N-TIMP2. We then conjugated C9 via a flexible linker to PEX, thereby creating a multi-specific inhibitor (C9-PEX) that simultaneously targets the MMP9 catalytic and PEX domains and CD44. It is likely that, via its co-localization with CD44, C9-PEX may compete with MMP9 localization on the cell surface, thereby inhibiting MMP9 catalytic activity, reducing MMP9 cellular levels, interfering with MMP9 homodimerization, and reducing the activation of downstream MAPK/ERK pathway signaling. The developed platform could be extended to other oncogenic MMPs as well as to other important target proteins, thereby offering great promise for creating novel multi-specific therapeutics for cancer and other diseases.

Keywords: CD44 receptor; hemopexin domain; metalloproteases; multi-specific inhibitor; proteolytic activity; tissue inhibitor of matrix metalloproteinase.