LAUSR

Introduction: In cancer patients, the development of metastases is associated with a poor clinical prognosis. Metastatic dissemination requires cancer cells to detach from the primary tumor and invade adjacent or distant tissue. This process involves epithelial-to-mesenchymal transition (EMT), whereby tumor cells lose cell-cell adhesion mediated by E-cadherin repression. The CD44 family of transmembrane glycoproteins comprises alternatively spliced variants that are involved in many cellular processes. The isoform CD44v6 has been shown to play a major role in tumor growth and metastasis. CD44v6 acts as a co-receptor for the receptor tyrosine kinases (RTKs) c-MET, RON and VEGFR-2, and is preferentially expressed in a variety of epithelial cancers. We have previously shown that the co-receptor function of CD44v6 for c-MET is the driving force for metastasis. c-Met and RON facilitate metastasis through MAPK signaling and VEGFR-2 plays a role in angiogenesis. AMC303, an allosteric and selective peptide inhibitor of CD44v6, prevents phosphorylation of the CD44v6 dependent RTKs and respective cellular processes. Methods: The effect of AMC303 on cancer cell function in response to the growth factors HGF, MSP and VEGF was studied in various assays. Cell migration and invasion was analyzed in scratch assays and the Boyden Chamber. Morphological changes of EMT were monitored using microscopy in scattering assays in the presence of growth factors. EMT markers were analyzed by Western blot and immunohistochemistry. Tube formation was microscopically analyzed. Results: AMC303 dose dependently and at low nanomolar concentrations (IC50 10 - 20nM) prevents HGF- or VEGF-induced activation of c-MET/VEGFR-2 in various cancer cells of pancreatic, lung and colonic origin or endothelial cells, which cannot be overcome by excess HGF and VEGF. HGF- and MSP-dependent cell migration, invasion and wound closure in scratch assays was prevented by AMC303 using different cancer cell lines. AMC303 had a strong inhibitory effect on HGF- and MSP- induced cell scattering, a morphological feature of EMT. Consistent with this, AMC303 inhibited the downregulation of HGF induced EMT markers (E-cadherin). In primary endothelial cells, AMC303 blocked activation of VEGFR-2 and VEGF-A induced formation of a tubular network. Conclusions: Phosphorylation of CD44v6 dependent RTKs is inhibited in primary endothelial cells and different epithelial tumor cells by binding of AMC303 to the extracellular domaine of CD44v6. This novel mode of action results in strong anti-tumor and anti-metastatic effects of AMC303 involving inhibition of migration and invasion of tumor cells and prevention of EMT. AMC303 is currently tested in a First-in-Human Phase I/Ib study in cancer patients with solid epithelial tumors. Citation Format: Thorsten Laufer, Martin Augsten, Vanessa Al-Rawi, Birgit Hotz, Yvonne Heneka, Oliver Coutelle, Alexandra Matzke-Ogi. The allosteric inhibitor of CD44v6 AMC303 blocks c-MET, Ron and VEGFR-2 dependent signaling and cellular processes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3960.