Overcoming Cetuximab Resistance in Colorectal Cancer through Inhibition of HGF Processing

Abstract

<b>Abstract ID 55700</b> <b>Poster Board 434</b> Cetuximab is a monoclonal antibody against epidermal growth factor receptor (EGFR) and can prolong survival in metastatic colorectal cancer (CRC) patients. However, therapeutic resistance can limit its efficiency and use. Our lab has previously identified that the activation of receptor tyrosine kinases (RTKs) MET and RON contributed to cetuximab resistance. In the absence of activating mutations of MET and RON, the activity of these RTKs depends on the availability of their ligands, hepatocyte growth factor (HGF) and hepatocyte growth factor-like (HGFL), respectively. To become biologically active, the inactive precursors of HGF and HGFL must be processed by serine proteases (HGFA, matriptase, and hepsin). A survey of TCGA datasets indicated that MET and HGF were overexpressed in several CRC CMS subtypes. We found that the addition of recombinant human HGF conferred cetuximab resistance to cetuximab-sensitive cells (CC). A cetuximab-resistant phenotype was also observed in cetuximab-sensitive cells we engineered to overexpress HGF (CC-HGF). Cetuximab resistance induced by HGF addition or overexpression could be overcome by downstream inhibition with crizotinib, a multi-targeted RTK inhibitor. Our next goal was to investigate whether we could target the pathway upstream. Our TCGA analysis did not show any consistent overexpression of the serine proteases. Hepatocyte growth factor activator inhibitor type 1 and 2 (HAI-1/2) are two Kunitz-type serine protease inhibitors. HAI-1 displayed significantly reduced expression in all CMS subtypes in the TCGA datasets. We demonstrated that upstream inhibition by the addition of recombinant human HAI-1 overcomes cetuximab resistance in CC-HGF cells. ZFH7116 is a small molecule inhibitor of the serine proteases that mimics HAI-1 activity. ZFH7116 suppressed HGF cleavage and maturation in our cetuximab-resistant SC and CC-CR cell lines. We observed a cooperative effect of ZFH7116 with cetuximab to reduce SC and CC-CR cell growth in 3D collagen cultures. We are currently investigating if ZFH7116 can overcome cetuximab resistance in CC-HGF. Collectively, our findings suggest that inhibiting HGF cleavage and processing may be a unique strategy for overcoming EGFR-targeted therapy resistance in colorectal cancer.