Transcriptional upregulation of c-MET is associated with invasion and tumor budding in colorectal cancer

// Conor A. Bradley 1, * , Philip D. Dunne 1, * , Victoria Bingham 1 , Stephen McQuaid 1, 2 , Hajrah Khawaja 1 , Stephanie Craig 1 , Jackie James 1, 2 , Wendy L. Moore 1 , Darragh G. McArt 1 , Mark Lawler 1 , Sonali Dasgupta 1 , Patrick G. Johnston 1 , Sandra Van Schaeybroeck 1 1 Drug Resistance Group, Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Science, Queen’s University Belfast, Belfast, UK 2 Tissue Pathology, Belfast Health and Social Care Trust, Belfast City Hospital, Belfast, UK * Joint first authors Correspondence to: Sandra Van Schaeybroeck, email: s.vanschaeybroeck@qub.ac.uk Keywords: c-MET, colorectal cancer (CRC), tumor budding, invasion, metastasis Received: July 06, 2016 Accepted: October 19, 2016 Published: October 26, 2016 ABSTRACT c-MET and its ligand HGF are frequently overexpressed in colorectal cancer (CRC) and increased c-MET levels are found in CRC liver metastases. This study investigated the role of the HGF/c-MET axis in regulating migration/invasion in CRC, using pre-clinical models and clinical samples. Pre-clinically, we found marked upregulation of c-MET at both protein and mRNA levels in several invasive CRC cells. Down-regulation of c-MET using RNAi suppressed migration/invasion of parental and invasive CRC cells. Stimulation of CRC cells with rh-HGF or co-culture with HGF-expressing colonic myofibroblasts, resulted in significant increases in their migratory/invasive capacity. Importantly, HGF-induced c-MET activation promoted rapid downregulation of c-MET protein levels, while the MET transcript remained unaltered. Using RNA in situ hybridization (RNA ISH), we further showed that MET mRNA, but not protein levels, were significantly upregulated in tumor budding foci at the invasive front of a cohort of stage III CRC tumors ( p < 0.001). Taken together, we show for the first time that transcriptional upregulation of MET is a key molecular event associated with CRC invasion and tumor budding. This data also indicates that RNA ISH, but not immunohistochemistry, provides a robust methodology to assess MET levels as a potential driving force of CRC tumor invasion and metastasis.