Anti-c-Met antibodies recognising a temperature sensitive epitope, inhibit cell growth

// Julin S. Wong 1,2 Emma Warbrick 2 , Borek Vojtesek 3 , Jeffrey Hill 4 and David P. Lane 1 1 p53 Laboratory, 8A Biomedical Grove, Immunos #06-06, Singapore, Singapore. 2 Epithelial Genetics Group, Medical Sciences Institute, College of Life Sciences and Medicine, Dentistry & Nursing, Dundee, Scotland, UK. 3 Regional Centre for Applied Molecular Oncology, Masaryk Memorial Cancer Institute, Brno, Czech Republic. 4 Experimental Therapeutics Centre, 31 Biopolis Way, Nanos Level 3, Singapore. Correspondence: David P. Lane, email: // Keywords : c-Met, seeMet 2, monoclonal antibody, temperature sensitive & cryptic epitope Received : June 4, 2013 Accepted : June 27, 2013 Published : June 29, 2013 Abstract c-Met is a tyrosine receptor kinase which is activated by its ligand, the hepatocyte growth factor. Activation of c-Met leads to a wide spectrum of biological activities such as motility, angiogenesis, morphogenesis, cell survival and cell regeneration. c-Met is abnormally activated in many tumour types. Aberrant c-Met activation was found to induce tumour development, tumour cell migration and invasion, and the worst and final step in cancer progression, metastasis. In addition, c-Met activation in cells was also shown to confer resistance to apoptosis induced by UV damage or chemotherapeutic drugs. This study describes the development of monoclonal antibodies against c-Met as therapeutic molecules in cancer treatment/diagnostics. A panel of c-Met monoclonal antibodies was developed and characterised by epitope mapping, Western blotting, immunoprecipitation, agonist/antagonist effect in cell scatter assays and for their ability to recognise native c-Met by flow cytometry. We refer to these antibodies as Specifically Engaging Extracellular c-Met (seeMet). seeMet 2 and 13 bound strongly to native c-Met in flow cytometry and reduced SNU-5 cell growth. Interestingly, seeMet 2 binding was strongly reduced at 4 o C when compared to 37 o C. Detail mapping of the seeMet 2 epitope indicated a cryptic binding site hidden within the c-Met α-chain.