Eur Arch Otorhinolaryngol (1997) 254 (Suppl. 1):S 138-S 143 9 Springer-Verlag 1997 E. Galeazzi 9 M. Olivero 9 F. C. Gervasio A. De Stefani 9 G. Valente 9 P. M. Comoglio M. F. Di Renzo 9 G. Cortesina Detection of MET oncogene/hepatocyte growth factor receptor in lymph node metastases from head and neck squamous cell carcinomas Abstract The c-MET oncogene encodes the receptor for hepatocyte growth factor/scatter factor (HGF/SF), which is known to stimulate the invasive growth of epithelial cells cultured in vitro. The Met/HGF receptor is a hetero- dimeric transmembrane tyrosine kinase, which is a proto- type for a new family of growth factor receptors. The c- MET oncogene is expressed in several types of epithelial tissue including keratinocytes and is over-expressed in a number of human carcinomas. Studies on various carci- noma cell lines have shown that over-expression and structural alteration of the receptor result in its activation and confer tumorigenesis. We have studied Met/HGF re- ceptor expression in tissue specimens from 34 patients with head and neck squamous cell carcinomas (HNSCC) and in 17 regional lymph node metastases. Western blot analysis was employed, using monoclonal antibodies di- rected against either the intracellular or extracellular do- main of the receptor. Each sample was compared to its normal counterpart. The receptor did not show any major structural alterations in HNSCC tissues, but its expression was increased from 2- to 50-fold in about 70% of tumors. Immunohistochemistry then showed that the same anti- bodies stained only a few cells in the basal layer of normal squamous epithelium but intensely marked tumor cells. In the lymph node metastases of Met-positive tumors, recep- tor expression was maintained and sometimes increased with respect to primary tumors. Immunohistochemical analysis of the metastatic lymph nodes showed that cells E. Galeazzi 9 F. C. Gervasio 9 A. De Stefani - G. Cortesina Department of Clinical Physiopathology, University of Turin School of Medicine, Turin, Italy M. Olivero 9 G. Valente 9 P. M. Comoglio Department of Biomedical Sciences and Oncology, University of Turin School of Medicine, Turin, Italy M. F. Di Renzo Institute of Histology, University of Sassari School of Medicine, Sassari, Italy G. Cortesina (~g:~) Clinica ORL, Via Genova 3, 1-10126 Turin, Italy were negative in the normal lymphatic tissue and strongly stained in tumor cells. Over-expression of the Met/HGF receptor was found at all tumor stages but was more sig- nificant in those associated with enlarged or multiple (N2-N3) lymph node metastases. These data show that expression of the Met/HGF receptor may be involved in the progression of HNSCC towards a metastatic pheno- type and may be a useful marker of head and neck tumor cell spread to regional lymph nodes. Key words Lymph node metastases - MET oncogene 9 Head and neck squamous cell carcinoma 9 Hepatocyte growth factor receptor Introduction The c-MET oncogene [6] encodes a transmembrane tyro- sine kinase, which has now been identified as the receptor for hepatocyte growth factor (HGF) or "scatter factor" (SF) [14]. This receptor (Met/HGF receptor) is an o~ complex of 190 kDa and is composed of an extracellular 50 kDa c~-chain and a 145 kDa ~3-chain [13] that spans the plasma membrane and shows tyrosine kinase activity [20]. These two chains are disulfide-linked. The ligand of the receptor encoded by the MET gene, HGF/SF, has pleiotropic effects on epithelial cells. It is mitogenic and also stimulates cell motility, dissociation of epithelial sheets and invasion of the cellular matrix [26]. The Met/I-IGF receptor plays a significant role in cell physiology during development and tissue regeneration and is expressed in several normal human epithelial tis- sues, including those of the liver, kidney and lung [9, 22]. Activation of the Met/I-IGF receptor kinase leads to un- controlled proliferation of cells. The over-expression of the Met protein is most probably sufficient for the consti- tutive activation of Met kinase with the MET oncogene activated by amplification or structural alterations of the extracellular domain of the receptor. Activation of the c-MET oncogene has been related to tumor cell invasiveness and metastasis on the basis of ex-