title: Deletion of the ectodomain unleashes the transforming, invasive, and tumorigenic potential of the MET oncogene.
abstract: The c-MET proto-oncogene, encoding the p190 hepatocyte growth factor tyrosine kinase receptor, can acquire oncogenic potential by multiple mechanisms, such as gene rearrangement, amplification and overexpression, point mutation, and ectopic expression, all resulting in its constitutive activation. Hepatocyte growth factor receptor truncated forms are generated by post-translational cleavage: p140 and p130 lack the kinase domain and are inactive. Their C-terminal remnant fragments are generally undetectable in normal cells, but a membrane-associated truncated form is recognized by anti-C-terminus antibodies in some human tumors, suggesting that a hepatocyte growth factor receptor lacking the ectodomain, but retaining the transmembrane and intracellular domains (Met-EC-), could acquire oncogenic properties. Herein we show that NIH-3T3 cells transduced with MET-EC- expressed a membrane-associated constitutively tyrosine-phosphorylated 60-kDa protein and, similarly to NIH-3T3 cells expressing the cytosolic oncoprotein Tpr-Met, showed activated extracellular regulated kinase 1/2 mitogen-activated protein kinase and Akt downstream transducers. Compared to control NIH-3T3 cells, NIH-3T3-Met-EC- cells grew faster and showed anchorage-independent growth and invasive properties in all aspects similar to cells expressing the transforming TPR-MET. Nude female mice injected subcutaneously with NIH-3T3-Met-EC- cells developed visible tumors, displaying the typical morphology of carcinomas with polygonal cells, in contrast to sarcomas with spindle-shaped cells induced by the injection of NIH-3T3-Tpr-Met cells. It is suggested that the different subcellular localization of the oncoproteins, more than differences in signal transduction, could be responsible for the tumor phenotype. All together, these data show that deletion of the ectodomain activates the hepatocyte growth factor receptor and its downstream signaling pathways, unleashing its transforming, invasive, and tumorigenic potential.
authors.affiliation: Laboratory of Histology, Department of Medical Sciences, Università del Piemonte Orientale A. Avogardro, Novara, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Merlin
authors.forename: Stefano
authors.initials: S
authors.lastname: Pietronave
authors.forename: Deborah
authors.initials: D
authors.lastname: Locarno
authors.forename: Guido
authors.initials: G
authors.lastname: Valente
authors.forename: Antonia
authors.initials: A
authors.lastname: Follenzi
authors.forename: Maria
authors.initials: M
authors.lastname: Prat
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D005260:Female; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007150:Immunohistochemistry; D007633:Keratins / Q000378:metabolism; D016086:Lentivirus / Q000235:genetics; D020935:MAP Kinase Signaling System / Q000235:genetics; D051379:Mice; D008819:Mice, Nude; D041681:NIH 3T3 Cells; D010766:Phosphorylation; D010957:Plasmids; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary / Q000235:genetics; D000090063:Proto-Oncogene Mas; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D019859:Proto-Oncogene Proteins c-met / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D014161:Transduction, Genetic; D014443:Tyrosine / Q000378:metabolism; D014746:Vimentin / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D014746:Vimentin; D049452:Green Fluorescent Proteins; D014443:Tyrosine; D007633:Keratins; D019859:Proto-Oncogene Proteins c-met; D051057:Proto-Oncogene Proteins c-akt