title: Constitutively activating mutations of c-kit receptor tyrosine kinase confer factor-independent growth and tumorigenicity of factor-dependent hematopoietic cell lines.
abstract: The c-kit receptor tyrosine kinase (KIT) is activated upon ligand binding, thereby leading to a variety of signaling events that play a fundamental role in hematopoiesis. In addition to ligand-dependent activation, we have previously shown that KIT is constitutively activated in a ligand-independent manner by two point mutations, Val-559-->Gly (G559) mutation in the juxtamembrane domain and Asp-814-->Val (V814) mutation in the phosphotransferase domain. To investigate the biochemical consequence and biologic significance of these mutations, retroviral vectors encoding KITG559 or KITV814 were introduced into murine pro-B-type Ba/F3 cells and myeloid FDC-P1 cells, both of which require interleukin-3 (IL-3) for their growth and survival. In the cells, KITG559 or KITV814 were found to be constitutively phophorylated on tyrosine in the absence of stem cell factor (SCF) that is a ligand for KIT. Chemical cross-linking analysis showed that a substantial fraction of the phosphorylated KITG559 underwent dimerization even in the absence of SCF, whereas the phosphorylated KITV814 did not, suggesting the distinct mechanisms underlying constitutive activation of KIT by G559 and V814 mutations. Furthermore, the cells expressing either KITG559 or KITV814 were found to show a factor-independent growth, whereas the cells expressing wild-type KIT (KITWT) proliferated in response to SCF as well as IL-3. Moreover, subcutaneous injection of Ba/F3 cells expressing KITG559 or KITV814 into nude mice resulted in production of large tumors at all sites of the injection within 2 weeks, and all nude mice quickly succumbed to leukemia and died. These results suggest that, although the mechanisms underlying constitutive activation of KITG559 or KITV814 may be different, both of the activating mutations have a function to induce a factor-independent and tumorigenic phenotype. Also, the data of this study raise the possibility that the constitutively activating mutations of c-kit may play a causal role in development of hematologic malignancies.
authors.affiliation: Second Department of Internal Medicine, Osaka University Medical School, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kitayama
authors.forename: Y
authors.initials: Y
authors.lastname: Kanakura
authors.forename: T
authors.initials: T
authors.lastname: Furitsu
authors.forename: T
authors.initials: T
authors.lastname: Tsujimura
authors.forename: K
authors.initials: K
authors.lastname: Oritani
authors.forename: H
authors.initials: H
authors.lastname: Ikeda
authors.forename: H
authors.initials: H
authors.lastname: Sugahara
authors.forename: H
authors.initials: H
authors.lastname: Mitsui
authors.forename: Y
authors.initials: Y
authors.lastname: Kanayama
authors.forename: Y
authors.initials: Y
authors.lastname: Kitamura
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001224:Aspartic Acid; D002455:Cell Division; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D017690:Cell Transplantation; D005260:Female; D006801:Humans; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D019009:Proto-Oncogene Proteins c-kit; D011519:Proto-Oncogenes; D020794:Receptor Protein-Tyrosine Kinases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D016184:Receptors, Colony-Stimulating Factor / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014633:Valine
chemical_list: D011518:Proto-Oncogene Proteins; D016184:Receptors, Colony-Stimulating Factor; D001224:Aspartic Acid; D019009:Proto-Oncogene Proteins c-kit; D020794:Receptor Protein-Tyrosine Kinases; D014633:Valine