title: De novo expression of EphA2 in osteosarcoma modulates activation of the mitogenic signalling pathway.
abstract: OBJECTIVE
  In osteosarcoma patients the development of metastases, often to the lungs, is the most frequent cause of death. The aim of this study was to elucidate the molecular mechanisms governing osteosarcoma development and dissemination and, thereby, to identify possible novel drug targets for improved treatment.
  
  
  RESULTS
  Osteosarcoma samples were characterized using genome-wide microarrays: increased expression of the EphA2 receptor and its ligand EFNA1 was detected. In addition, increased expression of EFNB1, EFNB3 and EphA3 was suggested. Immunohistochemistry revealed an absence of EphA2 in normal bone, and de novo expression in osteosarcomas. EFNA1 was expressed in normal bone, but was significantly elevated in tumours. Further in vitro investigations on the functional role of EphA2 and EFNA1 showed that EFNA1 ligand binding induced increased tyrosine phosphorylation, receptor degradation and downstream mitogen-activated protein kinase (MAPK) activation. Interference with the MAPK pathway unravelled a potential autoregulatory loop governing mainly EFNA1 expression via the same pathway.
  
  
  CONCLUSIONS
  Upregulation and de novo expression of ephrins in osteosarcomas are involved in oncogenic signalling and thus might stimulate osteosarcoma metastasis.
authors.affiliation: Institute of Pathology, Charitè Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Raphaela
authors.initials: R
authors.lastname: Fritsche-Guenther
authors.forename: Aurelia
authors.initials: A
authors.lastname: Noske
authors.forename: Ute
authors.initials: U
authors.lastname: Ungethüm
authors.forename: Ralf-Jürgen
authors.initials: RJ
authors.lastname: Kuban
authors.forename: Peter M
authors.initials: PM
authors.lastname: Schlag
authors.forename: Per-Ulf
authors.initials: PU
authors.lastname: Tunn
authors.forename: Janine
authors.initials: J
authors.lastname: Karle
authors.forename: Veit
authors.initials: V
authors.lastname: Krenn
authors.forename: Manfred
authors.initials: M
authors.lastname: Dietel
authors.forename: Christine
authors.initials: C
authors.lastname: Sers
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015153:Blotting, Western; D001859:Bone Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002648:Child; D036382:Ephrin-A1 / Q000235:genetics / Q000378:metabolism; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D012516:Osteosarcoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D036104:Receptor, EphA2 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D015854:Up-Regulation
chemical_list: D036382:Ephrin-A1; D036104:Receptor, EphA2; D020928:Mitogen-Activated Protein Kinases