title: Insulin-like growth factor II is involved in the proliferation control of medulloblastoma and its cerebellar precursor cells.
abstract: Medulloblastomas (MBs), the most frequent malignant brain tumors of childhood, presumably originate from cerebellar neural precursor cells. An essential fetal mitogen involved in the pathogenesis of different embryonal tumors is insulin-like growth factor II (IGF-II). We screened human MB biopsies of the classic (CMB) and desmoplastic (DMB) variants for IGF2 transcripts of the four IGF2 promoters. We found IGF2 transcription from the imprinted promoter P3 to be significantly increased in the desmoplastic variant compared to the classic subgroup. This was not a result of loss of imprinting of IGF2 in desmoplastic tumors. We next examined the interaction of IGF-II and Sonic hedgehog (Shh), which serves as a critical mitogen for cerebellar granule cell precursors (GCPs) in the external granule cell layer from which DMBs are believed to originate. Mutations of genes encoding components of the Shh-Patched signaling pathway occur in approximately 50% of DMBs. To analyze the effects of IGF-II on Hedgehog signaling, we cultured murine GCP and human MB cells in the presence of Shh and Igf-II. In GCPs, a synergistic effect of Shh and Igf-II on proliferation and gli1 and cyclin D1 mRNA expression was found. Igf-II, but not Shh, induced phosphorylation of Akt and its downstream target Gsk-3beta. In six of nine human MB cell lines IGF-II displayed a growth-promoting effect that was mediated mainly through the IGF-I receptor. Together, our data point to an important role of IGF-II for the proliferation control of both cerebellar neural precursors and MB cells.
authors.affiliation: Department of Neuropathology, University of Bonn Medical Center, Sigmund-Freud-St. 25, D-53105 Bonn, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Hartmann
authors.forename: Arend
authors.initials: A
authors.lastname: Koch
authors.forename: Hendrik
authors.initials: H
authors.lastname: Brune
authors.forename: Anke
authors.initials: A
authors.lastname: Waha
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schüller
authors.forename: Indra
authors.initials: I
authors.lastname: Dani
authors.forename: Dorota
authors.initials: D
authors.lastname: Denkhaus
authors.forename: Wilhelma
authors.initials: W
authors.lastname: Langmann
authors.forename: Udo
authors.initials: U
authors.lastname: Bode
authors.forename: Otmar D
authors.initials: OD
authors.lastname: Wiestler
authors.forename: Karl
authors.initials: K
authors.lastname: Schilling
authors.forename: Torsten
authors.initials: T
authors.lastname: Pietsch
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000254:growth & development; D049109:Cell Proliferation; D002478:Cells, Cultured; D002528:Cerebellar Neoplasms / Q000378:metabolism* / Q000503:physiopathology; D017931:DNA Primers; D005333:Fetus; D053823:Hedgehog Proteins; D006801:Humans; D008527:Medulloblastoma / Q000378:metabolism* / Q000503:physiopathology; D051379:Mice; D009474:Neurons / Q000166:cytology; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis; D011972:Receptor, Insulin / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013002:Somatomedins / Q000378:metabolism* / Q000494:pharmacology; D013234:Stem Cells / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D017931:DNA Primers; D053823:Hedgehog Proteins; D012333:RNA, Messenger; C509239:SHH protein, human; D013002:Somatomedins; D015534:Trans-Activators; D011972:Receptor, Insulin