title: Osteopontin and splice variant expression level in human malignant glioma: radiobiologic effects and prognosis after radiotherapy.
abstract: OBJECTIVE
  We investigated the role of the hypoxia-associated secreted glycoprotein osteopontin (OPN) in the response of malignant glioma to radiotherapy by characterizing OPN and its splice variants in vitro and in patient material.
  
  
  METHODS
  The effect of siRNA knockdown of OPN splice variants on cellular and radiobiologic behavior was analyzed in U251MG cells using OpnS siRNA (inhibition of all OPN splice variants) and OpnAC siRNA (knockdown only of OPNa and OPNc). OPN and splice variant mRNA levels were quantified in archival material of 41 glioblastoma tumor samples. Plasma OPN was prospectively measured in 33 malignant glioma patients.
  
  
  RESULTS
  Inhibition of OPNa and OPNc (OpnAC) reduced clonogenic survival in U251MG cells but did not affect proliferation, migration or apoptosis. Knockdown of all OPN splice variants (OpnS) resulted in an even stronger inhibition of clonogenic survival, while cell proliferation and migration were reduced and rate of apoptosis was increased. Additional irradiation had additive effects with both siRNAs. Plasma OPN increased continuously in malignant glioma patients and was associated with poor survival.
  
  
  CONCLUSIONS
  OPNb is partially able to compensate the effects of OPNa and OPNc knockdown in U251MG cells. High OPN plasma levels at the end of radiotherapy are associated with poor survival.
authors.affiliation: Department of Radiotherapy, Martin Luther University Halle-Wittenberg, Germany. Electronic address: antje.hahnel@uk-halle.de.
authors.forename: Antje
authors.initials: A
authors.lastname: Güttler
authors.forename: Maria
authors.initials: M
authors.lastname: Giebler
authors.forename: Peter
authors.initials: P
authors.lastname: Cuno
authors.forename: Henri
authors.initials: H
authors.lastname: Wichmann
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Keßler
authors.forename: Christian
authors.initials: C
authors.lastname: Ostheimer
authors.forename: Ariane
authors.initials: A
authors.lastname: Söling
authors.forename: Christian
authors.initials: C
authors.lastname: Strauss
authors.forename: Jörg
authors.initials: J
authors.lastname: Illert
authors.forename: Matthias
authors.initials: M
authors.lastname: Kappler
authors.forename: Dirk
authors.initials: D
authors.lastname: Vordermark
authors.forename: Matthias
authors.initials: M
authors.lastname: Bache
mesh_terms: D001932:Brain Neoplasms / Q000737:chemistry / Q000401:mortality / Q000532:radiotherapy*; D045744:Cell Line, Tumor; D005910:Glioma / Q000737:chemistry / Q000401:mortality / Q000532:radiotherapy*; D006801:Humans; D053495:Osteopontin / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D011379:Prognosis; D012333:RNA, Messenger / Q000032:analysis; D034741:RNA, Small Interfering / Q000235:genetics; D011853:Radiobiology
chemical_list: D012333:RNA, Messenger; D034741:RNA, Small Interfering; D053495:Osteopontin
keywords: Gliomas; Osteopontin; Radiation; Splice variants