title: RAF expression in human astrocytic tumors.
abstract: RAF proteins are well known oncoproteins. The B-RAF has been shown to be activated by mutations in a multitude of human cancers. Alterations of C-RAF expression are discussed to play a role in lung cancer. Only for A-RAF no link to tumorigenesis has been published so far. Malignant gliomas are the most prevalent primary brain tumors of adults. They are highly invasive and very difficult to treat, despite of surgery, gamma-irradiation and chemotherapy. Although a role of the mitogenic Ras-RAF-MEK-ERK signalling cascade in brain tumor development is well established, there are only few reports available addressing alterations in RAF sequence or protein expression and function in human gliomas. We analysed the mutational status of A-RAF and B-RAF in human glioblastomas (GBM) by sequencing. Then we checked for RAF gene amplification by dot blot hybridization and examined RAF mRNA and protein expression patterns in human astrocytic gliomas of WHO grade II (LGA) and IV (GBM) by semiquantitative RT-PCR and Western blotting, respectively. The results were correlated with patients prognosis. Finally, we performed functional assays to address a putative function of A-RAF in glioma cell proliferation and migration. We showed that RAF mutations are a rare event in glioblastoma multiforme. A-raf gene amplification was more often detected and overexpression of all three RAF proteins on mRNA and protein level was regularly found in human malignant gliomas. Whereas A-RAF and C-RAF expression was negatively correlated with the patients prognosis, B-RAF expression had a positive effect. Since neither A-RAF, nor C-RAF expression had any influence on proliferation and migration of GBM cells, putative functions of C-RAF in angiogenesis and of A-RAF in regulation of metabolism are discussed. Our data indicate that RAF proteins might be valuable targets for small molecule therapies. However, initially specific functions of RAF during tumorigenesis have to be elucidated.
authors.affiliation: Department of Neurosurgery, Tumorbiology Laboratory, University of Würzburg, D-97080 Würzburg, Germany. hagemann_c@klinik.uni-wuerzburg.de
authors.forename: Carsten
authors.initials: C
authors.lastname: Hagemann
authors.forename: Jens
authors.initials: J
authors.lastname: Gloger
authors.forename: Jelena
authors.initials: J
authors.lastname: Anacker
authors.forename: Harun M
authors.initials: HM
authors.lastname: Said
authors.forename: Stefanie
authors.initials: S
authors.lastname: Gerngras
authors.forename: Siglinde
authors.initials: S
authors.lastname: Kühnel
authors.forename: Christoph
authors.initials: C
authors.lastname: Meyer
authors.forename: Ulf Rüdiger
authors.initials: UR
authors.lastname: Rapp
authors.forename: Ulrike
authors.initials: U
authors.lastname: Kämmerer
authors.forename: Dirk
authors.initials: D
authors.lastname: Vordermark
authors.forename: Michael
authors.initials: M
authors.lastname: Flentje
authors.forename: Klaus
authors.initials: K
authors.lastname: Roosen
authors.forename: Giles Hamilton
authors.initials: GH
authors.lastname: Vince
mesh_terms: D001254:Astrocytoma / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D005786:Gene Expression Regulation; D005909:Glioblastoma / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology; D006801:Humans; D050505:Mutant Proteins / Q000235:genetics; D011379:Prognosis; D048491:Proto-Oncogene Proteins A-raf / Q000737:chemistry / Q000235:genetics*; D048493:Proto-Oncogene Proteins B-raf / Q000737:chemistry / Q000235:genetics*; D019908:Proto-Oncogene Proteins c-raf / Q000737:chemistry / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D050505:Mutant Proteins; D012333:RNA, Messenger; D048491:Proto-Oncogene Proteins A-raf; D048493:Proto-Oncogene Proteins B-raf; D019908:Proto-Oncogene Proteins c-raf