title: An imbalance between Smad and MAPK pathways is responsible for TGF-beta tumor promoting effects in high-grade gliomas.
abstract: The transforming growth factor-beta (TGF-beta) plays a pivotal role in the pathobiology of human gliomas: during carcinogenesis, it turns from a tumor suppressor to a tumor promoter. The traditional Smad pathway and the more recently discovered MAPK pathway are the most important pathways for TGF-beta related intracellular signal transduction mediating differential pathobiological effects. In this study, we investigated the effects of TGF-beta2 and the TGF-beta2 antisense phosphorothioate oligodeoxynucleotide (PTO) AS-11 on the functionality of both the Smad and MAPK pathways in high-grade gliomas. We aimed to correlate the imbalance between the pathways with differences in the behaviour of high-grade glioma cells. Gene and protein expression studies were used to detect levels of members of the Smad and MAPK pathways under regulation of TGF-beta2 and AS-11. Proliferation and migration assays were functional readouts for effects caused by these regulating tools. Gene arrays were used to detect yet unknown regulators of these functional effects. The Smad pathway was functional in the tested cell lines. Exogenous TGF-beta2 inhibited proliferation but enhanced migration. Smad 2 mRNA expression and activation were significantly reduced by incubation with AS-11. K-ras was reduced both in gene arrays and quPCR under treatment with AS-11, but there was no influence of K-ras down-regulation on the activity of ERK. Ubiquitination-related genes also were specifically down-regulated with AS-11. Our results indicate the involvement of K-ras in TGF-beta signaling in high-grade gliomas. ERK, which is a member of the MAPK pathway, was not influenced and seems to be activated through RAS independent cascades in glioma. These results suggest that combined antagonization of the TGF-beta and MAPK pathways might be a promising approach for glioma therapy. An imbalance between these two pathways might be responsible for TGF-beta switching to a tumor promoter protein in high-grade gliomas.
authors.affiliation: Department of Psychiatry and Psychotherapy, RWTH Aachen University, D-52074 Aachen, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Nickl-Jockschat
authors.forename: F
authors.initials: F
authors.lastname: Arslan
authors.forename: A
authors.initials: A
authors.lastname: Doerfelt
authors.forename: U
authors.initials: U
authors.lastname: Bogdahn
authors.forename: A
authors.initials: A
authors.lastname: Bosserhoff
authors.forename: P
authors.initials: P
authors.lastname: Hau
mesh_terms: D001932:Brain Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D005910:Glioma / Q000378:metabolism*; D006801:Humans; D020935:MAP Kinase Signaling System; D008954:Models, Biological; D009841:Oligonucleotides / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D015398:Signal Transduction; D051785:Smad Proteins / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000096:biosynthesis*; D053781:Transforming Growth Factor beta2 / Q000378:metabolism
chemical_list: D009841:Oligonucleotides; D051785:Smad Proteins; D016212:Transforming Growth Factor beta; D053781:Transforming Growth Factor beta2; D048049:Extracellular Signal-Regulated MAP Kinases