title: beta1-integrin-mediated signaling essentially contributes to cell survival after radiation-induced genotoxic injury.
abstract: Integrin-mediated adhesion to extracellular matrix proteins confers resistance to radiation- or drug-induced genotoxic injury. To analyse the underlying mechanisms specific for beta1-integrins, wild-type beta1A-integrin-expressing GD25beta1A cells were compared to GD25beta1B cells, which express signaling-incompetent beta1B variants. Cells grown on fibronectin, collagen-III, beta1-integrin-IgG or poly-l-lysine were exposed to 0-6 Gy X-rays in presence or depletion of growth factors and phosphatidylinositol-3 kinase (PI3K) inhibitors (LY294002, wortmannin). In order to test the relevance of these findings in tumor cells, human A-172 glioma cells were examined under the same conditions after siRNA-mediated silencing of beta1-integrins. We found that beta1A-integrin-mediated adhesion to fibronectin, collagen-III or beta1-IgG was essential for cell survival after radiation-induced genotoxic injury. Mediated by PI3K, pro-survival beta1A-integrin/Akt signaling was critically involved in this process. Additionally, the beta1-integrin downstream targets p130Cas and paxillin-impaired survival-regulating PI3K-dependent JNK. In A-172 glioma cells, beta1-integrin knockdown and PI3K inhibition confirmed the central role of beta1-integrins in Akt- and p130Cas/paxillin-mediated prosurvival signaling. These findings suggest beta1-integrins as critical regulators of cell survival after radiation-induced genotoxic injury. Elucidation of the molecular circuitry of prosurvival beta1-integrin-mediated signaling in tumor cells may promote the development of innovative molecular-targeted therapeutic antitumor strategies.
authors.affiliation: OncoRay -- Radiation Research in Oncology, Medical Faculty Carl Gustav Carus, Technical University Dresden, Fetscherstrasse, Dresden, Germany. Nils.Cordes@mailbox.tu-dresden.de
authors.forename: N
authors.initials: N
authors.lastname: Cordes
authors.forename: J
authors.initials: J
authors.lastname: Seidler
authors.forename: R
authors.initials: R
authors.lastname: Durzok
authors.forename: H
authors.initials: H
authors.lastname: Geinitz
authors.forename: C
authors.initials: C
authors.lastname: Brakebusch
mesh_terms: D000818:Animals; D001932:Brain Neoplasms / Q000473:pathology; D002448:Cell Adhesion; D018929:Cell Culture Techniques; D002470:Cell Survival; D016326:Extracellular Matrix Proteins; D005347:Fibroblasts; D005353:Fibronectins / Q000378:metabolism; D005910:Glioma / Q000473:pathology; D006133:Growth Substances; D006801:Humans; D019012:Integrin beta1 / Q000502:physiology*; D051379:Mice; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology; D034741:RNA, Small Interfering; D011832:Radiation Injuries; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D014965:X-Rays
chemical_list: D016326:Extracellular Matrix Proteins; D005353:Fibronectins; D006133:Growth Substances; D019012:Integrin beta1; D034741:RNA, Small Interfering; D051057:Proto-Oncogene Proteins c-akt