title: Distinct functional roles of Akt isoforms for proliferation, survival, migration and EGF-mediated signalling in lung cancer derived disseminated tumor cells.
abstract: Single disseminated tumor cells (DTC) can be detected in the bone marrow (BM) from 20% to 60% of patients with various tumors including non-small cell lung cancer (NSCLC). Detection of DTC in the BM of NSCLC patients is associated with poor prognosis and may be responsible for metastatic relapse. However, the functional properties of DTC are widely unknown. Here, we performed the first functional analysis of DTC focusing on the activation of the PI3K/Akt signalling pathway and the functional roles of Akt isoforms. In vitro kinase assays revealed a high activity of Akt3 in NSCLC-derived DTC. Proliferation and survival of DTC was reduced by depletion of Akt3 and to a lesser extend by Akt1, but not after depletion of Akt2. The major effect of Akt3 on the proliferation of DTC was associated with an Akt3-mediated regulation of both, cyclin D1 and cyclin D3, whereas Akt1 regulated the expression of cyclin D1 only. In contrast all three Akt isoforms, especially Akt2, were involved in the regulation of migration. Analysis of signalling events downstream of distinct Akt isoforms revealed that expression levels of urokinase-type plasminogen activator and its receptor were decreased after knockdown of Akt1 and Akt3. In addition, EGF-stimulated proliferative and anti-apoptotic signals are mediated by Akt1 and Akt3 in DTC. Finally, by immunofluorescence staining of primary DTC from BM samples of lung cancer patients, pAkt(S473) and Akt3 positive DTC were detected in vivo. Our data demonstrate that Akt1 and notably Akt3 regulate proliferation, survival, migration and EGF-mediated signal transduction in NSCLC-derived DTC.
authors.affiliation: Institute of Biochemistry and Signal Transduction, Center of Experimental Medicine, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Grabinski
authors.forename: Kai
authors.initials: K
authors.lastname: Bartkowiak
authors.forename: Katharina
authors.initials: K
authors.lastname: Grupp
authors.forename: Burkhard
authors.initials: B
authors.lastname: Brandt
authors.forename: Klaus
authors.initials: K
authors.lastname: Pantel
authors.forename: Manfred
authors.initials: M
authors.lastname: Jücker
mesh_terms: D019046:Bone Marrow Neoplasms / Q000378:metabolism / Q000503:physiopathology / Q000556:secondary; D001943:Breast Neoplasms / Q000473:pathology; D002289:Carcinoma, Non-Small-Cell Lung / Q000378:metabolism / Q000503:physiopathology / Q000556:secondary; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D002470:Cell Survival; D057075:Enzyme Assays; D004815:Epidermal Growth Factor / Q000494:pharmacology / Q000502:physiology*; D066246:ErbB Receptors / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D055785:Gene Knockdown Techniques; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D008175:Lung Neoplasms / Q000473:pathology; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D020893:Receptor, ErbB-3 / Q000378:metabolism; D055293:Receptors, Urokinase Plasminogen Activator / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics / Q000378:metabolism
chemical_list: D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D038362:Glycogen Synthase Kinase 3; D007527:Isoenzymes; D051057:Proto-Oncogene Proteins c-akt; D018719:Erb-b2 Receptor Tyrosine Kinases; D020893:Receptor, ErbB-3; D055293:Receptors, Urokinase Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator; C508053:ERBB2 protein, human; C494918:AKT1 protein, human; C494921:AKT2 protein, human; C491754:AKT3 protein, human