title: Inhibiting the phosphatidylinositide 3-kinase pathway blocks radiation-induced metastasis associated with Rho-GTPase and Hypoxia-inducible factor-1 activity.
abstract: OBJECTIVE
  Undifferentiated follicular and anaplastic thyroid tumours often respond poorly to radiotherapy and show increased metastatic potential. We evaluated radiation-induced effects on metastasis in thyroid carcinoma cells and tumours, mechanistically focusing on phosphatidylinositide 3-kinase (PI3K) and associated pathways.
  
  
  METHODS
  Migration was analysed in follicular (FTC133) and anaplastic (8505c) cells following radiotherapy (0-6 Gray) with concomitant pharmacological (GDC-0941) or genetic inhibition of PI3K. Hypoxia-inducible factor-1 (HIF-1)-activity was measured using luciferase reporter assays and was inhibited using a dominant-negative variant. Activation and subcellular localisation of target proteins were assessed via Western blot and immunofluorescence. In vivo studies used FTC133 xenografts with metastatic lung dissemination assessed ex vivo.
  
  
  RESULTS
  Radiation induced migration in a HIF-dependent manner in FTC133 cells but decreased migration in 8505c's. Post-radiation HIF-activity correlated with migratory phenotype. PI3K-targeting inhibited migration under basal and irradiated conditions through inhibition of HIF-1α, Rho-GTPase expression/activity and localisation whilst having little effect on src/FAK. In vivo, radiation induced PI3K, HIF, Rho-GTPases and src but only PI3K, HIF and Rho-GTPases were inhibited by GDC-0941. Co-treatment with GDC-0941 and radiation significantly reduced metastatic dissemination versus radiotherapy alone.
  
  
  CONCLUSIONS
  Radiation modifies metastatic characteristics of thyroid carcinoma cells, which can be successfully inhibited by targeting PI3K using GDC-0941 in vitro and in vivo.
authors.affiliation: Hypoxia and Therapeutics Group, Manchester Pharmacy School, University of Manchester, UK.
authors.forename: Natalie
authors.initials: N
authors.lastname: Burrows
authors.forename: Brian
authors.initials: B
authors.lastname: Telfer
authors.forename: Georg
authors.initials: G
authors.lastname: Brabant
authors.forename: Kaye J
authors.initials: KJ
authors.lastname: Williams
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002465:Cell Movement; D005260:Female; D006801:Humans; D051793:Hypoxia-Inducible Factor 1 / Q000502:physiology*; D007191:Indazoles / Q000494:pharmacology; D051379:Mice; D009362:Neoplasm Metastasis / Q000517:prevention & control*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D015398:Signal Transduction / Q000502:physiology*; D013449:Sulfonamides / Q000494:pharmacology; D013964:Thyroid Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D020741:rho GTP-Binding Proteins / Q000502:physiology*
chemical_list: D051793:Hypoxia-Inducible Factor 1; D007191:Indazoles; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D013449:Sulfonamides; D020741:rho GTP-Binding Proteins; C532162:2-(1H-indazol-4-yl)-6-(4-methanesulfonylpiperazin-1-ylmethyl)-4-morpholin-4-ylthieno(3,2-d)pyrimidine
keywords: GDC-0941; HIF-1; Metastasis; PI3K; Radiotherapy; Rho-GTPases