title: Radiation-induced myosin IIA expression stimulates collagen type I matrix reorganization.
abstract: OBJECTIVE
  Extracellular matrix (ECM) reorganization critically contributes to breast cancer (BC) progression and radiotherapy response. We investigated the molecular background and functional consequences of collagen type I (col-I) reorganization by irradiated breast cancer cells (BCC).
  
  
  METHODS
  Radiation-induced (RI) col-I reorganization was evaluated for MCF-7/6, MCF-7/AZ, T47D and SK-BR-3 BCC. Phase-contrast microscopy and a stressed matrix contraction assay were used for visualization and quantification of col-I reorganization. Cell-matrix interactions were assessed by the inhibition of β1 integrin (neutralizing antibody 'P5D2') or focal adhesion kinase (FAK; GSK22560098 small molecule kinase inhibitor). The role of the actomyosin cytoskeleton was explored by western blotting analysis of myosin II expression and activity; and by gene silencing of myosin IIA and pharmacological inhibition of the actomyosin system (blebbistatin, cytochalasin D). BCC death was evaluated by propidium iodide staining.
  
  
  RESULTS
  We observed a radiation dose-dependent increase of col-I reorganization by BCC. β1 Integrin/FAK-mediated cell-matrix interactions are essential for RI col-I reorganization. Irradiated BCC are characterized by increased myosin IIA expression and myosin IIA-dependent col-I reorganization. Moreover, RI col-I reorganization by BCC is associated with decreased BCC death, as suggested by pharmacological targeting of the β1 integrin/FAK/myosin IIA pathway.
  
  
  CONCLUSIONS
  Our data indicate the role of myosin IIA in col-I reorganization by irradiated BCC and reciprocal BCC death.
authors.affiliation: Department of Radiation Oncology and Experimental Cancer Research, Ghent University Hospital, Belgium. stephanie.blockhuys@ugent.be
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Blockhuys
authors.forename: Bart
authors.initials: B
authors.lastname: Van Rompaye
authors.forename: Riet
authors.initials: R
authors.lastname: De Rycke
authors.forename: Kathleen
authors.initials: K
authors.lastname: Lambein
authors.forename: Kathleen
authors.initials: K
authors.lastname: Claes
authors.forename: Marc
authors.initials: M
authors.lastname: Bracke
authors.forename: Carlos
authors.initials: C
authors.lastname: De Wagter
authors.forename: Olivier
authors.initials: O
authors.lastname: De Wever
mesh_terms: D000205:Actomyosin / Q000502:physiology; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D024042:Collagen Type I / Q000737:chemistry*; D005260:Female; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000502:physiology; D006801:Humans; D019012:Integrin beta1 / Q000502:physiology; D061986:MCF-7 Cells; D024507:Nonmuscle Myosin Type IIA / Q000502:physiology*
chemical_list: D024042:Collagen Type I; D019012:Integrin beta1; D000205:Actomyosin; D051416:Focal Adhesion Protein-Tyrosine Kinases; D024507:Nonmuscle Myosin Type IIA
keywords: Actomyosin; Breast cancer; Cell–matrix interactions; Collagen; ECM remodeling; Ionizing radiation