title: Cell adhesion to fibronectin induces mitomycin C resistance in bladder cancer cells.
abstract: OBJECTIVE
  To investigate whether cell adhesion to fibronectin induces drug resistance in human bladder cancer cells, and to study the survival signalling pathway in cell adhesion to fibronectin-mediated chemotherapy resistance in vitro.
  
  
  METHODS
  T24 cells (human bladder cancer cell lines) were pre-coated with fibronectin, and treated with mitomycin C (MMC) and the specific phosphoinositide-3 kinase (PI3-K) inhibitor LY294002. The apoptosis and cell cycles were analysed. The activity of the caspase-8, -9 and apoptosis-inducing factor (AIF) apoptosis pathways were assessed using colorimetric assay, immunofluorescence, Western blot and flow cytometry. The expression of glycogen synthase kinase-3beta (GSK-3beta) and cyclin D1, as the key regulator of G1/S phase transition, were determined by Western blot. The expression of PI3-K, Akt, phospho-Akt and beta1-integrin were also examined by Western blot.
  
  
  RESULTS
  Apoptosis induced by MMC was significantly resisted by fibronectin adhesion in T24 cells, and this effect was through inhibition of the caspase-9 and AIF apoptosis pathways, but not the caspase-8 pathway. Fibronectin antagonized MMC-induced G0/G1-phase arrest by inactivating GSK-3beta to stabilize cyclin D1 expression in T24 cells. Furthermore, fibronectin-mediated protection of T24 cells was dependent on the activity of the PI3-K/Akt signalling pathway, and the protection could be abolished by the PI3-K inhibitor LY294002.
  
  
  CONCLUSIONS
  Fibronectin-mediated PI3-K/Akt activation protects T24 cells from MMC-induced cell death through inhibition of both caspase-9 and AIF-mediated apoptosis and GSK-3beta/cyclin D1 involved G0/G1-phase arrest.
authors.affiliation: Department of Urology, Rui Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
authors.forename: Chun-Wu
authors.initials: CW
authors.lastname: Pan
authors.forename: Zhou-Jun
authors.initials: ZJ
authors.lastname: Shen
authors.forename: Ting-Ting
authors.initials: TT
authors.lastname: Wu
authors.forename: Xiao-Ying
authors.initials: XY
authors.lastname: Tang
authors.forename: Min
authors.initials: M
authors.lastname: Wang
authors.forename: Jun
authors.initials: J
authors.lastname: Sun
authors.forename: Yuan
authors.initials: Y
authors.lastname: Shao
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000627:therapeutic use*; D017209:Apoptosis; D051033:Apoptosis Inducing Factor / Q000037:antagonists & inhibitors / Q000378:metabolism; D015153:Blotting, Western; D061945:Caspase Inhibitors; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D002867:Chromones / Q000627:therapeutic use; D019008:Drug Resistance, Neoplasm; D004791:Enzyme Inhibitors / Q000627:therapeutic use; D005353:Fibronectins / Q000378:metabolism*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D016685:Mitomycin / Q000627:therapeutic use*; D009025:Morpholines / Q000627:therapeutic use; D001749:Urinary Bladder Neoplasms / Q000188:drug therapy*
chemical_list: D000903:Antibiotics, Antineoplastic; D051033:Apoptosis Inducing Factor; D061945:Caspase Inhibitors; D002867:Chromones; D004791:Enzyme Inhibitors; D005353:Fibronectins; D009025:Morpholines; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D016685:Mitomycin