Redox mechanisms switch on hypoxia-dependent epithelial-mesenchymal transition in cancer cells.
Epithelial-mesenchymal transition (EMT) and hypoxia are considered as crucial events favouring invasion and metastasis of many cancer cells. In this study, different human neoplastic cell lines of epithelial origin were exposed to hypoxic conditions in order to investigate whether hypoxia per se may trigger EMT programme as well as to mechanistically elucidate signal transduction mechanisms involved. The following human cancer cell lines were used: HepG2 (from human hepatoblastoma), PANC-1 (from pancreatic carcinoma), HT-29 (from colon carcinoma) and MCF-7 (from breast carcinoma). Cancer cells were exposed to carefully controlled hypoxic conditions and investigated for EMT changes and signal transduction by using morphological, cell and molecular biology techniques. All cancer cells responded to hypoxia within 72 h by classic EMT changes (fibroblastoid phenotype, SNAIL and beta-catenin nuclear translocation and changes in E-cadherin) and by increased migration and invasiveness. This was involving very early inhibition of glycogen synthase kinase-3beta (GSK-3beta), early SNAIL translocation as well as later and long-lasting activation of Wnt/beta-catenin-signalling machinery. Experimental manipulation, including silencing of hypoxia-inducible factor (HIF)-1alpha and the specific inhibition of mitochondrial generation of reactive oxygen species (ROS), revealed that early EMT-related events induced by hypoxia (GSK-3beta inhibition and SNAIL translocation) were dependent on transient intracellular increased generation of ROS whereas late migration and invasiveness were sustained by HIF-1alpha- and vascular endothelial growth factor (VEGF)-dependent mechanisms. These findings indicate that in cancer cells, early redox mechanisms can switch on hypoxia-dependent EMT programme whereas increased invasiveness is sustained by late and HIF-1alpha-dependent release of VEGF.
Cannito
Stefania
S
Dipartamento di Medicina e Oncologia Sperimentale and Centro Interuniversitario di Fisiopatologia Epatica, University of Torino, Torino, Italy.
Novo
Erica
E
Compagnone
Alessandra
A
Valfrè di Bonzo
Lorenzo
L
Busletta
Chiara
C
Zamara
Elena
E
Paternostro
Claudia
C
Povero
Davide
D
Bandino
Andrea
A
Bozzo
Francesca
F
Cravanzola
Carlo
C
Bravoco
Vittoria
V
Colombatto
Sebastiano
S
Parola
Maurizio
M
D015153:Blotting, Western; D002454:Cell Differentiation / Q000502:physiology; D015687:Cell Hypoxia / Q000502:physiology*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology; D002471:Cell Transformation, Neoplastic / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism / Q000473:pathology; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D008648:Mesoderm / Q000378:metabolism / Q000473:pathology; D009361:Neoplasm Invasiveness / Q000235:genetics / Q000503:physiopathology; D010084:Oxidation-Reduction; D034622:RNA Interference; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D017382:Reactive Oxygen Species; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; D051176:beta Catenin; D038362:Glycogen Synthase Kinase 3