title: Notch1 is required for hypoxia-induced proliferation, invasion and chemoresistance of T-cell acute lymphoblastic leukemia cells.
abstract: BACKGROUND
  Notch1 is a potent regulator known to play an oncogenic role in many malignancies including T-cell acute lymphoblastic leukemia (T-ALL). Tumor hypoxia and increased hypoxia-inducible factor-1α (HIF-1α) activity can act as major stimuli for tumor aggressiveness and progression. Although hypoxia-mediated activation of the Notch1 pathway plays an important role in tumor cell survival and invasiveness, the interaction between HIF-1α and Notch1 has not yet been identified in T-ALL. This study was designed to investigate whether hypoxia activates Notch1 signalling through HIF-1α stabilization and to determine the contribution of hypoxia and HIF-1α to proliferation, invasion and chemoresistance in T-ALL.
  
  
  METHODS
  T-ALL cell lines (Jurkat, Sup-T1) transfected with HIF-1α or Notch1 small interference RNA (siRNA) were incubated in normoxic or hypoxic conditions. Their potential for proliferation and invasion was measured by WST-8 and transwell assays. Flow cytometry was used to detect apoptosis and assess cell cycle regulation. Expression and regulation of components of the HIF-1α and Notch1 pathways and of genes related to proliferation, invasion and apoptosis were assessed by quantitative real-time PCR or Western blot.
  
  
  RESULTS
  Hypoxia potentiated Notch1 signalling via stabilization and activation of the transcription factor HIF-1α. Hypoxia/HIF-1α-activated Notch1 signalling altered expression of cell cycle regulatory proteins and accelerated cell proliferation. Hypoxia-induced Notch1 activation increased the expression of matrix metalloproteinase-2 (MMP2) and MMP9, which increased invasiveness. Of greater clinical significance, knockdown of Notch1 prevented the protective effect of hypoxia/HIF-1α against dexamethasone-induced apoptosis. This sensitization correlated with losing the effect of hypoxia/HIF-1α on Bcl-2 and Bcl-xL expression.
  
  
  CONCLUSIONS
  Notch1 signalling is required for hypoxia/HIF-1α-induced proliferation, invasion and chemoresistance in T-ALL. Pharmacological inhibitors of HIF-1α or Notch1 signalling may be attractive interventions for T-ALL treatment.
authors.affiliation: Department of Hematology, Qilu Hospital of Shandong University, Jinan, Shandong, 107 West Wenhua Road, Jinan, Shandong, 250012, People's Republic of China.
authors.forename: Jie
authors.initials: J
authors.lastname: Zou
authors.forename: Peng
authors.initials: P
authors.lastname: Li
authors.forename: Fei
authors.initials: F
authors.lastname: Lu
authors.forename: Na
authors.initials: N
authors.lastname: Liu
authors.forename: Jianjian
authors.initials: J
authors.lastname: Dai
authors.forename: Jingjing
authors.initials: J
authors.lastname: Ye
authors.forename: Xun
authors.initials: X
authors.lastname: Qu
authors.forename: Xiulian
authors.initials: X
authors.lastname: Sun
authors.forename: Daoxin
authors.initials: D
authors.lastname: Ma
authors.forename: Jino
authors.initials: J
authors.lastname: Park
authors.forename: Chunyan
authors.initials: C
authors.lastname: Ji
mesh_terms: D048708:Cell Growth Processes / Q000502:physiology; D015687:Cell Hypoxia / Q000502:physiology; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D019169:Jurkat Cells; D020778:Matrix Metalloproteinase 2 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D009361:Neoplasm Invasiveness; D054218:Precursor T-Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D034741:RNA, Small Interfering / Q000008:administration & dosage / Q000235:genetics; D051881:Receptor, Notch1 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection; D015854:Up-Regulation
chemical_list: C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C497761:NOTCH1 protein, human; D034741:RNA, Small Interfering; D051881:Receptor, Notch1; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9