title: Hedgehog signaling regulates hypoxia induced epithelial to mesenchymal transition and invasion in pancreatic cancer cells via a ligand-independent manner.
abstract: BACKGROUND
  Hypoxia plays a vital role in cancer epithelial to mesenchymal transition (EMT) and invasion. However, it is not quite clear how hypoxia may contribute to these events. Here we investigate the role of Hedgehog (Hh) signaling in hypoxia induced pancreatic cancer EMT and invasion.
  
  
  METHODS
  Pancreatic cancer cells were cultured under controlled hypoxia conditions (3% O2) or normoxic conditions. HIF-1α siRNA, cyclopamine (a SMO antagonist) and GLI1 siRNA were used to inhibit HIF-1α transcription or Hh signaling activation. The effect of hypoxia and Hh signaling on cancer cell EMT and invasion were evaluated by Quantitative real-time PCR analysis, Western blot analysis and invasion assay.
  
  
  RESULTS
  Here, we show that non-canonical Hh signaling is required as an important role to switch on hypoxia-induced EMT and invasion in pancreatic cancer cells. Moreover, our data demonstrate hypoxia induces EMT process as well as invasion, and activates the non-canonical Hh pathway without affecting sonic hedgehog homolog (SHH) expression. Moreover, these effects are reversible upon HIF-1α siRNA interference with unchanged SHH and patched1 (PTCH1) level. Furthermore, our data demonstrate that hypoxia induced invasion and EMT process are effectively inhibited by Smoothened (SMO) antagonist cyclopamine and GLI1 siRNA. In addition, GLI1 interference inhibited EMT progress with significantly suppressed vimentin expression, whereas inhibition of SMO through cyclopamine could not reduce vimentin level. This data indicate that hypoxia could trigger other factors (such as TGF-β, KRAS or RTK) bypassing SMO to activate GLI1 directly.
  
  
  CONCLUSIONS
  Our findings suggest that Hh signaling modulates hypoxia induced pancreatic cancer EMT and invasion in a ligand-independent manner. Thus, Hh signaling may represent a promising therapeutic target for preventing pancreatic cancer progression.
authors.affiliation: Department of Hepatobiliary Surgery, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, 277 West Yanta Road, Xi'an 710061Shaanxi Province, China.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Lei
authors.forename: Jiguang
authors.initials: J
authors.lastname: Ma
authors.forename: Qingyong
authors.initials: Q
authors.lastname: Ma
authors.forename: Xuqi
authors.initials: X
authors.lastname: Li
authors.forename: Han
authors.initials: H
authors.lastname: Liu
authors.forename: Qinhong
authors.initials: Q
authors.lastname: Xu
authors.forename: Wanxing
authors.initials: W
authors.lastname: Duan
authors.forename: Qing
authors.initials: Q
authors.lastname: Sun
authors.forename: Jun
authors.initials: J
authors.lastname: Xu
authors.forename: Zheng
authors.initials: Z
authors.lastname: Wu
authors.forename: Erxi
authors.initials: E
authors.lastname: Wu
mesh_terms: D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics; D015870:Gene Expression; D020868:Gene Silencing; D053823:Hedgehog Proteins / Q000378:metabolism*; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D008024:Ligands; D008954:Models, Biological; D009361:Neoplasm Invasiveness; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D010641:Phenotype; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D000072086:Smoothened Receptor; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D000071676:Zinc Finger Protein GLI1
chemical_list: D053823:Hedgehog Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008024:Ligands; D015513:Oncogene Proteins; D043562:Receptors, G-Protein-Coupled; C491023:SMO protein, human; D000072086:Smoothened Receptor; D015534:Trans-Activators; D000071676:Zinc Finger Protein GLI1