title: Intermittent hypoxia regulates stem-like characteristics and differentiation of neuroblastoma cells.
abstract: BACKGROUND
  Neuroblastomas are the most common extracranial solid tumors in children. Neuroblastomas are derived from immature cells of the sympathetic nervous system and are characterized by clinical and biological heterogeneity. Hypoxia has been linked to tumor progression and increased malignancy. Intermittent hypoxia or repeated episodes of hypoxia followed by re-oxygenation is a common phenomenon in solid tumors including neuroblastoma and it has a significant influence on the outcome of therapies. The present study focuses on how intermittent hypoxia modulates the stem-like properties and differentiation in neuroblastoma cells.
  
  
  RESULTS
  Cell survival was assessed by clonogenic assay and cell differentiation was determined by morphological characterization. Hypoxia-inducible genes were analyzed by real-time PCR and Western blotting. Immunofluorescence, real-time PCR and Western blotting were utilized to study stem cell markers. Analysis of neural crest/sympathetic nervous system (SNS) markers and neuronal differentiation markers were done by real-time PCR and Western blotting, respectively. Intermittent hypoxia stimulated the levels of HIF-1α and HIF-2 α proteins and enhanced stem-like properties of neuroblastoma cells. In intermittent hypoxia-conditioned cells, downregulation of SNS marker genes and upregulation of genes expressed in the neural crest were observed. Intermittent hypoxia suppressed the retinoic acid-induced differentiation of neuroblastoma cells.
  
  
  CONCLUSIONS
  Our results suggest that intermittent hypoxia enhances stem-like characteristics and suppresses differentiation propensities in neuroblastoma cells.
authors.affiliation: Department of Cancer Biology and Pharmacology, University of Illinois College of Medicine, Peoria, Illinois, United States of America.
authors.forename: Vasantha Kumar
authors.initials: VK
authors.lastname: Bhaskara
authors.forename: Indra
authors.initials: I
authors.lastname: Mohanam
authors.forename: Jasti S
authors.initials: JS
authors.lastname: Rao
authors.forename: Sanjeeva
authors.initials: S
authors.lastname: Mohanam
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D015687:Cell Hypoxia / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D009432:Neural Crest / Q000378:metabolism; D009447:Neuroblastoma / Q000235:genetics / Q000473:pathology*; D034741:RNA, Small Interfering / Q000378:metabolism; D013564:Sympathetic Nervous System / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology
chemical_list: D014408:Biomarkers, Tumor; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D034741:RNA, Small Interfering; D014212:Tretinoin