title: Targeting neuroblastoma stem cells with retinoic acid and proteasome inhibitor.
abstract: BACKGROUND
  Neuroblastma cell lines contain a side-population of cells which express stemness markers. These stem-like cells may represent the potential underlying mechanism for resistance to conventional therapy and recurrence of neuroblastoma in patients.
  
  
  RESULTS
  To develop novel strategies for targeting the side-population of neurobastomas, we analyzed the effects of 13-cis-retinoic acid (RA) combined with the proteasome inhibitor MG132. The short-term action of the treatment was compared with effects after a 5-day recovery period during which both chemicals were withdrawn. RA induced growth arrest and differentiation of SH-SY5Y and SK-N-BE(2) neuroblastoma cell lines. Inhibition of the proteasome caused apoptosis in both cell lines, thus, revealing the critical role of this pathway in the regulated degradation of proteins involved in neuroblastoma proliferation and survival. The combination of RA with MG132 induced apoptosis in a dose-dependent manner, in addition to promoting G2/M arrest in treated cultures. Interestingly, expression of stem cell markers such as Nestin, Sox2, and Oct4 were reduced after the recovery period of combined treatment as compared with untreated cells or treated cells with either compound alone. Consistent with this, neurosphere formation was significantly impaired by the combined treatment of RA and MG132.
  
  
  CONCLUSIONS
  Given that stem-like cells are associated with resistant to conventional therapy and are thought to be responsible for relapse, our results suggest that dual therapy of RA and proteasome inhibitor might be beneficial for targeting the side-population of cells associated residual disease in high-risk neuroblastoma.
authors.affiliation: Laboratory of Molecular Endocrinology, Centro de Investigación Príncipe Felipe, Valencia, Spain.
authors.forename: Barbara
authors.initials: B
authors.lastname: Hämmerle
authors.forename: Yania
authors.initials: Y
authors.lastname: Yañez
authors.forename: Sarai
authors.initials: S
authors.lastname: Palanca
authors.forename: Adela
authors.initials: A
authors.lastname: Cañete
authors.forename: Deborah J
authors.initials: DJ
authors.lastname: Burks
authors.forename: Victoria
authors.initials: V
authors.lastname: Castel
authors.forename: Jaime
authors.initials: J
authors.lastname: Font de Mora
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D005434:Flow Cytometry; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology*; D018613:Microscopy, Confocal; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D064231:Nestin / Q000378:metabolism; D009447:Neuroblastoma / Q000378:metabolism / Q000473:pathology; D050814:Octamer Transcription Factor-3 / Q000378:metabolism; D061988:Proteasome Inhibitors / Q000494:pharmacology*; D055748:SOXB1 Transcription Factors / Q000378:metabolism; D058985:Side-Population Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D013997:Time Factors; D014212:Tretinoin / Q000494:pharmacology*
chemical_list: D007976:Leupeptins; C577484:NES protein, human; D064231:Nestin; D050814:Octamer Transcription Factor-3; C494173:POU5F1 protein, human; D061988:Proteasome Inhibitors; C527782:SOX2 protein, human; D055748:SOXB1 Transcription Factors; D014212:Tretinoin; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde