uPAR and cathepsin B knockdown inhibits radiation-induced PKC integrated integrin signaling to the cytoskeleton of glioma-initiating cells

Int J Oncol. 2012 Aug;41(2):599-610. doi: 10.3892/ijo.2012.1496. Epub 2012 May 24.

Abstract

Despite advances in radiotherapeutic and chemotherapeutic techniques and aggressive surgical resection, the prognosis of glioblastoma patients is dismal. Accumulation of evidence indicates that some cancer cells survive even the most aggressive treatments, and these surviving cells, which are resistant to therapy and are perhaps essential for the malignancy, may be cancer stem cells. The CD133 surface marker is commonly used to isolate these extremely resistant glioma-initiating cells (GICs). In the present study, GICs which tested positive for the CD133 marker (CD133+) were isolated from both the established U251 cell line and the 5310 xenograft glioma cell line to study the events related to the molecular pathogenesis of these cells. Simultaneous down-regulation of uPAR and cathepsin B by shRNA (pUC) treatment caused the disruption of radiation-induced complex formation of pPKC θ/δ, integrin β1 and PKC ζ, integrin β1 in glioma cells. Further, pUC treatment inhibited PKC/integrin signaling via FAK by causing disassociation of FAK and the cytoskeletal molecules vinculin and α-actinin. Also, we observed the inhibition of ERK phosphorylation. This inhibition was mediated by pUC and directed a negative feedback mechanism over the FAK signaling molecules, which led to an extensive reduction in the signal for cytoskeletal organization generating migratory arrest. Altogether, it can be hypothesized that knockdown of uPAR and cathepsin B using shRNA is an effective strategy for controlling highly invasive glioma cells and extremely resistant glioma-initiating cells.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Acetophenones / pharmacology
  • Animals
  • Antigens, Differentiation / metabolism
  • Benzopyrans / pharmacology
  • Cathepsin B / genetics*
  • Cathepsin B / metabolism
  • Cell Adhesion Molecules, Neuronal / metabolism
  • Cell Line, Tumor
  • Cell Movement
  • Cell Transformation, Neoplastic
  • Cytoskeleton / metabolism*
  • Extracellular Matrix / metabolism
  • Extracellular Matrix / physiology
  • Gene Expression / radiation effects
  • Gene Knockdown Techniques
  • Glioma / pathology*
  • Humans
  • Integrin beta1 / metabolism*
  • Integrins / metabolism
  • Mice
  • Mice, Nude
  • Neoplastic Stem Cells / metabolism*
  • Neoplastic Stem Cells / radiation effects
  • Protein Binding
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase C / metabolism*
  • RNA Interference
  • RNA, Small Interfering / genetics
  • Radiation Tolerance
  • Receptors, Urokinase Plasminogen Activator / genetics*
  • Receptors, Urokinase Plasminogen Activator / metabolism
  • Signal Transduction
  • Spheroids, Cellular / metabolism
  • Xenograft Model Antitumor Assays

Substances

  • Acetophenones
  • Antigens, Differentiation
  • Benzopyrans
  • Cell Adhesion Molecules, Neuronal
  • Integrin beta1
  • Integrins
  • RNA, Small Interfering
  • Receptors, Urokinase Plasminogen Activator
  • rottlerin
  • Protein Kinase C
  • CTSB protein, human
  • Cathepsin B