Down-regulation of uPAR and uPA activates caspase-mediated apoptosis and inhibits the PI3K/AKT pathway

Int J Oncol. 2007 Jul;31(1):19-27.


Urokinase plasminogen activator (uPA) and its receptor (uPAR) play a major role in invasion and proliferation. A growing body of evidence has suggested that the uPA system promotes tumor metastasis by several different mechanisms, and not just solely by breaking down the ECM. In this study we have used RNAi-mediated simultaneous down-regulation of uPAR and uPA to determine the signaling pathway molecules and caspase-mediated apoptosis. From our in vitro experiments, we have observed that plasmid-based RNAi-mediated down-regulation of uPAR and uPA in SNB19 human glioma cells caused a decrease in the levels of uPAR protein and uPA enzyme activities. In addition, we observed a decrease in the phosphorylation of the Ras-activated pathway molecules such as FAK, p38MAPK, JNK and ERK1/2, as well as the MEK-activated phosphatidylinositol 3-kinase (PI3k) pathway, and also retarded the dephosphorylation of p-AKTser473 and p-mTORser2448, indicative of a feedback signaling mechanism of the uPAR-uPA system. Activation of caspase 8 accompanied by the release of cytochrome c and cleavage of PARP was also observed and indicative of Fas-mediated apoptosis. The use of FMK-VAD-FAK peptides coupled with FITC indicated activation of polycaspases, which was accompanied by the presence of fragmented nuclei. Our studies provide evidence for the presence of a feedback response of the uPAR-uPA system indicative of the multifaceted role of uPAR, and also the therapeutic potential of simultaneously targeting uPAR and uPA in cancer patients.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis* / genetics
  • Caspase 8 / metabolism*
  • Caspase Inhibitors
  • Cell Line, Tumor
  • Cysteine Proteinase Inhibitors / pharmacology
  • Cytochromes c / metabolism
  • Cytoplasm / metabolism
  • Down-Regulation
  • Humans
  • Mitochondria / metabolism
  • Phosphoinositide-3 Kinase Inhibitors*
  • Plasmids / genetics
  • Poly(ADP-ribose) Polymerases / metabolism
  • Protein Kinases / metabolism
  • Proto-Oncogene Proteins c-akt / antagonists & inhibitors*
  • RNA, Small Interfering / genetics
  • Receptors, Cell Surface / antagonists & inhibitors*
  • Receptors, Cell Surface / genetics
  • Receptors, Urokinase Plasminogen Activator
  • Signal Transduction
  • Transfection
  • Urokinase-Type Plasminogen Activator / antagonists & inhibitors*
  • Urokinase-Type Plasminogen Activator / genetics
  • ras Proteins / metabolism


  • Caspase Inhibitors
  • Cysteine Proteinase Inhibitors
  • PLAUR protein, human
  • Phosphoinositide-3 Kinase Inhibitors
  • RNA, Small Interfering
  • Receptors, Cell Surface
  • Receptors, Urokinase Plasminogen Activator
  • Cytochromes c
  • Poly(ADP-ribose) Polymerases
  • Protein Kinases
  • Proto-Oncogene Proteins c-akt
  • Urokinase-Type Plasminogen Activator
  • Caspase 8
  • ras Proteins