Genetic downregulation of pregnancy-associated plasma protein-A (PAPP-A) by bikunin reduces IGF-I-dependent Akt and ERK1/2 activation and subsequently reduces ovarian cancer cell growth, invasion and metastasis

Int J Cancer. 2004 Apr 10;109(3):336-47. doi: 10.1002/ijc.11700.


A Kunitz-type protease inhibitor, bikunin, downregulates expression of uPA and its receptor uPAR at the mRNA and protein levels in several types of tumor cells. Our recent work showed that, using a cDNA microarray analysis, pregnancy-associated plasma protein-A (PAPP-A) is a candidate bikunin target gene. To clarify how reduced levels of PAPP-A may confer repressed invasiveness, we transfected human ovarian cancer cell line HRA with antisense (AS)-PAPP-A cDNA and compared the properties of the transfected cells to those of parental HRA cells. Here, we show that regulation of uPA mRNA and protein by IGF-I depends on the PI3K and MAPK signaling pathways and phosphorylation of Akt and ERK1/2 is required for IGF-I-mediated cell invasion; that IGFBP-4 protease in HRA cells is identified as PAPP-A; that reduced PAPP-A expression is associated with the upregulation of IGFBP-4 expression; that higher intact IGFBP-4 levels were associated with low invasive potential and growth rate in AS-PAPP-A cells in response to IGF-I; that IGF-I stimulates Akt and ERK1/2 activation of both the control and antisense cells, but the relative potency and efficacy of IGF-I were lower in the antisense cells compared to the control; and that genetic downregulation of PAPP-A reduces the proliferation, invasion and metastasis of HRA cells. In conclusion, our data identify a novel role for PAPP-A as a bikunin target gene. IGF-I-induced IGFBP-4 proteolysis by PAPP-A may enhance cell growth and invasion through IGF-I-dependent Akt and ERK1/2 activation and subsequently upregulation of uPA.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Division / drug effects
  • Down-Regulation / drug effects
  • Enzyme Activation
  • Female
  • Humans
  • Insulin-Like Growth Factor Binding Protein 4 / metabolism
  • Insulin-Like Growth Factor I / pharmacology*
  • MAP Kinase Signaling System
  • Membrane Glycoproteins / pharmacology*
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases / metabolism*
  • Neoplasm Invasiveness
  • Neoplasm Metastasis
  • Oligonucleotides, Antisense / pharmacology
  • Ovarian Neoplasms / metabolism
  • Ovarian Neoplasms / pathology*
  • Pregnancy-Associated Plasma Protein-A / genetics
  • Pregnancy-Associated Plasma Protein-A / metabolism*
  • Protein Serine-Threonine Kinases*
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-akt
  • RNA, Messenger / metabolism
  • Serine Proteinase Inhibitors / pharmacology
  • Trypsin Inhibitor, Kunitz Soybean / pharmacology*
  • Tumor Cells, Cultured
  • Urokinase-Type Plasminogen Activator / genetics


  • Insulin-Like Growth Factor Binding Protein 4
  • Membrane Glycoproteins
  • Oligonucleotides, Antisense
  • Proto-Oncogene Proteins
  • RNA, Messenger
  • SPINT2 protein, human
  • Serine Proteinase Inhibitors
  • Insulin-Like Growth Factor I
  • Trypsin Inhibitor, Kunitz Soybean
  • AKT1 protein, human
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases
  • Urokinase-Type Plasminogen Activator
  • Pregnancy-Associated Plasma Protein-A