Pregnancy-Associated Plasma Protein-A (PAPP-A) expression and insulin-like growth factor binding protein-4 protease activity in normal and malignant ovarian surface epithelial cells

Kimberly R. Kalli, Bing K. Chen, Laurie K. Bale, Erica Gernand, Michael T. Overgaard, Claus Oxvig, William Arthur Cliby, Cheryl A Conover

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Pregnancy-Associated Plasma Protein-A (PAPP-A) proteolyses insulin-like growth factor binding protein-4 (IGFBP-4), thereby regulating local IGF availability. Reduced PAPP-A mRNA expression has been reported in ovarian cancer specimens compared to normal ovarian surface epithelial cells (OSE). To characterize PAPP-A expression and proteolytic activity in OSE, we developed a lifespan-extended human cell model using a temperature-sensitive mutant of the SV40 large T antigen (SV40LT). These OSE(tsT) cells proliferate at 34°C (i.e., when SV40LT-positive), but not at 39°C, a temperature at which the SV40LT is unstable (SV40LT-negative). Proteolysis of radiolabeled IGFBP-4 in conditioned media from OSE(tsT) lines was IGF-dependent and blocked by anti-PAPP-A antisera. Temperature shifts that eliminated stable SV40LT induced a 7-fold increase in PAPP-A mRNA and a 4-fold increase in protein. The converse experiment (shifting to SV40LT-positive conditions) resulted in decreased levels of PAPP-A mRNA but little change in PAPP-A protein. Nevertheless, there was a marked reduction in IGF-BP-4 proteolytic activity in medium of SV40LT-positive OSE-(tsT) cells. This decreased PAPP-A activity coincided with a nearly 20-fold increase in mRNA encoding a physiological inhibitor of PAPP-A, the precursor form of eosinophil Major Basic Protein (proMBP), and 4- to 5-fold increases in proMBP protein. Primary cultures of unmodified OSE expressed high levels of PAPP-A and undetectable proMBP, and therefore produced abundant IGFBP-4 protease activity. Short-term ovarian tumor cell cultures expressed variable levels of PAPP-A and high levels of proMBP, and consequently secreted little or no IGFBP-4 protease activity. The concurrent regulation of PAPP-A and its inhibitor, proMBP, suggests that IGFBP-4 proteolysis and local regulation of IGF availability may be altered in malignant ovarian epithelial cells.

Original languageEnglish (US)
Pages (from-to)633-640
Number of pages8
JournalInternational Journal of Cancer
Volume110
Issue number5
DOIs
StatePublished - Jul 10 2004

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Pregnancy-Associated Plasma Protein-A
Epithelial Cells
Polyomavirus Transforming Antigens
Viral Tumor Antigens
Insulin-Like Growth Factor Binding Protein 4
Proteolysis
Messenger RNA
Temperature
Eosinophil Major Basic Protein
Proteins
Protein Precursors
Conditioned Culture Medium

Keywords

  • IGFBP-4 protease
  • Major Basic Protein
  • Ovarian cancer
  • Ovarian epithelial cells
  • Pregnancy-associated plasma protein-A

ASJC Scopus subject areas

  • Cancer Research
  • Oncology

Cite this

Pregnancy-Associated Plasma Protein-A (PAPP-A) expression and insulin-like growth factor binding protein-4 protease activity in normal and malignant ovarian surface epithelial cells. / Kalli, Kimberly R.; Chen, Bing K.; Bale, Laurie K.; Gernand, Erica; Overgaard, Michael T.; Oxvig, Claus; Cliby, William Arthur; Conover, Cheryl A.

In: International Journal of Cancer, Vol. 110, No. 5, 10.07.2004, p. 633-640.

Research output: Contribution to journalArticle

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abstract = "Pregnancy-Associated Plasma Protein-A (PAPP-A) proteolyses insulin-like growth factor binding protein-4 (IGFBP-4), thereby regulating local IGF availability. Reduced PAPP-A mRNA expression has been reported in ovarian cancer specimens compared to normal ovarian surface epithelial cells (OSE). To characterize PAPP-A expression and proteolytic activity in OSE, we developed a lifespan-extended human cell model using a temperature-sensitive mutant of the SV40 large T antigen (SV40LT). These OSE(tsT) cells proliferate at 34°C (i.e., when SV40LT-positive), but not at 39°C, a temperature at which the SV40LT is unstable (SV40LT-negative). Proteolysis of radiolabeled IGFBP-4 in conditioned media from OSE(tsT) lines was IGF-dependent and blocked by anti-PAPP-A antisera. Temperature shifts that eliminated stable SV40LT induced a 7-fold increase in PAPP-A mRNA and a 4-fold increase in protein. The converse experiment (shifting to SV40LT-positive conditions) resulted in decreased levels of PAPP-A mRNA but little change in PAPP-A protein. Nevertheless, there was a marked reduction in IGF-BP-4 proteolytic activity in medium of SV40LT-positive OSE-(tsT) cells. This decreased PAPP-A activity coincided with a nearly 20-fold increase in mRNA encoding a physiological inhibitor of PAPP-A, the precursor form of eosinophil Major Basic Protein (proMBP), and 4- to 5-fold increases in proMBP protein. Primary cultures of unmodified OSE expressed high levels of PAPP-A and undetectable proMBP, and therefore produced abundant IGFBP-4 protease activity. Short-term ovarian tumor cell cultures expressed variable levels of PAPP-A and high levels of proMBP, and consequently secreted little or no IGFBP-4 protease activity. The concurrent regulation of PAPP-A and its inhibitor, proMBP, suggests that IGFBP-4 proteolysis and local regulation of IGF availability may be altered in malignant ovarian epithelial cells.",
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AU - Bale, Laurie K.

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AU - Conover, Cheryl A

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