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.

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 degrees C (i.e., when SV40LT-positive), but not at 39 degrees 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.

• Authors: Kimberly R Kalli, Bing-Kun Chen, Laurie K Bale, Erica Gernand, Michael T Overgaard, Claus Oxvig, William A Cliby, Cheryl A Conover
• Journal: International journal of cancer (Int J Cancer) Vol. 110 Issue 5 Pg. 633-40 (Jul 10 2004) ISSN: 0020-7136 [Print] United States
• PMID: 15146551 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)
• Copyright: Copyright 2004 Wiley-Liss, Inc.

Chemical References

• Culture Media, Conditioned
• Culture Media, Serum-Free
• DNA, Complementary
• Insulin-Like Growth Factor Binding Protein 4
• RNA, Messenger
• RNA
• Pregnancy-Associated Plasma Protein-A

Topics

• Adult
• Aged
• Aged, 80 and over
• Blotting, Northern
• Cell Division
• Cell Line
• Cell Line, Tumor
• Cells, Cultured
• Culture Media, Conditioned (pharmacology)
• Culture Media, Serum-Free
• DNA, Complementary (metabolism)
• Enzyme-Linked Immunosorbent Assay
• Eosinophils (metabolism)
• Epithelial Cells (metabolism)
• Female
• Humans
• Immunohistochemistry
• Insulin-Like Growth Factor Binding Protein 4 (biosynthesis)
• Middle Aged
• Mutation
• Ovarian Neoplasms (pathology)
• Ovary (metabolism)
• Pregnancy-Associated Plasma Protein-A (biosynthesis, metabolism)
• RNA (metabolism)
• RNA, Messenger (metabolism)
• Temperature
• Time Factors