Insulin-like growth factor-binding proteins (IGFBP)-4, -5, and -6 in the benign and malignant human prostate: IGFBP-5 messenger ribonucleic acid localization differs from IGFBP-5 protein localization

Marie K. Tennant, J. Brantley Thrasher, Patrick A. Twomey, Roger S. Birnbaum, Stephen R. Plymate

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54 Scopus citations

Abstract

Insulin-like growth factor (IGF)-binding proteins (IGFBPs) modulate the actions of IGF. We have previously reported that IGFBP-2 messenger ribonucleic acid (mRNA) and protein are increased, and IGFBP-3 protein decreased in malignant prostate epithelium compared to benign epithelium. In this study, we examined the other IGFBPs secreted by prostate cells in vitro, namely IGFBP-4, -5, and 6. Immunoreactivity and mRNA signals for IGFBP-4 and -6 were localized to epithelial cells, with less signal in stroma. IGFBP-4 immunostaining and hybridization signal were significantly increased in prostate adenocarcinoma compared to those in benign epithelium. Immunostaining for IGFBP-5 was localized to the epithelium and stroma. IGFBP- 5 immunoreactivity was significantly increased in malignant compared to benign epithelium. IGFBP-5 mRNA signal was not localized to epithelial cells; rather, the signal was over stromal cells surrounding the acinar structures. These cells are thought to be fibroblasts. We show that IGFBP-4 mRNA and protein and IGFBP-5 protein are increased in malignant epithelium compared to benign epithelium, that IGFBP-6 is present in benign and malignant epithelium, and that there is differential localization of IGFBP-5 mRNA and protein in prostate tissue. IGFBP-5 that is made by fibroblasts appears to be sequestered by epithelial cells. IGFBP-5 may, therefore, be a factor in cellular interactions between stromal and epithelial cells that are of fundamental importance for normal prostatic development and function.

Original languageEnglish (US)
Pages (from-to)3783-3792
Number of pages10
JournalJournal of Clinical Endocrinology and Metabolism
Volume81
Issue number10
DOIs
StatePublished - Oct 21 1996

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