INSULIN-LIKE GROWTH FACTOR-BINDING PROTEINS (IGFBP)-4, (IGFBP)-5, AND(IGFBP)-6 IN THE BENIGN AND MALIGNANT HUMAN PROSTATE - IGFBP-5 MESSENGER-RIBONUCLEIC-ACID LOCALIZATION DIFFERS FROM IGFBP-5 PROTEIN LOCALIZATION
Mk. Tennant et al., INSULIN-LIKE GROWTH FACTOR-BINDING PROTEINS (IGFBP)-4, (IGFBP)-5, AND(IGFBP)-6 IN THE BENIGN AND MALIGNANT HUMAN PROSTATE - IGFBP-5 MESSENGER-RIBONUCLEIC-ACID LOCALIZATION DIFFERS FROM IGFBP-5 PROTEIN LOCALIZATION, The Journal of clinical endocrinology and metabolism, 81(10), 1996, pp. 3783-3792
Insulin-like growth factor (IGF)-binding proteins (IGFBPs) modulate th
e actions of IGF. We have previously reported that IGFBP-2 messenger r
ibonucleic acid (mRNA) and protein are increased, and IGFBP-3 protein
decreased in malignant prostate epithelium compared to benign epitheli
um. In this study, we examined the other IGFBPs secreted by prostate c
ells in vitro, namely IGFBP-4, -5, and 6. Immunoreactivity and mRNA si
gnals for IGFBP-4 and -6 were localized to epithelial cells, with less
signal in stroma. IGFBP-4 immunostaining and hybridization signal wer
e 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 inc
reased in malignant compared to benign epithelium. IGFBP-5 mRNA signal
was not localized to epithelial cells; rather, the signal was over st
romal 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 epith
elium, that IGFBP-6 is present in benign and malignant epithelium, and
that there is differential localization of IGFBP-5 mRNA and protein i
n prostate tissue. IGFBP-5 that is made by fibroblasts appears to be s
equestered by epithelial cells. IGFBP-5 may, therefore, be a factor in
cellular interactions between stromal and epithelial cells that are o
f fundamental importance for normal prostatic development and function
.