Characterization of insulin-like growth factor-binding protein-related protein-1 in prostate cells

Insulin-like growth factor-binding protein-related protein-1 (IGFBP-rP1; al so known as Mac25, TAF, and PSF) is a member of the IGFBP superfamily. It i s a cysteine-rich protein that shares structural and functional similaritie s with the conventional IGFBPs. In situ hybridization of prostate tissue se ctions show intense IGFBP-rP1 messenger ribonucleic acid (mRNA) expression in normal stroma and glandular epithelium. There was a significant loss of detectable IGFBP-rP1 mRNA in metastatic prostate tissue. IGFBP-rP1 mRNA (No rthern blots) and protein (immunoblots) were detectable in primary cultures of prostatic stromal and epithelial cells as well as in the immortalized n onmalignant prostatic human epithelial cells, P69, and in the P69 metastati c subline, M12. IGFBP-rP1 expression was not detectable in the prostatic ca ncer cell Lines PC-3, DU145, and LNCaP. IGFBP-rP1 expression was regulated in P69 cells but not in M12 cells. Protein and mRNA expression was up-regul ated by IGF-I, transforming growth factor-beta, and retinoic acid. The obse rvations that IGFBP-rP1 expression is significantly diminished in prostate tumorigenesis and is regulated in nonmalignant prostate cells suggest IGFBP -rP1 is important in normal prostatic cell growth.