Generation of Anti-Insulin-Like Growth Factor-Binding Protein-Related Protein 1 (IGFBP-rP1/MAC25) Monoclonal Antibodies and Immunoassay: Quantification of IGFBP-rP1 in Human Serum and Distribution in Human Fluids and Tissues

The IGF-binding protein (IGFBP)-related proteins (rPs) are a group of recently described cysteine-rich proteins that share significant amino-terminal structural similarity with the conventional IGFBPs. IGFBP-rP1 (also known as MAC25/angiomodulin/prostacyclin-stimulating factor and T1A12), regulates cellular proliferation, adhesion, and angiogenesis and stimulates prostacyclin synthesis. We characterized new monoclonal antibodies generated against IGFBP-rP1 and have used them to study the distribution of IGFBP-rP1 in human biological fluids and tissues. Additionally, we have developed a noncompetitive sandwich-type immunoassay to quantitate the concentrations of IGFBP-rP1 in human serum. IGFBP-rP1 was readily detectable in serum, urine, amniotic fluid, and cerebrospinal fluid by immunoblot analysis. Evaluation of the newly developed immunoassay demonstrated acceptable analytical performance, with a detection limit of 0.7 μg/liter, a dynamic range of 3.1–100 μg/liter, and intra- and interassay coefficients ...