Insulin-Like Growth Factors (IGF)-I and -II and IGF-Binding Proteins in the Prolactinoma Cyst Fluid

Abstract

<i>Background: </i>Brain tumours produce insulin-like growth factors (IGFs) and IGF-binding proteins (IGFBPs). It is therefore feasible that cyst fluid from these tumours also contains detectable concentrations of IGFs and IGFBPs. This was the reason for measuring and characterizing these factors in prolactinoma cyst fluid. <i>Patients and Methods: </i>The cyst fluid underwent gel chromatography at low pH, and the IGF levels were determined by radioimmunoassay. In addition, sodium dodecyl sulphate – polyacrylamide gel electrophoresis (SDS-PAGE) and Western ligand blotting as well as binding studies with radiolabelled IGFs were performed. <i>Results: </i>The immunoreactive IGF-I, IGF-II and IGFBP-1 concentrations were 22,74 and 20 ng/ml, respectively. SDS-PAGE and subsequent Western ligand blotting using radiolabelled IGF-II gave bands with an estimated molecular weight of ≈200, 34, 28 and 24 kD. Additional binding studies showed specific binding of labelled IGF-I and IGF-II to these IGF-binding proteins. <i>Conclusions: </i>These results suggest that IGFs and IGFBPs are secreted by prolac-tinomas and that these factors may alter the growth characteristics of these tumours. Furthermore, the distinct pattern of IGFBPs might be used as a tool for differential diagnosis in various brain tumours.