INSULIN-LIKE GROWTH-FACTOR (IGF)-I, (IGF)-II AND IGF-BINDING PROTEINSIN THE CYST FLUID OF A PATIENT WITH ASTROCYTOMA

Insulin-like growth factor (IGF)-I, -II and IGF-binding proteins (IGFB Ps) were demonstrated in the cyst fluid of a patient with a hypothalam ic astrocytoma. The astrocytoma cyst fluid was subjected to gel chroma tography at low pH and the IGF-I and IGF-II levels were measured by sp ecific radioimmunoassays. Immunoreactive IGF-I and IGF-II levels were 19 ng/ml and 78 ng/ml respectively. Several-fold higher IGF-II values were obtained when cyst fluid was not extracted or was extracted with acid ethanol before radioimmunoassay analysis. The immunoreactive IGFB P-1 concentration was 26 ng/ml. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and subsequent Western ligand blotting with [I-125]IGF-II revealed bands at approximately 200,34.5, 29.5, 24 and 21 kD as visualized by autoradiography. Binding studies demonstra ted that these binding proteins bind specifically [I-125]IGF-I and [I- 125]IGF-II. These observations suggest that IGFs as well as IGF-bindin g proteins are produced by astrocytoma cells and may act in a paracrin e or autocrine fashion capable of modulating the growth of astrocytoma tumours.