Soluble urokinase receptor from fibrosarcoma HT-1080 cells

A soluble form of urokinase-binding protein has been isolated from the human fibrosarcoma cell line HT-1080 and cell lines derived from it. Conditioned media of these cells were collected after overnight incubation under serum-free conditions, and were concentrated and passed through a column of Sepharose 4B to which high-molecular-weight urokinase had been attached. After thorough washing, a polypeptide could be eluted from the column with 1 M acetic acid. This material appeared to be a single band of approximately 60 kDa on SDS polyacrylamide gel. It cross-reacted with commercial antibodies made against urokinase receptor, and could be chemically cross-linked to the amino terminal fragment of urokinase. This material was similar to the urokinase receptor that was cleaved from HT-1080 cells by means of phosphatidylinositol-specific phospholipase C.