Identification of the monocyte chemotactic protein from human osteosarcoma cells and monocytes: detection of a novel N-terminally processed form.

The chemotactic activity for monocytes in culture supernatants from double-stranded RNA-stimulated human MG-63 osteosarcoma cells and from LPS-stimulated human monocytes was purified to homogeneity and characterized by amino acid sequence analysis. The chemotactic protein derived from the fibroblastoid osteosarcoma cells had a blocked N-terminus but sequencing of tryptic fragments showed that it was identical with a recently identified monocyte chemoattractant designated MCP-1 or MCAF isolated from glioma or myelomonocytic cells, respectively. Preparations of monocyte -derived chemotactic activity appeared to contain not only the blocked protein, but also a novel N-terminally processed form of this molecule, lacking 5 amino acid residues.