Isolation and partial characterization of the structures of fibroblast activating factor-related proteins from U937 cells.

Human cultured monocyte-like tumour cells of the U937 histiocyte derived line were stimulated with phorbol myristate acetate, and generated and released an 18,000 MW polypeptide fibroblast-activating factor (FAF). Based on recognition by an antiserum to a synthetic peptide representing the 17 amino-terminal amino acids of FAF, two proteins of 32,000 and 35,000 MW were identified in extracts of U937 cells. Purification of the intracellular FAF-related proteins to homogeneity allowed the generation and amino acid sequencing of nine tryptic fragments of 4-11 amino acids. Neither of the intracellular FAF-related proteins exhibited the fibroblast proliferation-stimulating activity of FAF, suggesting that they are biosynthetic precursors analogous to the inactive propeptides of interleukin-1 beta and tumour necrosis factor-alpha.