Purification and Identification of Mouse Lung Microvessel Endothelial Cell-derived Chemoattractant for Lung-metastasizing Murine RAW117 Large-Cell Lymphoma Cells: Identification as Mouse Monocyte Chemotactic Protein I1

We reported recently that medium conditioned with mouse lung microvessel endothelial cells possessed chemotactic activity for a highly lung-metastatic variant (L17) of the RAW117 murine large-cell lymphoma cell line but not for the poorly metastatic parental cells (P) or a liver-metastasizing variant (H10). The chemotactic factor was purified to homogeneity by a five-step procedure involving hydrophobic interaction, Cibacron blue F3GA affinity, metal affinity, aniÃ3nexchange, and reversed phase chromatography, followed by preparative gel electrophoresis. The purified material appeared as a single broad band when analyzed by SDS-PAGE, with an average molecular weight of 26,000. The factor was cleaved by cyanogen bromide treatment, and a partial amino acid se quence of one of the cleaved polypeptides proved identical to mouse monocyte chemotactic protein 1 (mMCP-1/JE). The amino acid composi tion of the factor also indicated similarity to mMCP-1/JE. Separately purified mMCP-1/JE significantly stimulated the chemotactic migration of RAW117 cells (L17»H10, P). When recombinant human monocyte chemotactic protein 1 was compared to the purified endothelial cell che motactic factor as a Chemoattractant, similar migratory responses were observed in the RAW117 sublines. The chemotactic activity for L17 cells was significantly reduced from lung microvessel endothelial cell-condi tioned medium after treatment with anti-mouse MCP-1 antibody. In contrast, the migration-stimulating activity of liver sinusoidal endothelial cell-conditioned medium to H10 cells was not affected by anti-mouse MCP-1. A major function of mMCP-1/JE is to recruit monocytes to inflammatory sites, and our results suggest that mMCP-1/JE also facili tates lymphoma lung invasion and metastasis.