Identification as Complement Component C3b Cells Secreted by Mouse Hepatic Sinusoidal Endothelial Cells: A Paracrine Migration-stimulating Factor for Metastatic Tumor

Selective malignant cell invasion at secondary sites mediated by organspecific (paracrine) motility factors may be of importance in preferential organ colonization of metastatic cells. In this study we isolated and exam ined a migration-stimulating activity present in mouse hepatic sinusoidal endothelial cell-conditioned medium (HSE-CM). HSE-CM contains mi gration-stimulating activity for highly liver-metastatic (RAW117-H10) and highly lungand liver-metastatic (KAW117-L17) mouse large cell lymphoma sublines but not for the poorly metastatic parental line (RAW 117P). A migration-stimulating factor for H10 cells was purified from HSE-CM by hydroxylapatite affinity and DEAE aniÃ3nexchange chromatography, Sephacryl S-200 gel filtration, and preparative native gel electrophoresis. The activity in each of the purification fractions was mea sured in a Transwell chamber assay using 3-/¿mdiameter pore filters. Upon sodium dodecyl sulfate polyacrylamide gel electrophoresis, the com ponent migrated as a single component of M, 200,000 (nonreducing conditions) or as two components of Mr ~110,000 and ~67,000 (reducing conditions). The factor was bound to Concanavalin A-Sepharose but not to heparinor gelatin-Sepharose affinity columns, induced mainly H10 chemotactic cell activity and some chemokinetic activity, and preferentially stimulated the chemotaxis of liver-colonizing RAW117 sublines (H10 > L17 > P). Ml .-iiTininal amino acid sequence analysis of each subunit indicated that the HSE-CM-derived migration-stimulating factor was a proteolytic fragment of complement component C3. HSE-derived migra tion-stimulating factors may be important in determining the ability of RAYV117 tumor cells to invade and colonize the liver.