EXTRACELLULAR ANNEXIN-VI EXPRESSION IS ASSOCIATED WITH DIVALENT CATION-DEPENDENT ENDOTHELIAL-CELL ADHESION OF METASTATIC RAW117 LARGE-CELL LYMPHOMA-CELLS

We previously found that cell surface molecules of similar to 70, simi lar to 35, similar to 32, similar to 22, and similar to 14 kDa from li ver-metastatic murine RAW117 large-cell lymphoma cells bound to target liver microvessel endothelial cells. Isolation and sequencing of the similar to 35-kDa component revealed it to be annexin II, a Ca2+-bindi ng molecule involved in cytoskeletal and membrane interactions. Annexi n II antibodies inhibited the adhesion of RAW117 tumor cells to live o r fixed liver endothelial cells, and purified tumor cell surface fract ions containing the similar to 35-kDa component inhibited partially RA W117 cell-endothelial cell adhesion, suggesting a role for annexins in tumor cell-endothelial cell adhesion. In the present study we identif ied the 70-kDa cell surface component that binds to hepatic sinusoidal endothelial cells in a Ca2+-dependent manner as annexin VI. Cytofluor ographic analysis indicated that annexin VI was expressed on the cell surface in slightly higher amounts on highly metastatic RAW117 cells, and it was not removable by EDTA treatment. Anti-annexin VI antibodies inhibited the adhesion of RAW117 cells to fixed or unfixed murine hep atic sinusoidal endothelial cells by similar to 40%, indicating a role for annexin VI in mediating a portion of the Ca2+-dependent RAW117 ce ll adhesion to target liver microvessel endothelial cells. (C) 1994 Ac ademic Press,Inc.