A MONOCLONAL-ANTIBODY INHIBITS ADHESION TO FIBRONECTIN AND VITRONECTIN OF A COLON-CARCINOMA CELL-LINE AND RECOGNIZES THE INTEGRINS ALPHA(V)BETA(3), ALPHA(V)BETA(5), AND ALPHA(V)BETA(6)

Using whole viable human colon carcinoma HT29 cells as immunogen, we p roduced a monoclonal antibody (mAb) termed 69-6-5. The antibody was fu nctionally selected on its anti-cell-spreading activity. By immunoprec ipitation of surface radiolabeled cell lysates from HT29-D4 cells (an HT29 cell clone), mAb 69-6-5 recognized a molecular complex resembling integrin heterodimers. Sequential immunodepletions with mAb to the in tegrin alpha(v) subunit demonstrated that this complex was composed of alpha(v)-containing integrins. Accordingly, mAb 69-6-5 reacted with i ntegrin alpha(v) beta(3) immunopurified from melanoma cells and integr ins alpha(v) beta(5) and alpha(v) beta(6) immunopurified from pancreat ic carcinoma cells. In cell adhesion assays, the 69-6-5 mAb was able t o inhibit strongly in a dose-dependent manner arginine-glycine-asparti c acid-mediated adhesion of HT29-D4 cells to vitronectin, fibronectin, or ProNectin F but not to laminin or collagen. Immunoprecipitations w ith beta chain-specific antisera indicated that these cells express in tegrins alpha(v) beta(5) (receptor for vitronectin) and alpha(v) beta( 6) (receptor for fibronectin) but neither alpha(v) beta(1) nor alpha(v ) beta(3). In summary, these results indicated that mAb 69-6-5 reacts with several alpha(v) integrins and that it can effectively interfere with the adhesive functions of at least alpha(v) beta(5) and alpha(v) beta(6), which represent the major receptors on HT29-D4 cells responsi ble for their adhesion on vitronectin and fibronectin.