fluorescence-activated Flow Cytometry. Flow cytometric analysis was performed using FACScan (Becton Dickinson). Cultured cells were stained using the indirect irnmunofluorescence technique with the antibody B27.29

The MUC 1 mucin is expressed on normal breast epithelium and in 90%of breastcancers. Wereportherethat tumor-associated MUC1is a ligand for intercellular adhesion molecule 1 (ICAM-1) Antibodies to ICAM-l and to MUC1 inhibited adhesion of human and transfected mouse MUC1-positive cell lines to human umbilical vein endothelial cell monolayers and immobilized recombinant human ICAM-1-immunoglob ulin fusion protein. Purified MUC1 pretreatment of recombinant human ICAM-1 was an equally effective inhibitor of adhesion. The interaction between MUC1 and ICAM-1 may be critical to the process of bloodborne metastases in breast cancer.