BETA-1 INTEGRINS MEDIATE TUMOR-CELL ADHESION TO QUIESCENT ENDOTHELIAL-CELLS IN-VITRO

Metastatic spread of some solid tumours is thought to depend upon the adhesion of tumour cells to the vascular endothelium followed by extra vasation into surrounding tissues. We investigated the role of beta 1 integrins in the adhesion of the breast adenocarcinoma cell line MDA-M B-231 and the melanoma cell line RPMI-7951 to quiescent human umbilica l vein endothelial cells (HUVEC) in vitro. In the course of adhesion a ssays, tumour cells were observed to adhere to quiescent HUVEC monolay ers, particularly at endothelial cell-cell junctions. Immunohistochemi stry revealed concentration of beta 1 integrin expression at these sit es. Adhesion was reduced by pretreatment of either tumour cells or HUV EC with antibodies against beta 1 integrins. Simultaneous treatment of HUVECs and tumour cells with these antibodies produced an additive bl ocking effect, consistent with a heterotypic adhesion mechanism. Our d ata suggest that tumour cell and endothelial beta 1 integrins may play a crucial role in the arrest and migration of tumour cells through th e vascular endothelium in the absence of endothelial 'activation'.