TUMOR-CELL SURFACE ALPHA-4-BETA-1 INTEGRIN MEDIATES ADHESION TO VASCULAR ENDOTHELIUM - DEMONSTRATION OF AN INTERACTION WITH THE N-TERMINAL DOMAINS OF INCAM-110/VCAM-1

Hematogenous metastasis involves adhesive interactions between blood-borne tumor cells and the vessel wall. By the use of in vitro assays, the adhesion of human melanoma, osteosarcoma, and kidney carcinoma (but not colon carcinoma) cell lines was shown to involve thecytokine-inducible endothelial cell surface protein inducible cell adhesion molecule 110 (INCAM-110) and the alpha-4-beta-1 integrin, molecules normally involved in endothelial-leukocyte interactions. Tumor adhesion to human endothelial cell monolayers was increased 1.9- to 8.2-fold by endothelial activation with the cytokine tumor necrosis factor (TNF) and inhibited by the anti-INCAM-110 monoclonal antibody (mAb) E1/6. Each of these tumor cells expressed members of the beta-1 integrin family of adhesion molecules, and antibodies to the alpha-4 and beta-1 integrin subunits inhibited tumor-endothelial adhesion (48-87% inhibition). A cDNA encompassing the three N-terminal Ig-like domains of vascular cell adhesion molecule 1 (VCAM-1) encoded a protein recognized by the anti-INCAM-110 mAb E1/6 and, when captured onto plastic, supported melanoma cell adhesion by an alpha-4 integrin-dependent mechanism. In contrast to mAb E1/6, a second anti-INCAM-110 mAb Hu8/4 neither inhibited adhesion to activated endothelium nor bound the first three Ig-like domains of INCAM-110/VCAM-1. These data indicate that the adherence of several human tumors to activated endothelium is mediated by an interaction of alpha-4-beta-1 integrin and the N-terminal Ig-like domains of endothelial INCAM-110/VCAM-1. Tumor acquisition of the alpha-4 integrin subunit and endothelial expression of INCAM-110 may affect the frequency and distribution of metastasis.