Cellular adhesion of sialyl-Lewis-a(SLea)-positive pancreas carcinoma to endothelial cells (EC) is augmented by activation of EC via up-regulated E-selectin expression on EC. Co-cultivation of pancreas-carcinoma cells, PCI-24, with human umbilical-vein endothelial cells (HUVEC) for 5 hr at the PCI-to-HUVEC ratio of 1:10 induced E-selectin expression on the endothelial-cell surface, augmenting SLea-positive pancreas-carcinoma cell attachment with HUVEC. Culture supernatants of 6 tested pancreas-carcinoma cell lines contained soluble, E-selectin-inducing factor(s). The E-selectin-inducing effect by the supernatants was blocked by the protein-kinase-C inhibitor, H7. Antibodies against SLea and E-selectin but not SLex or ICAM-I blocked the increased pancreas-carcinoma-to-endothelial attachment. Paraformaldehyde(PFA)-fixed PCI-24 cells also induced E-selectin on vascular endothelial cells upon direct contact with endothelial cells, indicating the presence of a membrane-bound form. The 6 pancreas-carcinoma lines all produced IL-1α mRNA and protein but not IL-1β or TNF-α protein and/or mRNA Absorption of IL-lα from the supernatants by IL-lα-specific antibody almost completely abolished E-selectin-inducing activity. Anti-IL-lα antibody also abolished the E-selectin-inducing activity of PFA-fixed PCI. IL-1α production by PCI cells was up-regulated by TNF-α. These observations suggest that substance(s) produced by pancreas-carcinoma cells, in this case, IL-1α, may contribute to pancreas-carcinoma-cell colonization in non-inflamed, distant locations in vivo, by activating vascular endothelial cells.