The levels of E-selectin mRNA and protein were analyzed in bovine capillary cells treated with or without the angiogenesis inhibitor AGM-1470 (also known as TNP-470). Cells treated with AGM-1470 had a two- to sevenfold (median fivefold) increase in E-selectin mRNA compared with little or no increase in P-selectin, PECAM-1 and VCAM-1 mRNA. E-selectin protein was also significantly increased after exposure to AGM-1470. In contrast, there was no detectable effect on PECAM-1 protein. The increase in E-selectin mRNA and protein was always greater with subconfluent growing cells than with confluent cells. This apparent resistance of confluent endothelial cells to AGM-1470 may be relevant to its specificity in vivo. The fact that the effect of AGM-1470 on E-selectin is relatively selective for subconfluent growing cells may provide a clue as to how AGM-1470 is able to both reversibly inhibit endothelial cell proliferation in vitro and inhibit tumor growth in vivo without apparent effects to quiescent endothelium.