Angiogenesis plays an important role in breast cancer growth and metastasis. Multiple adhesion molecules have been shown to perform critical functions in the process of angiogenesis. In this study, we analyzed 15 benign and 22 malignant estrogen-receptor-negative and estrogen-receptor-positive breast specimens for the presence of the endothelial cell adhesion molecules E-selectin and P-selectin. We found that E-selectin's expression was increased in the malignant breast tumors compared with their benign counterparts (23.86% of blood vessels versus 2.47%; P = 0.0005). Furthermore, E-selectin staining was found to be significantly increased in the estrogen-receptor-negative carcinomas compared with the estrogen-receptor-positive ones (P = 0.005). In vitro findings strongly correlated with the in vivo findings and showed a higher degree of E-selectin induction in endothelial cells exposed to conditioned media from estrogen-receptor-negative breast cancer cell lines than from estrogen-receptor-positive ones. The degree of E-selectin induction correlated with the amount of interleukin-1 alpha in the tumor-conditioned media. Neutralizing antibodies to interleukin-1 alpha significantly inhibited the E-selectin expression in endothelial cells exposed to tumor-conditioned media. The results indicate that the endothelial E-selectin expression during angiogenesis is related to breast carcinoma progression in vivo and that this component of angiogenesis may be due directly to tumor-cell-secreted interleukin-1 alpha.

OBJECTIVE: E-selectin is an endothelial cell-specific membrane glycoprotein that participates in leukocyte adhesion and has also been suggested to function in angiogenesis. To gain further insights into E-selectin, we analyzed E-selectin polypeptide in proliferating versus quiescent bovine capillary endothelial cells and its expression as a function of the cell cycle. METHODS: E-selectin polypeptide was analyzed by immunoadsorption from 35Scysteine-labeled endothelial cells, by enzyme-linked immunosorbent assay, and by fluorescence-activated cell sorting. The distribution of endothelial cells in Gzero/G1, S, and G2/M phases of the cell cycle was determined using propidium iodide staining of DNA. RESULTS: E-selectin was upregulated in subconfluent proliferating bovine capillary endothelial cells compared to confluent quiescent cultures. The upregulation was independent of activation in that E-selectin was further increased by treatment with tumor necrosis factor alpha or lipopolysaccharide. In contrast to E-selectin, P-selectin and platelet-endothelial cell adhesion molecule-1 did not appear to be regulated by the growth state of the endothelial cells. The distribution of E-selectin-positive cells in GzeroG1, S, and G2/M phases of the cell cycle differed from E-selectin-negative cells in that more of the E-selectin-positive cells were in G2 and M. CONCLUSIONS: Increased E-selectin expression under noninflammatory conditions is correlated with cellular proliferation and G2/M phases of the cell cycle. The expression of E-selectin in proliferating endothelial cells in vitro is consistent with the presence of E-selectin in proliferating endothelial cells in vivo (Kräling et al. [18]).