Alteration of integrins by heparin-binding EGF-like growth factor in human breast cancer cells

The adhesion of cancer cells to the vascular endothelium is an important step in the hematogenous metastasis of cancer. Human breast cancer cells adhere to human umbilical vein endothelial cells (HUVECs) through the interaction of E selection on HUVECs and the carbohydrate ligand sialyl Lewisx on the cancer cells. We investigated the alteration of integrin expression on human breast cancer cells, following selectin-mediated initial adhesion to HUVECs. Four cell lines derived from human breast cancer expressed alpha 2-, alpha 3-, alpha 5-, alpha 6- and beta 1-integrins. The expression of alpha 2 beta 1- and alpha 3 beta 1-integrins on BT-20 cells, strongly expressing epidermal growth factor (EGF) receptors, was markedly increased by addition of the heparin-binding EGF-like growth factor (HB-EGF). The expression of alpha 2 beta 1-integrin on SK-BR-3 cells also was increased by the addition of HB-EGF. However, no such effect of HB-EGF on the expression of integrins was observed in T-47D and MCF-7 cells, nor on expression of the EGF receptor. The increase of integrin expression in BT-20 cells was inhibited by the addition of the tyrosine kinase inhibitor genistein. HB-EGF treatment of BT-20 or SK-BR-3 cells resulted in the augmentation of cancer cell adhesion to immobilized collagen. When BT-20 cells were cocultured with HUVECs, a similar level of augmentation of cancer cell adhesion to collagen was observed. The augmentation of cancer cell adhesion to collagen was inhibited by addition of an anti-HB-EGF-neutralizing antibody. Our interpretation of the results described above is that the cancer cells receive stimulation from cytokines, such as HB-EGF, produced by vascular endothelial cells, following the initial adhesion of cancer cells via selectins. This results in a secondary increase in the expression of cell adhesion molecules, such as the beta 1-integrin family, and leads to augmentation in the adhesive activities of cancer cells at the vessel walls. We postulate that these events are the ones involved in the enhanced transmigration of cancer cells to extravascular tissues following the selectin-mediated adhesion to the endothelium.