The involvement of the sLe-a selectin ligand in the extravasation of human colorectal carcinoma cells

The extravasation of tumor cells is a pivotal stage in the formation of hematogenous metastasis. An interaction of selectins expressed on endothelial cells and selectin ligands expressed by tumor cells has been implicated to play a role in extravasation. In the present study we used a human-mouse model to prove the hypothesis that the selectin ligand sialyl Lewis-a (sLe-a) is indeed involved in the in vivo extravasation of colorectal carcinoma (CRC) cells. The results indicated that highly metastatic CRC cells expressing high levels of sLe-a extravasate more efficiently than non-metastatic CRC cells expressing low levels of sLe-a. It was also demonstrated that down regulating the expression levels of sLe-a in CRC cells by genetic manipulations, significantly reduced CRC extravasation. Non-specific effects of these manipulations were ruled out. The results of this study indicate that the arrest and adhesion of CRC cells, and possibly of other types of cancer cells as well, to endothelium depend on the expression of the selectin ligand sLe-a by the tumor cells.