CD15s/CD62E interaction mediates the adhesion of non-small cell lung cancer cells on brain endothelial cells: implications for cerebral metastasis

Expression of the cell adhesion molecule (CAM), Sialyl Lewis X (CD15s) correlates with cancer metastasis, while expression of E-selectin (CD62E) is stimulated by TNF-α. CD15s/CD62E interaction plays a key role in the homing process of circulating leukocytes. We investigated the heterophilic interaction of CD15s and CD62E in brain metastasis-related cancer cell adhesion. CD15s and CD62E were characterised in human brain endothelium (hCMEC/D3), primary non-small cell lung cancer (NSCLC) (COR-L105 and A549) and metastatic NSCLC (SEBTA-001 and NCI-H1299) using immunocytochemistry, Western blotting, flow cytometry and immunohistochemistry in human brain tissue sections. TNF-α (25 pg/mL) stimulated extracellular expression of CD62E while adhesion assays, under both static and physiological flow live-cell conditions, explored the effect of CD15s-mAb immunoblocking on adhesion of cancer cell–brain endothelium. CD15s was faintly expressed on hCMEC/D3, while high levels were observed on primary NSCLC cells with expression highest on metastatic NSCLC cells (p < 0.001). CD62E was highly expressed on hCMEC/D3 cells activated with TNF-α, with lower levels on primary and metastatic NSCLC cells. CD15s and CD62E were expressed on lung metastatic brain biopsies. CD15s/CD62E interaction was localised at adhesion sites of cancer cell–brain endothelium. CD15s immunoblocking significantly decreased cancer cell adhesion to brain endothelium under static and shear stress conditions (p < 0.001), highlighting the role of CD15s–CD62E interaction in brain metastasis.