Abstract
BACKGROUND: Lung metastases to the brain are common secondary cancers, representing over 50% of fatal complications of systemic cancer. Metastasis of cancer cells involves multiple steps including intravasation, cancer cell-endothelial rolling and adhesion, extravasation and cerebral colonization. Here, we focused on metastatic Non-Small Cell lung cancer cells adhesion to brain endothelial cells. Specifically, we investigated the role of CD15 in lung cancer and its interaction with E-selectin and brain endothelial cells adhesion. METHODS: Five lung cancer cell lines and one brain endothelial cell line (hCMEC/D3) were used (two primary, COR-L105 and A549; one lymph node lung metastatic cell line, NCI-H1299 and two biopsied secondary lung to brain metastatic cultures). Western blot (WB), immunocytochemistry (ICC) and flow cytometric analysis were used to characterise CD15 expression. To induce E-selectin, endothelial cells were treated with TNF-a. Qualitative and quantitative tumour cell-endothelial adhesion assays and live cell image microscopy were conducted, followed by antibody blocking experiments. RESULTS: All cell lines expressed detectable CD15, as determined by WB, flow cytometry and ICC, with the lung cancer to lymph node cell line expressing the highest, followed by lung to brain cell lines. E-selectin expression was significantly increased in the brain endothelial cell line (p < 0.001) with detectable levels in lung cancer cell lines. There was a significant increase in lung cancer adhesion to brain endothelium exposed to TNFa (P < 0.001); the highest increase seen in the lung-lymph node cells followed by both the lung-brain cells and the primary lung cancer cell line (A549). This adhesion was completely blocked by co-treatment of CD15 antibodies compared to IgM isotype controls. CONCLUSIONS: CD15 may play a significant role in lung cancer cell adhesion to brain endothelium.We postulate that by interfering with CD15 homodimer and heterodimer interactions, adhesion of circulating lung cancer cells to the blood brain barrier would be prevented.