Induction of Matrix Metalloprotease Gene Expression in an Endothelial Cell Line by Direct Interaction with Malignant Cells

Mouse endothelial TKD2 cells in the monolayer were co-cultured with various human cell lines for 24 hr, and the expressions of several secreted MMPs and cell adhesion molecules were examined by real-time RT-PCR using mouse-specific primers. Co-culture with normal fibroblasts did not elicit the expression of these molecules, but co-culture with cancer cells induced the expression of MMP-3, -9, and -10 mRNA in endothelial cells and in normal mouse embryonic fibroblasts. The induction of MMP mRNAs was dependent on direct cell adhesion since a separate culture of A549 cells in Boyden chambers did not induce MMP mRNAs, and a neutralizing antibody against VLA-4 abolished the induction. Intracellular ROS levels increased in TKD2 cells following adhesion to cancer cells. ROS scavengers decreased the levels of MMP induction, and roterone, an inhibitor of mitochondrial complex 1, strongly suppressed the induction of MMP-3, -9, and -10. These results indicate that the adhesion of cancer cells to endothelial cells activates several distinct signaling pathways to induce the MMP gene expression.