To test whether JAG1 expressed on breast cancer cells could induce tube formation in endothelial cells via direct contact, we co-cultured EA.hy926 endothelial cells with various MDA-MB-231 clones and found that co-culture of MDA-MB-231 cells but not MDA-MB-231-2A2 cells induced the formation of tube-like structure (Figure 7A). The gene discussed is JAG1; the disease is breast cancer.