Given studies showing Jagged1 (a Notch ligand) expression in macrophages50,51, and Notch1-mediated induction of MenaINV expression, which is required for intravasation in association with macrophages at tumor microenvironment of metastasis (TMEM)19, we investigated whether Notch signaling plays a role during the stemness induction by macrophages that we observed in mammary tumors in vivo. The gene discussed is NOTCH1; the disease is breast cancer.