Our data suggests that FKBPL-based peptides in addition to their well-established anti-angiogenic [24, 25] and anti-CSC activity [5] via CD44, are able to inhibit lung metastasis, possibly by modulating the Notch pathway members, DLL4 and Notch 4, within breast cancer, giving these agents a potential competitive advantage. This evidence concerns the gene DLL4 and breast cancer.