The differences between parental and brain-colonizing cell line-derived exosomes were not very dramatic in the first three proteins; however, Bcl-xL was specifically up-regulated in exosomes from the non-BM breast cancer cell lines.This is in agreement with previous findings associating over-expression of this anti-apoptotic protein with nodal metastasis but not brain metastasis in human breast cancer tumors [54], [55]. This evidence concerns the gene BCL2L1 and breast cancer.