Furthermore, exosomes containing IL-15 were shown to be taken up by brain ECs and functionally implicated in full-blown brain metastasis of Nalm-6 BCP-ALL leukemia cells in mice [134], whereas exosomes from ALL cell lines facilitated transendothelial migration across a BCSFB model based on immortalized CP epithelial cells. This evidence concerns the gene IL15 and leukemia.