The present study is designed to assess if exosomes released from Chronic Myelogenous Leukemia (CML) cells may modulate angiogenesis. We have isolated and characterized the exosomes generated from LAMA84 CML cells and demonstrated that addition of exosomes to
human vascular endothelial cells (HUVEC) induces an increase of both ICAM-1 and VCAM-1 cell adhesion molecules and interleukin-8 expression. The stimulation of cell-cell adhesion
molecules was paralleled by a dose-dependent increase of adhesion of CML cells to a HUVEC
monolayer. We further showed that the treatment with exosomes from CML cells caused an increase in endothelial cell motility accompanied by a loss of VE-cadherin and β-catenin from the
endothelial cell surface. Functional characterization of exosomes isolated from CML patients
confirmed the data obtained with exosomes derived from CML cell line. CML exosomes caused reorganization into tubes of HUVEC cells cultured on Matrigel. When added to Matrigel plugs in vivo, exosomes induced ingrowth of murine endothelial cells and vascularization of the Matrigel
plugs. Our results suggest for the first time that exosomes released from CML cells directly affect endothelial cells modulating the process of neovascularization