Breast tumors induce the recruitment of AC133⁺KDR⁺ endothelial precursor cells mobilized by plasma vascular endothelial growth factor

Recent evidence has demonstrated the importance of bone marrow-derived endothelial precursor cells (EPC) in the contribution to postnatal physiological and pathological neovascularization, and in tumor growth and angiogenesis. These cells are recruited undifferentiated; in response to systemic or chemoattractive signals, such as vascular endothelial growth factor (VEGF), they lodge in the growing or lesioned tissue and differentiate into endothelial cells in response to local stimuli and cell–cell interactions. The extent and the significance of the EPC contribution for the growing of most tumors, including breast carcinomas, are still not defined. We analysed the peripheral blood mononuclear cells (PBMNC) of 48 breast cancer patients and found that 16.7% of them have circulating EPC. These cells were detected by RT-PCR expression of AC133 and kinase domain receptor (KDR). Furthermore, using an ELISA assay, we also found an association between circulating AC133⁺KDR⁺ cells and VEGF plasma levels in these patients. We also found AC133 and KDR positivity in breast carcinoma tissues. To our knowledge, this is the first report addressing the recruitment of EPC to breast tumors. Strategies to impair the mobilization and incorporation of EPC into tumors may interfere with the growth of these tumors.