TNFSF15 is also able to inhibit the differentiation of bone marrow-derived endothelial progenitor cells (EPCs) into endothelial cells and the incorporation of EPC into the tumor neovasculature.74,75 Interestingly, TNFSF15 does not induce apoptosis in early-stage EPC, unless these cells have differentiated into endothelial cells. The gene discussed is TNFSF15; the disease is neoplasm.