Endothelial cells secrete exosomes rich in vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), angiopoietin-1 (ANGPT1), ephrin A3 (EFNA3), matrix metallopeptidase 2 (MMP2), matrix metallopeptidase 9 (MMP9) and azurocidin 1 (AZU1), which can stimulate the production of adjacent tumour blood vessels [78–82]. The gene discussed is MMP9; the disease is neoplasm.