Monocyte exosomes have been shown to possess pro-coagulant properties that might contribute to endothelial cell-mediated thrombosis, T cell exosomes can promote tumor angiogenesis by activating VEGF signaling and induce cancer cell invasion by increasing the production of MMP-9, and exosomes from polarized macrophages can transfer MiRNAs to tumor cells that target anti-metastatic genes. This evidence concerns the gene MMP9 and cancer.