We found that MDSCs infiltrate into tumors and promote tumor angiogenesis by expressing high levels of matrix metalloproteinase 9 (MMP9) and by directly incorporating into tumor endothelium.(21) Furthermore, MDSCs produce large quantities of TGF-β and a number of MMPs, including MMP13, MMP14, and MMP2. This evidence concerns the gene MMP9 and neoplasm.