One possible explanation for this observation is that some of the genes that respond to ETS1 code for specific proteases, including urokinase-type plasminogen activator [38,39,40,41,42] and matrix metalloproteinases MMP-1 and MMP-9, which modify the extracellular matrix, making it easier for tumor cells to invade and increasing their capacity to spread. Here, MMP9 is linked to neoplasm.