MMP9 and neoplasm: Furthermore, rVP1 also upregulates autophagy in tumor cells by increasing the phosphorylation levels of mitogen-activated protein kinase 3 (MAPK3)/extracellular signal-regulated kinase 1 (ERK1) and mitogen-activated protein kinase 1/extracellular signal-regulated kinase 2 (MAPK1/ERK2) and the activity of matrix metalloproteinase 9 (MMP9) and then promotes the migration of macrophages.