MMP9 and neoplasm: Among the MIR4435-2HG/hsa-miR-1-3p/MMP9/hsa-miR-29-3p/DUXAP8 ceRNA network axis components, MMP9 is a member of the matrix metalloproteinase (MMP) family, a class of metal ion-dependent proteases that increases the invasive and migratory ability of tumor cells because MMPs degrade a variety of proteins in the cell periphery [25].