MMP9 and breast cancer: Decreasing O-GlcNAcylation of this protein via OGT inhibition or knockdown in breast cancer cells increases both SIRT1 level and activity, thereby regulating forkhead box M1 (FOXM1), MMP-2, and MMP-9 protein level, and modulating breast cancer cell invasive and metastatic capability in vitro and in vivo (42).