HDAC9 and cancer: CD13 (or aminopeptidase N, APN) is a transmembraneglycoproteinwhose elevated expression in tumors is related to a major invasiveand metastatic behavior. The combinationthat could be given by the CD13 inhibition with the antiproliferativeand cytotoxic effects of HDAC inhibition could result in improvedefficacy in cancer treatment. Jia etal.