DIM, unlike competitive inhibitors of enzyme activity, causes selective proteasome degradation [185,186] of HDAC class 1 enzymes (HDAC 1, 2, 3, 8) in human colon and prostate cancer cell lines; this new mechanism could be exploited in the clinic with HDAC inhibitors to achieve lower histone acetylation and/or a lower concentration of the necessary HDAC inhibitors. Here, HDAC9 is linked to prostate cancer.