HDAC9 and prostate cancer: It is also possible that the effect of PEITC on the epigenetic signature is cell-type dependent, which may explain why, in an earlier report, PEITC functioned as a HDAC inhibitor to activate the p21 gene in prostate cancer cells [53], while in our observations, chromatin and gene expression changes associated with PEITC exposure in colon cancer cells were repressive in nature.