Surprisingly, trichostatin A (TSA), a classic histone deacetylase that acts on prostate cancer cells, has been found to downregulate the KDM4B protein, causing downregulation of cyclin B1 and upregulation of the caspase-3 and caspase-9 apoptotic proteins, thereby inhibiting the growth of prostate cancer cells and promoting their apoptosis (Zhu et al., 2012). This evidence concerns the gene CASP9 and prostate cancer.