It has been reported that CYP24A1 expression is negatively correlated with the methylation of the CYP24A1 promoter in prostate and lung cancer, in vivo and in vitro [75,83] Thirdly, the suppression of DNA methyltransferase (DNMT) or histone deacetylase (HDAC) elevated CYP24A1 expression in colon and lung cancer. The gene discussed is HDAC9; the disease is lung cancer.