AR and prostate cancer: We found that in vitro treatment with a histone deacetylase inhibitor trichostatin A (TSA) could significantly increase the HNF4α expression in an androgen receptor (AR)-negative (PC-3) and two AR-positive (LNCaP, ARCaPM) prostate cancer cell lines in a time-dependent manner (Fig. 2a, b; Supplementary Fig. S4a).