The histone-deacetylase inhibitor Trichostatin A blocks proliferation and triggers apoptotic programs in hepatoma cells

Background/Aims: Effective treatment for hepatocellular carcinoma is urgently needed. The histone-deacetylase inhibitor Trichostatin A (TSA) was shown to induce apoptosis in non-hepatic cells at submicromolar concentrations. However, the effect of TSA on hepatoma cells is unknown. Methods: The hepatoma cells HepG2, MH1C1, Hepa1–6 and Hep1B as well as human fibroblasts (control cells) were exposed to TSA (10−6 to 10−9 M). Cell proliferation was assessed by measuring DNA-synthesis and cell numbers. Apoptosis was quantified by flow cytometry and by the TdT-mediated dUTP nick-end labeling method. Expression patterns of cell cycle- and/or apoptosis-associated p27, p21cip/waf, bax, bcl-2, cyclin A and (pro)-caspase 3 were studied using quantitative Western blotting. Activation of caspase 3 was analyzed via a colorimetric assay. Results: 10−6 M TSA inhibited DNA-synthesis by 46% (HepG2) to 64% (MH1C1) after 24 h, inducing a G2/M-phase arrest and apoptosis. TSA increased activation of caspase 3 and expression of cyclin A, p2lcip/waf, bax and (pro)-caspase 3, while bcl-2 was downregulated. Human fibroblasts remained unaffected. Conclusions: TSA inhibits hepatoma cell growth in vitro, which are otherwise particularly resistant to chemotherapy. Its anti-proliferative activity is paralleled by a comparable rate of apoptosis. TSA may be a promising agent for treatment of hepatocellular carcinoma in vivo.