Histone deacetylation is the primary epigenetic mechanism for silencing of tumor suppressor gene ‐ Tissue Factor Pathway Inhibitor‐2 in hepatocellular carcinoma cells

Tissue factor pathway inhibitor‐2 (TFPI‐2) is a critical tumor suppressor gene that is frequently silenced in primary hepatocellular carcinoma (HCC). Inactivation of TFPI‐2 is associated with increased tumor growth and metastasis in HCC. We investigated the role of epigenetic regulation in TFPI‐2 expression using 5‐azacytidine (5‐AZA, a DNA methyltransferase inhibitor) and trichostatin A (TSA, a histone deacetylase inhibitor) in HCC cell lines. Both 5‐AZA and TSA upregulated TFPI‐2 expression; however, TSA‐mediated reactivation of TFPI‐2 was more robust, suggesting that histone deacetylation may be the predominant mechanism of TFPI‐2 silencing. In further studies, TSA greatly increased the acetylation of histones at the TFPI‐2 promoter region, as well as the binding of relevant transcription factors and RNA polymerase II at the transcription start site for TFPI‐2. Co‐treatment with Garcinol, a histone acetyltransferase inhibitor, substantially reduced the TSA‐induced upregulation of TFPI‐2, implying that the histone acetyltransferase‐histone deacetylase (HAT‐HDAC) balance critically regulates TFPI‐2 expression in HCC cells. Overall, our data suggest that histone deacetylation is the likely primary mechanism underlying the silencing of TFPI‐2 in HCC. HDAC inhibitors such as TSA are thus, potential chemotherapeutic agents in HCC. Supported by HRSA‐C76HF19368(SB).