Histone deacetylase inhibitor (SAHA) and repression of EZH2 synergistically inhibit proliferation of gallbladder carcinoma

Abstract

Polycomb group protein EZH2, frequently overexpressed in malignant tumors, is the catalytic subunit of polycomb repressive complex 2 (PRC2). PRC2 interacts with HDACs in transcriptional silencing and relates to tumor suppressor loss. We examined the expression of HDAC isoforms (HDAC 1 and 2) and EZH2, and evaluated the possible use of HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) and EZH2 repressor for gallbladder carcinoma. We used 48 surgically resected gallbladders and cultures of human gallbladder epithelial cells (HGECs), gallbladder carcinoma (TGBC2TKB), and cholangiocarcinoma (HuCCT-1 and TFK-1) cell lines for examination. Immunohistochemically, EZH2 was overexpressed in gallbladder carcinoma, especially poorly differentiated carcinoma, but not in normal epithelium. In contrast, HDAC1/2 were expressed in both carcinoma and normal epithelium in vivo. This pattern was verified in cultured cells; EZH2 was highly expressed only in TGBC2TKB, whereas HDAC1/2 were expressed in HGECs and TGBC2TKB. Interestingly, SAHA treatment caused significant cell number decline in three carcinoma cells, and this effect was synergized with EZH2 siRNA treatment; however, HGECs were resistant to SAHA. In TGBC2TKB cells, the expression of EZH2 and HDAC1/2 were decreased by SAHA treatment, and p16 INK4a, E-cadherin, and p21 were simultaneously activated; however, no such findings were obtained in HGECs, suggesting that the effect of SAHA depends on the EZH2-mediated tumor suppressor loss. In conclusion, this study suggests a possible mechanism by which carcinoma cells but not normal cells are sensitive to SAHA and indicates the efficacy of this new anticancer agent in combination with EZH2 repression in gallbladder carcinoma. (Cancer Sci 2010; 101: 355-362) G allbladder carcinoma is an aggressive and depressing disease, particularly affecting older people and women. (1)(2)(3) It is usually difficult to detect gallbladder carcinoma in the early stage, because characteristic signs or symptoms are lacking and high risk factors have not been established in a majority of patients. Although complete surgical resection is the only curative therapy, invasion to surrounding organs or metastases is usually found in a majority of gallbladder carcinoma patients at the time of diagnosis. The current chemotherapy for patients with advanced gallbladder carcinoma is limited, and the development and exploration of new anticancer agents is necessary. (4,5) Polycomb group proteins are epigenetic chromatin modifiers involved in cancer development.(6,7) PcG proteins exist in at least two separate protein complexes, polycomb repressive complex 2 (PRC2) and PRC1. The PRC2 complex involves embryonic ectoderm development and EZH2. (8,9) EZH2 is a transcriptional repressor involved in controlling cell growth and proliferation and an abnormal expression of EZH2 may be involved in the tumorigenesis process and provides proliferative advantages to eukaryotic cells through interaction with the pathways of key elements that control cell growth arres...

Transcriptional regulation of cellular senescence

“…The search for more specific epigenetic-based therapies has identified the histone methyltransferase inhibitor 3-deazaneplanocin A as having efficacy in decreasing EZH2 levels. This results in the inhibition of H3K27 methylation, the reactivation of polycomb target genes, including INK4A, and the induction of growth inhibition and apoptosis in tumour cells in vitro (Tan et al, 2007;Fiskus et al, 2009;Puppe et al, 2009;Hayden et al, 2010;Yamaguchi et al, 2010). However, the fact that EZH2 is known to be mutated and inactivated in myeloid disorders (Ernst et al, 2010) suggests that Transcriptional regulation of cellular senescence F Lanigan et al EZH2-targeting drugs may only be effective in a subset of tumour types.…”

Sodium valproate blocks the transforming growth factor (TGF)-β1 autocrine loop and attenuates the TGF-β1-induced collagen synthesis in a human hepatic stellate cell line

“…Recent studies have shown that HDACis have the potential to inhibit carcinogenesis and fibrogenesis (2,(9)(10)(11)(12)(13)(14)(15). VPA, a semiselective HDACi (20), is widely prescribed for patients with epilepsy and psychiatric disorders and well tolerated by the majority of patients (21,22).…”

“…Histone acetylation and deacetylation is controlled by histone acetyltransferases and histone deacetylases. In recent years, histone deacetylase inhibitors (HDACis) showed anti-cancer activities and are, therefore, of clinical interest (9)(10)(11)(12). There are also several reports showing an antifibrogenic effect of HDACis, but the underlying mechanism is still unclear (2,(13)(14)(15).…”

New Molecular Targets for Anti-Angiogenic Therapeutic Strategies

“…Although EZH2 is the catalytic subunit of the polycomb repressive complex 2 (PRC2), it is accompanied by other components including SUZ12, EED, and YY1. Consequently, treatment with DZNep results in the depletion of each of these PRC2 complex proteins and blocks the associated histone H3 lysine 27 methylation (Chase & Cross, 2011;Fiskus et al, 2009;Yamaguchi et al, 2010). Therefore, DZNep may interfere with normal physiological processes that require methyl transfer.…”

“…www.intechopen.com (Chase & Cross, 2011;Fiskus et al, 2009;Yamaguchi et al, 2010). Although EZH2 is the catalytic subunit of the polycomb repressive complex 2 (PRC2), it is accompanied by other components including SUZ12, EED, and YY1.…”