Wu SM, Cheng WL, Liao CJ, Chi HC, Lin YH, Tseng YH, Tsai CY, Chen CY, Lin SL, Chen WJ, Yeh YH, Huang CYF, Chen MH, Yeh YC, Lin KH. Negative modulation of the epigenetic regulator, UHRF1, by thyroid hormone receptors suppresses liver cancer cell growth.
Int J Cancer 2015;
137:37-49. [PMID:
25430639 DOI:
10.1002/ijc.29368]
[Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Accepted: 11/12/2014] [Indexed: 12/16/2022]
Abstract
The thyroid hormone, 3,3',5-triiodo-l-thyronine (T3 ), mediates several physiological processes, including embryonic development, cellular differentiation, metabolism and regulation of cell proliferation. Thyroid hormone (T3 ) and its receptor (TR) are involved in metabolism and growth. In addition to their developmental and metabolic functions, TRs play a tumor suppressor role, and therefore, their aberrant expression can lead to tumor transformation. Aberrant epigenetic silencing of tumor suppressor genes promotes cancer progression. The epigenetic regulator, Ubiquitin-like with PHD and ring finger domains 1 (UHRF1), is overexpressed in various cancers. In our study, we demonstrated that T3 negatively regulates UHRF1 expression, both in vitro and in vivo. Our results further indicate that UHRF1 regulation by T3 is indirect and mediated by Sp1. Sp1-binding elements of UHRF1 were identified at positions -664/-505 of the promoter region using the luciferase and chromatin immunoprecipitation assays. Notably, UHRF1 and Sp1 levels were elevated in subgroups of hepatocellular carcinoma patients and inversely correlated with TRα1 expression. Knockdown of UHRF1 expression should therefore provide a means to inhibit hepatoma cell proliferation. Expression of UHRF1 was downregulated by TRs, in turn, relieving silencing of the UHRF1 target gene, p21. Based on the collective findings, we propose that T3 /TR signaling induces hepatoma cell growth inhibition via UHRF1 repression.
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