Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10758196 | Biochemical and Biophysical Research Communications | 2013 | 6 Pages |
Abstract
Triiodothyronine (T3) is a potent form of thyroid hormone mediates several physiological processes including cellular growth, development, and differentiation via binding to the nuclear thyroid hormone receptor (TR). Recent studies have demonstrated critical roles of T3/TR in tumor progression. Moreover, long-term hypothyroidism appears to be associated with the incidence of human hepatocellular carcinoma (HCC), independent of other major HCC risk factors. Dickkopf (DKK) 4, a secreted protein that antagonizes the canonical Wnt signaling pathway, is induced by T3 at both mRNA and protein levels in HCC cell lines. However, the mechanism underlying T3-mediated regulation of DKK4 remains unknown. In the present study, the 5â² promoter region of DKK4 was serially deleted, and the reporter assay performed to localize the T3 response element (TRE). Consequently, we identified an atypical direct repeat TRE between nucleotides â1645 and â1629 conferring T3 responsiveness to the DKK4 gene. This region was further validated using chromatin immunoprecipitation (ChIP) and electrophoretic mobility shift assay (EMSA). Stable DKK4 overexpression in SK-Hep-1 cells suppressed cell invasion and metastatic potential, both in vivo andin vitro, via reduction of matrix metalloproteinase-2 (MMP-2) expression. Our findings collectively suggest that DKK4 upregulated by T3/TR antagonizes the Wnt signal pathway to suppress tumor cell progression, thus providing new insights into the molecular mechanism underlying thyroid hormone activity in HCC.
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Authors
Hsiang-Cheng Chi, Chen-Hsin Liao, Ya-Hui Huang, Sheng-Ming Wu, Chung-Ying Tsai, Chia-Jung Liao, Yi-Hsin Tseng, Yang-Hsiang Lin, Cheng-Yi Chen, I-Hsiao Chung, Tzu-I Wu, Wei-Jan Chen, Kwang-Huei Lin,