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Dickkopf 4 positively regulated by the thyroid hormone receptor suppresses cell invasion in human hepatoma cells
Author(s) -
Liao ChenHsin,
Yeh ChauTing,
Huang YaHui,
Wu ShengMing,
Chi HsiangCheng,
Tsai MingMing,
Tsai ChungYing,
Liao ChiaJung,
Tseng YiHsin,
Lin YangHsiang,
Chen ChengYi,
Chung IHsiao,
Cheng WanLi,
Chen WeiJan,
Lin KwangHuei
Publication year - 2012
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1002/hep.24740
Subject(s) - biology , wnt signaling pathway , transfection , cancer research , cell growth , microbiology and biotechnology , cell culture , signal transduction , genetics
Thyroid hormone (T 3 ) mediates cellular growth, development, and differentiation by binding to the nuclear thyroid hormone receptor (TR). Recent studies suggest that long‐term hypothyroidism is associated with human hepatocellular carcinoma (HCC) independent from other major HCC risk factors. Dickkopf (DKK) 4, a secreted protein, antagonizes the Wnt signal pathway. In this study, we demonstrate that T 3 may play a suppressor role by inducing DKK4 expression in HCC cells at both the messenger RNA (mRNA) and protein levels. DKK4 was down‐regulated in 67.5% of HCC cancerous tissues. The decrease in DKK4 levels was accompanied by a concomitant decrease in TR protein levels in the matched cancerous tissues in 31% of tissues compared by immunoblotting with the adjacent noncancerous tissues. Further, TR and DKK4 expression levels were positively correlated in both normal and cancerous specimens by tissue array analysis. In function assays, stable DKK4 transfected into J7 or HepG2 cells decreased cell invasion in vitro . Conversely, knocking down DKK4 restores cell invasiveness. DKK4‐expressing J7 clones showed increased degradation of β‐catenin, but down‐regulation of CD44, cyclin D1, and c‐Jun. To investigate the effect of DKK4 and TR on tumor growth in vivo , we established a xenograft of J7 cells in nude mice. J7‐DKK4 and J7‐TRα1 overexpressing mice, which displayed growth arrest, lower lung colony formation index, and smaller tumor size than in control mice, supporting an inhibitory role of DKK4 in tumor progression. Conclusion : Taken together, these data suggest that the TR/DKK4/Wnt/β‐catenin cascade influences the proliferation and migration of hepatoma cells during the metastasis process and support a tumor suppressor role of the TR. (H epatology 2012)