title: Dickkopf 4 positively regulated by the thyroid hormone receptor suppresses cell invasion in human hepatoma cells.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors: Department of Biochemistry, School of Medicine, Chang-Gung University, Taoyuan, Taiwan.
authors: Chen-Hsin
authors: CH
authors: Liao
authors: Chau-Ting
authors: CT
authors: Yeh
authors: Ya-Hui
authors: YH
authors: Huang
authors: Sheng-Ming
authors: SM
authors: Wu
authors: Hsiang-Cheng
authors: HC
authors: Chi
authors: Ming-Ming
authors: MM
authors: Tsai
authors: Chung-Ying
authors: CY
authors: Tsai
authors: Chia-Jung
authors: CJ
authors: Liao
authors: Yi-Hsin
authors: YH
authors: Tseng
authors: Yang-Hsiang
authors: YH
authors: Lin
authors: Cheng-Yi
authors: CY
authors: Chen
authors: I-Hsiao
authors: IH
authors: Chung
authors: Wan-Li
authors: WL
authors: Cheng
authors: Wei-Jan
authors: WJ
authors: Chen
authors: Kwang-Huei
authors: KH
authors: Lin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000473:pathology / Q000503:physiopathology*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology*; D049109:Cell Proliferation; D018450:Disease Progression; D015536:Down-Regulation; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000502:physiology*; D008113:Liver Neoplasms / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D051379:Mice; D008819:Mice, Nude; D008875:Middle Aged; D011988:Receptors, Thyroid Hormone / Q000502:physiology*; D012189:Retrospective Studies; D015398:Signal Transduction / Q000502:physiology; D014183:Transplantation, Heterologous; D051153:Wnt Proteins / Q000502:physiology; D051176:beta Catenin / Q000502:physiology
chemical_list: C442333:DKK4 protein, human; D036341:Intercellular Signaling Peptides and Proteins; D011988:Receptors, Thyroid Hormone; D051153:Wnt Proteins; D051176:beta Catenin