Thyroid hormone regulation of miR-21 enhances migration and invasion of hepatoma

Cancer Res. 2013; 73(8):2505-17.

Huang YH1, Lin KH2

1Liver Research Center, Department of Hepato-Gastroenterology, Chang Gung Memorial Hospital, Linkou, Taiwan.

2Department of Biochemistry, College of Medicine, Chang-Gung University, Taoyuan, Taiwan 333

PMID: 23442323

 

Abstract:

BACKGROUND AND AIM: Thyroid hormone receptor (TR) regulates gene expression through binding with thyroid hormone (T3) and T3 response element (TRE) on target gene. In addition, T3 stimulation promotes migration of hepatocellular carcinoma (HCC) cells; however, the underlying mechanism is unknown. Mature miRNA (~22 nucleotides) can either result in degradation or translational repression of target mRNA through perfectly or nearly complementary to 3’ untranslated region (UTR). The aberrant expression of miRNAs in HCC patients has been reported. Whether T3/TR regulated miRNAs enhances HCC migration is discussed.

METHODS: Four HCC cell lines HepG2, Hep3B, J7 and SK-Hep1 are used in the study, and three HCC cells stably expressed TRα1 (HepG2-TRα1, Hep3B-TRα1 and J7-TRα1) are generated. The cDNA microarray and 270 miRNA expression profiles using stem-loop quantitative reverse transcription PCR (qRT-PCR)  assay is used to determine the dysregulation of genes in HepG2-TRα1 in the presence or absence of T3.

RESULTS: The miR-21 overexpressed in HCC was stimulated upon T3 application. T3/TR activates miR-21 through TR binds to native TRE exited in primary miR-21 promoter. Both HCC cell migration and invasion is promoted in miR-21 overexpression or T3 stimulation. Conversely, anti-sense miR-21-repressed cell migration, however, can be rescued by T3. The Rac-controlled regulator of invasion and metastasis, T-cell lymphoma invasion and metastasis 1 (TIAM1) correlates with migration and invasion is then focused after cross-comparison the genes which are miR-21 predicted targets and downregulation by T3. The 3’UTR luciferase reporter assay proves TIAM1 is miR-21 target. The protein expression of TIAM1 is decrease in either miR-21 or T3 stimulation. The consequence of migration and invasion enhancement of HCC in inhibition of TIAM1 expression is similar with miR-21 and T3 stimulation. The hyper- and hypothyroid mice evidence the positive correlation between T3 and miR-21. J7-TRα1 cells are utilized for tail vein assay of cancer metastasis to generate xenograft tumor in hyper- and hypothyroid mice also elucidates negative correlation between T3 (or miR-21) and TIAM1. Another animal tail vein model displays HCC with miR-21 depletion result in increase of TIAM1 expression. The clinical investigation discovered a positive correlation between the tumor/nontumor ratios of TRα1 and miR-21 expression, whereas a negative correlation between miR-21 and TIAM1 expression in HCC patients. In conclusion, the miR-21 stimulation by T3/TR signaling and subsequent TIAM1 suppression promotes HCC cell migration and invasion (Figure 1).

 

SUPPLEMENT:

Despite several miRNAs are aberrantly expressed in HCC, little is known about the mechanism of miRNA been regulated. We are the first group to elucidate miR-21 which is one of overexpressed miRNAs in HCC possesses a native TRE, and the metastatic ability mediated by a T3/TR-miR-21-TIAM1 pathway. This study provides physician a strategy to control T3 or miR21 level of HCC patient maybe an alternative way in anti-HCC therapy.

Kwang-Huei Lin-1

Figure 1. Schematic representative the miR-21 modulated by T3 on cell migration and invasion of HCC. (A) The basal level of TIAM1 protein expresses in absence of T3. (B) In presence of T3, pri-miR-21 containing native TRE that binds with TR and RXR is upregulated. The increase of mature miR-21 then targets TIAM1 3’UTR, repressing TIAM1 expression. Depletion of TIAM1 results in enhancement of migration and invasion of HCC cells.

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