Study the Role of Thyroid Hormone Receptors during Hepatocarcinogenesis in Transgenic Mice

Recently, several reports indicated that a significantly elevated risk for the association between hypothyroidism and hepatocellular carcinoma (HCC) in women, which was independent of established HCC risk factors. Additionally, hypothyroidism and low-normal free T4 are related with an increased risk of breast cancer in postmenopausal women. Martínez-Iglesias also reported that hypothyroidism enhances tumor invasiveness and the development of metastasis. These data indicate that thyroid hormone receptors (TRs) may play a tumor-suppressor role in normal physiological conditions. TRs possibly lose their suppressor function in the hypothyroidism condition (without T3), thus inducing cancer. Therefore, questions arise pertaining to the role of TRs during tumorigenesis and the nature of the underlying mechanism. To fulfill the aim, this study is to investigate the potential roles of TR-regulated miRNA participating in HCC tumorigenesis. Several steps of study will be designed: miRNA screening, target protein determination, function characterization of candidate miRNAs or their targets using cellular and animal models, and clinical association study. Further, to determine what kind of miRNAs and their target regulated by TR, the role of TR in hepato-carcinogenesis and cancer progression will be established. The HBx protein has been strongly implicated in the carcinogenesis of HCC. HBx transgenic mice, which developed HCC at around 14 to 16 months of age. We will establish hypothyroidal, hyperthyroidal, and euthyroidal (normal) conditions in the HBX transgenic mice to determine the role of TR during hepato-carcinogenesis. We propose five specific aims to test our hypothesis. Specific Aim 1: Establishment of a various thyroidal status in transgenic mice to determine the role of TRs. Specific Aim 2: To analyze the role of TRs and signaling pathways, global profiling of TR-regulated miRNAs in the early (~14 month) or late stage (~16 month) of HCC tissues, compared with their adjacent normal tissues by using mouse miRNA array analysis. The bioinformatics analytical method will be predicted maps of aberrantly expressed networks of novel miRNAs associated with the cancer phenotype. Specific Aim 3: The target proteins of miRNAs will be identified using iTRAQ labeling after basic reverse-phase HPLC and compared with Target Scan, PicTar or miRbase. Specific Aim 4: Functional study of the role of TR regulated miRNAs or their targets by either overexpression or reduced expression in vitro or in vivo. Specific Aim 5: To determine the clinical significance of TR regulated miRNAs in human HCC. The clinical correlation or significance will be established. Specific Aim 6: To develop the therapeutic anti-miRNA strategy to reduce the HCC risk. If TR-regulated miRNA up-regulated in HCC, we will develop an anti-miRNA strategy to inhibit tumor growth. Significance of the proposed research: (1) it will offer an opportunity to identify TR-regulated miRNAs in HCC and (2) it will provide fundamental knowledge to explore the biological roles of TR-regulated miRNAs in HCC. The miRNAs newly identified in this study will be used for diagnosis and prognosis, or for the future development of novel therapeutic targets.

Project ID:PC10008-0918
External Project ID:NSC100-2321-B182-005