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Growth activation alone is not sufficient to cause metastatic thyroid cancer in a mouse model of follicular thyroid carcinoma.

ABSTRACT: TSH is the major stimulator of thyrocyte proliferation, but its role in thyroid carcinogenesis remains unclear. To address this question, we used a mouse model of follicular thyroid carcinoma (FTC) (TRbeta(PV/PV) mice). These mice, harboring a dominantly negative mutation (PV) of the thyroid hormone-beta receptor (TRbeta), exhibit increased serum thyroid hormone and elevated TSH. To eliminate TSH growth-stimulating effect, TRbeta(PV/PV) mice were crossed with TSH receptor gene knockout (TSHR(-/-)) mice. Wild-type siblings of TRbeta(PV/PV) mice were treated with an antithyroid agent, propylthiouracil, to elevate serum TSH for evaluating long-term TSH effect (WT-PTU mice). Thyroids from TRbeta(PV/PV)TSHR(-/-) showed impaired growth with no occurrence of FTC. Both WT-PTU and TRbeta(PV/PV) mice displayed enlarged thyroids, but only TRbeta(PV/PV) mice developed metastatic FTC. Molecular analyses indicate that PV acted, via multiple mechanisms, to activate the integrins-Src-focal adhesion kinase-p38 MAPK pathway and affect cytoskeletal restructuring to increase tumor cell migration and invasion. Thus, growth stimulated by TSH is a prerequisite but not sufficient for metastatic cancer to occur. Additional genetic alterations (such as PV), destined to alter focal adhesion and migration capacities, are required to empower hyperplastic follicular cells to invade and metastasize. These in vivo findings provide new insights in understanding carcinogenesis of the human thyroid.

SUBMITTER: Lu C

PROVIDER: S-EPMC2851190 | biostudies-literature | 2010 Apr

REPOSITORIES: biostudies-literature

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Growth activation alone is not sufficient to cause metastatic thyroid cancer in a mouse model of follicular thyroid carcinoma.

Lu Changxue C Zhao Li L Ying Hao H Willingham Mark C MC Cheng Sheue-Yann SY

Endocrinology 20100204 4

TSH is the major stimulator of thyrocyte proliferation, but its role in thyroid carcinogenesis remains unclear. To address this question, we used a mouse model of follicular thyroid carcinoma (FTC) (TRbeta(PV/PV) mice). These mice, harboring a dominantly negative mutation (PV) of the thyroid hormone-beta receptor (TRbeta), exhibit increased serum thyroid hormone and elevated TSH. To eliminate TSH growth-stimulating effect, TRbeta(PV/PV) mice were crossed with TSH receptor gene knockout (TSHR(-/- ...[more]

PMID: 20133453

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Project description:Thyroid cancers are the most common malignancy of the endocrine system in humans. To understand the molecular genetic events underlying thyroid carcinogenesis, we have generated a mouse model that spontaneously develops follicular thyroid carcinoma similar to human thyroid cancer (Thrb(PV/PV) mouse). This mutant mouse harbors a dominant-negative mutated thyroid hormone receptor ? (denoted PV). The PV mutation was identified in a patient with resistance to thyroid hormone (TH). Thrb(PV/PV) mice exhibit highly elevated serum thyroid-stimulating hormone levels and increased TH. We have previously shown that thyroid-stimulating hormone is required, but not sufficient to induce metastatic follicular thyroid cancer in Thrb(PV/PV) mice. However, whether the elevated TH also contributes to the thyroid carcinogenesis of Thrb(PV/PV) mice was not elucidated. To understand the role of TH in thyroid carcinogenesis, we blocked the production of TH by treating Thrb(PV/PV) mice with propylthiouracil (Thrb(PV/PV)-PTU mice) and compared the development of thyroid cancer in Thrb(PV/PV)-PTU and untreated Thrb(PV/PV) mice. We found that thyroid tumor growth was reduced by ?42% in Thrb(PV/PV)-PTU mice as compared with Thrb(PV/PV) mice. Analysis by bromodeoxyuridine-nuclear labeling showed decreased incorporation of bromodeoxyuridine in thyroid tumor cells of Thrb(PV/PV)-PTU mice, indicative of decreased tumor cell proliferation. However, cleaved-caspase 3 staining showed no apparent changes in apoptosis of tumor cells in Thrb(PV/PV)-PTU mice. Molecular studies identified a marked attenuation of the PI3K-AKT-?-catenin signaling pathway that led to decreased protein levels of cyclin D2, thereby decreasing tumor cell proliferation in Thrb(PV/PV)-PTU mice. Furthermore, matrix metalloproteinase-2, a downstream target of ?-catenin and a key regulator during tumor invasion and metastasis, was also decreased. Thus, the present study uncovers a critical role of TH in promoting the thyroid carcinogenesis of Thrb(PV/PV) mice via membrane signaling events. Importantly, these findings suggest that anti-thyroid drugs could be considered as possible therapeutic agents of thyroid cancer.

Project description:Molecular mechanisms underlying the pathogenesis and progression of malignant thyroid cancers, such as follicular thyroid carcinomas (FTCs), and how these differ from benign thyroid lesions, are poorly understood. In this study, we employed network-based integrative analyses of FTC and benign follicular thyroid adenoma (FTA) lesion transcriptomes to identify key genes and pathways that differ between them. We first analysed a microarray gene expression dataset (Gene Expression Omnibus GSE82208, n = 52) obtained from FTC and FTA tissues to identify differentially expressed genes (DEGs). Pathway analyses of these DEGs were then performed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) resources to identify potentially important pathways, and protein-protein interactions (PPIs) were examined to identify pathway hub genes. Our data analysis identified 598 DEGs, 133 genes with higher and 465 genes with lower expression in FTCs. We identified four significant pathways (one carbon pool by folate, p53 signalling, progesterone-mediated oocyte maturation signalling, and cell cycle pathways) connected to DEGs with high FTC expression; eight pathways were connected to DEGs with lower relative FTC expression. Ten GO groups were significantly connected with FTC-high expression DEGs and 80 with low-FTC expression DEGs. PPI analysis then identified 12 potential hub genes based on degree and betweenness centrality; namely, TOP2A, JUN, EGFR, CDK1, FOS, CDKN3, EZH2, TYMS, PBK, CDH1, UBE2C, and CCNB2. Moreover, transcription factors (TFs) were identified that may underlie gene expression differences observed between FTC and FTA, including FOXC1, GATA2, YY1, FOXL1, E2F1, NFIC, SRF, TFAP2A, HINFP, and CREB1. We also identified microRNA (miRNAs) that may also affect transcript levels of DEGs; these included hsa-mir-335-5p, -26b-5p, -124-3p, -16-5p, -192-5p, -1-3p, -17-5p, -92a-3p, -215-5p, and -20a-5p. Thus, our study identified DEGs, molecular pathways, TFs, and miRNAs that reflect molecular mechanisms that differ between FTC and benign FTA. Given the general similarities of these lesions and common tissue origin, some of these differences may reflect malignant progression potential, and include useful candidate biomarkers for FTC and identifying factors important for FTC pathogenesis.

Project description:Metastasis is the major cause of thyroid cancer-related death. However, little is known about the genes involved in the metastatic spread of thyroid carcinomas. We have created a mouse that spontaneously develops metastatic follicular thyroid carcinoma (FTC). This mouse harbors a targeted mutation (denoted TRβPV) in the thyroid hormone receptor β gene (Thrb(PV/PV) mice). Our recent studies show that the highly elevated level of thyroid stimulating hormone (TSH) in Thrb(PV/PV) mice promotes proliferation of thyroid tumor cells, but requires the collaboration of the oncogenic action of TRβPV to empower the tumor cells to undergo distant metastasis. To uncover genes destined to drive the metastatic process, we used cDNA microarrays to compare the genomic expression profile of laser capture microdissected thyroid tumor lesions of Thrb(PV/PV) mice with that of hyperplastic thyroid cells of wild-type mice having elevated TSH induced by treatment with the anti-thyroid drug propylthiouracil (WT-PTU mice). Analyses of microarray data indicated that the expressions of 150 genes were significantly altered between Thrb(PV/PV) and WT-PTU mice (87 genes had higher expression and 63 genes had lower expression in Thrb(PV/PV) mice than in WT-PTU mice). Thirty-six percent of genes with altered expression function as key regulators in metastasis. The remaining genes were involved in various cellular processes including metabolism, intracellular trafficking, transcriptional regulation, post-transcriptional modification, and cell-cell/extracellular matrix signaling. The present studies have uncovered novel genes responsible for the metastatic spread of FTC and, furthermore, have shown that the metastatic process of thyroid cancer requires effective collaboration among genes with diverse cellular functions. Importantly, the present studies indicate that the tumor cells in the primary lesions are endowed with the genes destined to promote metastasis. Thus, our study has provided new insights into the understanding of the metastatic spread of human thyroid cancer.

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Growth activation alone is not sufficient to cause metastatic thyroid cancer in a mouse model of follicular thyroid carcinoma.

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Growth activation alone is not sufficient to cause metastatic thyroid cancer in a mouse model of follicular thyroid carcinoma.

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