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SKP2 Activation by Thyroid Hormone Receptor ?2 Bypasses Rb-Dependent Proliferation in Rb-Deficient Cells.

ABSTRACT: Germline RB1 mutations strongly predispose humans to cone precursor-derived retinoblastomas and strongly predispose mice to pituitary tumors, yet shared cell type-specific circuitry that sensitizes these different cell types to the loss of RB1 has not been defined. Here we show that the cell type-restricted thyroid hormone receptor isoform TR?2 sensitizes to RB1 loss in both settings by antagonizing the widely expressed and tumor-suppressive TR?1. TR?2 promoted expression of the E3 ubiquitin ligase SKP2, a critical factor for RB1-mutant tumors, by enabling EMI1/FBXO5-dependent inhibition of SKP2 degradation. In RB1 wild-type neuroblastoma cells, endogenous Rb or ectopic TR?2 was required to sustain SKP2 expression as well as cell viability and proliferation. These results suggest that in certain contexts, Rb loss enables TR?1-dependent suppression of SKP2 as a safeguard against RB1-deficient tumorigenesis. TR?2 counteracts TR?1, thus disrupting this safeguard and promoting development of RB1-deficient malignancies. Cancer Res; 77(24); 6838-50. ©2017 AACR.

SUBMITTER: Xu XL

PROVIDER: S-EPMC5732859 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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SKP2 Activation by Thyroid Hormone Receptor β2 Bypasses Rb-Dependent Proliferation in Rb-Deficient Cells.

Xu Xiaoliang L XL Li Zhengke Z Liu Aihong A Fan Xianqun X Hu Dan-Ning DN Qi Dong-Lai DL Chitty David W DW Jia Renbing R Qui Jianping J Wang Justin Q JQ Sharaf Jake J Zou Jun J Weiss Rebecca R Huang Hongyan H Joseph Walter J WJ Ng Lily L Rosen Richard R Shen Binghui B Reid Mark W MW Forrest Douglas D Abramson David H DH Singer Samuel S Cobrinik David D Jhanwar Suresh C SC

Cancer research 20170928 24

Germline RB1 mutations strongly predispose humans to cone precursor-derived retinoblastomas and strongly predispose mice to pituitary tumors, yet shared cell type-specific circuitry that sensitizes these different cell types to the loss of RB1 has not been defined. Here we show that the cell type-restricted thyroid hormone receptor isoform TRβ2 sensitizes to RB1 loss in both settings by antagonizing the widely expressed and tumor-suppressive TRβ1. TRβ2 promoted expression of ...[more]

PMID: 28972075

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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.

Dataset Information

SKP2 Activation by Thyroid Hormone Receptor ?2 Bypasses Rb-Dependent Proliferation in Rb-Deficient Cells.

Publications

SKP2 Activation by Thyroid Hormone Receptor β2 Bypasses Rb-Dependent Proliferation in Rb-Deficient Cells.

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