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Regulation of pituitary tumor transforming gene (PTTG) expression and phosphorylation in thyroid cells.

Endocrinology | 2013

Human pituitary tumor transforming gene (hPTTG) is a multifunctional proto-oncogene implicated in the initiation and progression of several tumors. Phosphorylation of hPTTG is mediated by cyclin-dependent kinase 2 (CDC2), whereas cellular expression is regulated by specificity protein 1 (SP1). The mechanisms underlying hPTTG propagation of aberrant thyroid cell growth have not been fully defined. We set out to investigate the interplay between hPTTG and growth factors, as well as the effects of phosphorylation and SP1 regulation on hPTTG expression and function. In our study, epidermal growth factor (EGF), TGFα, and IGF-1 induced hPTTG expression and phosphorylation in thyroid cells, which was associated with activation of MAPK and phosphoinositide 3-kinase. Growth factors induced hPTTG independently of CDC2 and SP1 in thyroid carcinoma cells. Strikingly, CDC2 depletion in TPC-1 cells resulted in enhanced expression and phosphorylation of hPTTG and reduced cellular proliferation. In reciprocal experiments, hPTTG overexpression induced EGF, IGF-1, and TGFα mRNAs in primary human thyrocytes. Treatment of primary human thyrocytes with conditioned media derived from hPTTG-transfected cells resulted in autocrine upregulation of hPTTG protein, which was ameliorated by growth factor depletion or growth factor receptor tyrosine kinase inhibitors. A transgenic murine model of thyroid targeted hPTTG overexpression (hPTTG-Tg) (FVB/N strain, both sexes) demonstrated smaller thyroids with reduced cellular proliferation and enhanced secretion of Egf. In contrast, Pttg(-/-) knockout mice (c57BL6 strain, both sexes) showed reduced thyroidal Egf mRNA expression. These results define hPTTG as having a central role in thyroid autocrine signaling mechanisms via growth factors, with profound implications for promotion of transformed cell growth.

Pubmed ID: 23867215 RIS Download

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SP1 Antibody (antibody)

RRID:AB_10621245

This polyclonal targets SP1

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cdc2 Antibody (antibody)

RRID:AB_2074654

This unknown targets cdc2

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PCNA (FL-261) (antibody)

RRID:AB_2160375

This polyclonal targets PCNA

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IGF-I Polyclonal Antibody (antibody)

RRID:AB_2280020

This polyclonal targets IGF1

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Phospho-p44/42 MAPK (Erk1/2) (Thr202/Tyr204) (D13.14.4E) XP® Rabbit mAb (antibody)

RRID:AB_2315112

This monoclonal targets Phospho-p44/42 MAPK (Erk1/2) (Thr202/Tyr204)

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Securin Polyclonal Antibody (antibody)

RRID:AB_2533156

This unknown targets Securin

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Phospho-Akt (Ser473) (193H12) Rabbit mAb (antibody)

RRID:AB_331168

This monoclonal targets Phospho-Akt (Ser473) (193H12) Rabbit mAb

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