The sonic hedgehog signaling pathway stimulates anaplastic thyroid cancer cell motility and invasiveness by activating Akt and c-Met.

Ashley J Williamson,Xiulong Xu,Yi Li,Richard A Prinz,Michelle E Doscas,Jin Ye,Katherine B Heiden,Mingzhao Xing

doi:10.18632/oncotarget.7228

Abstract

The sonic hedgehog (Shh) pathway is highly activated in thyroid neoplasms and promotes thyroid cancer stem-like cell phenotype, but whether the Shh pathway regulates thyroid tumor cell motility and invasiveness remains unknown. Here, we report that the motility and invasiveness of two anaplastic thyroid tumor cell lines, KAT-18 and SW1736, were inhibited by two inhibitors of the Shh pathway (cyclopamine and GANT61). Consistently, the cell motility and invasiveness was decreased by Shh and Gli1 knockdown, and was increased by Gli1 overexpression in KAT-18 cells. Mechanistic studies revealed that Akt and c-Met phosphorylation was decreased by a Gli1 inhibitor and by Shh and Gli1 knockdown, but was increased by Gli1 overexpression. LY294002, a PI-3 kinase inhibitor, and a c-Met inhibitor inhibited the motility and invasiveness of Gli1-transfected KAT-18 cells more effectively than the vector-transfected cells. Knockdown of Snail, a transcription factor regulated by the Shh pathway, led to decreased cell motility and invasiveness in KAT-18 and SW1736 cells. However, key epithelial-to-mesenchymal transition (EMT) markers including E-cadherin and vimentin as well as Slug were not affected by cyclopamine and GANT61 in either SW1736 or WRO82, a well differentiated follicular thyroid carcinoma cell line. Our data suggest that the Shh pathway-stimulated thyroid tumor cell motility and invasiveness is largely mediated by AKT and c-Met activation with little involvement of EMT.

Highlights

In mammals, the hedgehog pathway is regulated by three ligands: Sonic hedgehog (Shh), Indian hedgehog, and Desert hedgehog
Our present study showed that inhibition of the Shh pathway by Smo and Gli1 inhibitors or by Shh and Gli1 knockdown led to decreased cell motility and chemoinvasion in KAT-18 and SW1736 cells, whereas Gli1 overexpression enhanced KAT-18 motility and invasive potential
AKT and c-Met phosphorylation was increased in Gli1-transfected KAT-18 cells but decreased in KAT-18 cells with Shh and Gli1 knockdown. c-Met inhibitor III and the AKT inhibitor LY294002 decreased cell motility and invasiveness of Gli1-transfected cells

Summary

Introduction

The hedgehog pathway is regulated by three ligands: Sonic hedgehog (Shh), Indian hedgehog, and Desert hedgehog. Hedgehog binding to Patched leads to the uncoupling of Patched from Smo, subsequently leading to the activation of a signal cascade and the translocation of Gli into the nucleus to induce or repress gene expression [1,2,3]. The sonic hedgehog signaling pathway has been implicated in stimulating tumor cell motility and invasion www.impactjournals.com/oncotarget in several types of malignancies [3]. Gli can directly bind the E-cadherin promoter and induce its expression [5, 6]. The Shh pathway may promote tumor cell invasiveness by cross-activating the PI-3 kinase pathway or induces metalloproteinase expression [7,8,9,10,11,12,13,14,15]. Understanding the crosstalk between the Shh and other pathways will facilitate the discovery of novel therapeutics and the treatment of metastatic disease

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Results

Conclusion