Halofuginone inhibits radiotherapy-induced epithelial-mesenchymal transition in lung cancer.

Yang Chen,Hailing Hou,Peng Wang,Ningbo Liu,Ping Wang,Weishuai Liu,Kai Ji,Youyou Wang,Linlin Gong,Lujun Zhao

doi:10.18632/oncotarget.11217

Abstract

Radiotherapy is used to treat many different human tumors. Paradoxically, radiation can activate TGF-β1 signaling and induce the epithelial-mesenchymal transition (EMT), which is associated with enhanced tumor progression. This study investigated the inhibitory effects of halofuginone, a plant-derived alkaloid that has been shown to inhibit TGF-β1 signaling, on radiation-induced EMT and explored the underlying mechanisms using a Lewis lung carcinoma (LLC) xenograft model. The cells and animals were divided into five treatment groups: Normal Control (NC), Halofuginone alone (HF), Radiotherapy alone (RT), Radiotherapy combined with Halofuginone (RT+HF), and Radiotherapy combined with the TGF-β1 inhibitor SB431542 (RT+SB). Radiation induced EMT in lung cancer cells and xenografts, as evidenced by increased expression of the mesenchymal markers N-cadherin and Vimentin, and reduced expression of the epithelial markers E-cadherin and Cytokeratin. Further, radiotherapy treatment increased the migration and invasion of LLC cells. Halofuginone reversed the EMT induced by radiotherapy in vitro and in vivo, and inhibited the migration and invasion of LLC cells. In addition, TGF-β1/Smad signaling was activated by radiotherapy and the mRNA expression of Twist and Snail was elevated; this effect was reversed by halofuginone or the TGF-β1 inhibitor SB431542. Our results demonstrate that halofuginone inhibits radiation-induced EMT, and suggest that suppression of TGF-β1 signaling may be responsible for this effect.

Highlights

Epithelial-mesenchymal transition (EMT) is an essential process during embryonic development that has a profound impact on cancer progression
The cells and animals were divided into five treatment groups: Normal Control (NC), Halofuginone alone (HF), Radiotherapy alone (RT), Radiotherapy combined with Halofuginone (RT+HF), and Radiotherapy combined with the TGF-β1 inhibitor SB431542 (RT+SB)
Western Blots showed that TGF-β1/Smad signaling both in Lewis lung carcinoma (LLC) cells (Figure 4D) and xenografts (Figure 6C) was activated by radiotherapy, and this effect was reversed by halofuginone or the TGF-β1 inhibitor SB431542. p-Smad2 was increased in the RT group and reduced in the two combination groups

Summary

INTRODUCTION

Epithelial-mesenchymal transition (EMT) is an essential process during embryonic development that has a profound impact on cancer progression. Recent studies indicate that halofuginone, a plant-derived alkaloid, can inhibit TGF-β1 signaling pathway by multiple mechanisms [6]. Halofuginone blocks TGF-β1 signaling in epithelial cells by inhibiting the phosphorylation and activation of Smad and Smad, and by inducing Smad expression [7]. Halofuginone therapy has been shown to reduce the development and progression of bone metastasis caused by melanoma cells by inhibiting TGF-β1 signaling [8]. Our previous studies have demonstrated that the combination of halofuginone and radiotherapy inhibits www.impactjournals.com/oncotarget hepatic and pulmonary metastases [9], but the underlying mechanisms have not been established. We report for the first time that halofuginone can block TGF-β1 signaling to suppress radiation induced EMT. Our findings suggest that radiotherapy combined with halofuginone may be a novel treatment for lung cancer

RESULTS

DISCUSSION

Findings

MATERIALS AND METHODS