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

// Yang Chen 1, * , Weishuai Liu 2, * , Peng Wang 3 , Hailing Hou 1 , Ningbo Liu 1 , Linlin Gong 1 , Youyou Wang 1 , Kai Ji 2 , Lujun Zhao 1 , Ping Wang 1 1 Department of Radiation Oncology, Center of Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060, China 2 Department of Pain Management, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research, Center of Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060, China 3 Department of Radiation Oncology, Peking University International Hospital, Beijing 102206, China * These authors have contributed equally to this work Correspondence to: Lujun Zhao, email: zhaolujun@tjmuch.com Keywords: epithelial-mesenchymal transition (EMT), halofuginone, transforming growth factor-β (TGF-β1), radiotherapy, lung cancer Received: April 09, 2016      Accepted: July 27, 2016      Published: August 11, 2016 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.