Down-regulation of ARNT promotes cancer metastasis by activating the fibronectin/integrin β1/FAK axis

// Chi-Ruei Huang 1, 2 , Chung-Ta Lee 3 , Kwang-Yu Chang 4, 5 , Wen-Chang Chang 2 , Yao-Wen Liu 6 , Jenq-Chang Lee 7 , Ben-Kuen Chen 1, 8, 9 1 Institute of Bioinformatics and Biosignal Transduction, College of Bioscience and Biotechnology, National Cheng Kung University, Taiwan, ROC 2 Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taiwan, ROC 3 Department of Pathology, National Cheng Kung University Hospital, Taiwan, ROC 4 National Institute of Cancer Research, National Health Research Institutes, Taiwan, ROC 5 Division of Hematology/Oncology, Department of Internal Medicine; National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Taiwan, ROC 6 Department of Pathology, Kuo General Hospital, Taiwan, ROC 7 Department of Surgery, National Cheng Kung University Hospital, Taiwan, ROC 8 Department of Pharmacology, College of Medicine, National Cheng Kung University, Taiwan, ROC 9 Institute for Cancer Biology and Drug Discovery, College of Medical Science and Technology, Taipei Medical University, Taiwan, ROC Correspondence to: Ben-Kuen Chen e-mail: bkchen58@mail.ncku.edu.tw Keywords: metastasis, ARNT, oncogene, ROS Received: October 15, 2014 Accepted: February 25, 2015 Published: March 20, 2015 ABSTRACT The aryl hydrocarbon receptor nuclear translocator (ARNT) is broadly involved in regulating tumorigenesis by inducing genes that are involved in tumor growth and angiogenesis. Tumorigenesis usually involves normoxic conditions. However, the role of ARNT in tumor metastasis during normoxia remains unclear. Here, we demonstrate that ARNT protein levels were decreased in late-stage human colorectal cancer using immunohistochemical analysis. Down-regulation of ARNT protein promoted cancer cell migration and invasion, which was mediated by activation of the fibronectin/integrin β1/FAK signaling axis. In addition, the enhancement of migration and invasion in ANRT knockdown cells was blocked when ARNT was restored in the cells. In xenografts in severe combined immunodeficiency mice, tumor growth was significantly inhibited in the ARNT-knockdown condition. However, the tail-vein injection animal model revealed that the depletion of ARNT-induced metastatic lung colonies was further enhanced when ARNT expression was recovered post-injection. Interestingly, chemotherapeutic drugs inhibited ARNT expression and promoted the invasion of residual tumor cells. These results suggest that ARNT may play a positive role during tumor growth (either in early-stage tumor growth or in organ metastases), but plays a negative role in tumor migration and invasion. Therefore, the efficiency of ARNT-targeted therapy during different cancer stages should be carefully evaluated.