ZHX2 enhances the cytotoxicity of chemotherapeutic drugs in liver tumor cells by repressing MDR1 via interfering with NF-YA

// Hongxin Ma 1,* , Xuetian Yue 1,* , Lifen Gao 1 , Xiaohong Liang 1 , Wenjiang Yan 1 , Zhenyu Zhang 1 , Haixia Shan 1 , Hualin Zhang 1 , Brett T. Spear 2 and Chunhong Ma 1 1 Key Laboratory for Experimental Teratology of Ministry of Education and Department of Immunology, Shandong University School of Medicine, Jinan, Shandong, P.R. China 2 Department of Microbiology, Immunology & Molecular Genetics and Markey Cancer Center, University of Kentucky College of Medicine, Lexington, KY, USA * These authors contributed equally to the work Correspondence: Chunhong Ma, email: // Keywords : ZHX2, transcriptional repression, chemoresistance, p-glycoprotein, apoptosis Received : September 23, 2014 Accepted : November 25, 2014 Published : November 26, 2014 Abstract We previously reported the tumor suppressor function of Zinc-fingers and homeoboxes 2 (ZHX2) in hepatocellular carcinoma (HCC). Other studies indicate the association of increased ZHX2 expression with improved response to high dose chemotherapy in multiple myeloma. Here, we aim to test whether increased ZHX2 levels in HCC cells repress multidrug resistance 1(MDR1) expression resulting in increased sensitivity to chemotherapeutic drugs. We showed evidence that increased ZHX2 levels correlated with reduced MDR1 expression and enhanced the cytotoxicity of CDDP and ADM in different HCC cell lines. Consistently, elevated ZHX2 significantly reduced ADM efflux in HepG2 cells and greatly increased the CDDP-mediated suppression of liver tumor growth in vivo . Furthermore, immunohistochemical staining demonstrated the inverse correlation of ZHX2 and MDR1 expression in HCC tissues. Luciferase report assay showed that ZHX2 repressed the MDR1 promoter activity, while knockdown of NF-YA or mutating the NF-Y binding site eliminated this ZHX2-mediated repression of MDR1 transcription. Co-IP and ChIP assay further suggested that ZHX2 interacted with NF-YA and reduced NF-Y binding to the MDR1 promoter. Taken together, we clarify that ZHX2 represses NF-Y-mediated activation of MDR1 transcription and, in doing so, enhances the effects of chemotherapeutics in HCC cells both in vitro and in vivo .