Amphiregulin activates regulatory T lymphocytes and suppresses CD8 + T cell-mediated anti-tumor response in hepatocellular carcinoma cells

// Chun-Hui Yuan 1 , Xiao-Ming Sun 2 , Cheng-Liang Zhu 3 , Shao-Ping Liu 4 , Long Wu 5 , Hao Chen 1 , Mao-Hui Feng 6 , Ke Wu 7 , Fu-Bing Wang 1 1 Department of Laboratory Medicine, Zhongnan Hospital of Wuhan University, Wuchang District, Wuhan 430071, P.R. China 2 Department of Immunology, School of Basic Medical Sciences, Wuhan University, Wuchang District, Wuhan 430071, P.R. China 3 The State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuchang District, Wuhan 430072, P.R. China 4 Hubei Key Laboratory of Tumor Biological Behaviors & Hubei Cancer Clinical Study Center, Zhongnan Hospital of Wuhan University, Wuchang District, Wuhan 430071, P.R. China 5 Department of Oncology, Renmin Hospital of Wuhan University, Wuchang District, Wuhan 430060, P.R. China 6 Department of Oncology, Zhongnan Hospital of Wuhan University, Wuchang District, Wuhan 430071, P.R. China 7 Animal Experiment Center of Wuhan University/Animal Biosafety Level-III laboratory, Wuchang District, Wuhan 430071, P.R. China Correspondence to: Fu-Bing Wang, e-mail: wfb20042002@sina.com Keywords: hepatocellular carcinoma, amphiregulin, CD4 + regulatory T cells, CD8 + T cells Received: June 09, 2015      Accepted: September 24, 2015      Published: October 06, 2015 ABSTRACT CD8 + T cell-mediated immune response plays an important role in inhibiting progression of hepatocellular carcinoma (HCC). For strategic immunotherapy, it is critical to understand why some of the tumor cells escape from this immune attack. In this study, we investigated how HCC cells alter endogenous anti-tumor immunity and their related signaling pathways. We found that HCC cells, both in vitro and in vivo , substantially secret and express amphiregulin (AR). AR in turn activates immunosuppressive function of intratumoral CD4 + Foxp3 + regulatory T cells (Tregs), a major inhibitor of CD8 + T cells. Using either lentiviral siRNA, or AR neutralizing antibody, we blocked the expression and function of AR to test the specificity of AR mediated activation of Tregs, Biochemical and cell biology studies were followed and confirmed that blocking of AR inhibited Tregs activation. In addition, we found that AR can trigger the activation of rapamycin complex 1(mTORC1) signaling in Tregs. The mTORC1 inhibitor rapamycin treatment led to compromise Treg function and resulted in enhancing anti-tumor function of CD8 + T cells. Blocking AR/EGFR signaling in Tregs with Gefitinib also enhanced anti-tumor immunity and decreased tumor size in a mouse xenograft tumor model. Taken together, our study suggested a novel mechanism of functional interaction between HCC and Tregs for regulating anti-tumor function of CD8 + T cells.