Activated platelets inhibit hepatocellular carcinoma cell differentiation and promote tumor progression via platelet-tumor cell binding

// Rongfeng Zhang 1, * , Huishu Guo 2, * , Jingchao Xu 3 , Bing Li 4 , Yue-Jian Liu 2 , Cheng Cheng 5 , Chunyan Zhou 6 , Yongfu Zhao 3 , Yang Liu 1 1 Institute of Heart and Vascular Diseases, First Affiliated Hospital of Dalian Medical University, Dalian, China 2 Department of Central Laboratory, First Affiliated Hospital of Dalian Medical University, Dalian, China 3 Department of General Surgery, Second Affiliated Hospital of Dalian Medical University, Dalian, China 4 Department of Clinical Laboratory, First Affiliated Hospital of Dalian Medical University, Dalian, China 5 Translational Research on Neurological Diseases Center, First Affiliated Hospital of Dalian Medical University, Dalian, China 6 Department of Clinical Pharmacy, First Affiliated Hospital of Dalian Medical University, Dalian, China * These authors have contributed equally to this work Correspondence to: Yang Liu, email: liuyang19831119@163.com Yongfu Zhao, email: dl.zyf67@163.com Keywords: platelet, clopidogrel, tumor differentiation, hepatocellular carcinoma, TCF4 Received: January 17, 2016      Accepted: July 26, 2016      Published: August 16, 2016 ABSTRACT Lack of differentiation in hepatocellular carcinoma (HCC) is associated with increased circulating platelet size. We measured platelet activation and plasma adenosine diphosphate (ADP) levels in HCC patients based on differentiation status. Local platelet accumulation and platelet-hepatoma cell binding were measured using immunohistochemistry (IHC) or flow cytometry. Using a xenograft assay in NON/SCID mice, we tested the effects of the anti-platelet drug clopidogrel on platelet activation, platelet infiltration, platelet-tumor cell binding and tumor cell differentiation. HCC patients with poor differentiation status displayed elevated platelet activation and higher ADP levels. Platelets accumulated within poorly differentiated tissues and localized at hepatoma cell membranes. Platelet-tumor cell binding was existed in carcinoma tissues, largely mediated by P-selectin on platelets. NOD/SCID mice with xenograft tumors also exhibited increased platelet activation and platelet-tumor cell binding. Clopidogrel therapy triggered hepatoma cell differentiation by attenuating platelet activation and platelet-tumor cell binding. TCF4 knockdown promoted HepG-2 cell differentiation and inhibited tumor formation, and TCF4 could be the potential downstream target for clopidogrel therapy.