MEL treatment-induced ER stress, and eventually apoptosis in human SMMC-7721 cells. Knockdown of GRP78 using siRNA or proteosome inhibitor enhanced the cytotoxicity of the combination of SOR with MEL-treatment in SMMC-

Sorafenib (SOR) is a promising treatment for advanced hepatocellular carcinoma (HCC). However, the precise mechanisms of toxicity and drug resistance have not been fully explored and new strategies are urgently needed for HCC therapy. Meloxicam (MEL) is a selective cyclooxygenase-2 (COX-2) inhibitor which elicits antitumor effects in human HCC cells. In the present study, we investigated the interaction between MEL and SOR in human SMMC-7721 cells and the role endoplasmic reticulum (ER) stress exerts in the combination of SOR with MEL treatment-induced cytotoxicity. Our results revealed that the combination treatment synergistically inhibited cell proliferation and enhanced apoptosis. Furthermore, the combination treatment enhanced ER stress-related molecules which involved in SMMC-7721 cell apoptosis. GRP78 knockdown by siRNA or co-treatment with MG132 significantly increased this combination treatment-induced apoptosis. In addition, we found that the combination treatment suppressed tumor growth by way of activation of ER stress in in vivo models. We concluded that the combination of SOR with MEL treatment-induced ER stress, and eventually apoptosis in human SMMC-7721 cells. Knockdown of GRP78 using siRNA or proteosome inhibitor enhanced the cytotoxicity of the combination of SOR with MEL-treatment in SMMC7721 cells. These findings provided a new potential treatment strategy against HCC. Introduction Hepatocellular carcinoma (HCC) is one of the most common malignant tumors and the fourth primary cause of tumor-related deaths worldwide with high mortality and poor prognosis (1). Although many types of therapeutic measures including surgical resection, transarterial chemoembolization (TACE), radiation and chemotherapy have been used for the treatment of HCC, most patients progress to an advanced stage after the initial therapeutic benefit attributed to high chemoresistance, particularly due to the multidrug resistance (MDR) of HCC (2). Sorafenib (SOR), an oral multikinase inhibitor, which inhibits tumor growth and angiogenesis by way of inhibiting vascular endothelial growth factor receptor 2 and other receptor tyrosine kinases has been used as the standard treatment for advanced stages of HCC based on two large randomized phase III trials, which led to the Food and Drug Administration (FDA) approval since it prolongs survival for 2-3 months in advanced and inoperable HCC cases (3-5). However, clinical results have been disappointing showing that a large number of advanced HCC patients are unresponsive or acquire resistance to SOR. Therefore, it is urgent to seek new effective therapy strategies to combat HCC. Non-steroidal anti-inflammatory drugs (NSAIDs) have been reported to reduce the risk of developing cancer (6-8). Meloxicam (MEL), a selective cyclooxygenase-2 (COX-2) inhibitor, has been demonstrated to inhibit proliferation and promote apoptosis in many malignant diseases (9-11). Our previous experimental results showed that COX-2 inhibitor exhibits antiproliferative and proapoptotic effects in HCC cell lines (12,13). However, the detailed effects and mechanisms of MEL combined with SOR for treating HCC cells have not been fully cleared. Recently, a number of studies have revealed that certain chemotherapeutics lead to cell death by the way of the ER stress-related apoptosis (14,15). Therefore, we hypothesized that ER stress promoting proapoptotic effects or inhibiting its proliferative function may be a potential target for the treatment of HCC. The endoplasmic reticulum (ER), a central cellular organelle, plays a crucial role in protein folding and maturation as well as accumulation of intracellular calcium. Small Meloxicam combined with sorafenib synergistically inhibits tumor growth of human hepatocellular carcinoma cells via ER stress-related apoptosis JINGTAO ZHONG1, PENG XIu1, XIAOFENG DONG2, FuHAI WANG1, HONGLONG WEI1, XIN WANG1, ZONGZHEN Xu1, FENG LIu1, TAO LI1, YONG WANG1 and JIE LI1 1Department of General Surgery, Qianfoshan Hospital, Shandong university, Jinan, Shandong; 2Department of General Surgery, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, Guangxi, P.R. China Received June 16, 2015; Accepted July 10, 2015 DOI: 10.3892/or.2015.4181 Correspondence to: Dr Jie Li, Department of General Surgery, Qianfoshan Hospital, Shandong university, 16766 Jingshi Road, Jinan, Shandong, P.R. China E-mail: [email protected]