Research Article Celecoxib Inhibits Interleukin-6/Interleukin-6 Receptor–Induced JAK2/STAT3 Phosphorylation in Human Hepatocellular Carcinoma Cells Yan Liu 1 , Aiguo Liu 1,4 , Huameng Li 2,3 , Chenglong Li 2 , and Jiayuh Lin 1 Abstract Growing evidence shows an association between chronic liver inflammation and hepatocellular carcinoma (HCC) development. STAT3, which is associated with inflammation and cellular transfor- mation, is constitutively activated in human HCC tissues but not in normal human liver tissues. Although interleukin-6 (IL-6) is elevated in the serum of patients with HCC, it is not fully understood whether STAT3 constitutive activation is positively correlated with autocrine IL-6 secreted by HCC cells. Here, we reported that in HCC cells, the elevated levels of both IL-6 and IL-6 receptor (IL-6R, gp80), not IL-6 alone, correlated with STAT3 activation. We also explored whether the anticancer effects of celecoxib, an anti-inflammatory drug, may be due to the inhibition of the IL-6/STAT3 pathway in HCC cells. Our results showed that celecoxib decreased STAT3 phosphorylation by reducing Janus- activated kinase (JAK2) phosphorylation and caused apoptosis in HCC cells. Celecoxib could also block exogenous IL-6–induced STAT3 phosphorylation and nuclear translocation. Moreover, we observed more significant inhibition of cell viability when celecoxib was combined with doxorubicin or sorafenib. We conclude that the elevated levels of IL-6/IL-6R may be correlated with STAT3 activation in HCC cells. Celecoxib may be a candidate for HCC therapy through blocking IL-6/STAT3 pathway and can be combined with other anticancer drugs to reduce drug resistance caused by IL-6/STAT3 signals. Cancer Prev Res; 4(8); 1296–305. Ó2011 AACR. Introduction Primary liver cancer is the sixth most common cancer of all human cancers worldwide and is a major health pro- blem due to the poor prognosis (1). Hepatocellular carci- noma (HCC) accounts for more than 85% of all primary liver cancers, with a 5-year survival rate of 9% and a median survival time of less than 1 year (2–4). Epidemiologic studies have established that HCC occurs in association with hepatitis B virus infection and ethanol intake, but the molecular mechanisms have not been fully known. Over the past few years, growing evidence has shown that cyto- kines, such as interleukin-6 (IL-6), and transcription factors, such as NF-kB and STAT3, play an important role in HCC development (2, 5–9). Patients with HCC show elevated levels of IL-6 in their serum as compared with those with liver cirrhosis or with healthy individuals. In addition, the level of IL-6 is remarkably high in HCC stage III patients (5). STAT3, a major transducer to mediate the signal from IL-6 to the nucleus, is found significantly correlated with the prog- nosis of HCC patients (9), indicating that IL-6/STAT3 signaling pathway might be a therapeutic target. Constitutively activated STAT3 may induce tumor for- mation in nude mice and is frequently detected in various human cancers (10–12). STAT3 may be involved in onco- genesis, cell proliferation, angiogenesis, immune evasion, and apoptotic resistance (13–15). Growing evidence has shown that a blockade of constitutively activated STAT3 can cause apoptosis in vitro, inhibit tumor growth in vivo, and enhance the sensitivity to chemotherapy and radio- therapy (11, 16–21). IL-6 induces STAT3 phosphorylation at tyrosine residue 705 through IL-6 receptors (IL-6R and gp130) and Janus family kinases [Janus-activated kinase (JAK); refs. 22, 23]. Phosphorylated STAT3 molecules dimerize and translocate from the cytoplasm to the nucleus, where they bind to specific DNA elements to regulate the downstream genes, Authors' Affiliations: 1 Center for Childhood Cancer, The Research Insti- tute at Nationwide Children's Hospital, Department of Pediatrics, 2 Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, and 3 Biophysics Graduate Program, The Ohio State University, Columbus, Ohio; and 4 Department of Pediatrics, Tongji Hospital, Huazhong University of Science and Technology, Wuhan, Hubei, PR China Note: Supplementary data for this article are available at Cancer Preven- tion Research Online (http://cancerprevres.aacrjournals.org/). Current address for Y. Liu: Department of Cancer Biology, Vanderbilt University School of Medicine, Nashville, TN. Y. Liu and A. Liu contributed equally to the work. Corresponding Author: Jiayuh Lin, Center for Childhood Cancer, Depart- ment of Pediatrics, College of Medicine, The Ohio State University, 700 Children's Drive, Columbus, OH 43205. Phone: 614-722-5086; Fax: 614- 722-5895; E-mail: lin.674@osu.edu doi: 10.1158/1940-6207.CAPR-10-0317 Ó2011 American Association for Cancer Research. Cancer Prevention Research Cancer Prev Res; 4(8) August 2011 1296 Research. on June 13, 2020. © 2011 American Association for Cancer cancerpreventionresearch.aacrjournals.org Downloaded from Published OnlineFirst April 13, 2011; DOI: 10.1158/1940-6207.CAPR-10-0317