PTGS2 and hepatocellular carcinoma: To date, the sorafenib combined therapies include anticancer drugs like arsenic trioxide [35], the member of the statins group, fluvastatin [36], the cyclooxygenase-2 inhibitor, celecoxib [37], or natural compounds such as silibinin [38] and curcumin [39], that have been reported to enhance in vitro cytotoxicity in HCC.