PTGS2 and cancer: Accumulating studies have found cyclooxygenase-2 (COX-2), an enzyme that catalyzes prostaglandin synthesis, is highly expressed in multiple cancers, and is involved in tumorigenicity and chemotherapy resistance, which may be related to 5-fluorouracil resistance in HCC (Zhang S. et al., 2019; Hashemi Goradel et al., 2019; Xu et al., 2020).