Knockdown of cyclooxygenase-2 leads to growth inhibition and cell cycle arrest in hepatocellular carcinoma cells

Background & aims: Cyclooxygenase-2 (COX-2) is proved to play important roles in the development and progression of various human tumors, including hepatocellular carcinoma (HCC). However, the antitumor effect of RNA interference (RNAi) technology targeting COX-2 in HCC has not yet been verified. Methods: We silenced COX-2 expression using a lentivirus-mediated RNAi and further investigated the effects of COX-2 knockdown on cell growth and cell cycle in Huh7 and SMMC-7721 cells. COX-2 mRNA was detected by RT-PCR while COX-2 protein was detected by Western blotting. The cell proliferation was measured by MTT assay. The cell cycle was measured by flow cytometry. The tumorigenicity of HCC cells was evaluated using soft-agar clonogenic assay in vitro and nude mouse xenograft model in vivo. Results: The down-regulation of COX-2 expression significantly inhibited cell proliferation and colony formation, and led to cell cycle arrest in vitro, and reduced the potential of tumorigenicity in vivo in both Huh7 and SMMC-7721 cells. Furthermore, PGE2 production was also decreased after COX-2 expression was suppressed. Finally, knockdown of COX-2 also induced the down-regulation of cell cycle-related protein, cyclinD1. Conclusions: The abrogation of COX-2 expression can lead to potent antitumor activity and knockdown of COX-2 may be served as a prospective therapeutic strategy against HCC.