Celecoxib enhances the antitumor activity of epirubicin in vitro. (A) Cell proliferation analysis in N1‐S1 cells after celecoxib (10 and 50 μmol/L), epirubicin (50 nmol/L), or combined treatment for 48 h. (B) The sub‐G1 fraction of N1‐S1 cells after celecoxib (10 μmol/L), epirubicin (50 nmol/L), or combined treatment for 72 h was determined by flow cytometry. The anchorage‐independent growth of (C) Huh‐7 and (D) Hep3B cells after celecoxib (10 and 50 μmol/L), epirubicin (50 nmol/L), or combined treatment for 10 days was determined by flat colony formation assay. (E) The cell invasiveness of Huh‐7 cells after celecoxib (10 and 50 μmol/L), epirubicin (50 nmol/L) or combined treatment for 24 h was determined by invasion assay. Data were mean ± SD (*P < 0.05, **P < 0.01).