Luteolin synergizes the antitumor effects of 5-fluorouracil against human hepatocellular carcinoma cells through apoptosis induction and metabolism

Aims: Some compounds derived from Chinese medicine have demonstrated great prospective roles in sensitization to chemotherapy. This study aimed to investigate the combination of luteolin and 5-fluorouracil on proliferations of hepatocellular carcinoma cells and the potential mechanisms. Main methods: The antitumor effects of luteolin, 5-fluorouracil, and their combinations were detected by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium/phenazine methosulfate assay, and isobole method was used to evaluate drug combinations. CellTiter-Blue and Caspase-Glo 3/7 assay were used for assessment of cell viability and apoptosis after treatment with luteolin, 5-fluorouracil and their combinations. Cell cycle distributions and apoptosis were detected by PI staining, Hoechst 33342 staining and FITC-Annexin V/PI staining. Bcl-2, bax, p53 and PARP expressions were determined by Western blot. Furthermore, mRNA levels of 5-fluorouracil metabolism related enzymes were detected by RT-PCR. Key findings: Drug combination study showed that luteolin could synergize the antitumor effects of 5-fluorouracil at different dose ratios (luteolin: 5-fluorouracil = 10: 1, 20: 1, 40: 1) against HepG2 and Bel7402 cells. Cell viability and cell apoptosis analysis showed that the synergistic growth inhibition caused by combined luteolin and 5-fluorouracil was closely related to apoptosis. Further mechanism studies showed that the synergistic effects of drug combinations were related with enhanced bax/bcl-2 ratios and p53 expressions, and induced PARP cleavage. Also, combined luteolin and 5-fluorouracil could significantly decrease the dihydropyrimidine dehydrogenase. Significance: These results showed that luteolin could synergize the antitumor effects of 5-fluorouracil on HepG2 and Bel7402 cells, which might be related with apoptosis and regulation of 5-fluorouracil metabolism. (C) 2015 Elsevier Inc. All rights reserved.