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

Abstract

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. 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. 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. 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.