title: Luteolin synergizes the antitumor effects of 5-fluorouracil against human hepatocellular carcinoma cells through apoptosis induction and metabolism.
abstract: OBJECTIVE
  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.
  
  
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, PR China; National Center for Pharmaceutical Screening, Institute of Materia Medica, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100050, PR China.
authors.forename: Huanli
authors.initials: H
authors.lastname: Xu
authors.affiliation: National Center for Pharmaceutical Screening, Institute of Materia Medica, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100050, PR China.
authors.forename: Tao
authors.initials: T
authors.lastname: Yang
authors.affiliation: Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, PR China.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Liu
authors.affiliation: Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, PR China.
authors.forename: Ye
authors.initials: Y
authors.lastname: Tian
authors.affiliation: Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, PR China.
authors.forename: Xiaoliang
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, PR China.
authors.forename: Ru
authors.initials: R
authors.lastname: Yuan
authors.affiliation: Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, PR China.
authors.forename: Shuonan
authors.initials: S
authors.lastname: Su
authors.affiliation: Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, PR China.
authors.forename: Xiukun
authors.initials: X
authors.lastname: Lin
authors.affiliation: National Center for Pharmaceutical Screening, Institute of Materia Medica, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100050, PR China. Electronic address: xhl_52china@163.com.
authors.forename: Guanhua
authors.initials: G
authors.lastname: Du
mesh_terms: D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000096:biosynthesis / Q000235:genetics; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D042943:Dihydrouracil Dehydrogenase (NADP) / Q000037:antagonists & inhibitors; D004357:Drug Synergism; D005472:Fluorouracil / Q000494:pharmacology*; D006801:Humans; D008114:Liver Neoplasms, Experimental / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D047311:Luteolin / Q000494:pharmacology*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D011446:Prospective Studies; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics
chemical_list: D000964:Antimetabolites, Antineoplastic; D051017:Apoptosis Regulatory Proteins; D012333:RNA, Messenger; D042943:Dihydrouracil Dehydrogenase (NADP); D047311:Luteolin; D005472:Fluorouracil
keywords: 5-Fluorouracil; Apoptosis; Hepatocellular carcinoma; Luteolin; Synergistic effect