title: Characterization and resistance mechanisms of a 5-fluorouracil- resistant hepatocellular carcinoma cell line.
abstract: OBJECTIVE
  The chemoresistance of human hepatocellular carcinoma (HCC) to cytotoxic drugs, especially intrinsic or acquired multidrug resistance (MDR), still remains a major challenge in the management of HCC. In the present study, possible mechanisms involved in MDR of HCC were identified using a 5-fluorouracil (5-FU) -resistant human HCC cell line.
  
  
  METHODS
  BEL-7402/5-FU cells were established through continuous culturing parental BEL-7402 cells, imitating the pattern of chemotherapy clinically. Growth curves and chemosensitivity to cytotoxic drugs were determined by MTT assay. Doubling times, colony formation and adherence rates were calculated after cell counting. Morphological alteration, karyotype morphology, and untrastructure were assessed under optical and electron microscopes. The distribution in the cell cycle and drug efflux pump activity were measured by flow cytometry. Furthermore, expression of potential genes involved in MDR of BEL-7402/5-FU cells were detected by immunocytochemistry.
  
  
  RESULTS
  Compared to its parental cells, BEL-7402/5-FU cells had a prolonged doubling time, a lower mitotic index, colony efficiency and adhesive ability, and a decreased drug efflux pump activity. The resistant cells tended to grow in clusters and apparent changes of ultrastructures occurred. BEL-7402/5-FU cells presented with an increased proportion in S and G2/M phases with a concomitant decrease in G0/G1 phase. The MDR phenotype of BEL-7402/5-FU might be partly attributed to increased drug efflux pump activity via multidrug resistance protein 1 (MRP1), overexpression of thymidylate synthase (TS), resistance to apoptosis by augmentation of the Bcl-xl/Bax ratio, and intracellular adhesion medicated by E-cadherin (E-cad). P-glycoprotein (P-gp) might play a limited role in the MDR of BEL-7402/5-FU.
  
  
  CONCLUSIONS
  Increased activity or expression of MRP1, Bcl-xl, TS, and E-cad appear to be involved in the MDR mechanism of BEL-7402/5-FU.
authors.affiliation: Department of Traditional Chinese Medicine, Changhai Hospital, Second Military Medical University, Shanghai, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Gu
authors.forename: Fan-Fu
authors.initials: FF
authors.lastname: Fang
authors.forename: Bai
authors.initials: B
authors.lastname: Li
authors.forename: Bin-Bin
authors.initials: BB
authors.lastname: Cheng
authors.forename: Chang-Quan
authors.initials: CQ
authors.lastname: Ling
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002448:Cell Adhesion; D059447:Cell Cycle Checkpoints; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival; D004317:Doxorubicin / Q000493:pharmacokinetics; D018432:Drug Resistance, Multiple / Q000235:genetics; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D005472:Fluorouracil / Q000493:pharmacokinetics / Q000494:pharmacology*; D006801:Humans; D059785:Karyotype; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008940:Mitotic Index; D010641:Phenotype; D013940:Thymidylate Synthase / Q000235:genetics / Q000378:metabolism; D014410:Tumor Stem Cell Assay; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism; D051020:bcl-X Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000964:Antimetabolites, Antineoplastic; C494826:BAX protein, human; C494811:BCL2L1 protein, human; D015820:Cadherins; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D004317:Doxorubicin; D013940:Thymidylate Synthase; D005472:Fluorouracil