title: Differential effects of arsenic trioxide on chemosensitization in human hepatic tumor and stellate cell lines.
abstract: BACKGROUND
  Crosstalk between malignant hepatocytes and the surrounding peritumoral stroma is a key modulator of hepatocarcinogenesis and therapeutic resistance. To examine the chemotherapy resistance of these two cellular compartments in vitro, we evaluated a well-established hepatic tumor cell line, HepG2, and an adult hepatic stellate cell line, LX2. The aim was to compare the chemosensitization potential of arsenic trioxide (ATO) in combination with sorafenib or fluorouracil (5-FU), in both hepatic tumor cells and stromal cells.
  
  
  METHODS
  Cytotoxicity of ATO, 5-FU, and sorafenib, alone and in combination against HepG2 cells and LX2 cells was measured by an automated high throughput cell-based proliferation assay. Changes in survival and apoptotic signaling pathways were analyzed by flow cytometry and western blot. Gene expression of the 5-FU metabolic enzyme, thymidylate synthase, was analyzed by real time PCR.
  
  
  RESULTS
  Both HepG2 and LX2 cell lines were susceptible to single agent sorafenib and ATO at 24 hr (ATO IC(50): 5.3 μM in LX2; 32.7 μM in HepG2; Sorafenib IC(50): 11.8 μM in LX2; 9.9 μM in HepG2). In contrast, 5-FU cytotoxicity required higher concentrations and prolonged (48-72 hr) drug exposure. Concurrent ATO and 5-FU treatment of HepG2 cells was synergistic, leading to increased cytotoxicity due in part to modulation of thymidylate synthase levels by ATO. Concurrent ATO and sorafenib treatment showed a trend towards increased HepG2 cytotoxicity, possibly due to a significant decrease in MAPK activation in comparison to treatment with ATO alone.
  
  
  CONCLUSIONS
  ATO differentially sensitizes hepatic tumor cells and adult hepatic stellate cells to 5-FU and sorafenib. Given the importance of both of these cell types in hepatocarcinogenesis, these data have implications for the rational development of anti-cancer therapy combinations for the treatment of hepatocellular carcinoma (HCC).
authors.affiliation: Department of Surgery, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Fatima
authors.initials: F
authors.lastname: Rangwala
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Williams
authors.forename: Ginger R
authors.initials: GR
authors.lastname: Smith
authors.forename: Zainab
authors.initials: Z
authors.lastname: Thomas
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Allensworth
authors.forename: H Kim
authors.initials: HK
authors.lastname: Lyerly
authors.forename: Anna Mae
authors.initials: AM
authors.lastname: Diehl
authors.forename: Michael A
authors.initials: MA
authors.lastname: Morse
authors.forename: Gayathri R
authors.initials: GR
authors.lastname: Devi
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000328:Adult; D000970:Antineoplastic Agents / Q000494:pharmacology; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000494:pharmacology*; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D005472:Fluorouracil / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006131:Growth Inhibitors / Q000494:pharmacology; D056945:Hep G2 Cells; D055166:Hepatic Stellate Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D020128:Inhibitory Concentration 50; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009536:Niacinamide / Q000031:analogs & derivatives / Q000494:pharmacology; D010087:Oxides / Q000494:pharmacology*; D010671:Phenylurea Compounds / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000077157:Sorafenib; D013940:Thymidylate Synthase / Q000235:genetics; D013997:Time Factors
chemical_list: D000970:Antineoplastic Agents; D001152:Arsenicals; D006131:Growth Inhibitors; D010087:Oxides; D010671:Phenylurea Compounds; D009536:Niacinamide; D000077157:Sorafenib; D013940:Thymidylate Synthase; D055372:AMP-Activated Protein Kinases; D000077237:Arsenic Trioxide; D005472:Fluorouracil