title: Casticin-induced apoptosis involves death receptor 5 upregulation in hepatocellular carcinoma cells.
abstract: OBJECTIVE
  To investigate the apoptotic activities of casticin in hepatocellular carcinoma (HCC) cells and its molecular mechanisms.
  
  
  METHODS
  PLC/PRF/5 and Hep G2 cell lines were cultured in vitro and the inhibitory effect of casticin on the growth of cells was detected by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolim bromide (MTT) assay. The apoptotic cell death was examined using the cell apoptosis enzyme linked immunosorbent assay (ELISA) detection kit, flow cytometry (FCM) after propidium iodide (PI) staining and DNA agarose gel electrophoresis. The caspase activities were measured using ELISA. Reactive oxygen species (ROS) production was evaluated by FCM after dichlorodihydrofluorescein diacetate (DCFH-DA) probe labeling. Intracellular glutathione (GSH) content was measured using a glutathione assay kit. The expression of death receptor (DR)4 and DR5 proteins was analyzed by Western blotting and FCM.
  
  
  RESULTS
  Casticin significantly inhibited the growth of human HCC (PLC/PRF/5 and Hep G2) cells in a dose-dependent manner (P < 0.05). Casticin increased the percentage of the sub-G1 population in HCC cells in a concentration-dependent manner. The potency of casticin to PLC/PRF/5 cells was higher than that of 5-flurouracil (26.8% ± 4.8% vs 17.4% ± 5.1%) at 10 μmol/L for 24 h. Casticin increased the levels of Histone/DNA fragmentation and the levels of active caspase-3, -8 and -9 in a concentration-dependent manner (P < 0.05). Treatment with 30 μmol/L casticin for 24 h resulted in the formation of a DNA ladder. Casticin reduced the GSH content (P < 0.05), but did not affect the level of intracellular ROS in PLC/PRF/5 and Hep G2 cells. The thiol antioxidants, acetylcysteine (NAC) and GSH restored GSH content and attenuated casticin-induced apoptosis. In contrast, the nonthiol antioxidants, butylated hydroxyanisole and mannitol failed to do so. In the HCC cells treated with casticin for 24 h, DR5 protein level was increased. The expression of DR5 protein induced by casticin was inhibited by NAC. Pretreatment with DR5/Fc chimera protein, a blocking antibody, effectively attenuated the induction of apoptosis by casticin.
  
  
  CONCLUSIONS
  Casticin-induced apoptosis of HCC cells is involved in GSH depletion and DR5 upregulation.
authors.affiliation: Department of Pathology, The Third Xiangya Hospital of Central South University, Changsha 410013, Hunan Province, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
authors.forename: Yun
authors.initials: Y
authors.lastname: Yang
authors.forename: Li
authors.initials: L
authors.lastname: Tian
authors.forename: Xi-Feng
authors.initials: XF
authors.lastname: Sheng
authors.forename: Fei
authors.initials: F
authors.lastname: Liu
authors.forename: Jian-Guo
authors.initials: JG
authors.lastname: Cao
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology / Q000627:therapeutic use; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects*; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D053938:DNA Fragmentation; D005419:Flavonoids / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D005472:Fluorouracil / Q000494:pharmacology / Q000627:therapeutic use; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D015394:Molecular Structure; D017382:Reactive Oxygen Species / Q000378:metabolism; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism*
chemical_list: D000964:Antimetabolites, Antineoplastic; D000970:Antineoplastic Agents; D005419:Flavonoids; D017382:Reactive Oxygen Species; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; C054133:casticin; D020169:Caspases; D005978:Glutathione; D005472:Fluorouracil
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