title: Costunolide causes mitotic arrest and enhances radiosensitivity in human hepatocellular carcinoma cells.
abstract: OBJECTIVE
  This work aimed to investigate the effect of costunolide, a sesquiterpene lactone isolated from Michelia compressa, on cell cycle distribution and radiosensitivity of human hepatocellular carcinoma (HCC) cells.
  
  
  METHODS
  The assessment used in this study included: cell viability assay, cell cycle analysis by DNA histogram, expression of phosphorylated histone H3 (Ser 10) by flow cytometer, mitotic index by Liu's stain and morphological observation, mitotic spindle alignment by immunofluorescence of alpha-tubulin, expression of cell cycle-related proteins by Western blotting, and radiation survival by clonogenic assay.
  
  
  RESULTS
  Our results show that costunolide reduced the viability of HA22T/VGH cells. It caused a rapid G2/M arrest at 4 hours shown by DNA histogram. The increase in phosphorylated histone H3 (Ser 10)-positive cells and mitotic index indicates costunolide-treated cells are arrested at mitosis, not G2, phase. Immunofluorescence of alpha-tubulin for spindle formation further demonstrated these cells are halted at metaphase. Costunolide up-regulated the expression of phosphorylated Chk2 (Thr 68), phosphorylated Cdc25c (Ser 216), phosphorylated Cdk1 (Tyr 15) and cyclin B1 in HA22T/VGH cells. At optimal condition causing mitotic arrest, costunolide sensitized HA22T/VGH HCC cells to ionizing radiation with sensitizer enhancement ratio up to 1.9.
  
  
  CONCLUSIONS
  Costunolide could reduce the viability and arrest cell cycling at mitosis in hepatoma cells. Logical exploration of this mitosis-arresting activity for cancer therapeutics shows costunolide enhanced the killing effect of radiotherapy against human HCC cells.
authors.affiliation: Institute of Traditional Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Chia-Yuan
authors.initials: CY
authors.lastname: Liu
authors.forename: Hsun-Shuo
authors.initials: HS
authors.lastname: Chang
authors.forename: Ih-Sheng
authors.initials: IS
authors.lastname: Chen
authors.forename: Chih-Jen
authors.initials: CJ
authors.lastname: Chen
authors.forename: Ming-Ling
authors.initials: ML
authors.lastname: Hsu
authors.forename: Shu-Ling
authors.initials: SL
authors.lastname: Fu
authors.forename: Yu-Jen
authors.initials: YJ
authors.lastname: Chen
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000532:radiotherapy*; D002453:Cell Cycle; D002470:Cell Survival; D004247:DNA / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000532:radiotherapy*; D029562:Magnoliaceae / Q000378:metabolism; D008938:Mitosis; D010766:Phosphorylation; D010936:Plant Extracts / Q000494:pharmacology; D011836:Radiation Tolerance; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D012717:Sesquiterpenes / Q000494:pharmacology*; D007783:Lactones
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D004247:DNA; D006657:Histones; D010936:Plant Extracts; D011838:Radiation-Sensitizing Agents; D012717:Sesquiterpenes; C002602:costunolide; D007783:Lactones