title: [Regulation of telomerase activity and cell cycle of K562 cells by oridonin].
abstract: OBJECTIVE
  To investigate the effect of oridonin (ORI) on telomerase activity and cell cycle of human leukemic cell line K562 cells.
  
  
  METHODS
  Immunohistochemistry (IHC) technique was used to determine the expression of hTERT or C-myc. Telomerase activity was detected with TRAP-PCR-ELISA assay. In addition, the percentages of K562 cells in different cell cycle were determined by flow cytometry (FCM) at 24th and 48th hours separately after adding the different concentrations of ORI.
  
  
  RESULTS
  After the K562 cells were treated with ORI at 3.43 micromol x L(-1) for 48 h, the expression of hTERT and C-myc decreased obviously. There was statistical significant (P < 0.05) difference between experimental groups and the normal controls. In addition, the telomerase activity of K562 cells was significantly inhibited by ORI at the dose of 3.43 micromol x L(-1) for 48 h. At the same time, the cell cycle distribution changed, the percentage of G0/G1 or G2/M stages cells increased and that of the S stage cells decreased after ORI was added.
  
  
  CONCLUSIONS
  ORI can effectively inhibit telomerase activity in K562 cells. Arresting cell cycle and decreasing the expression of hTERT and C-myc may be the mechanism of action.
authors.affiliation: Henan Institute of Medical Sciences, Zhengzhou University, Zhengzhou 450052, China. liruifang1234@sohu.com
authors.forename: Rui-Fang
authors.initials: RF
authors.lastname: Li
authors.forename: Qing-Duan
authors.initials: QD
authors.lastname: Wang
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects*; D004268:DNA-Binding Proteins; D004224:Diterpenes / Q000302:isolation & purification / Q000494:pharmacology*; D045786:Diterpenes, Kaurane; D006801:Humans; D037602:Isodon / Q000737:chemistry; D020014:K562 Cells; D010946:Plants, Medicinal / Q000737:chemistry; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D019098:Telomerase / Q000378:metabolism*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D004268:DNA-Binding Proteins; D004224:Diterpenes; D045786:Diterpenes, Kaurane; D016271:Proto-Oncogene Proteins c-myc; C011959:oridonin; D019098:Telomerase