title: [Circadian rhythms of DNA synthesis and telomerase expression in hepatic cancer transplanted in nude mice].
abstract: OBJECTIVE
  To study the circadian rhythms of DNA synthesis and telomerase expression in hepatic cancer transplanted in nude mice.
  
  
  METHODS
  Sixteen BALB/C mice were synchronized with an alternative lighting regimen with 12 h for light and 12 h for darkness (12:12 LD) for 4 weeks. Hepatic cancer cells (SMMC-7721) were implanted into both flanks of each mouse. One week after transplantation, sampling from the tumor was conducted at 3, 9, 15 and 21 h after light onset (HALO). Single cell suspension was obtained and stained with propidium iodide. The cellular DNA content was measured by flow cytometry. Telomerase activity was measured by PCR-ELISA assay. Data were documented by ANOVA and Cosinor analysis.
  
  
  RESULTS
  The proportion of tumor cells in phase G1, S, G2/M and telomerase activity varied according to circadian time with statistical significance, and the telomerase activity showed a synchronized variation. The distribution curves of both phase S and the expression level of telomerase were fit for Cosinor changes.
  
  
  CONCLUSIONS
  DNA synthesis and telomerase expression of SMMC-7721 cells transplanted into the nude mice varies according to the circadian rhythm. The results provide a guidance for laying down the chemotherapy protocol for human tumors, especially when the telomerase inhibitor was used as the anti-cancer agent.
authors.forename: Yi
authors.initials: Y
authors.lastname: Qu
authors.forename: Zheng-rong
authors.initials: ZR
authors.lastname: Wang
authors.forename: Xiang
authors.initials: X
authors.lastname: Huang
authors.forename: Chun-lei
authors.initials: CL
authors.lastname: Yang
authors.forename: Bai-lin
authors.initials: BL
authors.lastname: Liu
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000502:physiology* / Q000528:radiation effects; D045744:Cell Line, Tumor; D017690:Cell Transplantation; D002940:Circadian Rhythm / Q000502:physiology* / Q000528:radiation effects; D004247:DNA / Q000096:biosynthesis* / Q000528:radiation effects; D008027:Light; D008113:Liver Neoplasms / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D017440:Photoperiod; D019098:Telomerase / Q000378:metabolism* / Q000528:radiation effects; D014407:Tumor Cells, Cultured
chemical_list: D004247:DNA; D019098:Telomerase