title: A method to estimate cell cycle time and growth fraction using bromodeoxyuridine-flow cytometry data from a single sample.
abstract: BACKGROUND
  Presently available flow cytometric methods of bromodeoxyuridine (BrdUrd) labelling do not provide information on the cell cycle time (TC) and the growth fraction (GF). In this paper, we describe a novel and simple method to estimate TC and GF from flow cytometric analysis of a single tumour sample after BrdUrd labelling.
  
  
  METHODS
  The proposed method is based on two assumptions: (1) the number of labelled cells traversing the cell cycle per unit time is constant and (2) the total number of labelled cells is constant throughout the cycle, provided that cells produced after division are excluded. The total numbers of labelled divided G1 cells, labelled divided S cells, labelled undivided S cells, and labelled undivided G2 cells were obtained for DNA histograms of BrdUrd-positive cells in a collected sample. These cell numbers were used to write equations to determine the durations of cell cycle phases, TC and GF. To illustrate the application of the proposed formulae, cell cycle kinetic parameters were analysed in solid SL2 tumours growing in DBA/2 mice and in human T-leukaemia Jurkat cells in culture.
  
  
  RESULTS
  The suitability of the proposed method for estimating durations of the cell cycle phases, TC and GF was demonstrated. TC in SL2 tumours was found to be relatively constant at 4 and 10 days after tumour implantation (20.3 +/- 1.1 h and 21.6 +/- 0.9 h, respectively). GF in tumours at day 10 was lower than GF at day 4 (54.2 +/- 7.7% vs. 79.2 +/- 5.9%, p = 0.0003). Approximate values of TC and GF of cultured Jurkat cells were 23.9 h and 79.3%, respectively.
  
  
  CONCLUSIONS
  The proposed method is relatively simple and permits estimation of the cell cycle parameters, including TC and GF, from a single tumour sample after labelling with BrdUrd. We have shown that this method may be useful in preclinical studies, allowing estimation of changes in GF during growth of murine tumours. Experiments with human Jurkat cells suggest that the proposed method might also prove suitable for measurement of cell kinetics in human tumours. Development of suitable software enabling more objective interpretation of the DNA profile in this method would be desirable.
authors.affiliation: Faculty of Mathematics and Informatics, Vilnius University, Naugarduko 24, 03225 Vilnius, Lithuania. rimantas.eidukevicius@sc.vu.lt
authors.forename: Rimantas
authors.initials: R
authors.lastname: Eidukevicius
authors.forename: Dainius
authors.initials: D
authors.lastname: Characiejus
authors.forename: Ramunas
authors.initials: R
authors.lastname: Janavicius
authors.forename: Nijole
authors.initials: N
authors.lastname: Kazlauskaite
authors.forename: Vita
authors.initials: V
authors.lastname: Pasukoniene
authors.forename: Mykolas
authors.initials: M
authors.lastname: Mauricas
authors.forename: Willem
authors.initials: W
authors.lastname: Den Otter
mesh_terms: D000818:Animals; D000963:Antimetabolites / Q000494:pharmacology*; D001973:Bromodeoxyuridine / Q000494:pharmacology*; D002453:Cell Cycle; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D005260:Female; D005434:Flow Cytometry / Q000379:methods*; D016193:G1 Phase; D016195:G2 Phase; D006801:Humans; D019169:Jurkat Cells; D007700:Kinetics; D051379:Mice; D008811:Mice, Inbred DBA; D015233:Models, Statistical; D009368:Neoplasm Transplantation; D012984:Software; D013223:Statistics as Topic
chemical_list: D000963:Antimetabolites; D001973:Bromodeoxyuridine