Cancer Chemotherapy and Pharmacology

, Volume 35, Issue 6, pp 489–495 | Cite as

Synchronization of cells in the S phase of the cell cycle by 3′-azido-3′-deoxythymidine: implications for cell cytotoxicity

  • Bangaru Chandrasekaran
  • Timothy E. Kute
  • David S. Duch
Original Article AZT, S-phase Cytostasis, Cytotoxicity, DNA Histograms, 5-Fluorouracil, MTX, Flow Cytometry


The mechanism of synergy between 3′-azido-3′-deoxythymidine (AZT) and anticancer agents was inverstigated with emphasis on cell-cycle events. Exposure of exponentially growing WiDr human colon carcinoma cells to AZT resulted in synchronization of cells in the S phase of the cell cycle. Forllowing treatment with AZT at 50 or 200 μM, 62%±3% or 82%±4% of the cells were in the S phase as compared with 36%±2% in the control. Bromodeoxyuridine uptake studies revealed that the synchronized cells actively synthesized DNA. At concentrations of up to 200 μM, AZT produced a cytostatic rather than cytotoxic effect as indicated by viability and cell growth measurements. at 200 μM, AZT-induced synchronization was significant (P=<0.001) after 12 h of drug exposure, reached a maximum at 24 h, and reversed to baseline levels by 72 h even in the continued presence of the drug. This indicates that AZT-induced cytostasis is a transient and reversible effect. The cell-cycle events seen with AZT in WiDr cells were also observed in eight of nine human tumor cell lines tested. Isobologram analysis of WiDr cells preexposed to AZT for 24 h and then exposed to either AZT-5-fluorouracil or AZT-methotrexate for a further 72 h revealed synergy between AZT and the anticancer agents, indicating that AZT-induced synchronization may have therapeutic benefits.

Key words

AZT S-phase cytostasis cytotoxicity DNA histograms 5-FU MTX flow cytometry 











3-(4-5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide


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Copyright information

© Springer-Verlag 1995

Authors and Affiliations

  • Bangaru Chandrasekaran
    • 1
  • Timothy E. Kute
    • 2
  • David S. Duch
    • 1
  1. 1.Division of Cell BiologyWellcome Research LaboratoriesResearch Triangle ParkUSA
  2. 2.Department of PathologyBowman Gray School of MedicineWinston-SalemUSA

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