EFFECTS OF TAMOXIFEN ON HUMAN-BREAST CANCER CELL-CYCLE KINETICS - ACCUMULATION OF CELLS IN EARLY G1-PHASE

  • 1 January 1983
    • journal article
    • research article
    • Vol. 43  (8) , 3583-3585
Abstract
The effects of the antiestrogen tamoxifen on the cell cycle kinetics of the endocrine-responsive MCF-7 human breast cancer cells were studied. Tamoxifen inhibits proliferation of MCF-7 cells. The [3H]thymidine labeling index is markedly reduced by tamoxifen, indicating a reduction in the fraction of cells in S phase. Flow cytometry of mithramycin-stained cells reveals that cells accumulate in G1 phase, with a concomitant depletion of S- and G2-M-phase cells with tamoxifen. Mapping of G1-phase cells by morphology of prematurely condensed chromosomes demonstrated that tamoxifen-treated cells accumulate in early G1. Tamoxifen inhibits proliferation of MCF-7 human breast cancer cells by invoking a transition delay early in the G1 phase of the cell cycle.

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