EFFECTS OF ESTROGEN AND ANTI-ESTROGEN ON DNA-POLYMERASE IN HUMAN-BREAST CANCER

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  • 1 January 1980
    • journal article
    • research article
    • Vol. 40  (5) , 1722-1726
Abstract
The effects of estrogens and antiestrogens on cellular DNA-dependent DNA polymerase activity in human breast cancer were studied, using as a model the MCF-7 human breast cancer cell line which contains estrogen receptor. 17.beta.-Estradiol had little if any effect on cytosol DNA polymerase activity or growth (total DNA per flask) of MCF-7 cells. Incubation of the cells for 4-6 days with the antiestrogen nafoxidine, however, resulted in a dose-dependent reduction in cytosol DNA polymerase activity to 1/2 that observed in untreated cells. Enzyme activity in antiestrogen-treated cells was restored to levels contained in untreated cells by removing antiestrogen from the growth medium and incubating the cells for an additional 4 days with 17.beta.-estradiol. The restoration required estrogenic steroids specifically, and the time course, magnitude, and dose dependence of the response were similar to estrogen-stimulated increases in DNA polymerase activity described in other estrogen target tissues. Estrogen-mediated reversal of antiestrogen suppression of DNA polymerase activity was paralleled by increases in total DNA synthesis.