The Effects of Estrogen and Antiestrogen on Chromatin in Human Breast Cancer Cell Line, MCF-7. II.
The effects of estrogen and antiestrogen on chromatin in a human breast cancer cell line, MCF-7, were studied in cells grown in media containing 10-8 M estradiol or 10-6 M tamoxifen for 1, 3 and 8 days. The effect on incorporation of thymidine into DNA was determined. Maximal incorporation occurred on day 1 after administration of estradiol, but was depressed to a low level within 3-8 days. A small increase in incorporation was observed on 1-3 days after administration of tamoxifen, but this was also depressed to a low level within 8 days. The uptake of [32P]orthophosphate into an individual protein band was observed using sodium dodecyl sulfate-polyacrylamide gels in chromatin from the cells on day 1 after administration of estradiol and tamoxifen. The difference in the action mechanisms of estradiol and tamoxifen may be explained in part by the uptake of phosphate into individual protein. The results of the present experiments may be due to influence of either estradiol and tamoxifen on the cell cycle as well.