Histone acetylation decreased by estradiol in the MCF-7 human mammary cancer cell line.

The effect of estradiol (E2) on the [3H]-acetylation of nuclear histones was studied in the MCF-7 human mammary cancer cell line in culture. Cells (approximately 10(8) were incubated with 8 x 10(-6) M [3H]-acetate in the absence (control) or in the presence of estradiol (10(-5)-10(-8) M). After 20 min incubation, the nuclear histones were extracted and separated by electrophoresis, and each histone band was measured and calculated in DPM/mg protein. It was observed that only the H2 + H3 and H4 histones were associated with the [3H]-acetate. Estradiol (10(-6)-10(-8) M) provoked a significant inhibition in the incorporation of the acetate. The negative effect, in percentage of the non-treated cell value, was as follows: in E2 (10(-6) M): -25 +/- 10 (SE) for H2 + H3 and -26 +/- 5 for H4; in E2 (10(-7) M): -35 +/- 9 and -39 +/- 10; and in E2 (10(-8) M): -56 +/- 22 and -30 +/- 13 respectively. It is concluded that estradiol has a negative effect in the acetylation of H2, H3 and H4 histones of this mammary cancer cell; no acetylation or effect is observed in H1 histones. The relationship of this finding to the biological responses of the hormone is to be explored.