Presence of estrogen binding sites and growth-stimulating effect of estradiol in the human myelogenous cell line HL60.

In the present study, we investigated the effects of estrogens on the growth of the HL60 line in vitro and the presence of estrogen binding sites in the same cells. Cell proliferation was estimated by cell counts, [3H]thymidine incorporation, and determination of the percentage of cells in the S phase by flow cytometry. Cells maintained in a medium containing physiological concentrations of estradiol (10(-9) M, 10(-8) M, 10(-7) M) exhibited a growth stimulation, shown by an increase in the percentage of cells in the S phase, whereas a pharmacological concentration (10(-6) M) produced a growth inhibition. Furthermore, the addition of the specific antihormone, tamoxifen, inhibited the stimulating effect of the estrogens. Receptor analysis showed the presence of specific estrogen-binding sites with an apparent dissociation constant of about 5.3 X 10(-10) M. The effect of estrogen was therefore associated with the presence of estrogen receptors in the human leukemic cell line HL60.