EFFECT OF GROWTH ON THE ESTROGEN-RECEPTOR LEVELS IN MCF-7 CELLS

  • 1 January 1984
    • journal article
    • research article
    • Vol. 44  (9) , 3724-3729
Abstract
MCF-7 [human breast tumor] cells have been shown to contain estrogen receptor in several cell fractions following homogenization: nuclei, microsomes and cytosol. The amount of 17.beta.-estradiol-binding capacity found in each cellular compartment depended on the inclusion of detergent in homogenization buffers and on the use of 0.25 M sucrose in the nuclear washes. 17.beta.-Estradiol receptor (E2R) associated with nuclei (whole nuclei exchange assay, 0.6 M KCl soluble and that found on membranes sheared from crude nuclear pellets by centrifugation in 0.25 M sucrose buffer) displayed a dissociation constant (Kd) of 0.77 .+-. 0.01 (SD) nM (n = 7). Kd of the cytoplasmic (microsomes and soluble) receptors were determined to be 0.33 .+-. 0.10 nM (n = 9). Exchangeable ligand on partially purified nuclei assumed its highest level in MCF-7 cells during logarithmic growth in serum-containing media (0.8 pmol/.mu.g DNA) but declined after the culture reached confluence (0.2 pmol/.mu.g DNA). Of the nuclear E2R, 75% declined linearly after feeding MCF-7 cells in logarithmic growth phase an estrogen- and serum-free medium (t1/2 3.5 days). Another class of salt-extractable nuclear receptor (0.2 pmol/.mu.g DNA) persisted in postconfluent cultures whether fed estrogen (serum-containing media) or not (serum-free media). This residual binding capacity remained in nuclei of MCF-7 cells for an extended period of time. MCF-7 cells demonstrated functionality of E2R throughout their growth phases as evidenced by the replenishment of cytosolic E2R and the induction of progesterone receptor when given 17.beta.-estradiol.