Membrane-associated binding sites for estrogen contribute to growth regulation of human breast cancer cells

Oncogene. 2001 Sep 6;20(39):5420-30. doi: 10.1038/sj.onc.1204729.

Abstract

Membrane-associated binding sites for estrogen may mediate rapid effects of estradiol-17beta that contribute to proliferation of human breast cancers. After controlled homogenization and fractionation of MCF-7 breast cancer cells, the bulk of specific estradiol binding is found in nuclear fractions. However, a significant portion of specific, high-affinity estradiol-17beta binding-sites are also enriched in plasma membranes. These estradiol binding-sites co-purify with 5'-nucleotidase, a plasma membrane-marker enzyme, and are free from major contamination by cytosol or nuclei. Electrophoresis of membrane fractions allowed detection of a primary 67-kDa protein and a secondary 46-kDa protein recognized by estradiol-17beta and by a monoclonal antibody directed to the ligand-binding domain of the nuclear form of estrogen receptor. Estrogen-induced growth of MCF-7 breast cancer cells in vitro was blocked by treatment with the antibody to estrogen receptor and correlated closely with acute hormonal activation of mitogen-activated protein kinase and Akt kinase signaling. Estrogen-promoted growth of human breast cancer xenografts in nude mice was also significantly reduced by treatment in vivo with the estrogen receptor antibody. Thus, membrane-associated forms of estrogen receptor may play a role in promoting intracellular signaling for hormone-mediated proliferation and survival of breast cancers and offer a new target for antitumor therapy.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Antibodies / pharmacology
  • Binding Sites
  • Breast Neoplasms / enzymology
  • Breast Neoplasms / pathology*
  • Cell Division / drug effects
  • Cell Membrane / metabolism
  • Estradiol / metabolism*
  • Estradiol / pharmacology*
  • Estrogen Receptor alpha
  • Female
  • Humans
  • Kinetics
  • Mice
  • Mice, Nude
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases / metabolism
  • Protein-Serine-Threonine Kinases*
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-akt
  • Receptors, Cell Surface / physiology
  • Receptors, Estrogen / antagonists & inhibitors
  • Receptors, Estrogen / chemistry
  • Receptors, Estrogen / physiology*
  • Serum Albumin, Bovine / pharmacology
  • Tumor Cells, Cultured
  • Xenograft Model Antitumor Assays

Substances

  • Antibodies
  • Estrogen Receptor alpha
  • Proto-Oncogene Proteins
  • Receptors, Cell Surface
  • Receptors, Estrogen
  • estradiol-bovine serum albumin
  • Serum Albumin, Bovine
  • Estradiol
  • AKT1 protein, human
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases