Activation of estrogen receptor-alpha by the heavy metal cadmium

A Stoica, B S Katzenellenbogen, M B Martin

Research output: Contribution to journalArticlepeer-review


Previous studies from this laboratory have shown that the heavy metal cadmium (Cd) mimics the effects of estradiol in estrogen-responsive breast cancer cell lines. To understand the mechanism by which cadmium activates estrogen receptor-alpha (ER-alpha), the ability of cadmium to bind to and activate wild-type and various mutants of ER-alpha was examined. When tested in transient cotransfection assays in COS-1 cells, cadmium concentrations as low as 10(-11) M activated ER-alpha. Scatchard analysis employing either purified human recombinant ER-alpha or extracts from ER-containing MCF-7 cells demonstrated that l09Cd binds to the ER with an equilibrium dissociation constant of approximately 4 to 5 x 10(-10) M. Cadmium also blocks the binding of estradiol to ER-alpha in a noncompetitive manner (K(i) = 2.96 x 10(-10) M), suggesting that the heavy metal interacts with the hormone-binding domain of the receptor. To study the role of the hormone-binding domain in cadmium activation, COS-1 cells were transiently cotransfected with GAL-ER, a chimeric receptor containing the DNA-binding domain of the transcription factor GAL4 and the hormone-binding domain of ER-alpha, and a GAL4-responsive reporter gene. Treatment of the transfected cells with either 10(-6) M cadmium or 10(-9) M estradiol resulted in a 4-fold increase in reporter gene activity. The effect of cadmium on the chimeric receptor was blocked by the antiestrogen, ICI-164,384, suggesting that cadmium activates ER-alpha through an interaction with the hormone-binding domain of the receptor. Transfection and binding assays with ER-alpha mutants identified C381, C447, E523, H524, and D538 as possible interaction sites of cadmium with the hormone-binding domain of ER-alpha.

Original languageEnglish (US)
Pages (from-to)545-53
Number of pages9
JournalMolecular endocrinology (Baltimore, Md.)
Issue number4
StatePublished - Apr 2000


  • Animals
  • Binding Sites/drug effects
  • Breast Neoplasms
  • COS Cells
  • Cadmium/metabolism
  • DNA-Binding Proteins
  • Estradiol/metabolism
  • Estrogen Receptor alpha
  • Female
  • Fungal Proteins/genetics
  • Genes, Reporter
  • Humans
  • Mutation
  • Receptors, Estrogen/drug effects
  • Recombinant Fusion Proteins/metabolism
  • Recombinant Proteins/metabolism
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors/genetics
  • Transfection
  • Tumor Cells, Cultured


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