Comparison of possible carcinogenic estradiol metabolites: effects on proliferation, apoptosis and metastasis of human breast cancer cells

Maturitas. 2006 Apr 20;54(1):72-7. doi: 10.1016/j.maturitas.2005.08.010. Epub 2005 Oct 4.


Objectives: Certain estradiol metabolites may play a pivotal role in breast carcinogenesis. Of special interest are the metabolites 2-hydroxyestradiol (2-OHE2), which can react anti-carcinogenically, and 4-hydroxyestradiol (4-OHE1) and 16a-hydroxyestrone (16-OHE1), which may have procarcinogenic potential. In the present study, we have compared for the first time the effect of these metabolites and their parent substance 17beta-estradiol (E2) on proliferation, apoptosis, apoptosis markers and markers of metastatic property of human breast cancer cells.

Methods: MCF-7 cells (human estrogen-receptor positive metastatic breast cancer cell line) were incubated with the estrogens at concentrations of 0.1-100 nM. Cell proliferation rate was measured by the ATP-assay. Apoptosis was measured by cell death assay and the apoptosis markers cytochrome C, Bcl-2, Fasl and p53 were determined in cell lysates by ELISAs. The markers of metastatic property of the cell line, VEGF and MCP-1 were measured in the cell supernatant by ELISAs.

Results: The estrogens E2, 4-OHE2 and 16-OHE1 display a proliferative effect on MCF-7 cells which is accompanied by a down-regulation of apoptosis. Various markers of apoptosis such as Bcl-2, cytochrome C and p53 appear to be involved. No significant effect was found for the metabolite 2-OHE2. VEGF and MCP-1 were up-regulated by E2 and 16-OHE1, whereas 2-OHE2 and 4-OHE2 did not show any effect.

Conclusions: The most potent estrogen regarding proliferation, apoptosis and metastasis of breast cancer cells seems to be estradiol. However, the estradiol metabolites 4-OHE2 and 16-OHE1 elicit similar properties on cell proliferation, apoptosis and metastasis as compared to estradiol but only at higher concentrations. In contrast 2-OHE2 did not show any significant effect on these parameters. Thus, intracellular estradiol metabolism may determine an individual's risk for breast carcinogenesis.

MeSH terms

  • Apoptosis / drug effects*
  • Biomarkers, Tumor / metabolism
  • Breast Neoplasms / pathology
  • Cell Line, Tumor
  • Cell Proliferation / drug effects*
  • Cytochromes c / drug effects
  • Cytochromes c / metabolism
  • Down-Regulation / drug effects
  • Enzyme-Linked Immunosorbent Assay
  • Estradiol / analogs & derivatives*
  • Estradiol / pharmacology
  • Estriol / pharmacology*
  • Estrogens / pharmacology*
  • Estrogens, Catechol
  • Fas Ligand Protein
  • Female
  • Humans
  • Membrane Glycoproteins / drug effects
  • Membrane Glycoproteins / metabolism
  • Proto-Oncogene Proteins c-bcl-2 / drug effects
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Tumor Necrosis Factors / metabolism
  • Tumor Suppressor Protein p53 / drug effects
  • Tumor Suppressor Protein p53 / metabolism
  • Up-Regulation / drug effects


  • Biomarkers, Tumor
  • Estrogens
  • Estrogens, Catechol
  • FASLG protein, human
  • Fas Ligand Protein
  • Membrane Glycoproteins
  • Proto-Oncogene Proteins c-bcl-2
  • Tumor Necrosis Factors
  • Tumor Suppressor Protein p53
  • Estradiol
  • Cytochromes c
  • 2-hydroxyestradiol
  • 4-hydroxyestradiol
  • Estriol