Enhanced anti-proliferative activity of the combination of tamoxifen plus HER-2-neu antibody

Breast Cancer Res Treat. 1997 Jan;42(1):1-5. doi: 10.1023/a:1005798224288.


HER-2/neu overexpression has been associated with poor prognosis in human breast cancer. Many of these cancers are also ER-positive. A logical therapeutic approach for patients who are ER-positive and overexpress HER-2/neu may be to block both the ER and the HER-2/neu pathways. In our study, we used both the MTT tetrazolium dye assay and 3H-thymidine incorporation to measure the effects of the anti-estrogen Tamoxifen or the 4D5 anti-HER-2/neu antibody alone or in combination on the growth of BT474 human breast cancer cells which express ER and overexpress HER-2/neu. We found an enhanced inhibitory effect on cell proliferation with the combination of Tamoxifen and the antibody compared to that seen by either agent alone. This simultaneous interruption of both the ER and the HER-2/neu pathways may be relevant in the clinical treatment of patients who are both ER-positive and overexpress HER-2/neu.

MeSH terms

  • Antibodies, Monoclonal / pharmacology*
  • Antineoplastic Agents, Hormonal / pharmacology*
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / pathology
  • Breast Neoplasms / therapy*
  • Cell Division / drug effects
  • DNA, Neoplasm / biosynthesis
  • Estrogen Antagonists / pharmacology*
  • Humans
  • Receptor, ErbB-2 / biosynthesis
  • Receptor, ErbB-2 / immunology*
  • Receptors, Estrogen / antagonists & inhibitors
  • Tamoxifen / pharmacology*
  • Tumor Cells, Cultured / drug effects
  • Tumor Cells, Cultured / metabolism
  • Tumor Cells, Cultured / pathology


  • Antibodies, Monoclonal
  • Antineoplastic Agents, Hormonal
  • DNA, Neoplasm
  • Estrogen Antagonists
  • Receptors, Estrogen
  • Tamoxifen
  • Receptor, ErbB-2