Tamoxifen up-regulates c-erbB-2 expression in oestrogen-responsive breast cancer cells in vitro

Eur J Cancer. 1992;28(2-3):318-21. doi: 10.1016/s0959-8049(05)80045-0.


Expression of the c-erbB-2 proto-oncogene is inhibited by oestrogens in oestrogen-responsive human breast cancer cells, at both mRNA and protein level. Here we report that, where the regulation of c-erbB-2 is concerned, tamoxifen displays a full anti-oestrogenic activity, enhancing the expression of c-erbB-2 in oestrogen receptor-positive cells cultured with untreated fetal calf serum or reversing the inhibitory effect of added oestrogens. Meanwhile, tamoxifen strongly inhibited cell growth. Tamoxifen was inactive on both c-erbB-2 expression and growth of oestrogen receptor-negative cells. These results may have important implications to explain occasional failure of tamoxifen therapy in oestrogen receptor-positive breast cancers.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Breast Neoplasms / genetics*
  • Breast Neoplasms / pathology
  • Cell Division / drug effects
  • Cell Line
  • Estrogen Antagonists / pharmacology*
  • Female
  • Gene Expression / drug effects*
  • Humans
  • In Vitro Techniques
  • Proto-Oncogene Proteins / genetics*
  • Receptor, ErbB-2
  • Tamoxifen / pharmacology*
  • Tumor Cells, Cultured / pathology
  • Up-Regulation


  • Estrogen Antagonists
  • Proto-Oncogene Proteins
  • Tamoxifen
  • Receptor, ErbB-2