Display Settings:


Send to:

Choose Destination
See comment in PubMed Commons below
Clin Cancer Res. 2007 Dec 1;13(23):7029-36.

Reversal of the estrogen receptor negative phenotype in breast cancer and restoration of antiestrogen response.

Author information

  • 1Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0640, USA.



In breast cancer, the presence of estrogen receptor alpha (ER) denotes a better prognosis and response to antiestrogen therapy. Lack of ERalpha correlates with overexpression of epidermal growth factor receptor or c-erbB-2. We have shown that hyperactivation of mitogen-activated protein kinase (MAPK) directly represses ERalpha expression in a reversible manner. In this study, we determine if inhibition of MAPK in established ERalpha(-) breast cancer cell lines and tumors results in reexpression of ERalpha, and further, if reexpression of ERalpha in these ERalpha(-) tumors and cell lines could restore antiestrogen responses.


Established ERalpha(-) breast cancer cell lines, ERalpha(-) breast tumors, and tumor cell cultures obtained from ERalpha(-) tumors were used in this study. Inhibition of hyperactive MAPK was accomplished via the MAPK/ERK kinase 1/2 inhibitor U0126 or via upstream inhibition with Iressa or Herceptin. Western blotting or reverse transcription-PCR for ERalpha was used to assess the reexpression of ERalpha in cells treated with U0126. Growth assays with WST-1 were done to assess restoration of antiestrogen sensitivity in these cells.


Inhibition of MAPK activity in ERalpha(-) breast cancer cell lines results in reexpression of ERalpha; upstream inhibition via targeting epidermal growth factor receptor or c-erbB-2 is equally effective. Importantly, this reexpressed ERalpha can now mediate an antiestrogen response in a subset of these ERalpha(-) breast cancer cell lines. Treatment of ERalpha(-) tumor specimens with MAPK inhibitors results in restoration of ERalpha mRNA, and similarly in epithelial cultures from ERalpha(-) tumors, MAPK inhibition restores both ERalpha protein and antiestrogen response.


These data show both the possibility of restoring ERalpha expression and antiestrogen responses in ERalpha(-) breast cancer and suggest that there exist ERalpha(-) breast cancer patients who would benefit from a combined MAPK inhibition/hormonal therapy.

Comment in

[PubMed - indexed for MEDLINE]
Free full text
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire
    Loading ...
    Write to the Help Desk