PT  - JOURNAL ARTICLE
AU  - Coutts, Amanda S.
AU  - Murphy, Leigh C.
TI  - Elevated Mitogen-activated Protein Kinase Activity in Estrogen-nonresponsive Human Breast Cancer Cells
DP  - 1998 Sep 15
TA  - Cancer Research
PG  - 4071--4074
VI  - 58
IP  - 18
4099  - http://cancerres.aacrjournals.org/content/58/18/4071.short
4100  - http://cancerres.aacrjournals.org/content/58/18/4071.full
SO  - Cancer Res1998 Sep 15; 58
AB  - The mitogen-activated protein kinase (MAPK) signal transduction pathway plays an essential role in cell cycle progression and can be activated by many growth factor/mitogen pathways including estrogen. MAPK has also been implicated in ligand-independent activation of estrogen receptor-α (ER-α). The development of estrogen-independent growth in breast cancer is likely a first step in progression to hormone independence and antiestrogen resistance. We examined MAPK expression and activity in T5-PRF and T5 human breast cancer cells. T5-PRF is an estrogen-nonresponsive cell line developed from T5 cells by chronically depleting the cells of estrogen in long-term culture. MAPK activity measured in vitro was significantly higher (P < 0.05) in T5-PRF compared with T5 cells. Western blot analyses showed increased levels of active dually phosphorylated MAPK in T5-PRF cell extracts compared with T5. The increased activity and expression of MAPK may contribute to the estrogen nonresponsive growth phenotype and ligand-independent activity of ER in T5-PRF cells. ©1998 American Association for Cancer Research.