RT Journal Article
SR Electronic
T1 Elevated Mitogen-activated Protein Kinase Activity in Estrogen-nonresponsive Human Breast Cancer Cells
JF Cancer Research
JO Cancer Res
FD American Association for Cancer Research
SP 4071
OP 4074
VO 58
IS 18
A1 Coutts, Amanda S.
A1 Murphy, Leigh C.
YR 1998
UL http://cancerres.aacrjournals.org/content/58/18/4071.abstract
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.