H-ras dependent estrogenic effects of epidermal growth factor in the estrogen-independent breast cancer cell line MDA-MB-231.
A crosstalk between cellular estrogen response and receptor tyrosine kinase signaling has been shown in a variety of estrogen receptor (ER)-positive cell lines. We intended to examine the presence of estrogenic growth factor effects in an ER alpha-negative breast cancer cell line. By means of reporter gene assays, we investigated the activation of estrogen response elements (EREs) by epidermal growth factor (EGF) in the estrogen-unresponsive cell line MDA-MB-231. Our results demonstrate the H-ras-dependent activation of EREs after EGF treatment in this estrogen-unresponsive cell line, an effect which was not observed in the ERalpha/beta-positive breast cancer cell line MCF-7. In MDA-MB-231 cells, the transcriptional activity of an ERE-containing promotor was enhanced dose dependently by all tested EGF concentrations. This effect could be blocked by co-treatment with the epidermal growth factor receptor (EGFR) inhibitors AG1478 and ZD1839, as well as by co-transfection with a vector coding for a dominant negative H-ras mutant, but not by co-treatment with the pure antiestrogen ICI182,780. Furthermore, expression of constitutively active H-ras was shown to be sufficient to activate EREs in MDA-MB-231 cells. Our results suggest alternative utilization of ERE-mediated gene regulation in an estradiol-unresponsive breast cancer cell line in response to an EGF stimulus. This mechanism was shown to be dependent on EGFR and H-ras activity, but independent of the presence of functional ERalpha.
Treeck
Oliver
O
Department of Obstetrics and Gynecology, University of Regensburg, Regensburg, Germany. treeck@email.com
Weber
Angela
A
Boester
Michaela
M
Porz
Simone
S
Frey
Nicola
N
Diedrich
Klaus
K
Ortmann
Olaf
O
D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002455:Cell Division; D045744:Cell Line, Tumor; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D005260:Female; D000077267:Fulvestrant; D015972:Gene Expression Regulation, Neoplastic; D011905:Genes, ras; D006801:Humans; D009376:Neoplasms, Hormone-Dependent / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D011960:Receptors, Estrogen / Q000187:drug effects / Q000378:metabolism*; D020218:Response Elements / Q000187:drug effects
D011960:Receptors, Estrogen; D000077267:Fulvestrant; D004958:Estradiol; D004815:Epidermal Growth Factor