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Tyrosine kinase/p21ras/MAP-kinase pathway activation by estradiol-receptor complex in MCF-7 cells
A Migliaccio1, M Di Domenico, G Castoria
1Istituto di Patologia Generale e Oncologia, Facoltà di Medicina e Chirurgia, Napoli, Italia.
Abstract:
The mechanism by which estradiol acts on cell multiplication is still unclear. Under conditions of estradiol-dependent growth, estradiol treatment of human mammary cancer MCF-7 cells triggers rapid and transient activation of the mitogen-activated (MAP) kinases, erk-1 and erk-2, increases the active form of p21ras, tyrosine phosphorylation of Shc and p190 protein and induces association of p190 to p21ras-GAP. Both Shc and p190 are substrates of activated src and once phosphorylated, they interact with other proteins and upregulate p21ras. Estradiol activates the tyrosine kinase/p21ras/MAP-kinase pathway in MCF-7 cells with kinetics which are similar to those of peptide mitogens. It is only after introduction of the human wild-type 67 kDa estradiol receptor cDNA that Cos cells become estradiol-responsive in terms of erk-2 activity. This finding, together with the inhibition by the pure anti-estrogen ICI 182 780 of the stimulatory effect of estradiol on each step of the pathway in MCF-7 cells proves that the classic estradiol receptor is responsible for the transduction pathway activation. Transfection experiments of Cos cells with the estradiol receptor cDNA and in vitro experiments with c-src show that the estradiol receptor activates c-src and this activation requires occupancy of the receptor by hormone. Our experiments suggest that c-src is an initial and integral part of the signaling events mediated by the estradiol receptor.
Insights
Estradiol rapidly activates the MAP kinase pathway in breast cancer cells via the classic estradiol receptor. This pathway involves c-src activation, crucial for cell multiplication signaling.
Area of Science:
- Cell Biology
- Molecular Endocrinology
- Cancer Research
Background:
- The precise mechanism of estradiol's influence on cell multiplication remains incompletely understood.
- Estradiol is known to regulate various cellular processes, including proliferation, in hormone-sensitive cells.
Purpose of the Study:
- To elucidate the signaling pathway through which estradiol stimulates cell multiplication in human mammary cancer MCF-7 cells.
- To identify the role of the classic estradiol receptor and associated kinases in mediating estradiol's proliferative effects.
Main Methods:
- Utilized human mammary cancer MCF-7 cells and Cos cells transfected with estradiol receptor cDNA.
- Investigated the activation of mitogen-activated protein (MAP) kinases (erk-1, erk-2), p21ras, and tyrosine kinases (src).
- Employed anti-estrogen ICI 182 780 to block estradiol effects and performed in vitro kinase assays.
Main Results:
- Estradiol treatment rapidly activated the MAP kinase pathway, including erk-1/erk-2 and p21ras, in MCF-7 cells.
- The estradiol receptor was confirmed as essential for this pathway activation, as demonstrated by Cos cell transfection and anti-estrogen inhibition.
- Estradiol receptor activation of c-src kinase was shown to be hormone-dependent and integral to the signaling cascade.
Conclusions:
- The classic estradiol receptor initiates signaling by activating c-src, which then triggers the p21ras/MAP-kinase pathway.
- This pathway is critical for estradiol-mediated cell multiplication in human mammary cancer cells.
- Estradiol utilizes a signaling mechanism analogous to peptide mitogens, involving tyrosine kinase activation.