Estrogens do not modify MAP kinase-dependent nuclear signaling during stimulation of early G(1) progression in human breast cancer cells.
Estrogens are direct mitogens for hormone-responsive human breast cancercells, where they promote cell cycle progression and induce transcriptional activation of "immediate early" and cyclin genes. Nongenomic signaling by estrogens, including rapid changes of mitogen-activated protein(MAP) kinase and other signal-transduction-cascades activity, has been proposed to be essential for the mitogenic actions of these hormones and their nuclear receptors. Because regulation of gene transcription is considered a key step in cell cycle control by mitogenic protein kinase cascades, here we investigated the possibility that estrogen might induce the activation of extracellular signal-regulated kinase (Erk) 1/2-, c-Jun NH(2)-terminal kinase-, p38- or protein kinase A-responsive transcription factors in the cell nucleus during stimulation of early G(1) progression, a timing coincident with the maximum effects of these hormones on such enzyme activity. No significant changes in protein kinase-mediated transcription factor activity could be detected here after estrogen stimulation of either MCF-7 or ZR-75.1 cells. Furthermore, these steroids were able to induce activation of the human CCND1 gene promoter, accumulation of cyclin D1 and pRb phosphorylation, all key events in cell cycle stimulation by mitogens, even in the presence of Erk1/2 activation blockade by a MAP kinase-activating kinase (Mek)1/2 inhibitor. Thus, estrogens do not appear to convey significant protein kinase-dependent signaling to the cell nucleus during the early phases of human breast cancer cell stimulation. Furthermore, hormonal regulation of G(1) gene transcription can occur even without additional activation of the Mek-Erk1/2 pathway by estrogen receptors.
Caristi
S
S
Dipartimento di Patologia generale, Seconda Università degli Studi di Napoli, 80138 Napoli, Italy.
Galera
J L
JL
Matarese
F
F
Imai
M
M
Caporali
S
S
Cancemi
M
M
Altucci
L
L
Cicatiello
L
L
Teti
D
D
Bresciani
F
F
Weisz
A
A
D001943:Breast Neoplasms / Q000201:enzymology / Q000473:pathology*; D002467:Cell Nucleus / Q000201:enzymology / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D019938:Cyclin D1 / Q000096:biosynthesis / Q000235:genetics; D004958:Estradiol / Q000494:pharmacology*; D016193:G1 Phase / Q000187:drug effects* / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000502:physiology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D048728:MAP Kinase Kinase Kinase 1; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism; D014407:Tumor Cells, Cultured; D048051:p38 Mitogen-Activated Protein Kinases
D016160:Retinoblastoma Protein; D019938:Cyclin D1; D004958:Estradiol; D017346:Protein Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; C482576:MAP3K1 protein, human; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases