Effect of prolonged hydroxytamoxifen treatment of MCF-7 cells on mitogen activated kinase cascade.
Resistance to the antiestrogen tamoxifen is the main stumbling block for the success of breast cancer therapy. We focused our study on cellular alterations induced by a prolonged treatment with the active tamoxifen metabolite hydroxytamoxifen (OHT). We show that a prolonged OHT treatment (for up to 7 days) led to a progressive increase in the level of phosphorylated p44/42 mitogen activated kinase (MAP kinase) induced by 10(-7) M TPA stimulation, without any significant change in the protein level. This effect was also observed in MCF-7 cells grown first in medium containing dextran-coated charcoal-treated FCS (DCC medium) for 20 days prior to OHT treatment, indicating a specific effect of the antiestrogen and not an effect of estrogen deprivation. It was prevented by cotreatment with estradiol and not observed in the estrogen receptor negative HeLa cell line, suggesting that it was mediated by the estrogen receptor. TPA induced phosphorylation of MEK1/2 was also raised by OHT treatment, without any change in their protein level or Raf-1 and H-Ras levels. When the MCF-7R OHT resistant cell line was grown in antiestrogen containing medium, the level of phosphorylated p44/42 MAP kinase was also high but reversed when the antiestrogen was removed. The 2 other MAP kinase, JNK and P38 pathways were not affected in the same way by OHT treatment. In conclusion, our data reveal that a prolonged OHT treatment, by increasing p44/42 MAPK activity, affects a key step in the growth control of MCF-7 cells, although not sufficiently to overcome the growth inhibitory effect of the drug.
Rabenoelina
Fanjaniriana
F
Unité 439 de l'Institut National de la Santé et de la Recherche Médicale, Montpellier, France.
Semlali
Abdelhabib
A
Duchesne
Marie-Josèphe
MJ
Freiss
Gilles
G
Pons
Michel
M
Badia
Eric
E
D000841:Anisomycin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001943:Breast Neoplasms / Q000201:enzymology*; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D005260:Female; D000077267:Fulvestrant; D011905:Genes, ras / Q000502:physiology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020935:MAP Kinase Signaling System / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000187:drug effects* / Q000201:enzymology; D048051:p38 Mitogen-Activated Protein Kinases
D000900:Anti-Bacterial Agents; D004965:Estrogen Antagonists; D011960:Receptors, Estrogen; D011994:Recombinant Proteins; D013629:Tamoxifen; D000077267:Fulvestrant; D004958:Estradiol; D000841:Anisomycin; D019908:Proto-Oncogene Proteins c-raf; 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; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D013755:Tetradecanoylphorbol Acetate