title: Hydroxylated estrogens (2-OH-E2 AND 4-OH-E2) do not activate cAMP/PKA and ERK1/2 pathways activation in a breast cancer MCF-7 cell line.
abstract: OBJECTIVE
  The current study was undertaken to determine the involvement of cAMP/PKA and MAPK-mediated signalling pathways in the regulation of cell proliferation by hydroxylated metabolites of 17β-estradiol (E2).
  
  
  METHODS
  MCF-7, human breast cancer cells, were cultured in phenol red-free DMEM and treated with 1 nM 2-OH-E2 or 4-OH-E2. E2 was used as a positive control. Cell proliferation was measured using the BrdU incorporation assay. Cellular levels of cAMP and PKA were determined using ELISA kits. ERK1/2 protein expression was evaluated by Western Blot analysis. To determine the involvement of different intracellular pathways in the regulation of cell proliferation appropriate activators or inhibitors were used.
  
  
  RESULTS
  Hydroxylated estrogens, as E2, exhibited no influence on cAMP accumulation and PKA activation. In concomitant treatments with forskolin, cell proliferation decreased to the amount noted under the influence of forskolin alone. A PKA inhibitor (PKI) had no statistically significant effect on proliferation stimulated by E2 and its hydroxylated metabolites. Phospho-ERK1/2 protein expression in cells stimulated with E2, 2-OH-E2 and 4-OH-E2 was not significantly different from the control. However, co-treatment with both PD98059 and E2 or its hydroxylated metabolites reversed the effect of tested compounds on cell proliferation.
  
  
  CONCLUSIONS
  We have shown that E2 hydroxylated metabolites do not activate cAMP/PKA in breast cancer cells and confirm previously published data, which showed a lack of ERK1/2 activation in a breast cancer cell line. The observed reversible action of PD98059 on cell proliferation can be explained by the fact that hydroxylated estrogens, as E2, stimulate secretion of a number of growth factors, which affect MAPK activity, suggested by Lobenhofer et al. (2000).
authors.affiliation: Department of Physiology and Toxicology of Reproduction, Jagiellonian University, Poland. ewa.gregoraszczuk@uj.edu.pl
authors.forename: P
authors.initials: P
authors.lastname: Kwiecinska
authors.forename: A
authors.initials: A
authors.lastname: Ptak
authors.forename: A
authors.initials: A
authors.lastname: Wrobel
authors.forename: E L
authors.initials: EL
authors.lastname: Gregoraszczuk
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology*; D002277:Carcinoma / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004353:Drug Evaluation, Preclinical; D004789:Enzyme Activation / Q000187:drug effects; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D004967:Estrogens / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D002393:Estrogens, Catechol; D005260:Female; D006801:Humans; D006900:Hydroxylation / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D004967:Estrogens; D002393:Estrogens, Catechol; D004958:Estradiol; C001390:2-hydroxyestradiol; C014036:4-hydroxyestradiol; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases