title: Characterization of the stimulatory effect of medroxyprogesterone acetate and chlormadinone acetate on growth factor treated normal human breast epithelial cells.
abstract: OBJECTIVE
  Evidence is increasing that adding progestogens to hormone replacement therapy may be more harmful than beneficial, however it is debatable whether all progestogens act equally on breast cells. Mitogenic growth factors from stromal breast tissue are important in growth-regulation of breast cells, and may modify responses to progestogens. We investigated the effect of two C-21 derivatives, medroxyprogesterone acetate (MPA) and chlormadinone acetate (CMA) on growth-factor treated normal breast epithelial cells and tried to explore the underlying mechanisms of proliferation.
  
  
  METHODS
  MCF10A (human epithelial, estrogen- and progesterone-receptor negative normal breast cells) were incubated with MPA or CMA at 0.1 and 1 microM for 7 days with the growth factors (GFs) EGF, bFGF and IGF-I at 1pM. The same combinations, as well as growth factors alone, were also incubated with the proliferation inhibitors PD98059 and LY294002 at 1 microM for 4 days. Cell proliferation rate was measured by the ATP-assay.
  
  
  RESULTS
  MPA 0.1 and 1 microM, and CMA 1 microM in combination with GFs both significantly increased cell proliferation rate, with MPA having the greatest effect. MPA- and CMA-induced proliferation of GF stimulated cells was blocked by both PD98059 (selective inhibitor of MAP kinases) and LY294002 (phosphatidylinositol 3-kinase inhibitor); GF stimulated cells could not be significantly reduced by any of the inhibitors used.
  
  
  CONCLUSIONS
  MPA and CMA have a stimulatory effect on benign growth factor stimulated MCF10A cells, possibly via activation of MAP kinase and subsequent substrates and activation of PI3-kinase. GF induced proliferation appear to be mediated by pathways other than those investigated here. Growth factors and progestogens therefore have an additive, synergistic effect on cell proliferation, eliciting their effects via different pathways.
authors.affiliation: Section of Endocrinology and Menopause, University Womens' Hospital Tuebingen, Calwerstrasse 7, 72 076 Tuebingen, Germany.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Krämer
authors.forename: Harald
authors.initials: H
authors.lastname: Seeger
authors.forename: Bernhard
authors.initials: B
authors.lastname: Krämer
authors.forename: Diethelm
authors.initials: D
authors.lastname: Wallwiener
authors.forename: Alfred O
authors.initials: AO
authors.lastname: Mueck
mesh_terms: D001940:Breast / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D002715:Chlormadinone Acetate / Q000378:metabolism / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D005260:Female; D006133:Growth Substances / Q000378:metabolism*; D020249:Hormone Replacement Therapy; D006801:Humans; D017258:Medroxyprogesterone Acetate / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D006133:Growth Substances; D002715:Chlormadinone Acetate; D017258:Medroxyprogesterone Acetate