title: Cadmium and proliferation in human uterine leiomyoma cells: evidence of a role for EGFR/MAPK pathways but not classical estrogen receptor pathways.
abstract: BACKGROUND
  It has been proposed that cadmium (Cd) is an environmental "metalloestrogen" and that its action is mediated via the estrogen receptor (ER). Cd mimics the effects of estrogen in the rat uterus, and blood Cd concentrations positively correlate with ER levels in uteri of women with fibroids.
  
  
  OBJECTIVE
  In the present study we explored whether Cd could stimulate proliferation of estrogen-responsive human uterine leiomyoma (ht-UtLM) cells and uterine smooth muscle cells (ht-UtSMCs) through classical interactions with ERα and ERβ, or by nongenomic mechanisms.
  
  
  METHODS
  We used estrogen response element (ERE) reporters, phosphorylated receptor tyrosine kinase arrays, Western blot analysis, estrogen binding, and cell proliferation assays to evaluate the effects of Cd on ht-UtLM cells and ht-UtSMCs.
  
  
  RESULTS
  Cd stimulated growth of both cell types at lower concentrations and inhibited growth at higher concentrations (≥ 50 μM). Cd did not significantly bind to ERα or ERβ, nor did it show transactivation in both cell types transiently transfected with ERE reporter genes. However, in both cells types, Cd (0.1 μM and 10 μM) activated p44/42 MAPK (ERK1/2), and a MAPK inhibitor (PD98059) abrogated Cd-induced cell proliferation. Cd in ht-UtLM cells, but not in ht-UtSMCs, activated the growth factor receptors EGFR, HGFR, and VEGF-R1 upstream of MAPK. Additional studies in ht-UtLM cells showed that AG1478, an EGFR inhibitor, abolished Cd-induced phosphorylation of EGFR and MAPK.
  
  
  CONCLUSIONS
  Our results show that low concentrations of Cd stimulated cell proliferation in estrogen-responsive uterine cells by nongenomic activation of MAPK, but not through classical ER-mediated pathways.
authors.affiliation: Molecular Pathogenesis Group, National Toxicology Program (NTP) Laboratory, Division of the NTP (DNTP).
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Gao
authors.forename: Linda
authors.initials: L
authors.lastname: Yu
authors.forename: Alicia B
authors.initials: AB
authors.lastname: Moore
authors.forename: Grace E
authors.initials: GE
authors.lastname: Kissling
authors.forename: Michael P
authors.initials: MP
authors.lastname: Waalkes
authors.forename: Darlene
authors.initials: D
authors.lastname: Dixon
mesh_terms: D002104:Cadmium / Q000633:toxicity*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D066246:ErbB Receptors / Q000378:metabolism; D047628:Estrogen Receptor alpha / Q000378:metabolism*; D047629:Estrogen Receptor beta / Q000378:metabolism*; D005260:Female; D006801:Humans; D007889:Leiomyoma / Q000378:metabolism / Q000473:pathology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D015398:Signal Transduction; D014594:Uterine Neoplasms / Q000378:metabolism / Q000473:pathology*
chemical_list: D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D002104:Cadmium; D066246:ErbB Receptors; D020928:Mitogen-Activated Protein Kinases