title: Influence of estradiol and triiodothyronine on breast cancer cell lines proliferation and expression of estrogen and thyroid hormone receptors.
abstract: OBJECTIVE
  To better understand the estrogen (E2) agonist action of triiodothyronine (T3) the effects of these hormones on ER negative MDA-MB-231 breast cancer cells were compared with those on S30, a clone of MDA-MB-231 stably transfected with ERalpha cDNA, in terms of proliferation and modulation of hormone receptors.
  
  
  RESULTS
  Growth experiments showed that MDA-MB-231 was not modulated by any hormone or tamoxifen (TAM). Treatment with E2, 10(-8)M or 10(-9)M had little effect on S30 proliferation. T3 at 10(-8)M significantly inhibited proliferation. This effect was not reverted by TAM. Treatments with 10(-8)M concentration of E2 or T3 reduced ERalpha gene expression in S30, an effect partially blocked by association with TAM, with no effect on TR expression. These results suggest that, in S30, 10(-8)M T3 has a similar action to E2 relative to ERalpha gene modulation.
  
  
  CONCLUSIONS
  Such results emphasize the need of determining T3 levels, before the introduction of antiestrogenic forms of treatment in breast cancer patients.
authors: Departamento de Clínica Médica, Universidade Estadual Paulista Júlio de Mesquista Filho, Botucatu, SP, Brasil.
authors: Sílvia Helena
authors: SH
authors: Cestari
authors: Nancy Bueno
authors: NB
authors: Figueiredo
authors: Sandro José
authors: SJ
authors: Conde
authors: Sueli
authors: S
authors: Clara
authors: Maria Lucia Hirata
authors: ML
authors: Katayama
authors: Carlos Roberto
authors: CR
authors: Padovani
authors: Maria Mitzi
authors: MM
authors: Brentani
authors: Célia Regina
authors: CR
authors: Nogueira
mesh_terms: D000704:Analysis of Variance; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D002999:Clone Cells; D004958:Estradiol / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000494:pharmacology; D005260:Female; D006801:Humans; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*; D011988:Receptors, Thyroid Hormone / Q000235:genetics / Q000378:metabolism*; D013629:Tamoxifen / Q000494:pharmacology; D014284:Triiodothyronine / Q000494:pharmacology*
chemical_list: D004965:Estrogen Antagonists; D011960:Receptors, Estrogen; D011988:Receptors, Thyroid Hormone; D014284:Triiodothyronine; D013629:Tamoxifen; D004958:Estradiol