title: Direct involvement of breast tumor fibroblasts in the modulation of tamoxifen sensitivity.
abstract: Using contact-dependent three-dimensional coculture systems and serum-free conditions, we compared the ability of estrogen receptor (ER)-alpha(+) tamoxifen-sensitive premalignant (EIII8) or tumorigenic (MCF-7), ER-alpha(+) tamoxifen-resistant (EIII8-TAM(R)) or ER-alpha(-) MDA-MB-231 breast cancer cells to interact and undergo epithelial morphogenesis on association with breast tumor-derived fibroblasts. Although all breast cancer cell lines interacted with tumor fibroblasts, EIII8 and its intrinsically tamoxifen-resistant counterpart EIII8-TAM(R) cells were most receptive and responded with dramatic, albeit, aberrant epithelial morphogenesis. EIII8 cells underwent epithelial morphogenesis when cocultured with fibroblasts from ER-alpha(-)/PgR(-) or ER-alpha(+)/PgR(+) breast tumors; however, EIII8 cells cocultured with ER-alpha(-)/PgR(-) tumor-derived fibroblasts exhibited decreased tamoxifen sensitivity compared with cells cocultured with ER-alpha(+)/PgR(+) tumor fibroblasts. Fibroblast-induced tamoxifen resistance was accompanied by mitogen-activated protein kinase and Akt hyperactivation, reduced sensitivity to U0126 or LY294002, and ER-alpha hyperphosphorylation in the activation function-1 domain. The intrinsic tamoxifen resistance of EIII8-Tam(R) cells correlated with constitutive ER-alpha hyperphosphorylation that was unaffected by the tumor fibroblasts. Our results suggest that tumor fibroblast-induced tamoxifen resistance of EIII8 cells is not mediated by epidermal growth factor receptor or insulin-like growth factor (IGF)-1R axes because no correlation was found between expression levels of IGF-1, IGF-2, phosphorylated IGF-1R, or epidermal growth factor receptor, and tamoxifen sensitivity of EIII8 fibroblast cultures.
authors: Breast Cancer Program, Karmanos Cancer Institute, Department of Pathology, Wayne State University School of Medicine, Detroit, MI 48201, USA. shekharm@karmanos.org
authors: Malathy P V
authors: MP
authors: Shekhar
authors: Steven
authors: S
authors: Santner
authors: Kathryn A
authors: KA
authors: Carolin
authors: Larry
authors: L
authors: Tait
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000503:physiopathology*; D045744:Cell Line, Tumor; D018920:Coculture Techniques; D019008:Drug Resistance, Neoplasm / Q000502:physiology*; D047628:Estrogen Receptor alpha / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000502:physiology*; D006801:Humans; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011980:Receptors, Progesterone / Q000378:metabolism; D020845:Selective Estrogen Receptor Modulators / Q000494:pharmacology*; D013629:Tamoxifen / Q000494:pharmacology*; D014158:Transcription, Genetic
chemical_list: D047628:Estrogen Receptor alpha; D011980:Receptors, Progesterone; D020845:Selective Estrogen Receptor Modulators; D013629:Tamoxifen; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases