title: Establishment of an in vitro estrogen-dependent mouse mammary tumor model: a new tool to understand estrogen responsiveness and development of tamoxifen resistance in the context of stromal-epithelial interactions.
abstract: Currently, to our knowledge, there are no continuous cell lines derived from estrogen dependent, tamoxifen sensitive spontaneous mouse mammary carcinomas. We describe here the establishment and characterization of a cell line derived from the M05 mouse mammary tumor, LM05-Mix, composed of both an epithelial and a fibroblastic component. From it the respective epithelial LM05-E and fibroblastic LM05-F cell lines were generated by limiting dilution. Immunofluorescence studies confirmed that the epithelial cells were positive for E-cadherin, cytokeratins and vimentin whereas the fibroblastic cells were negative for the epithelial markers and positive for alpha-smooth muscle actin and vimentin. Both cell types expressed estrogen and progesterone receptors, although only the epithelial LM05-E cells were stimulated by estradiol and inhibited by tamoxifen. In the bicellular LM05-Mix cell line estradiol proved to stimulate cell proliferation whereas the response to tamoxifen was dependent on confluency and the degree of epithelial-fibroblastic interactions. The presence of membrane estrogen receptors in both cell types was suggested by the achievement of non-genomic responses to short treatments with estradiol, leading to the phosphorylation of ERK1/2. Finally, cytogenetic studies suggest that these two cell types represent independent cell populations within the tumor and would not be the result of an epithelial-mesenchymal transition. This model presents itself as a valuable alternative for the study of estrogen responsiveness and tamoxifen resistance in the context of epithelial-stromal interactions.
authors.affiliation: Area Investigación, Instituto de Oncología Angel H Roffo, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Osvaldo
authors.initials: O
authors.lastname: Pontiggia
authors.forename: Vanina
authors.initials: V
authors.lastname: Rodriguez
authors.forename: Victoria
authors.initials: V
authors.lastname: Fabris
authors.forename: Diego
authors.initials: D
authors.lastname: Raffo
authors.forename: Viviana
authors.initials: V
authors.lastname: Bumaschny
authors.forename: Gabriel
authors.initials: G
authors.lastname: Fiszman
authors.forename: Elisa Bal
authors.initials: EB
authors.lastname: de Kier Joffé
authors.forename: Marina
authors.initials: M
authors.lastname: Simian
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D015153:Blotting, Western; D045744:Cell Line, Tumor / Q000166:cytology* / Q000378:metabolism; D019008:Drug Resistance, Neoplasm / Q000502:physiology; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D005347:Fibroblasts / Q000166:cytology* / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D017404:In Situ Hybridization, Fluorescence; D020287:In Situ Nick-End Labeling; D066298:In Vitro Techniques; D008325:Mammary Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D011960:Receptors, Estrogen / Q000378:metabolism; D011980:Receptors, Progesterone / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020845:Selective Estrogen Receptor Modulators / Q000494:pharmacology; D013629:Tamoxifen / Q000494:pharmacology; D014178:Translocation, Genetic
chemical_list: D004967:Estrogens; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D020845:Selective Estrogen Receptor Modulators; D013629:Tamoxifen; D004958:Estradiol