title: Laminin Modulates the Stem Cell Population in LM05-E Murine Breast Cancer Cells through the Activation of the MAPK/ERK Pathway.
abstract: OBJECTIVE
  We investigated the effects of laminin on the fraction of cells with self-renewing capacity in the estrogen-dependent, tamoxifen-sensitive LM05-E breast cancer cell line. We also determined whether laminin affected the response to tamoxifen.
  
  
  METHODS
  The LM05-E breast cancer cell line was used as a model for all experiments. Aldehyde dehydrogenase (ALDH) activity, clonogenic and mammosphere assays were performed to measure the effects of laminin on modulation of the stem cell subpopulation. Pluripotent gene expression was analyzed by reverse transcriptase-polymerase chain reaction. The involvement of the mitogen-activated protein kinase (MAPK)/ERK pathway was determined using specific inhibitors. The effects of laminin on the response to tamoxifenwere determined and the involvement of α6 integrin was investigated.
  
  
  RESULTS
  We found that pretreatment with laminin leads to a decrease in cells with the ability to form mammospheres that was accompanied by a decrease in ALDH activity. Moreover, exposure of mammospheres to laminin reduced the capacity to form secondary mammospheres and decreased the expression of Sox-2, Nanog, and Oct-4. We previously reported that 4-OH-tamoxifen leads to an increase in the expression of these genes in LM05-E cells. Treatment with signaling pathway inhibitors revealed that the MAPK/ERK pathway mediates the effects of laminin. Finally, laminin induced tamoxifen resistance in LM05-E cells through α6 integrin.
  
  
  CONCLUSIONS
  Our results suggest that the final number of cells with self-renewing capacity in estrogen-dependent breast tumors may result from the combined effects of endocrine treatment and microenvironmental cues.
authors.affiliation: Research Area, Instituto de Oncología "Angel H. Roffo", Ciudad de Buenos Aires, Argentina.
authors.forename: Damián E
authors.initials: DE
authors.lastname: Berardi
authors.affiliation: Research Area, Instituto de Oncología "Angel H. Roffo", Ciudad de Buenos Aires, Argentina.
authors.forename: Diego
authors.initials: D
authors.lastname: Raffo
authors.affiliation: Research Area, Instituto de Oncología "Angel H. Roffo", Ciudad de Buenos Aires, Argentina.|Members of the Research Career, Consejo Nacional de Investigaciones Científicas y Técnicas, Ciudad de Buenos Aires, Argentina.
authors.forename: Laura B
authors.initials: LB
authors.lastname: Todaro
authors.affiliation: Members of the Research Career, Consejo Nacional de Investigaciones Científicas y Técnicas, Ciudad de Buenos Aires, Argentina.|Instituto de Nanosistemas, Universidad Nacional de San Martín, Campus Miguelete, San Martín, Argentina.
authors.forename: Marina
authors.initials: M
authors.lastname: Simian
mesh_terms: D000818:Animals; D015415:Biomarkers; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D000066673:Cell Self Renewal; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D007797:Laminin / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008325:Mammary Neoplasms, Experimental; D051379:Mice; D014411:Neoplastic Stem Cells / Q000378:metabolism* / Q000473:pathology; D013629:Tamoxifen / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay
chemical_list: D015415:Biomarkers; D007797:Laminin; D013629:Tamoxifen
keywords: Breast neoplasms; Estrogen receptor alpha; Laminin; MAP kinase signaling system; Stem cells