title: Myoepithelial and luminal breast cancer cells exhibit different responses to all-trans retinoic acid.
abstract: OBJECTIVE
  Breast cancer is the leading cause of death among women worldwide. The exact role of luminal epithelial (LEP) and myoephitelial (MEP) cells in breast cancer development is as yet unclear, as also how retinoids may affect their behaviour. Here, we set out to evaluate whether retinoids may differentially regulate cell type-specific processes associated with breast cancer development using the bi-cellular LM38-LP murine mammary adenocarcinoma cell line as a model.
  
  
  METHODS
  The bi-cellular LM38-LP murine mammary cell line was used as a model throughout all experiments. LEP and MEP subpopulations were separated using inmunobeads, and the expression of genes known to be involved in epithelial to mysenchymal transition (EMT) was assessed by qPCR after all-trans retinoic acid (ATRA) treatment. In vitro invasive capacities of LM38-LP cells were evaluated using 3D Matrigel cultures in conjunction with confocal microscopy. Also, in vitro proliferation, senescence and apoptosis characteristics were evaluated in the LEP and MEP subpopulations after ATRA treatment, as well as the effects of ATRA treatment on the clonogenic, adhesive and invasive capacities of these cells. Mammosphere assays were performed to detect stem cell subpopulations. Finally, the orthotopic growth and metastatic abilities of LM38-LP monolayer and mammosphere-derived cells were evaluated in vivo.
  
  
  RESULTS
  We found that ATRA treatment modulates a set of genes related to EMT, resulting in distinct gene expression signatures for the LEP or MEP subpopulations. We found that the MEP subpopulation responds to ATRA by increasing its adhesion to extracellular matrix (ECM) components and by reducing its invasive capacity. We also found that ATRA induces apoptosis in LEP cells, whereas the MEP compartment responded with senescence. In addition, we found that ATRA treatment results in smaller and more organized LM38-LP colonies in Matrigel. Finally, we identified a third subpopulation within the LM38-LP cell line with stem/progenitor cell characteristics, exhibiting a partial resistance to ATRA.
  
  
  CONCLUSIONS
  Our results show that the luminal epithelial (LEP) and myoephitelial (MEP) mammary LM38-P subpopulations respond differently to ATRA, i.e., the LEP subpopulation responds with increased cell cycle arrest and apoptosis and the MEP subpopulation responds with increased senescence and adhesion, thereby decreasing its invasive capacity. Finally, we identified a third subpopulation with stem/progenitor cell characteristics within the LM38-LP mammary adenocarcinoma cell line, which appears to be non-responsive to ATRA.
authors.affiliation: Research Area, Institute of Oncology "Angel H. Roffo", University of Buenos Aires, Av. San Martín 5481, C1417DTB, Buenos Aires, Argentina.
authors.forename: Damián E
authors.initials: DE
authors.lastname: Berardi
authors.forename: Carolina
authors.initials: C
authors.lastname: Flumian
authors.forename: Paola B
authors.initials: PB
authors.lastname: Campodónico
authors.forename: Alejandro J
authors.initials: AJ
authors.lastname: Urtreger
authors.forename: María I
authors.initials: MI
authors.lastname: Diaz Bessone
authors.forename: Andrea N
authors.initials: AN
authors.lastname: Motter
authors.forename: Elisa D
authors.initials: ED
authors.lastname: Bal de Kier Joffé
authors.forename: Eduardo F
authors.initials: EF
authors.lastname: Farias
authors.forename: Laura B
authors.initials: LB
authors.lastname: Todaro
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects*; D004195:Disease Models, Animal; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D047628:Estrogen Receptor alpha / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D015674:Mammary Neoplasms, Animal / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D008807:Mice, Inbred BALB C; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D018168:Receptors, Retinoic Acid / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014212:Tretinoin / Q000494:pharmacology*; D047368:Tumor Burden / Q000187:drug effects*
chemical_list: D000970:Antineoplastic Agents; D047628:Estrogen Receptor alpha; D018168:Receptors, Retinoic Acid; D014212:Tretinoin