title: Role of COX-2 in tumorospheres derived from a breast cancer cell line.
abstract: BACKGROUND
  Cyclooxygenase-2 (COX-2) expression in primary breast cancer predicts tumor cell dissemination to bone marrow, which is a risk factor for recurrence and distant metastasis. "Stem-like" phenotype may be important in cancer metastasis.
  
  
  METHODS
  To investigate the role of COX-2 protein in breast cancer stem-like cells, we analyzed it by co-immunofluorescence in tumorospheres derived from the MCF7 estrogen receptor-positive breast cancer cell line. To evaluate COX-2 function we utilized a COX-2 inhibitor in a clonogenicity assay performed with tumorospheres-derived cells.
  
  
  RESULTS
  We detected rare cells in tumorospheres (one cell per tumorosphere) with very high COX-2 expression (COX-2(high)). COX-2 transfected MCF7 cells were able to generate long-term tumorospheres culture, even though transfection efficiency was only one in a million cells. We detected expression of OCT4 in some COX-2(high) cells, supporting the hypothesis that these cells could be cancer stem-like cells. It is important that COX-2(high) cells showed less expression of Ki-67 than did neighboring cells, indicating that COX-2(high) cells may be progenitors of tumorospheres. Celecoxib inhibited the growth of tumorosphere cultures and the ability of tumorosphere-derived cells to form colonies in vitro, indicating an active role of COX-2 in these processes. However, 2 μM celecoxib failed to eradicate tumorosphere-initiating cells. Finally, we detected rare COX-2(high) cells among SUM149 inflammatory breast cancer cells growing on plastic in serum-containing medium; the SUM149 cell line produces a very high level of COX-2 protein.
  
  
  CONCLUSIONS
  Our results support a role for COX-2 in stem-like breast cancer cells and suggest a mechanism behind a role for COX-2 in disseminated tumor cells, which are known to exhibit characteristic biomarkers and functional properties of stem-like cells.
authors.affiliation: Department of Surgical Oncology and Advanced Research Center for Microscopic Disease, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
authors.forename: Balraj
authors.initials: B
authors.lastname: Singh
authors.forename: Kendra R
authors.initials: KR
authors.lastname: Cook
authors.forename: Laura
authors.initials: L
authors.lastname: Vincent
authors.forename: Carolyn S
authors.initials: CS
authors.lastname: Hall
authors.forename: Cecilia
authors.initials: C
authors.lastname: Martin
authors.forename: Anthony
authors.initials: A
authors.lastname: Lucci
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology* / Q000503:physiopathology; D000068579:Celecoxib; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D009362:Neoplasm Metastasis / Q000503:physiopathology; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D050814:Octamer Transcription Factor-3 / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology; D011960:Receptors, Estrogen / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology
chemical_list: D052246:Cyclooxygenase 2 Inhibitors; D050814:Octamer Transcription Factor-3; C494173:POU5F1 protein, human; D011720:Pyrazoles; D011960:Receptors, Estrogen; D013449:Sulfonamides; D051546:Cyclooxygenase 2; D000068579:Celecoxib
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