title: Gene set enrichment analysis provides insight into novel signalling pathways in breast cancer stem cells.
abstract: BACKGROUND
  Tumour-initiating cells (TICs) or cancer stem cells can exist as a small population in malignant tissues. The signalling pathways activated in TICs that contribute to tumourigenesis are not fully understood.
  
  
  METHODS
  Several breast cancer cell lines were sorted with CD24 and CD44, known markers for enrichment of breast cancer TICs. Tumourigenesis was analysed using sorted cells and total RNA was subjected to gene expression profiling and gene set enrichment analysis (GSEA).
  
  
  RESULTS
  We showed that several breast cancer cell lines have a small population of CD24(-/low)/CD44(+) cells in which TICs may be enriched, and confirmed the properties of TICs in a xenograft model. GSEA revealed that CD24(-/low)/CD44(+) cell populations are enriched for genes involved in transforming growth factor-beta, tumour necrosis factor, and interferon response pathways. Moreover, we found the presence of nuclear factor-kappaB (NF-kappaB) activity in CD24(-/low)/CD44(+) cells, which was previously unrecognised. In addition, NF-kappaB inhibitor dehydroxymethylepoxyquinomicin (DHMEQ) prevented tumourigenesis of CD24(-/low)/CD44(+) cells in vivo.
  
  
  CONCLUSIONS
  Our findings suggest that signalling pathways identified using GSEA help to identify molecular targets and biomarkers for TIC-like cells.
authors.affiliation: Division of Systems Biomedical Technology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Murohashi
authors.forename: K
authors.initials: K
authors.lastname: Hinohara
authors.forename: M
authors.initials: M
authors.lastname: Kuroda
authors.forename: T
authors.initials: T
authors.lastname: Isagawa
authors.forename: S
authors.initials: S
authors.lastname: Tsuji
authors.forename: S
authors.initials: S
authors.lastname: Kobayashi
authors.forename: K
authors.initials: K
authors.lastname: Umezawa
authors.forename: A
authors.initials: A
authors.lastname: Tojo
authors.forename: H
authors.initials: H
authors.lastname: Aburatani
authors.forename: N
authors.initials: N
authors.lastname: Gotoh
mesh_terms: D000818:Animals; D001549:Benzamides / Q000494:pharmacology / Q000627:therapeutic use; D015415:Biomarkers; D001943:Breast Neoplasms / Q000235:genetics / Q000473:pathology*; D051927:CD24 Antigen / Q000032:analysis*; D002469:Cell Separation / Q000379:methods*; D003512:Cyclohexanones / Q000494:pharmacology / Q000627:therapeutic use; D005260:Female; D020869:Gene Expression Profiling; D005822:Genetic Vectors / Q000494:pharmacology; D006801:Humans; D018960:Hyaluronan Receptors / Q000032:analysis*; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000502:physiology; D009363:Neoplasm Proteins / Q000032:analysis* / Q000037:antagonists & inhibitors / Q000502:physiology; D014411:Neoplastic Stem Cells / Q000737:chemistry / Q000502:physiology* / Q000637:transplantation; D020411:Oligonucleotide Array Sequence Analysis; D015398:Signal Transduction / Q000502:physiology; D014161:Transduction, Genetic; D023041:Xenograft Model Antitumor Assays
chemical_list: D001549:Benzamides; D015415:Biomarkers; D051927:CD24 Antigen; C497889:CD24 protein, human; C497483:CD44 protein, human; D003512:Cyclohexanones; D018960:Hyaluronan Receptors; D016328:NF-kappa B; D009363:Neoplasm Proteins; C464444:dehydroxymethylepoxyquinomicin