title: Suppression of cancer stemness p21-regulating mRNA and microRNA signatures in recurrent ovarian cancer patient samples.
abstract: BACKGROUND
  Malignant ovarian disease is characterised by high rates of mortality due to high rates of recurrent chemoresistant disease. Anecdotal evidence indicates this may be due to chemoresistant properties of cancer stem cells (CSCs). However, our understanding of the role of CSCs in recurrent ovarian disease remains sparse. In this study we used gene microarrays and meta-analysis of our previously published microRNA (miRNA) data to assess the involvement of cancer stemness signatures in recurrent ovarian disease.
  
  
  METHODS
  Microarray analysis was used to characterise early regulation events in an embryonal carcinoma (EC) model of cancer stemness. This was then compared to our previously published microarray data from a study of primary versus recurrent ovarian disease. In parallel, meta-analysis was used to identify cancer stemness miRNA signatures in tumor patient samples.
  
  
  RESULTS
  Microarray analysis demonstrated a 90% difference between gene expression events involved in early regulation of differentiation in murine EC (mEC) and embryonic stem (mES) cells. This contrasts the known parallels between mEC and mES cells in the undifferentiated and well-differentiated states. Genelist comparisons identified a cancer stemness signature set of genes in primary versus recurrent data, a subset of which are known p53-p21 regulators. This signature is present in primary and recurrent or in primary alone but essentially never in recurrent tumors specifically. Meta-analysis of miRNA expression showed a much stronger cancer stemness signature within tumor samples. This miRNA signature again related to p53-p21 regulation and was expressed prominently in recurrent tumors. Our data indicate that the regulation of p53-p21 in ovarian cancer involves, at least partially, a cancer stemness component.
  
  
  CONCLUSIONS
  We present a p53-p21 cancer stemness signature model for ovarian cancer. We propose that this may, at least partially, differentially regulate the p53-p21 mechanism in ovarian disease. Targeting CSCs within ovarian cancer represents a potential therapeutic avenue.
authors.affiliation: Department of Histopathology, University of Dublin, Trinity College, Trinity Centre for Health Sciences, St James' Hospital, Dublin 8, Ireland. gallagmi@tcd.ie.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Gallagher
authors.forename: Cynthia Cbb
authors.initials: CC
authors.lastname: Heffron
authors.forename: Alexandros
authors.initials: A
authors.lastname: Laios
authors.forename: Sharon A
authors.initials: SA
authors.lastname: O'Toole
authors.forename: Brendan
authors.initials: B
authors.lastname: Ffrench
authors.forename: Paul C
authors.initials: PC
authors.lastname: Smyth
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Flavin
authors.forename: Salah A
authors.initials: SA
authors.lastname: Elbaruni
authors.forename: Cathy D
authors.initials: CD
authors.lastname: Spillane
authors.forename: Cara M
authors.initials: CM
authors.lastname: Martin
authors.forename: Orla M
authors.initials: OM
authors.lastname: Sheils
authors.forename: John J
authors.initials: JJ
authors.lastname: O'Leary