title: Is sphere assay useful for the identification of cancer initiating cells of the ovary?
abstract: OBJECTIVE
  Current evidence suggests that the presence of tumor-initiating cells (TICs) in epithelial ovarian cancer (EOC) has a role in chemoresistance and relapse. Surface markers such as CD44(+)/CD24(-), CD117(+), and CD133(+) expression have been reported as potential markers for TICs related to ovarian cancer and tumorigenic cell lines. In this study, we have investigated if spheroid forms are TIC specific or whether they can also be produced by somatic stem cells from healthy tissue in vitro. In addition, we also investigated the specificity of surface markers to identify TICs from papillary serous EOC patients.
  
  
  METHODS
  Cells were obtained from fresh tumors from 10 chemotherapy-naive patients with EOC, and cells from ovarian and tubal epithelium were obtained from 5 healthy menopausal women undergoing surgery for benign pathology and cultured in standard and in selective medium. Cells forming nonadherent spheroids were considered TICs, and the adherent cells were considered as non-TIC-like. Percentages of CD24(+), CD44(+), CD117(+), CD133(+), and vascular endothelial growth factor receptor (VEGF-R)(+) cell surface markers were analyzed by flow cytometry.
  
  
  RESULTS
  Four of 10 EOC cell tissues were excluded from the study. Tumor cells cultured in selective medium developed spheroid forms after 1 to 7 weeks in 5 of 6 EOC patients. No spheroid forms were observed in cultures of cells from healthy women. Unlike previously published data, low levels of CD24(+), CD44(+), CD117(+), and VEGF-R(+) expression were observed in spheroid cells, whereas expression of CD133(+) was moderate but higher in adherent cells from papillary serous EOC cells in comparison with adherent cells from controls.
  
  
  CONCLUSIONS
  Papillary serous EOC contains TICs that form spheroids with low expression of CD44(+), CD24(+), CD117(+) and VEGF-R(+). Further research is required to find specific surface markers to identify papillary serous TICs.
authors.affiliation: *Institut Clinic of Gynecology, Obstetrics and Neonatology, †Immunology Department, Centre de Diagnòstic Biomèdic, and ‡Institut Clinic of Hematologic Diseases and Clinical Oncology, Hospital Clínic-Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Faculty of Medicine-University of Barcelona, Barcelona, Spain.
authors.forename: María José
authors.initials: MJ
authors.lastname: Martínez-Serrano
authors.forename: Miguel
authors.initials: M
authors.lastname: Caballero-Baños
authors.forename: Ramon
authors.initials: R
authors.lastname: Vilella
authors.forename: Laura
authors.initials: L
authors.lastname: Vidal
authors.forename: Jaume
authors.initials: J
authors.lastname: Pahisa
authors.forename: Sergio
authors.initials: S
authors.lastname: Martínez-Roman
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015703:Antigens, CD / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000378:metabolism; D016022:Case-Control Studies; D002478:Cells, Cultured; D018284:Cystadenocarcinoma, Serous / Q000378:metabolism / Q000473:pathology*; D005260:Female; D005434:Flow Cytometry; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000378:metabolism / Q000473:pathology*; D009367:Neoplasm Staging; D014411:Neoplastic Stem Cells / Q000378:metabolism / Q000473:pathology*; D010051:Ovarian Neoplasms / Q000378:metabolism / Q000473:pathology*; D010053:Ovary / Q000378:metabolism / Q000473:pathology*; D010865:Pilot Projects; D011379:Prognosis; D018874:Spheroids, Cellular / Q000378:metabolism / Q000473:pathology*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D014408:Biomarkers, Tumor; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A