title: Embryonic retinal tumors in SV40 T-Ag transgenic mice contain CD133+ tumor-initiating cells.
abstract: OBJECTIVE
  Human retinoblastomas form during the proliferative phase of retina development and are caused by mutations that result in absent or functionally defective Rb protein. Similar tumors occur in mice only when multiple Rb gene family members are absent. We asked if retinal tumors can arise from an undifferentiated retinal cell. The tumor-initiating cells isolated from these tumors that formed in early embryonic murine retinas were characterized.
  
  
  METHODS
  Transgenic mice were created using a Pax6 promoter to target expression of SV40 large T-antigen (T-Ag) in the undifferentiated murine embryonic retina. T-Ag, which sequesters all Rb family proteins and p53, is expressed in the retina and lens by murine embryonic day 10 (E10) and tumors are observed by E12.5. A cell line that is adherent in serum-containing media and forms neurospheres in supplemented serum-free media was developed from retinal tumors isolated on postnatal day 7.
  
  
  RESULTS
  In all, 1.5% of attached cells form neurospheres when transferred to serum-free medium. All cultured cells express T-Ag, confirming that they derive from the original tumors; 0.5% of adherent cells express detectable levels of CD133. CD133+ FACS-sorted cells cultured in serum-free medium form 3-fold more neurospheres than do CD133- cells. Six of seven mice injected with CD133+ cells and one of seven mice injected with CD133- cells formed tumors during a 6-month period. Unlike primary adherent cells, primary and secondary tumors heterogeneously express markers of stem cells and differentiation similar to human retinoblastoma.
  
  
  CONCLUSIONS
  CD133+ tumor-initiating cells can originate from proliferating undifferentiated precursor cells.
authors.affiliation: Texas Children's Cancer and Hematology Centers, Texas Children's Hospital, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Lalita
authors.initials: L
authors.lastname: Wadhwa
authors.forename: Wesley S
authors.initials: WS
authors.lastname: Bond
authors.forename: Laszlo
authors.initials: L
authors.lastname: Perlaky
authors.forename: Paul A
authors.initials: PA
authors.lastname: Overbeek
authors.forename: Mary Y
authors.initials: MY
authors.lastname: Hurwitz
authors.forename: Patricia
authors.initials: P
authors.lastname: Chévez-Barrios
authors.forename: Richard L
authors.initials: RL
authors.lastname: Hurwitz
mesh_terms: D000071916:AC133 Antigen; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics*; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D004195:Disease Models, Animal; D005136:Eye Proteins / Q000235:genetics; D005434:Flow Cytometry; D006023:Glycoproteins / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics; D006801:Humans; D016130:Immunophenotyping; D051379:Mice; D008822:Mice, Transgenic; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors / Q000235:genetics; D010455:Peptides / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics; D012160:Retina / Q000196:embryology*; D019572:Retinal Neoplasms / Q000196:embryology* / Q000378:metabolism / Q000473:pathology; D012175:Retinoblastoma / Q000196:embryology* / Q000378:metabolism / Q000473:pathology; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D000071916:AC133 Antigen; D015703:Antigens, CD; D000952:Antigens, Polyomavirus Transforming; D005136:Eye Proteins; D006023:Glycoproteins; D018398:Homeodomain Proteins; D000071841:PAX6 Transcription Factor; C000605730:PAX6 protein, human; C000606023:PROM1 protein, human; D051761:Paired Box Transcription Factors; C000605732:Pax6 protein, mouse; D010455:Peptides; C000606024:Prom1 protein, mouse; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53