Cancer stem cell characteristics in retinoblastoma

Mol Vis. 2005 Sep 12;11:729-37.

Abstract

Purpose: There is increasing evidence that cancer stem cells contribute to tumor progression and chemoresistance in a variety of malignancies, including brain tumors, leukemias, and breast carcinomas. In this study, we tested the hypothesis that retinoblastomas contain subpopulations of cells that exhibit cancer stem cell properties.

Methods: The following sources of retinoblastoma cells and tissues were examined for the presence of stem cell markers by immunocytochemistry: retinoblastoma tumors from mice transgenic for the SV40 T-antigen (driven by the beta-luteinizing hormone promoter), cell pellets of human Y79 and WERI-Rb27 retinoblastoma cell lines, and archival human retinoblastoma pathological specimens. Hoechst dye exclusion, mediated by the stem cell surface marker ABCG2 (ATP-binding cassette transporter, G2 subfamily), was assessed by flow cytometry in mouse tumors and WERI-Rb27 cells.

Results: Small numbers of retinoblastoma cells (less than 1%) exhibited immunoreactivity to stem cell markers ABCG2, aldehyde dehydrogenase 1 (ALDH1), MCM2 (minichromosome maintenance marker 2), SCA-1 (Stem cell antigen-1), and p63. Hoechst dye uptake in mouse tumors and WERI-Rb27 cells was enhanced by addition of 50 microM Verapamil, consistent with activity of the calcium-sensitive ABCG2 protein. Flow cytometric analysis confirmed the presence of small subpopulations of cells excluding Hoechst dye in mouse retinoblastoma tumors (0.3%) and WERI-Rb27 cells (0.1%) in a verapamil-sensitive manner. ABCG2 and ALDH1 positive cells were Hoechst-dim, as seen by dual labeling in vitro.

Conclusions: Mouse and human retinoblastoma tumor cells contain a small subpopulation of cells that exhibit a cancer stem cell-like phenotype. Especially significant is the expression of ABCG2 in mouse and human tumor cells, a calcium-sensitive cell surface protein that not only acts to exclude Hoechst dye, but also confers resistance to over 20 different chemotherapeutic agents. These findings point to a heterogeneity in retinoblastoma tumors that may have significant impact on future treatment strategies.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aldehyde Dehydrogenase / metabolism
  • Aldehyde Dehydrogenase 1
  • Animals
  • Antigens, Ly / metabolism
  • Biomarkers, Tumor / metabolism
  • Cell Cycle Proteins / metabolism
  • DNA-Binding Proteins
  • Flow Cytometry
  • Fluorescent Antibody Technique, Indirect
  • Genes, Tumor Suppressor
  • Humans
  • Immunoenzyme Techniques
  • Isoenzymes / metabolism
  • Membrane Proteins / metabolism
  • Mice
  • Mice, Transgenic
  • Microscopy, Fluorescence
  • Minichromosome Maintenance Complex Component 2
  • Neoplastic Stem Cells / metabolism
  • Neoplastic Stem Cells / pathology*
  • Nuclear Proteins / metabolism
  • Phosphoproteins / metabolism
  • Retinal Dehydrogenase
  • Retinal Neoplasms / metabolism
  • Retinal Neoplasms / pathology*
  • Retinoblastoma / metabolism
  • Retinoblastoma / pathology*
  • Trans-Activators / metabolism
  • Transcription Factors
  • Tumor Cells, Cultured
  • Tumor Suppressor Proteins

Substances

  • Aldehyde Dehydrogenase 1
  • Antigens, Ly
  • Biomarkers, Tumor
  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • Isoenzymes
  • Ly6a protein, mouse
  • Membrane Proteins
  • Nuclear Proteins
  • Phosphoproteins
  • TP63 protein, human
  • Trans-Activators
  • Transcription Factors
  • Tumor Suppressor Proteins
  • Aldehyde Dehydrogenase
  • ALDH1A1 protein, human
  • Aldh1 protein, mouse
  • Retinal Dehydrogenase
  • MCM2 protein, human
  • Minichromosome Maintenance Complex Component 2