Purchase this article with an account.
G.M. Seigel, L.M. Campbell, M. Narayan, F. Gonzalez–Fernandez; Evidence for Cancer Stem Cells in Retinoblastoma . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3219.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
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 retinoblastoma contains subpopulations of cells that exhibit stem cell properties. Methods: Retinoblastoma tumors from LH–beta TAG mice, as well as cell pellets of human RB cell lines Y79 and WERI–RB27 were examined immunohistochemically for the presence of stem cell markers. Hoechst dye exclusion, mediated by the stem cell surface marker ABCG2, was assessed by a microtiter plate assay developed in our laboratory (Seigel, et al., Cytotechnology, in press) and confirmed by flow cytometry. Results: Small numbers of RB cells (less than 1%) exhibited immunoreactivity to stem cell markers ABCG2, Mcm2, FORSE1, SCA–1 and p63. Hoechst dye uptake was significantly enhanced by addition of 50 uM Verapamil (p< 0.001), 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 RB tumors (0.4%), WERI–RB27 cells (0.1%), as well as in non–tumorigenic R28 retinal precursor cells (0.4%). ABCG2 positive cells were always Hoechst–dim, as seen by dual labeling in vitro. Hoechst–dim/ABCG2 positive cells comprised 6.25% of the WERI–RB27 cell population, as further evidence of a stem cell phenotype. Conclusions: Mouse and human RB tumor cells contain a small subpopulation of cells that exhibit a cancer stem cell–like phenotype. Especially significant is the expression of ABCG2, a calcium–sensitive cell surface protein that not only acts to exclude Hoechst dye, but also confers resistance to over 20 different chemotherapeutic agents. Further in vitro studies are necessary to confirm self–renewal and chemoresistant properties of these cells. The existence of even a small subpopulation of chemo–resistant cancer stem cells in retinoblastoma would have a significant impact on therapeutic strategies necessary for tumor eradication.
This PDF is available to Subscribers Only