Purchase this article with an account.
R. Margolis, N.L. Claros, D. Almeida, D. Cobrinik, D.H. Abramson, T.C. Lee; Photoreceptor Markers in Retinoblastoma Tumors . Invest. Ophthalmol. Vis. Sci. 2004;45(13):3561.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Immunohistochemical studies that have been performed on primary retinoblastoma (RB) tumors suggest that the RB is composed of neuron–committed cells. The purpose of this study was to investigate the expression of photoreceptor–associated proteins in RB cell lines and primary tumors. We studied the staining patterns of the following antibodies: AC133, which is associated with photoreceptor outer segments; neural retinal leucine zipper (NRL), a transcription factor expressed in photoreceptor progenitor cells; 7G6, a marker for human cone arrestin; and rhodopsin. Methods: The cell lines WERI–RB1 and Y79, as well as twelve primary RB tumors were used in this study. Fixed specimens were sectioned, and immunofluorescence staining was performed with AC133, NRL, 7G6, and rhodopsin antibodies using our standard protocol. The quality and distribution of the staining were recorded. Immunoprecipitation and flow cytometry for AC133 were performed on RB cell lines, as well as a western blot for NRL. Results: Cytoplasmic NRL was expressed ubiquitously in all cell lines and tumors. There were regions of membrane–bound AC133 signal in all specimens, which was brightest in the luminal aspects of rosette–forming cells. Similarly, every specimen had areas of cytoplasmic 7G6 expression. Rhodopsin was not expressed in any cell lines or primary tumors. The AC133 and NRL immunoblotting showed the correct molecular weight for both proteins, and confirmed the specificity of the immunostaining signal. Conclusions: This study provides evidence that retinoblastoma can express several photoreceptor associated markers. To our knowledge, this is the first report of the staining patterns of NRL and AC133 in primary RB tumor specimens. All tumor cells expressed cytoplasmic NRL with no evidence of nuclear NRL staining, consistent with a cone cell phenotype. There were also pockets of AC133 and 7G6 expression within each tumor. We observed that the regions of AC133 expression corresponded to areas of bright 7G6 signal. We believe that within a particular tumor, cell populations are induced to differentiate, which corresponds to expression of cone–associated markers. Unlike previous studies, we did not observe any rhodopsin expression in any of the specimens. These results suggest that retinoblastoma tumor cells may retain cone cell differentiation pathways. Future studies will identify and characterize the different histologic cell populations.
This PDF is available to Subscribers Only