Purpose:
Retinoblastoma (RB) is the most common intraoculartumor of early childhood. The early onset of RB, coupled withour previous findings of cancer stem cell characteristics inRB (Seigel, et al., 2005), led us to examine the immunoreactivityof embryonic stem cell markers as further support for stem cellinvolvement in RB carcinogenesis.
Methods:
Our RB sources included: human pathological tissues,mouse RB tumors, as well as the Y79 and WERI–RB27 humanRB cell lines. Single and dual–label immunocytochemistrywas performed with antibodies specific for human embryonic stemcell markers: SSEA–1, SSEA–4, Oct3/4, Nanog, andalkaline phosphatase, coupled with the more universal stem cellmarker ABCG2, a chemo–resistance transporter that excludesHoechst 3342 dye.
Results:
Small numbers of immunopositive cells were seen inall RB samples, as seen in the following table.
The two RB cell lines demonstrated co–localization ofOct3/4–ABCG2 and Nanog–ABCG2. RB cells that wereimmunoreactive for embryonic stem cell markers remained Hoechstdim, consistent with the activity of the ABCG2 transporter.A photomicrograph of an Oct3/4 (green) immunoreactive WERI–RB27cell that excludes the blue Hoechst counterstain accompaniesthis abstract.
Conclusions:
Small percentages of cells are immunoreactive forhuman embryonic stem cell markers in RB. The cell/tissue sourceof RB has a bearing on the immunoreactive pattern of these markers.Further studies are needed to determine whether these findingsindicate postnatal persistence of embryonic stem cell markersin RB.
Keywords: retinoblastoma • tumors • retinal development