Cytokine-induced modulation of cellular proteins in retinoblastoma. Analysis by flow cytometry

Cytokines are a group of specialized, hormone-like proteins that can exert profound influences on cellular development and on a variety of cellular functions. Retinoblastoma cells are an important model for exploring human malignancy and differentiation. These multipotent embryonic cells are capable of differentiating into neuronal, glial-like and retinal pigment epithelium (RPE)-like elements. This report shows that flow cytometric analysis can be used to measure the expression of both cytoplasmic and cell surface proteins in retinoblastoma cells. The authors used this technique to monitor changes in the expression of selected cellular proteins after exposure to specific cytokines and found that MHC class I molecules were augmented by interferon-alpha (IFN-alpha) and interferon-gamma (IFN-gamma), but not by tumor necrosis factor (TNF). However, the MHC class II molecules were augmented by IFN-gamma but not by IFN-alpha or TNF. The neuronal markers, IRBP and PR-6, the glial-like marker, GFAP, and the RPE cell markers, RPE-9 and RPE-15, were not altered by any of the cytokines tested. Furthermore, IFN-gamma induced a striking enhancement of the expression of the photoreceptor cell protein, S-antigen. In contrast, IFN-alpha and TNF did not affect the expression of S-antigen. These studies show that the cytokine, IFN-gamma, can enhance a distinct cellular protein associated with cells committed to a specific cell lineage.