Retinal pigment epithelium exhibits gene expression and phagocytic activity alterations when exposed to retinoblastoma chemotherapeutics

Retinoblastoma (Rb) is a rare malignant disorder affecting the developing retina of children under the age of five. Chemotherapeutic agents used for treating Rb have been associated with defects of the retinal pigment epithelium (RPE), such as hyperplasia, gliosis, and mottling. Herein, we have developed two pluripotent stem cell (PSC)-RPE models to assess the cytotoxicity of known Rb chemotherapeutics such as Melphalan, Topotecan and TW-37. Our findings demonstrate that these drugs alter the RPE by decreasing the monolayer barrier's trans-epithelial resistance and affecting the cells' phagocytic activity. Transcriptional analyses demonstrate an altered expression of genes involved in melanin and retinol processing, tight junction and apical-basal polarity pathways in both models. When applied within the clinical range, none of the drug treatments caused significant cytotoxic effects, changes to the apical-basal polarity, tight junction network or cell cycle. Together, our results demonstrate that although the most commonly used Rb chemotherapeutic drugs do not cause cytotoxicity in RPE, their application in vitro leads to compromised phagocytosis and strength of the barrier function, in addition to changes in gene expression that could alter the visual cycle in vivo. Our data demonstrate that widely used Rb chemotherapeutic drugs can have a deleterious impact on RPE cells and thus great care has to be exercised with regard to their delivery so the adjacent healthy RPE is not damaged during the course of tumor eradication.