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Jennifer Rha, Salma Ferdous, Micah A Chrenek, Maxwell Griffin, Jeffrey H Boatright, Hans E Grossniklaus, John M Nickerson; Treatment of retinoblastoma cells with TCP induces dose-dependent cell death. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2337.
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Retinoblastoma (RB) is the most common intraocular tumor in children, Some cells in RB tumors are resistant to chemotherapy, presumably because they are differentiated and not proliferating. Lysine-specific demethylase 1 (LSD1) is responsible for numerous epigenetic modifications in various cancers. Based on work from our lab showing high Lsd1 expression in differentiating retinal cells, we hypothesize that LSD1 is highly expressed in differentiated retinoblastoma cells and that pharmacological LSD1 inhibition will kill them. To test this, we treated differentiating cultures of WERI-Rb-1 cells with tranylcypromine (TCP), an inhibitor of LSD1, and assessed cell viability.
We differentiated WERI-Rb-1 cells using a published method (Liu IJMM 40:4:1172 2017) and validating by probing for differentiation markers and LSD1 expression by ddPCR and western blotting. To determine the effect of LSD1 inhibition, we treated differentiated and undifferentiated WERI-Rb-1 cultures with TCP. We used two independent assays (MTT and LIVE/DEAD Viability/Cytotoxicity) to assess for cell viability. Experiments were performed in technical and biological triplicates (n=3).
Our data show that LSD1 is highly expressed in well-differentiated areas of the cultures. Differentiation induced higher expression of a marker of differentiation, neuronal differentiation 1 (NEUROD1), and lower expression of nestin (NES) mRNA, a neural stem/progenitor cell marker, when compared to undifferentiated RB cells. Both differentiated and undifferentiated cells express LSD1 at both the transcript and protein levels. Notably, TCP (2.5-20mM) treatment of differentiated and undifferentiated cells decreased cell viability in a dose-dependent manner.
TCP treatment killed both differentiated and undifferentiated WERI-Rb-1 cells in culture. LSD1 may thus be critical for the survival of WERI-Rb-1 cells. LSD1 inhibitors, such as tranylcypromine (TCP), are currently being tested in clinical trials as novel therapeutic approaches to disable the pro-oncogenic epigenome of various cancers, though not yet including RB (Hosseini Epigenomics 2017). Implicating LSD1 in the tumorigenesis of well-differentiated RB has immediate applications for translational research, as TCP is an FDA-approved psychiatric medication. In the future, LSD1 inhibitors such as TCP may be used in conjunction with current chemotherapeutics to treat RB.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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