High throughput RNAi screen identifies NOX4 – a druggable target to treat injury-induced eye degeneration and metastatic cancers
Thursday, September 14, 2017 — Poster Session III
- KY Barbosa-Sabanero
- J Chang
- M Lal
- K Bharti
Eye injuries often induce epithelial to mesenchymal transition (EMT) in retinal pigmented epithelial (RPE) cells that reside under the retina and provide functional support for it. RPE cells undergoing EMT leave the epithelial monolayer, hyperproliferate, migrate and cause scarring in the eye leading to blindness in several cases. With the aim to determine the key molecular players involved in the EMT of the RPE, we performed a high throughput screen using a reporter induced pluripotent stem (iPS) cell line. In this iPS cell line, a green fluorescent protein (GFP) expression correlates with epithelial phenotype of RPE cells. When iPS cells are differentiated into RPE, GFP expression increases and it decreases if RPE cells undergo EMT-like processes. Mechanical scratch injury of RPE cells in culture induces EMT-like molecular processes in cells. Using a siRNA screen, we identified an enzyme NOX4, a NADPH Oxidase, whose inhibition strongly promotes epithelial phenotype in injured RPE cells. Immunostaining and gene expression studies confirmed that NOX4 plays a role in EMT. NOX4 is known to increase reactive oxygen species (ROS) levels. Indeed, higher ROS were detected at RPE injury site. Downstream of NOX4, RPE EMT is induced by upregulation of genes such as ZEB1, TGF-Beta, STAT3, and FOXO3a, which were suppressed by genetic knockdown or pharmacological inhibition of NOX4. Currently, we are testing if NOX4 inhibiting drugs can rescue RPE EMT in vivo. Furthermore, we find several similarities between RPE EMT and EMT of cancer cells leading to metastasis. Therefore, we propose that NOX4 inhibition can also be used to suppress metastatic cancers.
Category: Molecular Biology and Biochemistry