Identification of Agents That Promote Endoplasmic Reticulum Stress Using an Assay That Monitors Luciferase Secretion

Abstract

Disruption of protein processing in the secretory pathway is a measurable hallmark of endoplasmic reticulum (ER) stress. Activation of ER stress–mediated pathways has been implicated in numerous diseases, including cancer. To identify agents that induce ER stress, we established a screen for compounds that reduce secretion of the reporter protein Gaussia luciferase (GLUC). Given the clinically validated importance of targeting ER stress–mediated pathways in the treatment of multiple myeloma (MM), we used this hematological malignancy as a model for validating our screening system. From a screen of 2000 marketed drugs and natural compounds in KMS11 and ARP1 MM cells, we identified 97 agents that reduced GLUC secretion in both cell lines by at least 30%. To confirm inducers of ER stress, we applied a secondary screen that assessed splicing of the unfolded protein response (UPR) transcription factor XBP1. One agent, theaflavin-3,3′-digallate (TF-3), was chosen based on its history of safe human consumption and further validated through studies of ER stress–related pathways, including the UPR and apoptosis. Given these promising results, this screen could be a useful tool to identify agents targeting ER stress–related mechanisms in other cellular systems wherein ER stress plays a role in disease etiology.