Colorectal cancer (CRC) is the second-leading cause of cancer-related deaths in the United States. A number of epidemiological studies, clinical trials, and animal studies have demonstrated the chemopreventive effect of non-steroidal anti-inflammatory drugs (NSAIDs) on CRC. However, the exact mechanism by which NSAIDs suppress colorectal tumorigenesis has remained unclear. Our previous study showed that NSAID-induced death receptor signaling, along with loss of the gatekeeper APC tumor suppressor, triggers a synthetic lethal interaction and apoptotic death in an otherwise normal cell. In this study, we determined how NSAIDs induce death receptor signaling, and found a critical role of the endoplasmic reticulum (ER) stress response. Treating CRC cells with the NSAIDs sulindac or indomethacin upregulated C/EBP homologous transcription factor (CHOP), a key mediator of the ER stress response that is required for the induction of death receptor 5 (DR5) by NSAIDs. Blocking ER stress abolished the apoptotic effect of NSAIDs in CRC cells and in normal colonic epithelial cells with knockdown of APC, and also suppressed the chemopreventive activity of NSAIDs in APCMin/+ mice. Furthermore, we identified plasma membrane translocation of calreticulin in cells undergoing NSAID-induced apoptosis, suggesting the involvement of immunomodulation in this tumor suppression. Our results provide novel insight into the chemopreventive mechanism of NSAIDs, which may help design more effective chemopreventive strategies and agents.

Citation Format: Rochelle E. Fletcher, Lin Zhang, Brian Leibowitz, Jian Yu. Non-steroidal anti-inflammatory drugs induce ER stress and have an immunomodulatory role in the suppression of colorectal tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1256. doi:10.1158/1538-7445.AM2017-1256