Abstract 2675: Quinacrine-mediated activation of JNK1 inhibits Nrf2 and causes cell death in human colon cancer
Authors: Oh Eun-Taex , Kim Chan-Woo , Kim Ha Gyeong , Lee In-Seon , Lee Chae Won , Park Heon Joo 
Published: August 2018

Abstract
Up-regulation of Nrf2 is associated with poor prognosis in skin, breast, prostate, lung, head and neck, endometrial, and colorectal cancer, and increases chemoresistance and radioresistance by inducing antioxidant and detoxification genes. Nrf2 inhibitors are not currently available for clinical use. Here, we investigated the feasibility of using quinacrine, an old antimalarial drug, as a novel Nrf2 inhibitor for treating colorectal cancer. Immunohistochemical analysis of colorectal cancer samples from 60 patients was used to assess the correlation between Nrf2 expression levels and clinicopathological features. Using data from tumors in the Cancer Genome Atlas (n=290 normal, n=295 cancer) and publicly available data sets, we validated the correlation between Nrf2 expression and poor prognosis in colorectal cancer. The effect of quinacrine on the activation of JNK1-mediated Nrf2 degradation was analyzed with co-immunoprecipitation, immunoblotting, and luciferase reporter assays. To confirm that quinacrine-mediated Nrf2 degradation caused cancer cell death, we used Nrf2 gain-of-function and loss-of-function experiments. The cytotoxicity of quinacrine against colorectal cancer cells under both normoxia (20% O2) and hypoxia (0.5% O2) was assessed by clonogenic survival assays. Finally, a xenograft mouse model was used to confirm the results of our in vitro experiments in an in vivo setting. High Nrf2 levels were correlated with increased expression of its target genes and poor survival among colorectal cancer patients in immunohistochemical analysis and analysis for publicly available data sets. The quinacrine-mediated activation of JNK1 induced Nrf2 degradation by increasing the interaction between Keap1 and Nrf2, thereby causing cancer cell death under normoxia and hypoxia and suppressing tumor growth in our in vivo model. Overexpression of Nrf2 effectively prevented quinacrine-mediated Nrf2 degradation and cancer cell death regardless of oxygen tension. Additionally, siRNA-mediated JNK1 knockdown inhibited quinacrine-mediated Nrf2 degradation. Luciferase reporter assays and qPCR revealed that quinacrine inhibited Nrf2-mediated transcription in cancer cells under normoxia and hypoxia. Finally, the quinacrine-mediated degradation of Nrf2 was found to increase the sensitivity of colorectal cancer in in vivo model and cancer cells under both normoxia and hypoxia in vitro to ROS-inducing drugs and anticancer drugs commonly used against colorectal cancer. Quinacrine caused colorectal cancer cell death by promoting activation of JNK1-mediated Nrf2 degradation.
Citation Format: Eun-Taex Oh, Chan-Woo Kim, Ha Gyeong Kim, In-Seon Lee, Chae Won Lee, Heon Joo Park. Quinacrine-mediated activation of JNK1 inhibits Nrf2 and causes cell death in human colon cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2675.