Abstract 2430: Targeting Nrf2 in esophageal adenocarcinoma sensitizes cancer cells to cisplatin treatment

Abstract

Abstract Background: The incidence rate of the esophageal adenocarcinoma (EAC) has increased rapidly among men since 1976 in the USA. EAC is considered to originate from premalignant Barrett's esophagus (BE) which results from chronic gastroesophageal reflux disease (GERD). It has been reported that oxidative stress is steadily increased in GERD-BE-EAC progression cascade. NFE2-related factor 2 (Nrf2) is a major regulator of cellular anti-oxidant properties that maintains cell viability and cellular homeostasis. Methods and Results: Using Western blot analysis, we detected overexpression of Nrf2 protein in several EAC cell lines, as compared to BE cell lines (CPA, BAR10T) and normal esophageal squamous cell lines. Nrf2 overexpression was also confirmed in primary EAC samples, using immunohistochemistry on a tissue microarray that contained 76 EACs. Knockdown of Nrf2 by siRNA or CRISPR/CAS9 in EAC cells (FLO1 and OE33), that have constitutive high levels of Nrf2, enhanced the sensitivity of cancer cells to cisplatin (CDDP). We confirmed these results by using a Nrf2 specific inhibitor (Brusatol). Further studies demonstrated that dysfunction of Nrf2, either through knockdown of Nrf2 expression or using its specific inhibitor, depleted several Nrf2 target genes such as GR, HO-1, GSTM2, GPX3 and GPX4, which have anti-oxidative properties, leading to a significant increase in cellular ROS levels. The excessive ROS levels resulted in an increase in oxidative DNA damage (measured by 8-oxoguanine) and double strand breaks (measured by p-H2AX) which were further increased by treatment with CDDP with subsequent increase in cancer cell death. Conclusion: These results indicate that constitutive overexpression of Nrf2 in EAC cells protects tumor cells from high level of ROS and favors tumor cell survival and drug resistance. Targeting Nrf2 through its specific inhibitor may have a therapeutic window in EAC. Additional studies are ongoing to determine the molecular mechanisms underlying NRF2 overexpression in EACs. Citation Format: Dunfa Peng, Tianling Hu, Shoumin Zhu, Wael El-Rifai. Targeting Nrf2 in esophageal adenocarcinoma sensitizes cancer cells to cisplatin treatment [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 2430.