Gulp1 Is An Epigenetically Altered And Functional Tumor Suppressor In Urothelial Carcinoma Through Regulation Of Nrf2-Keap1 Signaling Axis

Abstract We identified GULP1 as a novel tumor suppressor gene (TSG) selectively silenced during urothelial cancer (UC) progression through promoter hypermethylation (PH) analyzed by quantitative methylation specific PCR (QMSP) and novel methylation specific digital droplet PCR (ddPCR) assay. Numerous cell based assays revealed that GULP1 silencing confers growth advantage to tumor cells. Correspondently, in vivo tumorigenicity after xenotransplantation of GULP1 knockdown T24 cells was significantly higher than control cells. Further mechanistic analysis revealed that GULP1 has a crucial role in the regulation of Nrf2-Keap1 axis, maintaining actin cytoskeleton architecture and helping Keap1 to scaffold Nrf2 in the cytoplasm. Moreover, GULP1 silencing induces constitutive activation of Nrf2 target signature, responsible for chemoresistance of UCs. Additionally, we analyzed GULP1 PH and expression in cisplatin-based therapy responsive and resistant primary UC samples, and in isogenic cisplatin sensitive and resistant T24 cell lines. Interestingly, GULP1 expression at transcription level was lower in both resistant primary UC samples and resistant T24 cell line. Cell lines with lower expressions of GULP1 (SW780 and UM-UC-3) also showed higher resistance to cisplatin than those with higher expression (T24 and BFTC905). Altogether, our findings determined that GULP1 is an epigenetically silenced potential TSG in UC and GULP1 expression and/or PH may guide in selecting candidate patients for cisplatin based neo-adjuvant therapy. Citation Format: Masamichi Hayashi, Elisa Guida, Rachel Goldberg, Yoshikuni Inokawa, Leonardo Reis, Akira Oki, Evgeny Izumchenko, Leonel Maldonado, Luigi Marchionni, Mariana Brait, Trinity Bivalacqua, Alexander Baras, George J. Netto, Wayne Koch, David Sidransky, Mohammad O. Hoque. GULP1 is an epigenetically altered and functional tumor suppressor in urothelial carcinoma through regulation of Nrf2-Keap1 signaling axis [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 1551. doi:10.1158/1538-7445.AM2017-1551