GULP1 regulates the NRF2-KEAP1 signaling axis in urothelial carcinoma.

Disruption of the KEAP1-NRF2 pathway results in the transactivation of NRF2 target genes, consequently inducing cell proliferation and other phenotypic changes in cancer cells. Here, we demonstrated that GULP1 was a KEAP1-binding protein that maintained actin cytoskeleton architecture and helped KEAP1 to sequester NRF2 in the cytoplasm. In urothelial carcinoma of the bladder (UCB), silencing of GULP1 facilitated the nuclear accumulation of NRF2, led to constitutive activation of NRF2 signaling, and conferred resistance to the platinum drug cisplatin. Knockdown of GULP1 in UCB cells promoted tumor cell proliferation in vitro and enhanced tumor growth in vivo. In primary UCB, GULP1 silencing was more prevalent in muscle-invasive UCB compared to nonmuscle-invasive UCB. GULP1 knockdown cells showed resistance to cisplatin treatment. In parallel with decreased GULP1 expression, we observed increased expression of NRF2, HMOX1, and other candidate antioxidant genes in cisplatin-resistant cells. Furthermore, low or no expression of GULP1 was observed in most cisplatin nonresponder cases. Silencing of GULP1 was associated with GULP1 promoter hypermethylation in cell lines and primary tumors, and a high frequency of GULP1 promoter methylation was observed in multiple sets of primary clinical UCB samples. Together, our findings demonstrate that GULP1 is a KEAP1-binding protein that regulates KEAP1-NRF2 signaling in UCB and that promoter hypermethylation of GULP1 is a potential mechanism of GULP1 silencing.

Science signaling. 2020 Aug 18*** epublish ***

Masamichi Hayashi, Elisa Guida, Yoshikuni Inokawa, Rachel Goldberg, Leonardo O Reis, Akira Ooki, Manohar Pilli, Pritam Sadhukhan, Juhyung Woo, Woonyoung Choi, Evgeny Izumchenko, Leonel Maldonado Gonzalez, Luigi Marchionni, Alex Zhavoronkov, Mariana Brait, Trinity Bivalacqua, Alexander Baras, George J Netto, Wayne Koch, Anju Singh, Mohammad O Hoque

Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA., Department of Urology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA., Department of Environmental Health Sciences, School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA., Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA., Johns Hopkins Greenberg Bladder Cancer Institute, Johns Hopkins University, Baltimore, MD 21287, USA., Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA., Insilico Medicine Inc., Emerging Technology Centers, Johns Hopkins University at Eastern, B301, 1101 33rd Street, Baltimore, MD 21218, USA., Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA. .