Chemoprevention of oxidative stress-associated oral carcinogenesis by sulforaphane depends on NRF2 and the isothiocyanate moiety

// Aixian Lan 1, * , Wenjun Li 1, * , Yao Liu 1 , Zhaohui Xiong 2 , Xinyan Zhang 1 , Shanshan Zhou 3 , Olesya Palko 2 , Hao Chen 2 , Mayanga Kapita 2 , Justin R. Prigge 4 , Edward E. Schmidt 4 , Xin Chen 3 , Zheng Sun 1 , Xiaoxin Luke Chen 2 1 Department of Oral Medicine, Beijing Stomatological Hospital & School of Stomatology, Capital Medical University, Beijing 100050, China 2 Cancer Research Program, JLC-BBRI, North Carolina Central University, Durham, NC 27707, USA 3 Department of Pharmaceutical Engineering, School of Pharmaceutical & Life Sciences, Changzhou University, Jiangsu 213164, China 4 Department of Immunology and Infectious Diseases, Montana State University, Bozeman, MT 59717, USA * These authors have contributed equally to this work Correspondence to: Xin Chen, email: xinchen@cczu.edu.cn Zheng Sun, email: sunzheng12@vip.126.com Xiaoxin Luke Chen, email: lchen@nccu.edu Keywords: oral cancer, chemoprevention, NRF2, sulforaphane, 4NQO Received: May 04, 2016 Accepted: June 03, 2016 Published: July 15, 2016 ABSTRACT Oxidative stress is known to play an important role in oral cancer development. In this study we aimed to examine whether a chemical activator of NRF2, sulforaphane (SFN), may have chemopreventive effects on oxidative stress-associated oral carcinogenesis. We first showed that Nrf2 activation and oxidative damage were commonly seen in human samples of oral leukoplakia. With gene microarray and immunostaining, we found 4-nitroquinoline 1-oxide (4NQO) in drink activated the Nrf2 pathway and produced oxidative damage in mouse tongue. Meanwhile whole exome sequencing of mouse tongue identified mutations consistent with 4NQO's mutagenic profile. Using cultured human oral keratinocytes and 4NQO-treated mouse tongue, we found that SFN pre-treatment activated the NRF2 pathway and inhibited oxidative damage both in vitro and in vivo . On the contrary, a structural analogue of SFN without the isothiocyanate moiety did not have such effects. In a long-term chemoprevention study using wild-type and Nrf2 -/- mice, we showed that topical application of SFN activated the NRF2 pathway, inhibited oxidative damage, and prevented 4NQO-induced oral carcinogenesis in an Nrf2-dependent manner. Our data clearly demonstrate that SFN has chemopreventive effects on oxidative stress-associated oral carcinogenesis, and such effects depend on Nrf2 and the isothiocyanate moiety.