The Nrf2 inhibitor brusatol is a potent antitumour agent in an orthotopic mouse model of colorectal cancer

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// Jonathan P. Evans 1, * , Boleslaw K. Winiarski 2, * , Paul A. Sutton 1 , Robert P. Jones 1 , Lorenzo Ressel 3 , Carrie A. Duckworth 4 , D. Mark Pritchard 4 , Zhi-Xiu Lin 5 , Vicky L. Fretwell 1 , Elizabeth M. Tweedle 1 , Eithne Costello 1 , Christopher E. Goldring 2 , Ian M. Copple 2 , B. Kevin Park 2 , Daniel H. Palmer 1, 6 and Neil R. Kitteringham 2 1 Department of Molecular and Clinical Cancer Medicine, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom 2 MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom 3 Department of Veterinary Pathology, Institute of Veterinary Science, University of Liverpool, Liverpool, United Kingdom 4 Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom 5 School of Chinese Medicine, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, People’s Republic of China 6 Clatterbridge Cancer Centre, Liverpool, United Kingdom * Joint first authorship Correspondence to: Jonathan P. Evans, email: jpevans@liverpool.ac.uk Keywords: colorectal cancer; Nrf2; brusatol; irinotecan; orthotopic syngeneic model Received: April 18, 2017 Accepted: May 07, 2018 Published: June 05, 2018 ABSTRACT Nrf2 is a transcription factor that regulates cellular stress response and irinotecan-metabolising pathways. Its aberrant activity has been reported in a number of cancers, although relatively few studies have explored a role for Nrf2 in colorectal cancer (CRC). This study assessed the expression of Nrf2 in patient CRC tissues and explored the effect of Nrf2 modulation alone, or in combination with irinotecan, in human (HCT116) and murine (CT26) cell lines in vitro and in an orthotopic syngeneic mouse model utilising bioluminescent imaging. Using a tissue microarray, Nrf2 was found to be overexpressed (p<0.01) in primary CRC and metastatic tissue relative to normal colon, with a positive correlation between Nrf2 expression in matched primary and metastatic samples. In vitro experiments in CRC cell lines revealed that Nrf2 siRNA and brusatol, which is known to inhibit Nrf2, decreased viability and sensitised cells to irinotecan toxicity. Furthermore, brusatol effectively abrogated CRC tumour growth in subcutaneously and orthotopically-allografted mice, resulting in an average 8-fold reduction in luminescence at the study end-point (p=0.02). Our results highlight Nrf2 as a promising drug target in the treatment of CRC.

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