A novel mechanism of action of HER2 targeted immunotherapy is explained by inhibition of NRF2 function in ovarian cancer cells

// Hilal S. Khalil 1 , Simon P. Langdon 3 , Alexey Goltsov 1 , Tero Soininen 1 , David J. Harrison 4 , James Bown 2 , Yusuf Y. Deeni 1 1 Division of Science, School of Science, Engineering and Technology, Abertay University, Dundee, DD1 1HG, United Kingdom 2 Division of Computing and Mathematics, School of Arts, Media, and Computer Games, Abertay University, Dundee, DD1 1HG, United Kingdom 3 Division of Pathology, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh, EH4 2XU, United Kingdom 4 School of Medicine, University of St Andrews, St Andrews, KY16 9TF, United Kingdom Correspondence to: Yusuf Y. Deeni, email: y.deeni@abertay.ac.uk Keywords: Pertuzumab/Trastuzumab, NRF2, ROS, HER2-targeted, cancer-immunotherapeutics Received: June 29, 2016      Accepted: September 21, 2016      Published: October 04, 2016 ABSTRACT Nuclear erythroid related factor-2 (NRF2) is known to promote cancer therapeutic detoxification and crosstalk with growth promoting pathways. HER2 receptor tyrosine kinase is frequently overexpressed in cancers leading to uncontrolled receptor activation and signaling. A combination of HER2 targeting monoclonal antibodies shows greater anticancer efficacy than the single targeting antibodies, however, its mechanism of action is largely unclear. Here we report novel actions of anti-HER2 drugs, Trastuzumab and Pertuzumab, involving NRF2. HER2 targeting by antibodies inhibited growth in association with persistent generation of reactive oxygen species (ROS), glutathione (GSH) depletion, reduction in NRF2 levels and inhibition of NRF2 function in ovarian cancer cell lines. The combination of antibodies produced more potent effects than single antibody alone; downregulated NRF2 substrates by repressing the Antioxidant Response (AR) pathway with concomitant transcriptional inhibition of NRF2 . We showed the antibody combination produced increased methylation at the NRF2 promoter consistent with repression of NRF2 antioxidant function, as HDAC and methylation inhibitors reversed such produced transcriptional effects. These findings demonstrate a novel mechanism and role for NRF2 in mediating the response of cancer cells to the combination of Trastuzumab and Pertuzumab and reinforce the importance of NRF2 in drug resistance and as a key anticancer target.