The anti-HER3 (ErbB3) therapeutic antibody 9F7-F11 induces HER3 ubiquitination and degradation in tumors through JNK1/2- dependent ITCH/AIP4 activation

// Christophe Le Clorennec 1, 2, 3, 4 , Yassamine Lazrek 1, 2, 3, 4, 5, 8 , Olivier Dubreuil 5, 9 , Christel Larbouret 1, 2, 3, 4 , Marie-Alix Poul 1, 2, 3, 4 , Philippe Mondon 5, 10 , Gerry Melino 6, 7 , André Pèlegrin 1, 2, 3, 4 , Thierry Chardès 1, 2, 3, 4 1 IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, F-34298, France 2 INSERM, U1194 Montpellier, Montpellier, F-34298, France 3 Université de Montpellier, Montpellier, F-34298, France 4 ICM, Institut Régional du Cancer Montpellier, Montpellier, F-34298, France 5 Millegen SA, Labège, F-31670, France 6 Biochemistry Laboratory, Instituto Dermopatico Dell'Immacolata, Department of Experimental Medicine and Surgery, University of Rome “Tor Vergata,” 00133 Rome, Italy 7 Toxicology Unit, Medical Research Council, Leicester University, Leicester LE1 9HN, United Kingdom 8 Institut Pasteur de Guyane, BP 6010, 97306, Cayenne Cedex, France 9 GamaMabs Pharma SA, Centre Pierre Potier, ONCOPOLE, BP 50624, France 10 LFB Biotechnologies, 59000, Lille, France Correspondence to: Thierry Chardès, email: thierry.chardes@inserm.fr Keywords: cancer, HER3, ITCH/AIP4, antibody, treatment Received: January 06, 2016      Accepted: April 16, 2016      Published: May 18, 2016 ABSTRACT We characterized the mechanism of action of the neuregulin-non-competitive anti-HER3 therapeutic antibody 9F7-F11 that blocks the PI3K/AKT pathway, leading to cell cycle arrest and apoptosis in vitro and regression of pancreatic and breast cancer in vivo . We found that 9F7-F11 induces rapid HER3 down-regulation. Specifically, 9F7-F11-induced HER3 ubiquitination and degradation in pancreatic, breast and prostate cancer cell lines was driven mainly by the itchy E3 ubiquitin ligase (ITCH/AIP4). Overexpression of the ITCH/AIP4 inhibitor N4BP1 or small-interfering RNA-mediated knockdown of ITCH/AIP4 inhibited HER3 ubiquitination/degradation and PI3K/AKT signaling blockade induced by 9F7-F11. Moreover, 9F7-F11-mediated JNK1/2 phosphorylation led to ITCH/AIP4 activation and recruitment to HER3 for receptor ubiquitination and degradation. ITCH/AIP4 activity was activated by the deubiquitinases USP8 and USP9X, as demonstrated by RNA interference. Taken together, our results suggest that 9F7-F11-induced HER3 ubiquitination and degradation in cancer cells mainly occurs through JNK1/2-dependent ITCH/AIP4 activation.