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

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.

Oncotarget. 2016 May 18 [Epub ahead of print]

Christophe Le Clorennec, Yassamine Lazrek, Olivier Dubreuil, Christel Larbouret, Marie-Alix Poul, Philippe Mondon, Gerry Melino, André Pèlegrin, Thierry Chardès

IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, F-34298, France., IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, F-34298, France., Millegen SA, Labège, F-31670, France., IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, F-34298, France., IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, F-34298, France., Millegen SA, Labège, F-31670, France., Biochemistry Laboratory, Instituto Dermopatico Dell'Immacolata, Department of Experimental Medicine and Surgery, University of Rome "Tor Vergata," 00133 Rome, Italy., IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, F-34298, France., IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, F-34298, France.