Dual Targeting Of Erbb-2 And Erbb-3: A New Potential Strategy For The Treatment Of Pancreatic Cancer

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Background: Pancreatic cancer (PC) is one of the most lethal cancers and there is an urgent need to find out new therapeutic approaches. Deregulated signaling through ErbB-1 and ErbB-2, members of the epidermal growth factor receptor family, frequently occurs in PC. However, attempts aiming at inhibiting ErbB-1 and ErbB-2 have revealed only a modest impact on disease outcome. A growing body of evidence suggests that ErbB-3 and its ligand NRG-1β are key players in driving oncogenic signaling and resistance to targeted therapy in PC. We have recently developed a novel humanized ErbB-3 antibody, named EV20, which displayed a potent antitumor activity by promoting receptor downregulation in vitro and in vivo. Here we hypothesized that targeting of ErbB-3 with EV20 would enhance the therapeutic effect of ErbB-2 inhibitors in PC. Materials and Methods: Three different PC cell lines (BxPC-3, HPAF II and SW1990) were chosen based on their metastatic origin, genetic background (KRAS status) and responsiveness to erlotinib. The expression of ErbB-1, ErbB-2 and ErbB-3 was analyzed by FACS and WB. The effects of trastuzumab, cetuximab, EV20 and their combinations on NRG-1β-induced activation of the ErbB3/PI3K/Akt axis, cell proliferation, and in vivo tumor growth were evaluated by standard procedures. Results: ErbB-1 was overexpressed by all the cell lines, whereas the expression levels of ErbB-2 and ErbB-3 were moderate in HPAFII cells and low in BxPC-3 and SW1990 cells. NRG-1β was more effective than EGF (an ErbB-1 ligand) in activating ErbB-3 downstream signaling, which was not inhibited by cetuximab, despite a high ErbB-1 expression in the cells. Conversely, inhibition of ErbB-2 and/or ErbB-3 resulted in a marked suppression of NRG-1β-driven Akt activation. Finally, EV20 in combination with trastuzumab exerted a superior antitumor activity compared to single agent alone in terms of cell proliferation and growth of PC xenografts in nude mice. Conclusions: Dual targeting of ErbB-2 and ErbB-3 could represent a newer therapeutic approach in PC. Note: This abstract was not presented at the meeting. Citation Format: Gianluca Sala, Reza Ghasemi, Emily Capone, Ilario Giovanni Rapposelli, Sara Traini, Cosmo Rossi, Pier Giorgio Natali, Stefano Iacobelli. Dual targeting of ErbB-2 and ErbB-3: A new potential strategy for the treatment of pancreatic cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5437. doi:10.1158/1538-7445.AM2014-5437