Original ArticlesThe anti-HER3 antibody in combination with trastuzumab exerts synergistic antitumor activity in HER2-positive gastric cancer
Introduction
Gastric cancer (GC) is the third most common cause of cancer-related deaths worldwide, accounting for 723,000 deaths per year [1]. However, clinical approaches for treatment of GC are limited and the median survival for advanced (AGC) remains around 8 to 10 months [2]. Trastuzumab, a monoclonal antibody against human epidermal growth factor receptor 2 (HER2), is hitherto the only targeted biologic agent that has been demonstrated to confer overall survival benefit in the first-line treatment of HER2-positive AGC [3], and thus it is widely used in clinic. Nevertheless, the objective response rate of trastuzumab combined with chemotherapy was only 47%, and even initially responsive patients mostly suffered from progression within one year due to de novo or acquired resistance [3]. Thus, there is an urgent need to develop new therapeutic strategies that could overcome the limited efficacy of trastuzumab.
There are many proposed mechanisms underlying trastuzumab resistance [4]. Recent studies have shown that the activation of HER3 signaling plays a significant role in HER2-positive GC [5], [6]. HER3 is a kinase dead member of the HER family [7], whereas HER2 has no known ligand [8]. Although HER2 and HER3 are functionally incomplete on their own, their heterodimer formed in both ligand-dependent and ligand-independent manners [9] is the key activator of PI3K/AKT signaling in HER2-driven cancers [10], [11]. Prior studies have suggested that the compensatory resumed HER3 signaling is driven by high level of hetero-dimerization partner HER2 [12] or by PI3K/AKT driven inhibitory feedback loop in the presence of trastuzumab [13], [14]. Besides, elevated expression of the predominant ligand for HER3, neuregulin1 (NRG1), may drive the ligand-dependent HER3 signaling in GC and many other types of tumors [15], [16], [17]. Trastuzumab is able to block HER2–HER3 dimerization that occur in the absence of ligands by binding to domain IV of HER2 extracellular domain (ECD) [18], but it is not effective in blocking ligand-dependent HER2–HER3 dimerization, which is required to bind to domain II of HER2–ECD, resulting in unrestrained ligand-dependent HER3 signaling [9]. The inability of trastuzumab of fully inhibiting HER3 signaling and consequent PI3K/AKT signaling is considered as a reason for its limited therapeutic benefit [19].
In this regard, HER3 is emerging as a key target for complete blockade of the signaling pathway, in purpose of improving theefficacy of trastuzumab. While the rationale for HER3 blockage in GC is mainly rooted in previous experience with breast cancer [5], [20], [21]. Therapeutic targeting of HER3 in combination with trastuzumab need to be evaluated in GC [22]. Following this rationale, the HER3-targeted humanized monoclonal antibodies, 1A5 and 3D4, were developed. The two anti-HER3 antibodies bind to different epitopes of HER3, allowing them to simultaneously block both ligand-dependent and ligand-independent HER3 signaling. The aim of this study was to investigate the potential synergetic effects of a combination of anti-HER3 antibody and trastuzumab targeting HER2 and HER3 and its underlying mechanisms in the treatment of HER2-positive GC.
Section snippets
Reagents and antibodies
Trastuzumab (Herceptin) was purchased from Shanghai Roche Pharmaceutical Ltd., the anti-HER3 antibodies, 3D4 and 1A5, were produced by Beijing Cotimes Biotech Co.,Ltd (Patent Number: CN104011079A). NRG1 (rhNRG1-β1) was purchased from R&D Systems (396-HB-050). The HER2 (#4290), HER3 (#12708), p-HER3 (#2842), AKT (#4691), p-AKT (#4060), ERK (#4695), p-ERK (#4370), S6 (#2217), p-S6 (#4858) antibodies were purchased from Cell Signaling Technology. The anti-β-actin antibody (Lot#014M4759) was
Combination of 1A5–3D4 with trastuzumab synergistically inhibited cell proliferation and both PI3K/AKT and ERK pathways in HER2-positive GC cells
1A5 and 3D4 are two different antibodies designed to bind to sub-domains of HER3 without overlapping epitopes that allows them to simultaneously bind HER3. 1A5 inhibited HER3 phosphorylation irrespective with the levels of NRG1, whereas 3D4 can effectively prevent ligand-dependent phosphorylation of HER3 (Fig. S1A). Compared to 1A5 or 3D4 combined with trastuzumab, the combination of 1A5 and 3D4 (hereafter called 1A5–3D4) combined with trastuzumab showed more significantly synergistic effects
Discussion
Although clinical benefit has been well-established with trastuzumab, more potent targeted therapies for HER2 positive GC is necessary to overcome its limitation in efficacy. As the preferred dimerization partner for HER2, HER3 is a crucial activator with respect to the strength of interaction and downstream signaling. As HER3 lacks innate kinase activity, attention has been placed on targeting the HER3-ECD through antibodies, including antagonizing ligand binding to the ECD and blocking the
Conflict of interest
All the authors declare that they had no conflict of interest.
Acknowledgments
This study was supported by grants from National Natural Science Foundation of China (No. 81301915).
References (32)
- et al.
Advanced gastric cancer – slow but steady progress
Cancer Treat. Rev
(2010) - et al.
Trastuzumab in combination with chemotherapy versus chemotherapy alone for treatment of HER2-positive advanced gastric or gastro-oesophageal junction cancer (ToGA): a phase 3, open-label, randomised controlled trial
Lancet
(2010) - et al.
Resistance to human epidermal growth factor receptor type 2-targeted therapies
Eur. J. Cancer
(2014) - et al.
Neuregulin-1-mediated autocrine signaling underlies sensitivity to HER2 kinase inhibitors in a subset of human cancers
Cancer Cell
(2011) - et al.
Ligand-independent HER2/HER3/PI3K complex is disrupted by trastuzumab and is effectively inhibited by the PI3K inhibitor GDC-0941
Cancer Cell
(2009) - et al.
Targeting ligand-activated ErbB2 signaling inhibits breast and prostate tumor growth
Cancer Cell
(2002) - et al.
The anti-erbB3 antibody MM-121/SAR256212 in combination with trastuzumab exerts potent antitumor activity against trastuzumab-resistant breast cancer cells
Mol. Cancer
(2013) - et al.
HER2 in gastric cancer: a new prognostic factor and a novel therapeutic target
Ann. Oncol
(2008) - et al.
Cancer incidence and mortality worldwide: sources, methods and major patterns in GLOBOCAN 2012
Int. J. Cancer
(2015) - et al.
Molecular pathways: HER3 targeted therapy
Clin. Cancer Res
(2014)
Sustained inhibition of HER3 and EGFR is necessary to induce regression of HER2-amplified gastrointestinal carcinomas
Clin. Cancer Res
Insect cell-expressed p180erbB3 possesses an impaired tyrosine kinase activity
Proc. Natl. Acad. Sci. U.S.A.
The ErbB-2/HER2 oncoprotein of human carcinomas may function solely as a shared coreceptor for multiple stroma-derived growth factors
Proc. Natl. Acad. Sci. U.S.A.
Novel anticancer targets: revisiting ERBB2 and discovering ERBB3
Nat. Rev. Cancer
EGF–ERBB signalling: towards the systems level
Nat. Rev. Mol. Cell Biol
Escape from HER-family tyrosine kinase inhibitor therapy by the kinase-inactive HER3
Nature
Cited by (18)
HER3 in cancer: from the bench to the bedside
2022, Journal of Experimental and Clinical Cancer ResearchThirty years of HER3: From basic biology to therapeutic interventions
2021, Clinical Cancer ResearchConstruction of an integrated research system for precision treatment of gastrointestinal tumors
2021, Chinese Journal of Clinical Oncology
- 1
These authors contributed equally to this work.