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The anti-HER2 monoclonal antibody trastuzumab is a key drug for the treatment of HER2-positive gastric cancer (GC); however, its activity is often limited by the onset of resistance and mechanisms of resistance are still poorly understood. Several targeted agents showed synergistic activity by concomitant use with trastuzumab in vitro and are under clinical investigation. The aim of this study was to assess the antitumor activity of duligotuzumab, an anti HER3/EGFR antibody or ipatasertib, an AKT inhibitor, combined with trastuzumab in a panel of HER2-positive human gastric cancer cells (GCC), and the efficacy of such combinations in HER2-resistant cells. We have assessed the efficacy of duligotuzumab or ipatasertib and trastuzumab in combination, analyzing proliferation, migration and apoptosis and downstream intracellular signaling in vitro on human HER2-positive GCC (NCI-N87, OE33, OE19) and in negative HER2 GCC (MKN28). We observed a reduction of proliferation, migration and apoptotic rate in HER2-positive OE33, OE19 and N87 cell lines with the combination of duligotuzumab or ipatasertib plus trastuzumab. In particular, in OE33 and OE19 cell lines, the same combined treatment inhibited the activation of proteins downstream of HER2, HER3, AKT and MAPK pathways. Targeting both HER2 and HER3, or HER2 and AKT, results in an improved antitumor effect on HER2-positive GCC.

Gastric cancer (GC) is the fifth-most common cancer worldwide and an important cause of cancer-related-death. The growing knowledge of its molecular pathogenesis has shown that GC is not a single entity, but a constellation of different diseases, each with its own molecular and clinical characteristics. Currently, surgery represents the only curative approach for localized GC, but only 20% of patients (pts) showed resectable disease at diagnosis and, even in case of curative resection, the prognosis remains poor due to the high rate of disease relapse. In this context, multimodal perioperative approaches were developed in western and eastern countries in order to decrease relapse rates and improve survival. However, there is little consensus about the optimal treatment for non-metastatic GC. In this review, we summarize the current status and future developments of perioperative chemotherapy in resectable GC, attempting to find clear answers to the real problems in clinical practice., Competing Interests: Angelica Petrillo: grant from Lilly; Michele Orditura: Honoraria from Italfarmaco, EISAI, epionpharma, Roche; Fortunato Ciardiello: Advisory Boards: Roche, Amgen, Merck, Pfizer, Sanofi, Bayer, Servier, BMS, Celgene, Lilly; Institutional Research Grants: Bayer, Roche, Merck, Amgen, AstraZeneca, Takeda; Ferdinando De Vita: Advisory Boards: Roche, Amgen, Celgene, Lilly. The authors have no conflicts of interest to declare. The funders had no role in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.