A multi-kinase inhibitor APG-2449 enhances the antitumor effect of ibrutinib in esophageal squamous cell carcinoma via EGFR/FAK pathway inhibition

Esophageal squamous cell carcinoma (ESCC) is one of the most common types of cancer in China, with poor prognosis and lack of effective targeted therapy. It has been reported that ibrutinib possesses anticancer activity in ESCC with MYC and/or ERBB2 amplification. Here we explored the synergistic antitumor effect of a novel multi-kinase inhibitor APG-2449 with ibrutinib in ESCC and clarified the mechanism of the combination effect through in vitro and in vivo experiment. We found that APG-2449 exerted antitumor effect in ESCC. APG-2449 combined with ibrutinib showed synergistic inhibition of cell viability in ESCC cell lines. APG-2449 combined with ibrutinib dramatically inhibited the proliferation and migration of ESCC cells. Furthermore, we observed that ibrutinib combined with APG-2449 could induce more cancer cells arrested in the G1/S phase and apoptosis. In terms of mechanism, ibrutinib alone could decrease the phosphorylation level of EGFR and its downstream pathway of MEK/ERK. The combination therapy of APG-2449 and ibrutinib could significantly down-regulate the phosphorylation level of MEK/ERK and AKT. In ESCC xenotransplantation models, single therapy with either ibrutinib or APG-2449 was equivalent in delaying tumor growth, while the combination therapy suppressed tumor growth more significantly. Our data strongly suggest that the combination therapy of APG-2449 and ibrutinib can provide an effective therapeutic strategy for ESCC patients, which deserved further clinical investigation.