Identification of a novel EphB4 inhibitor, Sanguinarine, which attenuates β-catenin signaling to inhibit tumor proliferation and migration in lung cancer.

[INTRODUCTION] EphB4, a receptor tyrosine kinase, is a known promoter of tumor growth and a promising therapeutic target for cancer therapies. However, its contribution to the development and treatment of lung cancer (LC) is not clearly understood.

[OBJECTIVES] The study aims to determine the role of EphB4 in the development of LC and assess the anticancer effect of sanguinarine (Sang), a natural compound, in the targeting of EphB4 in vitro and in vivo.

[METHODS] The expression of EphB4 in LC cell lines and patient samples was studied. Sang was evaluated on the effect of LC cell proliferation, migration, invasion, and molecular interaction, which was evaluated by binding affinity studies and pathway analysis.

[RESULTS] EphB4 expression was found to be greatly increased in LC patient samples and cell lines, which is associated with the elevation of cell proliferation and invasion. Sang revealed a high binding affinity to EphB4 and blocked the proliferation of LC cells, inhibiting the migration and invasion by half in EphB4-dependent assays. Mechanistically, Sang directly binds to EphB4, inhibiting its phosphorylation and disrupting its interaction with β-catenin. This leads to increased β-catenin phosphorylation, ubiquitination, and proteasomal degradation, ultimately suppressing EMT and tumor progression. Sang disrupted IGF-II-mediated stabilization of EphB4, leading to its polyubiquitination and proteasomal degradation. Sang in vivo inhibits tumor volume and inhibits tumor mass in LC xenograft models with no appreciable toxicity.

[CONCLUSIONS] The results of the study indicate that EphB4 plays a significant role in the progression of LC and show that Sang can act on EphB4 via a previously unknown pathway with the involvement of IGF-II inhibition and proteasomal degradation. These findings indicate the promise of Sang as a clinical candidate in the treatment of LC and the need to advance the drug in clinical trials.