Cinobufagin exerts an antitumor effect in non-small-cell lung cancer by blocking STAT3 signaling.

Background: Non-small-cell lung cancer (NSCLC) is the most common histological subtype of lung cancer with significant morbidity and mortality rates worldwide. Cinobufagin, the primary component of Chansu and the major active ingredient of cinobufacini, has attracted widespread attention for its excellent anticancer effects, but its activity remains poorly characterized in NSCLC. Methods: The functions of cinobufagin treatment in anti-tumor was evaluated using various in vitro and in vivo assays. The change of STAT3 signaling by cinobufagin was analyzed using molecular docking, immunofluorescence technic and western blotting. Results: In vitro, we confirmed the inhibitory effect of cinobufagin on cell viability, proliferation, migration, epithelial-mesenchymal transition (EMT), as well as an apoptosis-inducing effect. The antitumor effects of cinobufagin were confirmed in vivo by measuring tumor growth in a mouse xenograft model. Cinobufagin was found to significantly inhibit the phosphorylation of signal transducer and activator of transcription 3 (STAT3) at tyrosine 705 (Y705) in a time- and concentration-dependent manner. Moreover, cinobufagin reversed IL-6-induced nuclear translocation of STAT3. Conclusions: Our study has demonstrated that cinobufagin exerts an antitumor effect in non-small-cell lung cancer by blocking STAT3 signaling, and cinobufagin is a promising candidate agent for NSCLC therapy.