Nigrosporins B, a Potential Anti-Cervical Cancer Agent, Induces Apoptosis and Protective Autophagy in Human Cervical Cancer Ca Ski Cells Mediated by PI3K/AKT/mTOR Signaling Pathway

Nigrosporins B, an anthraquinone derivative obtained from the secondary metabolites of marine fungus Nigrospora oryzae. In this study, we characterized the distinctive anti-cancer potential of Nigrosporins B in vitro and underlying molecular mechanisms in human cervical Cancer Ca Ski cells for the first time. The results of MTT assay showed that Nigrosporins B significantly inhibited the proliferation of multiple tumor cells in a dose-dependent manner, especially for the CA Ski cells with an IC₅₀ of 1.24 µM. Nigrosporins B exerted an Apoptosis induction effect on CA Ski cells as confirmed by flow cytometry, AO/EB dual fluorescence staining, mitochondrial membrane potential analysis and western blot assay. In addition, Nigrosporins B induced obvious Autophagy accompanied with the increase of autophagic vacuoles and the acceleration of autophagic flux as indicated by Cyto-ID staining, mRFP-GFP-LC3 adenovirus transfection and western blot analysis. Interestingly, the combination of Nigrosporins B with the three Autophagy inhibitors all significantly enhanced the cytotoxicity of Nigrosporins B on CA Ski cells, indicating that the Autophagy induced by Nigrosporins B might protect CA Ski cells from death. Furthermore, we found that Nigrosporins B inhibited the phosphorylation of PI3K, Akt, mTOR molecules and increased the protein expression levels of PTEN and p-AMPKα in a dose-dependent manner, suggesting that Nigrosporins B induced Apoptosis and protective Autophagy through the suppression of the PI3K/Akt/mTOR signaling pathway. Together, these findings revealed the anti-cervical Cancer effect of Nigrosporins B and the underlying mechanism of action in CA Ski cells, it might be as a promising alternative therapeutic agent for human cervical Cancer.