Silibinin Induces Both Apoptosis and Necroptosis with Potential Anti-tumor Efficacy in Lung Cancer.

Abstract

Background: Lung cancer incidence is steadily on the rise, posing a growing threat to human health. The search for therapeutic drugs from natural active substance and elucidating their mechanism have been the focus of anti-tumor research.

Objective: In our work, Silibinin (SiL) was chosen as a possible substance that could inhibit lung cancer. and its effects on inducing tumor cell death have been studied.

Methods: CCK-8 analysis and morphological observation were used to assess the cytotoxic impacts of SiL on lung cancer cells in vitro. The alterations in mitochondrial membrane potential (MMP) and apoptosis rate of cells were detected by flow cytometry. The level of lactate dehydrogenase (LDH) release out of cells was measured. The expression changes of apoptosis or necroptosis-related proteins were detected using western blotting. Protein interactions among RIPK1, RIPK3 and MLKL were analyzed using the co-immunoprecipitation technique. In vivo, SiL was evaluated for its antitumor effects using LLC tumor-bearing mice with mouse lung cancer.

Results: With an increased dose of SiL, the proliferation ability of A549 cells was considerably inhibited, and the accompanying cell morphology changed. The results of flow cytometry showed that after SiL treatment, MMP levels decreased, and the proportion of cells undergoing apoptosis increased. The proteins associated with apoptosis were upregulated and activated. The amount of LDH released from the cells increased following SiL treatment, accompanied by augmented expression and phosphorylation levels of necroptosis-related proteins. The co-IP assay further confirmed necrosome formation induced by SiL. Furthermore, Necrosulfonamide (an MLKL inhibitor) increased the apoptotic rate of SiL-treated cells and aggravated the cytotoxic effect of SiL, indicating that necroptosis blockade could switch cell death to apoptosis and increase the inhibitory effect of SiL on A549 cells. In LLC-bearing mice, gastric administration of SiL significantly inhibited tumor growth.

Conclusions: This study helped clarify the anti-tumor mechanism of SiL against lung cancer, elucidating its role in dual induction of apoptosis and necroptosis. In particular, necroptosis blockade could switch cell death to apoptosis and increase the inhibitory effect of SiL. Our work provided an experimental basis for the research on cell death induced by SiL and revealed its possible applications for improving the management of lung cancer.

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