Repurposing Suan-Zao-Ren-Tang as anticancer agents in apoptotic sensitization against non-small cell lung cancer cell lines through amplification of spindle assembly checkpoint activation

Treatment of non-small cell lung cancer (NSCLC) is a high unmet medical need. We repurposed Suan-Zao-Ren-Tang (SZRT), a widely used traditional Chinese medicine in alleviating insomnia, to sensitize vinorelbine-induced anti-NSCLC effect and have unveiled the underlying mechanism. B7E2, the partial purified extract from SZRT, was used through bioactivity-guided fractionation based on anti-proliferative activity in NSCLC cell lines A549 and NCI-H460. Three batches of B7E2 and their individual components were prepared for the examination of components and bioactivity and mechanistic study. B7E2 alone had no cytotoxic effect but its combination with vinorelbine displayed a synergistic activity in killing NSCLC cells. Apoptotic sensitization was verified by a remarkable increase of caspase activation and phosphorylation of Bcl-2 and Bcl-xL. Combination treatment prolonged mitotic arrest and induced a substantial activation of spindle assembly checkpoint (SAC) characterized by BUBR1 phosphorylation at Ser670 and Thr680, and cyclin B1 upregulation. Combination treatment enhanced the interaction between mitotic checkpoint complex (MCC) components, including BUBR1, MAD2, BUB3 and CDC20. Further analysis revealed that SZRT components, including senkyunolide-A, trans-neocnidilide, 3-butylidenephthalide, betulinic acid and linoleic acid, were responsible for B7E2 activities. Three B7E2 batches showed a good chemical similarity and similar activities between batches. The data suggest that B7E2 is a potential chemosensitizer in potentiating vinorelbine-induced anti-NSCLC activity through amplification and prolongation of SAC activation.