Tubeimoside-1, a triterpenoid saponin, induces cytoprotective autophagy in human breast cancer cells in vitro via Akt-mediated pathway
Tubeimoside-1, a triterpenoid saponin, induces cytoprotective autophagy in human breast cancer cells in vitro via Akt-mediated pathway
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Tubeimoside-1 是一种三萜皂苷，在体外通过 Akt 介导的途径诱导人乳腺癌细胞的细胞保护性自噬。
DOI：
10.1038/s41401-018-0165-9
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发表时间：
2019-07-01
影响因子：
8.2
通讯作者：
Cheng, Yan
中科院分区：
文献类型：
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作者：
Jiang, Shi-long;Guan, Yi-di;Cheng, Yan
自噬是细胞通过溶酶体自我消化的一种形式，与包括癌症在内的各种疾病过程相关，并且调节自噬在治疗各种恶性肿瘤中显示出希望。许多天然产物显示出很强的抗肿瘤活性，但其作用机制尚不清楚。为了更好地了解中药制剂如何发挥抗肿瘤作用，我们使用检测HeLa细胞中GFP-LC 3斑点的高含量筛选试验筛选了480种天然化合物对自噬的影响。土贝母皂苷-1（Tubeimoside-1，TBMS 1）是从葫芦科植物土贝母（Bolbostemma paniculatum（Maxim）Franquet）中提取的一种三萜皂苷类化合物，被鉴定为一种有效的自噬激活剂。TBMS 1激活自噬的证据是增加的LC 3-II量和GFP-LC 3点，在电子显微镜下观察到自噬体，和增强的自噬通量。为了探索TBMS 1激活自噬的机制，我们进行了化学信息学分析和表面等离子体共振（SPR）结合试验，显示Akt蛋白和TBMS 1之间结合的可能性更高。在三种人乳腺癌细胞系中，我们证明Akt-mTOR-eEF-2K通路参与TBMS 1诱导的自噬激活，而Akt介导的Mcl-1、Bcl-xl和Bcl-2的下调导致乳腺癌细胞凋亡的激活。抑制自噬可通过促进细胞凋亡增强TBMS 1的细胞毒作用。我们的研究结果证明了TBMS 1在激活自噬中的作用和机制，表明抑制细胞保护性自噬可能作为一种治疗策略，以加强TBMS 1对癌症的活性。
Autophagy, a form of cellular self-digestion by lysosome, is associated with various disease processes including cancers, and modulating autophagy has shown promise in the treatment of various malignancies. A number of natural products display strong antitumor activity, yet their mechanisms of action remain unclear. To gain a better understanding of how traditional Chinese medicine agents exert antitumor effects, we screened 480 natural compounds for their effects on autophagy using a high content screening assay detecting GFP-LC3 puncta in HeLa cells. Tubeimoside-1 (TBMS1), a triterpenoid saponin extracted from Bolbostemma paniculatum (Maxim) Franquet (Cucurbitaceae), was identified as a potent activator of autophagy. The activation of autophagy by TBMS1 was evidenced by increased LC3-II amount and GFP-LC3 dots, observation of autophagosomes under electron microscopy, and enhanced autophagic flux. To explore the mechanisms underlying TBMS1-activated autophagy, we performed cheminformatic analyses and surface plasmon resonance (SPR) binding assay that showed a higher likelihood of the binding between Akt protein and TBMS1. In three human breast cancer cell lines, we demonstrated that Akt-mTOR-eEF-2K pathway was involved in TBMS1-induced activation of autophagy, while Akt-mediated downregulations of Mcl-1, Bcl-xl, and Bcl-2 led to the activation of apoptosis of the breast cancer cells. Inhibition of autophagy enhanced the cytotoxic effect of TBMS1 via promoting apoptosis. Our results demonstrate the role and mechanism of TBMS1 in activating autophagy, suggesting that inhibition of cytoprotective autophagy may act as a therapeutic strategy to reinforce the activity of TBMS1 against cancers.