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Paris saponin VII, a Hippo pathway activator, induces autophagy and exhibits therapeutic potential against human breast cancer cells

Yu-chen Xiang1,2, Peng Peng1,3, Xue-wen Liu1,4, Xin Jin1,2, Jie Shen1,2, Te Zhang2,4, Liang Zhang1,3, Fang Wan1,2, Yu-liang Ren1,2, Qing-qing Yu3,4, Hu-zi Zhao1,3,4, Yuan Si1,3,4, Ying Liu1,2,3,4
1 Laboratory of Molecular Target Therapy of Cancer, Institute of Basic Medical Sciences, Hubei University of Medicine, Shiyan 442000, China
2 Hubei Key Laboratory of Wudang Local Chinese Medicine Research, Hubei University of Medicine, Shiyan 442000, China
3 Hubei Key Laboratory of Embryonic Stem Cell Research, Hubei University of Medicine, Shiyan 442000, China
4 Laboratory of Molecular Target Therapy of Cancer, Biomedical Research Institute, Hubei University of Medicine, Shiyan 442000, China
Correspondence to: Yuan Si: siyuan138@126.com, Ying Liu: ying_liu1002@163.com,
DOI: 10.1038/s41401-021-00755-9
Received: 22 April 2021
Accepted: 2 August 2021
Advance online: 14 September 2021

Abstract

Dysregulation of the Hippo signaling pathway seen in many types of cancer is usually associated with a poor prognosis. Paris saponin VII (PSVII) is a steroid saponin isolated from traditional Chinese herbs with therapeutic action against various human cancers. In this study we investigated the effects of PSVII on human breast cancer (BC) cells and its anticancer mechanisms. We showed that PSVII concentration-dependently inhibited the proliferation of MDA-MB-231, MDA-MB-436 and MCF-7 BC cell lines with IC50 values of 3.16, 3.45, and 2.86 μM, respectively, and suppressed their colony formation. PSVII (1.2–1.8 μM) induced caspase- dependent apoptosis in the BC cell lines. PSVII treatment also induced autophagy and promoted autophagic flux in the BC cell lines. PSVII treatment decreased the expression and nuclear translocation of Yes-associated protein (YAP), a downstream transcriptional effector in the Hippo signaling pathway; overexpression of YAP markedly attenuated PSVII-induced autophagy. PSVII-induced, YAP- mediated autophagy was associated with increased active form of LATS1, an upstream effector of YAP. The activation of LATS1 was involved the participation of multiple proteins (including MST2, MOB1, and LATS1 itself) in an MST2-dependent sequential activation cascade. We further revealed that PSVII promoted the binding of LATS1 with MST2 and MOB1, and activated LATS1 in the BC cell lines. Molecular docking showed that PSVII directly bound to the MST2-MOB1-LATS1 ternary complex. Microscale thermophoresis analysis and drug affinity responsive targeting stability assay confirmed the high affinity between PSVII and the MST2-MOB1-LATS1 ternary complex. In mice bearing MDA-MB-231 cell xenograft, administration of PSVII (1.5 mg/kg, ip, 4 times/ week, for 4 weeks) significantly suppressed the tumor growth with increased pLATS1, LC3-II and Beclin 1 levels and decreased YAP, p62 and Ki67 levels in the tumor tissue. Overall, this study demonstrates that PSVII is a novel and direct Hippo activator that has great potential in the treatment of BC.
Keywords: anti cancer drug pharmacology; autophagy; Chinese traditional medicine; molecular docking; Breast cancer; Hippo pathway activator

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