Abstract
Autophagy is a conserved self-degradation system closely related to cancer progression. Small molecule inhibitors of autophagy have proven to be efficient tools in cancer therapy and are in high demand. Here we report the discovery of two compounds (LZ02/01) capable of suppressing cancer cell proliferation via inhibiting autophagy flux and promoting apoptosis. Potential autophagy inhibitors were selected based on the pharmacophore model derived from the structures of known autophagy inhibitors. LZ02/01-mediated autophagy flux disruption and apoptosis promotion in breast and hepatocellular carcinoma cells (MCF-7 and Hep3B) were examined using a combination of molecular methods in vitro and in vivo. The synergistic tumor-suppressing effects of LZ02 and chloroquine were validated by adopting a xenograft mice model of human breast cancer. Two potential inhibitors (LZ02/01) targeting an autophagy pathway were discovered from the Enamine database. In both MCF-7 and Hep3B cells, LZ02 and LZ01 had the effect of causing the co-occurrence of autophagic flux inhibition and apoptosis induction, robustly suppressing the growth, proliferation, and cell cycle progression. Further tests revealed that FoxO3a and its downstream target genes regulating autophagy, apoptosis, and cell cycle progression were activated and overexpressed, suggesting such effects of LZ02/01 on autophagy and apoptosis were associated with the activation and overexpression of FoxO3a. In addition, LZ02/01-mediated apoptosis is not independent; it was verified to be promoted by autophagic flux inhibition. Meanwhile, synergistic effects on tumor growth reduction were detected in the xenograft mice model of human breast cancer simultaneously treated with LZ02 and chloroquine. Our findings suggest that LZ01 and LZ02 are potent in suppressing cancer cell proliferation and tumor growth through autophagic flux inhibition and apoptosis promotion. The synergistic anti-cancer effects of LZ02 with chloroquine may provide a rational basis for prospective cancer therapy.
Key messages
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A ligand-based pharmacophore model of high quality is constructed to query hits and two novel scaffold lead compounds LZ01/02 were identified by high-throughput virtual screening.
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LZ01/02 works to inhibit autophagic flux by attenuating lysosome function.
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LZ01/02 induces apoptosis through autophagic flux inhibition and apoptosis is the main mechanism to inhibit MCF-7 and Hep3B cancer cell proliferation.
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The synergistic antitumor growth effects of LZ02 and chloroquine are verified in human xenograft model.
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Data availability
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
Abbreviations
- Atg7:
-
Autophagy-related gene 7
- Bcl-2:
-
B cell lymphoma 2
- Bax:
-
Bcl2-associated X protein
- Bim:
-
Bcl2 interacting mediator of cell death
- CQ:
-
chloroquine
- CTSB:
-
Cathepsin B
- CTSD:
-
Cathepsin D
- LC3:
-
light chain 3
- ULK1:
-
Unc-51-like kinase 1
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Acknowledgments
We are grateful to Prof. J.R. Schrock (Emporia State University, USA) for revising the manuscript. We thank Professor Wenxing Ding from University of Kansas Medical Center for his constructive opinions in writing and optimizing the manuscript.
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Li Liu and Zhen Tian contributed equally to this work; Jiyuan Liu, Hai Zhang, and Zhinan Chen conceived the project and designed the experiment; Jiyuan Liu and Yalin Zhang discovered the chemical structures of LZ01 and LZ02 through ligand-based high throughout virtual screening; Jiyuan Liu and Yalin Zhang synthesized LZ01 and LZ02; Jiyuan Liu and Hai Zhang performed the phenotypic screening of LZ01 and LZ 02 on cancer cells and discovered the inhibitory effects of LZ01 and LZ02 on MCF-7 and Hep3B cells; Li Liu, Zhen Tian, and Yifan Li performed the in vitro tests of LZ01 and LZ02 on MCF-7 and Hep3B cells; Peijuan Liu, Zhiqian Xin, Yong Zhao, and Shan Miao carried out the animal experiments; Hai Zhang and Jiyuan Liu prepared the manuscript; Hai Zhang, Jiyuan Liu, and Zhinan Chen supervised the study and contributed reagents/materials; All authors contributed to data analysis.
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Liu, L., Tian, Z., Zhang, Y. et al. Ligand-based discovery of small molecules suppressing cancer cell proliferation via autophagic flux inhibition. J Mol Med 98, 1573–1589 (2020). https://doi.org/10.1007/s00109-020-01971-2
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DOI: https://doi.org/10.1007/s00109-020-01971-2