Targeting ubiquitin conjugating enzyme UbcH5b by a triterpenoid PC3-15 from Schisandra plants sensitizes triple-negative breast cancer cells to lapatinib.

Cancer Lett

Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Kunming, Yunnan, China; KIZ-CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, 650223, China. Electronic address:

Published: April 2021

Increasing evidence suggested that a number of ubiquitin enzymes, including ubiquitin-activating enzymes, ubiquitin-conjugating enzymes, E3 ubiquitin ligases and deubiquitination enzymes contribute to therapeutic resistance in triple-negative breast cancer (TNBC) cells. Inhibition of these enzymes with small molecule inhibitors may restore therapeutic sensitivity. Here, we demonstrated ubiquitin conjugating enzyme UbcH5b strongly supports HECTD3 auto-ubiquitination in vitro. Based on this, we developed a Fluorescence Resonance Energy Transfer (FRET) assay and identified three Schisandraceae triterpenoids, including PC3-15, to block HECTD3/UbcH5b auto-ubiquitination. Furthermore, we revealed that PC3-15 directly binds to UbcH5b and also inhibits UbcH5b-mediated p62 ubiquitination. We found that the UbcH5b-p62 axis confers TNBC cells resistance to lapatinib by promoting autophagy. Consistently, PC3-15 inhibits lapatinib-induced autophagy and increases lapatinib sensitivity in TNBC in vitro and in mouse xenografts. These findings suggest that the UbcH5b-p62 axis provides potential therapeutic targets and that Schisandraceae triterpenoids may be used for TNBC treatment in combination with lapatinib.

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Source
http://dx.doi.org/10.1016/j.canlet.2021.02.009DOI Listing

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