Isobacachalcone induces autophagy and improves the outcome of immunogenic chemotherapy

Qi Wu,Nitharsshini Nirmalathasan,Sylvère Durand,Yi Tu,Hui Pan,Wei Xie,Didac Carmona-Gutierrez,Frank Madeo,Liwei Zhao,Peng Liu,Ai-Ling Tian,Fanny Aprahamian,Shuai Zhang,Guido Kroemer,Oliver Kepp

doi:10.1038/s41419-020-03226-x

Abstract

A number of natural plant products have a long-standing history in both traditional and modern medical applications. Some secondary metabolites induce autophagy and mediate autophagy-dependent healthspan- and lifespan-extending effects in suitable mouse models. Here, we identified isobacachalcone (ISO) as a non-toxic inducer of autophagic flux that acts on human and mouse cells in vitro, as well as mouse organs in vivo. Mechanistically, ISO inhibits AKT as well as, downstream of AKT, the mechanistic target of rapamycin complex 1 (mTORC1), coupled to the activation of the pro-autophagic transcription factors EB (TFEB) and E3 (TFE3). Cells equipped with a constitutively active AKT mutant failed to activate autophagy. ISO also stimulated the AKT-repressible activation of all three arms of the unfolded stress response (UPR), including the PERK-dependent phosphorylation of eukaryotic initiation factor 2α (eIF2α). Knockout of TFEB and/or TFE3 blunted the UPR, while knockout of PERK or replacement of eIF2α by a non-phosphorylable mutant reduced TFEB/TFE3 activation and autophagy induced by ISO. This points to crosstalk between the UPR and autophagy. Of note, the administration of ISO to mice improved the efficacy of immunogenic anticancer chemotherapy. This effect relied on an improved T lymphocyte-dependent anticancer immune response and was lost upon constitutive AKT activation in, or deletion of the essential autophagy gene Atg5 from, the malignant cells. In conclusion, ISO is a bioavailable autophagy inducer that warrants further preclinical characterization.

Highlights

Macroautophagy is a unique cell biology phenomenon that leads to cytoplasmic vacuolization in response to nutrient deprivation as well as to a myriad of other cell stress-inducing conditions[1]
ISO induced the lipidation of LC3, measurable by immunoblot analyses that was even observed in the presence of bafilomycin A1, an inhibitor of autophagosome-lysosome fusion, suggesting that ISO induces autophagic flux (Fig. 1F, G)
Here, we identified ISO as an autophagy inducer that inhibits AKT and mechanistic target of rapamycin complex 1 (mTORC1) activity and activates the proautophagic transcription factors transcription factors EB (TFEB) and TFE3, which both are known to be activated by mTORC1 inhibition[27,28]

Summary

Introduction

Macroautophagy (to which we refer as “autophagy”) is a unique cell biology phenomenon that leads to cytoplasmic vacuolization in response to nutrient deprivation as well as to a myriad of other cell stress-inducing conditions[1]. Chalcones belong to the chemical class of flavonoids and are contained in multiple plants that are reputed for their dietary virtues Based on these considerations, we have set out in the past to identify autophagy-inducing chalcones. While 4,4′DMC inhibits autophagy-suppressive GATA transcription factors12,14, 3,4-DMC acts through the activation of the two related pro-autophagic transcription factors EB (TFEB) and E3 (TFE3)[13]. Irrespective of this difference, both 4,4′ DMC and 3,4-DMC reduce myocardial infarction in mice. 4,4′DMC extended the lifespan of yeast, nematodes, and flies[12], while 3,4-DMC enhanced anticancer immune responses in mice[13] These preclinical data plead in favor of a potential medial utility for chalcones

Methods

Results

Conclusion