Quercetin induces p53‐independent cancer cell death through lysosome activation by the transcription factor EB and Reactive Oxygen Species‐dependent ferroptosis

Abstract

Background and Purpose Cancer cells exhibit more dependence on iron and enhanced sensitivity to iron‐dependent, programmed cell death (ferroptosis) than normal cells. Quercetin exerts anti‐cancer effects, but the underlying molecular mechanism is largely unknown. In this study, we aimed to investigate the involvement of lysosome function and ferroptosis in the anti‐cancer potential of quercetin. Experimental Approach We used MTT assays and DNA content analysis to evaluate the cytotoxicity, colony formation assay to investigate cell proliferation, and flow cytometry and confocal microscopy to detect lysosomal acidification and protease enzyme activity. Western blotting, cell subfractionation, RT‐PCR and siRNA transfection were used to establish molecular mechanisms of action. Key Results Quercetin is known to promote p53‐independent cell death in various cancer cell lines. Although quercetin induces autophagy, genetic silencing of Atg7 fails to affect quercetin‐induced cell death. In contrast, both lysosome inhibitors and knockdown of the transcription factor EB can prevent quercetin‐induced cell death, suggesting the involvement of lysosome. Next, quercetin is found to induce lysosomal activation sequentially through nuclear translocation of EB and transcriptional activation of lysosomal genes. Notably, quercetin promoted lysosome‐dependent ferritin degradation and free iron release. This action and quercetin‐induced ROS generation synergistically resulted in lipid peroxidation and ferroptosis. Furthermore, Bid may link ferroptosis with apoptosis to cause cell death. Conclusion and Implications Quercetin induced EB‐mediated lysosome activation and increased ferritin degradation leading to ferroptosis and Bid‐involved apoptosis. Results from this study may expand our current knowledge about the mechanism of quercetin as an anti‐cancer agent.

Evaluating causality of cellular senescence in non-alcoholic fatty liver disease

“…Moreover, senolytics also have other effects. For example, the antioxidant quercetin inhibits ferroptosis and can decrease inflammation and lipid metabolism, all pathways that are associated with NAFLD [81,82]. Although it has been suggested that senolytics could be administrated intermittently, thereby reducing the risks of adverse events, large clinical trials are needed to define the benefits and potential risks of these drugs.…”

“…This multi-marker approach enables the detection of senescent cells in various experimental settings and tissues. Promising results have been achieved in the first clinical trials targeting cellular senescence in humans 80 , 81 Therefore, it is of critical importance to develop, implement, test, and harmonise methods and standard operating protocols for translational early phase trials of agents that target fundamental aging processes. New, effective and low-cost assays are needed to detect and trace senescence in blood, cells and biopsies of the targeted organ for use in clinical trials.…”

Autophagy‐Dependent Ferroptosis as a Therapeutic Target in Cancer

“…The activated lysosome degrades ferritin and then promotes ferroptosis through iron release and subsequent lipid oxidation. [90] Amentoflavone (AF) is a polyphenol which has been widely found in Selaginella. [91] It has attracted increasing interests because of its anti-tumor effects.…”

The molecular basis of the anticancer properties of quercetin

“…Ferroptosis is an iron-dependent non-canonical PCD mechanism, driven by the accumulation of lipid peroxides. In hepatocellular carcinoma HepG2 cells, quercetin (50 μM) promoted both apoptosis and ferroptosis [22]. Indeed, lysosome-dependent cell death induced by quercetin was associated with the promotion of ferritin degradation [22], a process known as ferritinophagy, which enhances the cellular free iron content, thus increasing lipid peroxidation and promoting ferroptotic cell death [23].…”

“…In hepatocellular carcinoma HepG2 cells, quercetin (50 μM) promoted both apoptosis and ferroptosis [22]. Indeed, lysosome-dependent cell death induced by quercetin was associated with the promotion of ferritin degradation [22], a process known as ferritinophagy, which enhances the cellular free iron content, thus increasing lipid peroxidation and promoting ferroptotic cell death [23]. Necroptosis, instead, relies on the activation of RIPK1 (receptor interacting serine/threonine kinase 1) that leads to the formation of the so-called necrosome complex.…”