Activation of SIRT3/AMPK/mTOR-mediated autophagy promotes quercetin-induced ferroptosis in oral squamous cell carcinoma.

Introduction: Quercetin has been reported to inhibit the growth of oral squamous cell carcinoma (OSCC), but the mechanism remains unclear. Therefore, our study aimed to investigate the involvement of sirtuin 3 (SIRT3) and the autophagy-dependent form of cell death, ferroptosis, in the pathogenesis of OSCC, and observe the impacts of quercetin on ferroptosis and SIRT3/AMPK/mTOR-mediated autophagy.

Methods: SIRT3 knock out or overexpressing SCC15 cell line was generated, treated with indicated drugs, and malondialdehyde (MDA) and ROS levels were measured. Roles of SIRT3 in regulating autophagy-mediated ferroptosis were assessed by immunoprecipitation and Western blotting.

Results: SIRT3 overexpression increased levels of MDA and ROS, reducing cell viability, and SIRT3 knockout produced the opposing effect. SIRT3 overexpression upregulated ATG16L1 expression and the conversion of LC3-Ⅰ to LC3-Ⅱ, triggering autophagy. Suppression of autophagy by ATG16L1 knockout impaired SIRT3-triggered ferroptosis. Use of an AMPK inhibitor antagonized the induction of ferroptosis by SIRT3 in SCC15 cells, indicating the involvement of the AMPK/mTOR pathway. Additionally, quercetin significantly increased the levels of SIRT3, p-AMPK, ATG16L1, and the ratio of LC3-Ⅱ/Ⅰ, but reduced cell viability and p-mTOR in SCC15 cells. Autophagy and AMPK inhibitors, or SIRT3 deletion significantly antagonized the impacts of quercetin on the autophagy-mediated ferroptosis in cancer cells.

Discussion: SIRT3 overexpression activated the AMPK/mTOR pathway and triggered ATG16L1-mediated autophagy, promoting ferroptosis in SCC15 cells, and we proposed that quercetin may be a promising therapeutic drug for OSCC.