Ascorbic acid induces ferroptosis via STAT3/GPX4 signaling in oropharyngeal cancer

Ferroptosis is recognized as a new type of regulated cell death initiated by iron-dependent accumulation of lipid peroxidation. Recent studies have shown that the administration of ascorbic acid (AA) preferentially kills tumor cells by impairing iron metabolism and exerting pro-oxidant effects. Despite mounting evidence indicating the anticancer potential of AA, the underlying molecular mechanisms remain unknown. In this study, we demonstrated that AA decreased cell viability and Ki67 expression, along with its accumulation in the G(0)/G(1) phase in FaDu and SCC-154 cell lines. Furthermore, AA exposure induced morphological changes in mitochondria associated with ferroptosis. AA-induced ferroptosis is accompanied by depletion of glutathione (GSH) and increased levels of ferrous ions (Fe2+), reactive oxygen species (ROS), and malondialdehyde (MDA). However, these ferroptotic effects were ameliorated by deferoxamine and N-acetylcysteine. Network pharmacology results showed that signal transducer and activator of transcription 3 (STAT3) is a key target of AA against oropharyngeal cancer. AA markedly downregulates the relative mRNA expression of STAT3 and glutathione peroxidase 4 (GPX4). Immunoblotting indicated that the protein levels of p-STAT3, STAT3, and GPX4 in FaDu and SCC-154 cells decreased significantly in response to AA treatment. Mechanistically, a chromatin immunoprecipitation assay confirmed that AA exposure reduced STAT3 expression in the GPX4 promoter region. Additionally, AA-induced inhibition of cell growth and ferroptosis was suppressed by STAT3 and GPX4 overexpression, respectively. In summary, AA inhibited oropharyngeal cancer cell growth in vitro by regulating STAT3/GPX4-mediated ferroptosis, which may provide a novel theoretical basis for the clinical treatment of oropharyngeal cancer with AA.