Differential Effects of Apigenin on Normal and Squamous Oral Epithelial Cells Reveal Redox–Autophagy Signaling Vulnerabilities in OSCC

The aim of this study was to compare the responses of normal human gingival epithelial cells (HGEpiC) and oral squamous cell carcinoma cells (OECM-1) to apigenin, a natural flavonoid, focusing on redox balance, autophagy, and apoptosis. This study is among the first to directly compare apigenin-induced responses in normal and cancerous oral epithelial cells. Cells were exposed to apigenin for 24 or 48 h, with untreated cells as controls. Mitochondrial activity, ATP, ROS (H₂O₂), and GSH were measured. Proliferation and morphology were monitored using HoloMonitor^® M4. Autophagy was assessed by fluorescent vacuole labeling, and apoptosis-related proteins (p-AKT, p-BCL-2, p-p53, p-JNK, caspase-8/9) by Luminex assay. Late apoptosis was evaluated by caspase-3/7 activity. Apigenin elicited a differential response: in HGEpiC cells, it was non-cytotoxic and increased metabolic activity, induced a moderate ROS increase, and activated autophagy as a pro-survival mechanism; in contrast, OECM-1 cells exhibited a significant reduction in metabolic activity, a marked ATP decrease at 24 h, and a pronounced ROS increase. These alterations were associated with reduced autophagy and decreased p-JNK signaling. These findings indicate that apigenin exerted no harmful effects on HGEpiC cells, while inducing redox imbalance in OECM-1 cells, highlighting a context-dependent cellular response.