Picropodophyllotoxin: A Natural Epimer Targeting STAT3 Phosphorylation and ROS-Mediated Apoptosis in Oral Squamous Cell Carcinoma Cells

Background: Picropodophllotoxin (PPT), a principal component of Podophyllum hexandrum root, demonstrates various beneficial biological activities in multiple cancer types, including antitumor and antiproliferative properties. Despite its known effects, the specific mechanisms by which PPT induces apoptosis in oral squamous cell carcinoma (OSCC) cells lack full clarification. Aims: This study aimed to evaluate the role of PPT in inducing apoptosis in OSCC cells by targeting signal transducer and activator of transcription 3 (STAT3) and to investigate the underlying molecular pathways. Methods: Human OSCC cell lines (HN22 and HSC4) were treated with PPT. Cell viability, colony formation, and apoptotic morphological changes were evaluated. Reactive oxygen species (ROS) generation and mitochondrial function were assessed using tetramethyl rhodamine methyl ester, MitoSOX, and 2^′, 7^′-dichlorodihydrofluorescein diacetate (DCFH-DA) assays following PPT treatment. The expression of apoptosis markers, including cleaved Poly (ADP-Ribose) Polymerase (c-PARP) and other target proteins, was measured using western blotting. ROS involvement was further confirmed using the ROS scavenger N-acetylcysteine (NAC). Results: Treatment with PPT resulted in a substantial reduction in cell viability, a decrease in colony formation capacity, and evident morphological changes in OSCC cells. These effects were dose- and time-dependent, as evidenced by increased expression of c-PARP. PPT-induced apoptosis was mediated by excessive ROS generation, which was almost completely blocked by NAC pretreatment. Conclusions: These findings suggest that PPT may serve as a promising therapeutic agent for treating human oral cancer by inhibiting the STAT3 pathway and inducing ROS-mediated apoptosis.