Triggering mitotic catastrophe by podophyllotoxin induces apoptosis in oral squamous cell carcinoma

Objective

This study investigated the relationship between mitotic catastrophe (MC) and apoptosis in oral squamous cell carcinoma (OSCC) using podophyllotoxin (PPT), a natural compound with antimitotic properties.

Design

We evaluated the concentration-dependent effects of PPT on cell proliferation (CCK-8 and soft agar assays) and morphology (transmission electron microscopy). Mechanistic insights were obtained by assessing DNA damage (western blotting), cell cycle progression (sub-G₁ analysis), and apoptosis-related protein activation in both 2D and 3D spheroid models of HSC-3 oral squamous carcinoma cells.

Results

PPT exerted pronounced inhibitory effects on cell proliferation and anchorage-independent growth accompanied by morphological indications of MC, such as enlarged multinucleated cells. DNA damage induced by PPT resulted in ataxia telangiectasia mutated kinase and checkpoint kinase 2 activation, leading to G₂/M arrest and cyclin B1upregulation. Importantly, PPT-induced MC was followed by apoptosis, as evidenced by an increased sub-G₁ population, Annexin V positivity, and caspase activation. Mitochondrial dysfunction, as indicated by altered membrane potential and enhanced Bax expression, underscored the apoptotic process. Caspase-2 activation emerged as a pivotal event, cleaving Bid and establishing a link between MC and the intrinsic apoptotic pathway. The effects were consistent across both 2D and 3D models, suggesting a robust therapeutic potential.

Conclusions

This study provides compelling evidence supporting the potential therapeutic significance of inducing MC-mediated apoptosis in OSCC. The results underscore the role of PPT and its derivatives, such as etoposide and teniposide, in targeting rapidly dividing cancer cells through interference with mitotic progression, offering insights into novel therapeutic strategies for oral cancer.