Crocin and eugenol enhance radiosensitivity in oral squamous cell carcinoma cells via apoptotic pathways and cell cycle regulation. Type of study: in vitro

BACKGROUND: Oral squamous cell carcinoma (OSCC) continues to be a significant clinical challenge because of radioresistance and treatment-related toxicities. Safer radiosensitizers are urgently needed. OBJECTIVE: This study assessed the radiosensitizing effects of crocin and eugenol on OSCC-1 cells in vitro. METHODS: OSCC-1 cells were treated with crocin, eugenol, ionizing radiation, or their combinations. Cell viability (MTT assay), apoptosis (Annexin V/PI), and cell cycle distribution (PI staining) were assessed, along with transcriptional expression of Bax, Bcl-2, Caspase-3, Cyclin A, and Cyclin B measured by RT-qPCR. The effects of the combinations were analyzed using the Chou-Talalay method. RESULTS: Both crocin and eugenol independently decreased OSCC cell viability and triggered apoptosis in a dose-dependent way. When used with IR, they worked together to boost cytotoxicity at moderate doses (CI < 1). Crocin caused early G1 arrest followed by G2/M accumulation, while eugenol strongly induced G2/M arrest and increased sub-G1 fractions. Molecular analysis showed activation of the intrinsic apoptotic pathway (↑Bax, ↑Caspase-3, ↓Bcl-2) and reduced levels of Cyclin A/B transcripts. CONCLUSION: Crocin and eugenol effectively sensitize OSCC cells to IR by regulating apoptotic factors and promoting checkpoint arrest. Their favorable safety profiles and ability to enhance radiosensitivity support further in vivo studies and translational development as natural adjuncts in radiotherapy.