Molecular Mechanisms of Chemoresistance in Oral Squamous Cell Carcinoma: A Narrative Review with Present and Future Perspectives

Oral squamous cell carcinoma (OSCC) remains a highly prevalent and aggressive malignancy with limited improvements in survival rates. One of the major obstacles to successful treatment is the development of chemoresistance, which contributes to recurrence, metastasis, and treatment failure. This narrative review aims to integrate current evidence on the molecular and cellular mechanisms that drive chemoresistance in OSCC and to delineate how these processes converge under therapeutic pressure. A structured search was performed to identify relevant studies addressing chemoresistance in OSCC, focusing on preclinical and translational evidence. Multiple interconnected mechanisms have been implicated in driving resistance in OSCC, including epigenetic alterations, deregulated signaling pathways, cancer stem cell plasticity, epithelial–mesenchymal transition (EMT), interactions with the tumor microenvironment (TME), drug efflux mediated by ATP-binding cassette (ABC) transporters, and enhanced DNA damage response. In combination, these mechanisms support tumor persistence and limit effective antitumor immunity. Emerging strategies such as epigenetic modulators, signaling pathway inhibitors, immunomodulation, and nanomedicine-based delivery systems have shown promising results in preclinical models. By highlighting convergent resistance networks, this integrative perspective supports the rational design of combination therapies and biomarker-guided strategies aimed at overcoming chemoresistance in OSCC.