Role of p38 MAPK in disease relapse and therapeutic resistance by maintenance of cancer stem cells in head and neck squamous cell carcinoma

Aim: This study aimed to investigate the role of p38 MAPK in maintenance of cancer stem cell (CSC) phenotype, therapy resistance, and DNA damage repair and response in head and neck squamous cell carcinoma (HNSCC). Methods: In this study, 104 HNSCC patients were included. Western blot, immunohistochemistry, and qPCR analysis were performed to investigate the expression level of p-p38 and CSC markers in cut margin and tumor area of HNSCC patients. The expression level of p-p38 and CSC markers was also evaluated in HNSCC cells with or without p38 inhibitor. Chemoresistance, wound healing capacity, and multicellular tumor spheroids (MCTS) formation capacity were evaluated in HNSCC-derived cell lines with or without p38 inhibitor. In addition, DNA damage response and repair capacities were also evaluated in HNSCC cells after p38 inhibition using alkaline comet assay and gamma-H(2)AX immunostaining. Result: We observed that recurrence could be associated with upregulated status of p-p38 and p38 alpha gene in cut margin area of HNSCC patients as compared to tumor region. p38-inhibited cells showed significantly reduced expression of CSC markers, chemosensitivity toward cisplatin, reduced migration potential, and sphere-forming ability along with increased apoptotic population after treatment with increasing concentration of cisplatin. p38-inhibited cells also exhibited significantly increased comet olive tail moment and accumulation of gamma-H(2)AX, demonstrating increased DNA damage. Conclusion: This study demonstrated that p38 MAPK activation may play a role in therapeutic resistance and disease relapse in HNSCC by maintenance of CSCs phenotype.