PURPOSE

53 mutations are highly prevalent in head and neck squamous cell carcinoma (HNSCC) and associated with increased resistance to conventional treatment primarily consisting of chemotherapy and radiation. Restoration of wild-type p53 function in 53-mutant cancer cells represents an attractive therapeutic approach and has been explored in recent years. In this study, the efficacy of a putative p53 reactivator called COTI-2 was evaluated in HNSCC cell lines with different 53 status. Clonogenic survival assays and an orthotopic mouse model of oral cancer were used to examine and sensitivity of HNSCC cell lines with either wild-type, null, or mutant 53 to COTI-2 alone, and in combination with cisplatin and/or radiation. Western blotting, cell cycle, live-cell imaging, RNA sequencing, reverse-phase protein array, chromatin immunoprecipitation, and apoptosis analyses were performed to dissect molecular mechanisms.

RESULTS

COTI-2 decreased clonogenic survival of HNSCC cells and potentiated response to cisplatin and/or radiation and irrespective of 53 status. Mechanistically, COTI-2 normalized wild-type p53 target gene expression and restored DNA-binding properties to the p53-mutant protein in HNSCC. In addition, COTI-2 induced DNA damage and replication stress responses leading to apoptosis and/or senescence. Furthermore, COTI-2 lead to activation of AMPK and inhibition of the mTOR pathways in HNSCC cells.

CONCLUSIONS

COTI-2 inhibits tumor growth and in HNSCC likely through p53-dependent and p53-independent mechanisms. Combination of COTI-2 with cisplatin or radiation may be highly relevant in treating patients with HNSCC harboring 53 mutations.