COTI-2, a novel thiosemicarbazone derivative, exhibits antitumor activity in HNSCC through p53-dependent and -independent mechanisms

Purpose: TP53 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 wildtype p53 function in TP53 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 TP53 status. Experimental Design: Clonogenic survival assays and an orthotopic mouse model of oral cancer were used to examine in vitro and in vivo sensitivity of HNSCC cell lines with either wildtype, null or mutant TP53 to COTI-2 alone, and in combination with cisplatin and/or radiation. Western blotting, cell cycle, live cell imaging, RNA sequencing, RPPA, chromatin immunoprecipitation (ChIP) 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 in vitro and in vivo irrespective of TP53 status. Mechanistically, COTI-2 normalized wildtype p53 target gene expression and restored DNA binding properties to the p53 mutant protein in HNSCC. Additionally, 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 vitro in HNSCC cells. Conclusions: COTI-2 inhibits tumor growth in vitro and in vivo 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 TP53 mutations.