COTI-2, A Novel Thiosemicarbazone Derivative, Exhibits Antitumor Activity in HNSCC through p53-dependent and -independent Mechanisms.

Abstract

<i>TP</i>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 <i>TP</i>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 <i>TP</i>53 status.<b>Experimental Design:</b> Clonogenic survival assays and an orthotopic mouse model of oral cancer were used to examine <i>in vitro</i> and <i>in vivo</i> sensitivity of HNSCC cell lines with either wild-type, null, or mutant <i>TP</i>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. COTI-2 decreased clonogenic survival of HNSCC cells and potentiated response to cisplatin and/or radiation <i>in vitro</i> and <i>in vivo</i> irrespective of <i>TP</i>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 <i>in vitro</i> in HNSCC cells. COTI-2 inhibits tumor growth <i>in vitro</i> and <i>in vivo</i> 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 <i>TP</i>53 mutations.