APR-246 & COTI-2 increase chemoradiotherapy sensitivity via ROS-induced DNA damage and ferroptosis in p53 mutant HPV negative head and neck squamous cell carcinoma

About 80% of patients with HPV negative head and neck squamous cell carcinoma are diagnosed at stage III or IV. In these cases, Surgical resection followed by (chemo-)radiotherapy is the standard treatment for most cases. However, many patients present with unresectable and/or resistant disease and even metastases, limiting therapeutic options. A common molecular defect in these tumours is the deactivation of the tumour suppressor gene TP53, frequently through inactivating mutations. Restoring TP53 function, combined with the standard chemoradiotherapy may enhance the therapeutic outcomes. In this study, the efficacy of two TP53 reactivating compound, APR-246 and COTI-2, was evaluated in combination with chemoradiotherapy on two different human HNSCC cell lines. Results highlight a synergistic effect of the combination treatment, significantly reducing clonogenic survival, spheroid growth and subcutaneous tumour growth in a preclinical murine model. Mechanistic investigation suggests that this effect is linked to redox imbalance caused by the generation of reactive oxygen species. This appears to play a key role in the Fenton reaction, further facilitated by an increase in DMT1 or decrease in FTH1 expression, leading to elevated cytosolic iron and lipid peroxide levels. Additionally, the reactive oxygen species may contribute towards the increase in both single and double strands breaks observed in several western blots. Overall, these results suggest that combining TP53 reactivation with chemoradiotherapy could trigger ferroptosis, improving tumour control in HNSCC.