Loss of MACROD2 drives radioresistance but not cisplatin resistance in HPV-positive head and neck cancer.

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer type worldwide. In recent years, there has been an increase in the rate of HNSCC cases attributed to the infection of the oropharynx by the human papillomavirus (HPV). Given the significant treatment-related toxicities of the current standard of care for HPV-positive HNSCC, there is an urgent need for the development of precision patient stratification and treatment strategies to improve patients' quality of life while maintaining excellent survival rates. We have previously carried out whole genome sequencing of HPV+ HNSCC tumors that failed concurrent cisplatin and radiation treatment and discovered that MACROD2 deletion is enriched among these tumors. In the current study, we sought to investigate the mechanistic role of MACROD2 in HPV+ HNSCC treatment resistance. Our results indicate that MACROD2 depletion in HNSCC cell lines leads to increased cell viability and colony formation capacity. Interestingly, MACROD2 depletion did not alter cisplatin sensitivity but led to an increase in radiation resistance of HPV+ HNSCC cell lines. RNA sequencing and immunofluorescence microscopy demonstrated that MACROD2-depleted HPV+ HNSCC cells displayed elevated levels of hypoxia and an altered DNA damage response. Taken together, this study establishes and characterizes the role of MACROD2 in HPV+ HNSCC radioresistance. Further work is needed to validate MACROD2 as a biomarker of treatment failure and to understand how to overcome the identified molecular mechanisms of resistance.