Targeting the DNA Damage Response in HPV+ Head and Neck Cancer

Project Summary Human papilloma virus (HPV)-positive head and neck squamous cell carcinoma (HNSCC) is a growing public health burden and has already surpassed cervical cancer as the most common HPV-related malignancy in the United States. While HPV+ HNSCC patients have generally good survival, they suffer from life-long chemoradiotherapy-related morbidities. Current data is insufficient to inform de-intensification of standard chemoradiotherapy or the development of targeted therapies. My ultimate goal is to understand the mechanisms by which HPV disrupts DNA damage response (DDR) signaling during HNSCC development, and to thereby inform the rational design of new targeted therapies. In considering new strategies to effectively control HPV+ HNSCC, I noted that HPV's oncogenic E6 and E7 proteins abrogate tumor suppressor pathways and impair DDR signaling to cause genomic instability. The Mendez lab and others have established DDR kinase WEE1 inhibition via the specific inhibitor AZD1775 (WEE1i) as a new therapeutic strategy in HNSCC, and that HPV+ HNSCC tumors are hypersensitive. WEE1 inhibition causes S-phase replication stress (RS) and irreparable DNA damage. Combined with genotoxic chemotherapy (e.g., cisplatin), WEE1i abrogates the G2/M checkpoint and causes premature mitosis. I recently showed that HPV16 E6/E7 oncoproteins sensitize HNSCC cells to WEE1i monotherapy through activation of a FOXM1-CDK1 circuit that drives mitotic gene expression and DNA damage. I also showed that elevated basal FOXM1 activity predisposes HPV+ HNSCC to WEE1i-induced toxicity. Next, I used an RNAi genetic screen to identify RS and DDR targets that synergize with WEE1i; based on my findings to date, I hypothesize that disruption of RS and DDR pathways by E6/E7 provide exploitable vulnerabilities for a combination targeted therapy that also includes WEE1i. I plan to clarify the mechanisms by which HPV sensitizes cancer cells to WEE1i-induced replication failure (Aim 1) and compromises DNA repair pathways upon WEE1 inhibition (Aim 2). I will use murine cancer models to test novel therapeutic combinations for targeting RS/DDR defects in HPV+ HNSCC and identify the situations in which they are most effective. In parallel, I will use a targeted quantitative proteomics approach to determine the E6/E7-specific RS and DDR responses to WEE1i, and multi-panel flow cytometry to determine the WEE1iassociated changes in the immune landscape of E6/E7-driven tumors in immunocompetent mice. This award will help me develop my scientific ideas and increase my competency in working with the mouse models that faithfully recapitulate human cancer. The scientific advances that I make during this training period will be critical to my ultimate goal of establishing an independent research program that focuses on how HPV drives HNSCC development and how HPV+ HNSCC might be more safely and effectively treated.