Abstract 7129: DNA polymerase beta expression in head & neck cancer modulates the poly-ADP-ribose-mediated replication checkpoint
Authors: Khan Md Maruf , Angajala Anusha , Gibbs Denise Y. , Liu Jeffrey C. , Ragin Camille , Sobol Robert W. 
Published: March 2024

Abstract
Head and Neck Squamous Cell Carcinoma (HNSCC) impose a significant health burden, necessitating innovative therapeutic strategies to enhance treatment efficacy. Current standard treatments, including surgery, radiation therapy, and chemotherapy, often exhibit limited effectiveness and cause substantial side effects. This underscores the critical need for novel therapies that selectively target cancer cells, sparing normal tissue. Survival from HNSCC is poor, and importantly, a racial disparity between African Americans (AfAm) and European Americans (EuAm) has been known for some time. Ancestry Informative Markers (AIMs) are associated with altered mRNA expression of Polβ where higher expression of Polβ was observed among AfAm patients in comparison to EuAm patients. Our research focuses on DNA polymerase beta (Polβ) and its role in replication stress and response to chemotherapy and DNA damage response modifiers. Elevated expression of Polβ is linked to increased DNA damage and genomic instability, contributing to treatment resistance. In this regard, our investigations reveal a regulatory role for base excision repair (BER) proteins, including Polβ, in the cellular response to inhibitors of poly(ADP-ribose) glycohydrolase (PARG), an enzyme involved in poly(ADP-ribose) (PAR) degradation. Inhibition of PARG triggers a robust intra-S phase response, activating ATR and CHK1 signaling. Exploiting the synthetic lethality between PARG inhibition and ATR/CHK1 inhibition, we have demonstrated the ability to overcome Polβ overexpression mediated treatment resistance in HNSCC cells. Specifically, our in vitro studies demonstrate that the response to a combination of an ATR inhibitor and PARG inhibitor is impacted by Polβ expression in HNSCC cells, with synergistic effects surpassing the efficacy of the individual inhibitors. Similarly, the combination of a CHK1 inhibitor and PARG inhibitor proves effective in cells with elevated Polβ expression, offering a potential dual therapeutic strategy. These combinations exhibit promising potential for HNSCC treatment when Polβ expression is elevated. In conclusion, our findings propose a novel therapeutic paradigm for HNSCC, employing combination therapy with ATR or CHK1 inhibitors and PARG inhibitors. This approach offers a targeted strategy, presenting a promising avenue for the development of more effective and less toxic treatment modalities in the management of HNSCC and may help overcome resistance from elevated expression of Polβ.
Citation Format: Md Maruf Khan, Anusha Angajala, Denise Y. Gibbs, Jeffrey C. Liu, Camille Ragin, Robert W. Sobol. DNA polymerase beta expression in head & neck cancer modulates the poly-ADP-ribose-mediated replication checkpoint [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7129.