Abstract A003: HPV infection causes dependence on alternative DNA damage response pathways providing cancer specific targets for radiosensitization

Abstract

Abstract Targeted radiosensitization is an attractive approach to improving the efficacy of radiotherapy in cancer treatment. However, drugs targeting ubiquitous DNA damage response (DDR) pathways are not cancer specific and can increase radiation related side effects. Thus, there is an unmet clinical need for tumor specific molecular targets. To address this need we sought to identify DNA damage signaling pathways that are unique to cancer cells. We hypothesized that by expressing its genome in host cells high-risk Human Papilloma Virus (HPV) can rewire DNA damage signaling making HPV-positive tumor cells dependent on alternative pathways to survive radiation, which can be exploited for targeted radiosensitization of HPV-induced cancers. Using a CRISPR/Cas9 screen in cells that selectively express HPV16 proteins E6 or E7 we uncovered genes that cells rely on to survive radiation-induced DNA damage in the context of E6 or E7 expression. We demonstrate that targeting these newly identified genes sensitizes cancer cells to radiation specifically in the presence of E6 or E7. We provide mechanistic insights showing that E6 and E7 alter the cellular epigenome by inhibiting histone lysine acetylation and tri-methylation, respectively. In this setting, a member of a centromeric protein complex identified in the screen is critical for mitotic progression and survival in E6-expressing cells following radiation exposure. Deletion of this factor resulted in delayed mitotic progression, chromosomal missegregation and rapid post-mitotic death in irradiated HPV-positive cells, a phenotype that was mitigated by ablation of E6 expression. Furthermore, we identified an E3 ubiquitin ligase that promotes survival in E7-expressing cells following radiation exposure by alleviating perturbations during DNA replication. Together, we have uncovered DDR pathways that are critical for cell survival after radiation exposure specifically in HPV-positive cells. Our findings suggest that expression of viral proteins E6 and E7 rewires DNA damage signaling networks causing dependence on alternative response pathways. We propose that these pathways can be targeted for tumor-specific radiosensitization of HPV-induced cancers. Citation Format: Michael Goldstein, Akhil Kotwal, Nishanth Gabriel, William Buchser, Monica Sentmanat, Stephanie Markovina, Julie Schwarz, Xia Cui. HPV infection causes dependence on alternative DNA damage response pathways providing cancer specific targets for radiosensitization [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: DNA Damage Repair: From Basic Science to Future Clinical Application; 2024 Jan 9-11; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2024;84(1 Suppl):Abstract nr A003.