LAUSR

The incidence of HPV-positive head and neck squamous cell carcinoma (HNSCC) is now being considered an epidemic in the US and Western Europe as rates have surpassed those for cervical cancer. For approximately 14,400 patients per year in the US, initial therapy is aggressive and often results in adverse lifelong side effects such as difficulty swallowing and speaking. Despite having a higher cure rate than HPV-negative HNSCC, the recurrence rate is still approximately 30%. Therefore, new treatment options need to be available for these relapsed patients. Our lab was prompted to explore demethylation as a therapeutic option as HPV-positive HNSCC have a more hypermethylated genome than HPV-negative cancers. 5-azacytidine (5-aza) is a synthetic cytidine analog that causes DNA demethylation by trapping methyltransferases to chromatin; it is FDA-approved for the treatment of myelodysplasia and acute myeloid leukemia. Our lab found that low doses of 5-aza delayed HPV-positive xenograft tumor growth and that HPV-positive tumor samples from patients treated with 5-aza in a window trial had increased apoptosis. They also observed a marked downregulation of HPV gene expression after 5-aza. Decreased HPV E6 expression, followed by reactivation of tumor suppressor p53, induced p53-dependent apoptosis in HPV-positive HNSCC. To further explore the mechanism of this sensitivity to 5-Aza, we first determined that 5-aza regulates the transcription of HPV genes, but not the stability of HPV transcripts. We found that the transcriptional regulation of HPV genes after 5-aza depends on the proto-oncogene JunB, a component of the transcription factor Activator Protein 1 (AP-1). Additionally, silencing of JunB abolished the expression of HPV E6/E7 genes and reactivated tumor suppressor p53 in HPV-positive HNSCC. Furthermore, we revealed that clonogenic survival of HPV-positive head and neck cancer cells is dependent on JunB expression. Our study exposes an important component of 5-Aza-associated sensitivity and toxicity in HPV-positive HNSCC and identifies a novel dependency on JunB, potentially providing a new rational targeted therapy. Citation Format: Hina Rehmani, Travis P. Schrank, Natalia Issaeva, Wendell G. Yarbrough. JunB regulates expression of HPV genes in head and neck cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3925.