Abstract 5818: Differentiation of human papillomavirus-positive head and neck squamous cell carcinoma cells

Abstract Head and neck squamous cell carcinoma (HNSCC) represents a highly malignant disease and death rates remain at approximately 50% for decades. Thus, new tumor-targeting treatment strategies are desperately needed. In a previous study, we dissected human papillomavirus (HPV)-negative HNSCC cell differentiation via cornification and detected an epigenetically determined loss of cell malignancy. Analyzing the mechanisms underlying the differentiation of HNSCC cells may identify targets for anti-tumor therapy. Using patient-derived tumor cells, we created an HNSCC differentiation model in HPV+ tumor cells. Similar to HPV- cells, we observed a loss of malignant characteristics in HPV+ cell cultures in differentiating cell culture conditions including irregular enlarged cell morphology, cell cycle arrest with downregulation of Ki67, and reduced cell viability. Even though cornification was detected in HPV+ tumor cell cultures and HPV+ FFPE tumor tissue sections, cornification was not induced during HPV+ cell differentiation. Instead, RNA-seq and subsequent Gene Ontology analysis showed myocyte-like differentiation with upregulation of markers of myofibril assembly including TPM1, TAGLN, and ACTA1. Immunofluorescence staining of differentiated and undifferentiated primary HPV+ HNSCC cells confirmed an upregulation of these markers and the formation of parallel actin fibers, reminiscent of myoblast-lineage cells. Moreover, multi-marker immunofluorescence analysis of HPV+ tumor tissue sections revealed areas of cells co-expressing the identified markers of myofibril assembly, HPV surrogate marker p16, and stress-associated basal keratinocyte marker KRT17, indicating that the observed myocyte-like differentiation observed in vitro also occurred in human tissue. Normal tissue displayed a co-expression of TPM1, TAGLN, and ACTA1 in differentiating keratinocytes between the basal cell layer and the fully differentiated corneocytes. This shows that the expression of myocyte-lineage markers is reflected in differentiating non-malignant mucosal tissue. Our study suggests that the targeted differentiation of tumor cells might be therapeutically valuable in HPV+ HNSCCs as well. Citation Format: Sarah Gendreizig, Laura Martinez-Ruiz, Javier Florido, Alba López-Rodríguez, Harkiren Pabla, Frank Brasch, Germaine Escames, Tobias Busche, Holger Sudhoff, Lars U. Scholtz, Ingo Todt, Felix Oppel. Differentiation of human papillomavirus-positive head and neck squamous cell carcinoma cells [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 5818.