Differentiation of cells from head and neck squamous cell carcinoma that are positive for human papillomavirus

Head and neck squamous cell carcinoma (HNSCC) is a highly malignant disease, death rates have remained at around 50%. Therefore, new treatment strategies are urgently needed. In a previous study, we investigated the differentiation of human papillomavirus (HPV)-negative HNSCC cells through cornification and discovered that cell malignancy was lost due to epigenetic factors. Understanding the mechanisms underlying HNSCC cell differentiation can help identify targets for anti-tumor therapy. We created an HNSCC differentiation model in HPV-positive tumor cells. Observed a loss of malignant characteristics in HPV-positive cell cultures similar to HPV-negative cells. This included irregular enlarged cell morphology, cell cycle arrest with Ki67 downregulation, and reduced cell viability. Although cornification was detected in HPV-positive tumor cell cultures and HPV-positive FFPE tumor tissue sections, it was not induced during HPV-positive 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 primary HPV-positive HNSCC cells confirmed the upregulation of these markers and the formation of parallel actin fibers, reminiscent of myoblast-lineage cells. Moreover, multi-marker immunofluorescence analysis of HPV-positive tumor tissue sections revealed areas of cells co-expressing markers of myofibril assembly, HPV surrogate marker p16, and stress-associated basal keratinocyte marker KRT17. This indicates that the observed myocyte-like differentiation also occurred in human tissue.