Human papillomavirus-associated head and neck squamous cell carcinoma cells lose viability during triggered myocyte lineage differentiation
Head and neck squamous cell carcinoma (HNSCC) is a highly malignant disease, and death rates have remained at approximately 50% for decades. New tumor-targeting strategies are desperately needed, and a previous report indicated the triggered differentiation of HPV-negative HNSCC cells to confer therapeutic benefits. Using patient-derived tumor cells, we created a similar HNSCC differentiation model of HPV+ tumor cells from two patients. We observed a loss of malignant characteristics in differentiating cell culture conditions, including irregularly enlarged cell morphology, cell cycle arrest with downregulation of Ki67, and reduced cell viability. RNA-seq showed myocyte-like differentiation with upregulation of markers of myofibril assembly. 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, immunofluorescence of HPV+ tumor tissue 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 in vitro differentiation occurs in human tissue. We are the first to report that carcinoma cells can undergo a triggered myocyte-like differentiation, and our study suggests that the targeted differentiation of HPV+ HNSCCs might be therapeutically valuable. Overall design: Primary head and neck squamous cell carcinoma cell cultures were established in a serum-free medium to investigate the differentiation potential of HNSCC. The cells were differentiated with a serum medium and cultured for 8 days until full differentiation was achieved. Both cultures under the control condition (PNEU) and the differentiation condition (CFM) have been analyzed using RNA-seq.