Mesenchymal-epithelial transition in lymph node metastases of oral squamous cell carcinoma is accompanied by ZEB1 expression

Abstract

Oral cavity squamous cell carcinomas (OSCC) that spread to the regional lymph nodes are associated with a high degree of epithelial-mesenchymal plasticity (EMP). Here, RNA sequencing of 1,946 carcinoma and 2,175 stromal cells of an advanced metachronous OSCC lymph node metastasis revealed heterogeneity of the OSCC cells with respect to epithelial-mesenchymal transition (EMT) states, metabolic adaptations, and cell cycle. Seven cell clusters formed a branching trajectory with epithelial differentiation, partial EMT states and metabolic adaptations. Notably, partial EMT was associated with stress response, especially with HSPA upregulation, immune-modulation through CXCL14 and a higher fraction of proliferating cells, whereas epithelial differentiation correlated with higher cytokeratin and kallikrein expression. While EMP-associated transcription factors SNAI2 and ZEB1 were active in all cancer cells, TWIST1, SNAI1 and ZEB1 activity were more pronounced in the epithelial branch. Epithelial differentiating cells have less receptor-ligand interactions with stromal cells than partial EMT cells indicating a more independent regulation. Interestingly, cells in and close to the trunk of the trajectory adapt to hypoxic and hypoglycemic conditions expressing genes related to glycolytic and amino acid catabolism. Our work provides in-depth insights into phenotypic heterogeneity within an OSCC lymph node metastasis, specifically how EMP drives locoregional progression.