Single-Cell Transcriptomic Analysis Identifies an Invasive Epithelial Subpopulation Associated with the TGFβ–SERPINE1 Axis in HNSCC

Background: Head and neck squamous cell carcinoma (HNSCC) is highly aggressive and prone to local recurrence, but the underlying mechanisms remain unclear. Methods: Single-cell RNA-seq and integrative transcriptomic analyses were used to identify invasive malignant epithelial subpopulations and candidate TGFβ-responsive genes. Transwell assays and Western blotting were performed to assess migration, invasion, and EMT in HNSCC cells. Results: Single-cell analysis identified a malignant epithelial subpopulation with high EMT activity and stemness-related features. SERPINE1 was identified as a candidate TGFβ1-responsive gene. SERPINE1 knockdown reduced cell migration, invasion, and EMT-associated changes and partially attenuated the effects of TGFβ1 treatment. Conclusions: Together, these findings identify an invasive epithelial subpopulation in HNSCC and highlight the TGFβ–SERPINE1 axis as an important molecular feature of this subpopulation.