KUSp, a novel oral spindle cell squamous cell carcinoma cell line with epithelial-mesenchymal transition features and high invasive capacity

Spindle cell squamous cell carcinoma (SpSCC) is a rare and aggressive variant of squamous cell carcinoma characterized by biphasic histopathology and epithelial–mesenchymal transition (EMT)-associated features. The scarcity of well-characterized experimental models, particularly those derived from metastatic lesions, has limited investigation of its biology. Here, we established KUSp, a cell line derived from a cervical lymph node metastasis of oral SpSCC, and characterized its pathological, phenotypic, and functional features. The primary tumor showed conventional squamous and spindle cell components, whereas the metastatic lesion predominantly contained spindle-shaped tumor cells expressing both epithelial and mesenchymal markers. KUSp displayed a pronounced EMT-like phenotype characterized by a spindle-shaped morphology, loss of cytokeratin AE1/AE3 and E-cadherin expression, and expression of vimentin, N-cadherin, and α-smooth muscle actin. Functionally, KUSp showed significantly greater Matrigel invasion than the established oral SCC cell lines examined, including HOC313, together with robust migratory activity. These findings characterize KUSp as a patient-derived in vitro model combining pronounced EMT-associated features with high invasive capacity and robust migratory activity, providing a resource for investigating the relationship between EMT-associated phenotypes and invasive behavior in metastatic oral SpSCC.