Nano-biomechanical Validation of Epithelial–Mesenchymal Transition in Oral Squamous Cell Carcinomas

The effective cure for oral squamous cell carcinoma (OSCC) patients is challenging due late diagnosis and fatal metastasis. The standard diagnosis for OSCC often depends on the subjective interpretation of conventional histopathology. Additionally, there is no standard way for OSCC prognosis. Over the past decade, nano-mechanical stiffness has been considered as a quantitative measure for cancer diagnosis. Nevertheless, its application to OSCC diagnosis and prognosis is still in a primitive stage. In this study, we investigated whether the OSCC progression can be predicted by nano-mechanical properties in combination with biochemical properties, especially the epithelial–mesenchymal transition (EMT). Atomic force microscopy-based nano-mechanical measurements of three different OSCC cell lines—SCC-4, SCC-9, and SCC-15—were conducted together with biochemical analyses. The gradual upregulation of Snail2, N-cadherin, and vimentin and the simultaneous downregulation of E-cadherin were observed, and the degree of upregulation and downregulation was stronger in the order of the cell lines mentioned above. The strength of enhancement in migration was in the same order as well. Consistently, nano-mechanical stiffness was gradually decreased as the EMT progresses. These results suggest that the nano-mechanical assay could serve as a quantitative tool to predict the OSCC progression in the context of the EMT. Furthermore, we found that the upregulated vimentin, a major filamentous component of the cytoskeleton, may contribute to mechanical softening, which can be discerned from the role of actin filaments in mechanical stiffness. In conclusion, our combinational study proposes a novel way to elucidate the mechanism of OSCC progression and its therapeutic targets.