Application of three-dimensional collagen scaffolds to recapitulate and monitor the dynamics of epithelial-mesenchymal transition during tumor satellite formation of head and neck cancer

Head and neck squamous cell carcinoma (HNSCC) is a worldwide leading malignancy with poor prognoses. Aggressive HNSCC is manifested by forming tumor satellites in the invasive front, which is closely associated with epithelial-mesenchymal transition, local invasion, and metastasis. Limited by the pathological analyses of static cancer specimens conducted in most previous investigations, the dynamic processes and the decisive factors of tumor satellite formation in HNSCC cannot be monitored and studied. The establishment of a system to recapitulate the phenomenon in vitro may be instrumental to explicitly address the question. In this study, we explored the feasibility of establishing an in vitro system to induce tumor satellite formation of different HNSCC cells by applying a system composed of three-dimensional collagen scaffolds. The real-time dynamic process of tumor satellite formation could be monitored in detail, and the pivotal factors accounting for HNSCC tumor satellite formation were evaluated. E-cadherin remodeling, vimentin aggregation, invadopodia formation, and extracellular matrix degradation occurred in the HNSCC cells when they were cultured in an environment created with a low calcium concentration and steric collagen scaffolds, which altogether contributed to tumor satellite formation and spreading. The phenomena of HNSCC cell transition observed in the current system were confirmed in vivo with compatible findings in surgical specimens. Through the use of this system, we illustrated a novel method to study tumor satellite formation in HNSCC. It may serve as a platform for further investigation of underlying mechanisms for tumor satellites of cancer.