Metastatic spread is mainly sustained by cancer stem cells (CSC), a subpopulation of cancer cells that displays stemness features. CSC are thought to be derived from cancer cells that undergo epithelial to mesenchymal transition (EMT), thus acquiring resistance to anoikis and anti-cancer drugs. After detachment from the primary tumor mass, CSC reach the blood and lymphatic flow, and disseminate to the target tissue. This process is by nature dynamic and in vitro models are quite far from the in vivo situation. In this study, we have tried to reproduce the adhesion process of CSC to a target tissue by using a 3D dynamic cell culture system. We isolated two populations of 3D tumor spheroids displaying CSC-like features from breast carcinoma (MCF-7) and lung carcinoma (A549) cell lines. Human fibroblasts were layered on a polystyrene scaffold placed in a dynamically perfused millifluidic system and then the adhesion of tumor cell derived from spheroids to fibroblasts was investigated under continuous perfusion. After 24 h of perfusion, we found that spheroid cells tightly adhered to fibroblasts layered on the scaffold, as assessed by a scanning electron microscope (SEM). To further investigate mechanisms involved in spheroid cell adhesion to fibroblasts, we tested the effect of three RGD integrin antagonists with different molecular structures on cell adhesion; when injected into the circuit, only cilengitide was able to inhibit cell adhesion to fibroblasts. Although our model needs further refinements and improvements, we do believe this study could represent a promising approach in improving current models to study metastatic infiltration in vitro and a new tool to screen new potential anti-metastatic molecules.
Keywords: 3D culture; EMT; SEM analysis; cell adhesion; dynamic model; integrins; metastasis.