Figure 3.

Selected microfluidic platforms for studying breast cancer intravasation, the process by which invading cancer cells enter a blood or lymphatic vessel allowing their passive transport to distant organs as CTCs. Once capable of moving through the ECM, motile breast cancer cells have been found to follow collagen fibers that lead from their primary site to nearby blood or lymph vessels. However, breast cancer cells are often incapable of penetrating the basal lamina or the endothelial cell layer surrounding the lumen of these vessels due to cadherins forming tight intercellular junctions. This seems to be overcome with the assistance of various signaling pathways and macrophage interactions forming a microenvironment that enables cancer cells to penetrate the vasculature.