[Techniques to study transendothelial migration in vitro]

The most dangerous aspect of cancer is the metastatic spread to other parts of the body. Cancer cells frequently use circulation to spread to secondary locations. By entering the blood-stream (in a process called intravasation) and by crossing the vessel walls at the metastatic sites (extravasation) tumor cells disseminate to distal organs and eventually form life  threatening metastases. Crossing the vessel walls (transendothelial migration) is a vital step of metastatic cascade and the elucidation of mechanisms involved in transendothelial migration might inspire new strategies of targeted antimetastatic therapy. There are several methods to study transendothelial migration in living models (in vivo). Although they offer complex physiological microenvironment, they are expensive and technically demanding, therefore not widely used. As an alternative, sophisticated techniques to investigate transendothelial migration in vitro have been developed. They are generally more available and feasible, but there is still considerable variability in the difficulty of performance, the requirements for specialized devices, accuracy of in vivo simulation and relevance for oncological applications. The classification, various modifications, pros and cons of in vitro techniques for studying transendothelial migration are summarized in this review.