Figure 1.

Main barriers that restrict the efficient traffic of effector cells towards tumors. The tumor microenvironment is a hostile environment for antitumor effector cell infiltration. This is achieved through multiple mechanisms such as: (1) mismatch between the chemokine receptors and chemokine pool in the tumor microenvironment; (2) decrease in the expression of adhesion molecule on the tumor endothelium; (3) aberrant vasculature that leads to inefficient traffic of immune cells; (4) tumor endothelium acting as a barrier.