A study on esophageal squamous cell carcinoma demonstrated that PAI-1 derived from cancer-associated fibroblasts (CAFs) promotes macrophage migration by activating Akt and Erk 1/2 through interaction with low-density lipoprotein receptor-related protein 1 (LRP1), an endocytic receptor on macrophage surfaces [31]. Here, LRP1 is linked to cancer.