The tumor microenvironment, consisting of stromal cells, immune cells, and the ECM, plays a significant role in invasion and metastasis. Cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs) can secrete growth factors and cytokines that promote invasion and metastasis. The interaction between cancer cells and the microenvironment can also induce epithelial-mesenchymal transition (EMT), a process that enhances cell motility.
