Fig. 4

A diagrammatic representation of the interplay among immune cells and CRC cells unveils the molecular mechanism underpinning CRC metastasis. The inborn immune system is comprised of macrophages, neutrophils, monocytes, eosinophils, basophils, and natural killer cells, while the acquired immune system includes B cells, CD8 + T cells, and CD4 + T cells. When the innate immune system becomes imbalanced, it can contribute to the metastasis of CRC. One critical aspect contributing to the promotion of CRC metastasis is the secretion of molecules such as Chemokine Receptor (CCR), Chemokine Ligand (CCL) and Interleukin by immune cells. These molecules play a pivotal role in creating a microenvironment conducive to EMT of tumor cells. Moreover, these molecules may suppress the immune surveillance mechanisms that would otherwise identify and eliminate cancer cells. In addition to chemokines, various components within the tumor microenvironment contribute to immune evasion and thus facilitate metastasis. Exosomes, for instance, tiny vesicles released by tumor cells, can carry immunosuppressive molecules that dampen the activity of immune cells. Cancer-associated fibroblasts (CAFs) and tumor-associated neutrophils (TANs) also play a role in creating an immunosuppressive microenvironment