Figure 1.

Complex roles of chemokines encompassing both tumor inhibiting and promoting functions. Chemokines are produced directly by tumor cells, tumor -associated vasculature, tissue macrophages and fibroblasts as well as recruited immune cells. Local chemokines shape tumor progression in many ways, often in synergy with other cytokines and metabolites. These include: recruitment of circulating immune cells and/or their retention in the tumor microenvironment; immune cells exerting pro- or anti-tumor immune responses; growth of tumors, including growth and chemoresistance of cancer stem cells; induction of epithelial–mesenchymal transition in tumor cells followed by their transmigration into lymphatic and/or blood vessels; dissemination of tumor cells to sites of secondary tumor growth; induction of angiogenesis; remodeling extracellular matrix by tumor-associated macrophages and cancer-associated fibroblasts. EMT, epithelial–mesenchymal transition; CSC, cancer stem cell; TAM, tumor-associated macrophage; CAF, cancer-associated fibroblast.