The tumour microenvironment is made up of many components, including endothelial cells, pericytes (PCs), fibroblasts (Fbs), inflammatory cells (e.g., T cells and macrophages), tumour-associated macrophages, cancer-associated fibroblasts and pro-inflammatory molecules secreted by these cells, such as interleukins (e.g., IL-6), chemokines (e.g., CXCL12/SDF-1α), vascular endothelial growth factors (VEGFs) and platelet-derived growth factors (PDGFs), matrix metalloproteinases (MMPs) and components of the extracellular matrix (ECM; e.g., tenascin C, fibronectin and collagen type I). Here, CXCL12 is linked to cancer.