Fig. 1

The origins of CAFs and its surrounding microenvironment components in tumor. CAFs are heterogeneous stromal cells abundantly existed in the TME, which have different cell sources activated by extensive TME-derived stimulants such as TGF-β, PDGF and other biological effect factors. Of which quiescent stellate cells and local resident normal fibroblasts, are the primary origin of CAFs; mesenchymal stem cells (MSCs), epithelial cells, adipocytes, pericytes, endothelial cells, and smooth muscle cells are also sources of CAFs within limited conditions. (The upper half of the figure portray the underlying origins of CAFs, while the lower half of the figure depict the tumor microenvironment components including various stromal cells and ECM around the CAFs)