Fig. 2

Potential cellular sources of CAFs. Cancer-associated fibroblasts (CAFs) can originate from diverse cell populations. Sources of CAFs include pre-existing resident fibroblasts and stellate cells (which become CAFs through activation), epithelial cells (via epithelial-to-mesenchymal transition, EMT), endothelial cells (via endothelial-to-mesenchymal transition, EndMT), mesenchymal stem cells (MSCs), and circulating fibrocytes (via recruitment), as well as pericytes, smooth muscle cells, and adipocytes (through transdifferentiation). ECM extracellular matrix; α-SMA α-smooth muscle actin; S100A4 fibroblast specific protein-1, also called FSP-1