These precursor cells are activated, recruited, or trans-differentiated into CAFs under the stimuli of multiple factors in tumors desmoplastic microenvironments, including oxidative stress, local hypoxia, physical changes in the ECM, exosomes and DNA damage during radiation therapy, cancer-derived cytokines such as transforming growth factor-β (TGF-β), interleukin-6 (IL-6), platelet-derived growth factor (PDGF), stromal derived factor 1 (SDF1) and hepatocyte growth factor (HGF) [1, 26, 27, 30]. This evidence concerns the gene CXCL12 and cancer.