CXCL1 and breast cancer: In addition to the constitutive production by BCSCs, and possibly other BC cells and stromal mesenchymal stem cells (Wang Y. et al., 2017), CXCL1 can be dynamically induced, during tumor progression, in macrophages, MDSCs, granulocytes, endothelium and fibroblasts, by a variety of stimuli such as IL1β, TNFα (Wen et al., 1989; Acharyya et al., 2012), IL6 (Roy et al., 2012), PGE2 (Wang et al., 2006), adipokines (Wang et al., 2020), and TLR3/4 (Zhao et al., 2014).