The CXCL1/KC gene was initially identified as being regulated by PDGF in BALB/c-3T3 cells. CXCL1/KC is an ELR CXC chemokine, and it is structurally and functionally related to the human GROs (CXCL1-CXCL3) and interleukin-8 (CXCL8). CXCL1, CXCL2, and CXCL3 bind to the CXCR2 receptor, with CXCL1 having the highest affinity. CXCL1 is crucial for the recruitment of neutrophils to inflammatory sites. In addition, CXCL1 has pleiotropic effects on cell proliferation, tumor angiogenesis, invasion, and metastasis. CXCL1 and CXCL2 induce neutrophil mobilization from the bone marrow in a murine model of acute peritonitis, and CXCL1 and G-CSF act cooperatively in this process. In addition, CXCL1 mediates murine sickle cell vasoocclusion during hemolytic transfusion reactions. Thrombin enhances the secretion of CXCL1 from tumor cells, and PGE2 stimulates expression of CXCL1 in human colorectal carcinoma cells (CRC). Furthermore, CXCL1 (secreted by CRC cells) induces endothelial cell migration and tube formation in vitro and in vivo. CXCL1 is induced by inflammatory cytokines such as IL-1 and TNF, and IL-17A enhances expression of CXCL1 by prolonging the half-life of its constitutively unstable mRNA.