CXCL4, also called PF4, is a small cytokine belonging to the CXC chemokine family and it is also known as chemokine (C-X-C motif) ligand. Mature mouse CXCL4 shares 76%, 88%, 64%, 64% and 63% amino acid sequence identity with human, rat, ovine, porcine and bovine CXCL4, respectively. Recombinant mouse CXCL4 contains 76 amino acids which is a single non-glycosylated polypeptide chain. CXCL4 can be antiproliferative and antiangiogenic, at least in part via interfering with FGF-2 and VEGF heparin binding and thus inhibiting their signaling. Tumor tissue revealed up-regulation of CXCL14 in cancer-associated fibroblasts of a majority of prostate cancer. Fibroblasts overexpressing CXCL14 promoted the growth of prostate cancer xenografts, and increased tumor angiogenesis and macrophage infiltration.