In two separate studies [38], [39], researchers examined the gene expression profile of 4T1 tumor cells in comparison to less metastatic cell lines, finding a variety of up-regulated pro-migratory soluble factors including (a) growth factors angiopoietin 2, VEGF-C, insulin-like growth factor 2, (b) chemokines CCL5, CCL7, CXCL1, CXCL16, CSF2, CSF3, (c) interleukins 1α and 23, and (d) matrix metalloproteases 13,3,9. This evidence concerns the gene CCL5 and neoplasm.