The specific contributions of the cancer-associated fibroblasts to tumor growth are poorly understood, but it has been suggested that they are able to promote the growth of mammary carcinoma cells and to enhance tumor angiogenesis [28-30], as well as through the secretion of proteinases (including MMP-1) and other proteins (for example, stromal-cell derived factor 1 (also called CXCL 12), syndecan-1, CXCR4 and Caveolin-1) [31,32]. Here, CXCR4 is linked to cancer.