CXCR4 is the most common chemokine receptor in solid human cancers, including breast [37], melanoma [8], renal cell [38], brain [9, 39], thyroid [10, 40], non-small cell lung [11, 41], pancreatic [12, 42], ovarian [13, 43], prostate [14, 44], and colorectal [15, 45] cancers. Here, CXCR4 is linked to cancer.