CXCR4 and cancer: In colorectal cancers, a relatively rare population of cells that expresses distinct set of cell surface markers, such as CD133, CD44, C-X-C chemokine receptor type 4 (CXCR4) and Leucine-rich repeat-containing G-protein coupled receptor 5 (LGR5), have been identified as highly tumorigenic and are referred to as cancer stem cells (CSCs) [5, 6].