LGR5 and cancer: Cross-talk among the multiple signaling pathways induces the expression of special molecules, such as CD24, CD44, CD133 (PROM1), CD166 (ALCAM), CD271 (NGFR), epithelial cell adhesion molecule (EpCAM), LGR5 (GPR49), and aldehyde dehydrogenase (ALDH), and the combined markers have been used to define a small subpopulation with CSC-like properties in various types of cancer [36,40].