LGR5 (Leucine-rich repeat-containing G protein-coupled receptor 5), also known as GPR49. belongs to the superfamily of G protein-coupled receptors (GPCRs) (1). It is a 907 amino acid multi-pass membrane protein and has multiple N-terminal leucine-rich repeats, which are important for interaction with the glycoprotein ligands, and 7 transmembrane domains. LGR5 is expressed across a diverse range of tissues such as in the muscle, placenta, spinal cord, and brain and particularly as a biomarker of adult stem cells in certain tissues (2). LGR5 is a member of the Wnt signaling pathway. Although its ligand remains elusive, it has been shown that costimulation with R-spondin 1 and Wnt-3a induces increased internalization of LGR5 (3). LGR5 is overexpressed in certain cancer types, e.g. gastrointestinal tumors, and is thought to represent a tumor suppressor, although its role there is still unclear.