LGR5 (Leucine-rich repeat-containing G-protein coupled receptor 5) , also known as GPR49, is a seven-transmembrane receptor and a well-established marker of adult stem cells in intestinal epithelium, stomach, and hair follicles. It is a receptor for R-spondins, which potentiate Wnt/β-catenin signaling. LGR5 is frequently overexpressed in various human cancers, including colorectal cancer, gastric cancer, and hepatocellular carcinoma, where it drives tumor initiation, progression, and chemotherapy resistance. The cynomolgus monkey LGR5 (cyno-LGR5) shares high homology with human LGR5, making this cell line valuable for preclinical drug screening and antibody development targeting LGR5-positive cancers.