Lgr5, a cell surface-expressed Wnt target gene and a receptor for the Wnt‐agonistic R‐spondins (RSPOs) [130], is a novel bonafide marker of adult organ stem cells [131, 132] as well as a functional biomarker of CSCs [133], contributing to cancer stemness traits through the regulation of Wnt/β-catenin signaling pathway [134, 135]. The gene discussed is LGR5; the disease is cancer.