LGR5 and colorectal cancer: Leucine-rich repeat-containing G-protein coupled receptor 5 (LGR5), a transcriptional target gene of the Wnt signalling pathway, is overexpressed in multiple cancers, including colorectal cancer (CRC), hepatocellular carcinoma (HCC) and pre-B acute lymphoblastic leukaemia (pre-B ALL) and has emerged as a promising therapeutic target.