ALCAM and neoplasm: Limiting dilution cell transplantation analysis for tumour initiation showed that as few as 500 CD166+ cells could be serially propagated in immunodeficient NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice, whereas 100,000 CD166− cells had no ability to form tumours in serial transplantation assays performed subcutaneously (Fig. 1b).