CD44 and melanoma: A 5-cell inoculation of melanoma cells mixed with Matrigel and injected into NSG mice had a tumour formation efficiency of 39% (7/18)53, whereas 100 cells of Matrigel-mixed CD44+ subpopulation and CD44+CD24+ESA+ subpopulation from pancreatic cancer PDXs formed tumours at an efficiency of 25% (4/16) and 50% (6/12), respectively54.