The myoepithelial layer is murine in humanized glands. Ducts humanized with 4G-shp53 cells were costained for p63 (red), GFP (green) and DNA (DAPI, blue) (n = 3). All injected human cells express GFP strongly. Green arrow, human luminal cells in a humanized duct; red arrow, murine myoepithelial cells in a murine duct. Scale bars 50 μm.