Myc is required for stem cell amplification induced by deregulated β-catenin signaling. A. Clonal colonies formed by 1000 sorted mammary basal cells. The graph shows the percentage of clonogenic cells (mean ± SEM of 3 independent experiments; *p < 0.01). B. Sphere formation by sorted basal cells. The graph shows the percentage of sphere-forming cells (mean ± SEM of 3 independent experiments; *p < 0.01). Bar: 100 μm. C. Mammary epithelial outgrowths developed from 1000 mammary basal cells transplanted into the cleared mammary fat pads. Bar: 4 mm. D. qPCR analysis of proliferation-related genes. Basal cell samples from K5ΔNβcat;K5Cre;MycF/Fand control mice obtained in 3 independent sorting experiments were analyzed.