To investigate IL4Rα expression in the individual cell subpopulations, we separated SC, TA and CB according to their surface markers, as previously described.12, 27, 28 The functional isolation of SC, TA and CB subpopulations (based on their clonogenic potential) was confirmed (Supplementary Figure 1A), and quantitative real-time PCR analysis of the SC, TA and CB subpopulations revealed that receptor expression was significantly increased in the cancer (C)SC and cancer transit amplifying subpopulation within the basal cell population compared with their benign counterparts (Figure 1e). Here, IL4R is linked to cancer.