In both genome-wide and airway basal cell signature-restricted analyses, airway epithelium basal cells exhibited similarity to cells with basal cell characteristics, such as CD44+ breast epithelial stem cells, and p63-overexpressing cervical cells and keratinocytes, but had more distant relationships with basal-like breast cancers and fibroblasts (Figures 3A, 3B). Here, CD44 is linked to breast cancer.