Keratin K15 as a Biomarker of Epidermal Stem Cells

The document reviewed the role of Keratin 15 (K15) as a potential biomarker for epidermal stem cells, discussing its expression in the basal keratinocytes of stratified epithelia and its association with stem cell characteristics in the bulge of hair follicles. However, the review highlighted the variable expression of K15 and its presence in both normal and diseased tissues, which challenges its specificity as a stem cell marker. The authors concluded that K15 expression alone is not sufficient to reliably identify epidermal stem cells due to its presence in both stem and differentiated cells. They also discussed the role of K15 in structural support, its potential compensatory function in epidermolysis bullosa, its involvement in skin tumor carcinogenesis, and its regulation by FOXM1 and PKC/AP-1 signaling pathways. The review suggested that while K15 is part of the stem cell marker profile, it should not be used in isolation to identify stem cell populations.