K16, which can be normally expressed in hair follicle suprabasal

K16, and that is usually expressed in hair follicle suprabasal terminally differentiated cells, showed restricted expression inside of the tumor cell mass , suggesting that BCCs undergo inward differentiation. In normal hair follicles, SHH signaling from bulb matrix cells induced K17 expression while in the ORS . By contrast, K17 was ubiquitously expressed all through BCC tumors , consistent with oncogenic SHH signaling in BCC . Whereas K16 and K17 expression is mutually exclusive while in the hair follicle, coincident expression was observed within BCC . Human BCC samples also expressed hair follicle keratins common of the companion layer, inner root sheath , cuticle, and medulla. The companion layer keratin K75 was expressed by six of twenty BCCs studied . Three of twenty BCCs also expressed IRS keratins, but only in a constrained quantity of cells .
Hair shaft keratins weren’t observed in BCC. In summary, by standard H&E staining, BCCs consisted of monomorphic cells disguising a complex pattern of hair folliclespecific keratin expression that implies hierarchical growth with differentiation and multiple tumor cell subpopulations. BCC Cells Express Human Hair Follicle extra resources Bulge Stem Cell Marker CD200. BCC cells express a diverse pattern of hair follicle differentiation demonstrated by intracellular expression of hair folliclespecific keratins. One approach to enrich TIC subpopulations in human BCCs could involve characterization of human BCC heterogeneity by using cell surface differentiation markers that identify keratinocyte stem cells . It has been assumed that BCC arises from KSCs because these cells are sufficiently longlived to sustain the necessary mutations and they already possess the capacity for selfrenewal.
The hair follicle bulge region and other keratinocyte subpopulations have been defined by clusters of differentiation antigens: CD24, CD71, CD146, and CD200 . BCC tumor cell inward differentiation, as manifested by differential hair follicle keratin expression, was also demonstrable by using cell surface markers of epidermal and hair follicle Macitentan differentiation. CD24 localized to cells of the hair follicle IRS and also the interfollicular stratified epidermis, and was similarly restricted to the BCC inner tumor cell mass . The transferrin receptor CD71 identified basal cells below the level in the bulge in hair follicles and was predominantly expressed inside the outermost cell layers of BCC tumor nodules .
CD146 localized to the lower portions on the hair follicle basal layer and surrounding endothelial cells, whereas, in BCC samples, CD146 expression was constrained to blood vessels and was absent from tumor cells . Human hair follicle bulge KSCs reside within the ORS between the origin in the sebaceous gland and arrector pili muscle insertion, and express the cell surface protein CD200 .