Human cutaneous squamous cell carcinoma (SCC) is the second most common type of non-melanoma skin cancer (NMSC) after basal cell carcinoma (BCC) in US. Evidence indicates that the precursor cells are the precursor cells for the origin of SCC. The SCCs probably arise from bulge stem cell niche of hair follicle but not from the transit amplifying cells of epidermis. The SKH1 hairless mice is a widely used mouse model for ultraviolet radiation (UV)-induced carcinogenesis. However, SKH1 mice have never been evaluated for status of skin stem cell probably due to absence of hair and other associated hairless phenotype. It has recently become possible to isolate living hair follicle stem and progenitor cells from mouse skin because of the discovery of cell surface marker (CD34) that facilitate enrichment. The cell surface protein CD34, more widely known as a hematopoietic stem and progenitor cell marker, was found to be uniquely expressed in the mouse hair follicle bulge region using immunohistochemistry staining techniques. In addition, CD34 expression was restricted to the hair follicle regardless of hair follicle stage, making this a potentially important tool for selected enrichment of hair follicle bulge region keratinocytes. In combination with alpha 6-integrin staining and fluorescence activated cell sorting (FACS), CD34 is used to successfully isolate a small population of CD34+/alpha 6-integrin+ cells from a single cell preparation of mouse keratinocytes. CD34-expressing keratinocytes were confirmed to have properties consistent with stem and progenitor cells in that they were shown to be slowly cycling and have a high proliferative capacity in culture, growing larger colonies relative to those from CD34 keratinocytes. In the present experiments, the SKH1 mouse skin stem cell population was identified using stem cell markers (CD34+/α6-integrin+, Keratin-15, Gli1, and Sox9). The results of FACS analysis of live cells, isolated from untreated SKH1 mouse skin, indicate that there are 0.23% CD34+ and 1.05% CD34+/α6-integrin+ cells. The FACS sorted double positive (CD34+/α6-integrin+) stem cells of SKH1 are also observed to be positive for K15, Gli1, and Sox9 markers of stem cells in cytospin slides. In summary, the quantitative FACS analysis and qualitative immunofluorescence data in skin tissues confirms the presence of the stem cell populations in SKH1 mice. Support: (RO1CA102431).

Citation Format: Ashok Singh, Anupama Singh, Ajit K. Verma. Characterization of epidermal stem cells in SKH1 hairless mice, a widely used mouse model to investigate ultraviolet radiation carcinogenesis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5020. doi:10.1158/1538-7445.AM2013-5020