However, 4 weeks following transplantation, SOX2-depleted clones were significantly smaller when compared to control ((NU/NU [088] Charles River) mice were used for orthotypic transplantations and xenograft studies. and the molecular mechanisms that are essential for their viability, Rabbit polyclonal to AADACL3 self-renewal, and long-term tumor initiating Zamicastat potential, and at the same time dispensable for normal tissue stem cell functions. Skin epithelium and cutaneous squamous cell carcinoma (SCC) Zamicastat present powerful model systems in which to investigate whether stemness is usually governed by the same or distinct molecular mechanisms in homeostasis and carcinogenesis. In skin epithelium a number of stem and progenitor cell populations have been identified3C8. Most prominent are hair follicle stem cells (HFSCs) that are located in the lower, Zamicastat permanent part of the hair follicle known as bulge. HFSCs Zamicastat have first been defined based on their slow-cycling behavior9 and elevated colony forming potential10, which enabled the identification of transcriptional11,12 and epigenetic13 signatures that distinguish HFSCs from other skin epithelial cell types. HFSCs have been isolated based on their expression of the cell surface proteins 6 and 1 integrin as well as CD34, cultured on 3T3 feeder layers long-term, and differentiated into all skin epithelial cell lineages upon transplantation onto mice14. These properties defined HFSCs as stem cells and distinguished them from other skin epithelial cell lineages with limited proliferative potential15. Similarly, cutaneous SCC, a hierarchically organized skin cancer that can originate from HFSCs as well as other skin epithelial cells16C18, is usually sustained by cancer cells with tumor initiating potential, which self-renew and also differentiate into tumor cells without the ability to form tumors upon transplantation19. Tumor initiating cells (TICs) in murine cutaneous SCC have been identified at the tumor-stroma interface where they express high levels of 6 and 1 integrin as well as CD3420,21. These cells are able to initiate and propagate SCCs that resemble the phenotypic heterogeneity of their parent in serial transplantation experiments. Differential gene expression analyses defined a characteristic molecular signature that distinguishes TICs in SCCs from normal skin epithelial stem and progenitor cells20. Intriguingly, essential HFSC regulators including Lim homeobox 2 (Lhx2), which maintains hair follicle stem cell function22, T-box protein 1 (Tbx1), which governs their self-renewal23, and nuclear factor of activated T cells 1 (Nfatc1), which restricts their activation24 Zamicastat and functions as a tumor suppressor gene25, are strongly repressed or undetectable in TICs of murine SCCs20 (Fig.1a). This observation suggested the hypothesis that self-renewal and long-term growth of SCC initiating tumor cells may be governed by molecular mechanisms that are distinct from normal skin epithelial stem and progenitor cells from which the tumors originated. Open in a separate window Physique 1 SOX2 expression distinguishes TICs from normal skin epithelial cells(a) Scatter plot illustrating gene expression values of 45,101 transcripts in tumor-initiating cells (TIC) of murine (m) cutaneous squamous cell carcinoma (SCC) compared to hair follicle stem cells (HFSCs). Red and green dots indicate highly enriched transcription factors in mTICs and mHFSCs, respectively. (b) qRT-PCR analyses of Sox2, Pitx1, and Twist1 on RNA from freshly sorted mTICs and mHFSCs. (c) qRT-PCR analysis of Sox2, Pitx1, and Twist1 on RNA from cultured mTICs and mHFSCs. (d) qRT-PCR analysis of SOX2, PITX1, and TWIST1 on RNA from human foreskin (FSK) and SCC13 cultures. (bCd) Data are represented as mean with error bars indicating s.d. (n=3, *P<0.05, Students t-test). (eCg) Western blot analyses of Sox2.