Hindawi Publishing Corporation Journal of Skin Cancer Volume 2013, Article ID 452425, 13 pages http://dx.doi.org/10.1155/2013/452425 Research Article Protein Kinase C, Which Is Linked to Ultraviolet Radiation-Induced Development of Squamous Cell Carcinomas, Stimulates Rapid Turnover of Adult Hair Follicle Stem Cells Ashok Singh, 1 Anupama Singh, 1 Jordan M. Sand, 1,2 Erika Heninger, 3 Bilal Bin Hafeez, 1 and Ajit K. Verma 1 1 Department of Human Oncology, Wisconsin Institutes for Medical Research, School of Medicine and Public Health, 1111 Highland Avenue, University of Wisconsin, Madison, WI 53705, USA 2 Molecular and Environmental Toxicology Center, Wisconsin Institutes for Medical Research, Paul P. Carbone Comprehensive Cancer Center, School of Medicine and Public Health, University of Wisconsin, Madison, WI 53705, USA 3 UWCCC Flow Cytometry Core Facility, School of Medicine and Public Health, University of Wisconsin, Madison, WI 53705, USA Correspondence should be addressed to Ajit K. Verma; akverma@wisc.edu Received 3 March 2013; Accepted 21 March 2013 Academic Editor: Deric L. Wheeler Copyright © 2013 Ashok Singh et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. To ind clues about the mechanism by which kinase C epsilon (PKC) may impart susceptibility to ultraviolet radiation (UVR)- induced development of cutaneous squamous cell carcinomas (SCC), we compared PKC transgenic (TG) mice and their wild- type (WT) littermates for (1) the efects of UVR exposures on percent of putative hair follicle stem cells (HSCs) and (2) HSCs proliferation. he percent of double HSCs (CD34+ and 6-integrin or CD34+/CD49f+) in the isolated keratinocytes were determined by low cytometric analysis. Both single and chronic UVR treatments (1.8 kJ/m 2 ) resulted in an increase in the frequency of double positive HSCs in PKC TG mice as compared to their WT littermates. To determine the rate of proliferation of bulge region stem cells, a 5-bromo-2  -deoxyuridine labeling (BrdU) experiment was performed. In the WT mice, the percent of double positive HSCs retaining BrdU label was 28.4 ± 0.6% compared to 4.0 ± 0.06% for the TG mice, an approximately 7-fold decrease. A comparison of gene expression proiles of FACS sorted double positive HSCs showed increased expression of Pes1, Rad21, Tfdp1 and Cks1b genes in TG mice compared to WT mice. Also, PKC over expression in mice increased the clonogenicity of isolated keratinocytes, a property commonly ascribed to stem cells. 1. Introduction he multistage model of mouse skin carcinogenesis is a useful system in which biochemical events unique to initiation, pro- motion, or progression steps of carcinogenesis can be studied and related to cancer formation. 12-O-Tetradecanoylphorbol- 13-acetate (TPA), a component of croton oil, is a potent mouse skin tumor promoter [1, 2]. A major breakthrough in understanding the mechanism of TPA tumor promotion has been the identiication of protein kinase C (PKC), as its major intracellular receptor [3]. PKC forms part of the signal transduction system involving the turnover of inositol phospholipids and is activated by DAG, which is produced as a consequence of this turnover [3]. PKC represents a family of phospholipid-dependent serine/threonine kinases [3–6]. PKC is among the six PKC isoforms (, , , , , and ) expressed in both mouse and human skin [7]. We have reported that epidermal PKC levels dictate the susceptibility of PKC transgenic (TG) mice to the devel- opment of squamous cell carcinomas (SCC) elicited either by repeated exposures to ultraviolet radiation (UVR) [8] or initiation with 7, 12-dimethylbenz[a]anthracene (DMBA) and tumor promotion with 12-O-tetradecanoylphorbol-13- acetate (TPA) [9]. Histologically, SCC in TG mice, like human SCC, is poorly diferentiated and metastatic [10].