Expression of PCNA, K10, and K5 in skin lesions from Stat3+/−:HPV8 and Stat3+/+:HPV8 mice. Expression of PCNA, K10, and K5 in skin lesions from Stat3+/−:HPV8 and Stat3+/+:HPV8 mice. Immunohistochemistry of serial sections of the skin specimens shown in Fig. 4A stained for PCNA, K10, and K5. Dark brown, positive cells; blue, nuclear counterstaining. Scale bars, 25 μm. The arrow indicates an island of K5-positive keratinocytes in the dermis. Marco De Andrea et al. Cancer Res 2010;70:7938-7948 ©2010 by American Association for Cancer Research