Fig. 2. Effects of UVB on COX-2 and cytokine mRNA expression Fig. 2. Effects of UVB on COX-2 and cytokine mRNA expression. Undifferentiated and differentiated keratinocytes were exposed to UVB (2.5–25 mJ/cm <sup>2</sup> ) or control. After 24 h, RNA was extracted from the cells and analyzed for gene expression by real-time PCR ( n = 3–6, ±SE). Data are presented as fold increase in gene expression relative to unexposed undifferentiated cells. Differences were considered statistically significant at P < 0.05: <sup>a</sup> undifferentiated fold increase as compared with control; <sup>b</sup> differentiated fold increase versus control; <sup>c</sup> undifferentiated versus differentiated. From: Distinct effects of ultraviolet B light on antioxidant expression in undifferentiated and differentiated mouse keratinocytes Carcinogenesis. 2007;29(1):219-225. doi:10.1093/carcin/bgm242 Carcinogenesis | © The Author 2007. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org 1