Epidermal p65/NF-κB signalling is essential for skin carcinogenesis.
Bottom Line: In particular in epidermal keratinocytes, NF-κB signalling was reported to exert primarily growth inhibitory and tumour-suppressing functions.Here, we show that mice with keratinocyte-restricted p65/RelA deficiency were resistant to 7, 12-dimethylbenz(a)anthracene (DMBA)-/12-O-tetra decanoylphorbol-13 acetate (TPA)-induced skin carcinogenesis. p65 deficiency sensitized epidermal keratinocytes to DNA damage-induced death in vivo and in vitro, suggesting that inhibition of p65-dependent prosurvival functions prevented tumour initiation by facilitating the elimination of cells carrying damaged DNA.In addition, lack of p65 strongly inhibited TPA-induced epidermal hyperplasia and skin inflammation by suppressing the expression of proinflammatory cytokines and chemokines by epidermal keratinocytes.
Affiliation: Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Centre for Molecular Medicine (CMMC), University of Cologne, Cologne, Germany.Show MeSH
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Mentions: We generated mice with specific deletion of the p65 gene in epidermal keratinocytes (p65EKO) by crossing mice carrying p65 floxed (p65FL) alleles (Luedde et al, 2008) with K14-Cre transgenic mice expressing Cre recombinase under the control of the keratin-14 (K14) promoter (Hafner et al, 2004). p65EKO mice were born at Mendelian ratio and reached adulthood without showing apparent abnormalities. Immunoblot analysis of epidermal protein extracts showed that p65 was efficiently ablated in the epidermis of p65EKO mice (Fig 1A). Interestingly, the loss of p65 resulted in decreased expression of the RelB and c-Rel NF-κB subunits, consistent with the notion that they are transcriptionally regulated by NF-κB (Hannink & Temin, 1990; Bren et al, 2001). Immunohistological analysis of skin sections from p65EKO mice showed a normal epidermal–dermal organization and a normally differentiated stratified epidermis (Fig 1B). Therefore, as shown previously by Rebholz et al (2007) keratinocyte-specific p65 deficiency did not affect the development and differentiation of the epidermis, in contrast to a previous report that showed that skin grafts from p65-deficient embryos developed epidermal hyperplasia and suggested that p65 regulates normal epidermal proliferation and differentiation (Zhang et al, 2004).
Affiliation: Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Centre for Molecular Medicine (CMMC), University of Cologne, Cologne, Germany.