An inducible mouse model for skin cancer reveals distinct roles for gain- and loss-of-function p53 mutations
Carlos Caulin, … , Guillermina Lozano, Dennis R. Roop
Carlos Caulin, … , Guillermina Lozano, Dennis R. Roop
Published July 2, 2007
Citation Information: J Clin Invest. 2007;117(7):1893-1901. https://doi.org/10.1172/JCI31721.
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Research Article

An inducible mouse model for skin cancer reveals distinct roles for gain- and loss-of-function p53 mutations

Abstract

Mutations in ras and p53 are the most prevalent mutations found in human nonmelanoma skin cancers. Although some p53 mutations cause a loss of function, most result in expression of altered forms of p53, which may exhibit gain-of-function properties. Therefore, understanding the consequences of acquiring p53 gain-of-function versus loss-of-function mutations is critical for the generation of effective therapies for tumors harboring p53 mutations. Here we describe an inducible mouse model in which skin tumor formation is initiated by activation of an endogenous K-rasG12D allele. Using this model we compared the consequences of activating the p53 gain-of-function mutation p53R172H and of deleting the p53 gene. Activation of the p53R172H allele resulted in increased skin tumor formation, accelerated tumor progression, and induction of metastasis compared with deletion of p53. Consistent with these observations, the p53R172H tumors exhibited aneuploidy associated with centrosome amplification, which may underlie the mechanism by which p53R172H exerts its oncogenic properties. These results clearly demonstrate that p53 gain-of-function mutations confer poorer prognosis than loss of p53 during skin carcinogenesis and have important implications for the future design of therapies for tumors that exhibit p53 gain-of-function mutations.

Authors

Carlos Caulin, Thao Nguyen, Gene A. Lang, Thea M. Goepfert, Bill R. Brinkley, Wei-Wen Cai, Guillermina Lozano, Dennis R. Roop

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Figure 2

Activation of the p53R172H allele contributes to tumor initiation and malignant progression of skin tumors.

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Activation of the p53R172H allele contributes to tumor initiation and ma...
(A) Schematic representation of the neo-p53R172H allele showing exons 4 and 5, the presence of the neo cassette in intron 4, and primers R172H reverse and R172H forward (PM1 and PM2, respectively; see Methods), which were used for PCR analysis of the p53 allele. The neo cassette prevents expression of the p53R172H allele (C. Caulin, D.R. Roop, and G. Lozano, unpublished observations). Asterisks indicate mutation in exon 5 for p53R172H. (B) Schematic representation of the p53f allele showing loxP sites in introns 1 and 10 and primers PF1 and PF2 (26) that were used to analyze deletion of exons 2–10. (C) Kinetics of tumor formation in K-ras–p53R172H/WT mice (K-p53R172H/WT; n = 22) and K-ras–p53f/WT mice (K-p53f/WT; n = 21). K-ras–p53WT/WT mice (K-p53WT/WT; n = 17) were used as controls. Tumor formation was evaluated by the average number of tumors developed per mouse after the initial treatment with TPA. (D) Kinetics of carcinoma formation. Each time point represents percentage of mice bearing carcinomas. (E) Kinetics of tumor formation in K-ras–p53R172H/f mice (K-p53R172H/f; n = 16) and K-ras–p53f/f mice (K-p53f/f; n = 22). (F) Kinetics of carcinoma formation in K-ras–p53R172H/f and K-ras–p53f/f mice. (G) Activation of the p53R172H, p53f, and K-rasG12D alleles in papillomas and carcinomas. Primers PM1 and PM2 were used to analyze activation of the p53R172H allele. Primers PF1 and PF2 were used to analyze deletion of the loxP-flanked sequences in the p53f allele. Primers P1 and P2 were used to analyze activation of the K-rasG12D allele. DNA purified from spleen (Sp; lane 16) of a K-ras–p53R172H/WT mouse was used as a control and only generated the band corresponding to p53WT or K-rasWT alleles.