Expression of a mutant p53 results in an age-related demographic shift in spontaneous lung tumor formation in transgenic mice.
BACKGROUND
Mutations in the P53 gene are among the most common genetic abnormalities in human lung cancer. Codon 273 in the sequence-specific DNA binding domain is one of the most frequently mutated sites.


METHODS
To investigate the role of mutant p53 in lung tumorigenesis, a lung specific p53(273H) transgenic mouse model was developed. Rates of lung cancer formation in the transgenic animals and their littermates were evaluated by necropsy studies performed in progressive age cohorts ranging from 4 to 24 months. In order to establish the influence of other common genetic abnormalities in lung tumor formation in the animals, K-Ras gene mutation and p16INK4a (p16) promoter methylation were evaluated in a total of 281 transgenic mice and 189 non-transgenic littermates.


RESULTS
At the age extremes of 4-12 and 22-24 months no differences were observed, with very low prevalence of tumors in animals younger than 12 months, and a relatively high prevalence at age 22 months or older. However, the transgenic mice had a significant higher lung tumor rate than their non-transgenic counterparts during the age of 13-21 months, suggesting an age-related shift in lung tumor formation induced by the lung-specific expression of the human mutant p53. Histopathology suggested a more aggressive nature for the transgenic tumors. Older mice (>13 months) had a significantly higher rate of p16 promoter methylation (17% v 82%). In addition, an age related effect was observed for K-Ras codons 12 or 13 mutations, but not for codon 61 mutations.


CONCLUSIONS
These results would suggest that the mutant p53(273H) contributes to an acceleration in the development of spontaneous lung tumors in these mice. Combination with other genetic and epigenetic alterations occurring after the age of 13 months is intimately linked to its oncogenic potential.
Comprehensive Cancer Center, The Ohio State University College of Medicine and Public Health, Columbus, Ohio, United States of America.
Wenrui
W
Duan
Li
L
Gao
Xin
X
Wu
Erinn M
EM
Hade
Jian-Xin
JX
Gao
Haiming
H
Ding
Sanford H
SH
Barsky
Gregory A
GA
Otterson
Miguel A
MA
Villalona-Calero
D000375:Aging / Q000502:physiology*; D000818:Animals; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology; D049109:Cell Proliferation; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics; D019175:DNA Methylation; D005786:Gene Expression Regulation; D011905:Genes, ras / Q000235:genetics; D007150:Immunohistochemistry; D008175:Lung Neoplasms / Q000235:genetics* / Q000473:pathology; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation / Q000235:genetics / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
D019941:Cyclin-Dependent Kinase Inhibitor p16; D016159:Tumor Suppressor Protein p53