P53+/- hemizygous knockout mouse: overview of available data

Area of Science:

• Toxicology
• Genetics
• Carcinogenesis

Background:

• The p53 gene plays a crucial role in tumor suppression.
• Evaluating alternative models for carcinogenicity testing is essential for reducing animal use and improving efficiency.
• The International Life Sciences Institute's (ILSI) Alternatives to Carcinogenicity Testing (ACT) project aimed to validate new testing strategies.

Purpose of the Study:

• To assess the performance of the p53-/- transgenic (knockout) mouse model in carcinogenicity testing.
• To evaluate the model's concordance with known genotoxic and non-genotoxic carcinogens and non-carcinogens.
• To identify technical lessons learned from using the p53 knockout model in short-term carcinogenicity studies.

Main Methods:

• Review of data from 31 short-term carcinogenicity studies involving 21 compounds.
• Testing conducted as part of the ILSI ACT project and comparable studies.
• Analysis of results for genotoxic and non-genotoxic carcinogens, including positive and negative controls.

Main Results:

• The p53 knockout model correctly identified 75% (12/16) of genotoxic carcinogens.
• The model showed no false positives for 22 non-genotoxic rodent carcinogens.
• Overall, 88% (42/48) of compounds yielded results concordant with expectations, excluding equivocal results.

Conclusions:

• The p53 knockout mouse model demonstrates significant potential as a tool for carcinogenicity testing.
• The model's performance aligns well with the hypothesis, particularly for genotoxic carcinogens.
• Further technical evaluation is warranted based on the lessons learned from ILSI ACT-sponsored testing.