NTP workshop: Animal models for the NTP rodent cancer bioassay: Stocks and strains - Should we switch?

National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA.
Toxicologic Pathology (Impact Factor: 1.92). 02/2006; 34(6):802-5. DOI: 10.1080/01926230600935938
Source: PubMed

ABSTRACT The National Toxicology Program (NTP) hosted a workshop, "Animal Models for the NTP Rodent Cancer Bioassay: Strains and Stocks--Should We Switch?" on June 16-17, 2005, at the National Institute of Environmental Health Sciences (NIEHS) in Research Triangle Park, North Carolina. The workshop's objectives were to determine (1) whether the currently used models, the F344/N rat and B6C3F1/N mouse, continue to be appropriate to identify substances that may pose a carcinogenic hazard for humans and (2) whether the NTP should consider conducting cancer bioassays using multiple strains of rats and/or mice to better capture the range of genetic variability. Workshop participants advised the NTP to discontinue using the current F344/N strain due to the recent issues with fertility, seizure activity, and chylothorax and provided several options on how the program should approach identifying and selecting a new rat model. Participants believed that the B6C3F1/N mouse is still appropriate for use by the NTP, but suggested the NTP take steps to better understand and address increases in background rates of liver tumors in this strain. Finally, the participants supported the NTP exploring the use of the multiple strain approach, although they raised many questions concerning data interpretation and feasibility. This article also outlines the NTP's next steps in pursuing the workshop recommendations.

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    • "Sprague-Dawley (SD) rats are a common choice for regulatory toxicology studies, but recently the Wistar Han (WH) strain has been increasingly used. The growing popularity of the Wistar strain can be attributed to their reduced size, which requires less test material, as well as a higher survival rates (longer lifespan) and lower incidence of background tumors relative to the more traditionally used Sprague-Dawley strain, which make them more desirable for use in carcinogenicity studies [1]. In addition to these differences, there have also been anecdotal reports based on reproductive performance data that the male WH rat attains sexual maturity about 2 weeks later than the Sprague-Dawley strain. "
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