Transgenic animal models that might be useful in identifying unsuspected oncogenic factors in tumour cell substrates

The use of alternative short term models for the assessment of pharmaceutical carcinogenicity potential is expanding and evolving. Several mouse models of accelerated carcinogenesis have gained user confidence and are being applied to product development decision-making. These models have been highlighted as part of a consortium effort organized under ILSI to further evaluate their strengths and limitations compared to the standard two-years, two species cancer bioassay. Examples of trends that are developing in our understanding of applicability of these models to chemical carcinogenesis have been presented but a more comprehensive review of all the currently available data has been avoided. Such a review would be soon outdated as the anticipated data from the ILSI consortium studies will soon become available and greatly further impact our present appreciation of the capabilities of these models. As strengths and limitations of those models are being elucidated, mechanistic understanding of the models is expanding. In addition to those reviewed briefly in this paper, numerous other transgenic models with micro-injected oncogenes and disrupted tumour suppressor genes have demonstrated enhanced propensity for developing cancer. Critical experiments can be designed to test, conceptually, for the ability of any of these models to detect tumorigenic potential for a given dose of adventitious agent, or residual DNA sequence. The choice of model and of DNA sequence or adventitious agent to begin this evaluation must be carefully considered. From such data, risk may be better identified or prioritized, but such approaches may not be practical as general routine screens of finished vaccine product with unknown residual DNA sequence or adventitious agents.