Research in
cancer chemoprevention involves a number of activities, the first and foremost of which is acquisition of detailed knowledge concerning the process of
carcinogenesis and identification of points of intervention whereby the process can be reversed or stalled. Parallel to this is the search for ideal chemopreventive agents--natural or synthetic--and screening for their activity and efficacy in vitro and in vivo. For ethical reasons it is not possible to test new agents on humans, so preclinical studies are dependent on results first being obtained with suitable animal models. Since it is not possible for a single model to reflect the diversity and heterogeneity of human
cancers, it is necessary to have as many different models as possible, depending on the requirement of the studies on different aspects of
cancer biology. Advances in research on
carcinogenesis and
chemoprevention therefore have to be accompanied by development of appropriate laboratory animal models using a variety of
carcinogens that produce tumours at different sites. Animal models have contributed significantly to our understanding of
carcinogenesis and ways to intervene in the underlying processes. Many animal
carcinogenesis and tumour models have been found to mirror corresponding human
cancers with respect to cell of origin, morphogenesis, phenotype markers and genetic alteration. In spite of the fact that interpolation of data from animal studies to humans is difficult for various reasons, animal models are widely used for assessment of new compounds with
cancer chemopreventive potential and for preclinical trials. So despite the movements of animal rights activists, animal models will continue to be used for biomedical research for saving human lives. In doing so, care should be taken to treat and handle the animals with minimal discomfort to them and ensuring that alternatives are used whenever possible.