United States-Japan workshop on new rodent models for the analysis and prevention of carcinogenesis

In assessing the present status of rodent models for the analysis and prevention of carcinogenesis, the discussion emphasized that models exist for very few of the major cancers occurring in the United States and Japan. Almost without exception, those that do exist were invented for etiological and mechanistic studies of chemical and physical carcinogenesis. Applicability to cancer chemoprevention was not a primary objective in their development. However, they have been adapted and used for identifying and characterizing chemopreventive agents out of necessity. It is therefore not surprising that they generally fail to fulfill most or all of the requisites of 'ideal' models enumerated above, and consequently, the validity of data produced through their use has been questioned. Evolution of future mechanistic models may similarly lead to their eventual adaptation to chemoprevention, but advances will be fragmentary, and the rate of progress seems likely to be slow. Animal models discussed at this workshop were designed specifically for this purpose and promise to expedite the accumulation of valuable new information. Nonetheless, recurrent discussion identified the urgent need for institution of a major, dedicated research initiative with the expressed objective of developing rodent models for organ-specific chemoprevention based on current understanding of underlying genetic and cellular processes. No concerted programs with this objective presently exist either in the United States or Japan. In addition to research specifically designed to meet this need, efforts should be made to involve investigators developing mechanistic animal models in the validation of their models through modulating cancer development by chemopreventive agents. Support for such research initiatives will be essential to continued progress toward the overall objective of identifying safe and effective cancer chemopreventive agents.