Abstract
Four model systems for prostate adenocarcinomas have been developed in rats: they are designated Dunning, Noble, ACI, and Pollard tumors. They have attributes that make them valuable sources of information, of relevance to the disease in man. The development and use of the Pollard tumors as in vitro and in vivo model systems are reviewed, especially on the phenomenon of metastasis. Specific agents either accelerate or retard the rate and extent of metastatic spread of the prostate tumor cells from extravascular sites to specific target organs. Specific enzymes may be involved in the phenomenon of metastasis.