Abstract
A tumor model was developed in DBA/2 mice for studying the progression of the mastocytoma P 815 X 2 tumor. Tumor cells obtained from ascites were grown in vitro. The number of cells derived from a single clone was increased by in vitro culture. Cells were then injected either i.v. or i.p. into DBA/2 mice. Large volumes of tumor ascites were observed after i.p. but not i.v. injection. The latter led to tumor growth at multiple sites, especially in the liver. Mastocytoma cells were released from liver tissue and then injected i.p. into other recipients. For cloning of liver invading tumor cells, this procedure was repeated for greater than 20 generations of mice. Tumor infiltration of the liver increased strongly during this period, but ascites volume clearly decreased.