Fate of intravenously injected rat ascites hepatoma cells in the lung of congenitally athymic mice.

Formation of hematogenous metastasis in the congenitally athymic nude mice (nu/nu) and their heterozygous ones (nu/+) was compared 2 weeks after an intravenous injection of xenogeneic tumor cells of rat ascites hepatoma cells (AH 130) with high thromboplastic activity. AH 130 cells formed large numbers of metastatic foci in the lungs of nu/nu recipients, while they developed into only temporary growth of metastatic foci with subsequent regression in nu/+ mice. Cellular reaction to arrested tumor cells in the pulmonary vessels was composed of large mononuclear cells, and was extensive and prominent in nu+/mice in comparison with nu/nu mice 3 days after the injection of the tumor cells. The results suggest that mononuclear cells reaction is closely related to suppression of growth of micrometastasis. This is considered as a model that highly immunogenic tumor cells attenuated and could be rejected in relation to immunological mechanisms.