Carcinogenesis by nitroso-2-hydroxyethylurea in splenectomized hamsters.

Several nitrosoalkylureas tested for carcinogenic activity in Syrian hamsters have as their main effect the induction of hemangiosarcomas of the spleen, many of which appear to metastasize to the liver. To investigate whether any of these lesions in the liver might not be metastases, a group of female Syrian hamsters was surgically splenectomized and treated with nitroso-2-hydroxyethylurea (NHEU) dissolved in corn oil/ethyl acetate once a week for 22 weeks. The animals survived much longer (median 45 weeks) than a comparable group of unsplenectomized female hamsters given identical treatment (median 24 weeks). The absence of hemangiosarcomas of the liver in the splenectomized hamsters showed that the presumed metastases seen in intact animals were, in fact, just that. A second interesting conclusion is that the compound did not produce a concomitant increase in tumors of other types.