TRANSPLACENTAL LUNG TUMORIGENESIS IN ATHYMIC MOUSE

Abstract

Female BALB/c nu/+ mice, pregnant by nu/+ males (nu: gene for hairlessness-athymia) were given injections of urethan, a transplacental tumorigen, on day 17 or 19 of gestation. After an average of 16 wk under clean conventional conditions, the incidence of primary lung tumors was similar in nude and normal offspring treated with carcinogen on either gestational day, with a higher incidence after treatment on day 19. The absence of thymus did not affect the occurrence of transplacentally induced primary lung tumors or alter the well-known perinatal increase in sensitivity. Histologically, the nu/nu tumors differed from normal in the appearance of many atypical basophilic cells and a tendency to invade the parenchyma and the pleural surface. These results suggested progression of the lung adenomas to a more atypical, invasive form, a progression that may have occurred prematurely in the absence of a thymus-dependent immune response.