Enhanced malignant phenotype of urethane-induced lung adenoma associated with sialoadenectomy in BALB/c mice.

Mouse lung adenoma were induced in adult female BALB/c mice by chronic i.p. urethane injection. Sialoadenectomy of the mice prior to carcinogen treatment did not alter the frequency or size of lung adenoma. However, sialoadenectomized mice exhibited a decrease in the proportion (18 versus 52%) of tumours which exhibited a low nuclear to cytoplasmic ratio and which grew along alveolar septa. Sialoadenectomy was also related to a complementary increase in the proportion (82 versus 48%) of tumours with large vesicular nuclei, prominent nucleoli and generally increased phenotypic features of malignancy. Replacement of epidermal growth factor (EGF) in sialoadenectomized mice restored the tumour-type ratio observed in non-sialoadenectomized mice. These data are discussed with respect to the possible roles of EGF in mouse lung alveologenic carcinoma formation and the cell type of origin for the tumours observed.