The role of pancreatic islets in experimental pancreatic carcinogenicity.

Our previous studies have suggested that the presence of intact islets is essential for the induction of pancreatic exocrine tumors in the Syrian hamster model. To validate this, we investigated the effect of the carcinogen, N-nitrosobis(2-oxo-propyl)amine (BOP) in hamsters, in which homologous isolated intact islets were transplanted into the submandibular gland (SMG). Freshly isolated pure islets from hamster donors were transplanted into the left SMG of 20 female host hamsters. Ten of these hamsters (group 1) received BOP (40 mg/kg) weekly for 3 weeks. Another 10 hamsters (group 2) were kept untreated. In groups 3 and 4 (10 hamsters each) the salt solution or isolated pancreatic ductal cells, respectively, was injected into the gland. In other groups (10 hamsters each) islets were transplanted into the peri-SMG connective tissue (group 5) or into the renal subcapsular space (group 6). Hamsters of group 1 (40 mg/kg, weekly for 3 weeks) as were group 7 hamsters, which served as BOP-treated controls. All BOP-treated hamsters developed pancreatic lesions. Similar hyperplastic and atypical ductal/ductular proliferation and in situ carcinoma were found in the SMG of many group 1 hamsters. No such lesions were found in the SMG, peri-SMG, or renal subcapsular space of the other groups. Islets appear to be involved in carcinogenicity of BOP. The mechanism is obscure.