In vitro pancreatic carcinogenesis

Studies in our laboratories have indicated that pancreatic cancer originate s not only from pancreatic ductal/ductular cells but also from within the L angerhans' islets, probably from reserve (precursor, stem) cells. To identi fy, enrich and characterize these cells, we established a long-term hamster islet culture and studied their growth, differentiation and response to th e pancreatic carcinogen, N-nitrosobis(2-oxopropyl)amine (BOF). One group of cultured islets was treated in vitro with BOP (KL5B group) and the other g roup of islets served as an untreated control (KL5N group). During the earl y culture days, in both groups all cultured islets showed a progressive los s of endocrine cells and replacement by ductular, acinar and intermediary c ells. However, all these cells disappeared after 35 days in culture and gav e room to undifferentiated cells, which we believe represent stem cells. No differences were found between KL5N and KL5B cells with regard to cell gro wth and differentiation until day 35, when the growth of the KL5B cells acc elerated and the cells underwent increasing pleomorphism and atypia. At day 133, KL5B cells but not KL5N cells showed colony formation in soft agar an d formed invasive, poorly differentiated adenocarcinomas of the ductal type when transplanted into hamsters. All of these tumors showed mutation of th e K-ms gene and extensive chromosomal damage. We concluded that like ductal /ductular cells, certain cell populations within islets are responsive to t he carcinogenic effect of BOP. We could not ascertain whether these cells p resent a preexisting (stem, reserve) cell population within the islets or t ransdifferentiated islet cells.