Evidence for partial exocrine acinar differentiation in experimentally induced pancreatic ductal/ductular cell tumors.

The pancreatic carcinomas induced in Syrian hamsters by a nitroso compound are of a ductal/ductular cell type. Electron microscopic examination of such tumors has revealed the presence of an occasional isolated acinar cell within the tumor. Based on their cellular characteristics, these acinar cells seem to have derived from ductular cell precursors. When we used a monoclonal antibody which specifically recognizes hamster acinar cells, a larger number of cells bearing acinar cell membrane markers were found in many tumors by an indirect immunofluorescence technique. Since most of these positively reacting cells did not exhibit the characteristic cytological features of acinar cells, such as rough endoplasmic reticulum and zymogen granules, differentiation of precursor cells to acinar cells may possibly occur at the cell membrane level. The presence of a few acinar cells within exocrine pancreatic tumors implies that acinar differentiation or retrodifferentiation can occur in pancreatic neoplasms.