Udp-galnac:fUcα1-2galα1-3galnac transferase activity in hamster pancreatic cancers and in normal hamster alimentary tissues

Ductal adenocarcinomas induced by N-nitrosobis(2-oxopropyl)amine treatment in Syrian hamsters produce blood group-A antigen, which is not present in normal hamster pancreas. To understand the underlying mechanism of A antigen neoexpression in pancreatic cancer cells, we examined the activity of UDP-GalNAc: Fucα1-2Galα1-3GalNAc transferase (A-transferase), the enzyme responsible for blood group-A antigen production. The specific activity of A-transferase in the pancreatic cancers was ∼8 nmol/mg protein/h in membrane preparations, 0.3 nmol/mg protein/h in whole cell extracts, and undetectable in normal hamster pancreas. Significant A-transferase activity was found in normal tissues expressing blood group-A antigen. Although both normal (gastric antrum, colon) and pancreatic cancer cells showed similar enzymatic characteristics (optimal pH, substrate affinity, optimal [Mn²⁺]), there was a difference in the requirement for divalent cations. The A-transferase in cancer cells showed a more stringent requirement for Mn²⁺. These results suggest that A-transferase is activated during nitrosamine-induced pancreatic carcinogenesis, which results in the neoexpression of blood group-A antigen. The difference in divalent cation requirements between A-transferase activities of cancer and normal cells may indicate that there are multiple A-transferases present in hamster tissues.