Demonstration of type-R and type-C virus particles in hamster pancreatic adenocarcinomas

Two transplantable solid tumors (CBP and PDP) and two continuous cultured cell lines (CBP-TC and PDP-TC) were established from nitrosamine-induced pancreatic ductal adenocarcinomas in inbred Syrian hamsters. Electron microscopic examination of both CBP and PDP solid tumors as well as CBP-TC cultured cells revealed the presence of type-R virus particles, which consisted of a 100 nm envelope containing a central 50 nm nucleoid with characteristic radiating 'spokes'. Type-R particles were abundant in cultured CBP-TC cells, moderately frequent in CBP solid tumors, and rare in PDP solid tumors; they were not present in PDP-TC cultured cells. The CBP and PDP solid tumors and cultured PDP-TC cells exhibited type-C viral particles, having a 150 nm envelope containing a 75 nm nucleoid. Mature, immature and budding forms of Type-C viruses were present and quite prominent in PDP tumors. Type-C particles were present but rare in CBP solid tumors and in PDP-TC cells. C-particles were not observed in cultured CBP-TC cells. Examination of normal hamster pancreas, liver, duodenum, muscle and connective tissue failed to reveal evidence of type-R or type-C virus particles. It is important to recognize the presence of virus particles in hamster pancreatic carcinoma lines, since viruses could potentially affect biochemical or immunological studies on the carcinomas through the production of viral proteins that could be mistaken for tumor-associated antigens.