C-type virus particles in urethan-induced pulmonary and renal carcinomas, in cell-graft-transmitted carcinosarcomas, and in filtrate-induced lymphomas in mice.

Repeated injections of urethan into suckling BALB/c mice induced multiple papillary adenocarcinomas in the lungs and kidneys. When the pulmonary tumors were transplanted i.p. by cell graft into 6 suckling BALB/c mice, they induced disseminated carcinosarcomas within the peritoneal cavity in all inoculated animals. Tumors resulting from the transplantation of tumor cells were used for preparation of filtered extracts. The filtrates were inoculated into 6 suckling BALB/c mice and induced generalized malignant lymphomas in all animals. The primary urethan-induced pulmonary and renal tumors, the carcinosarcomas that resulted from i.p. cell transfer, and also the generalized malignant lymphomas induced by inoculation of filtered extracts contained C-type virus particles. Theoretically, it could be assumed that both the primary urethan-induced pulmonary and renal tumors, as well as the cell-graft-induced peritoneal carcinosarcomas, contained the C-type virus particles as passengers, not necessarily related etiologically to the tumors in which they were found. It is quite likely, however, that these virus particles were etiologically related to the filtrate-induced malignant lymphomas in which they were also found.