Complete and apparently specif local tumor regression using syngeneic or xenogeneic "tumor-immune" RNA extracts

Abstract

Syngeneic and xenogeneic RNA-rich extracts of lymphoid tissues were used in an immunotherapeutic regimen to treat strain 2 guinea pigs that were given intradermal injections of a uniformly lethal dose (1 x 10(6)) of line 10 diethylnitrosamine-induced transplantable hepatoma cells. When 1 X 10(7) syngeneic nonsensitive peritoneal exudate cells, 2.5 mg RNA from line 10-immune strain 2 guinea pigs or line 10-immune Rhesus monkeys, and 1.0 mg of a line-10 tumor-specific antigen preparation were injected s.c. under the tumor cells injected 5 days previously, complete local tumor regression in all treated animals was observed. If either nonsensitive peritoneal exudate cells, RNA, or line 10 tumor-specific antigen was omitted, or if Escherichia coli RNA or RNA from animals sensitized to a different tumor (line 1) was used, little or no tumor regression was observed, suggesting that the action of the RNA may have resulted in an antitumor response specific for the noplasm being treated. The long-term tumor-free survival of all treated animals indicates that the action of the RNA is systemic, since metastases are known to occur frequently by the time our therapeutic regimen was given. Also, in testing the biological activity of the "tumor-immune" RNA in the in vitro cell-migration-inhibition assay, both the syngeneic and xenogeneic RNA extracts could transfer tumor-specific immunological sensitivity, as demonstrated by the elaboration of migration-inhibitory factor by the RNA-treated nonsensitive peritonial exudate cells in the presence of the line 10 tumor-specific antigen.