Lymphotoxin: an anticarcinogenic lymphokine as measured by inhibition of chemical carcinogen or ultraviolet-irradiation-induced transformation of Syrian hamster cells.

Syrian-hamster-derived lymphotoxin inhibits benzo(a)pyrene and ultraviolet carcinogen-induced in vitro morphologic transformation of diploid secondary passage hamster embryo cells. When lymphotoxin is added up to 4 days post carcinogen, the reduction in the frequency of morphologic transformation 6 days after carcinogen treatment varies directly with lymphotoxin concentration. The frequency of transformation does not change following re-feeding with lymphotoxin-free medium and incubation for 6 additional days. Furthermore, transformation by ultraviolet is prevented when cells are pulsed with lymphotoxin for as few as 6 hours after irradiation. Thus, lymphotoxin has the potential to irreversibly inhibit the first recognizable morphologic step of carcinogenesis.