CYTOTOXIC EFFECT OF A HYBRID PROTEIN INTERFE RON γ/TUMOR NECROSIS FACTOR β ON INTERFERON γRESISTANT CELL LINES IN VITRO
Previous observations indicated that a hybrid protein composed of IFNγ and TNFβ( γTNFβ ) showed enhanced anticellular activity com pared to either of the two lymphokines alone on a human cervical carcinoma cell line ME180. We report here that this hybrid protein exerted significant, though lowered, cytotoxicity on three IFNγ resistant mutants derived from the ME180 cell line. When the cells were treated with γTNFβ, IFNrγ or TNFβ for 72 and 30hr, the IFNγ resistant mutants as well as the wild type ME180 showed significantly higher sensitivity to the killing effect of γTNFβ than that of IFNrγ or TNFbβ. This result suggests that the artificial hybrid protein may be more effective than IFNγ in the treatment of cancer patients with tumors resistant to this lymphokine.