Tumor necrosis factor mutants with selective cytotoxic activity

Tumor necrosis factor (TNF-alpha) has a cytotoxic or cytostatic effect when tested with various malignant cell lines. Clinical trials in cancer patien ts, however, revealed high systemic toxicity of TNF-alpha. The existence of two types of receptor may partially explain the pleiotropic activity of TN F-alpha. The purpose of this study was to characterize the relative cytotox ic activity of TNF-alpha and TNF mutants on the mouse fibrosarcoma L-929 ce lls in a standard cytotoxicity test, on human larynx carcinoma HEp-2 cells, and on human monoblastoid leukemic cells U937. TNF mutants were obtained b y site-directed mutagenesis. The purity of TNF-alpha was established by cap illary electrophoresis. TNF-alpha and TNF mutants were analysed by Western blot analysis using monoclonal antibodies against TNF-alpha. The results sh ow that TNF mutants can recognize the different TNF-receptors (TNF-R) selec tivity. It is generally believed that activation of TNF-R75 is responsible for the systemic toxicity of TNF-alpha. Hence, the development of TNF mutan ts, binding selectively to TNF-R55, could lead to new option for an antican cer treatment that would be devoid of the deleterious effect of TNF-alpha.