A Soluble 17 kDa Tumour Necrosis Factor (TNF) Mutein, TNF-SAM2, with Membrane-bound TNF-like Biological Characteristics

Abstract

Background: Membrane-bound tumour necrosis factor (TNF) has a different binding affinity to two TNF receptors (TNFR1 and TNFR2) and shows different biological activities compared with TNF-α. We have developed a mutein, TNF-SAM2, which has modified TNF-α. It has higher tumour killing activity than TNF-α and fewer side effects. Materials and Methods: The difference between TNF-SAM2 and TNF-α was examined in view of the binding affinity to each TNF receptor, cytotoxicity and expression of genes using Colo205 cells. Results: The KD value of TNF-α (2.9×10^-7 M) for TNFR1 was lower than TNF-SAM2 (6.9×10^-7 M). Cytotoxicity of TNF-SAM2 was significantly higher than for TNF-α. RNA of Colo205 cells stimulated with TNF-SAM2 indicated that 80 genes increased by a factor of 2 or more, and 69 genes decreased. Conclusion: TNF-SAM2 can induce different intracellular signal transduction in Colo205 cells compared with TNF-α. TNF-SAM2 may have characteristics of the membrane-bound form despite the fact that is in a soluble form.