A mutein, F4168, of human tumor necrosis factor alpha (hTNF-alpha) containing the cell-adhesive Arg-Gly-Asp (RGD) sequence near the N terminus was constructed. In contrast to hTNF-alpha, the mutein had binding activity to B16F10/L5 melanoma cells similar to that of fibronectin or laminin, indicating that the adhesive nature of the RGD sequence is conferred upon hTNF-alpha. Introduction of the RGD sequence did not alter the antitumor potential of hTNF-alpha. Simultaneous injection of F4168 and B16F10/L5 melanoma cells into mice did not enhance metastasis formation in lungs, whereas hTNF-alpha significantly promoted it. Enhancement of spontaneous lymph node metastasis of B16F10/L5 cells was also evident in TNF-alpha- but not in F4168-treated mice. In the spontaneous lymph node metastasis model of MethA fibrosarcoma, F4168 injection inhibited metastasis formation more effectively than hTNF-alpha. B16F10/L5 melanoma cells treated with hTNF-alpha enhanced not only their binding activity to laminin but also their invasive potential into Matrigel, whereas F4168 showed no such enhancement. These results suggest that F4168 is a low-toxicity mutein of hTNF-alpha.