The present invention is directed to the applications of a novel cytokine, named THANK, for TNF homologue that activates apoptosis, NF-.kappa.B and c-jun N-terminal kinase. Such applications include using THANK inhibitors to inhibit the activation of NF-.kappa.B and to treat a pathological condition caused by the activation of NF-.kappa.B. Also provided is a method of inhibiting growth of a wide variety of tumor cells by administering THANK protein.