Abstract
Tumor necrosis factor-alpha (TNF), which was initially supposed to be a promising cancer therapeutic reagent, does not kill most types of cancer cells partly due to the activation of an anti-apoptotic gene, NF-kappaB. NF-kappaB forms an inactive complex with the inhibitor kappa B alpha (IkappaBalpha), which is rapidly phosphorylated and degraded in response to various extracellular signals. To disrupt this protective mechanism, we introduced an inhibitor kappa B alpha (IkappaBdN) gene, a deletion mutant gene lacking the nucleotides for the N-terminal 36 amino acids of IkappaBalpha, into human glioma cells (U251, T-98G, and U-373MG) via an adenoviral (Adv) vector in addition to treatment of the glioma cells with recombinant TNF. Immunohistochemical analysis revealed that NF-kappaB was translocated to nuclei by TNF treatment in U251 and T-98G cells, but not in U-373MG cells. Neither transduction of IkappaBdN nor treatment with TNF protein alone induced apoptosis in U251 and T-98G cells, whereas both cell lines underwent drastic TNF-induced apoptosis after transduction of IkappaBdN. On the other hand, U-373MG cells were refractory to TNF-induced apoptosis even when they were transduced with the IkappaBdN gene. U-373MG cells underwent drastically increased apoptosis when co-transduced with the IkappaBdN and Bax gene in the presence of TNF. Adv-mediated transfer of IkappaBdN or IkappaBdN plus Bax may be a promising therapeutic approach to treat gliomas through TNF-mediated apoptosis.