BACKGROUND: The main reason for the failure of anti-cancer chemotherapy is the acquisition build up of resistance of by cancer cells to apoptosis. The resistance of cancer cells to apoptosis has been reported to be due to the activation of NF-kappaB in many cancer cell lines. The activation of NF-kappaB in many cancer cell lines is reported to be underlying mechanism behind the build up of resistance of cancer cells to apoptosis. However, this relationship varied in according to varied depending on the cells used in the experiments. In this study, we evaluated the the role of NF-kappaB activation in the TNF-alpha-induced apoptosis in lung cancer cell line was evaluated. METHODS : NCI-H157 cells were used in all experiments. Cells were exposed to a high dose of TNF-alpha (20 ng/ml) for 24 or 48 hours with or without blocking NF-kappaB activation. TNF-alpha-induced activation of NF-kappaB was inhibited either by overexpression of I kappaB alpha-super repressor (I kappaB alpha-SR) or by pre-treatment with proteasome inhibitor. Cell viability and apoptosis were evaluated with MTT assay and Western blot analysis for PARP fragment(,) respectively. RESULTS: Cell viability of NCI-H157 cells was not affected by TNF-alpha treatment alone (;)however, combined treatment with TNF-alpha and cycloheximide reduced cell viability significantly(,) indicating that resistance to TNF-alpha is mediated by the new protein(s) synthesized after TNF-alpha stimulation. To evaluate the role of NF-kappaB in the transcription of anti-apoptotic protein(s), we inhibited(delete) NF-kappaB activation (was inhibited) before TNF-alpha stimulation(,) as described above. Ad5I kappaB alpha-SR-transduction inhibited TNF-alpha-induced nuclear translocation of p65. TNF-alpha-induced cell death and apoptosis increased after inhibition of TNF-alpha-induced activation of NF-kappaB by methods. CONCLUSION: These results suggest that TNF-alpha-induced activation of NF-kappaB may be closely related to the acquisition of the resistance to TNF-alpha-induced apoptosis in lung cancer cells. Therefore, blocking of NF-kappaB pathway can be a useful therapeutic modality in the treatment of lung cancer.