| Activation of NF-kappaB in Lung Cancer Cell Lines in Basal and TNF-alpha Stimulated States. |
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Bin Hwangbo, Seung Hee Lee, Choon Taek Lee, Chul Gyu Yoo, Sung Koo Han, Young Soo Shim, Young Whan Kim |
1Department of Internal Medicine, Seoul National University College of medicine, Seoul, Korea. ywkim@snu.ac.kr
2Lung Institute Seoul National University College of medicine, Seoul, Korea. |
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| Abstract |
BACKGROUND
The NF-kappaB transcription factors control various biological processes including the immune response, acute phase reastion and cell cycle regulation. NF-kappaB complexes are retained in the cytoplasm in the basal state and various stimuli cause a translocation of the NF-kappaB complexes into the nucleus where they bind to the kappaB elements and regulate the transcription of the target genes. Recent reports also suggest that NF-kappaB proteins are involved in oncogenesis, tumor growth and metastasis. High expression of NF-kappaB expression was reported in many cancer cell lines and tissues. The constitutive activation of NF-kappaB was also reported in several cancer cell lines supporting its role in cancer development and survival. The anti-apoptotic action of NF-kappaB is important for cancer survival. NF-kappaB also controls the expression of several proteins that are important for cellular adhesion (ICAM-1, VCAM-1) suggesting a role in cancer metastasis. In lung cancer, high expression levels of the NF-kappaB subunit p50 and c-Rel were reported. In fact, high expression does not mean a high activity, and the activation pattern of NF-kappaB in lung cancer has not been reported. METHODS: In this study, the NF-kappaB nuclear binding activity in the basal and TNF-alpha stimulated states were examined in various lung cancer cell lines and compared with the normal bronchial epithelial cell line. Twleve lung cancer cell lines including the non-small cell and small cell lung cancer cell lines (A549, NCL-H358, NCI-H441, NCL-H522, NCL-H2009, NCI-H460, NCI-H1229, NCI-H1703, NCL-H157, NCL-H187, NCI-H417, NCI-H526) and BEAS-2B bronchial epithelial cell line were used. To evaluate the NF-kappaB expression amd DNA binding activity, western blot analysis and an electrophoretic mobility shift assay with the nuclear protein extracts. RESULTS: The basal expressions of the p50 subunits were observed in the BEAS-2B cell line and all lung cancer cell lines except for NCI-H358 and NCI-H460. The expression levels of p65 and p50 were increased 30 minutes after stimulation with TNF- alpha in BEAS-2B and in 10 lung cancer cell lines. In the NCI-H358 and NCI-H460 cell lines, p65 expression was not observed in the basal and stimulated states and the two p50 related protein levels were higher after stimulation with TNF-alpha. These new proteins were smaller than p50 and are thought to be variants of p50. In the basal state, NF-kappaB was nearly activated in the BEAS-2B and all lung cancer cell lines. The DNA binding activity of the NF-kappaB complexes was markedly higher after stimulation with TNF-alpha. In the BEAS-2B and all lung cancer cell lines except for NCI-H358 and NCI-H460, the activated NF-kappaB complex was a p65/p60 heterodimer. In the NCI-H358 and NCI-H460 lung cancer cell lines, the NF-kappaB complex was variant of a p50/p50 homodimer. CONCLUSION: The NF-kappaB activation pattern in the lung cancer cell lines and the normal bronchial epithelial cell lines was similar except for the activatio of a variant of the p50/p50 homodimer in some lung cancer cell lines. |
| Key Words:
Lung cancer, NF-kappaB, A ctivation, p50, p65 |
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