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Cancer Lett. 2001 Oct 10;171(2):165-72.

Enhanced IkappaB kinase activity is responsible for the augmented activity of NF-kappaB in human head and neck carcinoma cells.

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Second Department of Oral and Maxillofacial Surgery, Tokushima University School of Dentistry, 3-18-15 Kuramoto-cho, Tokushima 770-8504, Japan.


The nuclear transcription factor kappaB (NF-kappaB) plays an important role in the development and progression of cancers. However, the mechanism by which cancer cells in the head and neck region acquire high NF-kappaB activity has not yet been clarified. In this study, we examined the NF-kappaB binding activity and the expression of the signal-transduction-related proteins of NF-kappaB in head and neck carcinoma cell lines. These cancer cells showed significantly higher NF-kappaB binding activity than normal oral epithelial and salivary gland cells. We also demonstrated the increased phosphorylation and degradation of IkappaB-alpha protein in cancer cells. Thus, enhanced NF-kappaB activity in cancer cells is attributable to the rapid phosphorylation and degradation of IkappaB-alpha protein. To further elucidate the mechanism involved in this phenomenon, we analyzed both the expression levels of upstream kinases (IkappaB kinase- (IKK-) alpha, IKK-beta, IKK-gamma, and NF-kappaB-inducing kinase (NIK)) and the IKK activity in cells. Although there was no significant difference in the expression levels of NIK, IKK-beta, or IKK-gamma in cancer cell lines compared to those in normal cells, increased expression of IKK-alpha protein was observed in cancer cells. In addition, IKK activity was significantly augmented in cancer cells as compared to normal cells. Thus, our results suggest that enhanced NF-kappaB activity in head and neck cancer cells may be due to the augmentation of IKK activity.

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