Constitutive activation of transcription factors NF-_κB, AP-1, and NF-IL6 in human head and neck squamous cell carcinoma cell lines that express pro-inflammatory and pro-angiogenic cytokines^†

We previously reported that human head and neck squamous cell carcinomas (HNSCCs) express the pro-inflammatory and pro-angiogenic cytokines interleukin (IL)-1α, IL-6, IL-8, and granulocyte-macrophage colony-stimulating factor in vitro and in vivo. The promoter region of the genes encoding these cytokines include binding sites for the transcription factors nuclear factor (NF) κB/Rel A, activator protein-1 (AP-1), and CCAAT enhancer-binding protein β (C/EBPβ, or NF-IL6), which have been reported to contribute to activation of these cytokine genes. In the study presented here, we examined the activation, composition, and function of these transcription factors in HNSCC cell lines that express pro-inflammatory cytokines, by using electrophoretic mobility shift and reporter-gene assays. Constitutive activation of NF-κB, AP-1, and NF-IL6 DNA-binding proteins was detected. Supershift analysis with antibodies specific for NF-κB, AP-1, and NF-IL6 binding proteins showed that the NF-κB–binding protein included p65/Rel A and p50; AP-1 activity included c-jun, junB, junD, and Fra-1; and NF-IL6 included C/EBPβ. Mutational analysis of the NF-κB, AP-1, and NF-IL6 sites in the IL-8 promoter region showed that NF-κB and AP-1 sites contributed to constitutive IL-8 reporter activity in HNSCC. HNSCC lines that exhibited increased IL-8 secretion relative to simian virus 40–immortalized and primary keratinocyte cell lines also demonstrated a concordant increase in NF-κB reporter activity relative to nonmalignant keratinocytes. We concluded that the early transcription factors NF-κB, AP-1, and NF-IL6 are constitutively activated in human HNSCC cell lines and that NF-κB and AP-1 promote expression of the pro-inflammatory and pro-angiogenic cytokine IL-8 in HNSCC. The demonstration of the activation of these transcription factors will be helpful in defining the identity and role of these and other early gene products that contribute to pathogenesis of the malignant phenotype in HNSCC and in defining potential targets for pharmacologic and molecular therapy of HNSCC. Mol. Carcinog. 26:119–129, 1999. Published 1999 Wiley-Liss, Inc.