Aberrant IKK? and IKK? cooperatively activate NF-?B and induce EGFR/AP1 signaling to promote survival and migration of head and neck cancer.

ABSTRACT: The inhibitor-?B kinase-nuclear factor-?B (IKK-NF-?B) and epidermal growth factor receptor-activator protein-1 (EGFR-AP1) pathways are often co-activated and promote malignant behavior, but the underlying basis for this relationship is unclear. Resistance to inhibitors of IKK? or EGFR is observed in head and neck squamous cell carcinomas (HNSCC). Here, we reveal that both IKK? and ? contribute to nuclear activation of canonical and alternate NF-?B/REL family transcription factors, and overexpression of signal components that enhance co-activation of the EGFR-AP1 pathway. We observed that IKK? and IKK? exhibit increased protein expression, nuclear localization, and phosphorylation in HNSCC tissues and cell lines. Individually, IKK activity varied among different cell lines, but overexpression of both IKKs induced the strongest NF-?B activation. Conversely, siRNA knock down of both IKKs significantly decreased nuclear localization and phosphorylation of canonical RELA and I?B? and alternative p52 and RELB subunits. Knock down of both IKKs more effectively inhibited NF-?B activation, broadly modulated gene expression and suppressed cell proliferation and migration. Global expression profiling revealed that NF-?B, cytokine, inflammatory response and growth factor signaling are among the top pathways and networks regulated by IKKs. Importantly, IKK? and IKK? together promoted the expression and activity of transforming growth factor ?, EGFR and AP1 transcription factors cJun, JunB and Fra1. Knock down of AP1 subunits individually decreased 8/15 (53%) of IKK-targeted genes sampled and similarly inhibited cell proliferation and migration. Mutations of NF-?B and AP1-binding sites abolished or decreased IKK-induced interleukin-8 (IL-8) promoter activity. Compounds such as wedelactone with dual IKK inhibitory activity and geldanomycins that block IKK?/? and EGFR pathways were more active than IKK?-specific inhibitors in suppressing NF-?B activation and proliferation and inducing cell death. We conclude that IKK? and IKK? cooperatively activate NF-?B and EGFR/AP1 networks of signaling pathways and contribute to the malignant phenotype and the intrinsic or acquired therapeutic resistance of HNSCC.

SUBMITTER: Nottingham LK 

PROVIDER: S-EPMC3926900 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature