TGF-β and NF-κB signal pathway cross-talk is mediated through TAK1 and SMAD7 in a subset of head and neck cancers.
Transforming growth factor-beta (TGF-β) has a dual role in epithelial malignancies, including head and neck squamous cell carcinoma (HNSCC). Attenuation of canonical TGF-β signaling enhances de novo tumor development, whereas TGF-β overexpression and signaling paradoxically promotes malignant progression. We recently observed that TGF-β-induced growth arrest response is attenuated, in association with aberrant activation of nuclear factor-κB (NF-κB), a transcription factor, which promotes malignant progression in HNSCC. However, what role cross-talk between components of the TGF-β and NF-κB pathways plays in altered activation of these pathways has not been established. Here, we show TGF-β receptor II and TGF-β-activated kinase 1 (TAK1) are predominantly expressed in a subset of HNSCC tumors with nuclear activation of NF-κB family member RELA (p65). Further, TGF-β1 treatment induced sequential phosphorylation of TAK1, IKK, IκBα and RELA in human HNSCC lines. TAK1 enhances TGF-β-induced NF-κB activation, as TAK1 siRNA knockdown decreased TGF-β1-induced phosphorylation of IKK, IκB and RELA, degradation of IκBα, RELA nuclear translocation and DNA binding, and NF-κB-induced reporter and target gene transcription. Functionally, TAK1 siRNA inhibited cell proliferation, migration and invasion. Celastrol, a TAK1 inhibitor and anti-inflammatory compound used in traditional Chinese medicine, also decreased TGF-β1-induced phosphorylation of TAK1 and RELA, and suppressed basal, TGF-β1- and tumor necrosis factor-alpha (TNF-α)-induced NF-κB reporter gene activity. Celastrol also inhibited cell proliferation, while increasing sub-G0 DNA fragmentation and Annexin V markers of apoptosis. Furthermore, TGF-β and RELA activation promoted SMAD7 expression. In turn, SMAD7 preferentially suppressed TGF-β-induced SMAD and NF-κB reporters when compared with constitutive or TNF-α-induced NF-κB reporter gene activation. Thus, cross-talk by TGF-β via TAK1 and NF-κB promotes the malignant phenotype of HNSCC. Moreover, NF-κB may contribute to the downstream attenuation of canonical TGF-β signaling through increased SMAD7 expression. Celastrol highlights the therapeutic potential of agents targeting TAK1 as a key node in this pro-oncogenic TGF-β-NF-κB signal pathway.
Tumor Biology Section, Head and Neck Surgery Branch, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892-1419, USA.
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Freudlsperger
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Bian
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Contag Wise
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Burnett
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Coupar
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Yang
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Chen
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C
Van Waes
D002294:Carcinoma, Squamous Cell / Q000209:etiology* / Q000473:pathology; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D006258:Head and Neck Neoplasms / Q000209:etiology* / Q000473:pathology; D006801:Humans; D020930:MAP Kinase Kinase Kinases / Q000502:physiology*; D016328:NF-kappa B / Q000502:physiology*; D009361:Neoplasm Invasiveness; D015398:Signal Transduction / Q000502:physiology*; D051906:Smad7 Protein / Q000502:physiology*; D000077195:Squamous Cell Carcinoma of Head and Neck; D051996:Transcription Factor RelA / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000502:physiology*; D000099151:MAP Kinase Kinase Kinase 7
D020930:MAP Kinase Kinase Kinases; D016328:NF-kappa B; D051906:Smad7 Protein; D051996:Transcription Factor RelA; D016212:Transforming Growth Factor beta; D000099151:MAP Kinase Kinase Kinase 7; C498143:RELA protein, human; C497806:SMAD7 protein, human