ΔNp63 Versatilely Regulates a Broad NF-κB Gene Program and Promotes Squamous Epithelial Proliferation, Migration, and Inflammation

Head and neck squamous cell carcinoma (HNSCC) and many other epithelial malignancies exhibit increased proliferation, invasion, and inflammation, concomitant with aberrant nuclear activation of TP53 and NF-kappa B family members Delta Np63, cRel, and RelA. However, the mechanisms of cross-talk by which these transcription factors coordinate gene expression and the malignant phenotype remain elusive. In this study, we showed that Delta Np63 regulates a cohort of genes involved in cell growth, survival, adhesion, and inflammation, which substantially overlaps with the NF-kappa B transcriptome. Delta Np63 with cRel and/or RelA are recruited to form novel binding complexes on p63 or NF-kappa B/Rel sites of multitarget gene promoters. Overexpressed Delta Np63- or TNF-alpha-induced NF-kappa B and inflammatory cytokine interleukin-8 (IL-8) reporter activation depended on RelA/cRel regulatory binding sites. Depletion of RelA or Delta Np63 by small interfering RNA (siRNA) significantly inhibited NF-kappa B-specific, or TNF-alpha-induced IL-8 reporter activation. Delta Np63 siRNA significantly inhibited proliferation, survival, and migration by HNSCC cells in vitro. Consistent with these data, an increase in nuclear Delta Np63, accompanied by increased proliferation (Ki-67) and adhesion (beta 4 integrin) markers, and induced inflammatory cell infiltration was observed throughout HNSCC specimens, when compared with the basilar pattern of protein expression and minimal inflammation seen in nonmalignant mucosa. Furthermore, overexpression of Delta Np63 alpha in squamous epithelial cells in transgenic mice leads to increased suprabasilar cRel, Ki-67, and cytokine expression, together with epidermal hyperplasia and diffuse inflammation, similar to HNSCC. Our study reveals Delta Np63 as a master transcription factor that, in coordination with NF-kappa B/Rels, orchestrates a broad gene program promoting epidermal hyperplasia, inflammation, and the malignant phenotype of HNSCC. Cancer Res; 71(10); 3688-700. (C) 2011 AACR.