Characterization of sonic hedgehog as a novel NF-kappaB target gene that promotes NF-kappaB-mediated apoptosis resistance and tumor growth in vivo.
To explore mechanisms controlling sonic hedgehog (Shh) expression in human cancers, we investigated regulation of Shh by the transcription factor NF-kappaB. We identify putative NF-kappaB binding sites in the human Shh promoter region that specifically bind NF-kappaB complexes. Further, NF-kappaB activation by tumor necrosis factor alpha (TNF-alpha) or p65 overexpression stimulates Shh promoter activity and p65 binds to Shh promoter in vivo. NF-kappaB-mediated transcriptional activation of Shh is mapped to a minimal NF-kappaB consensus site at position +139 of Shh promoter. NF-kappaB activation results in increased Shh mRNA and protein expression in vitro and, notably, also in vivo in a genetic mouse model of inducible NF-kappaB activity. Specific NF-kappaB inhibition by inhibitory NF-kappaBalpha (Ikappa-Balpha) superrepressor or p65 knockdown inhibits NF-kappaB-induced Shh promoter activation and Shh expression. NF-kappaB-mediated Shh expression promotes proliferation and confers resistance to TRAIL-induced apoptosis. Silencing of Shh prevents NF-kappaB-stimulated proliferation, while the addition of Shh rescues the proliferation defect imposed by NF-kappaB inhibition. Notably, NF-kappaB-stimulated tumor growth is significantly impaired by Shh knockdown in an in vivo model of pancreatic cancer. By demonstrating that NF-kappaB regulates Shh expression, which contributes to NF-kappaB-mediated proliferation and apoptosis resistance in vitro and in vivo, our findings have important implications to target aberrant Shh expression in human cancers.
Kasperczyk
Hubert
H
University Children's Hospital, Eythstr. 24, D-89075 Ulm, Germany. simone.fulda@uniklinik-ulm.de
Baumann
Bernd
B
Debatin
Klaus-Michael
KM
Fulda
Simone
S
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001483:Base Sequence; D045744:Cell Line, Tumor; D016384:Consensus Sequence; D004268:DNA-Binding Proteins; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D053823:Hedgehog Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism*; D009369:Neoplasms / Q000378:metabolism / Q000473:pathology*; D011401:Promoter Regions, Genetic; D011485:Protein Binding
D004268:DNA-Binding Proteins; D053823:Hedgehog Proteins; D016328:NF-kappa B; C509239:SHH protein, human; C465570:Shh protein, mouse