AP1- and NF-κB-binding sites conserved among mammalian WNT10B orthologs elucidate the TNFα-WNT10B signaling loop implicated in carcinogenesis and adipogenesis

WNT signals are context-dependently transduced to canonical and non-canonical signaling cascades. We cloned and characterized wild-type human WNT10B, while another group cloned aberrant human WNT10B with Gly60Asp amino-acid substitution. Proto-oncogene WNT10B is expressed in gastric cancer, pancreatic cancer, breast cancer, esophageal cancer, and cervical cancer. Because WNT10B blocks adipocyte differentiation, coding SNP of WNT10B gene is associated with familial obesity. In 2001, we reported WNT10B upregulation by TNFα. Here, comparative integromics analyses on WNT10B orthologs were performed to elucidate the transcriptional mechanism of WNT10B. Chimpanzee WNT10B and cow Wnt10b genes were identified within NW_001223159.1 and AC150975.2 genome sequences, respectively, by using bioinformatics (Techint) and human intelligence (Humint). Chimpanzee WNT10B and cow Wnt10b showed 98.7% and 95.1% total-amino-acid identity with human WNT10B, respectively. N-terminal signal peptide, 24 Cys residues, two Asn-linked glycosylation sites, and Gly60 of human WNT10B were conserved among mammalian WNT10B orthologs. Transcription start site of human WNT10B gene was 106-bp upstream of NM_003394.2 RefSeq 5'-end. Number of GC di-nucleotide repeats just down-stream of WNT10B transcription start site varied among primates and human population. Comparative genomics analyses revealed that double AP1-binding sites in the 5'-flanking promoter region and NF-κB-binding site in intron 3 were conserved among human, chimpanzee, cow, mouse, and rat WNT10B orthologs. Because TNFα signaling through TNFR1 and TRADD/RIP/TRAF2 complex activates JUN kinase (JNK) and IκB kinase (IKK) signaling cascades, conserved AP1- and NF-κB-binding sites explain the mechanism of TNFα-induced WNT10B upregulation. TNFα-WNT10B signaling loop is the negative feedback mechanism of adipogenesis to prevent obesity and metabolic syndrome. On the other hand, TNFα-WNT10B signaling loop is implicated in carcinogenesis. Inhibitors of TNFα-WNT10B signaling loop could be utilized for the prevention or treatment of cancer associated with chronic inflammation, such as gastric, liver, breast and pancreatic cancer.