Transcriptional regulation of WNT2B based on the balance of Hedgehog, Notch, BMP and WNT signals.

We cloned and characterized human WNT2B in 1996, and then others cloned and characterized mouse, chicken, and zebrafish WNT2B orthologs. WNT2B is expressed in several types of human cancer, such as basal cell carcinoma, gastric cancer, breast cancer, head/neck squamous cell carcinoma, cervical cancer and leukemia. WNT2B is one of canonical WNTs transducing signals through Frizzled (FZD) and LRP5/LRP6 receptors to beta-catenin-TCF/LEF signaling cascade. Here, refined integrative genomic analyses on WNT2B orthologs were carried out to elucidate its transcriptional mechanisms. GLI-, double FOX-, HES/HEY-, bHLH-, and Sp1-binding sites within mammalian WNT2B promoter were well conserved. Because GLI1, FOXA2, FOXC2, FOXE1, FOXF1 and FOXL1 are direct target genes of Hedgehog-GLI2 signaling cascade, Hedgehog signals should induce WNT2B upregulation through GLI family members as well as FOX family members. Notch, BMP and Hedgehog signals inhibit WNT2B expression via HES/HEY-binding to N-box, whereas BMP and WNT signals inhibit bHLH transcription factor-induced WNT2B expression via ID1, ID2, ID3, MSX1 or MSX2. Together these facts indicate that Hedgehog signals and bHLH transcription factors are involved in WNT2B upregulation, which is counteracted by BMP, WNT and Notch signals. Mesenchymal BMP induces IHH expression in gastrointestinal epithelial cells, and then epithelial Hedgehog induces WNT2B and BMP4 expression in mesenchymal cells. NF-kappaB signals induce SHH upregulation, and WNT2B is upregulated in inflammatory bowel disease (IBD). BMP-IHH and inflammation-SHH signaling loops are involved in WNT2B up-regulation during embryogenesis, adult tissue homeostasis, and carcinogenesis.