Transcriptional mechanisms of WNT5A based on NF-κB, Hedgehog, TGFβ, and Notch signaling cascades

Abstract

WNT5A is a cancer-associated gene involved in invasion and metastasis of melanoma, breast cancer, pancreatic cancer, and gastric cancer. WNT5A transduces signals through Frizzled, ROR1, ROR2 or RYK receptors to β-catenin-TCF/LEF, DVL-RhoA-ROCK, DVL-RhoB-Rab4, DVL-Rac-JNK, DVL-aPKC, Calcineurin-NFAT, MAP3K7-NLK, MAP3K7-NF-κB, and DAG-PKC signaling cascades in a context-dependent manner. SNAI1 (Snail), CD44, G3BP2, and YAP1 are WNT5A target genes. We and other groups previously reported that IL6- or LIF-induced signaling through JAK-STAT3 signaling cascade is involved in WNT5A upregulation (STAT3-WNT5A signaling loop). Here, refined integrative genomic analyses of WNT5A were carried out to elucidate other mechanisms of WNT5A transcription. The WNT5A gene was found to encode two isoforms by using alternative first exons 1A and 1B. Quadruple Smad-binding elements (SBEs), single Sp1-binding site (GC-box), PPARγ-binding site, C/EBP-binding site and bHLH-binding site within the promoter A region, 5′-adjacent to exon 1A, were conserved in human WNT5A, chimpanzee WNT5A, mouse Wnt5a, and rat Wnt5a. NF-κB-binding site, CUX1-binding site, double SBEs and double GC-boxes within the promoter B region, 5′-adjacent to exon 1B, were conserved in mammalian WNT5A orthologs. Quadruple FOX-binding sites and double SBEs within ultra-conserved intron 1 were also conserved in mammalian WNT5A orthologs. Conserved NF-κB-binding site within the WNT5A promoter B region elucidated the mechanisms that TNFα and toll-like receptor (TLR) signals upregulate WNT5A via MAP3K7. Quadruple FOX-binding sites rather than GLI-binding site revealed that Hedgehog signals induce WNT5A upregulation indirectly via FOX family members, such as FOXA2, FOXC2, FOXE1, FOXF1 and FOXL1. TGFβ signals were found to upregulate WNT5A expression directly through the Smad complex, and also indirectly through Smad-induced CUX1 and MAP3K7-mediated NF-κB. Together these facts indicate that WNT5A is transcribed based on multiple mechanisms, such as NF-κB, Hedgehog, TGFβ, and Notch signaling cascades.