title: The Notch-2 gene is regulated by Wnt signaling in cultured colorectal cancer cells.
abstract: BACKGROUND
  Notch and Wnt pathways are key regulators of intestinal homeostasis and alterations in these pathways may lead to the development of colorectal cancer (CRC). In CRC the Apc/β-catenin genes in the Wnt signaling pathway are frequently mutated and active Notch signaling contributes to tumorigenesis by keeping the epithelial cells in a proliferative state. These pathways are simultaneously active in proliferative adenoma cells and a crosstalk between them has previously been suggested in normal development as well as in cancer.
  
  
  RESULTS
  In this study, in silico analysis of putative promoters involved in transcriptional regulation of genes coding for proteins in the Notch signaling pathway revealed several putative LEF-1/TCF sites as potential targets for β-catenin and canonical Wnt signaling. Further results from competitive electrophoretic mobility-shift assay (EMSA) studies suggest binding of several putative sites in Notch pathway gene promoters to in vitro translated β-catenin/Lef-1. Wild type (wt)-Apc negatively regulates β-catenin. By induction of wt-Apc or β-catenin silencing in HT29 cells, we observed that several genes in the Notch pathway, including Notch-2, were downregulated. Finally, active Notch signaling was verified in the Apc(Min/+) mouse model where Hes-1 mRNA levels were found significantly upregulated in intestinal tumors compared to normal intestinal mucosa. Luciferase assays showed an increased activity for the core and proximal Notch-2 promoter upon co-transfection of HCT116 cells with high expression recombinant Tcf-4, Lef-1 or β-catenin.
  
  
  CONCLUSIONS
  In this paper, we identified Notch-2 as a novel target for β-catenin-dependent Wnt signaling. Furthermore our data supports the notion that additional genes in the Notch pathway might be transcriptionally regulated by Wnt signaling in colorectal cancer.
authors: Division of Cell Biology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköpings university, Linköping, Sweden. jonas.ungerback@liu.se
authors: Jonas
authors: J
authors: Ungerbäck
authors: Nils
authors: N
authors: Elander
authors: John
authors: J
authors: Grünberg
authors: Mikael
authors: M
authors: Sigvardsson
authors: Peter
authors: P
authors: Söderkvist
mesh_terms: D000236:Adenoma / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000378:metabolism; D001665:Binding Sites; D015179:Colorectal Neoplasms / Q000235:genetics*; D019295:Computational Biology; D015972:Gene Expression Regulation, Neoplastic; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D008156:Luciferases / Q000235:genetics; D051821:Lymphoid Enhancer-Binding Factor 1 / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D051883:Receptor, Notch2 / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics*; D000073940:Transcription Factor 4; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation / Q000235:genetics; D051153:Wnt Proteins / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D051821:Lymphoid Enhancer-Binding Factor 1; C497764:NOTCH2 protein, human; C497765:Notch2 protein, mouse; D051883:Receptor, Notch2; C532096:TCF4 protein, human; D000073940:Transcription Factor 4; D014157:Transcription Factors; D051153:Wnt Proteins; D051176:beta Catenin; D008156:Luciferases