title: SPDEF Induces Quiescence of Colorectal Cancer Cells by Changing the Transcriptional Targets of β-catenin.
abstract: The canonical Wnt signaling pathway activates the transcriptional activity of β-catenin. This pathway is often activated in colorectal cancer cells, but strategies to block it in tumors have not been effective. The SAM pointed domain containing ETS transcription factor (SPDEF) suppresses formation of colon tumors by unclear mechanisms. We investigated these mechanisms and the effects of SPDEF on β-catenin activity in mouse models of colorectal cancer (CRC), CRC cell lines, and mouse and human normal and cancer colonoids.
  
  
  
  We performed studies of Lgr5CreERT2; β-cateninexon3; Rosa26LSL-rtta-ires-EGFP; TRE-Spdef mice, which express an oncogenic form of β-catenin in Lgr5-positive ISCs upon administration of tamoxifen and SPDEF upon administration of tetracycline. CRC lines (HCT116 and SW480) were engineered to express inducible tagged SPDEF or vector (control) and subcutaneously injected into immunodeficient NSG mice. We generated SPDEF-inducible human colonoids, including a line derived from normal rectal mucosa (control) and an adenocarcinoma line derived from a patient with germline MUTYH mutation. Full-length and truncated forms of SPDEF were expressed in CRC cells; cells were assayed for β-catenin activity and studied in immunoprecipitation and chromatin immunoprecipitation assays.
  
  
  
  Expression of SPDEF was sufficient to inhibit intestinal tumorigenesis by activated β-catenin, block tumor cell proliferation, and restrict growth of established tumors. In tumor cells with activated β -catenin, expression of SPDEF induced a quiescent state, which was reversed when SPDEF expression was stopped. In mouse and human normal and tumor-derived enteroids/colonoids, those that expressed SPDEF for 3 days were significantly smaller. SPDEF inhibited the transcriptional activity of β-catenin via a protein-protein interaction, independent of SPDEF DNA binding capacity. SPDEF disrupted β-catenin binding to TCF1 and TCF3, displacing β-catenin from enhancer regions of genes that regulate the cell cycle but not genes that regulate stem cell activities.
  
  
  
  In studies of mice and human CRC, we found that SPDEF induces a quiescent state in CRC cells by disrupting binding of β-catenin to TCF1 and TCF3 and regulation of genes that control the cell cycle. In this model, β-catenin activity determines the proliferation or quiescence of CRC cells based on the absence or presence of SPDEF.
authors.affiliation: Integrative Molecular and Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, Texas; Department of Medicine and Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas.
authors.forename: Yuan-Hung
authors.initials: YH
authors.lastname: Lo
authors.affiliation: Division of Gastroenterology, Hepatology, and Nutrition, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.
authors.forename: Taeko K
authors.initials: TK
authors.lastname: Noah
authors.affiliation: Integrative Molecular and Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, Texas; Department of Medicine and Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas.
authors.forename: Min-Shan
authors.initials: MS
authors.lastname: Chen
authors.affiliation: Integrative Molecular and Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, Texas; Department of Medicine and Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas.
authors.forename: Winnie
authors.initials: W
authors.lastname: Zou
authors.affiliation: Departments of Clinical Cancer Prevention, GI Medical Oncology and Clinical Cancer Genetics Program, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Ester
authors.initials: E
authors.lastname: Borras
authors.affiliation: Departments of Clinical Cancer Prevention, GI Medical Oncology and Clinical Cancer Genetics Program, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Vilar
authors.affiliation: Integrative Molecular and Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, Texas; Department of Medicine and Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas; Division of Medicine, Section of Gastroenterology & Hepatology, Baylor College of Medicine, Houston, Texas. Electronic address: noah.shroyer@bcm.edu.
authors.forename: Noah F
authors.initials: NF
authors.lastname: Shroyer
mesh_terms: D000236:Adenoma / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D060466:Axin Protein / Q000235:genetics; D063646:Carcinogenesis; D002453:Cell Cycle / Q000235:genetics; D049109:Cell Proliferation; D002843:Chromatin / Q000378:metabolism; D003106:Colon; D015179:Colorectal Neoplasms / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D019938:Cyclin D1 / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D045325:HCT116 Cells; D057809:HEK293 Cells; D006801:Humans; D018960:Hyaluronan Receptors / Q000032:analysis; D007413:Intestinal Mucosa / Q000737:chemistry / Q000473:pathology; D051821:Lymphoid Enhancer-Binding Factor 1 / Q000378:metabolism; D008297:Male; D051379:Mice; D009940:Organoids; D011401:Promoter Regions, Genetic; D050783:Proto-Oncogene Proteins c-ets / Q000235:genetics* / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics; D036183:Receptor, EphB2 / Q000235:genetics; D013234:Stem Cells; D051820:TCF Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics*; D014162:Transfection; D060449:Wnt Signaling Pathway; D051176:beta Catenin / Q000235:genetics* / Q000378:metabolism*
chemical_list: C491761:AXIN2 protein, human; D060466:Axin Protein; C530104:CCND1 protein, human; C112697:CD44v6 antigen; D002843:Chromatin; D018960:Hyaluronan Receptors; D051821:Lymphoid Enhancer-Binding Factor 1; D050783:Proto-Oncogene Proteins c-ets; D016271:Proto-Oncogene Proteins c-myc; C403974:SPDEF protein, human; C519908:Spdef protein, mouse; D051820:TCF Transcription Factors; D051176:beta Catenin; D019938:Cyclin D1; C586310:EPHB2 protein, human; D036183:Receptor, EphB2
keywords: Colon Cancer; TCF/LEF Factors; Tumor Suppressor; Xenograft