title: Atonal homolog 1 is required for growth and differentiation effects of notch/gamma-secretase inhibitors on normal and cancerous intestinal epithelial cells.
abstract: OBJECTIVE
  The atonal homolog 1 (Atoh1) transcription factor is required for intestinal secretory (goblet, Paneth, enteroendocrine) cell differentiation. Notch/gamma-secretase inhibitors (GSIs) block proliferation and induce secretory cell differentiation in the intestine. We used genetic analyses of mice to determine whether Atoh1 mediates the effects of GSIs in normal and cancerous intestinal epithelia.
  
  
  METHODS
  We studied mice with intestine-specific disruption of Atoh1 (Atoh1(Deltaintestine)), the adenomatosis polyposis coli (APC)(min) mutation, both mutations (Atoh1(Deltaintestine); APC(min)), or littermate controls; mice were given GSI or vehicle. Colorectal cancer (CRC) cell lines were treated with GSI or vehicle and with small hairpin RNAs to reduce ATOH1. Differentiation and homeostasis were assessed by protein, RNA, and histologic analyses.
  
  
  RESULTS
  GSIs failed to induce secretory cell differentiation or apoptosis or decrease proliferation of Atoh1-null progenitor cells, compared with wild-type cells. Exposure of APC(min) adenomas to GSIs decreased proliferation and increased secretory cell numbers in an Atoh1-dependent manner. In CRC cells treated with GSI, ATOH1 levels were correlated inversely with proliferation. ATOH1 was required for secretory cell gene expression in cell lines and in mice.
  
  
  CONCLUSIONS
  ATOH1 is required for all effects of GSIs in intestinal crypts and adenomas; Notch has no unique function in intestinal progenitors and cancer cells other than to regulate ATOH1 expression. Reducing ATOH1 activity might mitigate intestinal toxicity from systemic GSI therapy for nonintestinal diseases. Among gastrointestinal malignancies, ATOH1 mediates the effects of GSIs, so ATOH1 expression levels might predict responses to these inhibitors. We propose that only the subset of CRCs that retain ATOH1 expression will respond to GSIs.
authors.affiliation: Division of Gastroenterology, Hepatology, and Nutrition, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.
authors.forename: Avedis
authors.initials: A
authors.lastname: Kazanjian
authors.forename: Taeko
authors.initials: T
authors.lastname: Noah
authors.forename: Douglas
authors.initials: D
authors.lastname: Brown
authors.forename: Jarred
authors.initials: J
authors.lastname: Burkart
authors.forename: Noah F
authors.initials: NF
authors.lastname: Shroyer
mesh_terms: D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects*; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic; D017491:Genes, APC; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008822:Mice, Transgenic; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D051880:Receptors, Notch / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013997:Time Factors
chemical_list: D053829:Amyloid Precursor Protein Secretases; D000970:Antineoplastic Agents; D051792:Basic Helix-Loop-Helix Proteins; D012333:RNA, Messenger; D051880:Receptors, Notch; C500942:ATOH1 protein, human; C500943:Atoh1 protein, mouse