title: Krüppel-like factor 9 (KLF9) prevents colorectal cancer through inhibition of interferon-related signaling.
abstract: Expression of the transcription factor Krüppel-like factor 9 (KLF9) is frequently reduced in colorectal cancers, although a tumor suppressive role has not been established. To determine if KLF9 suppresses intestinal adenoma formation, we generated mice of distinct Klf9 genotypes in the background of the Apc (Min/+) mouse and compared their adenoma burdens at 16 weeks of age. While small intestine adenoma burden remained unchanged among Klf9 genotypes, male and female Apc(Min/+)/Klf9(-/-) and Apc(Min/+)/Klf9(+/-) mice exhibited significantly more colon adenomas than their Apc(Min/+)/Klf9(+/+) counterparts. Microarray analysis showed significant increases in the expression of interferon-induced genes in the colon mucosa of female Apc (Min/+)/Klf9(+/-) and Apc(Min/+)/Klf9(-/-) compared to Apc(Min/+)/Klf9(+/+) mice, prior to overt adenoma occurrence. Gene upregulation was confirmed by qPCR of colon mucosa and by siRNA knockdown of KLF9 in human HT29 colorectal cancer cells. Increases in expression of these genes were further augmented by supplementation with Interferon β1. Circulating levels of the cytokine, interferon-stimulated gene 15 (ISG15) were increased in Apc(Min/+)/Klf9(+/-) and Apc(Min/+)/Klf9(-/-) mice relative to Apc(Min/+)/Klf9(+/+). Additionally, colon mucosal levels of ISG15 were increased in Apc(Min/+)/Klf9(+/-) mice. Chromatin immunoprecipitation demonstrated KLF9 recruitment to the ISG15 promoter. Lastly, treatment with ISG15 suppressed apoptosis in HT29 cells, in the presence and absence of 5-fluorouracil (5FU). Results show KLF9 to be a haploinsufficient suppressor of colon tumorigenesis in Apc(Min/+) mice in part, by repression of ISG15 and the latter's antiapoptotic function.
  
  
  CONCLUSIONS
  Krüppel-like factor 9 (KLF9) is a haploinsufficient tumor suppressor in the ApcMin/+ mouse colon by suppressing expression of ISG15, an apoptosis-inhibiting cytokine.
authors.affiliation: Interdisciplinary Biomedical Sciences Program, Department of Physiology and Biophysics.
authors.forename: Adam R
authors.initials: AR
authors.lastname: Brown
authors.affiliation: Interdisciplinary Biomedical Sciences Program, Department of Physiology and Biophysics.
authors.forename: Rosalia C M
authors.initials: RC
authors.lastname: Simmen
authors.affiliation: Division of Genetics and.
authors.forename: Vinay R
authors.initials: VR
authors.lastname: Raj
authors.affiliation: Interdisciplinary Biomedical Sciences Program.
authors.forename: Trang T
authors.initials: TT
authors.lastname: Van
authors.affiliation: Department of Pediatrics, University of Arkansas for Medical Sciences, Slot #505, 4301 West Markham Street, Little Rock, AR 72205, USA.
authors.forename: Stewart L
authors.initials: SL
authors.lastname: MacLeod
authors.affiliation: Interdisciplinary Biomedical Sciences Program, Department of Physiology and Biophysics, simmenfranka@uams.edu.
authors.forename: Frank A
authors.initials: FA
authors.lastname: Simmen
mesh_terms: D000236:Adenoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000235:genetics; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D016207:Cytokines / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D019073:HT29 Cells; D057895:Haploinsufficiency / Q000235:genetics; D006801:Humans; D016899:Interferon-beta / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000473:pathology; D051741:Kruppel-Like Transcription Factors / Q000235:genetics*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D011401:Promoter Regions, Genetic / Q000235:genetics; D034622:RNA Interference; D034741:RNA, Small Interfering; D015398:Signal Transduction / Q000235:genetics; D014452:Ubiquitins / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology
chemical_list: D016207:Cytokines; C489550:G1p2 protein, mouse; C489676:KLF9 protein, human; C489675:Klf9 protein, mouse; D051741:Kruppel-Like Transcription Factors; D034741:RNA, Small Interfering; D014452:Ubiquitins; C074034:ISG15 protein, human; D016899:Interferon-beta