title: KLF4 suppresses transformation of pre-B cells by ABL oncogenes.
abstract: Genes that are strongly repressed after B-cell activation are candidates for being inactivated, mutated, or repressed in B-cell malignancies. Krüppel-like factor 4 (Klf4), a gene down-regulated in activated murine B cells, is expressed at low levels in several types of human B-cell lineage lymphomas and leukemias. The human KLF4 gene has been identified as a tumor suppressor gene in colon and gastric cancer; in concordance with this, overexpression of KLF4 can suppress proliferation in several epithelial cell types. Here we investigate the effects of KLF4 on pro/pre-B-cell transformation by v-Abl and BCR-ABL, oncogenes that cause leukemia in mice and humans. We show that overexpression of KLF4 induces arrest and apoptosis in the G1 phase of the cell cycle. KLF4-mediated death, but not cell-cycle arrest, can be rescued by Bcl-XL overexpression. Transformed pro/pre-B cells expressing KLF4 display increased expression of p21CIP and decreased expression of c-Myc and cyclin D2. Tetracycline-inducible expression of KLF4 in B-cell progenitors of transgenic mice blocks transformation by BCR-ABL and depletes leukemic pre-B cells in vivo. Collectively, our work identifies KLF4 as a putative tumor suppressor in B-cell malignancies.
authors.affiliation: Department of Molecular Biology and Biochemistry, University of California-Irvine, 3242 McGaugh Hall, Irvine, CA 92697-3900, USA.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Kharas
authors.forename: Isharat
authors.initials: I
authors.lastname: Yusuf
authors.forename: Vanessa M
authors.initials: VM
authors.lastname: Scarfone
authors.forename: Vincent W
authors.initials: VW
authors.lastname: Yang
authors.forename: Julia A
authors.initials: JA
authors.lastname: Segre
authors.forename: Claudia S
authors.initials: CS
authors.lastname: Huettner
authors.forename: David A
authors.initials: DA
authors.lastname: Fruman
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000378:metabolism*; D002453:Cell Cycle; D016923:Cell Death; D002471:Cell Transformation, Neoplastic / Q000378:metabolism*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D016044:Fusion Proteins, bcr-abl / Q000235:genetics / Q000378:metabolism*; D016193:G1 Phase; D015973:Gene Expression Regulation, Leukemic / Q000235:genetics; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D016374:Oncogene Proteins v-abl / Q000235:genetics / Q000378:metabolism*; D055291:Salivary alpha-Amylases; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004268:DNA-Binding Proteins; C000715467:KLF4 protein, human; C000715468:Klf4 protein, mouse; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; D016374:Oncogene Proteins v-abl; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D016044:Fusion Proteins, bcr-abl; C524799:Amy1 protein, mouse; D055291:Salivary alpha-Amylases