title: Colon epithelial cell differentiation is inhibited by constitutive c-myb expression or mutant APC plus activated RAS.
abstract: Blocked differentiation is a hallmark of cancer cells and the restoration of differentiation programs in vivo is an actively pursued clinical aim. Understanding the key regulators of cyto-differentiation may focus therapies on molecules that reactivate this process. c-myb expression declines rapidly when human colon cancer epithelial cells are induced to differentiate with the physiologically relevant short-chain fatty acid, sodium butyrate. These cells show increased expression of alkaline phosphatase and cytokeratin 8. Similarly, murine Immorto-epithelial cells derived from wild-type colon cells also show c-myb mRNA declines when induced to differentiate with sodium butyrate. Immorto-cells harboring a single APC mutation are indistinguishable from wild-type cells with regard to differentiation, while addition of activated RAS alone markedly enhances differentiation. In marked contrast, complete differentiation arrest occurs when both APC and RAS are mutated. Expression of MybER, a 4-hydroxytamoxifen-activatable form of c-Myb, blocks differentiation in wildtype and APC mutant Immorto-cell lines as well as LIM1215 human colon carcinoma cells. These data identify two pathways of oncogenic change that lead to retarded epithelial cell differentiation, one involving the presence of a single APC mutation in conjunction with activated RAS or alternatively constitutive c-myb expression.
authors.affiliation: Differentiation and Transcription Laboratory, Trescowthick Research Laboratories, Peter MacCallum Cancer Centre, University of Melbourne, Australia. rob.ramsay@Petermac.org
authors.forename: Robert G
authors.initials: RG
authors.lastname: Ramsay
authors.forename: Daniel
authors.initials: D
authors.lastname: Ciznadija
authors.forename: Catherine
authors.initials: C
authors.lastname: Sicurella
authors.forename: Nancy
authors.initials: N
authors.lastname: Reyes
authors.forename: Ken
authors.initials: K
authors.lastname: Mitchelhill
authors.forename: Phillip K
authors.initials: PK
authors.lastname: Darcy
authors.forename: Giovanna
authors.initials: G
authors.lastname: D'Abaco
authors.forename: Theo
authors.initials: T
authors.lastname: Mantamadiotis
mesh_terms: D025601:Adenomatous Polyposis Coli Protein / Q000235:genetics* / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000032:analysis / Q000378:metabolism; D000818:Animals; D002087:Butyrates / Q000494:pharmacology; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000737:chemistry; D003106:Colon / Q000166:cytology*; D003110:Colonic Neoplasms / Q000235:genetics* / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000032:analysis / Q000378:metabolism; D003600:Cytosol / Q000737:chemistry; D015536:Down-Regulation / Q000235:genetics; D004847:Epithelial Cells / Q000166:cytology; D015870:Gene Expression / Q000235:genetics; D011905:Genes, ras / Q000235:genetics*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000032:analysis / Q000378:metabolism; D007413:Intestinal Mucosa / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D009154:Mutation / Q000235:genetics; D020598:Proto-Oncogene Proteins c-myb / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D015534:Trans-Activators / Q000032:analysis / Q000378:metabolism; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000032:analysis / Q000378:metabolism; D051153:Wnt Proteins; D051176:beta Catenin
chemical_list: D025601:Adenomatous Polyposis Coli Protein; D002087:Butyrates; C495270:CTNNB1 protein, human; C495267:CTNNB1 protein, mouse; D003598:Cytoskeletal Proteins; D036341:Intercellular Signaling Peptides and Proteins; D020598:Proto-Oncogene Proteins c-myb; D012333:RNA, Messenger; D015534:Trans-Activators; D016159:Tumor Suppressor Protein p53; D051153:Wnt Proteins; D051176:beta Catenin; D000469:Alkaline Phosphatase