title: DNA methylation associated with polycomb repression in retinoic acid receptor β silencing.
abstract: Retinoic acid receptor β 2 (RARβ2) is a tumor suppressor gene whose loss of expression is recurrent in prostate cancers. Here we studied the epigenetic mechanisms leading to its stable silencing. First, we characterized all RARβ isoforms in 6 human tumor cell lines (prostate DU145, LNCaP, PC3, lung A549, breast Hs578T, and colon HCT116) by RT-PCR and Western blot. We excluded loss of heterozygosity (2D-FISH) and loss of RARa expression, an upstream regulator, as origin of RARβ2 silencing. All data concluded to an epigenetic silencing. In agreement, a DNA methylation inhibitor restored its expression. Second RARβ2 loss of expression was found associated with different epigenetic profiles in LNCaP and DU145 cells. According to bisulfite sequencing and ChIP analysis, we observed heavy methylation (97%) of the RARβ2 promoter with repressive histone mark H3K9me3 in LNCaP. While DNA methylation and polycomb repression are described to be mutually exclusive at CpG-rich promoters, we observed that in DU145, moderate DNA methylation (36%) and H3K9me3 mark were present concomitantly with H3K27me3, a signature of polycomb repression. In summary, we provide new insights on how the RARβ2 promoter is silenced, reveal the existence of two distinct repressive chromatin profiles at the same locus, and support a polycomb-mediated epigenetic repression process in prostate cancer.
authors.affiliation: CNRS-Pierre Fabre, Unité de Service et de Recherche 3388, Epigenetic Targeting of Cancer, Centre de Recherche et Développement Pierre Fabre, Toulouse, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Moison
authors.forename: Catherine
authors.initials: C
authors.lastname: Senamaud-Beaufort
authors.forename: Lou
authors.initials: L
authors.lastname: Fourrière
authors.forename: Christine
authors.initials: C
authors.lastname: Champion
authors.forename: Alexandre
authors.initials: A
authors.lastname: Ceccaldi
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Lacomme
authors.forename: Antoine
authors.initials: A
authors.lastname: Daunay
authors.forename: Jörg
authors.initials: J
authors.lastname: Tost
authors.forename: Paola B
authors.initials: PB
authors.lastname: Arimondo
authors.forename: Anne-Laure
authors.initials: AL
authors.lastname: Guieysse-Peugeot
mesh_terms: D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D045744:Cell Line, Tumor; D002843:Chromatin / Q000187:drug effects; D018899:CpG Islands / Q000187:drug effects / Q000235:genetics; D019175:DNA Methylation / Q000187:drug effects; D000077209:Decitabine; D004791:Enzyme Inhibitors / Q000494:pharmacology; D044127:Epigenesis, Genetic / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics; D020868:Gene Silencing / Q000187:drug effects; D006657:Histones / Q000235:genetics / Q000378:metabolism; D006801:Humans; D009369:Neoplasms / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism*
chemical_list: D002843:Chromatin; D004791:Enzyme Inhibitors; D006657:Histones; D018168:Receptors, Retinoic Acid; C082925:retinoic acid receptor beta; D000077209:Decitabine; D001374:Azacitidine