title: Regulation of the expression of claudin 23 by the enhancer of zeste 2 polycomb group protein in colorectal cancer.
abstract: Altered epigenetic mechanisms, similar to gene mutations, contribute to the pathogenesis and molecular heterogeneity of neoplasms, including colorectal cancer (CRC). Enhancer of zeste 2 (EZH2) is a histone methyltransferase, which is involved in epigenetic gene silencing and is aberrantly expressed in CRC. Therefore, the identification of the genes regulated by EZH2 in CRC is important to improve current understanding of its role in cancer epigenetics. The present study used chromatin immunoprecipitation (ChIP) followed by deep sequencing to assess genome-wide EZH2‑DNA interactions in healthy or CRC mucosa samples. In total, 86.9/61.6 and 92.5/62.6 million tags were sequenced/mapped in healthy and CRC mucosa samples, respectively. The EZH2-binding densities were correlated with transcriptomic datasets and this demonstrated that the claudin-23 (CLDN23) gene, which encodes a component of cell-cell adhesion structures, was occupied by EZH2 and significantly silenced in CRC tissue. The measurement of DNA methylation at the CLDN23 promoter using pyrosequencing excluded the possibility that silencing of this gene in CRC patient samples was a result of DNA hypermethylation. Following treatment of the Colo205 and HT-29 CRC cell lines, with the EZH2 inhibitor, GSK126, the level of histone H3 lysine 27 trimethylation (H3K27me3) was reduced and the mRNA and protein expression levels of CLDN23 were increased. ChIP analysis confirmed that the level of H3K27m3 along the CLDN23 gene was decreased in the GSK126-treated cell lines. Furthermore, ChIP analysis of these samples detected histone H3 lysine 4 trimethylation (H3K4me3) at the CLDN23 promoter, demonstrating that the balance between H3K27me3 and H3K4me3 may underlie the regulation of the expression of CLDN23. The present study demonstrated an epigenetic link between the activity of the EZH2 methyltransferase at the CLDN23 locus and the expression of CLDN23 in CRC tissue.
authors.affiliation: Department of Gastroenterology and Hepatology, Medical Center for Postgraduate Education, Maria Sklodowska‑Curie Memorial Cancer Center and Institute of Oncology, Warsaw 02‑781, Poland.
authors.forename: Natalia
authors.initials: N
authors.lastname: Maryan
authors.affiliation: Department of Genetics, Maria Sklodowska‑Curie Memorial Cancer Center and Institute of Oncology, Warsaw 02‑781, Poland.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Statkiewicz
authors.affiliation: Department of Genetics, Maria Sklodowska‑Curie Memorial Cancer Center and Institute of Oncology, Warsaw 02‑781, Poland.
authors.forename: Michal
authors.initials: M
authors.lastname: Mikula
authors.affiliation: Department of Genetics, Maria Sklodowska‑Curie Memorial Cancer Center and Institute of Oncology, Warsaw 02‑781, Poland.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Goryca
authors.affiliation: Department of Gastroenterology and Hepatology, Medical Center for Postgraduate Education, Maria Sklodowska‑Curie Memorial Cancer Center and Institute of Oncology, Warsaw 02‑781, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Paziewska
authors.affiliation: Department of Genetics, Maria Sklodowska‑Curie Memorial Cancer Center and Institute of Oncology, Warsaw 02‑781, Poland.
authors.forename: Adriana
authors.initials: A
authors.lastname: Strzałkowska
authors.affiliation: Department of Genetics, Maria Sklodowska‑Curie Memorial Cancer Center and Institute of Oncology, Warsaw 02‑781, Poland.
authors.forename: Michalina
authors.initials: M
authors.lastname: Dabrowska
authors.affiliation: Department of Molecular and Translational Oncology, Maria Sklodowska‑Curie Memorial Cancer Center and Institute of Oncology, Warsaw 02‑781, Poland.
authors.forename: Mateusz
authors.initials: M
authors.lastname: Bujko
authors.affiliation: Department of Gastroenterology and Hepatology, Medical Center for Postgraduate Education, Maria Sklodowska‑Curie Memorial Cancer Center and Institute of Oncology, Warsaw 02‑781, Poland.
authors.forename: Jerzy
authors.initials: J
authors.lastname: Ostrowski
mesh_terms: D045744:Cell Line, Tumor; D057167:Claudins / Q000096:biosynthesis* / Q000235:genetics; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology; D019175:DNA Methylation / Q000235:genetics; D000071221:Enhancer of Zeste Homolog 2 Protein; D044127:Epigenesis, Genetic; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics; D020868:Gene Silencing; D015894:Genome, Human; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D007211:Indoles / Q000008:administration & dosage; D063151:Polycomb Repressive Complex 2 / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D011401:Promoter Regions, Genetic; D011728:Pyridones / Q000008:administration & dosage
chemical_list: C481943:CLDN23 protein, human; D057167:Claudins; C577920:GSK-2816126; D007211:Indoles; D011728:Pyridones; C498409:EZH2 protein, human; D000071221:Enhancer of Zeste Homolog 2 Protein; D063151:Polycomb Repressive Complex 2