title: Arsenic trioxide induces cell cycle arrest and alters DNA methylation patterns of cell cycle regulatory genes in colorectal cancer cells.
abstract: OBJECTIVE
  Cell cycle dysregulation is important in tumorigenesis. Transcriptional silencing of cell cycle regulatory genes, due to DNA methylation, is a common epigenetic event in malignancies. As2O3has been shown to induce cell cycle arrest and also to be a potential hypomethylating agent. Our study aimed to investigate DNA methylation patterns of cell cycle regulatory genes promoters, the effects of Arsenic trioxide (As2O3) on the methylated genes and cell cycle distribution in colorectal cancer (CRC) cell lines.
  
  
  METHODS
  The methylation-specific PCR (MSP) and/or restriction enzyme-based methods were used to study the promoter methylation patterns of 24 cell cycle regulatory genes in CRC cell lines. Gene expression level and cell cycle distribution were determined by Real-time PCR and flow cytometric analyses, respectively.
  
  
  RESULTS
  Our methylation analysis indicated that only promoters of RBL1 (p107), CHFR and p16 genes were aberrantly methylated in three cell lines. As2O3significantly decreased DNA methylation in promoter regions of these genes and restored their expression. We found that As2O3significantly reduced the expression of DNA methyltransferase 1 (DNMT1) and increased arsenic methyltransferase (AS3MT). Furthermore, As2O3altered transcriptional activity of several unmethylated cell cycle regulatory genes including cyclin B1, E1, D1, GADD45A and p21. Cell cycle flow cytometry analysis showed As2O3induced G2/M arrest in all three cell lines.
  
  
  CONCLUSIONS
  These data suggest that demethylation and alteration in the expression level of the cell cycle-related genes may be possible mechanisms in As2O3-induced cell cycle arrest in colorectal cancer cells.
authors: Hematology, Oncology and Stem Cell Transplantation Research Center, Shariati Hospital, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors: Haniyeh
authors: H
authors: Eyvani
authors: Hematology, Oncology and Stem Cell Transplantation Research Center, Shariati Hospital, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors: Farima
authors: F
authors: Moghaddaskho
authors: Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors: Majid
authors: M
authors: Kabuli
authors: Department of Medical Genetics and Molecular Biology, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran.
authors: Ali
authors: A
authors: Zekri
authors: Hematology, Oncology and Stem Cell Transplantation Research Center, Shariati Hospital, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors: Majid
authors: M
authors: Momeny
authors: Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors: Javad
authors: J
authors: Tavakkoly-Bazzaz
authors: Hematology, Oncology and Stem Cell Transplantation Research Center, Shariati Hospital, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors: Kamran
authors: K
authors: Alimoghaddam
authors: Hematology, Oncology and Stem Cell Transplantation Research Center, Shariati Hospital, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors: Ardeshir
authors: A
authors: Ghavamzadeh
authors: Hematology, Oncology and Stem Cell Transplantation Research Center, Shariati Hospital, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Electronic address: shghaffari200@yahoo.com.
authors: Seyed H
authors: SH
authors: Ghaffari
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000494:pharmacology*; D059447:Cell Cycle Checkpoints / Q000187:drug effects*; D045744:Cell Line, Tumor; D003106:Colon / Q000187:drug effects / Q000473:pathology; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics; D019175:DNA Methylation / Q000187:drug effects*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D010087:Oxides / Q000494:pharmacology*; D012007:Rectum / Q000187:drug effects / Q000473:pathology; D050720:Retinoblastoma-Like Protein p107 / Q000235:genetics
chemical_list: D000970:Antineoplastic Agents; D001152:Arsenicals; D010087:Oxides; C493844:RBL1 protein, human; D050720:Retinoblastoma-Like Protein p107; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human; D000077237:Arsenic Trioxide
keywords: AS3MT; Arsenic trioxide; CHFR; Cell cycle genes; Colorectal cancer; DNA methylation; DNMTs; RBL1; p16