title: Demethylation and alterations in the expression level of the cell cycle-related genes as possible mechanisms in arsenic trioxide-induced cell cycle arrest in human breast cancer cells.
abstract: Arsenic trioxide (As2O3) has been used clinically as an anti-tumor agent. Its mechanisms are mostly considered to be the induction of apoptosis and cell cycle arrest. However, the detailed molecular mechanisms of its anti-cancer action through cell cycle arrest are poorly known. Furthermore, As2O3has been shown to be a potential DNA methylation inhibitor, inducing DNA hypomethylation. We hypothesize that As2O3may affect the expression of cell cycle regulatory genes by interfering with DNA methylation patterns. To explore this, we examined promoter methylation status of 24 cell cycle genes in breast cancer cell lines and in a normal breast tissue sample by methylation-specific polymerase chain reaction and/or restriction enzyme-based methods. Gene expression level and cell cycle distribution were quantified by real-time polymerase chain reaction and flow cytometric analyses, respectively. Our methylation analysis indicates that only promoters of RBL1 (p107), RASSF1A, and cyclin D2 were aberrantly methylated in studied breast cancer cell lines. As2O3induced CpG island demethylation in promoter regions of these genes and restores their expression correlated with DNA methyltransferase inhibition. As2O3also induced alterations in messenger RNA expression of several cell cycle-related genes independent of demethylation. Flow cytometric analysis revealed that the cell cycle arrest induced by As2O3varied depending on cell lines, MCF-7 at G1 phase and both MDA-MB-231 and MDA-MB-468 cells at G2/M phase. These changes at transcriptional level of the cell cycle genes by the molecular mechanisms dependent and independent of demethylation are likely to represent the mechanisms of cell cycle redistribution in breast cancer cells, in response to As2O3treatment.
authors.affiliation: 1 Hematology, Oncology and Stem Cell Transplantation Research Center, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran.|2 Medical Genetics Department, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Farima
authors.initials: F
authors.lastname: Moghaddaskho
authors.affiliation: 1 Hematology, Oncology and Stem Cell Transplantation Research Center, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran.|2 Medical Genetics Department, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Haniyeh
authors.initials: H
authors.lastname: Eyvani
authors.affiliation: 2 Medical Genetics Department, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Ghadami
authors.affiliation: 2 Medical Genetics Department, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Javad
authors.initials: J
authors.lastname: Tavakkoly-Bazzaz
authors.affiliation: 1 Hematology, Oncology and Stem Cell Transplantation Research Center, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Kamran
authors.initials: K
authors.lastname: Alimoghaddam
authors.affiliation: 1 Hematology, Oncology and Stem Cell Transplantation Research Center, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Ardeshir
authors.initials: A
authors.lastname: Ghavamzadeh
authors.affiliation: 1 Hematology, Oncology and Stem Cell Transplantation Research Center, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Seyed H
authors.initials: SH
authors.lastname: Ghaffari
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D059447:Cell Cycle Checkpoints / Q000187:drug effects* / Q000235:genetics*; D045744:Cell Line, Tumor; D019175:DNA Methylation / Q000187:drug effects*; D005260:Female; D006801:Humans; D061986:MCF-7 Cells; D010087:Oxides / Q000494:pharmacology*; D011401:Promoter Regions, Genetic
chemical_list: D000970:Antineoplastic Agents; D001152:Arsenicals; D010087:Oxides; D000077237:Arsenic Trioxide
keywords: Breast cancer; DNA methylation; DNA methyltransferase; RBL1; arsenic trioxide; cell cycle genes