title: TAp73 and ΔNp73 have opposing roles in 5-aza-2'-deoxycytidine-induced apoptosis in breast cancer cells.
abstract: The p73 gene contains an extrinsic P1 promoter and an intrinsic P2 promoter, controlling the transcription of the pro-apoptotic TAp73 isoform and the anti-apoptotic ΔΝp73 isoform, respectively. The DNA methylation status of both promoters act equally in the epigenetic transcriptional regulation of their relevant isoforms. The aim of this study was to analyze the different effects of these p73 isoforms in 5-aza-2'-deoxycytidine (5-aza-dC)-induced apoptosis in breast cancer cells. We investigated the effects of the DNA demethylation agent, 5-aza-dC, on the T-47D breast cancer cell line, and evaluated the methylation status of the p73 promoters and expression of TAp73 and ΔNp73. Furthermore, we assessed the expression of p53 and p73 isoforms in 5-aza-dC-treated T-47D cells and p53 knockout cells. 5-aza-dC induced significant anti-tumor effects in T-47D cells, including inhibition of cell viability, G1 phase arrest and apoptosis. This was associated with p73 promoter demethylation and a concomitant increase in TAp73 mRNA and protein expression. In contrast, the methylation status of promoter P2 was not associated with ΔNp73 mRNA or protein levels. Furthermore, demethylation of P2 failed to inhibit the expression of ΔNp73 with 5-aza-dC in the p53 knockdown cell model. Our study suggests that demethylation of the P1 and P2 promoters has opposite effects on the expression of p73 isoforms, namely up-regulation of TAp73 and down-regulation of ΔΝp73. We also demonstrate that p53 likely contributes to 5-aza-dC-induced ΔNp73 transcriptional inactivation in breast cancer cells.
authors.affiliation: Department of Medical Oncology, Jinling Hospital, School of Medicine, Southern Medical University, Guangzhou, 510282, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Lai
authors.affiliation: Department of Medical Oncology, Jinling Hospital, Medical School of Nanjing University, Nanjing, 210002, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Yang
authors.affiliation: Department of Medical Oncology, Jinling Hospital, Medical School of Nanjing University, Nanjing, 210002, China.
authors.forename: Wenwen
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Department of Medical Oncology, Jinling Hospital, School of Medicine, Southern Medical University, Guangzhou, 510282, China.
authors.forename: Yanru
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Medical Oncology, Jinling Hospital, Medical School of Nanjing University, Nanjing, 210002, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Xu
authors.affiliation: Department of Medical Oncology, Jinling Hospital, School of Medicine, Southern Medical University, Guangzhou, 510282, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Song
authors.affiliation: Department of Medical Oncology, Jinling Hospital, Medical School of Nanjing University, Nanjing, 210002, China.
authors.forename: Guichun
authors.initials: G
authors.lastname: Huang
authors.affiliation: Department of General Surgery, Jinling Hospital, Medical School of Nanjing University, Nanjing, 210002, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Gu
authors.affiliation: Department of Medical Oncology, Jinling Hospital, School of Medicine, Southern Medical University, Guangzhou, 510282, China ; Department of Medical Oncology, Jinling Hospital, Medical School of Nanjing University, Nanjing, 210002, China.
authors.forename: Xiaoxiang
authors.initials: X
authors.lastname: Guan
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001483:Base Sequence; D045744:Cell Line, Tumor; D019175:DNA Methylation / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D000077209:Decitabine; D005260:Female; D016193:G1 Phase / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D042361:Mammary Glands, Human / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014158:Transcription, Genetic; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency / Q000235:genetics*; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D000964:Antimetabolites, Antineoplastic; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D020033:Protein Isoforms; C000606460:TP73 protein, human; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; C000606369:delta Np73 protein, human; D000077209:Decitabine; D001374:Azacitidine
keywords: 5-aza-2′-deoxycytidine; breast cancer; methylation; p53; p73