title: Activation of silenced tumor suppressor genes in prostate cancer cells by a novel energy restriction-mimetic agent.
abstract: BACKGROUND
  Targeting tumor metabolism by energy restriction-mimetic agents (ERMAs) has emerged as a strategy for cancer therapy/prevention. Evidence suggests a mechanistic link between ERMA-mediated antitumor effects and epigenetic gene regulation.
  
  
  METHODS
  Microarray analysis showed that a novel thiazolidinedione-derived ERMA, CG-12, and glucose deprivation could suppress DNA methyltransferase (DNMT)1 expression and reactivate DNA methylation-silenced tumor suppressor genes in LNCaP prostate cancer cells. Thus, we investigated the effects of a potent CG-12 derivative, CG-5, vis-à-vis 2-deoxyglucose, glucose deprivation and/or 5-aza-deoxycytidine, on DNMT isoform expression (Western blotting, RT-PCR), DNMT1 transcriptional activation (luciferase reporter assay), and expression of genes frequently hypermethylated in prostate cancer (quantitative real-time PCR). Promoter methylation was assessed by pyrosequencing analysis. SiRNA-mediated knockdown and ectopic expression of DNMT1 were used to validate DNMT1 as a target of CG-5.
  
  
  RESULTS
  CG-5 and glucose deprivation upregulated the expression of DNA methylation-silenced tumor suppressor genes, including GADD45a, GADD45b, IGFBP3, LAMB3, BASP1, GPX3, and GSTP1, but also downregulated methylated tumor/invasion-promoting genes, including CD44, S100A4, and TACSTD2. In contrast, 5-aza-deoxycytidine induced global reactivation of these genes. CG-5 mediated these epigenetic effects by transcriptional repression of DNMT1, which was associated with reduced expression of Sp1 and E2F1. SiRNA-mediated knockdown and ectopic expression of DNMT1 corroborated DNMT1's role in the modulation of gene expression by CG-5. Pyrosequencing revealed differential effects of CG-5 versus 5-aza-deoxycytidine on promoter methylation in these genes.
  
  
  CONCLUSIONS
  These findings reveal a previously uncharacterized epigenetic effect of ERMAs on DNA methylation-silenced tumor suppressor genes, which may foster novel strategies for prostate cancer therapy.
authors.affiliation: Division of Medicinal Chemistry, College of Pharmacy, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Hsiang-Yu
authors.initials: HY
authors.lastname: Lin
authors.forename: Yi-Chiu
authors.initials: YC
authors.lastname: Kuo
authors.forename: Yu-I
authors.initials: YI
authors.lastname: Weng
authors.forename: I-Lu
authors.initials: IL
authors.lastname: Lai
authors.forename: Tim H-M
authors.initials: TH
authors.lastname: Huang
authors.forename: Shuan-Pei
authors.initials: SP
authors.lastname: Lin
authors.forename: Dau-Ming
authors.initials: DM
authors.lastname: Niu
authors.forename: Ching-Shih
authors.initials: CS
authors.lastname: Chen
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D045744:Cell Line, Tumor; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics*; D019175:DNA Methylation / Q000187:drug effects; D000077209:Decitabine; D003847:Deoxyglucose / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D020868:Gene Silencing / Q000187:drug effects; D016147:Genes, Tumor Suppressor / Q000187:drug effects*; D006801:Humans; D008297:Male; D011467:Prostate / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D015533:Transcriptional Activation / Q000187:drug effects
chemical_list: D000964:Antimetabolites, Antineoplastic; D000077209:Decitabine; D003847:Deoxyglucose; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human; D001374:Azacitidine