title: DNMT1 and DNMT3b silencing sensitizes human hepatoma cells to TRAIL-mediated apoptosis via up-regulation of TRAIL-R2/DR5 and caspase-8.
abstract: DNA methylation plays a critical role in chromatin remodeling and gene expression. DNA methyltransferases (DNMTs) are hypothesized to mediate cellular DNA methylation status and gene expression during mammalian development and in malignant diseases. In this study, we examined the role of DNA methyltransferase 1 (DNMT1) and DNMT3b in cell proliferation and survival of hepatocellular carcinoma (HCC) cells. Gene silencing of both DNMT1 and DNMT3b by targeted siRNA knockdown reduces cell proliferation and sensitizes the cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated cell death. The proapoptotic protein caspase-8 demonstrated promoter hypermethylation in HCC cells and was up-regulated by knockdown of DNMT1 and DNMT3b both at mRNA and protein levels. In addition, death receptor TRAIL-R2/DR5 (TRAIL receptor 2/death receptor 5) did not exhibit promoter hypermethylation in HCC cells but was also up-regulated by knockdown of DNMT1 and DNMT3b both at mRNA and protein levels. Consistent with this observation, the combined transfection of DNMT1-siRNA plus DNMT3b-siRNA enhanced formation of the TRAIL-death-inducing signaling complex formation in HCC cells. In conclusion, our data suggest that DNA methylation of specific genomic regions maintained by DNMT1 and DNMT3b plays a critical role in survival of HCC cells, and a simultaneous knockdown of both DNMT1 and DNMT3b may be a novel anticancer strategy for the treatment of HCC.
authors.affiliation: Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan. kurita.satoshi@mayo.edu
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kurita
authors.forename: Hajime
authors.initials: H
authors.lastname: Higuchi
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Saito
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Nakamoto
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Takaishi
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Tada
authors.forename: Hidetsugu
authors.initials: H
authors.lastname: Saito
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Gores
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Hibi
mesh_terms: D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000473:pathology; D053181:Caspase 8 / Q000235:genetics*; D045744:Cell Line, Tumor; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D019175:DNA Methylation; D019008:Drug Resistance, Neoplasm; D020868:Gene Silencing; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000473:pathology; D024101:Mitochondrial Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D034741:RNA, Small Interfering / Q000235:genetics; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000235:genetics* / Q000502:physiology; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D015854:Up-Regulation; D000097584:DNA Methyltransferase 3B
chemical_list: D053181:Caspase 8; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; D024101:Mitochondrial Proteins; D034741:RNA, Small Interfering; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053221:TNF-Related Apoptosis-Inducing Ligand; D000097584:DNA Methyltransferase 3B; C503369:GRAMD4 protein, human; C000619380:DNMT1 protein, human
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