title: Overcoming resistance to interferon-induced apoptosis of renal carcinoma and melanoma cells by DNA demethylation.
abstract: Epigenetic editing of gene expression by aberrant methylation of DNA may help tumor cells escape attack from the innate and acquired immune systems. Resistance to antiproliferative effects and apoptosis induction by interferons (IFNs) was postulated to result from silencing of IFN response genes by promoter hypermethylation. Treatment of human ACHN renal cell carcinoma (RCC) and A375 melanoma cells with the DNA demethylating nucleoside analog 5-AZA-2'-deoxycytidine (5-AZA-dC) synergistically augmented antiproliferative effects of IFN- alpha (alpha) 2 and IFN-beta (beta). Either 5-AZA-dC or an antisense to DNA methyltransferase 1 (DNMT1) overcame resistance to apoptosis induction by IFNs with up to 85% apoptotic cells resulting from the combinations. No similar potentiation occurred in normal kidney epithelial cells. IFN response genes were augmented more than 10 times in expression by 5-AZA-dC. Demethylation by 5-AZA-dC of the promoter of the prototypic, apoptosis-associated IFN response gene XAF1 was confirmed by methylation-specific polymerase chain reaction. siRNA to XAF1 inhibited IFN-induced apoptosis; conversely, overexpression of XAF1 overcame resistance to apoptosis induction by IFN-beta. As occurred with apoptosis-resistant melanoma cells in vitro, tumor growth inhibition in the nude mouse of human A375 melanoma xenografts resulted from treatment with 5-AZA-dC in combination with IFN-beta, an effect not resulting from either single agent. The importance of epigenetic remodeling of expression of immune-modifying genes in tumor cells was further suggested by identifying reactivation of the cancer-testis antigens MAGE and RAGE in ACHN cells after DNMT1 depletion. Thus, inhibitors of DNMT1 may have clinical relevance for immune modulation by augmentation of cytokine effects and/or expression of tumor-associated antigens.
authors.affiliation: Taussig Cancer Center, Cleveland Clinic Foundation, Cleveland, OH 44195, USA.
authors.forename: Frederic J
authors.initials: FJ
authors.lastname: Reu
authors.forename: Soo In
authors.initials: SI
authors.lastname: Bae
authors.forename: Leonid
authors.initials: L
authors.lastname: Cherkassky
authors.forename: Douglas W
authors.initials: DW
authors.lastname: Leaman
authors.forename: Daniel
authors.initials: D
authors.lastname: Lindner
authors.forename: Normand
authors.initials: N
authors.lastname: Beaulieu
authors.forename: A Robert
authors.initials: AR
authors.lastname: MacLeod
authors.forename: Ernest C
authors.initials: EC
authors.lastname: Borden
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D015153:Blotting, Western; D002292:Carcinoma, Renal Cell / Q000188:drug therapy* / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000187:drug effects / Q000378:metabolism; D019175:DNA Methylation / Q000187:drug effects*; D015254:DNA Modification Methylases / Q000494:pharmacology; D000077209:Decitabine; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D004357:Drug Synergism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D016898:Interferon-alpha / Q000494:pharmacology; D016899:Interferon-beta / Q000494:pharmacology; D007372:Interferons / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins; D007680:Kidney Neoplasms / Q000188:drug therapy; D008546:Melanoma, Experimental / Q000188:drug therapy* / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D009363:Neoplasm Proteins / Q000235:genetics*; D016133:Polymerase Chain Reaction; D014183:Transplantation, Heterologous; D015854:Up-Regulation
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000964:Antimetabolites, Antineoplastic; D051017:Apoptosis Regulatory Proteins; D016898:Interferon-alpha; D047908:Intracellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins; C417551:XAF1 protein, human; D016899:Interferon-beta; D000077209:Decitabine; D007372:Interferons; D015254:DNA Modification Methylases; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human; C000619381:Dnmt1 protein, mouse; D001374:Azacitidine