Limited gene activation in tumor and normal epithelial cells treated with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine.
It remains unclear to what extent drugs targeting transcriptional repressor complexes affect global gene expression in cells derived from target and nontarget human tissues. To address this question, we used genome-wide expression analysis using microarrays to analyze the response of three tumor and one normal epithelial cell line to treatment with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (5-aza-CdR). Notably, we found that 5-aza-CdR treatment induced a limited number of genes (mean, 0.67%; range, 0.17-1.8% of 25,940 genes screened) in each cell line tested. The majority of the gene expression changes that followed 5-aza-CdR treatment were conserved in tumor and normal cells, including genes that function in cell proliferation, differentiation, immune presentation, and cytokine signaling. In contrast, 5-aza-CdR treatment induced the expression of cancer-testis class tumor antigens only in tumor cell lines. To explain this tissue-specific response, we analyzed the mechanism of transcriptional regulation of the prototype member of this tumor antigen gene family, MAGE-1. Taken from our analysis of MAGE-1 gene regulation, we propose that 5-aza-CdR-mediated gene activation has two distinct requirements: 1) the reversal of promoter hypermethylation, and 2) the presence of transcriptional activators competent for the activation of hypomethylated target promoters. This latter requirement for gene activation by 5-aza-CdR is probably mediated by sequence-specific transcription factors and may account for the limited number of human genes induced by 5-aza-CdR treatment. This revised model for gene activation by 5-aza-CdR has important implications for the use of DNA methyltransferase inhibitors in clinical settings.
Karpf
Adam R
AR
Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112, USA.
Lasek
Amy W
AW
Ririe
Ted O
TO
Hanks
Adrianne N
AN
Grossman
Douglas
D
Jones
David A
DA
D000951:Antigens, Neoplasm; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D045744:Cell Line, Tumor; D019175:DNA Methylation; D015254:DNA Modification Methylases / Q000037:antagonists & inhibitors*; D000077209:Decitabine; D004847:Epithelial Cells / Q000187:drug effects* / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D008544:Melanocytes / Q000187:drug effects / Q000502:physiology; D008545:Melanoma / Q000473:pathology; D058950:Melanoma-Specific Antigens; D005810:Multigene Family / Q000187:drug effects; D009363:Neoplasm Proteins / Q000235:genetics; D015533:Transcriptional Activation
D000951:Antigens, Neoplasm; D000964:Antimetabolites, Antineoplastic; C072011:MAGEA1 protein, human; D058950:Melanoma-Specific Antigens; D009363:Neoplasm Proteins; D000077209:Decitabine; D015254:DNA Modification Methylases; D001374:Azacitidine