Limited Gene Activation in Tumor and Normal Epithelial Cells Treated with the DNA Methyltransferase Inhibitor 5-Aza-2′-deoxycytidine

Abstract

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-2Ј-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.

Inhibiting DNA Methylation Causes an Interferon Response in Cancer via dsRNA Including Endogenous Retroviruses

“…A long recognized activity of DNMTis described by others (Karpf et al, 2004;Karpf et al, 1999), and our group Wrangle et al, 2013), is induction of immune responses in cancer cells. In recent clinical trials for non-small cell lung cancer (NSCLC) (Juergens et al, 2011;Wrangle et al, 2013) a small number of patients had remarkably robust and durable responses to immune checkpoint blockade therapy after first receiving Aza (Wrangle et al, 2013).…”

Combined inhibition of DNA methylation and histone acetylation enhances gene re-expression and drug sensitivity in vivo

“…As the aim was to combine the epigenetic therapies with a cytotoxic drug we have intentionally used low, non-toxic doses of the agents. Although decitabine treatment results in a reduced MAGE-A1 methylation in PBMCs the gene is not re-expressed and this may be due to a lack of the necessary transcriptional activators (Karpf et al, 2004). Few studies have examined the effects of demethylating agents on normal cells; however, there is some evidence that fewer genes become demethylated than in tumour cells (Liang et al, 2002).…”

Non-intensive treatment with low-dose 5-aza-2′-deoxycytidine (DAC) prior to allogeneic blood SCT of older MDS/AML patients

“…Interestingly, microarray studies show that the transcriptome of untransformed cells is changed only to a minor degree by these drugs compared to malignant cells. 17 The good feasibility is supportive of the use of low-dose azanucleosides also after allogeneic transplantation, either at hematologic relapse 18,19 or even pre-emptively in highrisk patients. 20 DAC pretreatment can induce improvement or even remission of MDS/AML with negligible nonhematopoietic toxicity, thus effectively bridging the time of donor search prior to allografting.…”