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Improved DNA methylation analysis via enrichment of demethylated cells expressing an X-inactivated GFP transgene

ABSTRACT: The demethylating drug 5-aza-2’-deoxycytidine (5-aza-2dC) is frequently used to investigate the effect of global DNA demethylation on gene expression in cultured mammalian cells. Here, we utilize a novel method that uses the reactivation of an X-inactivated GFP transgene as a marker to enrich for cells that have undergone drug-induced demethylation. By combining it with microarray gene expression profiling, we demonstrate the method’s utility in identifying genes activated by global DNA demethylation. Keywords: 5-aza-2'-deoxycytidine; methylation; dermal fibroblast; X-linked GFP

ORGANISM(S): Mus musculus

PROVIDER: GSE4718 | GEO | 2006/04/27

SECONDARY ACCESSION(S): PRJNA95607

REPOSITORIES: GEO

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Project description:Silencing of genes that suppress the malignant phenotype by DNA methylation spurred an interest in the clinical use of epigenetic reprogramming agents. Single therapy is unlikely to be curative in the context of a heterogeneous disease such as Diffuse Large B cell Lymphomas (DLBCL). The combination of DNA demethylating drugs could increase the chance to respond to classical and new treatments. We found that DLBCL cell lines respond heterogeneously to DNA demethylating agents. In sensitive cell lines, 5-aza-2’-deoxycytidine induced a genomic signature similar to that of doxorubicin, the most important drug of the combinatorial chemotherapy regimen for DLBCL treatment. Accordingly, the combination of 5-aza-2’-deoxycytidine and doxorubicin proved to be synergistic in cell killing in vitro and in vivo for DLBCL cell lines individually responsive to these drugs. In doxorubicin resistant cell lines, long-term exposure to low-dose of 5-aza-2’-deoxycytidine induces DNA demethylation and subsequent doxorubicin sensitization in vitro and in vivo. This later effect correlates with SMAD1 demethylation. SMAD1 is epigenetically silenced in doxorubicin-resistant DLBCL cells and DLBCL patients with poor prognostic. In addition, we found that DNA demethylating agents can sensitize primary DLBCL cells to doxorubicin. Primary cells obtained from a DLBCL patient treated with 5-azacytidine shows SMAD1 demethylation and ex vivo sensitization to multiple drugs. Therefore, DNA demethylating drugs can reprogram otherwise resistant DLBCL cells to respond to chemotherapy agents without increasing the toxicity to normal tissues. Our data also indicate that DNA methylation and consequent suppression of SMAD1 expression represent a previously undescribed molecular mechanism of chemoresistance in DLBCL that can be further exploit for therapy. A microarray study using genomic DNA from different DLBCL cell lines before any treatment. Two to four biological replicates by cell line. The HELP data wil be used to find genes hypermethylated in resistant cell lines compared to sensitive cell lines to doxorubicin and other drugs.

Project description:Silencing of genes that suppress the malignant phenotype by DNA methylation spurred an interest in the clinical use of epigenetic reprogramming agents. Single therapy is unlikely to be curative in the context of a heterogeneous disease such as Diffuse Large B cell Lymphomas (DLBCL). The combination of DNA demethylating drugs could increase the chance to respond to classical and new treatments. We found that DLBCL cell lines respond heterogeneously to DNA demethylating agents. In sensitive cell lines, 5-aza-2M-bM-^@M-^Y-deoxycytidine induced a genomic signature similar to that of doxorubicin, the most important drug of the combinatorial chemotherapy regimen for DLBCL treatment. Accordingly, the combination of 5-aza-2M-bM-^@M-^Y-deoxycytidine and doxorubicin proved to be synergistic in cell killing in vitro and in vivo for DLBCL cell lines individually responsive to these drugs. In doxorubicin resistant cell lines, long-term exposure to low-dose of 5-aza-2M-bM-^@M-^Y-deoxycytidine induces DNA demethylation and subsequent doxorubicin sensitization in vitro and in vivo. This later effect correlates with SMAD1 demethylation. SMAD1 is epigenetically silenced in doxorubicin-resistant DLBCL cells and DLBCL patients with poor prognostic. In addition, we found that DNA demethylating agents can sensitize primary DLBCL cells to doxorubicin. Primary cells obtained from a DLBCL patient treated with 5-azacytidine shows SMAD1 demethylation and ex vivo sensitization to multiple drugs. Therefore, DNA demethylating drugs can reprogram otherwise resistant DLBCL cells to respond to chemotherapy agents without increasing the toxicity to normal tissues. Our data also indicate that DNA methylation and consequent suppression of SMAD1 expression represent a previously undescribed molecular mechanism of chemoresistance in DLBCL that can be further exploit for therapy. A microarray study using double-stranded cDNA from different DLBCL cell lines before any treatment. Two biological replicates by cell line. The gene expression will be used to find gene expression signatures between sensitive and resistant cell lines to chemotherapeutics.

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Improved DNA methylation analysis via enrichment of demethylated cells expressing an X-inactivated GFP transgene

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