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Importance of dose-schedule of 5-aza-2'-deoxycytidine for epigenetic therapy of cancer.

ABSTRACT: BACKGROUND: The inactivation of tumor suppressor genes (TSGs) by aberrant DNA methylation plays an important role in the development of malignancy. Since this epigenetic change is reversible, it is a potential target for chemotherapeutic intervention using an inhibitor of DNA methylation, such as 5-aza-2'-deoxycytidine (DAC). Although clinical studies show that DAC has activity against hematological malignancies, the optimal dose-schedule of this epigenetic agent still needs to be established. METHODS: Clonogenic assays were performed on leukemic and tumor cell lines to evaluate the in vitro antineoplastic activity of DAC. The reactivation of TSGs and inhibition of DNA methylation by DAC were investigated by reverse transcriptase-PCR and Line-1 assays. The in vivo antineoplastic activity of DAC administered as an i.v. infusion was evaluated in mice with murine L1210 leukemia by measurement of survival time, and in mice bearing murine EMT6 mammary tumor by excision of tumor after chemotherapy for an in vitro clonogenic assay. RESULTS: Increasing the DAC concentration and duration of exposure produced a greater loss of clonogenicity for both human leukemic and tumor cell lines. The reactivation of the TSGs (p57KIP2 in HL-60 leukemic cells and p16CDKN2A in Calu-6 lung carcinoma cells) and the inhibition of global DNA methylation in HL-60 leukemic cells increased with DAC concentration. In mice with L1210 leukemia and in mice bearing EMT6 tumors, the antineoplastic action of DAC also increased with the dose. The plasma level of DAC that produced a very potent antineoplastic effect in mice with leukemia or solid tumors was > 200 ng/ml (> 1 microM). CONCLUSION: We have shown that intensification of the DAC dose markedly increased its antineoplastic activity in mouse models of cancer. Our data also show that there is a good correlation between the concentrations of DAC that reduce in vitro clonogenicity, reactivate TSGs and inhibit DNA methylation. These results suggest that the antineoplastic action of DAC is related to its epigenetic action. Our observations provide a strong rationale to perform clinical trials using dose intensification of DAC to maximize the chemotherapeutic potential of this epigenetic agent in patients with cancer.

SUBMITTER: Lemaire M

PROVIDER: S-EPMC2386792 | biostudies-literature | 2008

REPOSITORIES: biostudies-literature

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Importance of dose-schedule of 5-aza-2'-deoxycytidine for epigenetic therapy of cancer.

Lemaire Maryse M Chabot Guy G GG Raynal Noël Jm NJ Momparler Louise F LF Hurtubise Annie A Bernstein Mark L ML Momparler Richard L RL

BMC cancer 20080502

<h4>Background</h4>The inactivation of tumor suppressor genes (TSGs) by aberrant DNA methylation plays an important role in the development of malignancy. Since this epigenetic change is reversible, it is a potential target for chemotherapeutic intervention using an inhibitor of DNA methylation, such as 5-aza-2'-deoxycytidine (DAC). Although clinical studies show that DAC has activity against hematological malignancies, the optimal dose-schedule of this epigenetic agent still needs to be establi ...[more]

PMID: 18454857

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Project description:BackgroundThe silencing of tumor suppressor genes (TSGs) by aberrant DNA methylation occurs frequently in acute myeloid leukemia (AML). This epigenetic alteration can be reversed by 5-aza-2'-deoxcytidine (decitabine, 5-AZA-CdR). Although 5-AZA-CdR can induce complete remissions in patients with AML, most patients relapse. The effectiveness of this therapy may be limited by the inability of 5-AZA-CdR to reactivate all TSGs due to their silencing by other epigenetic mechanisms such as histone methylation or chromatin compaction. EZH2, a subunit of the polycomb repressive complex 2, catalyzes the methylation of histone H3 lysine 27 (H3K27) to H3K27me3. 3-Deazaneplanocin-A (DZNep), an inhibitor of methionine metabolism, can reactivate genes silenced by H3K27me3 by its inhibition of EZH2. In a previous report, we observed that 5-AZA-CdR, in combination with DZNep, shows synergistic antineoplastic action against AML cells. Gene silencing due to chromatin compaction is attributable to the action of histone deacetylases (HDAC). This mechanism of epigenetic gene silencing can be reversed by HDAC inhibitors such as trichostatin-A (TSA). Silent TSGs that cannot be reactivated by 5-AZA-CdR or DZNep have the potential to be reactivated by TSA. This provides a rationale for the use of HDAC inhibitors in combination with 5-AZA-CdR and DZNep to treat AML.ResultsThe triple combination of 5-AZA-CdR, DZNep, and TSA induced a remarkable synergistic antineoplastic effect against human AML cells as demonstrated by an in vitro colony assay. This triple combination also showed a potent synergistic activation of several key TSGs as determined by real-time PCR. The triple combination was more effective than the combination of two agents or a single agent. Microarray analysis showed that the triple combination generated remarkable changes in global gene expression.ConclusionsOur data suggest that it may be possible to design a very effective therapy for AML using agents that target the reversal of the following three epigenetic "lock" mechanisms that silence gene expression: DNA methylation, histone methylation, and histone deacetylation. This approach merits serious consideration for clinical investigation in patients with advanced AML.

Project description:Background:Aberrant DNA methylation that silences tumor suppressor genes occurs frequently in patients with acute myeloid leukemia (AML). Treatment of AML patients with the inhibitor of DNA methylation, 5-aza-2'-deoxycytidine (5-AZA-CdR) can induce complete remissions, but most patients will relapse. The clinical efficacy of 5-AZA-CdR may be influenced by its limited capacity to activate tumor suppressor genes silenced by methylation of lysine 27 histone H3 (H3K27) by EZH2. In order to overcome this limitation, we investigated previously the antileukemic action of 5-AZA-CdR in combination with the EZH2 inhibitor, 3-deazaneplanocin A (DZNep) on HL-60 AML cells. We observed a remarkable synergistic interaction against these AML cells for this combination. In this study, we investigated in more depth the action of 5-AZA-CdR plus DZNep on gene expression in AML cells using RNA sequence analysis Result:In a colony assay, 5-AZA-CdR in combination with DZNep exhibited also a potent synergy against another human AML cell line: AML-3. The induction of apoptosis in HL-60 and AML3 leukemic cells by 5-AZA-CdR plus DZNep was also synergistic. RNA sequence analysis on HL-60 leukemic cells showed that the combination of 5-AZA-CdR plus DZNep increased the expression of thousands of genes. The genes upregulated by this combination included genes related to differentiation, development, senescence, apoptosis, and tumor suppressor function. Many of the genes activated by 5-AZA-CdR plus DZNep have the potential to suppress leukemogenesis. Conclusion: The activation of many genes by the combination of 5-AZA-CdR plus DZNep correlates with its synergistic antileukemic action. The block in differentiation is one of the hallmarks of AML.The activation of many genes that program differentiation and development by this combination of epigenetic agents has the potential to reverse this block. The reversal of these two epigenetic genesilencing mechanisms by 5-AZA-CdR plus DZNep merits clinical investigation in patients with AML

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Importance of dose-schedule of 5-aza-2'-deoxycytidine for epigenetic therapy of cancer.

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Importance of dose-schedule of 5-aza-2'-deoxycytidine for epigenetic therapy of cancer.

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