Zebularine induces chemosensitization to methotrexate and efficiently decreases AhR gene methylation in childhood acute lymphoblastic leukemia cells

Departments of aGenetics bPediatrics, Ribeirão Preto Medical School, University of São Paulo (USP), Ribeirão Preto, SP, Brazil.
Anti-cancer drugs (Impact Factor: 1.78). 09/2013; 25(1). DOI: 10.1097/CAD.0000000000000028
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Acute lymphoblastic leukemia (ALL) is the most common hematologic malignancy in childhood. Despite the advances in treatment, about 20% of patients relapse and/or die, indicating the need for different therapies for this group. Zebularine (ZB) is a potent DNA methyltransferase (DNMT) inhibitor and has been associated with gene demethylation and enhancement of tumor chemosensitivity. This study aimed to evaluate the effects of ZB, alone or combined with chemotherapeutics (methotrexate and vincristine), on childhood ALL cell lines. Cell proliferation, apoptosis, and clonogenic capacity were studied in Jurkat and ReH cell lines. Bisulfite modification, followed by methylation-specific PCR was carried out to evaluate aryl hydrocarbon receptor (AhR) methylation status. Gene expression of DNMT1, DNMT3a, DNMT3b, and AhR was assessed using qRT-PCR. Both cell cultures were sensitive to ZB, showing a dose-dependent and time-dependent response (P<0.05). ZB induced apoptosis and decreased clonogenic capacity in both cell lines. Combination with methotrexate resulted in a strong synergistic effect, whereas combination with vincristine led to an antagonistic response in both cell lines. ZB treatment decreased gene expression of the three DNMTs and induced AhR gene promoter demethylation and its re-expression. These results indicate that ZB may be a promising drug for the adjuvant treatment of ALL, mainly when combined with methotrexate.

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Available from: Angel Mauricio Castro-Gamero, Oct 08, 2015
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    • "However, epigenetic changes are reversible, in contrast to gene mutations, and there is a potential to reverse gene silencing using DNA methyltransferase (DNMT) inhibitors, which are drugs that prevent hypermethylation by irreversibly binding to the active site of DNMT [43]. These drugs are effective as monotherapy for hematologic malignancy [44, 45], but not in solid cancer. However, effects on solid cancer are likely to be found in combination with other drugs. "
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