Abstract
Abstract This study found that long-term exposure of chronic myelogenous leukemia (CML) K562 cells to BCR/ABL thyrosine kinase inhibirors (TKIs) caused drug-resistance in association with an increase in levels of DNA methyltransferases (DNMTs) and a decrease in levels of microRNAs (miRNAs) miR-217. These observations are clinically relevant; an increase in levels of DNMT3A in association with downregulation of miR-217 were noted in leukemia cells isolated from individuals with BCR/ABL TKI-resistant philadelphia chromosome positive acute lymphoblastic leukemia (Ph+ ALL) and CML. Further studies with TKI-resistant K562 cells found that forced expression of miR-217 inhibited expression of DNMT3A through a miR-217-binding site within the 3′-untranslated region of DNMT3A and sensitized these cells to growth inhibition mediated by the TKI. Of note, long-term exposure of K562 cells to dasatinib (10 nM) together with 5-Aza-2′-deoxycytidine (5-AzadC) (0.1 μM) potently inhibited proliferation of these cells in association with upregulation of miR-217 and downregulation of DNMT3A in vitro. In addition, a decrease in levels of DNMT3A and an increase in levels of miR-217 were noted in K562 tumors growing in immune deficient mice that were treated by the combination of 5-AzadC and dasatinib. Taken together, Ph+ leukemia cells acquire TKI-resistance via downregulation of miR-217 and upregulation of DNMT3A. Inhibition of DNMT3A by forced expression of miR-217 or 5-AzadC may be useful to prevent drug resistance in individuals who receive TKIs. Citation Format: Takayuki Ikezoe, Chie Nishioka, Jing Yang, Akihito Yokoyama. Downregulation of miR-217 correlates with resistance of ph+ leukemia cells to ABL tyrosine kinase inhibitors. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1717. doi:10.1158/1538-7445.AM2014-1717
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