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Inhibition of euchromatic histone methyltransferase 1 and 2 sensitizes chronic myeloid leukemia cells to interferon treatment.

Loh SW, Ng WL, Yeo KS, Lim YY, Ea CK - PLoS ONE (2014)

Bottom Line: Chromatin immunoprecipitation assay shows that BIX01294 treatment enhances type I interferon response by reducing H3K9me2 at the promoters of interferon-stimulated genes.Moreover, our data suggest that the expression level of EHMT1 and EHMT2 inversely correlates with the type I interferon responsiveness in CML cell lines.Our study sheds light on the role of EHMT1 and EHMT2 as potential targets in improving the efficacy of standard treatments of CML.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia.

ABSTRACT

Background: H3K9 methylation is one of the essential histone post-translational modifications for heterochromatin formation and transcriptional repression. Recently, several studies have demonstrated that H3K9 methylation negatively regulates the type I interferon response.

Results: We report the application of EHMT1 and EHMT2 specific chemical inhibitors to sensitize CML cell lines to interferon and imatinib treatments. Inhibition of EHMT1 and EHMT2 with BIX01294 enhances the cytotoxicity of IFNα2a in four CML cell lines, K562, KCL22, BV173 and KT1 cells. Chromatin immunoprecipitation assay shows that BIX01294 treatment enhances type I interferon response by reducing H3K9me2 at the promoters of interferon-stimulated genes. Additionally, BIX01294 treatment augments IFNα2a- and imatinib-mediated apoptosis in CML cell lines. Moreover, our data suggest that the expression level of EHMT1 and EHMT2 inversely correlates with the type I interferon responsiveness in CML cell lines.

Conclusions: Our study sheds light on the role of EHMT1 and EHMT2 as potential targets in improving the efficacy of standard treatments of CML.

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Related in: MedlinePlus

BIX01294 enhances imatinib- and IFNα2a-induced apoptosis in K562 cells.(A) K562 cells were cultured with various concentrations of BIX01294 and imatinib as indicated. After four days, cell proliferation was measured with a MTT assay. Results represent the mean ± SD in quadruplicate experiments. (B) K562 cells were treated with or without IFNα2a (15 k IU/ml), or imatinib (150 nM) in the presence or absence of BIX01294 (2 µM) for 2 days. Cells were washed with PBS and fixed with 70% ethanol. Fixed cells were then stained with PI and analyzed with FACS. (C) K562 cells were stimulated with or without IFNα2a (10 k IU/ml), or imatinib (75 nM) in the presence or absence of BIX01294 (2 µM) for 2 days. Whole cell extracts were prepared and subjected to immunoblotting using the indicated antibodies.
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pone-0103915-g006: BIX01294 enhances imatinib- and IFNα2a-induced apoptosis in K562 cells.(A) K562 cells were cultured with various concentrations of BIX01294 and imatinib as indicated. After four days, cell proliferation was measured with a MTT assay. Results represent the mean ± SD in quadruplicate experiments. (B) K562 cells were treated with or without IFNα2a (15 k IU/ml), or imatinib (150 nM) in the presence or absence of BIX01294 (2 µM) for 2 days. Cells were washed with PBS and fixed with 70% ethanol. Fixed cells were then stained with PI and analyzed with FACS. (C) K562 cells were stimulated with or without IFNα2a (10 k IU/ml), or imatinib (75 nM) in the presence or absence of BIX01294 (2 µM) for 2 days. Whole cell extracts were prepared and subjected to immunoblotting using the indicated antibodies.

Mentions: CML is a unique disease, universally characterized by the presence of BCR-ABL fusion genes, which encodes a constitutively active tyrosine kinase, and is considered responsible for the pathogenesis of CML [15]. Imatinib (Gleevec) is the first BCR-ABL specific tyrosine kinase inhibitor approved by the FDA for treating CML [16]. To test if inhibition of EHMT1 and EHMT2 enhances the anticancer effect of imatinib in CML, we investigated the cytotoxicity of imatinib in the presence or absence of BIX01294. We demonstrated that K562 cells were very sensitive to imatinib treatment in that 150 nM of imatinib reduced the proliferation of K562 cells by 57% (Figure 6A). More importantly, treating K562 cells with imatinib together with BIX01294 significantly enhanced the anti-proliferation effect of imatinib (Figure 6A). Additionally, imatinib treatment reduced the mRNA and protein level of BCR-ABL while BIX01294 or IFNα2a treatment did not (Figure S2a and b). However, treating K562 cells together with BIX01294 and imatinib did not further reduce the mRNA and protein level of BCR-ABL. These results suggest that inhibition of EHMT1 and EHMT2 sensitizes CML cells to imatinib treatment.


Inhibition of euchromatic histone methyltransferase 1 and 2 sensitizes chronic myeloid leukemia cells to interferon treatment.

Loh SW, Ng WL, Yeo KS, Lim YY, Ea CK - PLoS ONE (2014)

BIX01294 enhances imatinib- and IFNα2a-induced apoptosis in K562 cells.(A) K562 cells were cultured with various concentrations of BIX01294 and imatinib as indicated. After four days, cell proliferation was measured with a MTT assay. Results represent the mean ± SD in quadruplicate experiments. (B) K562 cells were treated with or without IFNα2a (15 k IU/ml), or imatinib (150 nM) in the presence or absence of BIX01294 (2 µM) for 2 days. Cells were washed with PBS and fixed with 70% ethanol. Fixed cells were then stained with PI and analyzed with FACS. (C) K562 cells were stimulated with or without IFNα2a (10 k IU/ml), or imatinib (75 nM) in the presence or absence of BIX01294 (2 µM) for 2 days. Whole cell extracts were prepared and subjected to immunoblotting using the indicated antibodies.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4117596&req=5

pone-0103915-g006: BIX01294 enhances imatinib- and IFNα2a-induced apoptosis in K562 cells.(A) K562 cells were cultured with various concentrations of BIX01294 and imatinib as indicated. After four days, cell proliferation was measured with a MTT assay. Results represent the mean ± SD in quadruplicate experiments. (B) K562 cells were treated with or without IFNα2a (15 k IU/ml), or imatinib (150 nM) in the presence or absence of BIX01294 (2 µM) for 2 days. Cells were washed with PBS and fixed with 70% ethanol. Fixed cells were then stained with PI and analyzed with FACS. (C) K562 cells were stimulated with or without IFNα2a (10 k IU/ml), or imatinib (75 nM) in the presence or absence of BIX01294 (2 µM) for 2 days. Whole cell extracts were prepared and subjected to immunoblotting using the indicated antibodies.
Mentions: CML is a unique disease, universally characterized by the presence of BCR-ABL fusion genes, which encodes a constitutively active tyrosine kinase, and is considered responsible for the pathogenesis of CML [15]. Imatinib (Gleevec) is the first BCR-ABL specific tyrosine kinase inhibitor approved by the FDA for treating CML [16]. To test if inhibition of EHMT1 and EHMT2 enhances the anticancer effect of imatinib in CML, we investigated the cytotoxicity of imatinib in the presence or absence of BIX01294. We demonstrated that K562 cells were very sensitive to imatinib treatment in that 150 nM of imatinib reduced the proliferation of K562 cells by 57% (Figure 6A). More importantly, treating K562 cells with imatinib together with BIX01294 significantly enhanced the anti-proliferation effect of imatinib (Figure 6A). Additionally, imatinib treatment reduced the mRNA and protein level of BCR-ABL while BIX01294 or IFNα2a treatment did not (Figure S2a and b). However, treating K562 cells together with BIX01294 and imatinib did not further reduce the mRNA and protein level of BCR-ABL. These results suggest that inhibition of EHMT1 and EHMT2 sensitizes CML cells to imatinib treatment.

Bottom Line: Chromatin immunoprecipitation assay shows that BIX01294 treatment enhances type I interferon response by reducing H3K9me2 at the promoters of interferon-stimulated genes.Moreover, our data suggest that the expression level of EHMT1 and EHMT2 inversely correlates with the type I interferon responsiveness in CML cell lines.Our study sheds light on the role of EHMT1 and EHMT2 as potential targets in improving the efficacy of standard treatments of CML.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia.

ABSTRACT

Background: H3K9 methylation is one of the essential histone post-translational modifications for heterochromatin formation and transcriptional repression. Recently, several studies have demonstrated that H3K9 methylation negatively regulates the type I interferon response.

Results: We report the application of EHMT1 and EHMT2 specific chemical inhibitors to sensitize CML cell lines to interferon and imatinib treatments. Inhibition of EHMT1 and EHMT2 with BIX01294 enhances the cytotoxicity of IFNα2a in four CML cell lines, K562, KCL22, BV173 and KT1 cells. Chromatin immunoprecipitation assay shows that BIX01294 treatment enhances type I interferon response by reducing H3K9me2 at the promoters of interferon-stimulated genes. Additionally, BIX01294 treatment augments IFNα2a- and imatinib-mediated apoptosis in CML cell lines. Moreover, our data suggest that the expression level of EHMT1 and EHMT2 inversely correlates with the type I interferon responsiveness in CML cell lines.

Conclusions: Our study sheds light on the role of EHMT1 and EHMT2 as potential targets in improving the efficacy of standard treatments of CML.

Show MeSH
Related in: MedlinePlus