Regulation of hTERT by BCR-ABL at multiple levels in K562 cells

<p>Abstract</p> <p>Background</p> <p>The cytogenetic characteristic of Chronic Myeloid Leukemia (CML) is the formation of the Philadelphia chromosome gene product, BCR-ABL. Given that BCR-ABL is the specific target of Gleevec in CML treatment, we investigated the regula...

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Main Authors: Chai Juin Hsien, Zhang Yong, Tan Wei Han, Chng Wee Joo, Li Baojie, Wang Xueying
Format: Article
Language:English
Published: BMC 2011-12-01
Series:BMC Cancer
Online Access:http://www.biomedcentral.com/1471-2407/11/512
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spelling doaj-6833c9b8284b4487aae803d744d7bc692020-11-25T02:28:17ZengBMCBMC Cancer1471-24072011-12-0111151210.1186/1471-2407-11-512Regulation of hTERT by BCR-ABL at multiple levels in K562 cellsChai Juin HsienZhang YongTan Wei HanChng Wee JooLi BaojieWang Xueying<p>Abstract</p> <p>Background</p> <p>The cytogenetic characteristic of Chronic Myeloid Leukemia (CML) is the formation of the Philadelphia chromosome gene product, BCR-ABL. Given that BCR-ABL is the specific target of Gleevec in CML treatment, we investigated the regulation of the catalytic component of telomerase, hTERT, by BCR-ABL at multiple levels in K562 cells.</p> <p>Methods</p> <p>Molecular techniques such as over expression, knockdown, real-time PCR, immunoprecipitation, western blotting, reporter assay, confocal microscopy, telomerase assays and microarray were used to suggest that hTERT expression and activity is modulated by BCR-ABL at multiple levels.</p> <p>Results</p> <p>Our results suggest that BCR-ABL plays an important role in regulating hTERT in K562 (BCR-ABL positive human leukemia) cells. When Gleevec inhibited the tyrosine kinase activity of BCR-ABL, phosphorylation of hTERT was downregulated, therefore suggesting a positive correlation between BCR-ABL and hTERT. Gleevec treatment inhibited <it>hTERT </it>at mRNA level and significantly reduced telomerase activity (TA) in K562 cells, but not in HL60 or Jurkat cells (BCR-ABL negative cells). We also demonstrated that the transcription factor STAT5a plays a critical role in <it>hTERT </it>gene regulation in K562 cells. Knockdown of STAT5a, but not STAT5b, resulted in a marked downregulation of <it>hTERT </it>mRNA level, TA and hTERT protein level in K562 cells. Furthermore, translocation of hTERT from nucleoli to nucleoplasm was observed in K562 cells induced by Gleevec.</p> <p>Conclusions</p> <p>Our data reveal that BCR-ABL can regulate TA at multiple levels, including transcription, post-translational level, and proper localization. Thus, suppression of cell growth and induction of apoptosis by Gleevec treatment may be partially due to TA inhibition. Additionally, we have identified STAT5a as critical mediator of the <it>hTERT </it>gene expression in BCR-ABL positive CML cells, suggesting that targeting STAT5a may be a promising therapeutic strategy for BCR-ABL positive CML patients.</p> http://www.biomedcentral.com/1471-2407/11/512
collection DOAJ
language English
format Article
sources DOAJ
author Chai Juin Hsien
Zhang Yong
Tan Wei Han
Chng Wee Joo
Li Baojie
Wang Xueying
spellingShingle Chai Juin Hsien
Zhang Yong
Tan Wei Han
Chng Wee Joo
Li Baojie
Wang Xueying
Regulation of hTERT by BCR-ABL at multiple levels in K562 cells
BMC Cancer
author_facet Chai Juin Hsien
Zhang Yong
Tan Wei Han
Chng Wee Joo
Li Baojie
Wang Xueying
author_sort Chai Juin Hsien
title Regulation of hTERT by BCR-ABL at multiple levels in K562 cells
title_short Regulation of hTERT by BCR-ABL at multiple levels in K562 cells
title_full Regulation of hTERT by BCR-ABL at multiple levels in K562 cells
title_fullStr Regulation of hTERT by BCR-ABL at multiple levels in K562 cells
title_full_unstemmed Regulation of hTERT by BCR-ABL at multiple levels in K562 cells
title_sort regulation of htert by bcr-abl at multiple levels in k562 cells
publisher BMC
series BMC Cancer
issn 1471-2407
publishDate 2011-12-01
description <p>Abstract</p> <p>Background</p> <p>The cytogenetic characteristic of Chronic Myeloid Leukemia (CML) is the formation of the Philadelphia chromosome gene product, BCR-ABL. Given that BCR-ABL is the specific target of Gleevec in CML treatment, we investigated the regulation of the catalytic component of telomerase, hTERT, by BCR-ABL at multiple levels in K562 cells.</p> <p>Methods</p> <p>Molecular techniques such as over expression, knockdown, real-time PCR, immunoprecipitation, western blotting, reporter assay, confocal microscopy, telomerase assays and microarray were used to suggest that hTERT expression and activity is modulated by BCR-ABL at multiple levels.</p> <p>Results</p> <p>Our results suggest that BCR-ABL plays an important role in regulating hTERT in K562 (BCR-ABL positive human leukemia) cells. When Gleevec inhibited the tyrosine kinase activity of BCR-ABL, phosphorylation of hTERT was downregulated, therefore suggesting a positive correlation between BCR-ABL and hTERT. Gleevec treatment inhibited <it>hTERT </it>at mRNA level and significantly reduced telomerase activity (TA) in K562 cells, but not in HL60 or Jurkat cells (BCR-ABL negative cells). We also demonstrated that the transcription factor STAT5a plays a critical role in <it>hTERT </it>gene regulation in K562 cells. Knockdown of STAT5a, but not STAT5b, resulted in a marked downregulation of <it>hTERT </it>mRNA level, TA and hTERT protein level in K562 cells. Furthermore, translocation of hTERT from nucleoli to nucleoplasm was observed in K562 cells induced by Gleevec.</p> <p>Conclusions</p> <p>Our data reveal that BCR-ABL can regulate TA at multiple levels, including transcription, post-translational level, and proper localization. Thus, suppression of cell growth and induction of apoptosis by Gleevec treatment may be partially due to TA inhibition. Additionally, we have identified STAT5a as critical mediator of the <it>hTERT </it>gene expression in BCR-ABL positive CML cells, suggesting that targeting STAT5a may be a promising therapeutic strategy for BCR-ABL positive CML patients.</p>
url http://www.biomedcentral.com/1471-2407/11/512
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