Azacytidine Enhances Sensitivity Response to Imatinib in BCR/ABL positive CML Cell Line

Hamid Ali Nagi Al-Jamal, Wan Rohani Wan Taib, Siti Asmaa Mat Jusoh, Aziee Sudin, Muhammad Farid Johan


Azacytidine (5-Aza) is a chemotherapeutic drug that has been known to restore the expression of Tumour suppressor genes by de-methylation and shown clinical efficacy in Myelodysplastic syndrome (MDS) [1-3]. Currently, 5-Aza is being used in UK for the treatment of some adults with MDS, chronic myelocytic leukemia (CML) and acute myelocytic leukemia (AML) [4]. Majority of CML patients treated with imatinib, a BCR/ABL inhibitor would develop resistance under prolonged therapy. Signal transducer and activator of transcription 3 (STAT3) is an oncogenic transcription factor that is constitutively activated in various human cancers including hematological malignancies. Activation of STAT3 represents an important mechanism of imatinib resistant [5]. Methylation of SHP-1 is involved in the constitutive activation of STAT3 [6], and a low level of SHP-1 is not sufficient to inhibit activated STAT3 [7]. Epigenetic silencing of SHP-1 also plays a role in the development of resistance to imatinib in BCR/ABL positive CML cells [8].

Here we evaluated the expression of SHP-1 gene and its methylation status with sensitivity response of resistant CML cell lines to imatinib before and after treatment with 5-Aza. For this purpose, BCR/ABL positive CML cell lines, K562 and K562-R, an imatinib resistant cell lines were treated with 5-Aza. Cytotoxicity of imatinib and apoptosis were determined by MTS and Annexin-V, respectively. Gene expression analysis was detected by real time-PCR, STATs activity using Western blot and methylation status of SHP-1 gene by pyrosequencing analysis. There was a significant hypomethylation of SHP-1 gene in K562-R+5-Aza cells compared to other cells (p=0.003), Table 1.

Gene expression analysis indicates a significant re-expression of SHP-1 gene (p=0.001) after treatment of K562-R cells with 5-Aza (K562-R+5-Aza cells), Fig 1. Interestingly, the re-expression of SHP-1 in K562-R+5-Aza cell lines, was associated with STAT3 inactivation and higher sensitivity to imatinib. In conclusion, 5-Aza could enhance efficacy of imatinib on BCR/ABL CML cells through re-expression of SHP-1 gene and inhibition of STAT3 signaling that could be a new target in cancers treatment.

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Journal of Biomedical and Clinical Sciences (JBCS) publishes original research articles, short review, short communication, case reports, quiz and letter to editor that covering the areas of fundamental aspects of biomedical and clinical sciences, from pre-clinical towards translational research and their applications in medicine, dentistry and healthcare management. JBCS aims to provide a platform for basic science and clinical researchers to communicate and share their research findings to the advancement of technologies in biomedical and clinical sciences by providing maximum access to scholarly communication.

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