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Characterization of Imatinib Resistant CML Leukemic Stem/Initiating Cells and Their Sensitivity to CBP/Catenin Antagonists

Author(s):

Yi Zhao, Kaijin Wu, Yongfeng Wu, Elizabeth Melendez, Goar Smbatyan, David Massiello and Michael Kahn*   Pages 1 - 9 ( 9 )

Abstract:


The development of the tyrosine kinase inhibitor Imatinib (IM) represents a milestone breakthrough in CML (Chronic Myeloid Leukemia) treatment. However, it is not curative and patients develop IM resistance. IM resistance has been previously correlated with the emergence of drug-resistant LIC/LSC (Leukemia Initiating Cell/Leukemia Stem Cell) and increased nuclear catenin levels and enhanced Wnt signaling. It has been demonstrated previously that drug resistant CML LIC/LSC can be safely eliminated both in vitro and in vivo via disruption of the CBP/catenin interaction, utilizing the highly biochemically selective small molecule CBP/catenin antagonist ICG-001. Here we utilized an in vitro IM selection of primary CML patients’ samples to identify drug-resistant LIC/LSC populations. In this report we characterized the drug-resistant CML LIC/LSC population using FACS, Smartchip qPCR and colony assays to analyze cell surface markers, transcriptomics and function. As opposed to previous characterization of the CML leukemic stem cell population as being either CD34+CD38- or CD34+CD38+, the in vitro selected Imatinib resistant (IM-R) CML LSC population was consistently CD34-CD38-. In Long-Term Culture Initiating Cell assay (LTC-IC, a surrogate assay for long term repopulating stem cells), our results suggest that the CBP/catenin antagonist ICG-001 sensitizes LIC/LSC to IM treatment by forced differentiative elimination of the CML LIC/LSC population.

Keywords:

CML, Imatinib, CBP, p300, Wnt signaling, leukemia stem cell, ICG-001

Affiliation:

Department of Medicine, Keck School of Medicine of University of Southern California, Los Angeles, California, Department of Biochemistry and Molecular Biology, Norris Comprehensive Cancer Research Center, Keck School of Medicine of University of Southern California, Los Angeles, California, Center for Molecular Pathways and Drug Discovery, Keck School of Medicine, University of Southern California, Los Angeles, CA, Department of Biochemistry and Molecular Biology, Norris Comprehensive Cancer Research Center, Keck School of Medicine of University of Southern California, Los Angeles, California, Department of Biochemistry and Molecular Biology, Norris Comprehensive Cancer Research Center, Keck School of Medicine of University of Southern California, Los Angeles, California, Center for Molecular Pathways and Drug Discovery, Keck School of Medicine, University of Southern California, Los Angeles, CA, Dr. M Kahn, Department of Molecular Medicine, Beckman Research Institute, City of Hope, Duarte, CA 91010-3000



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