title: Chronic myeloid leukemia stem cells are not dependent on Bcr-Abl kinase activity for their survival.
abstract: Recent evidence suggests chronic myeloid leukemia (CML) stem cells are insensitive to kinase inhibitors and responsible for minimal residual disease in treated patients. We investigated whether CML stem cells, in a transgenic mouse model of CML-like disease or derived from patients, are dependent on Bcr-Abl. In the transgenic model, after retransplantation, donor-derived CML stem cells in which Bcr-Abl expression had been induced and subsequently shut off were able to persist in vivo and reinitiate leukemia in secondary recipients on Bcr-Abl reexpression. Bcr-Abl knockdown in human CD34(+) CML cells cultured for 12 days in physiologic growth factors achieved partial inhibition of Bcr-Abl and downstream targets p-CrkL and p-STAT5, inhibition of proliferation and colony forming cells, but no reduction of input cells. The addition of dasatinib further inhibited p-CrkL and p-STAT5, yet only reduced input cells by 50%. Complete growth factor withdrawal plus dasatinib further reduced input cells to 10%; however, the surviving fraction was enriched for primitive leukemic cells capable of growth in a long-term culture-initiating cell assay and expansion on removal of dasatinib and addition of growth factors. Together, these data suggest that CML stem cell survival is Bcr-Abl kinase independent and suggest curative approaches in CML must focus on kinase-independent mechanisms of resistance.
authors.affiliation: Paul O'Gorman Leukemia Research Centre, Institute of Cancer Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.
authors.forename: Ashley
authors.initials: A
authors.lastname: Hamilton
authors.forename: G Vignir
authors.initials: GV
authors.lastname: Helgason
authors.forename: Mirle
authors.initials: M
authors.lastname: Schemionek
authors.forename: Bin
authors.initials: B
authors.lastname: Zhang
authors.forename: Svetlana
authors.initials: S
authors.lastname: Myssina
authors.forename: Elaine K
authors.initials: EK
authors.lastname: Allan
authors.forename: Franck E
authors.initials: FE
authors.lastname: Nicolini
authors.forename: Carsten
authors.initials: C
authors.lastname: Müller-Tidow
authors.forename: Ravi
authors.initials: R
authors.lastname: Bhatia
authors.forename: Valerie G
authors.initials: VG
authors.lastname: Brunton
authors.forename: Steffen
authors.initials: S
authors.lastname: Koschmieder
authors.forename: Tessa L
authors.initials: TL
authors.lastname: Holyoake
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D018952:Antigens, CD34 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D000069439:Dasatinib; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D016044:Fusion Proteins, bcr-abl / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015973:Gene Expression Regulation, Leukemic; D055786:Gene Knockout Techniques; D057809:HEK293 Cells; D006801:Humans; D020014:K562 Cells; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008822:Mice, Transgenic; D014411:Neoplastic Stem Cells / Q000378:metabolism* / Q000473:pathology; D009687:Nuclear Proteins / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050799:STAT5 Transcription Factor / Q000378:metabolism; D013844:Thiazoles / Q000494:pharmacology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018952:Antigens, CD34; C082869:CRKL protein; D009687:Nuclear Proteins; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D050799:STAT5 Transcription Factor; D013844:Thiazoles; D016044:Fusion Proteins, bcr-abl; D000069439:Dasatinib