title: BCR-ABL1 kinase inhibits uracil DNA glycosylase UNG2 to enhance oxidative DNA damage and stimulate genomic instability.
abstract: Tyrosine kinase inhibitors (TKIs) revolutionized the treatment of chronic myeloid leukemia in chronic phase (CML-CP). Unfortunately, 25% of TKI-naive patients and 50-90% of patients developing TKI-resistance carry CML clones expressing TKI-resistant BCR-ABL1 kinase mutants. We reported that CML-CP leukemia stem and progenitor cell populations accumulate high amounts of reactive oxygen species, which may result in accumulation of uracil derivatives in genomic DNA. Unfaithful and/or inefficient repair of these lesions generates TKI-resistant point mutations in BCR-ABL1 kinase. Using an array of specific substrates and inhibitors/blocking antibodies we found that uracil DNA glycosylase UNG2 were inhibited in BCR-ABL1-transformed cell lines and CD34(+) CML cells. The inhibitory effect was not accompanied by downregulation of nuclear expression and/or chromatin association of UNG2. The effect was BCR-ABL1 kinase-specific because several other fusion tyrosine kinases did not reduce UNG2 activity. Using UNG2-specific inhibitor UGI, we found that reduction of UNG2 activity increased the number of uracil derivatives in genomic DNA detected by modified comet assay and facilitated accumulation of ouabain-resistant point mutations in reporter gene Na(+)/K(+)ATPase. In conclusion, we postulate that BCR-ABL1 kinase-mediated inhibition of UNG2 contributes to accumulation of point mutations responsible for TKI resistance causing the disease relapse, and perhaps also other point mutations facilitating malignant progression of CML.
authors.affiliation: Department of Microbiology and Immunology, Temple University, Philadelphia, PA, USA. aslupian@temple.edu
authors.forename: A
authors.initials: A
authors.lastname: Slupianek
authors.forename: R
authors.initials: R
authors.lastname: Falinski
authors.forename: P
authors.initials: P
authors.lastname: Znojek
authors.forename: T
authors.initials: T
authors.lastname: Stoklosa
authors.forename: S
authors.initials: S
authors.lastname: Flis
authors.forename: V
authors.initials: V
authors.lastname: Doneddu
authors.forename: D
authors.initials: D
authors.lastname: Pytel
authors.forename: E
authors.initials: E
authors.lastname: Synowiec
authors.forename: J
authors.initials: J
authors.lastname: Blasiak
authors.forename: A
authors.initials: A
authors.lastname: Bellacosa
authors.forename: T
authors.initials: T
authors.lastname: Skorski
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002467:Cell Nucleus / Q000235:genetics; D020552:Comet Assay; D004249:DNA Damage / Q000235:genetics*; D004273:DNA, Neoplasm / Q000235:genetics*; D016044:Fusion Proteins, bcr-abl / Q000235:genetics / Q000378:metabolism*; D042822:Genomic Instability; D006801:Humans; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000235:genetics* / Q000473:pathology; D051379:Mice; D016296:Mutagenesis; D014411:Neoplastic Stem Cells / Q000378:metabolism* / Q000473:pathology; D017354:Point Mutation / Q000235:genetics; D016133:Polymerase Chain Reaction; D017382:Reactive Oxygen Species / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics; D014407:Tumor Cells, Cultured; D051981:Uracil-DNA Glycosidase / Q000235:genetics / Q000378:metabolism*
chemical_list: D004273:DNA, Neoplasm; D017382:Reactive Oxygen Species; D016044:Fusion Proteins, bcr-abl; D051981:Uracil-DNA Glycosidase; D000254:Sodium-Potassium-Exchanging ATPase