Kinase domain mutants of Bcr-Abl exhibit altered transformation potency, kinase activity, and substrate utilization, irrespective of sensitivity to imatinib.
Kinase domain (KD) mutations of Bcr-Abl interfering with imatinib binding are the major mechanism of acquired imatinib resistance in patients with Philadelphia chromosome-positive leukemia. Mutations of the ATP binding loop (p-loop) have been associated with a poor prognosis. We compared the transformation potency of five common KD mutants in various biological assays. Relative to unmutated (native) Bcr-Abl, the ATP binding loop mutants Y253F and E255K exhibited increased transformation potency, M351T and H396P were less potent, and the performance of T315I was assay dependent. The transformation potency of Y253F and M351T correlated with intrinsic Bcr-Abl kinase activity, whereas the kinase activity of E255K, H396P, and T315I did not correlate with transforming capabilities, suggesting that additional factors influence transformation potency. Analysis of the phosphotyrosine proteome by mass spectroscopy showed differential phosphorylation among the mutants, a finding consistent with altered substrate specificity and pathway activation. Mutations in the KD of Bcr-Abl influence kinase activity and signaling in a complex fashion, leading to gain- or loss-of-function variants. The drug resistance and transformation potency of mutants may determine the outcome of patients on therapy with Abl kinase inhibitors.
Griswold
Ian J
IJ
Center for Hematologic Malignancies, Oregon Health and Science University, 3181 S.W. Sam Jackson Park Rd., Portland, OR 97239-3098, USA.
MacPartlin
Mary
M
Bumm
Thomas
T
Goss
Valerie L
VL
O'Hare
Thomas
T
Lee
Kimberly A
KA
Corbin
Amie S
AS
Stoffregen
Eric P
EP
Smith
Caitlyn
C
Johnson
Kara
K
Moseson
Erika M
EM
Wood
Lisa J
LJ
Polakiewicz
Roberto D
RD
Druker
Brian J
BJ
Deininger
Michael W
MW
D000595:Amino Acid Sequence; D000818:Animals; D001549:Benzamides; D049109:Cell Proliferation; D002470:Cell Survival; D002471:Cell Transformation, Neoplastic / Q000187:drug effects*; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D004195:Disease Models, Animal; D005260:Female; D016044:Fusion Proteins, bcr-abl / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D000068877:Imatinib Mesylate; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D023461:Myeloid Progenitor Cells / Q000166:cytology; D010770:Phosphotransferases / Q000378:metabolism*; D019000:Phosphotyrosine / Q000378:metabolism; D010879:Piperazines / Q000494:pharmacology*; D017434:Protein Structure, Tertiary; D011743:Pyrimidines / Q000494:pharmacology*; D015398:Signal Transduction; D013379:Substrate Specificity
D001549:Benzamides; D010879:Piperazines; D011743:Pyrimidines; D019000:Phosphotyrosine; D000068877:Imatinib Mesylate; D010770:Phosphotransferases; D016044:Fusion Proteins, bcr-abl