The Bcr-Abl mutations T315I and Y253H do not confer a growth advantage in the absence of imatinib.
Mutations in the Bcr-Abl kinase domain are a frequent cause of imatinib resistance in patients with advanced CML or Ph+ ALL. The impact of these mutations on the overall oncogenic potential of Bcr-Abl and on the clinical course of the disease in the absence of imatinib is presently unclear. In this study, we analyzed the effects of the Bcr-Abl P-loop mutation Y253H and the highly imatinib resistant T315I mutation on kinase activity in vitro and transforming efficiency of Bcr-Abl in vitro and in vivo. Immunoprecipitated Bcr-AblY253H and Bcr-AblT315I proteins displayed similar kinase activities and substrate phosphorylation patterns as Bcr-Abl wildtype. We directly compared the proliferative capacity of mutant to wildtype Bcr-Abl in primary BM cells in vitro and in a murine transplantation model of CML by using a competitive repopulation assay. The results implicate that in the absence of imatinib, there is no growth advantage for cells carrying Bcr-AblT315I or Bcr-AblY253H compared to Bcr-Ablwt, whereas imatinib treatment clearly selects for leukemic cells expressing mutant Bcr-Abl both in vitro and in vivo. Thus, the analysed Bcr-Abl mutants confer imatinib resistance, but do not induce a growth advantage in the absence of imatinib.
Miething
C
C
Department of Internal Medicine III, Klinikum rechts der Isar, Technical University of Munich, Trogerstr, Munich, Germany.
Feihl
S
S
Mugler
C
C
Grundler
R
R
von Bubnoff
N
N
Lordick
F
F
Peschel
C
C
Duyster
J
J
D019943:Amino Acid Substitution; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001549:Benzamides; D001854:Bone Marrow Cells / Q000473:pathology / Q000821:virology; D049109:Cell Proliferation / Q000187:drug effects; D002472:Cell Transformation, Viral; D004195:Disease Models, Animal; D004789:Enzyme Activation / Q000187:drug effects; D016044:Fusion Proteins, bcr-abl / Q000187:drug effects / Q000235:genetics*; D018014:Gene Transfer Techniques; D000068877:Imatinib Mesylate; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009154:Mutation; D041681:NIH 3T3 Cells; D009368:Neoplasm Transplantation; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology*; D012190:Retroviridae / Q000378:metabolism; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D001549:Benzamides; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate; D011505:Protein-Tyrosine Kinases; D016044:Fusion Proteins, bcr-abl