A BCR-ABL mutant lacking direct binding sites for the GRB2, CBL and CRKL adapter proteins fails to induce leukemia in mice.
The BCR-ABL tyrosine kinase is the defining feature of chronic myeloid leukemia (CML) and its kinase activity is required for induction of this disease. Current thinking holds that BCR-ABL forms a multi-protein complex that incorporates several substrates and adaptor proteins and is stabilized by multiple direct and indirect interactions. Signaling output from this highly redundant network leads to cellular transformation. Proteins known to be associated with BCR-ABL in this complex include: GRB2, c-CBL, p62(DOK), and CRKL. These proteins in turn, link BCR-ABL to various signaling pathways indicated in cellular transformation. In this study we show that a triple mutant of BCR-ABL with mutations of the direct binding sites for GRB2, CBL, p62(DOK) and CRKL, is defective for transformation of primary hematopoietic cells in vitro and in a murine CML model, while it retains the capacity to induce IL-3 independence in 32D cells. Compared to BCR-ABL, the triple mutant's ability to activate the MAP kinase and PI3-kinase pathways is severely compromised, while STAT5 phosphorylation is maintained, suggesting that the former are crucial for the transformation of primary cells, but dispensable for transformation of factor dependent cell lines. Our data suggest that inhibition of BCR-ABL-induced leukemia by disrupting protein interactions could be possible, but would require blocking of multiple sites.
Johnson
Kara J
KJ
Division of Hematology and Medical Oncology, Oregon Health & Science University Knight Cancer Institute, Portland, Oregon, United States of America. johnskar@ohsu.edu
Griswold
Ian J
IJ
O'Hare
Thomas
T
Corbin
Amie S
AS
Loriaux
Marc
M
Deininger
Michael W
MW
Druker
Brian J
BJ
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002471:Cell Transformation, Neoplastic; D005260:Female; D016044:Fusion Proteins, bcr-abl / Q000235:genetics*; D051380:GRB2 Adaptor Protein / Q000378:metabolism; D007377:Interleukin-3 / Q000378:metabolism; D007938:Leukemia / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D009374:Neoplasms, Experimental / Q000235:genetics; D009687:Nuclear Proteins / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D050721:Proto-Oncogene Proteins c-cbl / Q000378:metabolism; D050799:STAT5 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction
D048868:Adaptor Proteins, Signal Transducing; C082869:CRKL protein; D051380:GRB2 Adaptor Protein; C495949:Grb2 protein, mouse; D007377:Interleukin-3; D009687:Nuclear Proteins; D050799:STAT5 Transcription Factor; D050721:Proto-Oncogene Proteins c-cbl; D019869:Phosphatidylinositol 3-Kinases; D016044:Fusion Proteins, bcr-abl; C493849:Cbl protein, mouse