Chronic myelogenous leukemia blast cell proliferation is inhibited by peptides that disrupt Grb2-SoS complexes.
Chronic myelogenous leukemia (CML) is commonly characterized by the presence of the p210(Bcr-Abl) oncoprotein. Many downstream effectors of Bcr-Abl have been described, including activation of the Grb2-SoS-Ras-MAP kinase (Erk) pathway. The precise contributions of these signal-transduction proteins in CML blast cells in human patients are not yet well defined. To gain further insight into the importance of Grb2 for CML, peptides that disrupt Grb2-SoS complexes were tested. These high-affinity Grb2-binding peptides (HAGBPs) can autonomously shuttle into cells and function by binding to the N-terminal SH3 domain of Grb2. The HAGBPs were analyzed for their effects on Bcr-Abl-expressing cell lines and freshly isolated CML blast cells from patients. They induced a dramatic decrease in the proliferation of CML cell lines. This was not observed with point-mutated control peptides with abolished Grb2SH3(N) binding. As expected, Grb2-SoS complexes were greatly diminished in the HAGBP-treated cells, and MAP kinase activity was significantly reduced as determined by an activation-specific phospho-MAPK antibody. Furthermore, cell fractions that are enriched for blast cells from CML patients with active disease were also incubated with the Grb2 blocker peptides. The HAGBPs led to a significant proliferation reduction of these cells in the majority of the isolates, but not in all patients' cells. These results show that, in addition to the direct targeting of Bcr-Abl, selective inhibition of Grb2 protein complexes may be a therapeutic option for a significant number of CML patients.
Kardinal
C
C
Laboratory of Molecular Oncology, Institut für Medizinishe Strahleukunde und Zellforschung, Universität Würzburg, Germany.
Konkol
B
B
Lin
H
H
Eulitz
M
M
Schmidt
E K
EK
Estrov
Z
Z
Talpaz
M
M
Arlinghaus
R B
RB
Feller
S M
SM
D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D002454:Cell Differentiation; D002455:Cell Division / Q000187:drug effects; D002463:Cell Membrane Permeability; D004912:Erythrocytes / Q000502:physiology; D051380:GRB2 Adaptor Protein; D006801:Humans; D020014:K562 Cells; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000473:pathology*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D046911:Macromolecular Substances; D051379:Mice; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000494:pharmacology*; D011506:Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry; D020664:Son of Sevenless Proteins / Q000037:antagonists & inhibitors*; D014407:Tumor Cells, Cultured; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; C495949:Grb2 protein, mouse; D046911:Macromolecular Substances; D010455:Peptides; D011506:Proteins; D020664:Son of Sevenless Proteins