Ponatinib efficiently kills imatinib-resistant chronic eosinophilic leukemia cells harboring gatekeeper mutant T674I FIP1L1-PDGFRα: roles of Mcl-1 and β-catenin.
BACKGROUND
T674I FIP1L1-PDGFRα in a subset of chronic eosinophilic leukemia (CEL) is a gatekeeper mutation that is resistant to many tyrosine kinase inhibitors (TKIs) (e.g., imatinib, nilotinib and dasatinib), similar to T315I Bcr-Abl. Therefore, novel TKIs effective against T674I FIP1L1-PDGFRα are needed. Ponatinib (AP24534) is a novel orally bioavailable TKI against T315I Bcr-Abl, but it is not clear whether ponatinib is effective against T674I FIP1L1-PDGFRα. The purpose of this study was to examine the effect of ponatinib on T674I FIP1L1-PDGFRα.


METHODS
Molecular docking analysis in silico was performed. The effects of ponatinib on PDGFRα signaling pathways, apoptosis and cell cycling were examined in EOL-1, BaF3 cells expressing either wild type (WT) or T674I FIP1L1-PDGFRα. The in vivo antitumor activity of ponatinib was evaluated with xenografted BaF3-T674I FIP1L1-PDGFRα cells in nude mice models.


RESULTS
Molecular docking analysis revealed that ponatinib could bind to the DFG (Asp-Phe-Gly)-out state of T674I PDGFRα. Ponatinib potently inhibited the phosphorylation of WT and T674I FIP1L1-PDGFRα and their downstream signaling molecules (e.g., Stat3, Stat5). Ponatinib strikingly inhibited the growth of both WT and T674I FIP1L1-PDGFRα-carrying CEL cells (IC50: 0.004-2.5 nM). It induced apoptosis in CEL cells with caspase-3-dependent cleavage of Mcl-1, and inhibited tyrosine phosphorylation of β-catenin to decrease its stability and pro-survival functions. In vivo, ponatinib abrogated the growth of xenografted BaF3-T674I FIP1L1-PDGFRα cells in nude mice.


CONCLUSIONS
Ponatinib is a pan-FIP1L1-PDGFRα inhibitor, and clinical trials are warranted to investigate its efficacy in imatinib-resistant CEL.
Yanli
Y
Jin
Ke
K
Ding
Honglin
H
Li
Mengzhu
M
Xue
Xiaoke
X
Shi
Chengyan
C
Wang
Department of Pathophysiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China. panjx2@mail.sysu.edu.cn.
Jingxuan
J
Pan
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D024202:Electrophoretic Mobility Shift Assay; D005455:Fluorescent Antibody Technique; D006801:Humans; D017681:Hypereosinophilic Syndrome / Q000235:genetics / Q000378:metabolism*; D007093:Imidazoles / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D046529:Microscopy, Electron, Transmission; D062105:Molecular Docking Simulation; D064549:Myeloid Cell Leukemia Sequence 1 Protein / Q000378:metabolism; D015514:Oncogene Proteins, Fusion / Q000235:genetics; D011724:Pyridazines / Q000494:pharmacology*; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000235:genetics; D014162:Transfection; D023041:Xenograft Model Antitumor Assays; D051176:beta Catenin / Q000378:metabolism; D039221:mRNA Cleavage and Polyadenylation Factors / Q000235:genetics
D000970:Antineoplastic Agents; C495270:CTNNB1 protein, human; D007093:Imidazoles; C579095:MCL1 protein, human; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D015514:Oncogene Proteins, Fusion; D011724:Pyridazines; D051176:beta Catenin; D039221:mRNA Cleavage and Polyadenylation Factors; C545373:ponatinib; C479819:FIP1L1-PDGFRA fusion protein, human; D020796:Receptor, Platelet-Derived Growth Factor alpha