Ponatinib efficiently kills imatinib-resistant chronic eosinophilic leukemia cells harboring gatekeeper mutant T674I FIP1L1-PDGFRα: roles of Mcl-1 and β-catenin
Authors: Jingxuan Pan
Xiaoke Shi
Chengyan Wang
Ke Ding
Mengzhu Xue
Honglin Li
Yanli Jin
Journal: Molecular cancer (2014)
Discipline: MOLECULAR BIOLOGY & GENETICS
Keywords: Chronic eosinophilic leukemia; T674I FIP1L1-PDGFRα; Ponatinib; TKIs; Molecular docking analysis
Affiliations: Department of Pathophysiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China. .

Abstract:  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. 

Retracted: No

PubPeer comments:
 Two Bim bands in Fig. 3E look much more similar than you could expect. Could the authors check please? ![file] , 
 Dear Dr. Platycheirus Stegnus, I am the first author Yanli Jin. Thanks for your kind message. I will carefully check the original data and reply as soon as possible. Thanks. Yanli Jin , 
 Dear Dr. Platycheirus Stegnus, I am the first author Yanli Jin. I carefully checked our original data and admit the error in immunoblot in Figure 3E as you pointed out. The specific immunoblot band for Bim was accidentally duplicated in both BaF3-WT FIP1L1-PDGFRu03b1 and BaF3-T674I FIP1L1-PDGFRu03b1 cells. This error took place during preparation of figures with photoshop microsoftware. The high-resolution scans of the original immunoblots were appended. I deeply apologize for the mistake to readers and appreciate your pointing out. However, I would like to mention that this error does not affect the conclusions of the study. The authors have requested the Journal to give an erratum. Thanks. Yanli Jin Bim original data for BaF3-WT FIP1L1-PDGFRu03b1 and BaF3-T674I FIP1L1-PDGFRu03b1 cells in Figure 3E are shown below. ![file] , 
 Immublots reused in Fig.1 Shown with boxes of the same color ![file] , 
 Dear Dr. Dastarcus Vetustus, I am the first author Yanli Jin. The immunoblot bands against Actin in Figure 1B and 1D were actually from the same set of lysates isolated from the indicated cells treated with different concentrations of Ponatinib. Similarly, the immunoblot bands against Actin in Figure 1C and 1E were from the same set of lysates isolated from the indicated cells treated with Ponatinib for various durations. We did the immunoblotting experiments at the same time, the data were just arranged into different panels while narrating story. Thus, Figure 1B and 1D shared the inner standard. Similarly, Figure 1C and 1E shared the inner standard. We believe that in such an occasion the same actin may give better comparison. The conclusion of the paper was not impacted. Thanks. ,