Abstract
The gradual emerging of resistance to imatinib urgently calls for the development of new therapy for chronic myeloid leukemia (CML). The fusion protein Bcr-Abl, which promotes the malignant transformation of CML cells, is mainly located in the cytoplasm, while the c-Abl protein which is expressed in the nucleus can induce apoptosis. Based on the hetero-dimerization of FKBP (the 12-kDa FK506- and rapamycin-binding protein) and FRB (the FKBP-rapamycin binding domain of the protein kinase, mTOR) mediated by AP21967, we constructed a nuclear transport system to induce cytoplasmic Bcr-Abl into nuclear. In this study, we reported the construction of the nuclear transport system, and we demonstrated that FN3R (three nuclear localization signals were fused to FRBT2098L with a FLAG tag), HF2S (two FKBP domains were in tandem and fused to the SH2 domain of Grb2 with an HA tag) and Bcr-Abl form a complexus upon AP21967. Bcr-Abl was imported into the nucleus successfully by the nuclear transport system. The nuclear transport system inhibited CML cell proliferation through mitogen-activated protein kinase (MAPK) and signal transducer and activator of transcription 5 (STAT5) pathways mainly by HF2S. It was proven that nuclear located Bcr-Abl induced CML cell (including imatinib-resistant K562G01 cells) apoptosis by activation of p73 and its downstream molecules. In summary, our study provides a new targeted therapy for the CML patients even with Tyrosine Kinase Inhibitor (TKI)-resistance.
Highlights
Chronic myeloid leukemia (CML) is a malignant tumor derived from myeloid stem cells and characterized by the Philadelphia chromosome [1,2]
It has been previously reported that nuclear accumulation of Bcr-Abl with active tyrosine kinase activity triggers apoptosis, which was achieved by treatment with imatinib when nuclear export is blocked by Leptomycin B (LMB) [10,11]
We examined whether the nuclear transport system directs Bcr-Abl into the nucleus and depletes it from the cytoplasm, whether it inhibits growth and promotes apoptosis of CML cells, and the underlying mechanisms
Summary
Chronic myeloid leukemia (CML) is a malignant tumor derived from myeloid stem cells and characterized by the Philadelphia chromosome [1,2]. AP21967 enhanced the suppression of effect on p-STAT5 (Figure 4D) These results confirmed that the HF2S significantly inhibited CML cell proliferation by down-regulation of the kinase activities of MAPK-Akt and STAT5 pathways. Addition of AP21967 synergistically enhanced the apoptotic effect on CML cells: 49.5% in K562 cells, 47.4% in K562G01 cells, and 58.9% in 32D-p210 cells These results suggested that blockade of Y177 by HF2S can induce CML cell apoptosis, while a combination of Y177 blockade and Bcr-Abl nuclear translocation significantly promoted CML cell apoptosis. Most Bcr-Abl resides in the cytoplasm [30,31] and causes the malignant proliferation of CML cells by activating multiple signaling pathways, including JAK/STAT, MAPK/RAS/ERK and PI3K/Akt pathways [32,33]. Since the distinct effects of c-Abl are in different subcellular domains, we constructed a nuclear transport system to
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
