Jonathan Constance

Graduate Student
Department of Pharmacology & Toxicology, University of Utah

421 Wakara Way, Rm 306
Salt Lake City
Utah, 84108

ph: 801.581.7120

Research Project

Tyrosine kinase inhibitor (TKI) therapy for Chronic Myelogenous Leukemia (CML) poorly addresses the problems of persistent leukemic stem cells, the fatal blast phase, and TKI resistant CML, all of which have high levels of Bcr-Abl expression in common. The constitutively active tyrosine-kinase fusion protein, Bcr-Abl, is the etiologic agent of CML. The exclusively cytoplasmic Bcr-Abl usurps the role of the tyrosine-kinase Abl and over-stimulates survival, proliferative, and anti-apoptotic signaling; antagonistically, Abl induces apoptosis when moved to the mitochondria. Using endogenous Bcr-Abl as a surrogate to mitochondrial ‘death-directed’ Abl for selectively killing leukemic cells may be an effective strategy for CML. As a proof of concept, preliminary data demonstrate that Bcr-Abl targeted to the mitochondria induce cell death. Statistical fluorescence confocal microscopy showed Bcr-Abl tagged with green fluorescent protein (EGFP) and a mitochondrial translocation signal (MTS) was highly colocalized with the mitochondria of K562 leukemia cells. Additionally, K562 cells transfected with MTS-EGFP-Bcr-Abl had a nearly 5-fold increase in cell death (annexin-V/ 7-AAD) at 24 hours as compared to the TKI imatinib (78±7 vs. 16±11, respectively; P<0.001). By converting Bcr-Abl from an oncogenic factor into an apoptotic agent the three major obstacles of current CML therapy may be overcome.