Molecular pharmaceutics

Inhibition of bcr-abl in human leukemic cells with a coiled-coil protein delivered by a leukemia-specific cell-penetrating Peptide.

PMID 25858426


The oncoprotein Bcr-Abl is the cause of chronic myeloid leukemia (CML).1 Current therapies target the tyrosine kinase domain of Bcr-Abl, but resistance to these drugs is common.2 Bcr-Abl homo-oligomerization via its N-terminal coiled-coil (CC) domain is required for tyrosine kinase activity.3 Our previous work has shown that it is possible to inhibit Bcr-Abl activity by targeting the CC domain with a peptidomemetic known as CC(mut3), delivered as a plasmid.4 In this study, CC(mut3) is delivered to cells as a protein by utilizing a leukemia-specific cell-penetrating peptide (CPP).5 Here, recombinant CPP-CC(mut3) was expressed, purified, and tested for its antioncogenic activity. CPP-CC(mut3) was able to enter two leukemic cell lines (K562 and Ba/F3-P210) and inhibit Bcr-Abl activity as shown by induction of necrosis/apoptosis via 7-AAD/Annexin V staining, reduction of oncogenic potential in colony forming assays, reduction of cell proliferation, and inhibition of Bcr-Abl phosphorylation (kinase activity). Further, CPP-CC(mut3) did not enter nonleukemic cell lines (HEK293 and MCF-7). While CPP-CC(mut3) was able to enter the parental, nonleukemic Bcr-Abl(-) Ba/F3 pro-B cell line, it revealed no signs of activity in the assays performed, as expected. These results indicate the feasibility of using CPP-CC(mut3) as a therapeutic against CML.