| Description |
Chronic myeloid leukemia (CML) is caused by the constitutive tyrosine kinase activity of the oncoprotein Bcr-Abl. This aberrant kinase activity activates a multitude of oncogenic signaling pathways resulting in myeloid cell proliferation. In the early 2000s, the development of tyrosine kinase inhibitors (TKIs) (such as the breakthrough drug imatinib) greatly improved the prognosis and overall survival of those diagnosed with CML. However, point mutations in the TK domain often limit the clinical effectiveness of TKIs. Second- and third-generation TKIs have been developed to treat those with mutant Bcr-Abl; however, off-target effects and subsequent toxicity of these newer drugs limits their use. The N-terminal coil-coiled (CC) domain of Bcr-Abl allows for homooligomerization, a prerequisite to aberrant TK activity. Previous work in the lab has focused on designing a mutant CC which is capable of binding to the CC in Bcr-Abl, thereby inhibiting oligomerization and subsequent oncogenic signaling. The lead construct, the 72-amina acid CCmut3, was effective against cells harboring both wild-type and clinically-relevant Bcr-Abl mutants when delivered as a gene. As gene therapy is still preclinical, the aim of this work was to create a translatable version of CCmut3. In one study, a leukemia-specific cell-penetrating peptide was added to the N-terminus of the CC, which facilitated protein delivery to leukemic cells and subsequent induction of apoptosis in Bcr-Abl+ cells. Next, peptide stapling was implemented in an attempt to create a proteolytically-resistant version of CCmut3 . Locking the peptide backbone of an ?-helical peptide with an all-hydrocarbon staple can lead to increased helicity, target affinity, serum stability, and half-life. However, stapling of CCmut3 paradoxically led to increased sensitivity to proteolysis, which is explored in Chapter 4. The last chapter in this dissertation focuses on the use of alternative staples and other modifications that could be used to design CC constructs that are resistant to proteolysis. |
