Novel Hot Spot Mutations in BCR-ABL1: a Personalised Medicine Approach in Chronic Myeloid Leukaemia

IntroductionAcquisition of mutations in the BCR-ABL1 kinase domain (KD) is frequently associated with tyrosine kinase inhibitor (TKI) failure in chronic myeloid leukemia (CML). Recently, we revealed a novel mutation... [ view full abstract ]

Introduction

Acquisition of mutations in the BCR-ABL1 kinase domain (KD) is frequently associated with tyrosine kinase inhibitor (TKI) failure in chronic myeloid leukemia (CML). Recently, we revealed a novel mutation “hot-spot” in the BCR-ABL1 KD region (residues 295 – 312), associated with high resistance and poor clinical outcomes (Pricl S. et al., Molecular dynamics reveal BCR-ABL1 polymutants as a unique mechanism of resistance to PAN-BCR-ABL1 kinase inhibitor therapy. Proc Natl Acad Sci U S A. 2014 Mar 4;111(9):3550-5).

Here we present an integrated structural, computational, and molecular biology approach to understand the eventual role of the newly reported hot-spot mutations of the BCR-ABL1 KD in TKI resistance observed in CML patients.

Methods

We carried out our investigation using a "two-tier level" investigation: isolated KDs and SH2-linker-SH3-KD (SSKD) BCR-ABL1 constructs. Proteins structure, stability, drug binding and activity were studied by computational/structural (SAXS) biology, isothermal titration calorimetry, surface plasmon resonance, and in vitro kinase assays.

Results

Our findings demonstrate that each single hot-spot mutation exerts different effects on the protein structure, thermodynamic stability, ability to bind specific TKIs (e.g., imatinib, dasatinib, and ponatinib), and kinase activity. Moreover, the study reveals that 1) the use of isolated KD constructs might not be appropriated,  2) the drug residence time plays a major role in the presence of some kinase variants, and 3) the kinase activity of mutant BCR-ABL1 does not always correlate with TKI resistance.

Discussion

Our results show the potential of an inegrated, personalised medicine approach to TKI-resistant CML and provide a strategy that could improve clinical outcomes for CML patients. Characterizing drug resistance that is driven by mechanisms outside of the primary drug target is indeed quite difficult and time-consuming. Yet, the detailed knowledge of the likely escape mechanisms for a given therapy may impact drug selection and the sequencing of active targeted agents. And this, ultimately, will move cancer targeted therapy to the next level, bringing another round of fundamental change to the practice of oncology.