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Characterization of BCR-ABL deletion mutants from patients with chronic myeloid leukemia
D W Sherbenou1, O Hantschel, L Turaga
1Cell and Developmental Biology, Oregon Health & Science University, Portland, OR, USA.
Abstract:
The BCR-ABL oncogenic tyrosine kinase causes chronic myeloid leukemia and is the target for imatinib therapy. During imatinib treatment, cells are selected in some patients with BCR-ABL kinase domain mutations that render decreased drug sensitivity. In addition, some patients express deletion mutants of BCR-ABL, apparently due to missplicing. Most commonly these deletion mutants lack a significant portion of the kinase domain that includes the P-loop. We describe a screen for such mutations in patients with CML and demonstrate that they are not oncogenic and are catalytically inactive. We hypothesized that coexpressing BCR-ABL deletion mutants has a dominant-negative effect on the native form through heterocomplex formation. However, upon coexpression of native and deletion mutant BCR-ABL in Ba/F3 cells, growth factor independence is maintained and signaling is activated normally. Despite this, these cells have increased imatinib sensitivity compared to cells expressing only native BCR-ABL. Thus, it will be important to investigate the prognostic impact of coexpression of deletion mutants in CML patients during imatinib treatment.
Insights
Deletion mutants of BCR-ABL, found in chronic myeloid leukemia (CML) patients, are inactive but increase imatinib sensitivity when coexpressed with native BCR-ABL. Further study is needed to understand their prognostic impact.
Area of Science:
- Oncology
- Molecular Biology
- Hematology
Background:
- The BCR-ABL tyrosine kinase drives chronic myeloid leukemia (CML).
- Imatinib therapy targets BCR-ABL, but resistance can emerge due to kinase domain mutations or deletion mutants.
- Deletion mutants, often lacking the P-loop, are observed in CML patients undergoing treatment.
Purpose of the Study:
- To screen for BCR-ABL deletion mutants in CML patients.
- To investigate the oncogenic potential and catalytic activity of these deletion mutants.
- To determine the effect of coexpressing BCR-ABL deletion mutants with the native form on imatinib sensitivity.
Main Methods:
- Screening for BCR-ABL deletion mutants in CML patient samples.
- Assessing oncogenic potential and catalytic activity of deletion mutants.
- Coexpression of native and deletion mutant BCR-ABL in Ba/F3 cells to evaluate signaling and drug sensitivity.
Main Results:
- BCR-ABL deletion mutants were identified and confirmed to be non-oncogenic and catalytically inactive.
- Coexpression of native and deletion mutant BCR-ABL in Ba/F3 cells maintained growth factor independence and normal signaling.
- Cells coexpressing both forms exhibited increased sensitivity to imatinib compared to those with only native BCR-ABL.
Conclusions:
- BCR-ABL deletion mutants are inactive but may influence CML treatment outcomes.
- Coexpression of deletion mutants enhances imatinib sensitivity, suggesting a potential therapeutic or prognostic role.
- Further investigation into the prognostic significance of BCR-ABL deletion mutants in CML patients is warranted.
