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Published on: May 14, 2018
EML4-ALK Variant 3 Promotes Mitotic Errors and Spindle Assembly Checkpoint Deficiency Leading to Increased
Kellie Lucken1, Laura O'Regan1, Jene Choi2
1Department of Molecular and Cell Biology, University of Leicester, Leicester, United Kingdom.
Abstract:
EML4-ALK is an oncogenic fusion protein present in approximately 5% of non-small cell lung cancers (NSCLC). Alternative breakpoints in the gene encoding EML4 result in distinct variants that are linked to markedly different patient outcomes. Patients with EML4-ALK variant 3 (V3) respond poorly to ALK inhibitors and have lower survival rates compared with patients with other common variants, such as V1. Here, we use isogenic Beas-2B bronchial epithelial cell lines expressing EML4-ALK V1 or V3, as well as ALK-positive NSCLC patient cells that express V1 (H3122 cells) or V3 (H2228 cells), to show that EML4-ALK V3 but not V1 leads to hyperstabilized K-fibers in mitosis, as well as errors in chromosome congression and segregation. This is consistent with our observation that EML4-ALK V3 but not V1 localizes to spindle microtubules and that wild-type EML4 is a microtubule stabilizing protein. In addition, cells expressing EML4-ALK V3 exhibit loss of spindle assembly checkpoint control that is at least in part dependent on ALK catalytic activity. Finally, we demonstrate that cells expressing EML4-ALK V3 have increased sensitivity to microtubule poisons that interfere with mitotic spindle assembly, whereas combination treatment with paclitaxel and clinically approved ALK inhibitors leads to a synergistic response in terms of reduced survival of H2228 cells.
Implications:
This study suggests that combining the microtubule poison, paclitaxel, with targeted ALK inhibitors may provide an effective new treatment option for patients with NSCLC with tumors that express the EML4-ALK V3 oncogenic fusion.
Insights
EML4-ALK variant 3 (V3) in non-small cell lung cancer (NSCLC) causes mitotic errors and poor response to ALK inhibitors. Combining paclitaxel with ALK inhibitors shows synergistic effects, offering a potential new NSCLC treatment.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- EML4-ALK fusion proteins drive non-small cell lung cancer (NSCLC) growth.
- Distinct EML4-ALK variants (e.g., V1, V3) correlate with varied patient outcomes and drug responses.
- EML4-ALK variant 3 (V3) is associated with poor response to ALK inhibitors and reduced survival.
Purpose of the Study:
- To investigate the distinct cellular and molecular mechanisms underlying EML4-ALK V1 and V3.
- To determine the impact of EML4-ALK V3 on mitotic processes and spindle assembly checkpoint.
- To evaluate the therapeutic potential of combining microtubule-targeting agents with ALK inhibitors for V3-expressing NSCLC.
Main Methods:
- Utilized isogenic Beas-2B cell lines and NSCLC patient-derived cells expressing EML4-ALK V1 or V3.
- Analyzed mitotic K-fiber stabilization, chromosome congression, and segregation.
- Assessed spindle assembly checkpoint function and sensitivity to microtubule poisons and ALK inhibitors.
Main Results:
- EML4-ALK V3, unlike V1, induces hyperstabilized K-fibers and mitotic errors, including chromosome congression and segregation defects.
- EML4-ALK V3 localizes to spindle microtubules, impacting their stability and function.
- Cells with EML4-ALK V3 show impaired spindle assembly checkpoint control, dependent on ALK activity.
- EML4-ALK V3-expressing cells exhibit enhanced sensitivity to microtubule poisons.
Conclusions:
- EML4-ALK V3 drives mitotic instability through microtubule hyperstabilization and spindle assembly checkpoint dysfunction.
- Combination therapy with paclitaxel and ALK inhibitors demonstrates synergistic efficacy in reducing survival of EML4-ALK V3-positive NSCLC cells.
- This combination strategy represents a promising therapeutic avenue for NSCLC patients with EML4-ALK V3-driven tumors.
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