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Differential protein stability and ALK inhibitor sensitivity of EML4-ALK fusion variants
Johannes M Heuckmann1, Hyatt Balke-Want, Florian Malchers
1Department of Translational Genomics, University of Cologne, c/o MPI for Neurological Research, Gleueler Str. 50, 50931 Cologne, Germany.
Purpose:
ALK rearrangement-positive lung cancers can be effectively treated with ALK inhibitors. However, the magnitude and duration of response is heterogeneous. In addition, acquired resistance limits the efficacy of ALK inhibitors, with most upfront resistance mechanisms being unknown.
Experimental Design:
By making use of the Ba/F3 cell line model, we analyzed the cytotoxic efficacy of ALK kinase inhibitors as a function of different EML4-ALK fusion variants v1, v2, v3a, and v3b as well as of three artificially designed EML4-ALK deletion constructs and the ALK fusion genes KIF5b-ALK and NPM1-ALK. In addition, the intracellular localization, the sensitivity to HSP90 inhibition and the protein stability of ALK fusion proteins were studied.
Results:
Different ALK fusion genes and EML4-ALK variants exhibited differential sensitivity to the structurally diverse ALK kinase inhibitors crizotinib and TAE684. In addition, differential sensitivity correlated with differences in protein stability in EML4-ALK-expressing cells. Furthermore, the sensitivity to HSP90 inhibition also varied depending on the ALK fusion partner but differed from ALK inhibitor sensitivity patterns. Finally, combining inhibitors of ALK and HSP90 resulted in synergistic cytotoxicity.
Conclusions:
Our results might explain some of the heterogeneous responses of ALK-positive tumors to ALK kinase inhibition observed in the clinic. Thus, targeted therapy of ALK-positive lung cancer should take into account the precise ALK genotype. Furthermore, combining ALK and HSP90 inhibitors might enhance tumor shrinkage in EML4-ALK-driven tumors.
Insights
Tumor response to ALK inhibitors varies due to different EML4-ALK variants. Combining ALK and HSP90 inhibitors may improve tumor shrinkage in ALK-positive lung cancers.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Anaplastic Lymphoma Kinase (ALK) rearrangement-positive lung cancers show heterogeneous responses to ALK inhibitors.
- Acquired resistance to ALK inhibitors limits treatment efficacy, with unknown upfront resistance mechanisms.
Purpose of the Study:
- To investigate the cytotoxic efficacy of ALK kinase inhibitors against various EML4-ALK variants and other ALK fusion genes.
- To analyze the intracellular localization, HSP90 inhibition sensitivity, and protein stability of ALK fusion proteins.
- To explore potential synergistic effects of combining ALK and HSP90 inhibitors.
Main Methods:
- Utilized the Ba/F3 cell line model to assess inhibitor efficacy against EML4-ALK variants (v1-v3b), deletion constructs, KIF5b-ALK, and NPM1-ALK.
- Studied intracellular localization, HSP90 inhibition sensitivity, and protein stability of ALK fusion proteins.
- Evaluated the cytotoxic effects of combining ALK and HSP90 inhibitors.
Main Results:
- Differential sensitivity of ALK fusion genes and EML4-ALK variants to crizotinib and TAE684 was observed.
- Sensitivity to ALK inhibitors correlated with protein stability, while HSP90 inhibition sensitivity varied with the ALK fusion partner.
- Combined ALK and HSP90 inhibition demonstrated synergistic cytotoxicity.
Conclusions:
- Results may explain heterogeneous clinical responses in ALK-positive tumors.
- Tailoring targeted therapy based on precise ALK genotype is recommended for ALK-positive lung cancer.
- Combination therapy with ALK and HSP90 inhibitors could enhance tumor shrinkage in EML4-ALK-driven tumors.
