Related Experiment Video
Updated: Jul 17, 2025
Characterize Disease-related Mutants of RAF Family Kinases by Using a Set of Practical and Feasible Methods
Published on: July 17, 2019
BRAFΔβ3-αC in-frame deletion mutants differ in their dimerization propensity, HSP90 dependence, and druggability
Manuel Lauinger1,2, Daniel Christen1,2,3, Rhena F U Klar1,2,3,4,5,6
1Institute of Molecular Medicine, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.
Abstract:
In-frame BRAF exon 12 deletions are increasingly identified in various tumor types. The resultant BRAFΔβ3-αC oncoproteins usually lack five amino acids in the β3-αC helix linker and sometimes contain de novo insertions. The dimerization status of BRAFΔβ3-αC oncoproteins, their precise pathomechanism, and their direct druggability by RAF inhibitors (RAFi) has been under debate. Here, we functionally characterize BRAFΔLNVTAP>F and two novel mutants, BRAFdelinsFS and BRAFΔLNVT>F, and compare them with other BRAFΔβ3-αC oncoproteins. We show that BRAFΔβ3-αC oncoproteins not only form stable homodimers and large multiprotein complexes but also require dimerization. Nevertheless, details matter as aromatic amino acids at the deletion junction of some BRAFΔβ3-αC oncoproteins, e.g., BRAFΔLNVTAP>F, increase their stability and dimerization propensity while conferring resistance to monomer-favoring RAFi such as dabrafenib or HSP 90/CDC37 inhibition. In contrast, dimer-favoring inhibitors such as naporafenib inhibit all BRAFΔβ3-αC mutants in cell lines and patient-derived organoids, suggesting that tumors driven by such oncoproteins are vulnerable to these compounds.
Insights
In-frame BRAF exon 12 deletions create BRAFΔβ3-αC oncoproteins that require dimerization. Dimer-favoring inhibitors effectively target these BRAF mutants, offering a new therapeutic strategy for associated cancers.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Genetics
Background:
- In-frame BRAF exon 12 deletions are emerging in various cancers, producing BRAFΔβ3-αC oncoproteins.
- The exact dimerization, pathomechanism, and druggability of BRAFΔβ3-αC oncoproteins by RAF inhibitors (RAFi) remain debated.
Purpose of the Study:
- To functionally characterize novel BRAFΔβ3-αC mutants (BRAFΔLNVTAP>F, BRAFdelinsFS, BRAFΔLNVT>F).
- To compare these mutants with existing BRAFΔβ3-αC oncoproteins.
- To investigate the role of dimerization in BRAFΔβ3-αC oncoprotein activity and drug sensitivity.
Main Methods:
- Functional characterization of BRAF mutants in cell lines.
- Assessment of protein complex formation and dimerization status.
- Evaluation of sensitivity to RAF inhibitors (RAFi) and HSP 90/CDC37 inhibition.
Main Results:
- BRAFΔβ3-αC oncoproteins form stable homodimers and large complexes, requiring dimerization for activity.
- Aromatic amino acids at the deletion junction enhance stability and dimerization, conferring resistance to monomer-favoring RAFi like dabrafenib.
- Dimer-favoring inhibitors, such as naporafenib, effectively inhibit all tested BRAFΔβ3-αC mutants.
Conclusions:
- BRAFΔβ3-αC oncoproteins are obligate dimers.
- Tumors driven by BRAFΔβ3-αC oncoproteins are sensitive to dimer-favoring RAF inhibitors.
- Targeting BRAF dimerization offers a promising therapeutic avenue for cancers with these mutations.
