Mosaic RAS/MAPK variants cause sporadic vascular malformations which respond to targeted therapy
Lara Al-Olabi, … , E. Elizabeth Patton, Veronica A. Kinsler
Lara Al-Olabi, … , E. Elizabeth Patton, Veronica A. Kinsler
Published February 20, 2018
Citation Information: J Clin Invest. 2018;128(4):1496-1508. https://doi.org/10.1172/JCI98589.
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Clinical Research and Public Health Vascular biology

Mosaic RAS/MAPK variants cause sporadic vascular malformations which respond to targeted therapy

Abstract

BACKGROUND. Sporadic vascular malformations (VMs) are complex congenital anomalies of blood vessels that lead to stroke, life-threatening bleeds, disfigurement, overgrowth, and/or pain. Therapeutic options are severely limited, and multidisciplinary management remains challenging, particularly for high-flow arteriovenous malformations (AVM). METHODS. To investigate the pathogenesis of sporadic intracranial and extracranial VMs in 160 children in which known genetic causes had been excluded, we sequenced DNA from affected tissue and optimized analysis for detection of low mutant allele frequency. RESULTS. We discovered multiple mosaic-activating variants in 4 genes of the RAS/MAPK pathway, KRAS, NRAS, BRAF, and MAP2K1, a pathway commonly activated in cancer and responsible for the germline RAS-opathies. These variants were more frequent in high-flow than low-flow VMs. In vitro characterization and 2 transgenic zebrafish AVM models that recapitulated the human phenotype validated the pathogenesis of the mutant alleles. Importantly, treatment of AVM-BRAF mutant zebrafish with the BRAF inhibitor vemurafinib restored blood flow in AVM. CONCLUSION. Our findings uncover a major cause of sporadic VMs of different clinical types and thereby offer the potential of personalized medical treatment by repurposing existing licensed cancer therapies. FUNDING. This work was funded or supported by grants from the AVM Butterfly Charity, the Wellcome Trust (UK), the Medical Research Council (UK), the UK National Institute for Health Research, the L’Oreal-Melanoma Research Alliance, the European Research Council, and the National Human Genome Research Institute (US).

Authors

Lara Al-Olabi, Satyamaanasa Polubothu, Katherine Dowsett, Katrina A. Andrews, Paulina Stadnik, Agnel P. Joseph, Rachel Knox, Alan Pittman, Graeme Clark, William Baird, Neil Bulstrode, Mary Glover, Kristiana Gordon, Darren Hargrave, Susan M. Huson, Thomas S. Jacques, Gregory James, Hannah Kondolf, Loshan Kangesu, Kim M. Keppler-Noreuil, Amjad Khan, Marjorie J. Lindhurst, Mark Lipson, Sahar Mansour, Justine O’Hara, Caroline Mahon, Anda Mosica, Celia Moss, Aditi Murthy, Juling Ong, Victoria E. Parker, Jean-Baptiste Rivière, Julie C. Sapp, Neil J. Sebire, Rahul Shah, Branavan Sivakumar, Anna Thomas, Alex Virasami, Regula Waelchli, Zhiqiang Zeng, Leslie G. Biesecker, Alex Barnacle, Maya Topf, Robert K. Semple, E. Elizabeth Patton, Veronica A. Kinsler

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Figure 5

BRAF and MAP2K mutations induce VM phenotypes in zebrafish that respond to targeted therapy.

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BRAF and MAP2K mutations induce VM phenotypes in zebrafish that respond ...
(A) Schematic of zebrafish embryos injected with Tg (fli1a:GFP) at the 1-cell stage generate zebrafish larvae that are mosaic for the transgene integration and expression. (B) Image of mosaic expression of Tg (fli1a:GFP) in a vessel. (C) Images of zebrafish expressing WT or mutant BRAFV600E in a mosaic fashion from a fli1a promoter in endothelial cells. Accumulation of blood is visible at the caudal vein vascular plexus in the BRAFV600E–expressing zebrafish and outlined with a dashed red line. (D) Quantification of VM phenotype in BRAFWT-expressing (n = 511) and BRAFV600E-expressing (n = 779) zebrafish. (E) BRAFWT and BRAFV600E mosaic expression in stable Tg (fli1a:GFP) larvae to visualize all vessels in the zebrafish in the VM lesion. Increased numbers of vascular channels and disorganized architecture of VM lesions are clearly detectable. (F) Schematic of VM treatment protocol and quantification of the percentage of VM BRAFV600E zebrafish with improved blood flow following treatment with vemurafenib. VM BRAFV600E zebrafish were randomized prior to DMSO (n = 31) or vemurafenib (n = 19) treatment and blind scored. (G) Images of zebrafish expressing MAPK2K1Q58del in a mosaic fashion from a fli1a promoter in endothelial cells (n = 5/37). Zebrafish larvae in D were analyzed by an unpaired parametric t test with Welch’s correction and in F by a paired t test comparing matched pairs (before and after treatment). Data are shown as SEM. ***P < 0.001.