Lab related publications

KRAS-driven model of Gorham-Stout disease effectively treated with trametinib

Gorham-Stout disease (GSD) is a sporadically occurring lymphatic disorder. Patients with GSD develop ectopic lymphatics in bone, gradually lose bone, and can have life-threatening complications, such as chylothorax. The etiology of GSD is poorly understood, and current treatments for this disease are inadequate for most patients. To explore the pathogenesis of GSD, we performed targeted high-throughput sequencing with samples from a patient with GSD and identified an activating somatic mutation in KRAS (p.G12V). To characterize the effect of hyperactive KRAS signaling on lymphatic development, we expressed an active form of KRAS (p.G12D) in murine lymphatics (iLECKras mice). We found that iLECKras mice developed lymphatics in bone, which is a hallmark of GSD. We also found that lymphatic valve development and maintenance was altered in iLECKras mice. Because most iLECKras mice developed chylothorax and died before they had significant bone disease, we analyzed the effect of trametinib (an FDA-approved MEK1/2 inhibitor) on lymphatic valve regression in iLECKras mice. Notably, we found that trametinib suppressed this phenotype in iLECKras mice. Together, our results demonstrate that somatic activating mutations in KRAS can be associated with GSD and reveal that hyperactive KRAS signaling stimulates the formation of lymphatics in bone and impairs the development of lymphatic valves. These findings provide insight into the pathogenesis of GSD and suggest that trametinib could be an effective treatment for GSD.

Non‑hotspot PIK3CA mutations are more frequent in CLOVES than in common or combined lymphatic malformations

Pascal Brouillard,Matthieu J. Schlögel, Nassim Homayun Sepehr, Raphaël Helaers, Angela Queisser,Elodie Fastré,Simon Boutry,Sandra Schmitz, Philippe Clapuyt, Frank Hammer, Anne Dompmartin, Annamaria Weitz‑Tuoretmaa, Jussi Laranne,Louise Pasquesoone,Catheline Vilain, Laurence M. Boon and Miikka Vikkula

Most patients with an common or combined lymphatic malformation with or without overgrowth harbour a somatic PIK3CA mutation. However, in about a quarter of patients, no such mutation was detected, suggesting the existence of (an)other cause(s). We detected a hotspot mutation more frequently in common and combined LMs compared to syndromic cases (CLOVES and PROS). Diagnostic genotyping should thus not be limited to PIK3CA hot‑spot mutations.

Universal toxin-based selection for precise genome engineering in human cells

Songyuan Li, Nina Akrap, Silvia Cerboni, Michelle J. Porritt, Sandra Wimberger, Anders Lundin, Carl Möller, Mike Firth, Euan Gordon, Bojana Lazovic, Aleksandra Sieńska, Luna Simona Pane, Matthew A. Coelho, Giovanni Ciotta, Giovanni Pellegrini, Marcella Sini, Xiufeng Xu, Suman Mitra, Mohammad Bohlooly-Y, Benjamin J. M. Taylor, Grzegorz Sienski & Marcello Maresca

It represents a flexible, precise, and efficient selection strategy to engineer cells using CRISPR-Cas and base editing systems. This method enables the rapid generation of a homogenous cell population with bi-allelic integration of a DNA cassette at the selection locus, without clonal isolation. Toxin-based selection works in both cancer-transformed and non-transformed cells, including human induced pluripotent stem cells and human primary T-lymphocytes, as well as it is applicable also in vivo, in mice with humanized liver.

New and Emerging Targeted Therapies for Vascular Malformations

An Van Damme,Emmanuel Seront, Valerie Dekeuleneer, Laurence M. Boon, Miikka Vikkula

Extensive insight into the genetic origin and molecular mechanism of development has been accumulated over the last 20 years. Since the discovery of the first somatic mutations in a vascular anomaly 10 years ago, it is now recognized that they are perhaps all caused by inherited or somatic mutations in genes that hyperactivate two major intracellular signal-ing pathways: the RAS/MAPK/ERK and/or the phosphatidylinositol 3 kinase (PIK3)/protein kinase B/mammalian target of rapamycin (mTOR) pathway. Repurposing of cancer drugs has become a major focus in this rapidly evolving field.

Blockade of VEGF-C signaling inhibits lymphatic malformations driven by oncogenic PIK3CA mutation

Ines Martinez-CorralYan Zhang, Milena PetkovaHenrik OrtsäterSofie SjöbergSandra D. CastilloPascal BrouillardLouis LibbrechtDieter SaurMariona GrauperaKari AlitaloLaurence BoonMiikka Vikkula & Taija Mäkinen

Lymphatic malformations (LMs) are debilitating vascular anomalies presenting with large cysts (macrocystic) or lesions that infiltrate tissues (microcystic). Cellular mechanisms underlying LM pathology are poorly understood. Here we show that the somatic PIK3CAH1047R mutation, resulting in constitutive activation of the p110α PI3K, underlies both macrocystic and microcystic LMs in human.

Blocking Signalopathic Events to Treat Cerebral Cavernous Malformations

SalimAbdelilah-Seyfried, ElisabethTournier-Lasserve, W. BrentDerry

Cerebral cavernous malformations (CCMs) are caused by the clonal loss of any of three CCM genes within endothelial cells of lowly perfused venous capillary vessel beds. In mouse models of CCM, cavernoma growth is spurred when CCM-deficient clones of vessel-resident endothelial progenitor cells recruit wild-type neighboring endothelial cells. Increasing evidence suggests that nongenetic ‘third hits’ cause an activation of quiescent CCM-deficient cells; this may provide novel avenues for drug treatments directed at blocking acute phases of the CCM pathology.

Theranostic Advances in Vascular Malformations

V Dekeuleneer, E Seront, A Van Damme, LM Boon, M Vikkula

Until a few years ago, treatment options of vascular malformations were limited to sclerotherapy and/or surgery. Since, it has been demonstrated that the majority of vascular malformations are caused by inherited or somatic mutations in various genes. These discoveries paved the way for the development and testing of targeted molecular inhibitors as therapies for vascular anomalies via repurposing of anticancer drugs.

A Clinical Feasibility Study to Image Angiogenesis in Patients with Arteriovenous Malformations Using 68Ga-RGD PET/CT

Daphne Lobeek et al.

Arteriovenous malformations (AVMs) have an inherent capacity to form new blood vessels, resulting in excessive lesion growth, and this process is further triggered by the release of angiogenic factors. 68Ga-labeled arginine-glycine-aspartate tripeptide sequence (RGD) PET/CT imaging may provide insight into the angiogenic status and treatment response of AVMs. This clinical feasibility study was performed to demonstrate that 68Ga-RGD PET/CT imaging can be used to quantitatively assess angiogenesis in peripheral AVMs.

RASA1 mosaic mutations in patients with capillary malformation-arteriovenous malformation

N RevencuE Fastre M Ravoet R Helaers P Brouillard A  Bisdorff-Bresson C Chung M Gerard V Dvorakova A Irvine L Boon M Vikkula 

This study shows that RASA1 mosaic mutations can cause capillary malformation-arteriovenous malformation. Thus, highly sensitive sequencing techniques should be considered as diagnostic tools, especially for patients with no family history. Even low-level mosaicism can cause the classical phenotype and increased risk for offspring. In addition, our study further supports the second-hit pathophysiological mechanism to explain the multifocality of vascular lesions in this disorder.