Somatic Mutations in the Angiopoietin-Receptor TIE2 Can Cause Both Solitary and Multiple Sporadic Venous Malformations

Germline substitutions in the endothelial cell tyrosine kinase receptor TIE2/TEK cause a rare inherited form of venous anomalies, mucocutaneous venous malformations (VMCM)1-4. We now identified a somatic 2(nd) hit causing loss-of-function of the receptor in a resected VMCM. We assessed for whether such localized, tissue-specific events play a role in the etiology of the far more common sporadic VM. Eight somatic TIE2 mutations were identified in lesions from 28 out of 57 patients (49.1%), not detected in their blood or in control tissues. The somatic mutations included a frequent L914F change, and a series of double-mutations that occurred in cis, all of which show ligand-independent hyperphosphorylation in vitro. When overexpressed in HUVECs, L914F showed abnormal localization and response to ligand, differing from wild-type and the common inherited R849W mutant, suggesting they may have distinct effects. The presence of the same mutations in multifocal VMs in two patients, suggests a common origin for the abnormal endothelial cells in the distant sites. In conclusion, these data illustrate that a sporadic disease may be explained by somatic changes in a gene causing rare, inherited forms, and pinpoint TIE2 pathways as potential therapeutic targets for VM.