A xenograft model for venous malformation

Jillian Goines,Xian Li,Adrienne M Hammill,Steven J Fishman,Paula Mobberley-Schuman,Elisa Boscolo,Denise M Adams,Yuqi Cai,Megan Metcalf

doi:10.1007/s10456-018-9624-7

Abstract

Vascular malformations are defects caused by the abnormal growth of the vasculature. Among them, venous malformation (VM) is an anomaly characterized by slow-flow vascular lesions with abnormally shaped veins, typically in sponge-like configuration. VMs can expand over years causing disfigurement, obstruction of vital structures, thrombosis, bleeding, and pain. Treatments have been very limited and primarily based on supportive care, compression garments, sclerotherapy, and/or surgical resection. Sirolimus treatment has recently shown efficacy in some patients with complicated vascular anomalies, including VMs. Activating somatic TIE2 gene mutations have been identified in up to 60% of VMs and PIK3CA mutations have been found in another 25%. Here, we report a xenograft model of VM that reflects the patients’ mutation heterogeneity. First, we established a protocol to isolate and expand in culture endothelial cells (VM–EC) from VM tissue or VM blood of nine patients. In these cells, we identified somatic mutations of TIE2, PIK3CA, or a combination of both. Both TIE2 and PIK3CA mutations induced constitutive AKT activation, while TIE2 mutations also showed high MAPK–ERK signaling. Finally, VM–EC implanted into immune-deficient mice generated lesions with ectatic blood-filled channels with scarce smooth muscle cell coverage, similar to patients’ VM. This VM xenograft model could be instrumental to test the therapeutic efficacy of Sirolimus in the presence of the different TIE2 or PIK3CA mutations or to test for efficacy of additional compounds in targeting the specific mutated protein(s), thus enabling development of personalized treatment options for VM patients.

Highlights

Venous malformation (VM) is a congenital chronic condition that can be severely disfiguring [1, 2]
EC were successfully isolated from 9 VM patients (3 solid tissues and 6 lesion blood samples collected during sclerotherapy procedure) (Table 1)
VM–EC monolayers presented with a homogeneous cobblestone appearance up to passage 7 (Supplemental Fig.S1) and expressed EC-specific markers CD31, vonWillebrand Factor, and vascular endothelial (VE)-Cadherin (Fig. 1a), to normal, control EC (Fig. 1b)

Summary

Introduction

Venous malformation (VM) is a congenital chronic condition that can be severely disfiguring [1, 2]. VMs consist of endothelial-lined dilated slow-flow dysmorphic venous channels, typically in a sponge-like configuration with impaired smooth muscle cell coverage. Treatment with the mTOR inhibitor Sirolimus has shown efficacy in some patients affected by VMs [4, 5]. Activating germline or somatic TEK (TIE2) mutations are associated with VM [6, 7]. TIE2 is an endothelium-specific receptor tyrosine kinase that regulates both maintenance of vascular quiescence and promotion of angiogenesis. Somatic mutations in the catalytic subunit of class I phosphoinositide 3-kinases (PIK3CA), reported in several types of cancer [8], overgrowth syndromes [9–11], and lymphatic malformations [12–14], have been identified in about 20–25% of VM cases [15–17]

Methods

Results

Conclusion