A xenograft model for venous malformation

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.

Treatment of superficial vascular anomalies with topical sirolimus: A multicenter case series

“…This variable response may be explained by physiologic differences in the makeup of venous malformations. Specifically, two distinct somatic mutually exclusive mutations, TIE2 and PIK3CA, have been identified in VMs; however, only PIK3CA is closely associated with the mTOR pathway, and therefore, sirolimus may not be effective if the tumor is resulting from alterations in TIE2 …”

Signaling pathways and inhibitors of cells from patients with kaposiform lymphangiomatosis

“…The presence of common PIK3CA mutations in the KLA cells was assessed by DNA Sanger sequencing as previously described. 13 Briefly, amplified DNA product was generated by PCR using primers for PIK3CA exons 7, 9, and 20 (Integrated DNA Technologies). PCR products were sequenced at the CCHMC DNA Sequencing and Genotyping Core.…”

Cellular and molecular mechanisms of PIK3CA-related vascular anomalies

“…Furthermore, AKT activation is higher in PIK3CA-mutated EC compared to TIE2-mutant EC. Our studies suggest this stronger AKT phosphorylation is linked to increased vessel density in a PIK3CA-mutated patient-derived xenograft model (35,36,37,38). PIK3CA mutation-based models include a patient-derived EC xenograft and murine models with transgenic expression of PIK3CA p.H1047R in the embryonic mesoderm or in VE-Cadherin+ cells (33,34,39).…”

“…PIK3CA mutations are more frequent in intramuscular VM that do not involve the skin (35). TIE2 and PIK3CA mutations are typically mutually exclusive but in few patients both occurred (33,34,35,36). The result of PIK3CA or TIE2 mutation is constitutively active PI3K signaling and downstream AKT activation.…”