NRASQ61R mutation drives elevated angiopoietin-2 expression in human endothelial cells and a genetic mouse model.

BACKGROUND: Angiopoietin-2 (Ang-2) is increased in the blood of patients with kaposiform lymphangiomatosis (KLA) and kaposiform hemangioendothelioma (KHE). While the genetic causes of KHE are not clear, a somatic activating NRASQ61R mutation has been found in the lesions of KLA patients. PROCEDURE: Our study tested the hypothesis that the NRASQ61R mutation drives elevated Ang-2 expression in endothelial cells. Ang-2 was measured in human endothelial progenitor cells (EPC) expressing NRASQ61R and a genetic mouse model with endothelial targeted NRASQ61R. To determine the signaling pathways driving Ang-2, NRASQ61R EPC were treated with signaling pathway inhibitors. RESULTS: Ang-2 levels were increased in EPC expressing NRASQ61R compared to NRASWT by Western blot analysis of cell lysates and ELISA of the cell culture media. Ang-2 levels were elevated in the blood of NRASQ61R mutant mice. NRASQ61R mutant mice also had reduced platelet counts and splenomegaly with hypervascular lesions, like some KLA patients. mTOR inhibitor rapamycin attenuated Ang-2 expression by NRASQ61R EPC. However, MEK1/2 inhibitor trametinib was more effective blocking increases in Ang-2. CONCLUSIONS: Our studies show that the NRASQ61R mutation in endothelial cells induces Ang-2 expression in vitro and in vivo. In cultured human endothelial cells, NRASQ61R drives elevated Ang-2 through MAP kinase and mTOR-dependent signaling pathways.

Complex lymphatic anomalies: Molecular landscape and medical management.

The lymphatic system is one of the most essential and complex systems in the human body. Disorders that affect the development or function of the lymphatic system can lead to multi-system complications and life-long morbidity. The past two decades have seen remarkable progress in our knowledge of the basic biology and function of the lymphatic system, the molecular regulators of lymphatic development, and description of disorders associated with disrupted lymphangiogensis. In this chapter we will touch on the clinical features of complex lymphatic anomalies, new molecular knowledge of the drivers of these disorders, and novel developmental therapeutics for lymphatic disease.

Targeted therapy for capillary-venous malformations.

Sporadic venous malformations are genetic conditions primarily caused by somatic gain-of-function mutation of PIK3CA or TEK, an endothelial transmembrane receptor signaling through PIK3CA. Venous malformations are associated with pain, bleedings, thrombosis, pulmonary embolism, esthetic deformities and, in severe cases, life-threatening situations. No authorized medical treatment exists for patients with venous malformations. Here, we created a genetic mouse model of PIK3CA-related capillary venous malformations that replicates patient phenotypes. We showed that these malformations only partially signal through AKT proteins. We compared the efficacy of different drugs, including rapamycin, a mTORC1 inhibitor, miransertib, an AKT inhibitor and alpelisib, a PI3Kα inhibitor at improving the lesions seen in the mouse model. We demonstrated the effectiveness of alpelisib in preventing vascular malformations' occurrence, improving the already established ones, and prolonging survival. Considering these findings, we were authorized to treat 25 patients with alpelisib, including 7 children displaying PIK3CA (n = 16) or TEK (n = 9)-related capillary venous malformations resistant to usual therapies including sirolimus, debulking surgical procedures or percutaneous sclerotherapies. We assessed the volume of vascular malformations using magnetic resonance imaging (MRI) for each patient. Alpelisib demonstrated improvement in all 25 patients. Vascular malformations previously considered intractable were reduced and clinical symptoms were attenuated. MRI showed a decrease of 33.4% and 27.8% in the median volume of PIK3CA and TEK malformations respectively, over 6 months on alpelisib. In conclusion, this study supports PI3Kα inhibition as a promising therapeutic strategy in patients with PIK3CA or TEK-related capillary venous malformations.