NRASQ61R mutation in human endothelial cells causes vascular malformations.

Somatic mutations in NRAS drive the pathogenesis of melanoma and other cancers but their role in vascular anomalies and specifically human endothelial cells is unclear. The goals of this study were to determine whether the somatic-activating NRASQ61R mutation in human endothelial cells induces abnormal angiogenesis and to develop in vitro and in vivo models to identify disease-causing pathways and test inhibitors. Here, we used mutant NRASQ61R and wild-type NRAS (NRASWT) expressing human endothelial cells in in vitro and in vivo angiogenesis models. These studies demonstrated that expression of NRASQ61R in human endothelial cells caused a shift to an abnormal spindle-shaped morphology, increased proliferation, and migration. NRASQ61R endothelial cells had increased phosphorylation of ERK compared to NRASWT cells indicating hyperactivation of MAPK/ERK pathways. NRASQ61R mutant endothelial cells generated abnormal enlarged vascular channels in a 3D fibrin gel model and in vivo, in xenografts in nude mice. These studies demonstrate that NRASQ61R can drive abnormal angiogenesis in human endothelial cells. Treatment with MAP kinase inhibitor U0126 prevented the change to a spindle-shaped morphology in NRASQ61R endothelial cells, whereas mTOR inhibitor rapamycin did not.

Constitutively active PIK3CA mutations are expressed by lymphatic and vascular endothelial cells in capillary lymphatic venous malformation.

Capillary lymphatic venous malformations (CLVM) are complex vascular anomalies characterized by aberrant and enlarged lymphatic and blood vessels. CLVM appear during fetal development and enlarge after birth, causing life-long complications such as coagulopathy, pulmonary embolism, chronic pain, and disfigurement. Treatment includes surgical debulking, amputation, and recurrent sclerotherapy. Somatic, mosaic mutations in the 110-kD catalytic α-subunit of phosphoinositide-3-kinase (PIK3CA) gene have been previously identified in affected tissues from CLVM patients; however, the cell population harboring the mutation is still unknown. In this study, we hypothesized that endothelial cells (EC) carry the PIK3CA mutations and play a major role in the cellular origin of CLVM. We isolated EC from the lesions of seven patients with CLVM and identified PIK3CA hotspot mutations. The CLVM EC exhibited constitutive phosphorylation of the PI3K effector AKT as well as hyperproliferation and increased resistance to cell death compared to normal EC. Inhibitors of PIK3CA (BYL719) and AKT (ARQ092) attenuated the proliferation of CLVM EC in a dose-dependent manner. A xenograft model of CLVM was developed by injecting patient-derived EC into the flanks of immunocompromised mice. CLVM EC formed lesions with enlarged lymphatic and vascular channels, recapitulating the patient histology. EC subpopulations were further obtained by both immunomagnetic separation into lymphatic EC (LEC) and vascular EC (VEC) and generation of clonal populations. By sequencing these subpopulations, we determined that both LEC and VEC from the same patient express the PIK3CA mutation, exhibit increased AKT activation and can form lymphatic or vascular lesions in mouse.

Ponatinib Combined With Rapamycin Causes Regression of Murine Venous Malformation.

Objective- Venous malformations (VMs) arise from developmental defects of the vasculature and are characterized by massively enlarged and tortuous venous channels. VMs grow commensurately leading to deformity, obstruction of vital structures, bleeding, and pain. Most VMs are associated with the activating mutation L914F in the endothelial cell (EC) tyrosine kinase receptor TIE2. Therapeutic options for VM are limited and ineffective while therapy with the mammalian target of rapamycin inhibitor rapamycin shows moderate efficacy. Here, we investigated novel therapeutic targets promoting VM regression. Approach and Results- We performed an unbiased screen of Food and Drug Administration-approved drugs in human umbilical vein ECs expressing the TIE2-L914F mutation (HUVEC-TIE2-L914F). Three ABL (Abelson) kinase inhibitors prevented cell proliferation of HUVEC-TIE2-L914F. Moreover, c-ABL, common target of these inhibitors, was highly phosphorylated in HUVEC-TIE2-L914F and VM patient-derived ECs with activating TIE2 mutations. Knockdown of c-ABL/ARG in HUVEC-TIE2-L914F reduced cell proliferation and vascularity of murine VM. Combination treatment with the ABL kinase inhibitor ponatinib and rapamycin caused VM regression in a xenograft model based on injection of HUVEC-TIE2-L914F. A reduced dose of this drug combination was effective in this VM murine model with minimal side effects. The drug combination was antiproliferative, enhanced cell apoptosis and vascular channel regression both in vivo and in a 3-dimensional fibrin gel assay. Conclusions- This is the first report of a combination therapy with ponatinib and rapamycin promoting regression of VM. Mechanistically, the drug combination enhanced AKT inhibition compared with single drug treatment and reduced PLCγ (phospholipase C) and ERK (extracellular signal-regulated kinase) activity.

Signaling pathways and inhibitors of cells from patients with kaposiform lymphangiomatosis.

BACKGROUND: Kaposiform lymphangiomatosis (KLA) is a rare lymphatic anomaly with significant morbidity and mortality. KLA is characterized by diffuse multifocal lesions comprised of focal areas of "kaposiform" spindled cells accompanying malformed lymphatic channels. The goal of this study was to identify activated signaling pathways in cells isolated from three KLA patients for the purpose of testing new therapies. PROCEDURE: Cells were obtained from the lungs of one patient isolated at autopsy and the spleen of two patients removed in surgery due to disease complications. A protein kinase array was performed on the KLA cell lysates and normal lymphatic endothelial cells. RESULTS: Higher activation of key signaling pathways in the KLA cells, including PRAS40, AKT1/2/3, and ERK-1/2, was identified by protein kinase array and confirmed by Western blot analysis. This indicated a role for highly activated PI3K-AKT and MAPK-ERK-1/2 signaling pathways in KLA cells. Cell proliferation studies assessed PI3K inhibitors (LY294002; BYL719), AKT inhibitor ARQ092, mTOR inhibitor rapamycin, and MAPK inhibitor U0126. These studies demonstrated that PI3K-AKT-mTOR and MAPK signaling are important mediators of KLA cell proliferation. BYL719 and rapamycin were more effective at inhibiting KLA cell proliferation than U0126. CONCLUSIONS: Our studies using cells from KLA patient lesions demonstrate that these cells are highly proliferative and the PI3K-AKT-mTOR and MAPK pathways are promising therapeutic targets. Development and clinical trials of PI3K, AKT, and MAPK inhibitors for cancer treatment and the data in this study lend support for early clinical trials assessing the efficacy of these inhibitors in KLA patients.

A xenograft model for venous malformation.

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.

Acute consumption of a high-fat diet prior to ischemia-reperfusion results in cardioprotection through NF-κB-dependent regulation of autophagic pathways.

Previous studies have demonstrated improvement of cardiac function occurs with acute consumption of a high-fat diet (HFD) after myocardial infarction (MI). However, no data exist addressing the effects of acute HFD upon the extent of injury after MI. This study investigates the hypothesis that short-term HFD, prior to infarction, protects the heart against ischemia-reperfusion (I/R) injury through NF-κB-dependent regulation of cell death pathways in the heart. Data show that an acute HFD initiates cardioprotection against MI (>50% reduction in infarct size normalized to risk region) after 24 h to 2 wk of HFD, but protection is completely absent after 6 wk of HFD, when mice are reported to develop pathophysiology related to the diet. Furthermore, cardioprotection after 24 h of HFD persists after an additional 24 h of normal chow feeding and was found to be dependent upon NF-κB activation in cardiomyocytes. This study also indicates that short-term HFD activates autophagic processes (beclin-1, LC-3) preischemia, as seen in other protective stimuli. Increases in beclin-1 and LC-3 were found to be NF-κB-dependent, and administration of chloroquine, an inhibitor of autophagy, abrogated cardioprotection. Our results support that acute high-fat feeding mediates cardioprotection against I/R injury associated with a NF-κB-dependent increase in autophagy and reduced apoptosis, as has been found for ischemic preconditioning.

MEK inhibition reduced vascular tumor growth and coagulopathy in a mouse model with hyperactive GNAQ.

Activating non-inherited mutations in the guanine nucleotide-binding protein G(q) subunit alpha (GNAQ) gene family have been identified in childhood vascular tumors. Patients experience extensive disfigurement, chronic pain and severe complications including a potentially lethal coagulopathy termed Kasabach-Merritt phenomenon. Animal models for this class of vascular tumors do not exist. This has severely hindered the discovery of the molecular consequences of GNAQ mutations in the vasculature and, in turn, the preclinical development of effective targeted therapies. Here we report a mouse model expressing hyperactive mutant GNAQ in endothelial cells. Mutant mice develop vascular and coagulopathy phenotypes similar to those seen in patients. Mechanistically, by transcriptomic analysis we demonstrate increased mitogen activated protein kinase signaling in the mutant endothelial cells. Targeting of this pathway with Trametinib suppresses the tumor growth by reducing vascular cell proliferation and permeability. Trametinib also prevents the development of coagulopathy and improves mouse survival.

A Xenograft Model for Venous Malformation.

Xenograft models allow for an in vivo approach to monitor cellular functions within the context of a host microenvironment. Here we describe a protocol to generate a xenograft model of venous malformation (VM) based on the use of human umbilical vein endothelial cells (HUVEC) expressing a constitutive active form of the endothelial tyrosine kinase receptor TEK (TIE2 p.L914F) or patient-derived EC containing TIE2 and/or PIK3CA gene mutations. Hyperactive somatic TIE2 and PIK3CA mutations are a common hallmark of VM in patient lesions. The EC are injected subcutaneously on the back of athymic nude mice to generate ectatic vascular channels and recapitulate histopathological features of VM patient tissue histology. Lesion plugs with TIE2/PIK3CA-mutant EC are visibly vascularized within 7-9 days of subcutaneous injection, making this a great tool to study venous malformation.

A Patient-Derived Xenograft Model for Venous Malformation.

Venous malformation (VM) is a vascular anomaly that arises from impaired development of the venous network resulting in dilated and often dysfunctional veins. The purpose of this article is to carefully describe the establishment of a murine xenograft model that mimics human VM and is able to reflect patient heterogeneity. Hyper-activating non-inherited (somatic) TEK (TIE2) and PIK3CA mutations in endothelial cells (EC) have been identified as the main drivers of pathological vessel enlargement in VM. The following protocol describes the isolation, purification and expansion of patient-derived EC expressing mutant TIE2 and/or PIK3CA. These EC are injected subcutaneously into the back of immunodeficient athymic mice to generate ectatic vascular channels. Lesions generated with TIE2 or PIK3CA-mutant EC are visibly vascularized within 7‒9 days of injection and recapitulate histopathological features of VM patient tissue. This VM xenograft model provides a reliable platform to investigate the cellular and molecular mechanisms driving VM formation and expansion. In addition, this model will be instrumental for translational studies testing the efficacy of novel drug candidates in preventing the abnormal vessel enlargement seen in human VM.

Constitutive Active Mutant TIE2 Induces Enlarged Vascular Lumen Formation with Loss of Apico-basal Polarity and Pericyte Recruitment.

Abnormalities in controlling key aspects of angiogenesis including vascular cell migration, lumen formation and vessel maturation are hallmarks of vascular anomalies including venous malformation (VM). Gain-of-function mutations in the tyrosine kinase receptor TIE2 can cause VM and induce a ligand-independent hyperactivation of TIE2. Despite these important findings, the TIE2-dependent mechanisms triggering enlarged vascular lesions are not well understood. Herein we studied TIE2 p.L914F, the most frequent mutation identified in VM patients. We report that endothelial cells harboring a TIE2-L914F mutation display abnormal cell migration due to a loss of front-rear polarity as demonstrated by a non-polarized Golgi apparatus. Utilizing a three-dimensional fibrin-matrix based model we show that TIE2-L914F mutant cells form enlarged lumens mimicking vascular lesions present in VM patients, independently of exogenous growth factors. Moreover, these abnormal vascular channels demonstrate a dysregulated expression pattern of apico-basal polarity markers Podocalyxin and Collagen IV. Furthermore, in this system we recapitulated another pathological feature of VM, the paucity of pericytes around ectatic veins. The presented data emphasize the value of this in vitro model as a powerful tool for the discovery of cellular and molecular signals contributing to abnormal vascular development and subsequent identification of novel therapeutic approaches.

Antiproliferative Effects of a Triterpene-Enriched Extract from Lingzhi or Reishi Medicinal Mushroom, Ganoderma lucidum (Agaricomycetes), on Human Lung Cancer Cells.

Ganoderma lucidum, a mushroom that has been used to treat disease in East Asia for centuries, has been shown to be effective against many types of tumors, but the exact cellular mechanism of action is unknown. In this study we examined proliferation of a lung cancer cell line after treatment with 12 concentrations of powdered G. lucidum for 24, 48, and 120 hours. Based on half-maximal inhibitory concentrations values, proliferation of the H1793 cell line seemed to be sensitive to the extract in a time- and dose-dependent manner. We used immunoblot analysis to examine the amounts of cell cycle proteins (cyclin D, Cdk4, and Cdc2) and apoptotic proteins (Bcl-xL and Bax) after treatment with a range of G. lucidum concentrations. Changes in amounts of proteins that regulate the cell cycle were consistent with longer G1 and G2 phases. Proapoptotic protein (Bax) levels increased 6.5-fold, with a commensurate increase in the Bax-to-Bcl ratio, especially at 48 and 120 hours. These results suggest that the decrease in cellular proliferation correlated with a change in both cell cycle progression and apoptosis, and that the triterpenoid in G. lucidum is the bioactive component. Further biochemical characterization of this ancient herbal remedy could hold promise for treating lung cancer.