Somatic activating mutations in Pik3ca cause sporadic venous malformations in mice and humans

The impact of PI3K inhibitors on breast cancer cell and its tumor microenvironment

The phosphoinositide 3-kinase (PI3K) pathway shows frequent aberrant alterations and pathological activation in breast cancer cells. While PI3K inhibitors have not achieved expectant therapeutic efficacy in clinical trials, and several studies provide promising combination strategies to substantially maximize therapeutic outcomes. Besides its direct impact on regulating cancer cells survival, PI3K inhibitors are also demonstrated to have an immunomodulatory impact based on the tumor microenvironment. Inhibition of the leukocyte-enriched PI3K isoforms may break immune tolerance and restore cytotoxic T cell activity by reprogramming the tumor microenvironment. In addition, PI3K inhibitors have pleiotropic effects on tumor angiogenesis and even induce tumor vascular normalization. In this review, we discuss the mechanism of PI3K inhibitor suppression of breast cancer cells and modulation of the tumor microenvironment in order to provide further thoughts for breast cancer treatment.

Targeted therapy in patients with PIK3CA-related overgrowth syndrome

CLOVES syndrome (congenital lipomatous overgrowth, vascular malformations, epidermal naevi, scoliosis/skeletal and spinal syndrome) is a genetic disorder that results from somatic, mosaic gain-of-function mutations of the PIK3CA gene, and belongs to the spectrum of PIK3CA-related overgrowth syndromes (PROS). This rare condition has no specific treatment and a poor survival rate. Here, we describe a postnatal mouse model of PROS/CLOVES that partially recapitulates the human disease, and demonstrate the efficacy of BYL719, an inhibitor of PIK3CA, in preventing and improving organ dysfunction. On the basis of these results, we used BYL719 to treat nineteen patients with PROS. The drug improved the disease symptoms in all patients. Previously intractable vascular tumours became smaller, congestive heart failure was improved, hemihypertrophy was reduced, and scoliosis was attenuated. The treatment was not associated with any substantial side effects. In conclusion, this study provides the first direct evidence supporting PIK3CA inhibition as a promising therapeutic strategy in patients with PROS.

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.

Mosaic RAS/MAPK variants cause sporadic vascular malformations which respond to targeted therapy

BACKGROUND. Sporadic vascular malformations (VMs) are complex congenital anomalies of blood vessels that lead to stroke, life-threatening bleeds, disfigurement, overgrowth, and/or pain. Therapeutic options are severely limited, and multidisciplinary management remains challenging, particularly for high-flow arteriovenous malformations (AVM).

METHODS. To investigate the pathogenesis of sporadic intracranial and extracranial VMs in 160 children in which known genetic causes had been excluded, we sequenced DNA from affected tissue and optimized analysis for detection of low mutant allele frequency.

RESULTS. We discovered multiple mosaic-activating variants in 4 genes of the RAS/MAPK pathway, KRAS, NRAS, BRAF, and MAP2K1, a pathway commonly activated in cancer and responsible for the germline RAS-opathies. These variants were more frequent in high-flow than low-flow VMs. In vitro characterization and 2 transgenic zebrafish AVM models that recapitulated the human phenotype validated the pathogenesis of the mutant alleles. Importantly, treatment of AVM-BRAF mutant zebrafish with the BRAF inhibitor vemurafinib restored blood flow in AVM.

CONCLUSION. Our findings uncover a major cause of sporadic VMs of different clinical types and thereby offer the potential of personalized medical treatment by repurposing existing licensed cancer therapies.

FUNDING. This work was funded or supported by grants from the AVM Butterfly Charity, the Wellcome Trust (UK), the Medical Research Council (UK), the UK National Institute for Health Research, the L’Oreal-Melanoma Research Alliance, the European Research Council, and the National Human Genome Research Institute (US).

ALK1 Loss Results in Vascular Hyperplasia in Mice and Humans Through PI3K Activation

OBJECTIVE

ALK1 (activin-receptor like kinase 1) is an endothelial cell-restricted receptor with high affinity for BMP (bone morphogenetic protein) 9 TGF-β (transforming growth factor-β) family member. Loss-of-function mutations in ALK1 cause a subtype of hereditary hemorrhagic telangiectasia-a rare disease characterized by vasculature malformations. Therapeutic strategies are aimed at reducing potential complications because of vascular malformations, but currently, there is no curative treatment for hereditary hemorrhagic telangiectasia.

APPROACH AND RESULTS

In this work, we report that a reduction in ALK1 gene dosage (heterozygous ALK1^+/- mice) results in enhanced retinal endothelial cell proliferation and vascular hyperplasia at the sprouting front. We found that BMP9/ALK1 represses VEGF (vascular endothelial growth factor)-mediated PI3K (phosphatidylinositol 3-kinase) by promoting the activity of the PTEN (phosphatase and tensin homolog). Consequently, loss of ALK1 function in endothelial cells results in increased activity of the PI3K pathway. These results were confirmed in cutaneous telangiectasia biopsies of patients with hereditary hemorrhagic telangiectasia 2, in which we also detected an increase in endothelial cell proliferation linked to an increase on the PI3K pathway. In mice, genetic and pharmacological inhibition of PI3K is sufficient to abolish the vascular hyperplasia of ALK1^+/- retinas and in turn normalize the vasculature.

CONCLUSIONS

Overall, our results indicate that the BMP9/ALK1 hub critically mediates vascular quiescence by limiting PI3K signaling and suggest that PI3K inhibitors could be used as novel therapeutic agents to treat hereditary hemorrhagic telangiectasia.

PI3K/mTOR inhibition promotes the regression of experimental vascular malformations driven by PIK3CA-activating mutations

Somatic activating mutations within the PIK3CA gene have been recently detected in sporadic lymphatic and venous malformations, and in vascular malformations (VM) associated to overgrowth syndromes, such as CLOVES and Klippel-Trenaunay syndrome. Although VM are often limited to specific tissue areas and can be well treated, in extended or recurrent lesions novel therapeutic approaches are needed. We generated a mouse model of VM by local expression of PIK3CA-activating mutation in endothelial cells. PIK3CA-driven lesions are characterized by large areas of hemorrhage, hyperplastic vessels, infiltrates of inflammatory cells, and elevated endothelial cell density. Such vascular lesions are ameliorated by administration of dual PI3K/mTOR inhibitor, BEZ235, and mTOR inhibitor, Everolimus. Unexpectedly, the expression of PIK3CA-activating mutations in human endothelial cells results in both increased proliferation rates and senescence. Moreover, active forms of PIK3CA strongly promote the angiogenic sprouting. Treatment with PI3K/mTOR inhibitors restores normal endothelial cell proliferation rate and reduces the amount of senescent cells, whereas treatment with Akt inhibitor is less effective. Our findings reveal that PIK3CA mutations have a key role in the pathogenesis of VM and PIK3CA-driven experimental lesions can be effectively treated by PI3K/mTOR inhibitors.

Somatic PIK3CA mutations in seven patients with PIK3CA-related overgrowth spectrum

Somatic mutations in PIK3CA cause many overgrowth syndromes that have been recently coined the "PIK3CA-Related Overgrowth Spectrum." Here, we present seven molecularly confirmed patients with PIK3CA-Related Overgrowth Spectrum, including patients with Congenital Lipomatous Overgrowth, Vascular Malformations, Epidermal Nevi, Scoliosis/Skeletal and Spinal syndrome, Klippel-Trenaunay syndrome, lymphatic malformation and two with atypical phenotypes that cannot be classified into existing disease categories. The literature on PIK3CA-Related Overgrowth Spectrum, suggests that PIK3CA c.1258T>C; p.(Cys420Arg), c.1624G>A; p.(Glu542Lys), c.1633G>A; p.(Glu545Lys), c.3140A>G; p.(His1047Arg), and c.3140A>T; p.(His1047Leu) can be identified in approximately 90% of patients without brain overgrowth. Therefore, droplet digital polymerase chain reaction targeting these mutation hotspots could be used as the first-tier genetic test on patients with PIK3CA-Related Overgrowth Spectrum who do not have signs of overgrowth in their central nervous system. © 2017 Wiley Periodicals, Inc.

Outcomes of Venous Malformation Sclerotherapy: A Review of Study Methodology and Long-Term Results

It is very important that patients seeking sclerotherapy for the treatment of venous malformations are aware of the expected course of the therapy. They should be thoroughly counseled about the complications, the need for multiple sessions of therapy, and also about the expected clinical outcome. The aim of this review is to discuss the long-term outcomes of sclerotherapy for the treatment of venous malformation. Many studies have discussed their individual center's experiences and short-midterm results, but there is a relative paucity of data on long-term outcomes. We have reviewed the literature and also shared our experience of a large cohort of patients ( n  = 116) with a relatively longer follow-up period of more than 1 year. Venous malformations are very complex lesions and their treatment is quite variable depending on its extent and complexity. As a result, outcome studies vary considerably in the choice of sclerosant, study methodology, outcome assessment (clinical vs. imaging), and grading scales. This review also highlights this extreme heterogeneity in the literature of the sclerotherapy outcome and summarizes a few national and international studies for comparison.

Angiopoietin-Tie signalling in the cardiovascular and lymphatic systems

Endothelial cells that form the inner layer of blood and lymphatic vessels are important regulators of vascular functions and centrally involved in the pathogenesis of vascular diseases. In addition to the vascular endothelial growth factor (VEGF) receptor pathway, the angiopoietin (Ang)-Tie system is a second endothelial cell specific ligand-receptor signalling system necessary for embryonic cardiovascular and lymphatic development. The Ang-Tie system also regulates postnatal angiogenesis, vessel remodelling, vascular permeability and inflammation to maintain vascular homoeostasis in adult physiology. This system is implicated in numerous diseases where the vasculature has an important contribution, such as cancer, sepsis, diabetes, atherosclerosis and ocular diseases. Furthermore, mutations in the TIE2 signalling pathway cause defects in vascular morphogenesis, resulting in venous malformations and primary congenital glaucoma. Here, we review recent advances in the understanding of the Ang-Tie signalling system, including cross-talk with the vascular endothelial protein tyrosine phosphatase (VE-PTP) and the integrin cell adhesion receptors, focusing on the Ang-Tie system in vascular development and pathogenesis of vascular diseases.

Fingertip Capillary Malformation and Associated Disorders: Report of 9 Cases

Although capillary malformations (CMs) are not usually serious health problems in themselves, they can occasionally be warning signs for syndromes with more serious or aggressive vascular malformations not readily apparent at birth or on initial examination. We describe a series of 9 patients with a common phenotype: (1) CM on the fingertips; (2) associated combined vascular (lymphatic-venous) malformations on the trunk and/or extremities; and (3) in some cases, partial overgrowth and asymmetry of the extremities. Data were collected retrospectively for patients with CM on the fingertips who were treated at 2 Vascular Anomalies Centers from January 2006 to January 2016. All the patients presented CM and other associated vascular abnormalities from birth. CMs were centripetal in their distribution. The greater the centripetal progression of the CM, the greater the associated vascular malformation observed. Some patients also presented varying degrees of overgrowth and asymmetry. At present, we have not found a patient with CM of the fingertip without associated anomalies. In conclusion, we present a series of patients with a particular morphology of CM located on the fingertips. All cases were associated with lymphatic-venous malformations at other sites. These data lead us to recommend these patients be referred from birth to a multidisciplinary unit of vascular anomalies.

Angiogenesis in metabolic-vascular disease

Angiogenesis, literally formation of new blood vessels, is the main process through which the vascular system expands during embryonic and postnatal development. Endothelial cells, which constitute the inner lining of all blood vessels, are typically in a quiescent state in the healthy adult organism. However, in vascular and metabolic diseases, the endothelium becomes unstable and dysfunctional. The resulting tissue hypoxia may thereby induce pathological angiogenesis, which is a hallmark of disease conditions like cancer or diabetic retinopathy. However, recent evidence suggests that angiogenesis is also a major player in the context of further metabolic diseases, especially in obesity. In particular, deregulated angiogenesis is linked with adipose tissue dysfunction and insulin resistance. On the other hand, signalling pathways, such as the PI3K pathway, may regulate metabolic activities in the endothelium. Endothelial cell metabolism emerges as an important regulator of angiogenesis. This review summarises the role of angiogenesis in metabolic-vascular disease, with specific focus on the role of angiogenesis in obesity-related metabolic dysfunction and on signaling pathways, especially PI3K, linking cell metabolism to endothelial function.

Efficient isolation and culture of endothelial cells from venous malformation using the Rho-associated protein kinase inhibitor Y27632

BACKGROUND

The investigation of primary cells from a pathological lesion can elucidate the pathogenesis of diseases, but, for vascular malformations in humans, such basic research is still stagnant, because the isolation and culture of vascular endothelial cells (ECs) is very difficult. To obtain a sufficient amount of ECs from venous malformation (VM) this study took advantage of a Rho-associated protein kinase inhibitor, Y27632, which had been used for the efficient procurement of primary keratinocytes.

METHODS

ECs were isolated and cultured from VM lesions, combining enzymatic digestion, cell sorting, and Y27632. The proliferative effect of Y27632 on ECs was examined by proliferation assay. The characteristics of the ECs cultured with Y27632 by EC marker expression and tube formation assay were also examined.

RESULTS

Y27632 enhanced the proliferation of ECs and elongated the senescence of the cells. The expression of specific markers of ECs such as von Willebrand factor, endothelin-1, and VE-cadherin, was confirmed in the cells cultured with Y27632. In a tube formation assay, the cells cultured with Y27632 showed higher tube formation ability compared to the cells cultured without Y27632, indicating that Y27632 promoted the angiogenic capability of ECs.

CONCLUSIONS

The protocol using Y27632 offers a new EC culture methodology and provides a new option for the biological investigation of vascular malformations. This new method will contribute to other types of vascular biology research as well.

Vascular heterogeneity and specialization in development and disease

Blood and lymphatic vessels pervade almost all body tissues and have numerous essential roles in physiology and disease. The inner lining of these networks is formed by a single layer of endothelial cells, which is specialized according to the needs of the tissue that it supplies. Whereas the general mechanisms of blood and lymphatic vessel development are being defined with increasing molecular precision, studies of the processes of endothelial specialization remain mostly descriptive. Recent insights from genetic animal models illuminate how endothelial cells interact with each other and with their tissue environment, providing paradigms for vessel type- and organ-specific endothelial differentiation. Delineating these governing principles will be crucial for understanding how tissues develop and maintain, and how their function becomes abnormal in disease.

Endoglin prevents vascular malformation by regulating flow-induced cell migration and specification through VEGFR2 signalling

Loss-of-function (LOF) mutations in the endothelial cell (EC) enriched gene endoglin (ENG) causes the human disease hereditary haemorrhagic telangiectasia-1, characterized by vascular malformations promoted by vascular endothelial growth factor A (VEGFA). How ENG deficiency alters EC behaviour to trigger these anomalies is not understood. Mosaic ENG deletion in the postnatal mouse rendered Eng LOF ECs insensitive to flow-mediated venous to arterial migration. Eng LOF ECs retained within arterioles acquired venous characteristics and secondary ENG-independent proliferation resulting in arterio-venous malformation (AVM). Analysis following simultaneous Eng LOF and overexpression (OE) revealed that ENG OE ECs dominate tip cell positions and home preferentially to arteries. ENG knock-down altered VEGFA-mediated VEGFR2 kinetics and promoted AKT signalling. Blockage of PI3K/AKT partly normalised flow-directed migration of ENG LOF ECs in vitro and reduced the severity of AVM in vivo. This demonstrates the requirement of ENG in flow-mediated migration and modulation of VEGFR2 signalling in vascular patterning.

Therapeutic targeting of the angiopoietin-TIE pathway

The endothelial angiopoietin (ANG)-TIE growth factor receptor pathway regulates vascular permeability and pathological vascular remodelling during inflammation, tumour angiogenesis and metastasis. Drugs that target the ANG-TIE pathway are in clinical development for oncological and ophthalmological applications. The aim is to complement current vascular endothelial growth factor (VEGF)-based anti-angiogenic therapies in cancer, wet age-related macular degeneration and macular oedema. The unique function of the ANG-TIE pathway in vascular stabilization also renders this pathway an attractive target in sepsis, organ transplantation, atherosclerosis and vascular complications of diabetes. This Review covers key aspects of the function of the ANG-TIE pathway in vascular disease and describes the recent development of novel therapeutics that target this pathway.

PI3K Signaling in Tissue Hyper-Proliferation: From Overgrowth Syndromes to Kidney Cysts

The members of the PhosphoInositide-3 Kinase (PI3K) protein family are well-known regulators of proliferative signals. By the generation of lipid second messengers, they mediate the activation of AKT/PKB (AKT) and mammalian Target Of Rapamycin (mTOR) pathways. Although mutations in the PI3K/AKT/mTOR pathway are highly characterized in cancer, recent evidence indicates that alterations in the proliferative signals are major drivers of other diseases such as overgrowth disorders and polycystic kidney disease. In this review, we briefly summarize the role of the PI3K/AKT/mTOR pathway in cell proliferation by comparing the effect of alterations in PI3K enzymes in different tissues. In particular, we discuss the most recent findings on how the same pathway may lead to different biological effects, due to the convergence and cooperation of different signaling cascades.

Mosaic Disorders of the PI3K/PTEN/AKT/TSC/mTORC1 Signaling Pathway

Somatic mutations in genes of the PI3K/PTEN/AKT/TSC/mTORC1 signaling pathway cause segmental overgrowth, hamartomas, and malignant tumors. Mosaicism for activating mutations in AKT1 or PIK3CA cause Proteus syndrome and PIK3CA-Related Overgrowth Spectrum, respectively. Postzygotic mutations in PTEN or TSC1/TSC2 cause mosaic forms of PTEN hamartoma tumor syndrome or tuberous sclerosis complex, respectively. Distinct features observed in these mosaic conditions in part reflect differences in embryological timing or tissue type harboring the mutant cells. Deep sequencing of affected tissue is useful for diagnosis. Drugs targeting mTORC1 or other points along this signaling pathway are in clinical trials to treat these disorders.

Prenatal Detection of PIK3CA-related Overgrowth Spectrum in Cultured Amniocytes Using Long-range PCR and Next-generation Sequencing

Mutations in PIK3CA are associated with overgrowth spectrum disorders including excessive growth in some areas of the body and the central nervous system. Alterations in PIK3CA occur as somatic, postzygotic events and confer a mosaic genotype with variability in phenotypic expression being commonly observed. We describe the second reported prenatal diagnosis of a PIK3CA-related overgrowth spectrum disorder. The prenatal ultrasound features in this case enabled the presumptive, prospective diagnosis to be made which was then confirmed by genetic testing. Subsequent parental testing for mutations in PIK3CA demonstrated normal genotypes. Identification of this mutation prenatally enabled prospective information to be provided to the family and facilitated multidisciplinary perinatal management.

Phosphoinositide 3-kinase: a new kid on the block in vascular anomalies

Vascular anomalies are broadly divided into vascular tumours and malformations. These lesions are composed of abnormal vascular elements of various types, and mainly affect infants, children, and young adults. Vascular anomalies may be painful, may be complicated by bleeding, infection, or organ dysfunction, and can have secondary effects on other tissues. Current treatment strategies include surgical excision, pulsed laser, and sclerotherapy, which are invasive, with risks of recurrence. There are growing pharmacological options for these vascular anomalies, but, to date, no specific targeted therapies have been developed. Phosphoinositide 3-kinases (PI3Ks) constitute a family of lipid kinases that are involved in signal transduction and vesicular traffic, and that modulate important cellular processes such as proliferation, growth, and migration. Recent findings have indicated that the PI3K signalling pathway is important in the pathogenesis of vascular anomalies. This provides an opportunity to use PI3K inhibitors, which are in clinical trials for cancer treatment, for such lesions. Here, we provide an update on the classification of vascular anomalies, with their major features, and discuss the role of the PI3K signalling pathway in the pathogenesis of vascular anomalies, and their clinical implications and therapeutic opportunities. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Targeting PI3K in Cancer: Impact on Tumor Cells, Their Protective Stroma, Angiogenesis, and Immunotherapy

The PI3K pathway is hyperactivated in most cancers, yet the capacity of PI3K inhibitors to induce tumor cell death is limited. The efficacy of PI3K inhibition can also derive from interference with the cancer cells' ability to respond to stromal signals, as illustrated by the approved PI3Kδ inhibitor idelalisib in B-cell malignancies. Inhibition of the leukocyte-enriched PI3Kδ or PI3Kγ may unleash antitumor T-cell responses by inhibiting regulatory T cells and immune-suppressive myeloid cells. Moreover, tumor angiogenesis may be targeted by PI3K inhibitors to enhance cancer therapy. Future work should therefore also explore the effects of PI3K inhibitors on the tumor stroma, in addition to their cancer cell-intrinsic impact.

SIGNIFICANCE

The PI3K pathway extends beyond the direct regulation of cancer cell proliferation and survival. In B-cell malignancies, targeting PI3K purges the tumor cells from their protective microenvironment. Moreover, we propose that PI3K isoform-selective inhibitors may be exploited in the context of cancer immunotherapy and by targeting angiogenesis to improve drug and immune cell delivery. Cancer Discov; 6(10); 1090-105. ©2016 AACR.

CLOVES syndrome: review of a PIK3CA-related overgrowth spectrum (PROS)

Overgrowth syndromes are characterized by global or localized disproportionate growth associated with other anomalies, including vascular malformations and neurological and/or visceral disorders. CLOVES (Congenital Lipomatous asymmetric Overgrowth of the trunk with lymphatic, capillary, venous, and combined-type Vascular malformations, Epidermal naevi, Scoliosis/Skeletal and spinal anomalies) is an overgrowth syndrome caused by mosaic activating mutation in gene PIK3CA, which gives rise to abnormal PI3K-AKT-mTOR pathway activation. These mutations are responsible for the clinical manifestations of the syndrome, which include low- and high-flow vascular malformations, thoracic lipomatous hyperplasia, asymmetric growth, and visceral and neurological disorders. These common anomalies are illustrated with figures from two personal cases. Identification of the clinical and genetic characteristics of CLOVES syndrome is crucial for the differential diagnosis with other overgrowth syndromes, such as Proteus or Klippel-Trenaunay (K-T) syndromes, and for the therapeutic management of the different anomalies. In this context, a new entity comprising different syndromes with phenotypic mutations in PIK3CA has been proposed, designated PIK3CA-related overgrowth spectrum (PROS), with the aim of facilitating clinical management and establishing appropriate genetic study criteria.

Somatic PIK3CA mutations as a driver of sporadic venous malformations

Venous malformations (VM) are vascular malformations characterized by enlarged and distorted blood vessel channels. VM grow over time and cause substantial morbidity because of disfigurement, bleeding, and pain, representing a clinical challenge in the absence of effective treatments (Nguyenet al, 2014; Uebelhoeret al, 2012). Somatic mutations may act as drivers of these lesions, as suggested by the identification of TEK mutations in a proportion of VM (Limayeet al, 2009). We report that activating PIK3CA mutations gives rise to sporadic VM in mice, which closely resemble the histology of the human disease. Furthermore, we identified mutations in PIK3CA and related genes of the PI3K (phosphatidylinositol 3-kinase)/AKT pathway in about 30% of human VM that lack TEK alterations. PIK3CA mutations promote downstream signaling and proliferation in endothelial cells and impair normal vasculogenesis in embryonic development. We successfully treated VM in mouse models using pharmacological inhibitors of PI3Kα administered either systemically or topically. This study elucidates the etiology of a proportion of VM and proposes a therapeutic approach for this disease.