PIK3CA mutations in vascular malformations

Correlation between the miR-618 rs2682818 C>A polymorphism and venous malformation susceptibility

Venous malformations are the most common congenital vascular malformations, and the incidence rate is high. Previous studies have confirmed that a variety of polymorphisms within the miRNA functional region are associated with tumor susceptibility. We examined the correlation between miR-618 rs2682818 C>A and risk of developing venous malformation in a southern Chinese population (1113 patients and 1158 controls). TaqMan genotyping of miR-618 rs2682818 C>A was conducted utilizing real-time fluorescent quantitative PCR. The miR-618 rs2682818 polymorphism was not correlated with susceptibility to venous malformation (CA/AA vs. CC: adjusted odds ratio [AOR] = 1.00, 95% confidence interval [CI] = 0.81-1.25, p = 0.994; AA vs. CC/CA: AOR = 1.10, 95% CI = 0.73-1.65, p = 0.646). Stratified analysis of different subtypes of venous malformation revealed that there was no significant difference in the rs2682818 C>A polymorphism genotypes across these subtypes. Our results indicate that miR-618 rs2682818 C>A polymorphism is not correlated with the susceptibility to venous malformation.

Factors affecting the ability of patients with complex vascular anomalies to navigate the healthcare system

BACKGROUND

Vascular anomalies (VAs) are rare congenital disorders that can cause pain, disfigurement, coagulopathy, asymmetric growth, and disability. Patients with complex VAs experience multiple barriers to accessing expert care. It is imperative to understand which factors support these patients' ability to navigate the healthcare system.

RESULTS

We surveyed adult patients with VAs using previously validated measures, recruiting participants from five patient advocacy groups and multidisciplinary VA clinics. The primary outcome was self-reported ability to access needed medical care, using the "Navigating the Healthcare System" subscale of the Health Literacy Questionnaire. We evaluated factors associated with the ability to navigate the healthcare system using multivariate linear regression (n = 136). We also performed an exploratory model that included the primary care doctor's knowledge of VAs for the subset of participants with a primary care doctor (n = 114). Participants were predominantly women (n = 90, 66%), White and non-Hispanic (n = 109, 73%), and college-educated (n = 101, 73%). Most participants had PIK3CA-Related Overgrowth Spectrum (n = 107, 78%). Most participants reported that navigating the healthcare system was "sometimes" or "usually difficult" (mean score 16.4/30, standard deviation 5.6). In multivariate linear regression, ability to navigate the healthcare system was associated positively with quality of information exchange (β = 0.38, 95% Confidence Interval (CI) 0.22 to 0.55, p <.001) and whether patients had VA specialists (β = 2.31, 95% CI 0.35 to 4.28, p =.021), but not associated with patient self-advocacy, anxiety, education, age, race and ethnicity, gender, or having a primary care doctor. In exploratory analysis of participants with primary care doctors, ability to navigate the healthcare system was positively associated with quality of information exchange (β = 0.27, 95% CI 0.09 to 0.45, p =.004), having a VA specialist (β = 2.31, 95% CI 0.22 to 4.39, p =.031), and primary care doctors' VA knowledge (β = 0.27, 95% CI 0.04 to 0.50, p =.023).

CONCLUSION

Patients with VAs struggle to navigate the healthcare system. High-quality information from clinicians and more knowledgeable primary care doctors might help patients to access needed care. Relying on patient self-advocacy is insufficient. Future efforts should focus on patient-directed and clinician-directed educational interventions. Additionally, future work should assess the structural barriers that impede healthcare access for these patients.

Phosphoinositide 3-kinase as a therapeutic target in angiogenic disease

Phosphoinositide 3-kinases (PI3Ks) generate lipids that control multitudinous intracellular cell signaling events which participate in cell survival and proliferation. In addition, PI3K signaling also contributes to metabolism, immunity, angiogenesis and cardiovascular homeostasis, and many diseases. The diverse actions of PI3K stem from the existence of their various isoforms and a variety of protein effectors. Hence, PI3K isoform-specific inhibitors have already achieved a wonderful effect on treating cancer. Herein, we summarize the molecular mechanism of PI3K inhibitors in preventing the permeability of vessels and neovascularization. Additionally, we briefly illustrate how PI3K signaling modulates blood vessel growth and discuss the different roles that PI3K isoforms play in angiogenesis.

Targeted next-generation sequencing for detection of PIK3CA mutations in archival tissues from patients with Klippel-Trenaunay syndrome in an Asian population : List the full names and institutional addresses for all authors

BACKGROUND

Klippel-Trenaunay syndrome (KTS) is a rare slow-flow combined vascular malformation with limb hypertrophy. KTS is thought to lie on the PIK3CA-related overgrowth spectrum, but reports are limited. PIK3CA encodes p110α, a catalytic subunit of phosphatidylinositol 3-kinase (PI3K) that plays an essential role in the PI3K/AKT/mammalian target of rapamycin (mTOR) signaling pathway. We aimed to demonstrate the clinical utility of targeted next-generation sequencing (NGS) in identifying PIK3CA mosaicism in archival formalin-fixed paraffin-embedded (FFPE) tissues from patients with KTS.

RESULTS

Participants were 9 female and 5 male patients with KTS diagnosed as capillaro-venous malformation (CVM) or capillaro-lymphatico-venous malformation (CLVM). Median age at resection was 14 years (range, 5-57 years). Median archival period before DNA extraction from FFPE tissues was 5.4 years (range, 3-7 years). NGS-based sequencing of PIK3CA achieved an amplicon mean coverage of 119,000x. PIK3CA missense mutations were found in 12 of 14 patients (85.7%; 6/8 CVM and 6/6 CLVM), with 8 patients showing the hotspot variants E542K, E545K, H1047R, and H1047L. The non-hotspot PIK3CA variants C420R, Q546K, and Q546R were identified in 4 patients. Overall, the mean variant allele frequency for identified PIK3CA variants was 6.9% (range, 1.6-17.4%). All patients with geographic capillary malformation, histopathological lymphatic malformation or macrodactyly of the foot had PIK3CA variants. No genotype-phenotype association between hotspot and non-hotspot PIK3CA variants was found. Histologically, the vessels and adipose tissues of the lesions showed phosphorylation of the proteins in the PI3K/AKT/mTOR signaling pathway, including p-AKT, p-mTOR, and p-4EBP1.

CONCLUSIONS

The PI3K/AKT/mTOR pathway in mesenchymal tissues was activated in patients with KTS. Amplicon-based targeted NGS could identify low-level mosaicism from low-input DNA extracted from FFPE tissues, potentially providing a diagnostic option for personalized medicine with inhibitors of the PI3K/AKT/mTOR signaling pathway.

Clinicopathological profile of sclerosing polycystic adenoma/adenosis: A systematic review

In this systematic review, we aimed to evaluate the clinicopathological profile of sclerosing polycystic adenoma (SPA). PubMed, Scopus, EMBASE, Lilacs, Web of Science, and gray literature were searched to access cases of SPA in salivary glands. One hundred and thirty cases of SPA were found across 61 selected articles. SPA affected mainly the parotid gland of adults with a mean age of 44.6 years old, with a slight preference for females. The lesion was usually presented as a painless firm mass with a long period of evolution. Histologically, they are well-delimitated lesions composed of acinar and ductal elements with a variety of cytomorphologic features surrounded by a densely collagenized stroma. PI3K was the most common gene mutation related to SPA. SPA is a benign condition that mainly affects the parotid gland of female patients and it is usually treated by surgical resection with a good prognosis.

Familial CCM Genes Might Not Be Main Drivers for Pathogenesis of Sporadic CCMs-Genetic Similarity between Cancers and Vascular Malformations

Cerebral cavernous malformations (CCMs) are abnormally dilated intracranial capillaries that form cerebrovascular lesions with a high risk of hemorrhagic stroke. Recently, several somatic "activating" gain-of-function (GOF) point mutations in PIK3CA (phosphatidylinositol-4, 5-bisphosphate 3-kinase catalytic subunit p110α) were discovered as a dominant mutation in the lesions of sporadic forms of cerebral cavernous malformation (sCCM), raising the possibility that CCMs, like other types of vascular malformations, fall in the PIK3CA-related overgrowth spectrum (PROS). However, this possibility has been challenged with different interpretations. In this review, we will continue our efforts to expound the phenomenon of the coexistence of gain-of-function (GOF) point mutations in the PIK3CA gene and loss-of-function (LOF) mutations in CCM genes in the CCM lesions of sCCM and try to delineate the relationship between mutagenic events with CCM lesions in a temporospatial manner. Since GOF PIK3CA point mutations have been well studied in reproductive cancers, especially breast cancer as a driver oncogene, we will perform a comparative meta-analysis for GOF PIK3CA point mutations in an attempt to demonstrate the genetic similarities shared by both cancers and vascular anomalies.

Comprehensive targeted next-generation sequencing in patients with slow-flow vascular malformations

Recent studies have shown that the PI3K signaling pathway plays an important role in the pathogenesis of slow-flow vascular malformations (SFVMs). Analysis of genetic mutations has advanced our understanding of the mechanisms involved in SFVM pathogenesis and may identify new therapeutic targets. We screened for somatic variants in a cohort of patients with SFVMs using targeted next-generation sequencing. Targeted next-generation sequencing of 29 candidate genes associated with vascular anomalies or with the PI3K signaling pathway was performed on affected tissues from patients with SFVMs. Fifty-nine patients with SFVMs (venous malformations n  =  21, lymphatic malformations n  =  27, lymphatic venous malformations n  =  1, and Klippel-Trenaunay syndrome n  =  10) were included in the study. TEK and PIK3CA were the most commonly mutated genes in the study. We detected eight TEK pathogenic variants in 10 samples (16.9%) and three PIK3CA pathogenic variants in 28 samples (47.5%). In total, 37 of 59 patients (62.7%) with SFVMs harbored pathogenic variants in these three genes involved in the PI3K signaling pathway. Inhibitors of this pathway may prove useful as molecular targeted therapies for SFVMs.

How we approach hemangiomas in infants

Pediatric oncologists are increasingly involved in the management of benign vascular tumors and their associated life-threatening complications. Hemangiomas are the most common referring diagnosis to multidisciplinary vascular anomalies clinics. However, as contemporary research has revealed, hemangiomas are not a single, easily defined entity but rather a diverse set of related vascular tumors, each having a unique natural history, growth pattern, and response to therapy. This manuscript seeks to illustrate how we evaluate and manage these complex tumors, their complications, and associated syndromes, while remaining ever vigilant for malignant hemangioma mimickers such as soft tissue sarcomas and congenital leukemia.

Cerebral Cavernous Malformation: Immune and Inflammatory Perspectives

Cerebral cavernous malformation (CCM) is a type of vascular anomaly that arises due to the dyshomeostasis of brain capillary networks. In the past two decades, many advances have been made in this research field. Notably, as a more reasonable current view, the CCM lesions should be attributed to the results of a great number of additional events related to the homeostasis disorder of the endothelial cell. Indeed, one of the most fascinating concerns in the research field is the inflammatory perturbation in the immune microenvironment, which would affect the disease progression as well as the patients’ outcomes. In this work, we focused on this topic, and underlined the immune-related factors’ contribution to the CCM pathologic progression.

Lymphangiogenesis requires Ang2/Tie/PI3K signaling for VEGFR3 cell surface expression

Vascular endothelial growth factor C (VEGF-C) induces lymphangiogenesis via VEGF receptor 3 (VEGFR3), which is encoded by the most frequently mutated gene in human primary lymphedema. Angiopoietins (Angs) and their Tie receptors regulate lymphatic vessel development, and mutations of the ANGPT2 gene were recently found in human primary lymphedema. However, the mechanistic basis of Ang2 activity in lymphangiogenesis is not fully understood. Here, we used gene deletion, blocking Abs, transgene induction, and gene transfer to study how Ang2, its Tie2 receptor, and Tie1 regulate lymphatic vessels. We discovered that VEGF-C–induced Ang2 secretion from lymphatic endothelial cells (LECs) was involved in full Akt activation downstream of phosphoinositide 3 kinase (PI3K). Neonatal deletion of genes encoding the Tie receptors or Ang2 in LECs, or administration of an Ang2-blocking Ab decreased VEGFR3 presentation on LECs and inhibited lymphangiogenesis. A similar effect was observed in LECs upon deletion of the PI3K catalytic p110α subunit or with small-molecule inhibition of a constitutively active PI3K located downstream of Ang2. Deletion of Tie receptors or blockade of Ang2 decreased VEGF-C–induced lymphangiogenesis also in adult mice. Our results reveal an important crosstalk between the VEGF-C and Ang signaling pathways and suggest new avenues for therapeutic manipulation of lymphangiogenesis by targeting Ang2/Tie/PI3K signaling.

The onset of PI3K-related vascular malformations occurs during angiogenesis and is prevented by the AKT inhibitor miransertib

Low‐flow vascular malformations are congenital overgrowths composed of abnormal blood vessels potentially causing pain, bleeding and obstruction of different organs. These diseases are caused by oncogenic mutations in the endothelium, which result in overactivation of the PI3K/AKT pathway. Lack of robust in vivo preclinical data has prevented the development and translation into clinical trials of specific molecular therapies for these diseases. Here, we demonstrate that the Pik3ca^H1047R activating mutation in endothelial cells triggers a transcriptome rewiring that leads to enhanced cell proliferation. We describe a new reproducible preclinical in vivo model of PI3K‐driven vascular malformations using the postnatal mouse retina. We show that active angiogenesis is required for the pathogenesis of vascular malformations caused by activating Pik3ca mutations. Using this model, we demonstrate that the AKT inhibitor miransertib both prevents and induces the regression of PI3K‐driven vascular malformations. We confirmed the efficacy of miransertib in isolated human endothelial cells with genotypes spanning most of human low‐flow vascular malformations.

Zebrafish mutants in vegfab can affect endothelial cell proliferation without altering ERK phosphorylation and are phenocopied by loss of PI3K signaling

The formation of appropriately patterned blood vessel networks requires endothelial cell migration and proliferation. Signaling through the Vascular Endothelial Growth Factor A (VEGFA) pathway is instrumental in coordinating these processes. mRNA splicing generates short (diffusible) and long (extracellular matrix bound) Vegfa isoforms. The differences between these isoforms in controlling cellular functions are not understood. In zebrafish, vegfaa generates short and long isoforms, while vegfab only generates long isoforms. We found that mutations in vegfaa had an impact on endothelial cell (EC) migration and proliferation. Surprisingly, mutations in vegfab more strongly affected EC proliferation in distinct blood vessels, such as intersegmental blood vessels in the zebrafish trunk and central arteries in the head. Analysis of downstream signaling pathways revealed no change in MAPK (ERK) activation, while inhibiting PI3 kinase signaling phenocopied vegfab mutant phenotypes in affected blood vessels. Together, these results suggest that extracellular matrix bound Vegfa might act through PI3K signaling to control EC proliferation in a distinct set of blood vessels during angiogenesis.

Interventional Treatment Options in Children with Extracranial Vascular Malformations

Extracranial vascular malformations vary greatly and belong to the complex field of orphan diseases and can involve all segments of the vascular tree: arteries, capillaries, and veins, and similarly the lymphatic system. The classification according to the International Society for the Study of Vascular Anomalies (ISSVA) represents an important guidance for selecting appropriate therapy. Although many of the principles of endovascular treatment, including image-guided sclerotherapy and embolization, are similar in adult and pediatric practice, there are some distinct differences regarding the treatment of vascular malformations of children. Thus, it is crucial to involve longer-term plan about managing these chronic diseases and their impact on a growing child. This review provides a detailed overview over the clinical presentation of venous, lymphatic, and arteriovenous malformations in children and emphasizes the specifics of their interventional treatment options, including distinct pediatric dose limitations and procedure-related side effects.

Clinical Response to PI3K-α Inhibition in a Cohort of Children and Adults With PIK3CA-Related Overgrowth Spectrum Disorders

Objective:

The goal of this report is to describe, through a series of 5 cases, the clinical response and safety of alpelisib (BYL719) use in children and adults with PIK3CA-related overgrowth spectrum (PROS) disorders at our center.

Methods:

We reviewed clinical records of 5 patients from October 2019 through September 2021 followed by the pediatric hematology and multidisciplinary vascular anomalies teams at the Monroe Carell Jr. Children’s Hospital at Vanderbilt (MCJCHV). All patients carried a clinical or genetic diagnosis of PROS and were treated with alpelisib provided by a Novartis managed access program.

Results:

We highlight improvement in reported symptoms, objective overgrowth measurements, and quality of life to varying degrees in all patients. We note dose-dependent hyperglycemia and gastrointestinal side effects in 2 of the 5 patients. No patients experienced any serious side effects.

Conclusion:

This case series reports on the real-world use of PI3K-α inhibition in the management of PROS. Ongoing clinical trials will provide efficacy and safety data as these drugs become more widely used in patients with vascular anomalies and syndromes secondary to somatic PIK3CA mutations.

ISSVA Classification of Vascular Anomalies and Molecular Biology

Vascular anomalies include various diseases, which are classified into two types according to the International Society for the Study of Vascular Anomalies (ISSVA) classification: vascular tumors with proliferative changes of endothelial cells, and vascular malformations primarily consisting of structural vascular abnormalities. The most recent ISSVA classifications, published in 2018, detail the causative genes involved in many lesions. Here, we summarize the latest findings on genetic abnormalities, with the presentation of the molecular pathology of vascular anomalies.

PIK3CA mutation correlates with mTOR pathway expression but not clinical and pathological features in Fibfibroipose vascular anomaly (FAVA)

Background

Fibro-adipose vascular anomaly (FAVA) is a rare and new entity of vascular anomaly. Activating mutations in the phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) gene were identified at a frequency of 62.5% in FAVA cases. The PIK3CA mutations excessively activate mammalian target of rapamycin (mTOR) pathway, which promotes angiogenesis and lymphangiogenesis, implying that PIK3CA mutations may act as drivers of FAVAs. This study investigated the correlations between PIK3CA mutational status, clinicopathological features and immunohistochemical expression of the mTOR pathway in a series of FAVA.

Methods

We retrospectively evaluated the clinical and pathological findings of four FAVA cases. We performed next-generation sequencing (NGS) with a custom panel of genes associated with the mTOR pathway and genes responsible for other vascular anomalies; followed by direct sequencing and immunohistochemical analysis of the mTOR pathway.

Results

Two PIK3CA-mutation cases and two PIK3CA-wild-type (wt) cases exhibited similar typical clinical features of FAVA. Histological analysis revealed venous malformation, lymphatic malformation, nerves containing enlarged abnormal vessels and fibrofatty tissue were observed regardless of PIK3CA mutational status. In contrast to clinical and histological findings, the immunohistochemical expression of activated AKT and mTOR that are upstream of the mTOR pathway was detected in abnormal vessels of PIK3CA-mutation cases but not in those of PIK3CA-wt cases. However, activated eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1) and ribosomal protein S6 kinase 1 (S6K1), both of which are downstream effectors of the mTOR pathway, were expressed in abnormal vessels of both PIK3CA-mutation and PIK3CA-wt cases. Furthermore, targeting NGS did not find any common genetic mutations involved in the mTOR pathway among PIK3CA-wt cases.

Conclusions

There was no significant association between the presence of PIK3CA mutations and the clinicopathological features of FAVA, suggesting that the PIK3CA gene is not necessarily involved in the onset of FAVA. FAVAs lacking PIK3CA mutations may be caused by other gene mutations that activate 4EBP1 and S6K1.

Translational medicine in hereditary hemorrhagic telangiectasia

Scientific community have gained lots of new insights in the genetic and biochemical background of different conditions, rare diseases included, settling the basis for preclinical models that are helping to identify new biomarkers and therapeutic targets. Translational Medicine (TM) is an interdisciplinary area of biomedicine with an essential role in bench-to-bedside transition enhancement, generating a circular flow of knowledge transference between research environment and clinical setting, always centered in patient needs. Here, we present different tools used in TM and an overview of what is being done related to hereditary hemorrhagic telangiectasia (HHT), as a disease's model. This work is focused on how this combination of basic and clinical research impacts in HHT patient's daily clinical management and also looking into the future. Further randomized clinical trials with HHT patients should assess the findings of this bench-to-bedside transition. The benefits of this basic and clinical research combination, may not only be important for HHT patients but for patients with other vascular diseases sharing angiogenic disturbances.

PIK3CA-related overgrowth spectrum (PROS): new insight in known diseases

The overgrowth syndromes related to phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) are grouped under the concept of PROS (PIK3CA-related overgrowth spectrum). It is a heterogeneous group of diseases, considered a rare disease (ORPHA: 530313), which combines the presence of vascular malformations with segmental overgrowth of some parts of the body. All these diseases are caused by mutations in the gene that encodes for the alpha subunit of PI3K. These mutations are somatic and take place during the embryonic stage. Depending on the stage of embryonic development and the affected germ layers, the phenotype will be very different, from syndromes with extensive involvement to isolated forms. Although there are clinical criteria, identification of the mutation by biopsy, although complex, confirms the diagnosis. The objective of the present study is to review the pathophysiological, clinical, diagnostic, and therapeutic aspects of PROS, in order to optimize its identification.

Genetic Basis and Therapies for Vascular Anomalies

Vascular and lymphatic malformations represent a challenge for clinicians. The identification of inherited and somatic mutations in important signaling pathways, including the PI3K (phosphoinositide 3-kinase)/AKT (protein kinase B)/mTOR (mammalian target of rapamycin), RAS (rat sarcoma)/RAF (rapidly accelerated fibrosarcoma)/MEK (mitogen-activated protein kinase kinase)/ERK (extracellular signal-regulated kinases), HGF (hepatocyte growth factor)/c-Met (hepatocyte growth factor receptor), and VEGF (vascular endothelial growth factor) A/VEGFR (vascular endothelial growth factor receptor) 2 cascades has led to the evaluation of tailored strategies with preexisting cancer drugs that interfere with these signaling pathways. The era of theranostics has started for the treatment of vascular anomalies. Registration: URL: https://www.clinicaltrialsregister.eu; Unique identifier: 2015-001703-32.

Cerebral Cavernous Malformation: From Mechanism to Therapy

Cerebral cavernous malformations are acquired vascular anomalies that constitute a common cause of central nervous system hemorrhage and stroke. The past 2 decades have seen a remarkable increase in our understanding of the pathogenesis of this vascular disease. This new knowledge spans genetic causes of sporadic and familial forms of the disease, molecular signaling changes in vascular endothelial cells that underlie the disease, unexpectedly strong environmental effects on disease pathogenesis, and drivers of disease end points such as hemorrhage. These novel insights are the integrated product of human clinical studies, human genetic studies, studies in mouse and zebrafish genetic models, and basic molecular and cellular studies. This review addresses the genetic and molecular underpinnings of cerebral cavernous malformation disease, the mechanisms that lead to lesion hemorrhage, and emerging biomarkers and therapies for clinical treatment of cerebral cavernous malformation disease. It may also serve as an example for how focused basic and clinical investigation and emerging technologies can rapidly unravel a complex disease mechanism.

Lymphovenous shunts: from development to clinical applications

The lymphatic system is a vast network of vessels that functions to return excess fluid from the interstitial space to the blood stream. Lymphovenous shunts are anastomoses, either natural or surgical, that connect the lymphatic and venous systems. Connections between the thoracic duct and venous system or between the right lymphatic duct and venous system are prime examples of anatomic lymphovenous shunts. Lymphovenous shunts are also present peripherally in tissues such as lymph nodes. Furthermore, pathologic lymphovenous shunts are observed in conditions such as lymphedema, malignancy, and lymphovenous malformations. Surgically, lymphovenous shunts may be constructed as an approach to treat lymphedema. Here, we discuss anatomic and surgical lymphovenous shunts in the context of normal development and disease. This perspective is intended to give an understanding of the role of lymphovenous shunts in health and disease and to show how they can be leveraged to treat disease surgically.

Endothelial sprouting, proliferation, or senescence: tipping the balance from physiology to pathology

Therapeutic modulation of vascular cell proliferation and migration is essential for the effective inhibition of angiogenesis in cancer or its induction in cardiovascular disease. The general view is that an increase in vascular growth factor levels or mitogenic stimulation is beneficial for angiogenesis, since it leads to an increase in both endothelial proliferation and sprouting. However, several recent studies showed that an increase in mitogenic stimuli can also lead to the arrest of angiogenesis. This is due to the existence of intrinsic signaling feedback loops and cell cycle checkpoints that work in synchrony to maintain a balance between endothelial proliferation and sprouting. This balance is tightly and effectively regulated during tissue growth and is often deregulated or impaired in disease. Most therapeutic strategies used so far to promote vascular growth simply increase mitogenic stimuli, without taking into account its deleterious effects on this balance and on vascular cells. Here, we review the main findings on the mechanisms controlling physiological vascular sprouting, proliferation, and senescence and how those mechanisms are often deregulated in acquired or congenital cardiovascular disease leading to a diverse range of pathologies. We also discuss alternative approaches to increase the effectiveness of pro-angiogenic therapies in cardiovascular regenerative medicine.

Efficacy and safety of sirolimus in the treatment of vascular malformations: A protocol for systematic review and meta-analysis

BACKGROUND

The pathophysiologic of vascular malformations is still unclear, and the treatment of vascular malformations is a challenge. With improvement in the understanding of pathogenesis of vascular malformations, sirolimus has been a promising and effective treatment. As so far, there is absent convincing evidence to confirm the efficacy of sirolimus for vascular malformations. The purpose of this study was to evaluate the effectiveness and safety of sirolimus in the treatment of vascular malformations.

METHODS

The literatures about the management of vascular malformations with sirolimus would be searched from databases of MEDLINE, EMBASE, PubMed, Web of Science, Clinicaltrials.org., Cochrane Library, China Biology Medicine Database (CBM), Wan Fang Database, China National Knowledge Infrastructure Database (CNKI), and VIP Science Technology Periodical Database. We will search each database from inception or 1995 to August 20, 2020. Two researchers worked independently on literature selection, data extraction and quality assessment. The efficacy and safety of sirolimus in the treatment of vascular malformations were the main outcomes. Adverse events after sirolimus were evaluated as the secondary outcomes. The included studies will be analyzed by Review Manager 5.3. If the results are applicable, meta-analysis would also be performed.

RESULTS

The study will evaluate the efficacy and safety of sirolimus in the treatment of vascular malformations based on current evidence.

CONCLUSION

The conclusion of this study will provide more reliable, evidence-based data for the use of sirolimus in the treatment of vascular malformations.

PROSPERO REGISTRATION NUMBER

CRD42020167881.

Venous malformations

Venous malformations include a spectrum of slow-flow malformations that together are the most common forms of vascular anomalies. Care of these patients requires a multi-disciplinary approach. Goals of care are to ameliorate symptoms and to preserve function. Use of therapeutic compression garments remains the mainstay of therapy. There are new and promising therapies over the last few years that will be invaluable tools for optimal care of this complex patient population. Advances in medical therapy through inhibition of the mTOR/PI3K/AKT pathway with Sirolimus and more proximal targeted drugs along with advances in sclerotherapy techniques are promising for the long-term improvement and amelioration of symptoms in patients with venous malformations.

Frequent activating PIK3CA mutations in sporadic angiolipoma

BACKGROUND

Angiolipoma (AL) is considered as a lipoma variant that is characterized by the combination of mature adipocytes and capillary blood vessels diffusely distributed within the tumor. With the exception of recurrent PRKD2 mutations of uncertain pathogenetic significance, the genetic abnormalities of ALs are unknown, in the absence of any of the specific chromosomal aberrations described in other lipoma variants.

METHODS

Formalin-fixed and paraffin-embedded blocks of 13 conventional ALs and 5 cellular ALs from 17 individuals were retrieved and analyzed for mutations in exons 9 and 20 of PIK3CA by polymerase chain reaction and Sanger sequencing.

RESULTS

Activating PIK3CA mutations were identified in 14 tumors (78%). All PIK3CA-mutated samples carried the same exon 9 mutation, c.1634A>C (p.E545A). No mutation was detected in exon 20 of PIK3CA. No significant difference between PIK3CA-mutated and wild-type samples appeared to exist based on age, gender, and location of the tumor. All 5 cellular ALs carried the p.E545A PIK3CA mutation.

CONCLUSION

The high frequency of the p.E545A PIK3CA mutation in both conventional and cellular ALs suggests that activation of the PI3K/AKT pathway plays a key role in AL pathogenesis and reinforces the concept that cellular AL should be regarded as a variant of AL.

Blockade of VEGF-C signaling inhibits lymphatic malformations driven by oncogenic PIK3CA mutation

Lymphatic malformations (LMs) are debilitating vascular anomalies presenting with large cysts (macrocystic) or lesions that infiltrate tissues (microcystic). Cellular mechanisms underlying LM pathology are poorly understood. Here we show that the somatic PIK3CA^H1047R mutation, resulting in constitutive activation of the p110α PI3K, underlies both macrocystic and microcystic LMs in human. Using a mouse model of PIK3CA^H1047R-driven LM, we demonstrate that both types of malformations arise due to lymphatic endothelial cell (LEC)-autonomous defects, with the developmental timing of p110α activation determining the LM subtype. In the postnatal vasculature, PIK3CA^H1047R promotes LEC migration and lymphatic hypersprouting, leading to microcystic LMs that grow progressively in a vascular endothelial growth factor C (VEGF-C)-dependent manner. Combined inhibition of VEGF-C and the PI3K downstream target mTOR using Rapamycin, but neither treatment alone, promotes regression of lesions. The best therapeutic outcome for LM is thus achieved by co-inhibition of the upstream VEGF-C/VEGFR3 and the downstream PI3K/mTOR pathways.

Lymphatic malformation (LM) is a debilitating often incurable vascular disease. Using a mouse model of LM driven by a disease-causative PIK3CA mutation, the authors show that vascular growth is dependent on the upstream lymphangiogenic VEGF-C signalling, permitting effective therapeutic intervention.

A Primer on a Comprehensive Genetic Approach to Vascular Anomalies

The field of vascular anomalies has grown tremendously in the last few decades with the identification of key molecular pathways and genetic mutations that drive the formation and progression of vascular anomalies. Understanding these pathways is critical for the classification of vascular anomalies, patient care, and development of novel therapeutics. The goal of this review is to provide a basic understanding of the classification of vascular anomalies and knowledge of their underlying molecular pathways. Here we provide an organizational framework for phenotype/genotype correlation and subsequent development of a diagnostic and treatment roadmap. With the increasing importance of genetics in the diagnosis and treatment of vascular anomalies, we highlight the importance of clinical geneticists as part of a comprehensive multidisciplinary vascular anomalies team.

Revisiting PI3-kinase signalling in angiogenesis

PI3Ks belong to a family of lipid kinases that comprises eight isoforms. They phosphorylate the third position of the inositol ring present in phosphatidylinositol lipids and, in turn, activate a broad range of proteins. The PI3K pathway regulates primal cellular responses, including proliferation, migration, metabolism and vesicular traffic. These processes are fundamental for endothelial cell function during sprouting angiogenesis, the most common type of blood vessel formation. Research in animal models has revealed key functions of PI3K family members and downstream effectors in angiogenesis. In addition, perturbations in PI3K signalling have been associated with aberrant vascular growth including tumour angiogenesis and vascular malformations. Together, this highlights that endothelial cells are uniquely sensitive to fluctuations in PI3K signalling. Here, we aim to update the current view on this important signalling cue in physiological and pathological blood vessel growth.

PI3K isoforms in cell signalling and vesicle trafficking

PI3Ks are a family of lipid kinases that phosphorylate intracellular inositol lipids to regulate signalling and intracellular vesicular traffic. Mammals have eight isoforms of PI3K, divided into three classes. The class I PI3Ks generate 3-phosphoinositide lipids, which directly activate signal transduction pathways. In addition to being frequently genetically activated in cancer, similar mutations in class I PI3Ks have now also been found in a human non-malignant overgrowth syndrome and a primary immune disorder that predisposes to lymphoma. The class II and class III PI3Ks are regulators of membrane traffic along the endocytic route, in endosomal recycling and autophagy, with an often indirect effect on cell signalling. Here, we summarize current knowledge of the different PI3K classes and isoforms, focusing on recently uncovered biological functions and the mechanisms by which these kinases are activated. Deeper insight into the PI3K isoforms will undoubtedly continue to contribute to a better understanding of fundamental cell biological processes and, ultimately, of human disease.