Ccm3, a gene associated with cerebral cavernous malformations, is required for neuronal migration

Programmed cell death 10 increased blood-brain barrier permeability through HMGB1/TLR4 mediated downregulation of endothelial ZO-1 in glioblastoma

Dysfunction of blood brain barrier (BBB) contributes to the development of peritumoral edema (PTE) and GBM progression. Programmed cell death 10 (PDCD10) exerts various influence on cancers, especially in glioblastoma (GBM). We previously found that PDCD10 expression was positively correlated with PTE extent in GBM. Thus, the present study aims to investigate the emerging role of PDCD10 in regulating BBB permeability in GBM. Here we found that in vitro indirect co-culture of ECs with Pdcd10-overexpressed GL261 cells resulted in a significant increase of FITC-Dextran (MW, 4000) leakage by reducing endothelial zonula occluden-1 (ZO-1) and Claudin-5 expression in ECs respectively. Overexpression of Pdcd10 in GBM cells (GL261) triggered an increase of soluble high mobility group box 1 (HMGB1) release, which in turn activated endothelial toll like receptor 4 (TLR4) and downstream NF-κB, Erk1/2 and Akt signaling in ECs through a paracrine manner. Moreover, Pdcd10-overexpressed GL261 cells facilitated a formation of abnormal vasculature and increased the BBB permeability in vivo. Our present study demonstrates that upregulation of PDCD10 in GBM triggered HMGB1/TLR4 signaling in ECs and significantly decreased endothelial ZO-1 expression, which in turn dominantly increased BBB permeability and contributed to tumor progression in GBM.

The Dual Role of PDCD10 in Cancers: A Promising Therapeutic Target

Programmed cell death 10 (PDCD10) was initially considered as a protein associated with apoptosis. However, recent studies showed that PDCD10 is actually an adaptor protein. By interacting with multiple molecules, PDCD10 participates in various physiological processes, such as cell survival, migration, cell differentiation, vesicle trafficking, cellular senescence, neurovascular development, and gonadogenesis. Moreover, over the past few decades, accumulating evidence has demonstrated that the aberrant expression or mutation of PDCD10 is extremely common in various pathological processes, especially in cancers. The dysfunction of PDCD10 has been strongly implicated in oncogenesis and tumor progression. However, the updated data seem to indicate that PDCD10 has a dual role (either pro- or anti-tumor effects) in various cancer types, depending on cell/tissue specificity with different cellular interactors. In this review, we aimed to summarize the knowledge of the dual role of PDCD10 in cancers with a special focus on its cellular function and potential molecular mechanism. With these efforts, we hoped to provide new insight into the future development and application of PDCD10 as a clinical therapeutic target in cancers.

PDCD10 promotes the aggressive behaviors of pituitary adenomas by up-regulating CXCR2 and activating downstream AKT/ERK signaling

As the second most common primary intracranial neoplasms, about 40% of pituitary adenomas (PAs) exhibit aggressive behaviors and resulting in poor patient prognosis. The molecular mechanisms underlying the aggressive behaviors of PAs are not yet fully understood. Biochemical studies have reported that programmed cell death 10 (PDCD10) is a component of the striatin-interacting phosphatase and kinase (STRIPAK) complex and plays a dual role in cancers in a tissue- or disease-specific manner. In the present study, we report for the first time that the role of PDCD10 in PAs. Cell proliferation, migration and invasion were either enhanced by overexpressing or inhibited by silencing PDCD10 in PA cells. Moreover, PDCD10 significantly promoted epithelial–mesenchymal transition (EMT) of pituitary adenoma cells. Mechanistically, we showed that the expression of CXCR2, together with phosphorylation levels of AKT and ERK1/2 were regulated by PDCD10. Activation of CXCR2 inversed inactivation of AKT/ERK signal pathways and the tumor-suppressive effects induced by PDCD10 silencing. Finally, the pro-oncogenic effect of PDCD10 was confirmed by in vivo tumor grafting. Taken together, we demonstrate for the first time that PDCD10 can induce aggressive behaviors of PAs by promoting cellular proliferation, migration, invasion and EMT through CXCR2-AKT/ERK signaling axis.

The multifaceted PDCD10/CCM3 gene

The programmed cell death 10 (PDCD10) gene was originally identified as an apoptosis-related gene, although it is now usually known as CCM3, as the third causative gene of cerebral cavernous malformation (CCM). CCM is a neurovascular disease that is characterized by vascular malformations and is associated with headaches, seizures, focal neurological deficits, and cerebral hemorrhage. The PDCD10/CCM3 protein has multiple subcellular localizations and interacts with several multi-protein complexes and signaling pathways. Thus PDCD10/CCM3 governs many cellular functions, which include cell-to-cell junctions and cytoskeleton organization, cell proliferation and apoptosis, and exocytosis and angiogenesis. Given its central role in the maintenance of homeostasis of the cell, dysregulation of PDCD10/CCM3 can result in a wide range of altered cell functions. This can lead to severe diseases, including CCM, cognitive disability, and several types of cancers. Here, we review the multifaceted roles of PDCD10/CCM3 in physiology and pathology, with a focus on its functions beyond CCM.

Pdcd10-Stk24/25 complex controls kidney water reabsorption by regulating Aqp2 membrane targeting

PDCD10, also known as CCM3, is a gene found to be associated with the human disease cerebral cavernous malformations (CCMs). PDCD10 forms a complex with GCKIII kinases including STK24, STK25, and MST4. Studies in C. elegans and Drosophila have shown a pivotal role of the PDCD10-GCKIII complex in maintaining epithelial integrity. Here, we found that mice deficient of Pdcd10 or Stk24/25 in the kidney tubules developed polyuria and displayed increased water consumption. Although the expression levels of aquaporin genes were not decreased, the levels of total and phosphorylated aquaporin 2 (Aqp2) protein in the apical membrane of tubular epithelial cells were decreased in Pdcd10- and Stk24/25-deficient mice. This loss of Aqp2 was associated with increased expression and membrane targeting of Ezrin and phosphorylated Ezrin, Radixin, Moesin (p-ERM) proteins and impaired intracellular vesicle trafficking. Treatment with Erlotinib, a tyrosine kinase inhibitor promoting exocytosis and inhibiting endocytosis, normalized the expression level and membrane abundance of Aqp2 protein, and partially rescued the water reabsorption defect observed in the Pdcd10-deficient mice. Our current study identified the PDCD10-STK-ERM signaling pathway as a potentially novel pathway required for water balance control by regulating vesicle trafficking and protein abundance of AQP2 in the kidneys.

Programmed Cell Death 10 Mediated CXCL2-CXCR2 Signaling in Regulating Tumor-Associated Microglia/Macrophages Recruitment in Glioblastoma

Background

Programmed cell death 10 (PDCD10) plays a crucial role in regulating tumor phenotyping, especially in glioblastoma (GBM). Glioma-associated microglia/macrophages (GAMs) in tumor pathological microenvironment contribute to GBM progression. We previously found that the infiltration of GAMs was associated with PDCD10 expression in GBM patients. The present study aims to further explore the regulation of PDCD10 on GAMs in GBM.

Methods

Overexpression of PDCD10 in human- and murine-GBM cells was established by lentiviral transduction. Cell behaviors and polarization of primary microglia, microglia- and macrophage-like cells were investigated through indirect co-culture with GBM cells in vitro respectively. The PDCD10-induced release of chemokines was identified by a chemokine protein array. The cross-talk between GBM and microglia as well as macrophages was further studied using selective antagonist SB225002. Finally, an orthotopic homograft mouse model was employed to verify the results of in vitro experiments.

Results

Indirect co-culture with PDCD10-overexpressed GBM cells promoted proliferation and migration of microglia- and macrophage-like cells, and stimulated pro-tumorigenic polarization of primary microglia, microglia- and macrophage-like cells. Pdcd10-upregulated GBM cells triggered a nearly 6-fold increase of CXC motif chemokine ligand 2 (CXCL2) release, which in turn activated CXC chemokine receptor 2 (CXCR2) and downstream Erk1/2 and Akt signaling in primary microglia, microglia- and macrophage-like cells. The blockage of CXCR2 signaling with specific inhibitor (SB225002) abolished microglia- and macrophage-like cell migration induced by PDCD10-upregulated GBM cells. Moreover, Pdcd10-upregulated GL261 cells promoted GAMs recruitment and tumor growth in vivo.

Conclusion

Our study demonstrates that overexpression of PDCD10 in GBM recruits and activates microglia/macrophages, which in turn promotes tumor progression. CXCL2-CXCR2 signaling mediated by PDCD10 is potentially involved in the crosstalk between GBM cells and GAMs.

Genetic syndromes with vascular malformations - update on molecular background and diagnostics

Vascular malformations are present in a great variety of congenital syndromes, either as the predominant or additional feature. They pose a major challenge to the clinician: due to significant phenotype overlap, a precise diagnosis is often difficult to obtain, some of the malformations carry a risk of life threatening complications and, for many entities, treatment is not well established. To facilitate their recognition and aid in differentiation, we present a selection of notable congenital disorders of vascular system development, distinguishing between the heritable germinal and sporadic somatic mutations as their causes. Clinical features, genetic background and comprehensible description of molecular mechanisms is provided for each entity.

Novel cytokinetic ring components drive negative feedback in cortical contractility

Actomyosin cortical contractility drives many cell shape changes including cytokinetic furrowing. While positive regulation of contractility is well characterized, counterbalancing negative regulation and mechanical brakes are less well understood. The small GTPase RhoA is a central regulator, activating cortical actomyosin contractility during cytokinesis and other events. Here we report how two novel cytokinetic ring components, GCK-1 (germinal center kinase-1) and CCM-3 (cerebral cavernous malformations-3), participate in a negative feedback loop among RhoA and its cytoskeletal effectors to inhibit contractility. GCK-1 and CCM-3 are recruited by active RhoA and anillin to the cytokinetic ring, where they in turn limit RhoA activity and contractility. This is evidenced by increased RhoA activity, anillin and nonmuscle myosin II in the cytokinetic ring, and faster cytokinetic furrowing, following depletion of GCK-1 or CCM-3. GCK-1 or CCM-3 depletion also reduced RGA-3 levels in pulses and increased baseline RhoA activity and pulsed contractility during zygote polarization. Together, our results suggest that GCK-1 and CCM-3 regulate cortical actomyosin contractility via negative feedback. These findings have implications for the molecular and cellular mechanisms of cerebral cavernous malformation pathologies.

Ethanol-Induced Alterations in Placental and Fetal Cerebrocortical Annexin-A4 and Cerebral Cavernous Malformation Protein 3 Are Associated With Reductions in Fetal Cortical VEGF Receptor Binding and Microvascular Density

Jegou et al. (2012) have reported prenatal alcohol exposure (PAE)-induced reductions of angiogenesis-related proteins in mouse placenta. These effects were associated with striking alterations in microvascular development in neonatal cerebral cortex. Here, we employed a rat model of moderate PAE to search for additional proteins whose placental and fetal cortical expression is altered by PAE, along with a subsequent examination of fetal cerebral cortical alterations associated with altered protein expression. Long-Evans rat dams voluntarily consumed either a 0 or 5% ethanol solution 4 h each day throughout gestation. Daily ethanol consumption, which resulted in a mean peak maternal serum ethanol concentration of 60.8 mg/dL, did not affect maternal weight gain, litter size, or placental or fetal body weight. On gestational day 20, rat placental: fetal units were removed by Caesarian section. Placental protein expression, analyzed by 2D-PAGE – tandem mass spectroscopy, identified a total of 1,117 protein spots, 20 of which were significantly altered by PAE. To date, 14 of these PAE-altered proteins have been identified. Western blotting confirmed the alterations of two of these placental proteins, namely, annexin-A4 (ANX-A4) and cerebral cavernous malformation protein 3 (CCM-3). Specifically, PAE elevated ANX-A4 and decreased CCM-3 in placenta. Subsequently, these two proteins were measured in fetal cerebral cortex, along with radiohistochemical studies of VEGF binding and histofluorescence studies of microvascular density in fetal cerebral cortex. PAE elevated ANX-A4 and decreased CCM-3 in fetal cerebral cortex, in a pattern similar to the alterations observed in placenta. Further, both VEGF receptor binding and microvascular density and orientation, measures that are sensitive to reduced CCM-3 expression in developing brain, were significantly reduced in the ventricular zone of fetal cerebral cortex. These results suggest that the expression angiogenesis-related proteins in placenta might serve as a biomarker of ethanol-induced alterations in microvascular development in fetal brain.

Effects of programmed cell death protein 10 on fecundity in Schistosoma japonicum

Programmed cell death protein 10 (PCDP10) is widely distributed in animal tissues and exerts extensive biological effects. This study aimed to investigate the effect of Schistosoma japonicum PCDP10 (SjPCDP10) on the fecundity of schistosomes. We performed real-time PCR to assess Sjpcdp10 expression levels at different developmental stages of S. japonicum. Immunoprotection against S. japonicum was assessed in vivo in mice, and Sjpcdp10 expression was inhibited via RNA interference (RNAi) to determine its role in fecundity. Real-time PCR analysis revealed that Sjpcdp10 mRNA was expressed during different developmental stages in S. japonicum, reaching maximum and minimum levels in female worms and lung-stage schistosomula, respectively. Recombinant SjPCDP10 had a molecular weight of approximately 28 kDa, displaying good immunogenicity but poor immunoprotection. SjPCDP10 was primarily localized in the egg, eggshell, epiphragm of adult worms, and especially the vitelline glands of female worms. RNAi-mediated knockdown of Sjpcdp10 by greater than 90%, and the protein expression decreased by 73%, reduced the number of eggs per female worm significantly more than RNAi-mediated knockdown of Egfp (negative control) (P < 0.05). The present results indicate that Sjpcdp10 knockdown affects the fecundity of schistosomes and may play a vital role in oogenesis.

Effects of programmed cell death protein 10 on the Schistosoma japonicum female reproductive system

This study aimed to investigate the effects of programmed cell death protein 10 (PCDP10) on the female reproductive system of Schistosoma japonicum, one of the major infectious agents of schistosomiasis. We found that PCDP10 was widely distributed in the integument, the worm parenchymal area, and the vitellarium of the female worm, but was localized to a lesser extent in the ovary and testicles. RNAi experiments successfully achieved gene knockdown, and the ultrastructural morphology of the adult reproductive organs was observed. The results demonstrated that, compared with those of the negative control group, the number of cortical granules around oocytes decreased and the number of immature oocyte cells increased. Fusion of yolk globules occurred, and the number and the diameter of yolk droplets decreased significantly. Real-time PCR showed that the expression of yolk glands reached its peak before ovulation and then decreased. The TUNEL assay results showed that apoptosis in the RNAi group was significantly higher than that in the negative control group. These results suggested that SjPCDP10 plays an important role in the female reproductive system. In conclusion, PCD10 is involved in oocyte growth and development, especially in eggshell formation, which may provide a reference for further elucidating the molecular mechanism of PCDP10 involved in egg formation and embryo development in Schistosoma japonicum.

First case of neutropenia and thrombocytopenia in the setting of cerebral cavernous malformation 3

Cerebral cavernous malformation 3 (CCM3) is a vascular malformation disorder causing brain slow-flow vascular parenchymal lesions. These lesions are the result of variants in the Programmed Cell Death Protein 10 (PDCD10) gene, located on 3q26.1. We report an 8-month-old patient who was presented with seizures and intracranial abscesses and was found to have a variant of PDCD10 on whole exome sequencing, representing, to our knowledge, the youngest case of CCM3 described in the literature. Her clinical course was complicated by the development of neutropenia, requiring granulocyte colony-stimulating factor, and thrombocytopenia, requiring intermittent platelet transfusions, with later development of B acute lymphoblastic leukemia 2 years after initial presentation. This case represents the first description in the literature of hematologic complications in the setting of CCM3. We hypothesize that these hematological manifestations are the result of alterations in the actin and microtubule cytoskeleton, affecting the process of hematopoiesis in a similar fashion to the documented effect of the PDCD10 variant on neuronal migration.

The association between prenatal alcohol exposure and protein expression in human placenta

BACKGROUND

The need for earlier recognition of children at risk for neurobehavioral problems associated with prenatal ethanol exposure (PAE) has prompted investigations of biomarkers prognostic for altered fetal development. Here, we examined whether PAE alters the expression of angiogenesis-related proteins and cytokines in human placenta in subjects from an Ethanol, Neurodevelopment, Infant and Child Health prospective cohort.

METHODS

PAE was ascertained by screening questionnaires, Time-line Follow-back interviews and a panel of ethanol biomarkers at two study visits. After delivery, placental tissue samples were collected for protein analysis.

RESULTS

No significant differences in the prevalence of substance use, demographic or medical characteristics were observed between the No PAE and PAE groups. PAE was associated with significant reductions in placental expression of VEGFR2 and annexin-A4, while the levels of VEGFR1 and CCM-3 trended downward. A trend toward higher expression of the cytokines TNF-α and IL-13 was also observed in the PAE group. Receiver operating characteristic analyses of the data demonstrated a moderate-to-high degree of diagnostic accuracy for individual placental proteins. Combinations of proteins substantially increased their ability to differentiate between PAE and No PAE subjects.

CONCLUSIONS

These results establish the feasibility of harvesting placental tissue for protein analyses of PAE in a prospective manner. In addition, given the importance of vascular remodeling in both placenta and developing brain, the role of angiogenic and cytokine proteins in this process warrants further investigation for their utility for predicting alterations in brain development, as well as their mechanistic role in PAE-induced pathology.

Cerebrovascular disorders associated with genetic lesions

Cerebrovascular disorders are underlain by perturbations in cerebral blood flow and abnormalities in blood vessel structure. Here, we provide an overview of the current knowledge of select cerebrovascular disorders that are associated with genetic lesions and connect genomic findings with analyses aiming to elucidate the cellular and molecular mechanisms of disease pathogenesis. We argue that a mechanistic understanding of genetic (familial) forms of cerebrovascular disease is a prerequisite for the development of rational therapeutic approaches, and has wider implications for treatment of sporadic (non-familial) forms, which are usually more common.

Loss of programmed cell death 10 activates tumor cells and leads to temozolomide-resistance in glioblastoma

PURPOSE

Glioblastoma (GBM) is one of the most aggressive and incurable primary brain tumors. Identification of novel therapeutic targets is an urgent priority. Programmed cell death 10 (PDCD10), a ubiquitously expressed apoptotic protein, has shown a dual function in different types of cancers and in chemo-resistance. Recently, we reported that PDCD10 was downregulated in human GBM. The aim of this study was to explore the function of PDCD10 in GBM cells.

METHODS

PDCD10 was knocked down in three GBM cell lines (U87, T98g and LN229) by lentiviral-mediated shRNA transduction. U87 and T98g transduced cells were used for phenotype study and LN229 and T98g cells were used for apoptosis study. The role of PDCD10 in apoptosis and chemo-resistance was investigated after treatment with staurosporine and temozolomide. A GBM xenograft mouse model was used to confirm the function of PDCD10 in vivo. A protein array was performed in PDCD10-knockdown and control GBM cells.

RESULTS

Knockdown of PDCD10 in GBM cells promoted cell proliferation, adhesion, migration, invasion, and inhibited apoptosis and caspase-3 activation. PDCD10-knockdown accelerated tumor growth and increased tumor mass by 2.1-fold and led to a chemo-resistance of mice treated with temozolomide. Immunostaining revealed extensive Ki67-positive cells and less activation of caspase-3 in PDCD10-knockdown tumors. The protein array demonstrated an increased release of multiple growth factors from PDCD10-knockdown GBM cells.

CONCLUSIONS

Loss of programmed cell death 10 activates tumor cells and leads to temozolomide-resistance in GBM, suggesting PDCD10 as a potential target for GBM therapy.

Combined HMG-COA reductase and prenylation inhibition in treatment of CCM

Cerebral cavernous malformations (CCMs) are common vascular anomalies that develop in the central nervous system and, more rarely, the retina. The lesions can cause headache, seizures, focal neurological deficits, and hemorrhagic stroke. Symptomatic lesions are treated according to their presentation; however, targeted pharmacological therapies that improve the outcome of CCM disease are currently lacking. We performed a high-throughput screen to identify Food and Drug Administration-approved drugs or other bioactive compounds that could effectively suppress hyperproliferation of mouse brain primary astrocytes deficient for CCM3. We demonstrate that fluvastatin, an inhibitor of 3-hydroxy-3-methyl-glutaryl (HMG)-CoA reductase and the N-bisphosphonate zoledronic acid monohydrate, an inhibitor of protein prenylation, act synergistically to reverse outcomes of CCM3 loss in cultured mouse primary astrocytes and in Drosophila glial cells in vivo. Further, the two drugs effectively attenuate neural and vascular deficits in chronic and acute mouse models of CCM3 loss in vivo, significantly reducing lesion burden and extending longevity. Sustained inhibition of the mevalonate pathway represents a potential pharmacological treatment option and suggests advantages of combination therapy for CCM disease.

A Sterile 20 Family Kinase and Its Co-factor CCM-3 Regulate Contractile Ring Proteins on Germline Intercellular Bridges

Germ cells in most animals are connected by intercellular bridges, actin-based rings that form stable cytoplasmic connections between cells promoting communication and coordination [1]. Moreover, these connections are required for fertility [1, 2]. Intercellular bridges are proposed to arise from stabilization of the cytokinetic ring during incomplete cytokinesis [1]. Paradoxically, proteins that promote closure of cytokinetic rings are enriched on stably open intercellular bridges [1, 3, 4]. Given this inconsistency, the mechanism of intercellular bridge stabilization is unclear. Here, we used the C. elegans germline as a model for identifying molecular mechanisms regulating intercellular bridges. We report that bridges are actually highly dynamic, changing size at precise times during germ cell development. We focused on the regulation of bridge stability by anillins, key regulators of cytokinetic rings and cytoplasmic bridges [1, 4-7]. We identified GCK-1, a conserved serine/threonine kinase [8], as a putative novel anillin interactor. GCK-1 works together with CCM-3, a known binding partner [9], to promote intercellular bridge stability and limit localization of both canonical anillin and non-muscle myosin II (NMM-II) to intercellular bridges. Additionally, we found that a shorter anillin, known to stabilize bridges [4, 7], also regulates NMM-II levels at bridges. Consistent with these results, negative regulators of NMM-II stabilize intercellular bridges in the Drosophila egg chamber [10, 11]. Together with our findings, this suggests that tuning of myosin levels is a conserved mechanism for the stabilization of intercellular bridges that can occur by diverse molecular mechanisms.

Disruptions in asymmetric centrosome inheritance and WDR62-Aurora kinase B interactions in primary microcephaly

Recessive mutations in WD repeat domain 62 (WDR62) cause microcephaly and a wide spectrum of severe brain malformations. Disruption of the mouse ortholog results in microcephaly underlain by reduced proliferation of neocortical progenitors during late neurogenesis, abnormalities in asymmetric centrosome inheritance leading to neuronal migration delays, and altered neuronal differentiation. Spindle pole localization of WDR62 and mitotic progression are defective in patient-derived fibroblasts, which, similar to mouse neocortical progenitors, transiently arrest at prometaphase. Expression of WDR62 is closely correlated with components of the chromosome passenger complex (CPC), a key regulator of mitosis. Wild type WDR62, but not disease-associated mutant forms, interacts with the CPC core enzyme Aurora kinase B and staining of CPC components at centromeres is altered in patient-derived fibroblasts. Our findings demonstrate critical and diverse functions of WDR62 in neocortical development and provide insight into the mechanisms by which its disruption leads to a plethora of structural abnormalities.

Cerebral Cavernous Malformations: Review of the Genetic and Protein-Protein Interactions Resulting in Disease Pathogenesis

Mutations in the genes KRIT1, CCM2, and PDCD10 are known to result in the formation of cerebral cavernous malformations (CCMs). CCMs are intracranial lesions composed of aberrantly enlarged “cavernous” endothelial channels that can result in cerebral hemorrhage, seizures, and neurologic deficits. Although these genes have been known to be associated with CCMs since the 1990s, numerous discoveries have been made that better elucidate how they and their subsequent protein products are involved in CCM pathogenesis. Since our last review of the molecular genetics of CCM pathogenesis in 2012, breakthroughs include a more thorough understanding of the protein structures of the gene products, involvement with integrin proteins, and MEKK3 signaling pathways, and the importance of CCM2–PDCD10 interactions. In this review, we highlight the advances that further our understanding of the “gene to protein to disease” relationships of CCMs.

Downregulation of programmed cell death 10 is associated with tumor cell proliferation, hyperangiogenesis and peritumoral edema in human glioblastoma

Background

Neovascularization and peritumoral edema are hallmarks of glioblastoma (GBM). Programmed cell death 10 (PDCD10) plays a pivotal role in regulating apoptosis, neoangiogenesis and vessel permeability and is implicated in certain tumor signaling pathways. However, little is known about PDCD10 in GBM. We aimed to investigate the expression pattern of PDCD10 and to identify the association of its expression with some molecular and clinical parameters in human GBM.

Methods

mRNA and protein expression of PDCD10 were examined respectively by real-time RT-PCR and Western blotting in GBM (n = 27), astrocytoma grade II (n = 13) and control (n = 11). The protein level of p-Akt and GFAP was detected by Western blot. Double-imunofluorecent staining was performed to reveal the cellular expression profile of PDCD10. Brain edema and microvascular density (MVD) were respectively analyzed based on pre-operative MRI and after laminin immnostaining. MGMT promoter methylation was detected by methylation specific PCR.

Results

mRNA and protein levels of PDCD10 were significantly downregulated in GBM, concomitantly accompanied by the activation of Akt. PDCD10 immunoreactivity was absent in proliferating tumor cells, endothelial cells and GFAP-positive cells, but exclusively present in the hypoxic pseudopalisading cells which underwent apoptosis. Moreover, loss of PDCD10 was associated with a higher MVD and a more severe peritumoral edema but not with MGMT promoter methylation in GBM.

Conclusion

We report for the first time that PDCD10 expression is downregulated in GBM, which is associated with the activation of Akt signaling protein. PDCD10 is potentially implicated in tumor proliferation and apoptosis, hyperangiogenesis and peritumoral edema in GBM.

Rho GTPase signalling in cell migration

Cells migrate in multiple different ways depending on their environment, which includes the extracellular matrix composition, interactions with other cells, and chemical stimuli. For all types of cell migration, Rho GTPases play a central role, although the relative contribution of each Rho GTPase depends on the environment and cell type. Here, I review recent advances in our understanding of how Rho GTPases contribute to different types of migration, comparing lamellipodium-driven versus bleb-driven migration modes. I also describe how cells migrate across the endothelium. In addition to Rho, Rac and Cdc42, which are well known to regulate migration, I discuss the roles of other less-well characterized members of the Rho family.

Rho GTPase signalling in cell migration

Cells migrate in multiple different ways depending on their environment, which includes the extracellular matrix composition, interactions with other cells, and chemical stimuli. For all types of cell migration, Rho GTPases play a central role, although the relative contribution of each Rho GTPase depends on the environment and cell type. Here, I review recent advances in our understanding of how Rho GTPases contribute to different types of migration, comparing lamellipodium-driven versus bleb-driven migration modes. I also describe how cells migrate across the endothelium. In addition to Rho, Rac and Cdc42, which are well known to regulate migration, I discuss the roles of other less-well characterized members of the Rho family.

Loss of endothelial programmed cell death 10 activates glioblastoma cells and promotes tumor growth

BACKGROUND

Neo-angiogenesis is a hallmark of glioblastoma (GBM) and is sustained by autocrine and paracrine interactions between neoplastic and nonneoplastic cells. Programmed cell death 10 (PDCD10) is ubiquitously expressed in nearly all tissues and plays crucial roles in regulating angiogenesis and apoptosis. We recently discovered the absence of PDCD10 expression in the tumor vessels of GBM patients. This raised the hypothesis that loss of endothelial PDCD10 affected GBM cell phenotyping and tumor progression.

METHODS

Endothelial PDCD10 was silenced by siRNA and lentiviral shRNA. The tumor cell phenotype was studied in direct and indirect co-culture of endothelial cells (ECs) with U87 or LN229. Angiogenic protein array was performed in the media of PDCD10-silenced ECs. Tumor angiogenesis and tumor growth were investigated in a human GBM xenograft mouse model.

RESULTS

Endothelial silence of PDCD10 significantly stimulated tumor cell proliferation, migration, adhesion, and invasion and inhibited apoptosis in co-cultures. Stable knockdown of endothelial PDCD10 increased microvessel density and the formation of a functional vascular network, leading to a 4-fold larger tumor mass in mice. Intriguingly, endothelial deletion of PDCD10 increased (≥2-fold) the release of 20 of 55 tested proangiogenic factors including VEGF, which in turn activated Erk1/2 and Akt in GBM cells.

CONCLUSIONS

For the first time, we provide evidence that loss of endothelial PDCD10 activates GBM cells and promotes tumor growth, most likely via a paracrine mechanism. PDCD10 shows a tumor-suppressor-like function in the cross talk between ECs and tumor cells and is potentially implicated in GBM progression.

The cerebral cavernous malformation 3 gene is necessary for senescence induction

Mutations in cerebral cavernous malformation 3 gene are known to result in development of vascular malformations and have recently been proposed to also give rise to meningiomas. We report in this study that lack of CCM3 unexpectedly impairs the senescence response of cells, and this is related to the inability of CCM3-deficient cells to induce the C/EBPβ transcription factor and implement the senescence-associated secretory phenotype. Induction of C/EBPβ and cytokines is also impaired in the absence of CCM3 in response to cytokines in nonsenescent cells, pointing to it being a primary defect and not secondary to impaired senescence. CCM3-deficient cells also have a defect in autophagy at late passages of culture, and this defect is also not dependent on impaired senescence, as it is evident in immortal cells after nutrient starvation. Further, these two defects may be related, as enforcing autophagy in CCM3-deficient late passage cells increases C/EBPβ cytokine expression. These results broaden our knowledge on the mechanisms by which CCM3 deficiency results in disease and open new avenues of research into both CCM3 and senescence biology.

Exceptional aggressiveness of cerebral cavernous malformation disease associated with PDCD10 mutations

PURPOSE

The phenotypic manifestations of cerebral cavernous malformation disease caused by rare PDCD10 mutations have not been systematically examined, and a mechanistic link to Rho kinase-mediated hyperpermeability, a potential therapeutic target, has not been established.

METHODS

We analyzed PDCD10 small interfering RNA-treated endothelial cells for stress fibers, Rho kinase activity, and permeability. Rho kinase activity was assessed in cerebral cavernous malformation lesions. Brain permeability and cerebral cavernous malformation lesion burden were quantified, and clinical manifestations were assessed in prospectively enrolled subjects with PDCD10 mutations.

RESULTS

We determined that PDCD10 protein suppresses endothelial stress fibers, Rho kinase activity, and permeability in vitro. Pdcd10 heterozygous mice have greater lesion burden than other Ccm genotypes. We demonstrated robust Rho kinase activity in murine and human cerebral cavernous malformation vasculature and increased brain vascular permeability in humans with PDCD10 mutation. Clinical phenotype is exceptionally aggressive compared with the more common KRIT1 and CCM2 familial and sporadic cerebral cavernous malformation, with greater lesion burden and more frequent hemorrhages earlier in life. We first report other phenotypic features, including scoliosis, cognitive disability, and skin lesions, unrelated to lesion burden or bleeding.

CONCLUSION

These findings define a unique cerebral cavernous malformation disease with exceptional aggressiveness, and they inform preclinical therapeutic testing, clinical counseling, and the design of trials.Genet Med 17 3, 188-196.

Cdk5 regulates multiple cellular events in neural development, function and disease

Cyclin-dependent kinases (CDKs) generally regulate cell proliferation in dividing cells, including neural progenitors. In contrast, an unconventional CDK, Cdk5, is predominantly activated in post-mitotic cells, and involved in various cellular events, such as microtubule and actin cytoskeletal organization, cell-cell and cell-extracellular matrix adhesions, and membrane trafficking. Interestingly, recent studies have indicated that Cdk5 is associated with several cell cycle-related proteins, Cyclin-E and p27(kip1) . Taking advantage of multiple functionality, Cdk5 plays important roles in neuronal migration, layer formation, axon elongation and dendrite arborization in many regions of the developing brain, including cerebral cortex and cerebellum. Cdk5 is also required for neurogenesis at least in the cerebral cortex. Furthermore, Cdk5 is reported to control neurotransmitter release at presynaptic sites, endocytosis of the NMDA receptor at postsynaptic sites and dendritic spine remodeling, and thereby regulate synaptic plasticity and memory formation and extinction. In addition to these physiological roles in brain development and function, Cdk5 is associated with many neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis. In this review, I will introduce the physiological and pathological roles of Cdk5 in mammalian brains from the viewpoint of not only in vivo phenotypes but also its molecular and cellular functions.