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We aimed to examine whether golgi protein GOLPH3 could affect the secretion of glioma cell-derived exosomes. The exosomes were extracted by ultra-centrifugation from the supernatant of U251 and U87 cell cultures and identified by transmission electron microscopy (TEM), Malvern analyzer, and western blot. The quantity of exosomes was examined by measuring the total protein levels and the number of multiple vesicle bodies (MVBs), the source of exosomes. The exosome miRNAs were analyzed by high-throughput sequencing followed by GO and KEGG analysis, and validated by qRT-PCR. GOLPH3 could not affect the total protein levels of exosomes and the number of MVBs. However, we found 149 differentially expressed miRNAs in exosomes between vector and GOLPH3 over-expression group, and 14 miRNAs were only examined in GOLPH3 over-expression cells. The predicted target genes of these miRNAs had functions in binding and catalytic activity, which were enriched in the pathways of endocytosis, RNA transportation, thyroid hormone signaling and miRNAs in cancer. GOLPH3 could not affect the quantity of exosomes, but rather contribute to miRNA expression in exosomes, which may play some functions in the promotion effect of GOLPH3 on glioma development. [ABSTRACT FROM AUTHOR]

We previously reported that LATS2, the upstream serine/threonine kinase of Yes-associated protein (YAP), is downregulated in gliomas and exhibits negative correlation with the prognosis of glioma patients. In this work, we aimed to explore the role and mechanism of large tumor suppressor kinase (LATS2) in the progression of malignant gliomas. We found that over-expression of LATS2 inhibited glioma cell proliferation and migration/invasion, while LATS2 downregulation promoted them. Mechanistically, LATS2 promoted the phosphorylation of YAP without affecting YAP mRNA expression. Inconsistent with some previous reports, both YAPWT and YAP5SA did not affect the level of LATS2, suggesting that LATS2 did not form a feedback loop with YAP in gliomas. Furthermore, mammalian Ste20-like kinases (MST1) over-expression did not affect the phosphorylation of YAP, suggesting that MST1 may not be the essential upstream serine/threonine kinase of Hippo/YAP pathway in gliomas. Together, LATS2 inhibits glioma cell proliferation and migration/invasion by inactivating YAP. [ABSTRACT FROM AUTHOR]

Introduction: Our recent work reported that GOLPH3 promotes glioma progression via inhibiting endocytosis and degradation of EGFR. The current study aimed to explore the potential regulating mechanism of GOLPH3 on JAK2-STAT3 signaling, a downstream effector of EGFR, in glioma progression.Methods: The expression of JAK2, STAT3 and GOLPH3 in glioma tissues was detected by western blotting, tissue microarray and immunohistochemistry. The U251 and U87 cells with GOLPH3 down-regulation or over-expression were generated by lentivirus system. The effects of GOLPH3 on the activity of JAK2 and STAT3 were detected by western blotting and reverse transcription polymerase chain reaction. Co-immunoprecipitation was used to detect the association of GOLPH3 with JAK2 and STAT3. Cell proliferation was detected by CCK8 and EdU assay.Results: The level of JAK2, STAT3 and GOLPH3 were significantly up-regulated and exhibited pairwise correlation in human glioma tissues. The level of p-JAK2 and p-STAT3, as well as the mRNA and protein levels of cyclin D1 and c-myc, two target genes of STAT3, decreased after GOLPH3 down-regulation, while they increased after GOLPH3 over-expression both in U251 and U87 cells. Interestingly, GOLPH3, JAK2 and STAT3 existed in the same protein complex and GOLPH3 affected the interaction of JAK2 and STAT3. Importantly, down-regulation of STAT3 partially abolished cell proliferation induced by GOLPH3 over-expression.Conclusions: GOLPH3 may act as a scaffold protein to regulate JAK2-STAT3 interaction and then its activation, which therefore mediates the effect of GOLPH3 on cell proliferation. [ABSTRACT FROM AUTHOR]

Dysregulation of Hippo/YAP signaling leads to aberrant cell growth and neoplasia. Although the roles and regulation of Hippo/YAP signaling were extensively studied in cancer biology recently, study systematically checking the expression pattern of core components of this pathway at the tumor tissue level remains lacking. In this study, we thoroughly examined the profile of core components of Hippo/YAP signaling in patient specimens both at the mRNA and at protein levels. We found that the mRNA level of YAP1/TAZ and their target genes, CRY61, CTGF, and BIRC5, was remarkably amplified in glioma tissues. Consistently, the protein level of YAP1/TAZ increased and meanwhile those of p-YAP1/p-TAZ and LATS1/2 decreased in gliomas. Unexpectedly, both the mRNA and protein levels of MST1/2 increased in the glioma tissues, inconsistent with its presumed tumor suppressor identity. In addition, over-expression of LATS2 decreased, while over-expression of YPA1 increased the cell proliferation ability. Furthermore, based on the data from the free public database, YAP1/TAZ and BIRC5 were positively associated with the prognosis of glioma patients, while LATS1/2 exhibited negative correlation with the glioma patient prognosis. Collectively, we deduce that, in glioma tissue context, MST1/2 may not be the essential component of the hippo/YAP pathway. Moreover, our findings uncover a new evidence supporting that YAP1/TAZ-BIRC5 might be abnormally activated due to LATS1/2 down-regulation, which in turn promote the occurrence and development of gliomas, paving the way to identify the potential therapeutic molecular target for gliomas. [ABSTRACT FROM AUTHOR]

Isoprenylation is a posttranslational modification that transfers farnesyl pyrophosphate (FPP) or geranylgeranyl pyrophosphate (GGPP) to cysteine residues of a particular set of proteins, causing their localization to the plasma membrane and other cellular compartments and so rendering them biologically active. Such a modification process, catalyzed by protein prenyltransferase including farnesyltransferase (FT), geranylgeranyltransferase I (GGTI), and geranylgeranyltransferase II (GGTII), is required for the transforming activity of many oncogenic proteins, including some RAS family members. In the past three decades, prenyltransferase has been extensively studied as a promising cancer therapeutic target in vitro, in animal models, and in the clinic. Recently, a growing number of studies suggest that prenyltransferases and the substrates FPP and GGPP also play fundamental roles in nervous system development and brain disorders. However, a systemic review about the advances of prenyltransferases in the field of neuroscience is lacking so far. Herein, we give a brief introduction for the structure and distribution of GGTI and comprehensively updated the recent advances of GGTI in neuronal dendritogenesis/synaptogenesis and in learning/memory-related behavioral performance. More importantly, we discussed the involvement of GGTI and its substrate GGPP in neurodegenerative disorders, such as aging, Alzheimer's disease, multiple sclerosis, and Niemann-Pick disease type C. The role of FT-FPP and GGTII is mentioned as well to compare with GGTI in these physiological and pathological processes. We hope that this systematical review about what we know about GGTI research in the brain can stimulate further studies on the underlying mechanism of GGTI-mediated isoprenylation in the pathogenesis of neurodegenerative and neurodevelopmental disorders. [ABSTRACT FROM AUTHOR]

Drosophila lethal (2) giant larvae (lgl) has been reported as a tumor suppressor and could regulate the Drosophila hippo signaling. Human giant larvae-1(Hugl-1), one human homologue of Drosophila lgl, also has been reported to be involved in the development of some human cancers. However, whether Hugl-1 is associated with the pathogenesis of malignant gliomas remains poorly understood. In the present work, we examined the effect of Hugl-1 on glioma cell growth both in vitro and in vivo. Firstly, we found that Hugl-1 protein levels decreased in the human glioma tissues, suggesting that Hugl-1 is involved in glioma progression. Unfortunately, either stably or transiently over-expressing Hugl-1 did not affect glioma cell proliferation in vitro. In addition, Hugl-1 over-expression did not regulate hippo signaling pathway. Interestingly, over-expression of Hugl-1 not only inhibited gliomagenesis but also markedly inhibited cell proliferation and promoted the apoptosis of U251 cells in an orthotopic model of nude mice. Taken together, this study provides the evidence that Hugl-1 inhibits glioma cell growth in intracranial model of nude mice, suggesting that Hugl-1 might be a potential tumor target for glioma therapy. [ABSTRACT FROM AUTHOR]

Plumbagin, a natural quinonoid constituent isolated from the root of medicinal plant Plumbago zeylanica L, has exhibited anti-tumor and anti-proliferative activities in various tumor cell lines as well as in animal tumor models. However, its anticancer effects and the mechanisms underlying its suppression of glioma cell growth have not been elucidated. Oncogenic transcription factor Forkhead Box M1 (FOXM1) has garnered particular interest in recent years as a potential target for the prevention and/or therapeutic intervention in glioma, nevertheless, less information is currently available regarding FOXM1 inhibitor. Here, we reported that plumbagin could effectively inhibit cell proliferation, migration and invasion and induce apoptosis of glioma cells. Cell cycle assay showed that plumbagin induced G2/M arrest. Interestingly, we found that plumbagin decreased the expression of FOXM1 both at mRNA level and protein level. Plumbagin also inhibited the transactivation ability of FOXM1, resulting in down-regulating the expression of FOXM1 downstream target genes, such as cyclin D1, Cdc25B, survivin, and increasing the expression of p21 and p27. Most importantly, down-regulation of FOXM1 by siFOXM1 transfection enhanced plumbagin-induced change in viability. On the contrary, over-expression of FOXM1 by cDNA transfection reduced plumbagin-induced glioma cell growth inhibition. These results suggest that plumbagin exhibits its anticancer activity partially by inactivation of FOXM1 signaling pathway in glioma cells. Our findings indicate that plumbagin may be considered as a potential natural FOXM1 inhibitor, which could contribute to the development of new anticancer agent for therapy of gliomas. [ABSTRACT FROM AUTHOR]

Mammalian sterile 20-like 1 (Mst1), an upstream serine/threonine-specific protein kinase of the Hippo pathway, is reported to play important roles in tumor suppression and organ size regulation in mammals via regulating cell proliferation and survival. However, whether it is involved in the pathogenesis of malignant gliomas remains poorly understood. Therefore, in the present work, we examined the effect and mechanism of Mst1 on the proliferation and apoptosis of malignant glioma cells. The cell proliferation and growth of glioma cells were examined by EdU incorporation and CCK-8 assay. In addition, the cell apoptosis was assessed by flow cytometry. We found that down-regulation of Mst1 promoted glioma cell proliferation and growth, but inhibited the cell apoptosis. Consistent with this, over-expression of Mst1 inhibited glioma cell proliferation and growth. Interestingly, Mst1 did not affect the phosphorylation of YAP1, the key downstream molecule of Hippo pathway. However, Mst1 was found to bind to AKT in glioma cell and negatively regulated AKT and mTOR activity. Finally, the increased cell proliferation rate induced by Mst1 down-regulation was partially abolished by down-regulation of AKT1. Meanwhile, glioma cell growth inhibition induced by Mst1 over-expression was partially rescued by over-expression of AKT1. Taken together, these findings suggest that Mst1 regulates proliferation of glioma cells via AKT/mTOR signaling pathway. [ABSTRACT FROM AUTHOR]

Fyn-related kinase (FRK), a member of Src-related tyrosine kinases, is recently reported to function as a potent tumor suppressor in several cancer types. Our previous study has also shown that FRK over-expression inhibited the migration and invasion of glioma cells. However, the mechanism of FRK effect on glioma cell migration and invasion, a feature of human malignant gliomas, is still not clear. In this study, we found that FRK over-expression increased the protein level of N-cadherin, but not E-cadherin. Meanwhile, FRK over-expression promoted β-catenin translocation to the plasma membrane, where it formed complex with N-cadherin, while decreased β-catenin level in the nuclear fraction. In addition, down-regulation of N-cadherin by siRNA promoted the migration and invasion of glioma U251 and U87 cells and abolished the inhibitory effect of FRK on glioma cell migration and invasion. In summary, these results indicate that FRK inhibits migration and invasion of human glioma cells by promoting N-cadherin/β-catenin complex formation. [ABSTRACT FROM AUTHOR]

The Fyn related kinase (FRK) is a noteworthy member of the Src non-receptor tyrosine kinase family for its distinctive tumor suppressive function. Recently, we have shown that FRK plays a protective role against the progression of glioma by suppressing cell migration and invasion. However, it is unclear whether the cell growth of glioma is also regulated by FRK and by which mechanism FRK alters its specific biological functions. In the current study, we found that FRK over-expression significantly suppressed the proliferation of glioma cells. In contrast, FRK knockdown by siRNA promoted glioma cell growth. In addition, FRK over-expression caused G phase arrest as well as apoptosis of glioma cells. Further investigation disclosed that FRK-induced G1 arrest was accompanied by down-regulation of hyperphosphorylated retinoblastoma protein (pRb), which led to the consequent suppression of E2F1. More importantly, we found that over-expression of FRK inhibited proper cyclin D1 accumulation in the nucleus of proliferating cells. Taken together, our results demonstrate a combined mechanism for the anti-proliferative effects of FRK by inhibiting cyclin D1 nucleus accumulation and pRb phosphorylation in glioma cells. [ABSTRACT FROM AUTHOR]

Glioblastoma is the most common and fatal human brain malignancy in adults with highly proliferative capacity. Despite advances in surgery and adjuvant therapy, the median survival of patients has changed little over recent decades. Identifying molecules critical for glioma development is significant for devising effective targeted therapy. We previously reported that Bex2, a member of the brain expressed X-linked gene family, promoted the progression of glioma by promoting cell proliferation. In the present study, we investigated the main mechanism of Bex2 promoting the proliferation of glioblastoma cells. We found that Bex2 downregulation inhibited glioma cell proliferation and the expression of NF-κB p65, but Bex2 overexpression promoted them. Similarly, the proliferation of glioma cells was inhibited by p65 downregulation but increased by p65 overexpression. In addition, Bex2 overexpression-induced cell proliferation was abolished by p65 downregulation. Furthermore, Bex2 with nuclear localization signal deleted no longer promoted p65 expression. In conclusion, this study demonstrates that Bex2 promotes proliferation of human glioblastoma cells via NF-κB signaling pathway and Bex2 nuclear location is critical for p65 expression. [ABSTRACT FROM AUTHOR]

Ubiquitin-specific protease 22 (USP22) exhibits an important function in tumor progression and oncogenesis. The aim of this study was to investigate the role of USP22 and the association with its potential targets in patients with glioma. To our knowledge, this is the first study that determines the relationship between USP22 expression and clinicopathological significance in glioma. In our study, USP22 protein levels were detected by Western blot analysis. The protein levels of USP22 in glioma tissues were significantly higher than non-tumors. The immunohistochemistry results showed that USP22 protein was overexpressed in glioma tissues compared with non-tumors. The higher the grade of gliomas, the higher the level of USP22 expression. Further, the results of Kaplan-Meier analysis indicated that patients with high USP22 expression had significantly worse overall survival than patients with low expression of USP22. It suggested that USP22 overexpression may be associated with poor prognosis in patients with glioma. It may represent a novel prognostic biomarker or a target for improving the treatment efficiency of patients with glioma. [ABSTRACT FROM AUTHOR]

Glioblastoma is a kind of highly aggressive and incurable tumor with an average survival time of 12 months in our currently available treatment. The invasive cells are the sources of tumor recurrence and mechanisms of invasion are largely unknown. Identification of candidate genes important for invasion and migration is a hot spot of cancer biology. As one member of Bex protein family, Bex2 has its functions in the development of the nervous system and neurological diseases. Bex2 plays great roles in breast cancer, but its function and mechanisms in glioma progression remain unclear. In this study, we found Bex2 overexpression promoted cell migration and invasion, while Bex2 downregulation inhibited them. Meanwhile, we observed that Bex2 downregulation increased N-cadherin but decreased the excretion of MMP-2. Taken together, these data suggested that Bex2 promoted the progression of glioma by promoting cell migration and invasion, and these effects might be mediated by N-cadherin and MMP-2. [ABSTRACT FROM AUTHOR]

Glioblastoma multiforme is a highly migratory and invasive brain tumor in which hypoxia inducible factor-1α (HIF-1α) plays important roles. However, the underlying mechanisms regulating the action of HIF-1α in glioma cell migration and invasion ability remain unclear. We reported here that HIF-1α was regulated by geranylgeranyltransferase I (GGTI), a protein prenylation transferase, and then promoted glioma cell migration and invasion. The migratory and invasive ability of glioma cells were enhanced by hypoxia treatment but inhibited by down-regulation of HIF-1α. GGTI activity inhibition or GGTI specific β subunit (GGTI β) knocking-down decreased HIF-1α protein level. In addition, down-regulation of GGTI β inhibited migration and invasion of glioma cells under hypoxia, while GGTI β over-expression promoted it. Furthermore, the effect of GGTI β over-expression on cell migration and invasion was abolished by HIF-1α down-regulation. In summary, our study showed, for the first time, that HIF-1α was regulated by protein prenylation transferase GGTI and mediated the effect of GGTI on glioma cell migration and invasion. [ABSTRACT FROM AUTHOR]

Geranylgeranyltransferase I (GGTase-I) is responsible for the posttranslational lipidation of several signaling proteins such as RhoA, Rac1, and Cdc42, which contribute to tumor development and metastasis. However, the role of GGTase-I in the progression of human glioma is largely unknown. Here, we provide the evidence that Rac1 mediates the effects of GGTase-I on the proliferation and apoptosis in human glioma cells. We found that GGTase-I was abundantly expressed in human primary glioma tissues. Inhibition or downregulation of GGTase-I markedly decreased the proliferation of glioma cells and induced their apoptosis, while overexpression of GGTase-I promoted cell growth in vitro. Inactivation of GGTase-I eliminated geranylgeranylation of RhoA and Rac1, prevented them from targeting to the plasma membrane, and inhibited Rac1 activity. Furthermore, overexpressing wild type or constitutively active Rac1 stimulated glioma cell growth, similar to the effect of GGTase-I overexpression. Importantly, overexpressing dominant-negative Rac1 or Rac1 with the prenylation site deleted or mutated abrogated GGTase-I-induced proliferation in glioma cells. These results confirm the view that geranylgeranylation is essential to the activity and localization of Rho family proteins and suggest that Rac1 is required for GGTase-I-mediated glioma growth. [ABSTRACT FROM AUTHOR]

The Fyn related kinase (FRK), a member of intracellular Src-related tyrosine kinases, was recently reported to function as a potent tumor suppressor in several cancer types. However, the expression level and functional significance of FRK in human malignant glioma, which is characterized by high migration and invasion potential, have never been investigated. We reported here that FRK reduced cell migration and invasion via inhibiting the c-Jun N-terminal protein kinase (JNK)/c-Jun signaling pathway in glioma cells. The mRNA and protein levels of FRK were significantly down-regulated in human primary glioma tissues. In addition, over-expression of FRK inhibited migration and invasion of glioma cells and excretion of the matrix metalloprotease 2 (MMP2), an index of migration and invasion. Furthermore, over-expression of FRK inhibited phosphorylation of JNK and c-Jun, which play important role in cell migration and invasion. Finally, the effects of FRK on cell migration and invasion and JNK/c-Jun inhibition were abolished by anisomycin, a JNK specific activator. In summary, these results clearly indicate that FRK may play a protective role against the progression of glioma by suppressing cell migration and invasion, suggesting that FRK needs to be further studied in its detail mechanism and clinical significant. [ABSTRACT FROM AUTHOR]