sphingosine-kinase and Glioma

MicroRNAs (miRNAs) are a conserved class of endogenous and short non-coding RNAs that post-transcriptionally regulate the expression of genes involved in diverse cellular processes. MiR-28-5p has been reported to be associated with several cancers, including human glioma. However, the roles of miR-28-5p in glioma development are poorly understood.. Sixteen human glioma tissues and paired adjacent normal tissues were acquired through the Gansu Provincial Hospital. We performed quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) to detect the miR-28-5p expression between 16 paired adjacent normal and glioma tissues, as well as the miR-28-5p expression between normal human astrocytes cells and five glioma cell lines. To examine the functional roles of the downregulated miR-28-5p in glioma, cell viability and colony formation assays were performed for the analysis of cell growth. We overexpressed miR-28-5p by transient transfection of miRNAs mimics and performed the transwell Matrigel invasion assay and transwell migration (without Matrigel) assay. To investigate the roles of miR-28-5p in SphK1 expression, Western blot and Real Time-Polymerase Chain Reaction assays were performed.. In this work, we demonstrated that miR-28-5p is downregulated in glioma tissues compared to the adjacent normal tissues. Functional studies showed that miR-28-5p overexpression inhibited the cell viability, colony formation and proliferation; meanwhile, it induced the cell apoptosis. The transwell invasion assay indicated that miR-28-5p blocked the invasion and migration of glioma cells. SphK1 (Sphingosine kinase 1 antibody) is predicted as a targeted candidate of miR-28-5p. Then, the Luciferase reporter assay, Western blot and Real Time-Polymerase Chain Reaction (PCR) validated that miR-28-5p negatively regulated SphK1 expression by directly targeting its 3'untranslated regions (3'UTR) in U87 cells. Furthermore, rescue assay suggested that overexpression of SphK1 without its 3'UTR could prevent the miR-28-5p from inducing the inhibition of glioma tumor cells.. Our findings showed that miR-28-5p could suppress the growth, invasion and migration of glioma cells by suppressing the SphK1 expression. The results demonstrated that miR-28-5p might serve as an important potential therapeutic target for glioma.

Topics: 3' Untranslated Regions; Apoptosis; Brain; Brain Neoplasms; Cell Line, Tumor; Cell Movement; Cell Proliferation; Down-Regulation; Gene Expression Regulation, Neoplastic; Gene Knockdown Techniques; Glioma; Humans; MicroRNAs; Neoplasm Invasiveness; Phosphotransferases (Alcohol Group Acceptor); Prognosis

Multicellular tumor spheroids (MCTSs) embedded in a matrix are re-emerging as a powerful alternative to monolayer-based cultures. The primary information gained from a three-dimensional model is the invasiveness of treatment-exposed MCTSs through the acquisition of light microscopy images. The amount and complexity of the acquired data and the bias arisen by their manual analysis are disadvantages calling for an automated, high-throughput analysis. We present a universal algorithm we developed with the scope of being robust enough to handle images of various qualities and various invasion profiles. The novelty and strength of our algorithm lie in: the introduction of a multi-step segmentation flow, where each step is optimized for each specific MCTS area (core, halo, and periphery); the quantification through the density of the two-dimensional representation of a three-dimensional object. This latter offers a fine-granular differentiation of invasive profiles, facilitating a quantification independent of cell lines and experimental setups. Progression of density from the core towards the edges influences the resulting density map thus providing a measure no longer dependent on the sole area size of MCTS, but also on its invasiveness. In sum, we propose a new method in which the concept of quantification of MCTS invasion is completely re-thought.

Topics: Algorithms; Animals; Computer Simulation; Dacarbazine; Enzyme Inhibitors; Glioblastoma; Glioma; High-Throughput Screening Assays; Humans; Image Processing, Computer-Assisted; Imaging, Three-Dimensional; Mice; Neoplasm Invasiveness; Phosphotransferases (Alcohol Group Acceptor); Rats; Spheroids, Cellular; Temozolomide; Time-Lapse Imaging; Tumor Cells, Cultured

To investigate the role of sphingosine kinase 1 (SphK1) in regulating the proliferation of hypoxia-exposed glioma cells in vitro and explore the possible molecular mechanisms.. Human glioblastoma U87MG cells was transfected with specific small interfering RNA (siRNA) constructs targeting SphK1, and the efficiency of SphK1 knockdown was validated by real-time PCR and Western blotting. The cells transfected with SphK1 siRNA and with a negative control siRNA were then exposed to 3% oxygen or 150 µmol/L CoCl2 to induce hypoxia. The cell proliferation and cell cycle changes following the exposure were evaluated with the Cell Counting Kit-8 and flow cytometry, respectively, and the intracellular Ca(2+) changes were monitored using Flou-4/AM under an inverted laser scanning confocal microscope.. SphK1 knockdown significantly reduced hypoxia-induced calcium reflux and suppressed the cell proliferation. Application of OAG, an activator of calcium channels, however, obviously enhanced the cell proliferation under hypoxia.. SphK1 promotes the proliferation of glioma cells under hypoxia via regulating calcium signaling.

Topics: Calcium Signaling; Cell Cycle; Cell Hypoxia; Cell Line, Tumor; Cell Proliferation; Glioblastoma; Glioma; Humans; Phosphotransferases (Alcohol Group Acceptor); RNA, Small Interfering

Sphingosine kinase (SphK), which is regulated by hypoxia, catalyses phosphorylation of sphingosine to produce sphingosine-1-phosphate, which stimulates invasiveness of gliomas. However, whether SphK is involved in proliferation of glioma cells under hypoxic conditions is not clearly understood. In this study, we have investigated the role of SphK in of proliferation glioma cells under hypoxia..   Effects of small interfering RNA (siRNA) on SphKs, SKI (inhibitor of SphK) and U0126 (inhibitor of ERK) on proliferation of glioma cells under hypoxia were studied using CCK-8 assay and flow cytometry. Protein expression profiles were evaluated by Western blot analysis.. SKI suppressed proliferation of glioma cells under hypoxia. Similarly, downregulation of SphKs by siRNA inhibited glioma cell proliferation, and the cell cycle was arrested in G(2) /M phase when SphK1 was inhibited. In addition, inhibition of SphK1 attenuated phosphorylation of ERK in hypoxic conditions. Furthermore, U0126 markedly inhibited cell population growth and arrested cells in G(2) /M as effectively as SKI. However, silencing SphK2 induced cell cycle arrest in the S phase and it showed little effect on hypoxia-induced activation of ERK..   SphK1 and SphK2 are involved in proliferation of glioma cells in hypoxic conditions through distinct signalling pathways. SphK1, but not SphK2, promotes cell population expansion in hypoxic conditions by activating ERK.

Topics: Base Sequence; Butadienes; Cell Hypoxia; Cell Line, Tumor; Cell Proliferation; Enzyme Inhibitors; Extracellular Signal-Regulated MAP Kinases; G2 Phase Cell Cycle Checkpoints; Glioblastoma; Glioma; Humans; Nitriles; Phosphotransferases (Alcohol Group Acceptor); Receptors, G-Protein-Coupled; RNA, Small Interfering; S Phase Cell Cycle Checkpoints

The aim of this study was to investigate the mechanism through which Sphingosine kinase-1 (SPHK1) exerts its anti-apoptosis activity in glioma cancer cells. We here report that dysregulation of SPHK1 alters the sensitivity of glioma to apoptosis both in vitro and in vivo. Further mechanistic study examined the expression of Bcl-2 family members, including Bcl-2, Mcl-1, Bax and Bim, in SPHK1-overexpressing glioma cells and revealed that only pro-apoptotic Bim was downregulated by SPHK1. Moreover, the transcriptional level of Bim was also altered by SPHK1 in glioma cells. We next confirmed the correlation between SPHK1 and Bim expression in primary glioma specimens. Importantly, increasing SPHK1 expression in glioma cells markedly elevated Akt activity and phosphorylated inactivation of FOXO3a, which led to downregulation of Bim. A pharmacological approach showed that these effects of SPHK1 were dependent on phosphatidylinositol 3-kinase (PI3K). Furthermore, effects of SPHK1 on Akt/FOXO3a/Bim pathway could be reversed by SPHK1 specific RNA interference or SPHK1 inhibitor. Collectively, our results indicate that regulation of the Akt/FOXO3a/Bim pathway may be a novel mechanism by which SPHK1 protects glioma cells from apoptosis, thereby involved in glioma tumorigenesis.

Topics: Animals; Apoptosis; Apoptosis Regulatory Proteins; Bcl-2-Like Protein 11; Blotting, Western; Brain Neoplasms; Forkhead Box Protein O3; Forkhead Transcription Factors; Glioma; Humans; Immunoenzyme Techniques; Luciferases; Membrane Proteins; Mice; Mice, Nude; Phosphatidylinositol 3-Kinase; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor); Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; RNA, Small Interfering; Signal Transduction; Tumor Cells, Cultured

Sphingosine-1-phosphate (S1P) is an important bioactive sphingolipid involved in angiogenesis and lymphangiogenesis, 2 important processes that influence the growth, survival, and spread of tumors. S1P acts as an extracellular mediator through binding to 5 highly specific S1P receptors, S1P(1-5). Sphingosine kinase-1 (SK1), one of 2 known sphingosine kinase enzymes responsible for S1P production, appears to be overexpressed in many tumors. Although a role for S1P in angiogenesis and lymphangiogenesis has been established, it is unclear whether S1P secreted from cancer cells has a paracrine function in a tumor environment. Here we investigated whether modulation of cellular SK1 could initiate a paracrine angiogenic and lymphangiogenic switch. We found that SK1 overexpression in HEK cells or its down-regulation in glioma or breast cancer cells modulated extracellular S1P levels accordingly, which in turn increased or decreased both migration and tube formation in cocultured vascular or lymphatic endothelial cells. In contrast, down-regulation of sphingosine kinase 2 in both glioma and breast cancer cells had no appreciable effect on cellular or secreted S1P levels. In addition, vascular endothelial growth factors VEGF and VEGF-C down-regulation in cancer cells appeared insufficient to block the angiogenic and lymphangiogenic switch triggered by these cells. Moreover, S1P initiated endothelial cell sprouting in 3-dimensional collagen matrices, which is representative of a multistep angiogenic process. Our data collectively demonstrate for the first time that SK1 plays an essential role in regulating in vitro paracrine angiogenesis and lymphangiogenesis.

Topics: Breast Neoplasms; Cell Line; Cell Line, Tumor; Coculture Techniques; Endothelial Cells; Female; Gene Expression Regulation; Glioma; Humans; Lymphangiogenesis; Neovascularization, Pathologic; Neovascularization, Physiologic; Paracrine Communication; Phosphotransferases (Alcohol Group Acceptor)

Sphingosine 1-phosphate (S1P), a sphingolipid metabolite that plays an important role in the regulation of cell survival, growth, migration, and angiogenesis, acts both inside the cells and as an extracellular mediator through binding to five G protein-coupled receptors (S1P(1-5)). Sphingosine kinase 1 (SK1), the enzyme responsible for S1P production, is overexpressed in many solid tumors, including gliomas. One common feature of these tumors is the presence of "hypoxic regions," characterized by cells expressing high levels of hypoxia-inducible factors HIF-1alpha and HIF-2alpha, two transcription regulators that modulate the levels of proteins with crucial roles in tumor progression. So far, nothing is known about the role and the regulation of SK1 during tumor-induced hypoxia or about SK1 regulation and HIFs. Here we investigated the role of HIF-1alpha and HIF-2alpha in the regulation of SK1 during hypoxic stress in glioma-derived U87MG cells. We report that hypoxia increases SK1 mRNA levels, protein expression, and enzyme activity, followed by intracellular S1P production and S1P release. Interestingly, knockdown of HIF-2alpha by small interfering RNA abolished the induction of SK1 and the production of extracellular S1P after CoCl(2) treatment, whereas HIF-1alpha small interfering RNA resulted in an increase of HIF-2alpha and of SK1 protein levels. Moreover, using chromatin immunoprecipitation analysis, we demonstrate that HIF-2alpha binds the SK1 promoter. Functionally, we demonstrate that conditioned medium from hypoxia-treated tumor cells results in neoangiogenesis in human umbilical vein endothelial cells in a S1P receptor-dependent manner. These studies provide evidence of a link between S1P production as a potent angiogenic agent and the hypoxic phenotype observed in many tumors.

Topics: Basic Helix-Loop-Helix Transcription Factors; Brain Neoplasms; Disease Progression; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Neoplastic; Glioma; Humans; Hypoxia-Inducible Factor 1; Phosphotransferases (Alcohol Group Acceptor); Promoter Regions, Genetic; RNA, Messenger; RNA, Small Interfering; Transcription, Genetic; Up-Regulation

In C6 glioma cells, the sphingolipid second messenger ceramide potentiates expression of inducible nitric-oxide synthase (iNOS) induced by tumor necrosis factor alpha (TNF-alpha) without affecting GTP cyclohydrolase I (GTPCH), the rate-limiting enzyme in the biosynthesis of 6(R)-5,6,7,8-tetrahydrobiopterin (BH(4)), a cofactor required for iNOS activity. TNF-alpha also stimulates sphingosine kinase, the enzyme that phosphorylates sphingosine to form sphingosine-1-phosphate (SPP), a further metabolite of ceramide. Several clones of C6 cells, expressing widely varying levels of sphingosine kinase, were used to examine the role of SPP in regulation of GTPCH and BH(4) biosynthesis. Overexpression of sphingosine kinase, with concomitant increased endogenous SPP levels, potentiated the effect of TNF-alpha on GTPCH expression and activity and BH(4) biosynthesis. In contrast, enforced expression of sphingosine kinase had no effect on iNOS expression or NO formation. Furthermore, N,N-dimethylsphingosine, a potent sphingosine kinase inhibitor, completely eliminated the increased GTPCH activity and expression induced by TNF-alpha. Surprisingly, we found that, although C6 cells can secrete SPP, which is enhanced by TNF-alpha, treatment of C6 cells with exogenous SPP or dihydro-SPP had no affect on BH(4) biosynthesis. However, both SPP and dihydro-SPP markedly stimulated ERK 1/2 in C6 cells, which express cell surface SPP receptors. Interestingly, although this ERK activation was blocked by PD98059, which also reduced cellular proliferation induced by enforced expression of sphingosine kinase, PD98059 had no effect on GTPCH activity. Collectively, these results suggest that only intracellularly generated SPP plays a role in regulation of GTPCH and BH(4) levels.

Topics: Animals; Base Sequence; Biopterins; DNA Primers; Enzyme Activation; Glioma; GTP Cyclohydrolase; Mice; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor); Tumor Cells, Cultured; Tumor Necrosis Factor-alpha