Tumor stem cells and glioma initiating cells

The tumor stem cell theory supposed that tumor stem cells are the origin of tumor abnormal proliferation, invasion, metastasis, drug resistance and recurrence. As the theory is put forward, it redefines the functions of classic stem cells in tumorigenesis. It is a great event for recent studies on glioma initiating cells as brain tumor stem cells were identified and isolated successfully. A lot of evidence from experiments in vivo and in vitro demonstrates that brain tumor stem cells might play an important role in glioma tumorigenesis. In this review, we discuss the relationship between tumor stem cells and tumorigenesis, and the research on the correlation between brain tumor stem cells and glioma genesis.     

Effects of microRNA-483-3p on human glioma cells

AIM:To investigate the effects of microRNA (miRNA)-483-3p on the growth and migration of human glioma cell line A172 and its potential mechanisms.METHODS:The abundance of miRNA-483-3p in human embryonic kidney 293 cells and different human glioma cell lines (A172,U251 and SHG44) was measured by RT-qPCR.After down-regulation of miRNA-483-3p by transfection of inhibitor in the A172 cells,the cell viability,cell cycle distribution and cell migration were detected by CCK-8 assay,flow cytometry and Transwell assay,respectively.Furthermore,the protein levels of cell cycle-related molecules and epithelial-mesenchymal transition markers were measured by Western blot.Luciferase reporter assay was used to predict and verify the target gene of miRNA-483-3p.RESULTS:miRNA-483-3p was highly expressed in human glioma cells.Knockdown of miRNA-483-3p inhibited A172 cell viability,arrested cell cycle and decreased cell migration rate.Furthermore,the protein levels of cyclin D1,cyclin-dependent kinase 4,phoshorylated retinoblastoma protein,N-cadherin and vimentin were significantly decreased after knockdown of miRNA-483-3p,accompanied with the up-regulation of E-cadherin and β-catenin protein expression.Luciferase reporter assay demonstrated that Smad4 was a potential target gene of miRNA-483-3p.Down-regulation of Smad4 in the A172 cells transfected with miRNA-483-3p inhibitor partially reversed the effect of miRNA-483-3p on cell viability and migration.CONCLUSION:Knockdown of miRNA-483-3p restrains the growth and migration of A172 cells by targeting Smad4.     

Niflumic acid inhibits the proliferation,migration and invasion of glioma U87 cells

AIM To investigate the effect of niflumic acid （NFA） on human glioma U87 cells and to clarify the potential mechanism. METHODS The U87 cells were cultured in vitro and divided into blank control group, and 50, 100 and 200 μmol/L NFA groups. MTT assay was performed to determine the viability of cells in various groups. Migration and invasion abilities were measured by real-time cell analysis （RTCA）. RESULTS The results of MTT assay showed that compared with blank control group, the viability of U87 cells was increased after treatment with NFA for 12 h （P<0.05 or P<0.01）, while the viability was significantly decreased after treatment with NFA for 24 and 48 h （P<0.05 or P<0.01） in a concentration-dependent manner. The results of RTCA showed that compared with control group, the cell migration and invasion abilities were inhibited in 100 and 200 μmol/L NFA groups （P<0.05 or P<0.01） and the inhibitory effects were more obvious in 200 μmol/L NFA group （P<0.01）. CONCLUSION NFA inhibits the viability, migration and invasion of human glioma U87 cells.     

Inhibitory effect of Naja naja venom components on proliferation of human glioma U251 cells

AIM: To study the inhibitory effect of Naja naja venom components on the proliferation of human glioma U251 cells.METHODS: MTT assay was used to compare the inhibitory effect of various kinds of Naja naja venom components on human glioma U251 cells and the efficient components were selected. Flow cytometry was performed to detect apoptotic rate and cell cycle. The morphological changes of human glioma U251 cells were observed under laser scanning confocal microscope and transmission electron microscope.RESULTS: Eleven components of Naja naja venom were tested. The growth-inhibiting effects of them on U251 cells were observed, among which the component KD II-3 showed the inhibitory effect on U251 cells in a dose- and time-dependent manner. After treated with KD II-3 at the concentrations of 1 mg/L, 3.75 mg/L, 7.5 mg/L and 15 mg/L, the apoptotic rates of U251 cells were 13.3%, 17.7%, 20.0% and 22.4%, respectively. U251 cells were blocked in G₀/G₁ phase and the peak of sub-G₁ phase appeared. Under laser scanning confocal microscope, U251 cells showed shrinkage of the cell membrane, chromatin condensation and fragmentation after treated with KD II-3 at the concentration of 7.5 mg/L for 24 h, and karyopyknosis and chromatin condensation in U251 cells were found under transmission electron microscope.CONCLUSION: Component KD II-3 of Naja naja venom inhibits the proliferation of U251 cells and promotes apoptosis.     

miR-21 enhances resistance of glioma cells to carmustine by down-re-gulating PTEN

AIM:To explore the function of miR-21 in human glioma cells resistant to carmustine and to elucidate its related mechanism. METHODS:SWOZ2 cells were transfected with miR-21 mimics(SWOZ2-miR-21mimics) or miRNA mimics negative control(control group) by the method of jetPRIME. The real-time fluorescence quantitative PCR was used to detect and compare the levels of miR-21 expression between BCNU-resistant cell line SWOZ2-BCNU and BCNU-sensitive cell line SWOZ2, or between SWOZ2-miR-21 mimic group and control group. The drug sensitivity of these cells to BCNU was determined by CCK-8 assay. The protein expression of phosphatase and tensin homology deleted on chromosome 10(PTEN), phosphorylated protein kinase B(p-Akt) and P-glycoprotein(P-gp) in these cells were also detected by Western blotting. RESULTS:The expression level of miR-21 was remarkably higher in SWOZ2-BCNU cells than that in SWOZ2 cells. The expression level of miR-21 was significantly higher in SWOZ2-miR-21 mimics group than that in control group. The half-maximal inhibitory concentration(IC₅₀) of BCNU was obviously higher for SWOZ2-BCNU cells than that for SWOZ2 cells. The IC₅₀ of BCNU was markedly higher in SWOZ2-miR-21 mimics group than that in control group. PTEN protein expression was remarkably lower, but p-Akt and P-gp protein expression levels were markedly higher in SWOZ2-BCNU cells than those in SWOZ2 cells. The protein level of PTEN was significantly lower, but the protein levels of p-Akt or P-gp were distinctly higher in SWOZ2-miR-21 mimics group than those in control group. CONCLUSION:miR-21 enhances the resistance of human glioma cells to BCNU by down-regulating the expression of PTEN protein.     

Effects of chemotherapy with angiotensin II-induced hypertension on transplanted intracerebral rat gliomas

AIM:To observe morphological changes in transplanted intracerebral rat gliomas and rat survival time with gliomas under chemotherapy with angiotensin II-induced hypertension. METHODS:C6 glioma cells were cultured, and the effects of carmustine, nimodipine or/and teniposide on gliomas cells was observed. In addition, the brain tumor model was established in Wistar rats by stereotaxic inoculation of C6 glioma cells. The tumor-bearing rats were treated with carmustine, nimodipine lisplatin or/and teniposide during angiotensin II-induced hypertension, the pathological changes in gliomas was also examined. RESULTS:In vitro experiments showed chemotherapy resulted in morphologic changes in glioma cells, including cell enlargement, degeneration. In vivo experiments, the survival time of tumor-bearing rats was longer, the voume of gliomas was smaller in chemotherapy with hypertension group than those in chemotherapy alone, and pathological examination showed necrosis in the gliomas. CONCLUSION:Chemotherapy with angiotensin II-induced hypertension has a better inhibitory effect on rat intracerebral gliomas than chemotherapy alone.     

Changes of aquaporin expression in blood-brain barrier induced by glioma cells

AIM:To investigate the effects of glioma cells on aquaporin expression in blood-brain barrier and their importance in pathophysiology.METHODS:A blood-brain barrier model was established by coculture of ECV304 and astrocytesin vitro. HPLC was used to determine the change of water transport ofin vitroblood-brain barrier model after the influence of glioma cells. The expression levels of AQP1 and AQP4 were analyzed by semiquatitative RT-PCR.RESULTS:Glioma cells decreased expression level of AQP4 of astrocytes and induced abnormal expression of aquaporin-1 in endothelial cell line. The water transport ofin vitroblood-brain barrier model from luminal side to abluminal side was increased after coculture with glioma cells.CONCLUSION:The vasogenic brain edema induced by glioma cells may not be the result of hyperpermeability of blood-brain barrier to macromolecules in plasma. The changes of aquaporin expression may be the molecular basis of brain edema induced by glioma cells.     

Effect of ginsenoside Rg1 on the amyloid protein precursor and neprilysin expression induced by lipopolysaccharide in C6 cell line

AIM: This study was designed to investigate the effect of ginsenoside Rg1 on the amyloid β-protein precursor (APP) and neprilysin (NEP)expression induced by lipopolysaccharide (LPS) in C6 cell line in order to discover effectual Alzheimer's disease (AD)-treated drugs. METHODS: MTT colorimetric analysis was used to measure the survival rate of C6 cultured with ginsenoside Rg1 at different concentrations (2.5, 5, 10 and 20 μmol·L^-1) and LPS (100 mg·L^-1). The expression of APP and NEP mRNA was measured by RT-PCR. RESULTS: LPS decreased the survival rate of C6, furthermore, the increase in APP expression and the decrease in NEP expression were observed. On the other hand, the above alteration induced by LPS was reversed by ginsenoside Rg1. CONCLUSION: This study demonstrates that LPS can cause cell damage, the increase in APP expression and the decrease in NEP expression. Ginsenoside Rg1 can exert a neuroprotective action, protect C6 cells against LPS-induced injury via inhibiting APP expression and increasing NEP expression.     

Effects of chemotherapy on free radicals in the rat glioma

AIM: To observe the role of free radicals in the inhibitory effect of chemotherapy on glioma cells. METHODS: C6 glioma cells were cultured in vitro, and treated with carmustine (B), teniposide (V), or/and nimodipine (N). Furthermore, the glioma-bearing rats were treated with B plus N, B+V+lisplatin (D)+N, or B+V+D+N+angiotensin Ⅱ. The MDA content and superoxide dismutase (SOD) activity in the culture supernatant and cortical brain tissue were assayed. RESULTS: B, V and N significantly decreased MDA content and SOD activity in the supernatant of glioma cell culture and C6 glioma cells. Chemotherapy reduced MDA content and increased SOD activity in the cortical brain tissue of tumor-bearing rats, with highest efficiency in B+V+D+N+angiotensin Ⅱ group. The survival time of tumor-bearing rats in B+V+D+N+angiotensin Ⅱ group was longer than that in other chemotherapy group. CONCLUSION: The antitumor effects of combined chemotherapy may be involved in the free radical metabolism.     

Notch1 regulates stemness and chemotherapeutic sensitivity of human glioma U251 cells

AIM: To investigate whether Notch1 changes stemness and chemotherapeutic sensitivity in human glioma U251 cells. METHODS: The lentiviral vectors, which expressed Notch1-shRNA or Notch1 intracellular domain (NICD), were transfected into U251 cells. Western blot and immunofluorescence staining were applied to monitor the validity of the cells, down-regulation of Notch1 expression or over-expression of NICD. The proportion of CD133⁺ cells was analyzed by flow cytometry. The expression of nestin and GFAP was identified by immunofluorescence staining. The formation rate of tumor cell spheres and the implanted tumor growth in SCID mice were observed. MTT assay was performed to evaluate the chemotherapeutic sensitivity to VM-26 and BCNU of the cells with different treatments. RESULTS: Stemness was significantly enhanced in the cells over-expressing NICD. For example, the proportion of CD133⁺ cells was increased, the expression of nestin was up-regulated, the expression of GFAP was down-regulated, and the formation rate of tumor cell spheres and implanted tumor growth were increased. The chemotherapeutic sensitivity to VM-26 and BCNU of the cells was decreased. In the cells with Notch1 gene down-regulation by RNAi, the stemness was inhibited and chemotherapeutic sensitivity was increased. CONCLUSION: Notch1, which leads to the change of stemness and chemotherapeutic sensitivity in human glioma U251 cells, is likely to be a potential molecular target for treatment of glioma.