The association between Salt-inducible kinase 2 (SIK2) and gamma isoform of the regulatory subunit B55 of PP2A (B55gamma) contributes to the survival of glioma cells under glucose depletion through inhibiting the phosphorylation of S6K.

BACKGROUND: PPP2R2C encodes a gamma isoform of the regulatory subunit B55 subfamily consisting PP2A heterotrimeric with A and C subunits. Currently, the precise functions of B55gamma in cancer are still under investigating. In this project, we reported a novel function of B55gamma in the regulation of glucose metabolism in Glioma cells. METHODS: Western blot and immunoprecipitation were performed to determine protein expression and interaction. Cell viability was measured by Typan Blue staining and direct cell counting using hematocytometer. siRNA technology was used to down regulate protein expression. RESULTS: Glucose uptake and lactate product were suppressed by overexpression of B55gamma in Glioma cells. In addition, cancer cells with larger amount of B55gamma showed higher survival advantages in response to glucose starvation through the dephosphorylation of S6K. From proteomic analysis, we found B55gamma binds with and up regulates SIK2 through the stabilization of SIK2 protein which is required for the B55gamma-mediated suppression of S6K pathway. Knocking down of SIK2 in B55gamma over expressing cells recovered the phosphorylation of S6K. CONCLUSION: In summary, our project will provide novel insight into the design and development of therapeutic strategies to target the B55gamma-mediated glucose metabolism for the treatment of human brain tumor patients.

Decreased miR-106a inhibits glioma cell glucose uptake and proliferation by targeting SLC2A3 in GBM.

BACKGROUND: MiR-106a is frequently down-regulated in various types of human cancer. However the underlying mechanism of miR-106a involved in glioma remains elusive. METHODS: The association of miR-106a with glioma grade and patient survival was analyzed. The biological function and target of miR-106a were determined by bioinformatic analysis and cell experiments (Western blot, luciferase reporter, cell cycle, ntracellular ATP production and glucose uptake assay). Finally, rescue expression of its target SLC2A3 was used to test the role of SLC2A3 in miR-106a-mediated cell glycolysis and proliferation. RESULTS: Here we showed that miR-106a was a tumor suppressor miRNA was involved in GBM cell glucose uptake and proliferation. Decreased miR-106a in GBM tissues and conferred a poor survival of GBM patients. SLC2A3 was identified as a core target of miR-106a in GBM cells. Inhibition of SLC2A3 by miR-106a attenuated cell proliferation and inhibited glucose uptake. In addition, for each biological process we identified ontology-associated transcripts that significantly correlated with SLC2A3 expression. Finally, the expression of SLC2A3 largely abrogated miR-106a-mediated cell proliferation and glucose uptake in GBM cells. CONCLUSIONS: Taken together, miR-106a and SLC2A3 could be potential therapeutic approaches for GBM.

Unusual posterior fossa mass caused by Lhermitte-Duclos disease with no symptoms in adults.

We present an asymptomatic case of Lhermitte-Duclos disease (LDD) in a 40-year-old woman and discuss the diagnosis, management and prognosis of this rare disease. Surgical intervention is strongly recommended as an initial therapy strategy even in asymptomatic adult patients. Conservative strategies could be chosen if the mass involves the brainstem or is accidentally found in the elderly.

Temozolomide/PLGA microparticles: a new protocol for treatment of glioma in rats.

Implantable and poly (d,l-lactide-co-glycolide) (PLGA) microparticles were developed to deliver temozolomide (TM) continuously in interstitial chemotherapy for glioma. The therapeutic effect of temozolomide/PLGA was evaluated in a rat C6 glioma model. C6 cells were implanted orthotopically into 100 rat brains in 5 groups (n=20 each): sham operation group, control group, local delivery of blank PLGA microspheres group, oral TM group, and local delivery of TM/PLGA group. Rats in oral TM group were orally administered temozolomide, and rats in TM/PLGA group were locally implanted with TM/PLGA microspheres. Ten rats were selected randomly from each group for observing the survival time, and the other 10 rats were killed on POD 14 to measure proliferation activity and apoptosis of the gliomas. Head MRI examination was performed before the rats were killed. The median survival time of sham operation group, control group, blank PLGA microspheres group, oral TM group, and TM/PLGA group was 19.5, 20, 19, 27, and 46.5 days, respectively. MRI demonstrated that the tumor volume was reduced in oral TM group and interstitial TM/PLGA group. PCNA-positive cell staining showed that proliferation activity of tumor cells treated with interstitial TM/PLGA therapy significantly decreased when compared with that of tumor cells treated with oral TM therapy. The apoptosis of C6 cells in interstitial TM/PLGA group significantly increased when compared with that in oral TM group. Interstitial TM/PLGA was effective in treating intracranial C6 rat gliomas and could prove to be a potential chemotherapy agent for human malignant gliomas.

γ-secretase inhibitor up-regulates vascular endothelial growth factor receptor-2 and endothelial nitric oxide synthase.

Although previous studies have shown that γ-secretase inhibitors significantly suppress tumor growth via anti-angiogenesis, the mechanism involved in the regulation of tumor angiogenesis by γ-secretase inhibitors has not been clearly understood. The objective of this study was to investigate the regulation of vascular endothelial growth factor receptor (VEGFR) and endothelial nitric oxide synthase (eNOS) by a γ-secretase inhibitor in the H5V mouse microvascular endothelial cell line. H5V cells were cultured with different concentrations of the γ-secretase inhibitor DAPT for 48 h and with 100 µmol/l DAPT at different incubation times. Protein and mRNA expression of VEGFR-1, VEGFR-2, VEGFR-3 and eNOS was measured by Western blotting and real-time PCR, respectively. The VEGFR-2 kinase inhibitor was used to assess the role of VEGFR-2 in eNOS regulation. We found that the γ-secretase inhibitor DAPT increased protein and mRNA expression of VEGFR-2 and eNOS, but decreased VEGFR-1 expression and had no significant effect on VEGFR-3. Up-regulation of eNOS was blocked by the VEGFR-2 kinase inhibitor. In conclusion, the γ-secretase inhibitor enhances VEGFR-2 and eNOS expression, and the up-regulation of eNOS is dependent on an increase in VEGFR-2. Thus, we suggest that administration of the γ-secretase inhibitor be combined with disruption of eNOS or interruption of VEGF signaling, which may improve the anti-angiogenic efficacy in tumor treatments.

Temozolomide/PLGA microparticles plus vatalanib inhibits tumor growth and angiogenesis in an orthotopic glioma model.

Temozolomide (TM) has anti-tumor activity in patients with malignant glioma. Implantable poly (D,L-lactide-co-glycolide) (PLGA) microparticles of TM (TM-MS) have been developed, enhancing the cytotoxicity of TM to Glioma C6 cells. Vatalanib, as anti-angiogenic agent, has also shown anti-tumor activity with malignant gliomas. We examined the combined effects of TM-MS and vatalanib in a rat orthotopic glioma model and found TM-MS offered a greater tumor inhibition than TM, and combination treatment with both of them improved the survival time versus single agent therapy. The combination treatment also demonstrated an inhibition to rat glioma tumors, a significant decrease in cell proliferation, an increase in apoptosis, and a lower microvessel density within the glioma tumors. The results suggest that TM-MS can more effectively inhibit tumor than TM, and combination treatment with TM-MS and vatalanib inhibits tumor growth and angiogenesis and may prove to be a promising therapy for malignant gliomas.