Upregulation of SATB1 is associated with the development and progression of glioma

BACKGROUND

Special AT-rich sequence-binding protein-1 (SATB1) has been reported to be expressed in several human cancers and may have malignant potential. This study was aimed at investigating the expression and potential role of SATB1 in human glioma.

METHOD

The relationship between SATB1 expression, clinicopathological parameters, Ki67 expression and MGMT promoter methylation status was evaluated, and the prognostic value of SATB1 expression in patients with gliomas was analyzed. SATB1-specific shRNA sequences were synthesized, and U251 cells were transfected with SATB1 RNAi plasmids. Expression of SATB1 mRNA and protein was investigated by RT-PCR and immunofluoresence staining and western blotting. The expression of c-Met, SLC22A18, caspase-3 and bcl-2 protein was determined by western blotting. U251 cell growth and adherence was detected by methyl thiazole tetrazolium assay. The apoptosis of U251 cells was examined with a flow cytometer. The adherence, invasion, and in vitro angiogenesis assays of U251 cells were done. The growth and angiogenesis of SATB1 low expressing U251 cells was measured in an in vivo xenograft model.

RESULTS

Of 70 tumors, 44 (62.9%) were positive for SATB1 expression. SATB1 expression was significantly associated with a high histological grade and with poor survival in univariate and multivariate analyses. SATB1 expression was also positively correlated with Ki67 expression but negatively with MGMT promoter methylation in glioma tissues. SATB1 shRNA expression vectors could efficiently induce the expression of SLC22A18 protein, increase the caspase-3 protein, inhibit the expression of SATB1, c-Met and bcl-2 protein, the growth, invasion, metastasis and angiogenesis of U251 cells, and induce apoptosis in vitro. Furthermore, the tumor growth of U251 cells expressing SATB1 shRNA were inhibited in vivo, and immunohistochemical analyses of tumor sections revealed a decreased vessel density in the animals where shRNA against SATB1 were expressed.

CONCLUSIONS

SATB1 may have an important role as a positive regulator of glioma development and progression, and that SATB1 might be a useful molecular marker for predicting the prognosis of glioma.

Hydroxyapatite nanoparticles inhibit the growth of human glioma cells in vitro and in vivo

Hydroxyapatite nanoparticles (nano-HAPs) have been reported to exhibit antitumor effects on various human cancers, but the effects of nano-HAPs on human glioma cells remain unclear. The aim of this study was to explore the inhibitory effect of nano-HAPs on the growth of human glioma U251 and SHG44 cells in vitro and in vivo. Nano-HAPs could inhibit the growth of U251 and SHG44 cells in a dose- and time-dependent manner, according to methyl thiazoletetrazolium assay and flow cytometry. Treated with 120 mg/L and 240 mg/L nano-HAPs for 48 hours, typical apoptotic morphological changes were noted under Hoechst staining and transmission electron microscopy. The tumor growth of cells was inhibited after the injection in vivo, and the related side effects significantly decreased in the nano-HAP-and-drug combination group. Because of the function of nano-HAPs, the expression of c-Met, SATB1, Ki-67, and bcl-2 protein decreased, and the expression of SLC22A18 and caspase-3 protein decreased noticeably. The findings indicate that nano-HAPs have an evident inhibitory action and induce apoptosis of human glioma cells in vitro and in vivo. In a drug combination, they can significantly reduce the adverse reaction related to the chemotherapeutic drug 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU).

Correlation of low SLC22A18 expression with poor prognosis in patients with glioma

We investigated the expression of the putative tumor suppressor SLC22A18 to evaluate it as a prognostic marker in glioma patients. Immunohistochemical and Western blot analyses of clinical tissue samples obtained from 120 patients with glioma were performed. Low expression of SLC22A18 was observed in 71.7% of patients. Loss of SLC22A18 expression in glioma was significantly related to pathological grade (p = 0.003). High pathological grade (World Health Organization III-IV) was correlated with negative (low or absent) expression of SLC22A18, which was correlated with a significantly shorter overall patient survival than in those with positive (high) expression (p = 0.007). Multivariate Cox regression analysis indicated that SLC22A18 expression level is an independent survival prognostic factor for patients with glioma (p = 0.011). Western blotting analysis confirmed decreased expression of SLC22A18 in glioma tissues compared with adjacent brain tissues. This study suggests that SLC22A18 functions as a tumor suppressor in glioma and represents a candidate biomarker for long-term survival in this disease.

Promoter methylation and downregulation of SLC22A18 are associated with the development and progression of human glioma

BACKGROUND

Downregulation of the putative tumor suppressor gene SLC22A18 has been reported in a number of human cancers. The aim of this study was to investigate the relationship between SLC22A18 downregulation, promoter methylation and the development and progression of human glioma.

METHOD

SLC22A18 expression and promoter methylation was examined in human gliomas and the adjacent normal tissues. U251 glioma cells stably overexpressing SLC22A18 were generated to investigate the effect of SLC22A18 on cell growth and adherence in vitro using the methyl thiazole tetrazolium assay. Apoptosis was quantified using flow cytometry and the growth of SLC22A18 overexpressing U251 cells was measured in an in vivo xenograft model.

RESULTS

SLC22A18 protein expression is significantly decreased in human gliomas compared to the adjacent normal brain tissues. SLC22A18 protein expression is significantly lower in gliomas which recurred within six months after surgery than gliomas which did not recur within six months. SLC22A18 promoter methylation was detected in 50% of the gliomas, but not in the adjacent normal tissues of any patient. SLC22A18 expression was significantly decreased in gliomas with SLC22A18 promoter methylation, compared to gliomas without methylation. The SLC22A18 promoter is methylated in U251 cells and treatment with the demethylating agent 5-aza-2-deoxycytidine increased SLC22A18 expression and reduced cell proliferation. Stable overexpression of SLC22A18 inhibited growth and adherence, induced apoptosis in vitro and reduced in vivo tumor growth of U251 cells.

CONCLUSION

SLC22A18 downregulation via promoter methylation is associated with the development and progression of glioma, suggesting that SLC22A18 is an important tumor suppressor in glioma.

Stabilization of hepatocyte growth factor mRNA by hypoxia-inducible factor 1

Hypoxia regulates expression of hepatocyte growth factor (HGF) by increasing its transcription and by stabilizing its mRNA. Despite the pivotal role of hypoxia-inducible factor 1 (HIF-1) in transcriptional activation of hypoxia-responsive genes, it is not known whether HIF-1 mediates hypoxia-induced stabilization of HGF mRNA. We constructed adenoviral vectors expressing either the wild-type HIF-1alpha (Ad2/HIF-1alpha/FL), a constitutively stable hybrid form of HIF-1alpha (Ad2/HIF-1alpha/VP16), or no transgene (Ad2/CMVEV). In rat glioma (C6) cells, human glioma (U251) cells human cardiac, vascular smooth muscle, and endothelial cells, infection with Ad2/HIF-1alpha/VP16 or Ad2/HIF-1alpha/FL increased HGF expression at both the mRNA and protein levels. Under normoxic conditions, the half-life of HGF mRNA was 43 min in C6 and U251 cells. Hypoxia and Ad2/HIF-1alpha/VP16 increased the half-life of HGF mRNA to 3.2 and 2.8 h, respectively, while Ad2/CMVEV had no effect. These studies are the first to demonstrate that overexpression of HIF-1alpha increases HGF mRNA stability. Our results also suggest that stabilization of HGF mRNA by hypoxia is mediated, at least in part, by HIF-1.

c-Met-targeted RNA interference inhibits growth and metastasis of glioma U251 cells in vitro

Angiogenesis plays an essential role in tumor growth and metastasis and is a promising target for cancer therapy. c-Met, a receptor tyrosine kinase, and its ligand, hepatocyte growth factor (HGF), are critical in cellular proliferation, motility, invasion, and angiogenesis. The present study was designed to determine the role of c-Met in growth and metastasis of glioma U251 cells using RNA interference (RNAi) technology in vitro. We constructed three kinds of shRNA expression vectors aiming at the c-Met gene, then transfected them into glioma U251 cells by lipofectamine(TM) 2000. The level of c-Met mRNA was investigated by real-time polymerse chain reaction (RT-PCR). The protein expression of c-Met was observed by immunofluoresence staining and western blotting. U251 cell growth and adherence was detected by methyl thiazole tetrazolium assay. The apoptosis of U251 cells was examined with a flow cytometer. The adherence, invasion, and in vitro angiogenesis assays of U251 cells were done. We got three kinds of c-Met specific shRNA expression vectors which could efficiently inhibit the growth and metastasis of U251 cells and the expression of c-Met in U251 cells. RT-PCR, immunofluoresence staining and western blotting showed that inhibition rate for c-Met expression was up to 90%, 79% and 85%, respectively. The expression of c-Met can be inhibited by RNA interference in U251 cells, which can inhibit the growth and metastasis of U251 cell and induce cell apoptosis. These results indicate that RNAi of c-Met can be an effective antiangiogenic strategy for glioma.

Radiation-enhanced hepatocyte growth factor secretion in malignant glioma cell lines

BACKGROUND

Postoperative radiotherapy is the standard treatment for patients with a malignant glioma. However, a malignant glioma is radioresistant and almost always recurs, even after a high dose of radiation. A malignant glioma is characterized by its proliferation, invasion and neoangiogenesis, which can be attributed to the high levels of HGF. The scope of this study is to investigate HGF secretion by malignant glioma cells with different radiosensitivity after irradiation.

METHODS

Three human malignant glioma cell lines (U251, U251-NG2, and BT325) were irradiated with single doses of 0, 5, 10, and 20 grays of gamma-rays from a (137)Cs source. Hepatocyte growth factor levels in medium were measured by ELISA at 24, 48, and 72 hours after radiation. Cell survival was measured by the proliferation-based assay (XTT assay) 7 days after irradiation.

RESULTS

After a single dose radiation, the HGF levels showed a dose-dependent increase in U251, U251-NG2, and BT325 glioma cells. Both baseline and radiation-enhanced HGF levels were about 10-fold higher in BT325 compared to U251 and U251-NG2 cells. In addition, in the XTT assay, the BT325 was more radioresistant than both U251 and U251-NG2 cell lines (dose modifying factor = 1.5 and 1.6, respectively).

CONCLUSION

Irradiation-enhanced HGF secretion in all 3 tested glioma cell lines (up to 7 times basal levels). It is tempting to associate the radiation-enhanced HGF secretion with an increased angiogenic potential of the tumor, which may be a factor in radioresistance.

In vitro and in vivo radiosensitization induced by hydroxyapatite nanoparticles

BACKGROUND

Previous study showed that hydroxyapatite nanoparticles (nano-HAPs) inhibited glioma growth in vitro and in vivo; and in a drug combination, they could reduce adverse reactions. We investigated the possible enhancement of radiosensitivity induced by nano-HAPs.

METHODS

In vitro radiosensitization of nano-HAPs was measured using a clonogenic survival assay in human glioblastoma U251 and breast tumor brain metastatic tumor MDA-MB-231BR cells. DNA damage and repair were measured using γH2AX foci, and mitotic catastrophe was determined by immunostaining. The effect of nano-HAPs on in vivo tumor radiosensitivity was investigated in a subcutaneous and an orthotopic model.

RESULTS

Nano-HAPs enhanced each cell line's radiosensitivity when the exposure was 1 h before irradiation, and they had no significant effect on irradiation-induced apoptosis or on the activation of the G2 cell cycle checkpoint. The number of γH2AX foci per cell was significantly large at 24 h after the combination modality of nano-HAPs + irradiation compared with single treatments. Mitotic catastrophe was also significantly increased at an interval of 72 h in tumor cells receiving the combined modality compared with the individual treatments. In a subcutaneous model, nano-HAPs caused a larger than additive increase in tumor growth delay. In an orthotopic model, nano-HAPs significantly reduced tumor growth and extended the prolongation of survival induced by irradiation.

CONCLUSIONS

These results show that nano-HAPs can enhance the radiosensitivity of tumor cells in vitro and in vivo through the inhibition of DNA repair, resulting in an increase in mitotic catastrophe.

In vitro and in vivo potentiating the cytotoxic effect of radiation on human U251 gliomas by the c-Met antisense oligodeoxynucleotides

C-Met, a receptor tyrosine kinase, and its ligand, hepatocyte growth factor (HGF), are critical in cellular proliferation, motility, and invasion, and are known to be overexpressed in gliomas, which are related to the repair of damaged DNA. In this study, we investigated both in vitro and in vivo whether inhibition of the c-Met gene by antisense oligonucleotides (ODNs) enhances the cytotoxic effect of radiation on human U251 gliomas. A volume of 100 nM of c-Met antisense ODNs inhibited the level of mRNA by more than 95% and reduced the protein expression by about 70%. Treatment of human U251 glioma cells with 100 nM of c-Met antisense ODNs significantly enhanced the radiation-induced cell kill compared to control cells, and cells treated with nonsense ODNs. When the glioma cells were implanted in the cisterna magna of nude mice followed by treatment with c-Met antisense ODNs, the survival time of the nude mice was markedly prolonged compared to that of the untreated group (P < 0.001, logrank test). In addition, the combination of antisense ODNs and irradiation extended the survival time of the glioma-bearing nude mice much longer than could be achieved with radiation alone (P < 0.0001, logrank test). These results suggest that inhibition of c-Met can be expected to serve as a novel potentiator for radiation therapy in human U251 gliomas.

Giant intradiploic epidermoid cyst of the occipital bone

Epidermoid cysts are uncommon, benign and slow-growing lesions. They often reach an enormous size without producing neurologic symptoms. We describe a 35-year-old female who had a giant intradiploic epidermoid cyst of the occipital bone. She underwent posterior cranial fossa tumor resection. Pathology confirmed epidermoid cyst. There was no recurrence at 13-month follow-up. Total removal of these cysts and repeated washing of the cavity with 0.9% saline may prevent recurrence and aseptic meningitis.

C-Met antisense oligodeoxynucleotide inhibits growth of glioma cells

BACKGROUND

C-Met, a receptor tyrosine kinase, and its ligand, hepatocyte growth factor, are critical in cellular proliferation, motility, and invasion and are known to be overexpressed in gliomas. The aim of our study was therefore to investigate the effect of transfected caroboxyfluorescein-5-succimidyl ester (FAM)-labeled c-Met antisense oligonucleotide (ASODN) on growth of glioma cells.

METHODS

Conjugated FAM-labeled c-Met ASODN was encapsulated by LIPOFECTAMINE PLUS Reagent and then added into the human glioma cell line U251. Cultured cells were divided into 5 groups: control group, 500 nmol/L nonsense oligonucleotide (NSODN) group, 250 nmol/L ASODN group, 500 nmol/L ASODN group, and 750 nmol/L ASODN group. The intracellular distribution of c-Met ASODN was observed with fluorescence microscopy; cell growth was detected by methyl thiazole tetrazolium assay. The apoptosis of U251 cells was also examined with a flow cytometer. Semiquantitative reverse transcriptase polymerase chain reaction and Western blot examinations were carried for expression of c-Met messenger RNA (mRNA) and protein.

RESULTS

The blue fluorescence was seen in the cytoplast and nuclei of cells of FAM-labeled c-Met ASODN groups with fluorescence microscopy after the cells were treated with FAM-labeled c-Met ASODN-LIPOFECTAMINE PLUS Reagent complex for 3 hours. Antisense (AS) oligonucleotide caused a statistically significant reduction of cell viability (P < .05), whereas NSODN had no such changes. The cell growth was also significantly inhibited by ASODN (P < .05). After transfection, 250, 500, and 750 nmol/L ASODN induced significant apoptotic response, about 4.67% +/- 2.86%, 8.65% +/- 3.18%, and 12.76% +/- 3.15% for 24 hours (P < .05) and 7.79% +/- 1.92%, 11.43% +/- 1.54%, and 15.78% +/- 1.86% for 48 hours (P < .01), respectively. However, 500 nmol/L NSODN did not induce any significant apoptotic response until 48 hours after transfection (P > .05). A significant loss of c-Met mRNA was presented in ASODN-treated cells, and this was not seen in treatment with NSODN. Protein level was significantly decreased 48 hours after c-Met ASODN transfected.

CONCLUSIONS

Antisense oligonucleotide targeting c-Met can be identified as a most potent AS compound, which can inhibit cell growth and induce cell apoptosis. This provides evidence that c-Met plays a role in tumor progression of glioma by acting as an oncogene and suggests that c-Met ASODN may provide a novel approach to therapy for human glioma.

Correlation between SATB1 and Bcl-2 expression in human glioblastoma multiforme

Special AT-rich sequence-binding protein-1 (SATB1) has been reported to be overexpressed in numerous human tumors. The aim of the present study was to determine the correlation and clinical significance between the expression of SATB1 and B-cell lymphoma 2 (Bcl-2) in human glioblastoma multiforme (GBM). Samples from 70 patients with GBMs were analyzed and 10 normal brain tissues were used as the control group. In situ hybridization was used to detect SATB1 mRNA expression and immunohistochemistry was used to detect Bcl-2 and proliferating cell nuclear antigen (PCNA) protein expression. Apoptosis was detected with flow cytometry. The SATB1 mRNA and Bcl-2 protein levels were found to be significantly higher in GBM tissues than in normal brain and their levels were associated with patient survival, but not associated with patient gender, age and tumor size and site. A positive correlation was observed between SATB1 mRNA and Bcl-2 protein and between SATB1 mRNA and PCNA. A negative correlation was observed between SATB1 mRNA and apoptosis and between Bcl-2 and apoptosis. A positive correlation existed between Bcl-2 and PCNA. Patients with GBM identified as SATB1 mRNA (+) and Bcl-2 (+) were associated with a poor prognosis. Therefore, assessment of SATB1 and Bcl-2 co-expression may provide important information for the diagnosis, therapy and prognosis of GBM.

Relationship between SATB1 expression and prognosis in astrocytoma

Special AT-rich-sequence-binding protein 1 (SATB1), a new type of gene regulator, has been reported to be expressed in various human cancers and may be associated with malignancy. The aim of this study was to investigate the expression of SATB1 in astrocytoma and to determine its prognostic value for the overall survival of patients with astrocytoma. The expression of SATB1 protein and messenger RNA (mRNA) in human astrocytoma specimens was examined using immunohistochemistry and semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). The relationship between SATB1 expression and O-6-methylguanine-DNA methyltransferase (MGMT) promoter methylation status was also investigated. Spearman's correlation coefficient was used to describe the association between SATB1 expression and the clinical parameters of astrocytoma patients. SATB1 protein and mRNA were expressed at significant levels in astrocytoma specimens. SATB1 expression was positively correlated with astrocytoma pathological grade but negatively correlated with the life span of astrocytoma patients. SATB1 expression was also significantly lower in astrocytoma specimens with MGMT promoter methylation than in those without MGMT promoter methylation. Our findings suggest that SATB1 may have an important role as a positive regulator of astrocytoma development and progression and that SATB1 might be a useful molecular marker for predicting the prognosis of patients with astrocytoma and could be a novel target for treating astrocytoma.

Induction of proline-rich tyrosine kinase 2 activation-mediated C6 glioma cell invasion after anti-vascular endothelial growth factor therapy

BACKGROUND

Anti-angiogenic therapy inhibits tumor growth and is considered as a potential clinical therapy for malignant glioma. However, inevitable recurrences and unexpected tumor resistance, particularly increased invasion ability of glioma cell, were observed after anti-angiogenic treatment. The underlying mechanism remains undetermined. Focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2 (Pyk2) are closely associated with cell migration; therefore, we investigated the possible role of these kinases in rat C6 glioma cell invasion induced by bevacizumab, a recombinant monoclonal antibody against vascular endothelial growth factor (VEGF).

METHODS

The effects of bevacizumab on migration and invasion of C6 glioma cells were investigated in vitro and in vivo. The cells proliferation, migration, and invasion were determined by MTT assay, wound healing, and transwell assay, respectively. Invasive potential of glioma cells in vivo was assessed by counting vimentin-positive cells crossing the solid tumor rim by immunohistochemical staining. The total and phosphorylated protein levels of FAK and Pyk2 were detected by Western blotting.

RESULTS

Bevacizumab exposure increased migration and invasion of cultured C6 cells in a concentration-dependent manner. In addition, the continuous bevacizumab treatment also promoted tumor invasion in rat C6 intracranial glioma models. Bevacizumab treatment enhanced Pyk2 phosphorylation at Tyr402, but no effect on FAK phosphorylation at Tyr397 both in vitro and in vivo. Knockdown of Pyk2 by siRNA or inhibition of Pyk2 phosphorylation by Src kinase specific inhibitor PP1 partially inhibited bevacizumab-induced cell invasion in cultured C6 glioma cells. Furthermore, the combined administration of bevacizumab and PP1 significantly suppressed glioma cell invasion into surrounding brain tissues compared to bevacizumab treatment alone in experimental rats.

CONCLUSIONS

These results suggest that anti-VEGF treatment promotes glioma cell invasion via activation of Pyk2. Inhibition of Pyk2 phosphorylation might be a potential target to ameliorate the therapeutic efficiency of anti-VEGF treatment.

Silencing SATB1 overcomes temozolomide resistance by downregulating MGMT expression and upregulating SLC22A18 expression in human glioblastoma cells

Glioblastoma multiforme (GBM) is the most common malignant tumor of the central nervous system and has a very poor prognosis. Currently, patients were treated by resection followed by radiotherapy plus concurrent temozolomide (TMZ) chemotherapy. However, many patients are resistant to TMZ-induced DNA damage because of upregulated expression of the DNA repair enzyme O6-methylguanine-DNA methyltransferase (MGMT). In this study, upregulation of SATB1 and MGMT, and downregulation of SLC22A18 resulted in acquisition of TMZ resistance in GBM U87 cells. Inactivation of special AT-rich sequence-binding protein 1 (SATB1) using short hairpin RNA (shRNA) downregulated MGMT expression and upregulated solute carrier family 22 member 18 (SLC22A18) expression in GBM cells. This suggested SATB1-mediated posttranscriptional regulation of the MGMT and SLC22A18 protein levels. Immunohistochemical analysis of malignant glioma specimens demonstrated a significant positive correlation between the levels of MGMT and SATB1, and a negative correlation between the levels of SLC22A18 and SATB1. Importantly, in recurrent, compared with the primary, lesions in 15 paired identical tumors, the SATB1 and MGMT protein levels were increased and the SLC22A18 levels were decreased. Finally, in TMZ-resistant GBM, SATB1 knockdown enhanced TMZ efficacy. Consequently, SATB1 inhibition might be a promising strategy combined with TMZ chemotherapy to treat TMZ-resistant GBM.

Elevated expression of solute carrier family 22 member 18 increases the sensitivity of U251 glioma cells to BCNU

Previous studies showed that solute carrier family 22 member 18 (SLC22A18) is involved in tumorigenesis. The aim of this study was to examine the role of SLC22A18 in glioma cells. Glioma U251 cells were transfected with the human SLC22A18 gene. Transfection of the empty vector pcDNA3.1 was used as a negative control. Sensitivity to BCNU was measured by Annexin V staining. The expression of caspase-3 and bcl-2 was determined by immunohistochemistry. The transfection was confirmed by PCR, RT-PCR and Western blotting. Augmented apoptotic cell death was observed in the SLC22A18-transfected cells, compared to the non-transfected cells or cells with the empty vector. Caspase-3 expression increased in U251-SLC22A18 cells, whereas the bcl-2 expression decreased. These results indicated that SLC22A18 has a pro-apoptotic function in glioma cells.

Inhibition of human glioma U251 cells growth in vitro and in vivo by hydroxyapatite nanoparticle-assisted delivery of short hairpin RNAs against SATB1

Special AT-rich sequence-binding protein-1 (SATB1) has been reported to be over-expressed in many human tumors and knockdown of SATB1 can inhibit tumor growth. The present study was designed to determine the role of SATB1 in the growth of human glioma U251 cells using the plasmid-based SATB1 short hairpin RNA (shRNA) delivered by hydroxyapatite nanoparticles in vitro and in vivo. The in vitro growth, invasion and angiogenesis assays of human glioma U251 cells were done. U251 cells tumor blocks were transplanted into the nude mice. CaCl2-modified hydroxyapatite nanoparticles carrying shRNA-SATB1 plasmids were injected into the tumors. The apoptosis of the tumor U251 cells was examined with TUNEL assay and flow cytometer (FCM). The tumor growth and immunohistochemistry were measured. The expression level of SATB1 mRNA was investigated by RT-PCR. The expression levels of SATB1, Cyclin D1, MMP-2, VEGF, Bax and Caspase-9 protein were determined by western blot analysis. The results showed that hydroxyapatite nanoparticles-delivered shRNA-SATB1 could significantly inhibit the growth, invasion and angiogenesis of U251 cells in vitro and the growth of U251 cells in vivo. FCM results showed that Nano HAP-shRNA-SATB1-induced apoptosis (up to 67.8 %). SATB1 expression was strongly down-regulated in the tumor U251 cells. Cyclin D1, MMP-2 and VEGF were also down-regulated in the tumor tissues that also displayed significant increased in Bax expression and Caspase-9 activity. These results show that Nano HAP-shRNA-SATB1 can inhibit the growth of human glioma U251 cells in vitro and in vivo, and hydroxyapatite nanoparticles can be used for the in vitro and in vivo delivery of plasmid-based shRNAs into U251 cells.

Hepatocyte growth factor production is stimulated by gangliosides and TGF-beta isoforms in human glioma cells

Hepatocyte growth factor (HGF) is a pleiotrophic cytokine that stimulates motility and invasion of several cancer cell types and induces angiogenesis, which is known to be expressed in several malignancies including glioma. The effect of transforming growth factor-beta (TGF-beta) isoforrns as well as gangliosides on HGF production was investigated in human glioma cell lines. TGF-beta isoforms and gangliosides were found to differentially stimulate HGF production by these cells. The ganglioside GD3 enhanced this release to the greatest extent and the stimulation was more marked in a glioblastoma cell line than in the two other anaplastic astrocytoma cell lines. These results suggest that both TGF-betas and gangliosides may act as indirect angiogenic factors by stimulating HGF secretion.

Examining the biomarkers and molecular mechanisms of medulloblastoma based on bioinformatics analysis

Medulloblastoma (MB) is the most common malignant brain tumor in children. The aim of the present study was to predict biomarkers and reveal their potential molecular mechanisms in MB. The gene expression profiles of GSE35493, GSE50161, GSE74195 and GSE86574 were downloaded from the Gene Expression Omnibus (GEO) database. Using the Limma package in R, a total of 1,006 overlapped differentially expressed genes (DEGs) with the cut-off criteria of P<0.05 and |log2fold-change (FC)|>1 were identified between MB and normal samples, including 540 upregulated and 466 downregulated genes. Furthermore, the Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were also performed using the Database for Annotation, Visualization and Integrated Discovery (DAVID) online tool to analyze functional and pathway enrichment. The Search Tool for Retrieval of Interacting Genes database was subsequently used to construct a protein-protein interaction (PPI) network and the network was visualized in Cytoscape. The top 11 hub genes, including CDK1, CCNB1, CCNB2, PLK1, CDC20, MAD2L1, AURKB, CENPE, TOP2A, KIF2C and PCNA, were identified from the PPI network. The survival curves for hub genes in the dataset GSE85217 predicted the association between the genes and survival of patients with MB. The top 3 modules were identified by the Molecular Complex Detection plugin. The results indicated that the pathways of DEGs in module 1 were primarily enriched in cell cycle, progesterone-mediated oocyte maturation and oocyte meiosis; and the most significant functional pathways in modules 2 and 3 were primarily enriched in mismatch repair and ubiquitin-mediated proteolysis, respectively. These results may help elucidate the pathogenesis and design novel treatments for MB.

c-Met antisense oligodeoxynucleotides increase sensitivity of human glioma cells to paclitaxel

Cell culture, tissue chemistry and flow cytometry were used to determine whether antisense c-Met oligodeoxynucleotides enhanced the sensitivity of human glioma cells to paclitaxel. A combination of paclitaxel with antisense c-Met oligodeoxynucleotides inhibited cell growth, induced apoptosis and induced c-Met protein expression in U251 and SHG44 human glioma cells more significantly than either paclitaxel or the oligodeoxynucleotides on their own (P<0.01). Thus, c-Met antisense oligodeoxynucleotides increase the sensitivity of human glioma cells to paclitaxel. Combined use of the two agents could be a novel and attractive strategy in human glioma treatment.

GNG5 is an unfavourable independent prognostic indicator of gliomas

Gliomas are the most common primary brain tumours, and glioblastomas (GBMs) are subgrouped into four distinct molecular subtypes. This study aimed to identify the potential gene related to glioma progression. Weighted gene co-expression network analysis (WGCNA) was used to explore the related gene. Correlation, ROC, survival and Cox regression analyses were performed. Blue module was strongly associated with WHO grade (r = .65, P = 1e-19). GNG5 in gliomas was overexpressed compared with normal samples and associated with clinicopathologic characteristics. GNG5 was frequent in Mesenchymal subtype and lowly expressed in Proneural subtype of GBMs. Survival and Cox regression analyses showed that glioma patients with GNG5 overexpression had shorter survival time, and GNG5 was an independent prognostic indicator of overall survival. Overall, GNG5 expression is closely associated with clinicopathologic characteristics and is an independent prognostic indicator for glioma patients, as well as a promising subtype-associated biomarker in molecular classification of gliomas.

In vitro and in vivo radiosensitization of human glioma U251 cells induced by upregulated expression of SLC22A18

Our previous study showed that solute carrier family 22 (organic cation transporter) member 18 (SLC22A18) downregulation via promoter methylation was associated with the development and progression of glioma, and the elevated expression of SLC22A18 was found to increase the sensitivity of glioma U251 cells to the anticancer drug 1,3-bis(2-chloroethyl)-1-nitrosourea. In this study, we investigated the possible upregulated expression of SLC22A18-induced enhancement of radiosensitivity of human glioma U251 cells in order to provide evidence in support of further clinical investigations. Stably overexpressing SLC22A18 human glioma U251 cells were generated to investigate the effect of SLC22A18 on the sensitivity of cells to irradiation in vitro using clonogenic survival assay. The apoptosis of U251 cells was examined with terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay. DNA damage and repair were measured using γH2AX foci. The effect of SLC22A18 on the in vivo tumor radiosensitivity was investigated in the orthotopic mice model. Upregulated expression of SLC22A18 enhanced the radiosensitivity of glioma U251 cells and also enhanced irradiation-induced apoptosis of U251 cells, but irradiation-induced apoptosis did not correlate with radiosensitizing effect of upregulated expression of SLC22A18. The repair of irradiation-induced double-strand-breaks was retarded in stably overexpressing SLC22A18 U251 cells. In the orthotopic mice model, the upregulated expression of SLC22A18 in U251 cells enhanced the effect of irradiation treatment and increased the survival time of mice. These results show that upregulated expression of SLC22A18 radiosensitizes human glioma U251 cells by suppressing DNA repair capacity.

Effect of 5-Aza-2'-deoxycytidine on SLC22A18 in glioma U251 cells

SLC22A18 [solute carrier family 22 (organic cation transporter) member 18] is located within the 11p15.5 cluster, and may be a new tumor suppressor gene; evidence of SLC22A18 hypermethylation is documented in several types of human cancers. In order to determine whether SLC22A18 hypermethylation is involved in glioma, we determined the SLC22A18 gene protein expression, mRNA expression and methylation status in glioma U251 cells before and after treatment with 5-Aza-2'‑deoxycytidine (5-Aza-CdR), and observed the change in growth. Glioma U251 cells treated with 5-Aza-CdR were analyzed by flow cytometry to identify any change in their cell cycle profiles. Tumors induced via the injection of untreated U251 cells were measured. Immunohistochemistry, reverse transcriptase-polymerase chain reaction (RT-PCR) and PCR-based methylation assay were carried out to determine SLC22A18 gene protein expression, mRNA expression and methylation status in glioma U251 cells before and after treatment with 5-Aza‑CdR. The treated cells showed an increase in their proportion in G1, from 79.2 to 83.5%, and a decrease in S phase, from 12.4 to 5.8%. The apoptotic rate increased from 6.4 to 15.8%. Tumors induced via the injection of untreated U251 cells were approximately 1.46 cm³ in size, whereas the tumors induced by U251 cells treated with 5-Aza-CdR averaged 0.88 cm³ in size. The expression levels of SLC22A18 protein and mRNA in U251 cells were increased following treatment with 5x10⁻⁷ M 5-Aza‑CdR. Prior to 5-Aza-CdR treatment, the SLC22A18 gene demonstrated hypermethylation and therefore could not be cleaved by HpaII and MspI. It is known that only the DNA digested with HpaII or MspI can be amplified. Following treatment with 5-Aza‑CdR, the SLC22A18 gene became demethylated, and could then be cleaved by both of the enzymes, and this failed to be amplified. 5-Aza-cdR may induce glioma U251 cell division and apoptosis and enhance demethylation and protein and mRNA expression of SLC22A18. The hypermethylation of SLC22A18 may be related to the transcriptional silencing of this gene. The growth inhibitory effects of 5-Aza-CdR treatment in vivo remain recognizable.

Predictive value of the SLC22A18 protein expression in glioblastoma patients receiving temozolomide therapy

BACKGROUND

Our previous study showed that SLC22A18 downregulation and promoter methylation were associated with the development and progression of glioma and the elevated expression of SLC22A18 was found to increase the sensitivity of glioma U251 cells to the anticancer drug 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). In this study, we investigated the predictive value of SLC22A18 promoter methylation and protein expression in glioblastoma multiforme (GBM) patients receiving temozolomide (TMZ) therapy.

PATIENTS AND METHODS

SLC22A18 promoter methylation and protein expression were examined by methylation-specific polymerase chain reaction (MSP) and Western blotting respectively, then we compared SLC22A18 promoter methylation and protein expression in tumor cell explants in regard to prediction of TMZ response and survival time of 86 GBM patients.

RESULTS

SLC22A18 promoter methylation was detected in 61 of 86 (71%) samples, whereas 36 of 86 (42%) cases were scored positive for SLC22A18 protein expression. Overall SLC22A18 promoter methylation was significantly related to SLC22A18 protein expression, but a subgroup of cases did not follow this association. Multivariate Cox regression analysis indicated that SLC22A18 protein expression, but not promoter methylation, was significantly correlated with TMZ therapy. SLC22A18 protein expression predicted a significantly shorter overall survival in 51 patients receiving TMZ therapy, whereas no differences in overall survival were observed in 35 patients without TMZ therapy.

CONCLUSIONS

These results show that lack of SLC22A18 protein expression is superior to promoter methylation as a predictive tumor biomarker in GBM patients receiving temozolomide therapy.

Identification of key genes and pathways in meningioma by bioinformatics analysis

Meningioma is the most frequently occurring type of brain tumor. The present study aimed to conduct a comprehensive bioinformatics analysis of key genes and relevant pathways involved in meningioma, and acquire further insight into the underlying molecular mechanisms. Initially, differentially expressed genes (DEGs) in 47 meningioma samples as compared with 4 normal meninges were identified. Subsequently, these DEGs were subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. In addition, a protein-protein interaction (PPI) network of the identified DEGs was constructed using the Search Tool for the Retrieval of Interacting Genes and visualized using Cytoscape. In total, 1,683 DEGs were identified, including 66 upregulated and 1,617 downregulated genes. The GO analysis results revealed that the DEGs were significantly associated with the 'protein binding', 'cytoplasm', 'extracellular matrix (ECM) organization' and 'cell adhesion' terms. The KEGG analysis results demonstrated the significant pathways included 'AGE-RAGE signaling pathway in diabetic complications', 'PI3K-Akt signaling pathway', 'ECM-receptor interaction' and 'cell adhesion molecules'. The top five hub genes obtained from the PPI network were JUN, PIK3R1, FOS, AGT and MYC, and the most enriched KEGG pathways associated with the four obtained modules were 'chemokine signaling pathway', 'cytokine-cytokine receptor interaction', 'allograft rejection', and 'complement and coagulation cascades'. In conclusion, bioinformatics analysis identified a number of potential biomarkers and relevant pathways that may represent key mechanisms involved in the development and progression of meningioma. However, these findings require verification in future experimental studies.