LRRC4 controls in vitro invasion of glioblastoma cells through inhibiting RPTP-zeta expression

LRRC4 (leucine rich repeat containing 4), a novel member of LRP (Leucine-rich repeat protein) superfamily, contains a conserved leucine-rich repeat (LRR) cassette and an immunoglobulin-like (IgC2) domain in its extracellular region. In the present study, we demonstrated that the N and C terminal LRR (LRRNT and LRRCT) are requisite for membrane and cytoplasm location of LRRC4 in Cos7 cells. We also suggested that RPTP-zeta (receptor-type protein tyrosine phosphatase) receptor is relevant to the invasion ability of gliomas cells, and its expression is inhibited by the reexpression of LRRC4. Our observations indicated that LRRC4 may be a negative regulator of the RPTP-zeta receptor, and contribute to suppressing the invasion ability of gliomas cells.Minghua Wu, Kai Gan, Chen Huang contributed equally to this work.     

塞来昔布对胶质瘤U251细胞增殖、凋亡和Survivin表达的影响

背景与目的:选择性COX-2抑制剂塞来昔布是近年来开发的新型非甾体类抗炎药。大量实验证明塞来昔布具有明显的抑制肿瘤细胞增殖和诱导凋亡的作用,这在结直肠肿瘤和家族性腺瘤性息肉病中已经得到了证实。本研究观察塞来昔布在体外对人胶质瘤细胞株U251的抑制增殖和诱导凋亡的作用,并探讨该作用与Survivin表达之间的关系。方法:用不同浓度塞来昔布溶液处理对数生长期的U251细胞,在倒置显微镜下动态观察瘤细胞的生长情况。用MTT比色法检测不同时间点各药物浓度组细胞增殖情况。不同浓度塞来昔布处理U251细胞48h后,用流式细胞技术检测各组细胞的凋亡率,免疫细胞化学法及Westernblot法检测各组细胞中Survivin蛋白的表达情况,逆转录聚合酶链反应(RT-PCR)半定量法检测各组细胞中survivinmRNA的表达水平。结果:塞来昔布处理后细胞出现明显凋亡样形态学改变。10~100μmol/L塞来昔布对U251细胞增殖均有抑制作用,该作用随着药物浓度的增加和作用时间的延长而增强。塞来昔布处理U251细胞48h后,流式细胞检测结果显示出明显的细胞凋亡,凋亡率随着塞来昔布浓度的增高而升高;免疫细胞化学结果显示,对照组细胞...     

Flavonoids activated caspases for apoptosis in human glioblastoma T98G and U87MG cells but not in human normal astrocytes

BACKGROUND:

Human glioblastoma is a deadly brain cancer that continues to defy all current therapeutic strategies. The authors induced apoptosis in human glioblastoma T98G and U87MG cells after treatment with apigenin, (?)‐epigallocatechin, (?)‐epigallocatechin‐3‐gallate (EGCG), and genistein, which did not induce apoptosis in human normal astrocytes.

METHODS:

Induction of apoptosis was examined using Wright staining and ApopTag assay. Production of reactive oxygen species (ROS) and increase in intracellular free Ca²⁺ were measured by fluorescent probes. Analysis of mRNA and Western blotting indicated increases in expression and activities of the stress kinases and cysteine proteases for apoptosis. JC‐1 showed changes in mitochondrial membrane potential (ΔΨ_m), and use of specific inhibitors confirmed activation of kinases and proteases in apoptosis.

RESULTS:

Treatment of glioblastoma cells with apigenin, (?)‐epigallocatechin, EGCG, or genistein triggered ROS production that induced apoptosis with phosphorylation of p38 mitogen‐activated protein kinase (MAPK) and activation of the redox‐sensitive c‐Jun N‐terminal kinase 1 pathway. Pretreatment of cells with ascorbic acid attenuated ROS production and p38 MAPK phosphorylation. Increases in intracellular free Ca²⁺ and activation of caspase‐4 indicated involvement of endoplasmic reticulum stress in apoptosis. Other events in apoptosis included overexpression of Bax, loss of ΔΨ_m, mitochondrial release of cytochrome c and Smac into the cytosol, down‐regulation of baculoviral inhibitor‐of‐apoptosis repeat‐containing proteins, and activation of calpain, caspase‐9, and caspase‐3. (?)‐Epigallocatechin and EGCG also induced caspase‐8 activity. Apigenin, (?)‐epigallocatechin, EGCG, and genistein did not induce apoptosis in human normal astrocytes.

CONCLUSIONS:

Results strongly suggest that flavonoids are potential therapeutic agents for induction of apoptosis in human glioblastoma cells. Cancer 2010. © 2010 American Cancer Society.     

RNA interference targeting survivin exerts antitumoral effects in vitro and in established glioma xenografts in vivo

Malignant glioma represents the most common primary adult brain tumor in Western industrialized countries. Despite aggressive treatment modalities, the median survival duration for patients with glioblastoma multiforme (GBM), the highest grade malignant glioma, has not improved significantly over past decades. One promising approach to deal with GBM is the inactivation of proteins essential for survival or progression of glioma cells by means of RNA interference (RNAi) techniques. A likely candidate for an RNAi therapy of gliomas is the inhibitor of apoptosis protein survivin. Survivin is involved in 2 main cellular processes-cell division and inhibition of apoptosis. We show here that stable RNAi of survivin induced polyploidy, apoptosis, and impaired proliferation of human U343-MG, U373-MG, H4, and U87-MG cells and of primary glioblastoma cells. Proteome profiler arrays using U373-MG cells identified a novel set of differentially expressed genes upon RNAi-mediated survivin knockdown. In particular, the death receptor TRAIL R2/DR5 was strongly upregulated in survivin-depleted glioma cells, inducing an enhanced cytotoxic response of allogeneic human NK cells. Moreover, an experimental in vivo therapy using polyethylenimine (PEI)/siRNA complexes for survivin knockdown efficiently blocked tumor growth of established subcutaneous U373-MG tumors and enhanced survival of NMRI(nu/nu) mice orthopically transplanted with U87-MG cells. We conclude that survivin is functionally relevant in gliomas and that PEI-mediated exogenous delivery of siRNA targeting survivin is a promising strategy for glioblastoma therapy.     

Expression of cytoplasmic and nuclear Survivin in primary and secondary human glioblastoma

Clinically, human glioblastoma (GBM) may develop de novo or from a low-grade glioma (secondary GBM), and molecular alterations in the two pathways may differ. This study examined the status of Survivin expression and apoptosis in 30 primary and 26 secondary GBMs. Our results show that cytoplasmic Survivin positivity was significantly (P<0.001) more frequent in primary GBMs (83%) than that in secondary GBMs (46%). In addition, an inverse correlation of cytoplasmc Survivin positivity with GBM apoptotic index, and a positive association between cytoplasmic Survivin and size of the tumours were observed. These results suggest that cytoplasmic Survivin, via its antiapoptotic function, may be involved in the tumorigenesis of many primary GBMs, but only in a small fraction of secondary GBMs. Furthermore, the overall progression times from low-grade precursor lesions to secondary GBMs were significantly shorter (P<0.05) in cytoplasmic Survivin-positive cases (mean, 15.6 months) than those in Survivin-negative cases (mean, 23.8 moths), and the positive expression level of Survivin in cytoplasm was upregulated in most secondary GBMs when compared to matched pre-existing low-graded lesions. These results suggest that the increased accumulation of Survivin in the cytoplasm of more malignant glioma cells may prove to be a selective advantage, thus accelerating progression to a more aggressive phenotype.     

LRRC4基因表达能降低胶质母细胞瘤细胞系U251的生长和成瘤潜能

背景与目的：LRRC4是作者最近克隆的一个新基因,该基因在原发性脑肿瘤活检标本中明显表达下调。本研究旨在研究LRRC4基因是否具有抑制脑肿瘤生长的能力。方法：LRRC4基因的全长编码区被亚克隆至表达载体pcDNA3．1中,应用脂质体转染的方法将重组的质粒载体导入胶质母细胞瘤细胞系U251,经G418筛选,建立稳定表达LRRC4基因的U251的细胞系。采用细胞增殖实验、软琼脂实验、肿瘤形成实验来考察LRRC4基因表达对于细胞生长和肿瘤形成的影响。结果：经过脂质体转染和筛选,建立了稳定表达LRRC4全长编码区的U251细胞系,用于进一步实验。比较未转染组和转染空白载体组,Northern blot实验证实转染了LRRC4基因的细胞LRRC4 mRNA的表达增强。细胞增殖一定时间后,转染LRRC4基因的细胞较未转染细胞的生长速度明显减慢,克隆形成率明显降低。将这些细胞注射入无胸腺裸鼠体内,40天后处死裸鼠,测量肿瘤大小,结果显示,转染LRRC4基因的细胞形成的肿瘤明显小于对照组。结论：LRRC4基因可转染于人脑胶质母细胞瘤细胞系U251。LRRC4在U251细胞的表达有抑制瘤细胞增殖和抑制裸鼠移植瘤的形成和生长的作用。     

靶向survivin的siRNA对骨肉瘤细胞MG63的抑制作用

目的：探讨针对人survivin基因的siRNA对骨肉瘤细胞MG63的体内外抑制作用。方法：合成survivin基因的RNA干涉（RNA interferance,RNAi）特异性片段,构建survivin特异性的RNA干涉载体pSiS,转染MG63细胞,G418筛选稳定转染的细胞系。细胞计数检测细胞生长情况;Western blotting检测细胞中survivin蛋白表达的变化;通过Annexin V法染色和流式细胞术检测细胞凋亡;观察裸鼠皮下MG63移植瘤的形成。结果：成功构建了survivin基因siRNA真核表达载体pSiS,获得了稳定转染的细胞MG63/pSiS。与MG63、MG63/pSi（空质粒对照细胞）相比,MG63/pSiS细胞生长曲线十分平缓,差异有统计学意义（P〈0.01）;Western blotting显示,MG63/pSiS细胞中survivin蛋白表达减少,细胞凋亡率增加（P〈0.01）。MG63/pSiS移植瘤形成明显受到抑制。结论：Survivin特异性siRNA可明显促进骨肉瘤细胞MG63的凋亡,抑制该肿瘤细胞体外生长和体内移植成瘤。     

In vitro and in vivo characterization of a novel Hedgehog signaling antagonist in human glioblastoma cell lines

Glioblastoma multiforme (GBM) is composed of heterogeneous and genetically different cells, which are highly invasive and motile. The standard chemotherapeutic agent, temozolomide, affects GBM cell proliferation but is generally unable to prevent tumor recurrence. Hedgehog pathway activation has been reported to be relevant in GBM and different pharmacological pathway modulators have been identified. We report that by growing a commercially available recurrent GBM cell line (DBTRG-05MG) without serum and in the presence of defined growth factors; we obtained a less differentiated cell population, growing in suspension as neurospheres, in which the Hedgehog pathway is activated. Furthermore, the expression profile of Hedgehog pathway components found in DBTRG-05MG neurospheres is similar to primary stem-like cells derived from recurrent GBM patients. We report the effect of our novel specific Smoothened receptor antagonist (SEN450) on neurosphere growing cells and compared its effect to that of well known benchmark compounds. Finally, we showed that SEN450 is both antiproliferative on its own and further reduces tumor volume after temozolomide pretreatment in a mouse xenograft model using DBTRG-05MG neurosphere cells. Altogether our data indicate that the Hedgehog pathway is not irreversibly switched off in adherent cells but can be reactivated when exposed to well-defined culture conditions, thus restoring the condition observed in primary tumor-derived material, and that pharmacological modulation of this pathway can have profound influences on tumor proliferation. Therefore, pharmacological inhibition of the Hedgehog pathway is a potentially useful therapeutic approach in GBM.     

Molecular and functional MDR1-Pgp and MRPs expression in human glioblastoma multiforme cell lines

The aim of our study was to investigate the functional expression of P-glycoprotein (Pgp) and multidrug resistance-associated proteins (MRPs) in 2 distinct glioma cells (GL15 and 8MG) from patients with glioblastoma multiforme. MDR1 gene and Pgp expression was not detected in either cell line by RT-PCR and Western blotting, respectively. In contrast, MRP1 was detected at both mRNA and protein level in both cell lines, with a higher expression in the 8MG cells that occur predominantly at the cell membrane. Three other MRPs (MRP3, MRP4 and MRP5) were detected by RT-PCR in both cell lines, whereas MRP2 was not expressed. In addition, MRP3 protein was also detected by immunocytochemistry in both GL15 and 8MG cell lines. Indomethacin and probenecid, 2 modulators of MRPs activity, increased the accumulation of vincristine and etoposide, 2 substrates of MRPs, by both cell lines. These modulators also decreased the efflux of vincristine from both cell lines with a more pronounced effect in 8MG cells. In conclusion, our results show functional expression of MRPs leading to a decrease in the intracellular vincristine and etoposide concentrations in human glioblastoma cell lines. Furthermore, our results that exhibit protein expression of MRP1 and MRP3 and gene expression of MRP4 and MRP5 in these 2 glioblastoma cell lines suggest new mechanisms that could lead to a MDR phenotype of tumour cells in patients with glioblastoma multiforme.     

Oncolytic adenovirus mediated Survivin knockdown by RNA interference suppresses human colorectal carcinoma growth in vitro and in vivo

Background

Colorectal cancer is a one of the most common alimentary malignancies. Survivin has been proved by many studies to be an ideal target for cancer gene therapy because of its strong anti-apoptotic effect. The reduction of Survivin expression by means of chemically synthesized small interfering RNA or small hairpin RNA expressed from plasmid and resulted growth inhibition of cancer cells had been proved by many studies including ours, but the transfection efficiency was not encouraging. So for the first time we constructed the Survivin shRNA into an oncolytic adenovirus, tested its effects on colorectal cancer cell lines and nude mice xenograft model.

Methods

In this study, we constructed an oncolytic adenovirus with a Survivin targeted small hairpin RNA and a reporter gene (ZD55-Sur-EGFP). The expression of Survivin mRNA and protein were analyzed by RT-PCR and western blot. The cell growth and apoptosis were tested by in vitro cytopathic assay, MTT assay and flow cytometry respectively. The effect of the constructed virus on xenograft model was evaluated by tumor volume and western blot analysis.

Results

ZD55-Sur-EGFP replicated in cancer cells specifically, reduced the expression of Survivin mRNA and protein expression effectively (P < 0.0001), induced cancer cell apoptosis and inhibited SW480 cell growth both in vitro and in vivo significantly.

Conclusion

We conclude Survivin RNA interference combining with oncolytic adenovirus virotherapy to be a promising treatment for colorectal cancer.     

溶瘤新城疫病毒抑制IL-6诱导的人胶质母细胞瘤U87MG细胞的迁移和侵袭

目的：探讨溶瘤新城疫病毒（NDV）对IL-6诱导的人胶质母细胞瘤U87MG细胞增殖、迁移和侵袭的作用及其可能的机制。方法：将U87MG细胞分为对照组、IL-6组、NDV组、NDV+IL-6组,其中IL-6组与NDV+IL-6组用75 ng/mL IL-6预处理1 h,其余组用DMEM预处理1 h,后分别用DMEM、75 ng/mL IL-6、1 HU NDV、1 HU NDV+75 ng/mL IL-6处理24 h。MTT法、细胞划痕实验和Transwell侵袭实验分别检测IL-6、NDV对U87MG细胞增殖、迁移和侵袭的影响,WB法检测各组细胞JAK2、p-JAK2、STAT3、p-STAT3和MMP2蛋白的表达水平。结果：与对照组相比,IL-6组细胞迁移率显著升高（P<0.05）,侵袭细胞数目显著增多（P<0.01）;与IL-6组相比,NDV+IL-6组U87MG细胞增殖率显著降低（P<0.05）,细胞迁移率和侵袭细胞数目均显著降低（均P<0.01）。WB实验结果显示,与对照组相比,IL-6组p-STAT3/STAT3比值显著升高（P<0.01）,ND...     

Survivin promotes glioma angiogenesis through vascular endothelial growth factor and basic fibroblast growth factor in vitro and in vivo

Survivin is involved in multiple signaling mechanisms in tumor maintenance, and accumulated studies elucidate that knockdown of survivin in endothelial cells could inhibit angiogenesis; however, the role of survivin in tumor cells to regulate tumor-derived angiogenesis remains largely unclear. In the present study 80 cases of brain glioma were chosen and protein expressions of survivin, vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and platelet-derived growth factor (PDGF) in glioma cells were investigated by immunohistochemistry (IHC). Human umbilical vein endothelial cells (HUVEC) were cocultured with human glioma U251 wild-type cells, U251 cells survivin silenced, SHG44 wild-type cells, and SHG44 survivin-overexpressing cells, respectively. The proliferation and migration of HUVEC were evaluated by MTT assay and transwell chamber assay. The microvessels density (MVD) marked by CD31 expression in vascular endothelial cells in glioma xenografts in nude mice was detected by IHC. VEGF, bFGF, and PDGF in the aforementioned cells were detected by quantitive PCR (qPCR), Western blot, ELISA, and IHC in vitro and in vivo. The results showed that VEGF immunoreactivity score (IRS), bFGF IRS, and PDGF IRS were all positively correlated with survivin IRS in gliomas, respectively (P < 0.01). Survivin in human glioma cells could significantly promote the proliferation and migration of HUVEC and increase MVD, which could be contributed to survivin-dependent burst of VEGF and bFGF expression, followed by increase of tumor growth and proliferation. In summary, survivin, through upregulation of VEGF and bFGF, plays an essential role during glioma angiogenesis.     

Asterosaponin 1, a cytostatic compound from the starfish Culcita novaeguineae, functions by inducing apoptosis in human glioblastoma U87MG cells

Summary Malignant glioblastoma is one of the most common malignant tumors in the neurological system. Asterosaponin 1, a new cytostatic agent from the starfish Culcita novaeguineae appear to exhibit various biological activities, including antitumor effect, but the function and mechanism of this new agent on glioblastoma cells has not previously been determined. In the present study, we investigated the proliferation change of human glioblastoma U87MG cells exposed to different concentrations (2.5–20.0 μg/ml) of asterosaponin 1 for a certain time. The results showed that asterosaponin 1 significantly suppressed U87MG cell proliferation in a time- and dose-dependent manner (IC₅₀ =4.3 μg/ml). Flow cytometric analysis of DNA in U87MG cells showed that asterosaponin 1 induces the prominent appearance of a sub-G1 peak in the cell cycle suggestive of apoptosis identical with the result of annexin V/PI assay. Furthermore, U87MG cells treatment with asterosaponin 1 resulted in nuclear condensation with apoptotic bodies observed by both fluorescence and electron microscopy. Agarose gel electrophoresis of DNA from asterosaponin 1-treated cells revealed a typical “ladder” consistent with apoptotic DNA fragmentation. Western-blot staining showed asterosaponin 1 decreased the expression of Bcl-2 protein and increased the expression of Bax protein. The novel findings suggest that the cytostatic actions of asterosaponin 1 toward U87MG cells result from the induction of cell apoptosis. Overall, our data demonstrate that asterosaponin 1 is fully equipped for an efficient apoptotic killing of glioblastoma cells and suggest that this mechanism may play a critical role in anti-tumor chemotherapy.Guang Cheng, Xiang Zhang and Hai-Feng Tang contributed equally to this work     

Nucleolin antagonist triggers autophagic cell death in human glioblastoma primary cells and decreased in vivo tumor growth in orthotopic brain tumor model

Nucleolin (NCL) is highly expressed in several types of cancer and represents an interesting therapeutic target. It is expressed at the plasma membrane of tumor cells, a property which is being used as a marker for several human cancer including glioblastoma. In this study we investigated targeting NCL as a new therapeutic strategy for the treatment of this pathology. To explore this possibility, we studied the effect of an antagonist of NCL, the multivalent pseudopeptide N6L using primary culture of human glioblastoma cells. In this system, N6L inhibits cell growth with different sensitivity depending to NCL localization. Cell cycle analysis indicated that N6L-induced growth reduction was due to a block of the G1/S transition with down-regulation of the expression of cyclin D1 and B2. By monitoring autophagy markers such as p62 and LC3II, we demonstrate that autophagy is enhanced after N6L treatment. In addition, N6L-treatment of mice bearing tumor decreased in vivo tumor growth in orthotopic brain tumor model and increase mice survival. The results obtained indicated an anti-proliferative and pro-autophagic effect of N6L and point towards its possible use as adjuvant agent to the standard therapeutic protocols presently utilized for glioblastoma.     

End-binding 1 protein overexpression correlates with glioblastoma progression and sensitizes to Vinca-alkaloids in vitro and in vivo

End-binding 1 protein (EB1) is a key player in the regulation of microtubule (MT) dynamics. Here, we investigated the role of EB1 in glioblastoma (GBM) tumor progression and its potential predictive role for response to Vinca-alkaloid chemotherapy. Immunohistological analysis of the 109 human GBM cases revealed that EB1 overexpression correlated with poor outcome including progression-free survival and overall survival. Downregulation of EB1 by shRNA inhibited cell migration and proliferation in vitro. Conversely, EB1 overexpression promoted them and accelerated tumor growth in orthotopically-transplanted nude mice. Furthermore, EB1 was largely overexpressed in stem-like GBM6 that display in vivo a higher tumorigenicity with a more infiltrative pattern of migration than stem-like GBM9. GBM6 showed strong and EB1-dependent migratory potential. The predictive role of EB1 in the response of GBM cells to chemotherapy was investigated. Vinflunine and vincristine increased survival of EB1-overexpressing U87 bearing mice and were more effective to inhibit cell migration and proliferation in EB1-overexpressing clones than in controls. Vinca inhibited the increase of MT growth rate and growth length induced by EB1 overexpression. Altogether, our results show that EB1 expression level has a prognostic value in GBM, and that Vinca-alkaloid chemotherapy could improve the treatment of GBM patients with EB1-overexpressing tumor.     

Combined VEGF and CXCR4 antagonism targets the GBM stem cell population and synergistically improves survival in an intracranial mouse model of glioblastoma

Glioblastoma recurrence involves the persistence of a subpopulation of cells with enhanced tumor-initiating capacity (TIC) that reside within the perivascular space, or niche (PVN). Anti-angiogenic therapies may prevent the formation of new PVN but have not prevented recurrence in clinical trials, suggesting they cannot abrogate TIC activity. We hypothesized that combining anti-angiogenic therapy with blockade of PVN function would have superior anti-tumor activity. We tested this hypothesis in an established intracranial xenograft model of GBM using a monoclonal antibody specific for murine and human VEGF (mcr84) and a Protein Epitope Mimetic (PEM) CXCR4 antagonist, POL5551. When doses of POL5551 were increased to overcome an mcr84-induced improvement in vascular barrier function, combinatorial therapy significantly inhibited intracranial tumor growth and improved survival. Anti-tumor activity was associated with significant changes in tumor cell proliferation and apoptosis, and a reduction in the numbers of perivascular cells expressing the TIC marker nestin. A direct effect on TICs was demonstrated for POL5551, but not mcr84, in three primary patient-derived GBM isolates. These findings indicate that targeting the structure and function of the PVN has superior anti-tumor effect and provide a strong rationale for clinical evaluation of POL5551 and Avastin in patients with GBM.