Mesenchymal stem cells deliver synthetic microRNA mimics to glioma cells and glioma stem cells and inhibit their cell migration and self-renewal

MicroRNAs (miRNAs) have emerged as potential cancer therapeutics; however, their clinical use is hindered by lack of effective delivery mechanisms to tumor sites. Mesenchymal stem cells (MSCs) have been shown to migrate to experimental glioma and to exert anti-tumor effects by delivering cytotoxic compounds. Here, we examined the ability of MSCs derived from bone marrow, adipose tissue, placenta and umbilical cord to deliver synthetic miRNA mimics to glioma cells and glioma stem cells (GSCs). We examined the delivery of miR-124 and miR-145 mimics as glioma cells and GSCs express very low levels of these miRNAs. Using fluorescently labeled miRNA mimics and in situ hybridization, we demonstrated that all the MSCs examined delivered miR-124 and miR-145 mimics to co-cultured glioma cells and GSCs via gap junction–dependent and independent processes. The delivered miR-124 and miR-145 mimics significantly decreased the luciferase activity of their respected reporter target genes, SCP-1 and Sox2, and decreased the migration of glioma cells and the self-renewal of GSCs. Moreover, MSCs delivered Cy3-miR-124 mimic to glioma xenografts when administered intracranially. These results suggest that MSCs can deliver synthetic exogenous miRNA mimics to glioma cells and GSCs and may provide an efficient route of therapeutic miRNA delivery in vivo.     

Comprehensive analysis of microRNA expression profile in malignant glioma tissues

Malignant gliomas represent the most devastating group of brain tumors in adults, among which glioblastoma multiforme (GBM) exhibits the highest malignancy rate. Despite combined modality treatment, GBM recurs and is invariably fatal. A further insight into the molecular background of gliomagenesis is required to improve patient outcomes. The primary aim of this study was to gain broad information on the miRNA expression pattern in malignant gliomas, mainly GBM. We investigated the global miRNA profile of malignant glioma tissues with miRNA microarrays, deep sequencing and meta‐analysis. We selected miRNAs that were most frequently deregulated in glioblastoma tissues, as well as in peritumoral areas, in comparison with normal human brain. We identified candidate miRNAs associated with the progression from glioma grade III to glioma grade IV. The meta‐analysis of miRNA profiling studies in GBM tissues summarizes the past and recent advances in the investigation of the miRNA signature in GBM versus noncancerous human brain and provides a comprehensive overview. We propose a list of 35 miRNAs whose expression is most frequently deregulated in GBM patients and of 30 miRNA candidates recognized as novel GBM biomarkers.     

The genomic profile of human malignant glioma is altered early in primary cell culture and preserved in spheroids

Screening of therapeutics relies on representative cancer models. The representation of human glioblastoma by in vitro cell culture models is questionable. We obtained genomic profiles by array comparative genomic hybridization of both short- and long-term primary cell and spheroid cultures, derived from seven glioblastomas and one anaplastic oligodendroglioma. Chromosomal copy numbers were compared between cell cultures and spheroids and related to the parental gliomas using unsupervised hierarchical clustering and correlation coefficient. In seven out of eight short-term cell cultures, the genomic profiles clustered further apart from their parental tumors than spheroid cultures. In four out of eight samples, the genetic changes in cell culture were substantial. The average correlation coefficient between parental tumors and spheroid profiles was 0.89 (range: 0.79-0.97), whereas that between parental tumors and cell cultures was 0.62 (range: 0.10-0.96). In two out of three long-term cell cultures progressive genetic changes had developed, whereas the spheroid cultures were genetically stable. It is concluded that genomic profiles of primary cell cultures from glioblastoma are frequently deviant from parental tumor profiles, whereas spheroids are genetically more representative of the glioblastoma. This implies that glioma cell culture data have to be handled with the highest caution.     

Role of synaptojanin 2 in glioma cell migration and invasion

The small GTPase Rac1 is thought to play an important role in cell migration and invasion. We have previously identified synaptojanin 2, a phosphoinositide phosphatase, as an effector of Rac1. Here, we show that small interfering RNA-mediated depletion of either Rac1 or synaptojanin 2 inhibits invasion of SNB19 and U87MG glioblastoma cells through Matrigel and rat brain slices. Depletion of Rac1 or synaptojanin 2 also inhibits migration of SNB19 and U87MG cells on glioma-derived extracellular matrix. In addition, we found that depletion of Rac1 or synaptojanin 2 inhibits the formation of lamellipodia and invadopodia, specialized membrane structures that are thought to be involved in extracellular matrix degradation. These results suggest that synaptojanin 2 contributes to the role of Rac1 in cell invasion and migration by regulating the formation of invadopodia and lamellipodia. This study also identifies synaptojanin 2 as a novel potential target for therapeutic intervention in malignant tumors.     

反义microRNA-221与反义microRNA-222抑制人脑胶质瘤细胞的体外与体内生长

目的 探讨敲低microRNA(miR)-221和miR-222表达以抑制人脑胶质瘤U251细胞生长的作用及其机制.方法 脂质体介导转染反义寡聚核苷酸(AS-miR-221和AS-miR-222)于人脑胶质瘤细胞U251.采用Northern blot鉴定转染后U251细胞的miR-221和miR-222表达水平;四甲基偶氮唑蓝(MTT)法评价AS-miR-221和AS-miR-222抑制U251细胞生长的作用;Transwell实验检测细胞侵袭能力;流式细胞术检测细胞周期的分布和凋亡;Western blot检测转染后U251细胞相关蛋白表达的变化,并用AS-miR-221和AS-miR-222治疗裸鼠皮下移植瘤,观察其在活体内对肿瘤生长的抑制作用.结果 Northern blot检测结果 显示,AS-miR-221和AS-miR-222共转染后,肿瘤细胞miR-221和miR-222表达明显下降,细胞生长速度降低,细胞穿过率为14.5%,细胞周期出现G0/G1期阻滞,凋亡率(13.7%)增高,并可见connexin43、p27、PUMA、caspase-3、PTEN、TIMP3和Bax等相关蛋白表达增高,而bcl-2表达降低,p53无明显变化.经AS-miR-221和AS-miR-222治疗后,裸鼠皮下移植瘤生长明显受抑.结论 AS-miR-221和AS-miR-222共转染可抑制U251细胞的增殖与侵袭,miR-221和miR-222可以作为人脑胶质瘤基因治疗的侯选靶点.     

ALA- and ALA-ester-mediated photodynamic therapy of human glioma spheroids

The effects of photodynamic therapy (PDT) in human glioma spheroids incubated in 5-aminolevulinic acid (ALA), or ALA esters, are investigated. Spheroid survival and growth are monitored following PDT at representative drug concentrations, light doses, and dose rates. The primary finding of this study is that the response of human glioma spheroids to PDT with lipophilic ester derivatives, such as benzyl-ALA and hexyl-ALA, is equivalent to that observed with ALA, however, this equivalency is obtained for ester concentrations 10–20 times lower than the parent compound. The enhanced efficiency of the esters is likely due to their increased membrane penetrance. Potential clinical advantages of using lipophilic esters in PDT of gliomas are discussed.     

Regulation of glioma cell migration by serine-phosphorylated P311

P311, an 8-kDa polypeptide, was previously shown to be highly expressed in invasive glioma cells. Here, we report the functional characteristics of P311 with regard to influencing glioma cell migration. P311 is constitutively serine-phosphorylated; decreased phosphorylation is observed in migration-activated glioma cells. The primary amino acid sequence of P311 indicates a putative serine phosphorylation site (S59) near the PEST domain. Site-directed mutagenesis of S59A retarded P311 degradation and induced glioma cell motility. In contrast, S59D mutation resulted in the rapid degradation of P311 and reduced glioma cell migration. Coimmunoprecipitation coupled with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis identified Filamin A as a binding partner of P311, and immunofluorescence studies showed that both proteins colocalized at the cell periphery. Moreover, P311-induced cell migration was abrogated by inhibition of beta1 integrin function using TACbeta1A, a dominant-negative inhibitor of beta1 integrin signaling, suggesting that P311 acts downstream of beta1 signaling. Finally, overexpression of P311 or P311 S59A mutant protein activates Rac1 GTPase; small interfering RNA-mediated depletion of Rac1 suppresses P311-induced motility. Collectively, these results suggest a role for levels of P311 in regulating glioma motility and invasion through the reorganization of actin cytoskeleton at the cell periphery.     

Effects of vinblastine and 5-fluorouracil on human glioma and thyroid cancer cell monolayers and spheroids

The effects of the two antitumor drugs vinblastine and 5-fluorouracil on the growth of the human tumor cell lines U-118 MG (glioma) and HTh-7 (thyroid cancer) were analyzed. The cells were cultured both as monolayers and as multicellular spheroids and exposed to vinblastine (0.1, 1.0, or 10 micrograms/ml) or 5-fluorouracil (10, 100, or 1000 micrograms/ml) for 15 min, 2 hr, or 24 hr. The drugs induced growth delays of the monolayers and delays in the outgrowth of cells from spheroids which were placed on cell-adhesive surfaces. Cell cultures exposed to sublethal drug doses showed a dose-dependent lag period followed by regrowth at normal growth rates. In all cases with vinblastine exposures, the spheroids seemed more resistant to the drug treatments than did the monolayer cultures. Much smaller differences were obtained after treatments with 5-fluorouracil. The three-dimensional arrangement of cells in spheroids giving rise to, e.g., nutrient and proliferation gradients may, to some extent, be responsible for the increased resistance. The spheroids were especially resistant to short treatments with vinblastine. This was probably due to penetration barriers.     

The inhibition of proliferation and migration of glioma spheroids exposed to temozolomide is less than additive if combined with irradiation

The aim of this study was to investigate the effect of temozolomide (TZM) in combination with X-rays on proliferation and migration in human glioma spheroids. Multicellular spheroids were derived from GaMg and U87 cell lines. Spheroids were treated with various concentrations of TZM (5 micromol, 0.025 mmol, 0.05 mmol) and irradiation (RT). Proliferation and migration assays were performed. For GaMg spheroids, the proliferation inhibition was 30% (RT), 71%, 79%, 85% (for various TZM concentrations) and 78%, 83%, 90% following RT+TZM. For U87 spheroids, the inhibition of proliferation was 52% (RT), 62%, 78%, 88% (TZM), and 73%, 87%, 92% (RT+TZM). Inhibition of migration for GaMg was 30% (RT), 37%, 63%, 78% (TZM), and 56%, 75%, 84% (RT+TZM). For U87, migration inhibition was 29% (RT), 48%, 52%, 67% (TZM), and 62%, 67%, 73% (RT+TZM). Radiotherapy enhancement ratio (RER) of GaMg/U87 spheroid proliferation was 1.4/1.7 (5 micromol TZM), 1.3/1.8 (0.025 mmol TZM), and 1.4/1.4 (0.05 mmol TZM). RER for migration of GaMg/U87 was 2.2/1.9 (5 micromol TZM), 1.7/1.8 (0.025 mmol TZM), and 1.5/1.4 (0.05 mmol TZM). In terms of inhibition of proliferation and migration, irradiation can lead to an enhancement of the TZM effect in human glioma spheroids, which is less than additive.     

Combined modality therapy of gemcitabine and irradiation on human glioma spheroids derived from cell lines and biopsy tissue

Multicellular tumor spheroids have been used to examine aspects of combined modality treatment since they often recreate the in vivo tumor environment much more closely than other models. The radioenhancement by gemcitabine (dFdC) on human glioma spheroids derived from cell lines (CLS) and biopsy tissue, grown as organotypic multicellular spheroids (OMS), was studied. CLS of GaMg and U87 and OMS of four glioblastoma patients were used. Radiochemosensitvity was determined using migration and proliferation assays on CLS. In OMS, histology and immunohistochemical studies of MIB-1, p53, and p21 expression were examined 24 and 48 h following treatment. Cell death (ethidium homodimer) was studied using a fluorescence cell viability assay. In CLS, combination treatment led to migration inhibition in GaMg and U87 of 85% and 62% (dFdC 46% and 52%, RT 21% and 43%) and proliferation inhibition of 83% and 85%, respectively. Following dFdC + RT in OMS (% of cases), apoptosis and p21 expression increased (50%), p53 expression increased (75%) and cell proliferation decreased (75%). Only minor morphological damage was observed. Confocal laser scanning microscopy identified an increased dead cell core after dFdC + RT (50%). In conclusion, dFdC can lead to an additively radioenhancement in CLS and individual OMS.     

Effects of DFMO on glioma cell proliferation,migration and invasion in vitro

The polyamine inhibitor DL--difluoromethylornithine (DFMO) is a specific irreversible inhibitor of ornithine decarboxylase which is a rate-limiting enzyme in the polyamine bio-synthesis pathway. The present study describes the effects of DFMO on glioma cell proliferation, migration and invasion using multicellular spheroids from three glioma cell lines (GaMg, U-251 Mg and U-87 Mg). 10 mM DFMO reduced cell migration in the three cell lines by about 30–50%. 1 mM putrescine, added together with DFMO inhibited the DFMO effect. A stronger effect was observed in the growth assay where 10 mM DFMO reduced the spheroid growth, for all cell lines, by 90%. This effect was also reversed by adding 1 mM of putrescine. In vitro tumor cell invasion experiments indicated after 3 days of confrontation, an extensive invasion also after 10 mM DFMO treatment. The brain aggregate volumes were reduced to about the same extent as in the absence of drug, suggesting essentially no effects of DFMO on the invasive process. It is concluded that the tumor spheroids retained their ability to invade normal brain tissue even after DFMO exposure. However, DFMO inhibited spheroid growth and cell migration which supports the notion that cell growth, migration and invasion are biological properties that are not necessarily related to each other.     

Variable presence of hypoxia in M006 human glioma spheroids and in spheroids and xenografts of clonally derived sublines.

Recently we reported the variable presence of hypoxia adjacent to necrosis in human glioma lines grown as subcutaneous tumours in severe combined immunodeficient (SCID) mice. To assess the basis for this observation, we examined the pattern of oxygenation in M006 and M006XLo glioma spheroids. We found a wide range of binding of [3H]misonidazole to cells adjacent to the necrotic core, analogous to the patterns seen in xenografts, indicating substantial differences in the central oxygen tension of the spheroids. Clonal selection was used to isolate single cell-derived sublines of the M006XLo line. Some sublines gave spheroids that showed narrow distributions of [3H]misonidazole binding to the cells adjacent to necrosis, whereas other sublines showed a range of binding similar to that seen in spheroids of the parent line. After additional passages in monolayer culture, clonal sublines occasionally gave rise to spheroids in which the mean oxygen tension of cells adjacent to necrosis differed substantially from that of the initial spheroids. No relationship was evident between the thickness of the rim of viable cells and the presence or absence of central hypoxia, over a wide range of rim thickness. These results indicate that different oxygenation characteristics of glioma spheroids and tumour microregions are unlikely to arise from stable genetic variants coexisting in the parent line.     

缺氧共培养胶质瘤细胞对内皮细胞生长及凋亡的影响

目的:通过体外模拟胶质瘤缺氧微环境,研究在缺氧条件下C6胶质瘤细胞对人脐静脉内皮细胞(HUVECs)生长及凋亡的影响。方法:利用Transwell共培养装置及二氯化钴(CoCl2)模拟缺氧法,建立模拟胶质瘤缺氧微环境的体外共培养模型。通过绘制生长曲线明确内皮细胞生长状况,流式细胞仪检测内皮细胞凋亡及细胞周期。结果:缺氧能够显著抑制内皮细胞生长,促进内皮细胞凋亡。缺氧培养24小时后,内皮细胞中G1期细胞增加,S期细胞减少。相反,共培养胶质瘤细胞能够减少缺氧诱导的内皮细胞凋亡。同时,细胞周期中G1期细胞比例下降,S期细胞比例升高。结论:缺氧能够诱导内皮细胞凋亡,抑制内皮细胞增殖。而共培养胶质瘤细胞能够有效减少这种缺氧诱导的内皮细胞凋亡,促进内皮细胞有丝分裂。胶质瘤细胞可能正是通过这一机制,维持肿瘤血管发生。     

缺氧共培养胶质瘤细胞对内皮细胞生长及凋亡的影响

目的：通过体外模拟胶质瘤缺氧微环境,研究在缺氧条件下C6胶质瘤细胞对人脐静脉内皮细胞（HUVECs）生长及凋亡的影响。方法：利用Transwell共培养装置及二氯化钴（CoCl2）模拟缺氧法,建立模拟胶质瘤缺氧微环境的体外共培养模型。通过绘制生长曲线明确内皮细胞生长状况,流式细胞仪检测内皮细胞凋亡及细胞周期。结果：缺氧能够显著抑制内皮细胞生长,促进内皮细胞凋亡。缺氧培养24小时后,内皮细胞中G1期细胞增加,S期细胞减少。相反,共培养胶质瘤细胞能够减少缺氧诱导的内皮细胞凋亡。同时,细胞周期中G1期细胞比例下降,S期细胞比例升高。结论：缺氧能够诱导内皮细胞凋亡,抑制内皮细胞增殖。而共培养胶质瘤细胞能够有效减少这种缺氧诱导的内皮细胞凋亡,促进内皮细胞有丝分裂。胶质瘤细胞可能正是通过这一机制,维持肿瘤血管发生。     

Incorporation of iododeoxyuridine in multicellular glioma spheroids: implications for DNA-targeted radiotherapy using Auger electron emitters.

A promising new treatment for glioma involves Auger electron emitters such as 125I or 123I conjugated to deoxyuridine (IUdR). However, the presence in tumour deposits of non-proliferating cells with clonogenic potential poses a major limitation to this cycle-specific therapy. We have used multicellular tumour spheroids derived from the human glioma cell line UVW to study [125I]IUdR-targeted radiotherapy in aggregates containing cells in different proliferative states. Autoradiographic identification of labelled cells indicated that nuclear incorporation of [125I]IUdR decreased markedly with increasing size of spheroid. IUdR incorporation was maximal in the surface layer of cells and decreased with depth within spheroids. Radiopharmaceutical uptake corresponded closely to the regions of cell cycling as indicated by staining for the nuclear antigen Ki67. The uptake of drug was enhanced by increasing the duration of incubation from 52 h to 104 h. These observations suggest that significant sparing of non-cycling malignant cells would result from treatment delivered as a single injection of radiolabelled IUdR. To achieve maximal therapeutic effect. IUdR should be administered by multiple injections, by slow release from biodegradable implants or by slow-pump delivery.     

Differential mechanisms of radiosensitization by 2-deoxy-D-glucose in the monolayers and multicellular spheroids of a human glioma cell line

In vitro studies using monolayer cultures of human tumor cell lines have shown that 2-DG selectively inhibits energy-dependent DNA repair and cellular recovery processes in cancer cells. However, monolayer cultures differ greatly from the complex environmental conditions generated in solid tumors that develop inhomogeneous hypoxic and necrotic regions. In contrast, multicellular spheroids mimic heterogeneous cellular behavior and the consequent functional characteristics of in vivo solid tumors, and serve as important in vitro model to investigate tumor biology and responses to potential therapeutic agents. The present study compares the radiomodification by 2-DG in monolayer cultures and spheroids of a human glioma cell line (BMG-1) to gain insight into the effects in solid tumors. In spheroids, the glucose consumption (2.1 p mole/cell/h) and lactate production (3.67 p mole/cell/h) was nearly 2-3 fold higher than in monolayer cells (0.83 and 1.43 p mole/cell/h respectively). Presence of 2-DG (5 mM) for 2-4 h inhibited the glucose usage and lactate production by 70% in spheroids, while a 35% reduction was observed in monolayer cells. Under these conditions, 2-DG drastically enhanced the radiation-induced cell death of spheroids (by 2-3 folds); while a 40% increase was observed in monolayer cells. Radiosensitization by 2-DG in monolayer cells was primarily due to an increase in mitotic death (23%) linked to cytogenetic damage (micronuclei), whereas a profound induction of apoptosis (40%) accounted for the sensitization in spheroids. Although the Bcl-2 and Bax levels were significantly higher in spheroids, Bcl-2/Bax ratio was similar in monolayers and spheroids. Comet assay revealed a late onset of DNA breaks in the presence of 2- DG following irradiation only in spheroids, which corroborated well with the late onset of oxidative stress. 2-DG did not induce a significant cell cycle delay in monolayers, while a transient G(2) delay was apparent in spheroids.     

MiR-29c inhibits glioma cell proliferation, migration, invasion and angiogenesis

Previous studies reported that miR-29c is significantly downregulated in several tumors. However, little is known about the effect and molecular mechanisms of action of miR-29c in human glioma. Using quantitative RT-PCR, we demonstrated that miR-29c was significantly downregulated in glioma cell lines and human primary glioma tissues, compared to normal human astrocytes and matched non-tumor associated tissues (P < 0.05, χ² test). Overexpression of miR-29c dramatically reduced the proliferation and caused cessation of cell cycle. The reduced cell proliferation is due to G1 phase arrest as cyclin D1 and cyclin E are diminished whereas p27 and p21 are upregulated. We further demonstrated that miR-29c overexpression suppressed the glioma cell migration and invasion abilities by targeting MMP-2. In addition, we also found that overexpression of miR-29c sharply inhibited angiogenesis, which correlated with down-regulation of VEGF. The data indicate that miR-29c may be a tumor suppressor involved in the progression of glioma.     

MicroRNA-107 inhibits glioma cell migration and invasion by modulating Notch2 expression

MicroRNAs (miRNAs), small non-protein-coding RNA molecules, modulate target gene expression by binding to 3′untranslated regions (UTR) of target mRNA. These molecules are aberrantly expressed in many human cancers, and can function either as tumor suppressors or oncogenes. In the current study, we show that miR-107 is down-regulated in glioma tissues and cell lines, and its overexpression leads to inhibition of the migratory and invasive ability of glioma cells via direct targeting of Notch2, which is known to transactivate Tenascin-C and Cox-2. Experiments with Notch2 siRNA further suggest that miR-107 may exerts its anti-invasive activity through Notch2 signaling pathways. Our findings collectively indicate that miR-107 is involved in glioma cell migration and invasion, and support its utility as a potential target for glioma treatment.     

RTVP-1 regulates glioma cell migration and invasion via interaction with N-WASP and hnRNPK

Glioblastoma (GBM) are characterized by increased invasion into the surrounding normal brain tissue. RTVP-1 is highly expressed in GBM and regulates the migration and invasion of glioma cells. To further study RTVP-1 effects we performed a pull-down assay using His-tagged RTVP-1 followed by mass spectrometry and found that RTVP-1 was associated with the actin polymerization regulator, N-WASP. This association was further validated by co-immunoprecipitation and FRET analysis. We found that RTVP-1 increased cell spreading, migration and invasion and these effects were at least partly mediated by N-WASP. Another protein which was found by the pull-down assay to interact with RTVP-1 is hnRNPK. This protein has been recently reported to associate with and to inhibit the effect of N-WASP on cell spreading. hnRNPK decreased cell migration, spreading and invasion in glioma cells. Using co-immunoprecipitation we validated the interactions of hnRNPK with N-WASP and RTVP-1 in glioma cells. In addition, we found that overexpression of RTVP-1 decreased the association of N-WASP and hnRNPK. In summary, we report that RTVP-1 regulates glioma cell spreading, migration and invasion and that these effects are mediated via interaction with N-WASP and by interfering with the inhibitory effect of hnRNPK on the function of this protein.