High expression of RFX4 is associated with tumor progression and poor prognosis in patients with glioblastoma

Abstract

Aim: Glioma stem cells (GSCs) have been shown to contribute to tumor development and recurrence, therapeutic resistance, and cellular heterogeneity of glioblastoma multiforme (GBM). Recently, it has been reported that GSCs lose their self-renewal ability and tumorigenic potential upon differentiation. In this study, we identified Regulatory Factor X4 (RFX4) gene to regulate GSCs’ survival and self-renewal activity in the GBM patients samples.

Materials and methods: We utilized public datasets from the Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO), Ivy Glioblastoma Atlas Project, and The Human Protein Atlas to screen candidate genes which are associated with the development of GBM and poor patients survival. Small hairpin RNA (shRNA) lentivirus was applied to knockdown RFX4 gene in GSCs.

Results: We found that RFX4 mRNA expression among the RFX family was particularly reduced during GSC differentiation. RT-qPCR analysis revealed significant downregulation of RFX4 and stem cell markers (CD15 and CD133) mRNA expressions in primary human GBM-derived GSCs cultured under serum condition. Consistently, GSCs showed significantly elevated RFX4 mRNA expression levels compared to normal astrocytes, NHA, whereas glioma cells did not. Furthermore, analysis of the TCGA data set revealed that RFX4 is highly expressed in GBM, and contributes to the lowering of patient survival. Depletion of RFX4 using shRNA lentivirus in patient GBM-derived GSCs decreased neurosphere formation and cell viability.

Conclusion: These results suggest that RFX4 is a potential risk factor for maintaining the stemness of GSCs and making glioma more malignant, and thus, could be a promising target of GBM treatment.     

内皮抑素和血管生成抑素融合基因修饰的单纯疱疹病毒对胶质瘤干细胞的体外实验研究

目的 探讨内皮抑素和血管生成抑素( Endo - Angio)融合基因修饰的单纯疱疹病毒(VAE)对胶质瘤干细胞(GSCs)的体外溶瘤作用。方法 新鲜高级别（WHOⅢ级、Ⅵ级）人脑胶质瘤标本经原代培养获得GSCs,采用流式细胞术检测其中CD133阳性细胞数,单克隆形成实验检测GSCs的自我更新能力,免疫荧光技术检测未分化GSCs的Nestin及分化后GFAP、NF和MAG的表达;MTS法检测VAE对GSCs增殖活性的影响,RT - PCR和Western blot检测Endo - Angio融合蛋白的表达并检测其对人脑微血管内皮细胞(HBMEC)增殖的影响;最后观察病毒处理后仍存活细胞的自我更新和诱导贴壁情况。结果 (1)从20例高级别胶质瘤标本中培养出4例GSCs,能够表达CD133及Nestin,具有自我更新能力和多向分化能力。(2)VAE能够感染GSCs,4例GSCs增殖活性明显下降(P＜0.05)。(3)VAE感染GSCs 48 h后,基因水平及蛋白水平都有Endo- Angio融合蛋白表达,该融合蛋白使HBMEC增殖活性明显下降(P＜0.05)。(4)VAE感染后仍存活的细胞不再具有形成GSCs球的能力,加入血清诱导后也不再贴壁生长。结论 在体外,VAE能够显著抑制GSCs活性,能够表达具有生物活性的Endo-Angio融合蛋白,为脑胶质瘤溶瘤病毒治疗开辟了新的途径。     

CD133+ glioblastoma stem-like cells induce vascular mimicry in vivo

Glioblastoma is one of the most angiogenic malignancy, the neoplastic vessels of which are likely to arise by angiogenesis and vasculogenesis. An alternative mechanism of tumor vasculature is described, termed vasculogenic mimicry, by which highly aggressive tumor cells can form vessel-like structures themselves, by virtue of their high cellular plasticity. Evidence suggests that cancer stem cells acquire a multi-potent plastic phenotype and show vasculogenic potential. In this study, we report that glioblastoma stem-like cells (GSCs) can form vasculogenic mimicry in tumor xenografts and express pro-vascular molecules. We isolated GSCs from resected human glioblastoma tissues and demonstrated their stemness, differentiation, and in vivo tumor-initiating potential. Through a limiting dilution assay, CD133+ (CD133(+)-GSC) and CD133- (CD133(-)-GSC) subpopulation of GSCs were obtained. Orthotopic xenotransplantation study revealed that these two subpopulations of GSCs shared similar efficacy in tumor formation but showed distinct intratumor vasculature. In comparison with CD133(-)-GSC, a highly vascularized anaplastic tumor, mimicking vasculogenic mimicry, was found in CD133(+)-GSC-derived tumor xenografts. Subsets of CD133(+)-GSC but not CD133(-)-GSC were capable of vascular smooth muscle-like cell differentiation, in vitro and in vivo. In tumor xenografts, endothelium-associated CD31 gene was detected in implanted CD133(-)-GSC and exclusively dispersed within the tumor tissues. Although the detailed action mechanisms required further investigation, this study demonstrated the vasculogenic capacity of brain GSCs and their cellular plasticity. The results of expression of pro-vascular molecules and differentiation of vascular-like cells suggest that GSCs may contribute to form vessel-like structures and provide a blood supply for glioblastoma cells.     

Detoxification of oxidative stress in glioma stem cells: Mechanism,clinical relevance,and therapeutic development

Neural oncogenesis is currently incurable and invariably lethal. The development of innovative treatments for this devastating cancer will require a deeper molecular understanding of how cancer cells survive, proliferate, and escape from current therapies. In high‐grade gliomas (HGGs), glioma stem cells (GSCs) may causally contribute to tumor initiation and propagation, therapeutic resistance, and subsequent recurrence of tumors. Within a tumor mass, GSCs are enriched in a hypoxic niche in which the oxidative stress levels are substantially elevated. Paradoxically, however, recent studies suggest that GSCs appear to generate less reactive oxygen species (ROS), a chemical component responsible for elevation of oxidative stress levels. To date, molecular mechanisms for how GSCs reduce oxidative stress to allow preferential survival in hypoxic areas in tumors remains elusive. This review article summarizes recent studies on the role of ROS‐reducing enzymes, including peroxiredoxin 4, in detoxifying oxidative stress preferentially for GSCs in HGGs. In addition, the therapeutic potential of some of the recently identified antioxidant chemotherapeutic agents and avenues for future research in this area are discussed. © 2014 Wiley Periodicals, Inc.     

The pathological characteristics of glioma stem cell niches

Brain tumor stem cells (BTSC) are predicted to be critical drivers of tumor progression due to their self-renewal capacity and limitless proliferative potential. Recent studies suggest that stem cells are controlled by a particular microenvironment known as a “niche”. We therefore analysed human glioma tissues and found that the CD133⁺ and nestin⁺ niches are perivascularly localized in all glioma tissues. Furthermore, there is a positive correlation between the CD133⁺ niches and CD133⁺ blood vessels, which is similar to the correlation between the nestin⁺ niches and nestin⁺ blood vessels. We demonstrate that both CD133⁺ blood vessels and nestin⁺ blood vessels have an important role in maintaining the structure of the glioma stem cell niche. Moreover, the abundance of CD133⁺ niches and nestin⁺ niches increases significantly as tumor grade increases. These findings provide a new insight into the biology of BTSC and open a new perspective for targeted therapy against the brain tumors.     

人脑胶质瘤干细胞初步研究

目的从人脑胶质瘤体外细胞系和胶质瘤组织中分离、鉴定肿瘤干细胞,为进一步研究其生物学特性奠定基础。方法将人胶质瘤SHG44细胞和手术标本制成的单细胞,分别用含血清培养基(DMEM 10% FBS)和无血清培养基(DMEM/F12,添加bFGF、LIF和EGF)培养。用CD133免疫磁珠筛选,流式细胞仪和免疫荧光共聚焦显微镜检测干细胞、祖细胞和分化细胞特异性标志物。结果SHG44细胞培养1周,用CD133磁珠分离得到的CD133~ 细胞的比例:血清组为0.021%,无血清组为1.2%。流式细胞仪检测:(1)Hoechst 33342~-细胞比例:血清组为1.5%,无血清组为16.4%;(2)nestin~ 细胞比例:血清组为7.2%,无血清组为51.05%;(3)免疫磁珠分离的CD133~ 细胞再用流式细胞仪测得的CD133~ 细胞为83.02%,CD133~-细胞群中有3.32%的CD133~ 细胞。标本源肿瘤细胞在无血清条件下培养两天后CD133磁珠分离CD133~ 细胞比例为4%。CD133~ 细胞在分化不同阶段共表达或分别表达祖细胞标志物nestin、神经元和胶质细胞特异性标志蛋白MAP2和GFAP。结论在胶质瘤细胞系和胶质瘤组织中均存在CD133~ 的脑肿瘤干细胞,具有自我更新和多向分化潜能、在无血清培养下细胞球体中CD133~ 细胞仍占少数,而nestin~ 细胞占多数,可作为进一步研究脑肿瘤干细胞生物学特性的实验材料在相关领域中的应用。     

亚甲蓝对胶质瘤干细胞增殖作用的影响

目的研究亚甲蓝(MB)对胶质瘤干细胞增殖作用的影响。方法从新鲜人脑胶质母细胞瘤标本中分离脑肿瘤细胞,接种于含生长因子的无血清改良Eagle培养基/F-12(DMEM/F-12)培养基中培养至细胞形成干细胞球,用免疫荧光法对其进行检测和鉴定。随机将细胞分为四组:正常对照组,低剂量组,中剂量组,高剂量组。采用生长曲线法,软琼脂克隆形成法检测亚甲蓝对胶质瘤干细胞增殖作用的影响,流式细胞仪检测亚甲蓝作用后的胶质瘤干细胞的凋亡情况。结果生长曲线、集落形成能力结果和凋亡检测结果均显示,与对照组及低剂量组相比,亚甲蓝中、高剂量组细胞的增殖能力明显下降,且亚甲蓝的最低有效浓度为1μM,最佳有效浓度为10μM。结论亚甲蓝可以降低胶质瘤干细胞的增殖能力。     

Downregulation of ADAMTS3 Suppresses Stemness and Tumorigenicity in Glioma Stem Cell

Aims

Glioblastoma multiforme (GBM) is the most aggressive type of human brain tumor, with a poor prognosis and a median overall survival of fewer than 15 months. Glioma stem cells (GSCs) have recently been identified as a key player in tumor initiation and therapeutic resistance in GBM. ADAMTS family of metalloproteinases is known to cleave a wide range of extracellular matrix substrates and has been linked to tissue remodeling events in tumor development. Here, we investigate that ADAMTS3 regulates GSC proliferation and self-renewal activities, and tumorigenesis in orthotopic xenograft models.

Methods

ADAMTS3 mRNA expression levels in normal human astrocyte (NHA), glioma, and GSCs cell lines were compared. After knockdown of ADAMTS3, alamarBlue assay, in vitro limiting dilution, and orthotopic xenograft assays were performed. To investigate the tumor-associated roles of ADAMTS3, several statistical assays were conducted using publicly available datasets.

Results

ADAMTS3 level was remarkably higher in GSCs than in NHA, glioma cell lines, and their matched differentiated tumor cells. Interestingly, knockdown of ADAMTS3 disrupted GSC's proliferation, self-renewal activity, and tumor formation in vivo. Furthermore, ADAMTS3 could be used as an independent predictor of malignancy progression in GBM.

Conclusion

We identified ADAMTS3 as a potential therapeutic target for GBM.     

U251细胞系来源的脑肿瘤干细胞原位移植瘤动物模型的建立

目的 从U251细胞系中分离脑肿瘤干细胞并以其为移植物建立动物模型.方法 应用悬浮培养法获得脑肿瘤干细胞,用免疫磁珠分选法分离CD133阳性和阴性细胞;将上述3种细胞植入裸鼠颅内.取移植组织切片观察及进行再培养.结果 免疫磁珠分离技术可获得CD133阳性细胞.悬浮培养法所得的细胞和CD133阳性及阴性细胞进行裸鼠原位移植的成瘤率分别为71.4％、80％和0％.结论 U251细胞系中存在脑肿瘤干细胞.裸鼠颅内注射移植脑肿瘤干细胞能够建立肿瘤模型.     

CD133基因表达与人脑胶质瘤恶性程度相关性分析

目的探讨人脑胶质瘤组织中胶质瘤干细胞标志物CD133的表达与肿瘤恶性程度的关系。方法应用实时荧光定量PCR方法检测75例不同病理级别胶质瘤组织及4例正常脑组织中CD133基因的表达情况，并与肿瘤病理级别进行相关性分析；同时采用免疫组化法检测35例肿瘤组织和2例正常脑组织中CD133的表达情况，在蛋白表达水平予以验证。结果CD133在基因转录水平和蛋白表达水平具有良好的相关性。CD133在正常脑组织中未见表达，在各级别胶质瘤中均有表达，且差异有显著性（P〈0．01）；CD133表达量与肿瘤的恶性程度呈正相关（P〈0．01）。结论检测胶质瘤CD133表达水平有助于评价肿瘤的生物学行为，并为针对肿瘤干细胞的靶向治疗提供参考依据。     

Autocrine/paracrine sphingosine‐1‐phosphate fuels proliferative and stemness qualities of glioblastoma stem cells

Accumulating reports suggest that human glioblastoma contains glioma stem‐like cells (GSCs) which act as key determinants driving tumor growth, angiogenesis, and contributing to therapeutic resistance. The proliferative signals involved in GSC proliferation and progression remain unclear. Using GSC lines derived from human glioblastoma specimens with different proliferative index and stemness marker expression, we assessed the hypothesis that sphingosine‐1‐phosphate (S1P) affects the proliferative and stemness properties of GSCs. The results of metabolic studies demonstrated that GSCs rapidly consume newly synthesized ceramide, and export S1P in the extracellular environment, both processes being enhanced in the cells exhibiting high proliferative index and stemness markers. Extracellular S1P levels reached nM concentrations in response to increased extracellular sphingosine. In addition, the presence of EGF and bFGF potentiated the constitutive capacity of GSCs to rapidly secrete newly synthesized S1P, suggesting that cooperation between S1P and these growth factors is of central importance in the maintenance and proliferation of GSCs. We also report for the first time that S1P is able to act as a proliferative and pro‐stemness autocrine factor for GSCs, promoting both their cell cycle progression and stemness phenotypic profile. These results suggest for the first time that the GSC population is critically modulated by microenvironmental S1P, this bioactive lipid acting as an autocrine signal to maintain a pro‐stemness environment and favoring GSC proliferation, survival and stem properties. GLIA 2014;62:1968–1981     

胶质瘤干细胞来源的外泌体对血管内皮细胞增殖和迁移的影响

目的探讨胶质瘤干细胞(glioma stem cells,GSCs)来源的外泌体对人脑微血管内皮细胞(HBMECs)的增殖和迁移的影响。方法培养和分离人胶质瘤U87细胞系来源的胶质瘤干细胞(GSCs),对培养的肿瘤球细胞及其诱导分化的细胞采用免疫组织化学染色的方法鉴定。然后提取胶质瘤干细胞分泌的外泌体(GSCs-exo),分别添加不同浓度的GSCsexo (20μg/ml、40μg/ml、60μg/ml)处理人脑微血管内皮细胞(HBMECs)。在处理结束后,采用CCK-8法检测GSCs-exo对血管内皮细胞增殖的影响、Transwell小室检测GSCs-exo对细胞迁移能力的影响。结果肿瘤球细胞培养状态下呈悬浮生长,免疫组织化学荧光染色法证明培养的肿瘤球细胞中特异性表达CD133和Nestin,其诱导分化的细胞染色可见GFAP和Neun表达阳性。随着GSCs-exo浓度的升高,促血管内皮细胞的增殖能力逐渐增强,迁移能力也大大提高(P 0. 05)。结论在胶质瘤微环境中,胶质瘤干细胞来源的外泌体可以促进血管内皮细胞的增殖和迁移,GSCs-exo可能是胶质瘤血管形成的关键因素。     

A molecularly distinct subset of glioblastoma requires serum-containing media to establish sustainable bona fide glioblastoma stem cell cultures

Glioblastoma (GBM) is the most frequent and deadly primary malignant brain tumor. Hallmarks are extensive intra-tumor and inter-tumor heterogeneity and highly invasive growth, which provide great challenges for treatment. Efficient therapy is lacking and the majority of patients survive less than 1 year from diagnosis. GBM progression and recurrence is caused by treatment-resistant glioblastoma stem cells (GSCs). GSC cultures are considered important models in target identification and drug screening studies. The current state-of-the-art method, to isolate and maintain GSC cultures that faithfully mimic the primary tumor, is to use serum-free (SF) media conditions developed for neural stem cells (NSCs). Here we have investigated the outcome of explanting 218 consecutively collected GBM patient samples under both SF and standard, serum-containing media conditions. The frequency of maintainable SF cultures (SFCs) was most successful, but for a subgroup of GBM specimens, a viable culture could only be established in serum-containing media, called exclusive serum culture (ESC). ESCs expressed nestin and SOX2, and displayed all functional characteristics of a GSC, that is, extended proliferation, sustained self-renewal and orthotopic tumor initiation. Once adapted to the in vitro milieu they were also sustainable in SF media. Molecular analyses showed that ESCs formed a discrete group that was most related to the mesenchymal GBM subtype. This distinct subgroup of GBM that would have evaded modeling in SF conditions only provide unique cell models of GBM inter-tumor heterogeneity.     

Pluripotent stem cell‐derived radial glia‐like cells as stable intermediate for efficient generation of human oligodendrocytes

Neural precursor cells (NPCs) derived from human pluripotent stem cells (hPSCs) represent an attractive tool for the in vitro generation of various neural cell types. However, the developmentally early NPCs emerging during hPSC differentiation typically show a strong propensity for neuronal differentiation, with more limited potential for generating astrocytes and, in particular, for generating oligodendrocytes. This phenomenon corresponds well to the consecutive and protracted generation of neurons and GLIA during normal human development. To obtain a more gliogenic NPC type, we combined growth factor‐mediated expansion with pre‐exposure to the differentiation‐inducing agent retinoic acid and subsequent immunoisolation of CD133‐positive cells. This protocol yields an adherent and self‐renewing population of hindbrain/spinal cord radial glia (RG)‐like neural precursor cells (RGL‐NPCs) expressing typical neural stem cell markers such as nestin, ASCL1, SOX2, and PAX6 as well as RG markers BLBP, GLAST, vimentin, and GFAP. While RGL‐NPCs maintain the ability for tripotential differentiation into neurons, astrocytes, and oligodendrocytes, they exhibit greatly enhanced propensity for oligodendrocyte generation. Under defined differentiation conditions promoting the expression of the major oligodendrocyte fate‐determinants OLIG1/2, NKX6.2, NKX2.2, and SOX10, RGL‐NPCs efficiently convert into NG2‐positive oligodendroglial progenitor cells (OPCs) and are subsequently capable of in vivo myelination. Representing a stable intermediate between PSCs and OPCs, RGL‐NPCs expedite the generation of PSC‐derived oligodendrocytes with O4‐, 4860‐, and myelin basic protein (MBP)‐positive cells that already appear within 7 weeks following growth factor withdrawal‐induced differentiation. Thus, RGL‐NPCs may serve as robust tool for time‐efficient generation of human oligodendrocytes from embryonic and induced pluripotent stem cells. GLIA 2015;63:2152–2167     

抑制Hedgehog信号通路对人脑胶质瘤肿瘤干细胞体外增殖的影响

目的 探讨抑制Hedgehog信号通路对人脑胶质瘤肿瘤干细胞（GSCs）体外增殖的影响。方法 收集我院手术切除的胶质母细胞瘤标本,进行分离、培养和鉴定GSCs,应用环靶明抑制Hedgehog信号通路,采用免疫组化染色检测GSCs Hedgehog信号通路相关蛋白的表达,使用CCK-8试剂盒测定GSCs的增殖活性。结果 胶质母细胞瘤标本分离出来的细胞球表达CD133及Nestin;而且表达Hedgehog信号通路关键蛋白Sonic Hedgehog和Smo。环靶明对GSCs增殖的抑制率随浓度的升高显著增高（P<0.05）,而且随作用时间延长显著增高（P<0.01）。结论 Hedeghog信号通路的特异性抑制剂环靶明能够显著抑制体外培养GSCs的增殖。     

干细胞样抗原提高树突状细胞介导胶质瘤免疫治疗的体外研究

目的 比较胶质瘤干细胞样抗原与非干细胞样抗原致敏树突状细胞(DCs)疫苗对胶质瘤的体外作用.方法 体外用无血清法和血清法培养恶性胶质瘤细胞,有限稀释法检测其克隆形成率;冻融法获取相应胶质瘤抗原;GM-CSF、IL-4体外诱导人外周血单核细胞获取DCs,与抗原孵育后再激活T淋巴细胞,同位素法检测效应细胞对胶质瘤细胞的杀伤率;流式细胞术检测DCs表面分子变化以及非贴壁细胞中T细胞比例的变化.结果 无血清培液中的胶质瘤细胞具有更高的克隆形成率(P<0.01);DCs经不同抗原刺激后HLA-A、HLA-DR、CD80、CD86表达上调(P<0.01);非贴壁细胞与DCs共培养后T细胞比例明显增高;干细胞样抗原激活的效应细胞对非干细胞样细胞和干细胞样细胞杀伤率分别为(70.2±5.13)%和(56.7±7.81)%(P<0.001),而非干细胞样抗原活化的效应细胞相应的杀伤率为(36.6±6.45)%和(9.05±3.49)%(P<0.001).结论 无血清培养液中的胶质瘤细胞具有更强的增殖能力,胶质瘤干细胞样抗原较传统抗原具有更强的抗原性,为进一步提高胶质瘤DCs疫苗疗效奠定基础.     

人脑胶质瘤中CD133、SSEA-1、Nestin的表达和意义

目的：研究胶质瘤干细胞标志物CD133、SSEA-1和Nestin在胶质瘤组织中表达及其与病理分级的相关性;探讨三者在人脑胶质瘤的诊断及恶性程度判断中的临床意义。方法应用免疫组织化学方法检测54例脑胶质瘤组织和6例正常脑组织标本中CD133、SSEA-1及Nestin的表达。结果 CD133、SSEA-1和Nestin在胶质瘤组织中的阳性细胞平均表达率分别为25.38%、26.62%和22.39%,而在正常脑组织中均无表达。CD133、SSEA-1和Nestin阳性细胞率在胶质瘤各病理级别间比较,差异均有统计学意义,且三者的表达与胶质瘤病理级别呈正相关（P＜0.05）。SSEA-1与CD133、CD133与Nestin及SSEA-1与Nestin阳性细胞表达均呈正相关（P＜0.05）。结论检测CD133、SSEA-1、Nestin表达,有利于胶质瘤的诊断及恶性程度判断,并在胶质瘤的个性化综合治疗和预后评估发挥作用。