Induction of Apoptosis in Resistant Glioma Cells by Synthetic Caspase-Activation

The detailed mechanisms behind the resistance of malignant gliomas to therapy are not known. Inherent resistance to apoptosis is, however, one plausible explanation. In the present study we tried to delineate the molecular defects and to induce apoptosis by inducible caspases in three apparently apoptosis resistant glioma cell lines. U-105 MG, U-251 MG, and SF-767 were resistant to Fas-induced apoptosis as shown by the lack of Fas-induced cell death, morphological changes, annexin-V reactivity, Parp cleavage, caspase-3 cleavage, and caspase-3 activation. The glioma cells showed no consistent down-regulation of the pro-apoptotic proteins Fas, Fadd, caspase-3, caspase-8, caspase-9, Apaf-1, Bid, Bad, or Bax, and no consistent up-regulation of the anti-apoptotic proteins Bcl-x or Bcl-2. In U-105 MG, Fas was, however, not detected at the cell surface indicating intracellular retention. To assess if the apoptotic blocks could be by-passed, we introduced the so-called artificial death switches, i.e., inducible caspases and Fadd, into the glioma cells. Synthetic activation of inducible caspase-3, but not of caspase-8, resulted in apoptosis in the three glioma cell lines and inducible Fadd induced apoptosis in SF-767. The results were consistent with a block in the apoptotic signaling pathways of glioma cells between caspase-8 and caspase-3 activation, and that inducible Fadd could induce caspase-8 independent apoptosis in some cells. Apparently resistant glioma cells could thus be induced to undergo apoptosis by activation of appropriate death switches. This might have implications for the design of future therapeutic strategies.     

不同免疫背景小鼠G422胶质瘤颅内移植瘤模型的建立

背景与目的：胶质瘤治疗效果差,是神经外科领域研究的难点。本研究建立正常免疫（Bal b／c小鼠）、T细胞免疫缺陷（裸小鼠）和补体功能缺陷（补体C3基因敲除小鼠）三种不同免疫背景的小鼠G422胶质瘤颅内移植瘤模型。并观察肿瘤的生长特点。方法：将小鼠源性G422胶质瘤细胞种植入Bat b／c小鼠、裸小鼠和补体C3基因敲除小鼠脑内．观察肿瘤种植后三种小鼠的生存期、成瘤率、肿瘤生长情况及病理学特性。结果：Bal b／c鼠、裸小鼠、补体C3基因敲除小鼠三种小鼠脑内种植G422胶质瘤细胞后,成瘤率分别为90％、100％、100％。Bal b／c荷瘤鼠平均生存期最长[（44．3±6．0）d],裸小鼠次之[（24．8±4．8）d],补体C3基因敲除小鼠最短[（18．6±5．2）d]．肿瘤体积增大至34．29mm^3需要的时间分别为35d、21d、14d;组织病理学观察显示G422胶质瘤细胞脑内种植后可保持胶质瘤的肿瘤特征。结论：采用G422小鼠胶质瘤细胞种植入Bal b／c小鼠、裸小鼠、补体C3基因敲除小鼠脑内．可建立具有不同免疫背景的胶质瘤动物模型。     

Tissue Factor and Cancer Procoagulant Expressed by Glioma Cells Participate in their Thrombin-mediated Proliferation

The relationship between coagulation cascade activation and glioma cell proliferation was examined. The human glioma cell lines T98G, TM-1 and normal human astrocyte cell strain (NHA) were examined. Using anti-tissue factor (TF) antibody, immunocytochemical detection of TF antigen was obtained in both cell lines and cell strain. TF antigen in cell lysates was also measured by enzyme linked immunosorbent assay (ELISA). In a one-stage clotting assay, T98G, TM-1 and NHA revealed procoagulant activity (PCA) in normal human plasma and factor VII deficient plasma. PCA in normal human plasma was significantly inhibited by both inhibitory anti-TF antibody and cysteine protease inhibitor HgCl₂. This result indicates that T98G, TM-1 and NHA cells express not only TF but also cancer procoagulant (CP) at the same time.In a cell proliferation assay, thrombin induced proliferation in T98G and TM-1 cells in a dose-dependent fashion and in NHA cell in a bell-shaped fashion. This mitogenic stimulant was inhibited by the specific thrombin inhibitor hirudin. The combinations of coagulation factors II, V, and X with or without factor VII induced proliferation in T98G, TM-1, and NHA cells. The maximal mitogenic stimulatory effects were larger in glioma cells than in NHA. These mitogenic stimulatory effects were also inhibited by hirudin. Each coagulation factor on its own or in any other combination of coagulation factors had no proliferative effect. Thus, these mitogenic stimulatory effects were considered to be the effect of thrombin.In conclusion, T98G and TM-1 human glioma cells express two different types of procoagulants TF and CP. In the presence of coagulation factors, these glioma cells can generate thrombin and this thrombin generation is capable of inducing glioma cell proliferation in vitro.     

脑胶质瘤干细胞和U251人胶质瘤细胞系X线辐射敏感性研究

目的：研究脑胶质瘤干细胞 （Brain glioma stem cell） 和U251胶质瘤细胞系对不同剂量X线的射线敏感性。方法： 从脑胶质瘤组织中分离培养脑胶质瘤肿瘤球, 用CD133免疫磁珠技术分离得到脑胶质瘤干细胞; 经不同剂量X线照射脑胶质瘤干细胞和U251细胞后, 用软琼脂克隆形成实验检测两者的放射敏感性。结果： 1） 从脑胶质瘤组织中分离胶质瘤干细胞。2） 随着照射剂量的增加, 两种细胞的存活率均出现下降, 但肿瘤干细胞的存活率明显高于U251细胞 （t=-3.71, P<0.01）。3） 根据公式SF=exp（-αD-βD2） 对实验数据进行拟合, 得到干细胞和U251细胞的α/β值分别为3.57、 7.15。结论： 脑胶质瘤干细胞与U251胶质瘤细胞系相比具有较强的辐射抗拒性。     

Autophagy Involvement in Olanzapine-Mediated Cytotoxic Effects in Human Glioma Cells

The aim of this study was to investigate the effects of olanzapine on growth inhibition as well as autophagy inglioma cells in vitro and in vivo. The proliferation of both LN229 and T98 glioma cells, measured by MTT assay,was suppressed in a concentration-dependent and time-dependent manner. Moreover, apoptosis of both cellswas significantly increased with the treatment of olanzapine as evidenced by increased Bcl-2 expression, Hoechst33258 staining and annexinV-FITC/PI staining. Olanzapine treatment also enhanced activation of autophagy withincreased expression of LC3-II, expression of protein p62, a substrate of autophagy, being decreased. The growthinhibition by olanzapine in both glioma cell lines could be blocked by co-treatment with 3-MA, an autophagyinhibitor. Furthermore, olanzapine effectively blocked the growth of subcutaneous xenografts of LN229 gliomacells in vivo. The increased level of protein LC3-II and decreased level of p62 followed by a decreased level ofBcl-2, suggesting that autophagy may contribute to apoptosis. In addition, reduced proliferation of glioma cellswas shown by a decrease of Ki-67 staining and increased caspase-3 staining indicative of apoptosis in mousexenografts. These results indicated that olanzapine inhibited the growth of glioma cells accompanied by inductionof autophagy and apoptosis both in vitro and in vivo. Olanzapine-induced autophagy plays a tumor-suppressingrole in glioma cells.     

BH3 Mimetics Reactivate Autophagic Cell Death in Anoxia-Resistant Malignant Glioma Cells

Here, we investigated the specific roles of Bcl-2 family members in anoxia tolerance of malignant glioma. Flow cytometry analysis of cell death in 17 glioma cell lines revealed drastic differences in their sensitivity to oxygen withdrawal (<0.1% O₂). Cell death correlated with mitochondrial depolarization, cytochrome C release, and translocation of green fluorescent protein (GFP)-tagged light chain 3 to autophagosomes but occurred in the absence of caspase activation or phosphatidylserine exposure. In both sensitive and tolerant glioma cell lines, anoxia caused a significant up-regulation of BH3-only genes previously implicated in mediating anoxic cell death in other cell types (BNIP3, NIX, PUMA, and Noxa). In contrast, we detected a strong correlation between anoxia resistance and high expression levels of antiapoptotic Bcl-2 family proteins Bcl-xL, Bcl-2, and Mcl-1 that function to neutralize the proapoptotic activity of BH3-only proteins. Importantly, inhibition of both Bcl-2 and Bcl-xL with the small-molecule BH3 mimetics HA14-1 and BH3I-2′ and by RNA interference reactivated anoxia-induced autophagic cell death in previously resistant glioma cells. Our data suggest that endogenous BH3-only protein induction may not be able to compensate for the high expression of antiapoptotic Bcl-2 family proteins in anoxia-resistant astrocytomas. They also support the conjecture that BH3 mimetics may represent an exciting new approach for the treatment of malignant glioma.     

全反式维甲酸诱导大鼠C6脑胶质瘤细胞凋亡的实验研究

目的: 探讨全反式维甲酸对大鼠C6脑胶质瘤细胞的增殖抑制及其分子机制。 方法: MTT法检测全反式维甲酸作用于大鼠C6脑胶质瘤细胞后,观察其对细胞增殖抑制率的影响。流式细胞仪观察肿瘤细胞周期及凋亡率的变化。电镜观察C6细胞超微结构变化。Western blot法在不同时间点对凋亡相关基因caspase-3活性蛋白产物的表达进行了检测。 结果: MTT结果表明ATRA对C6细胞的抑制作用具有时间和浓度依赖性。流式细胞仪检测证明与对照组相比,处理组C6细胞发生G₁期阻滞;S、G₂期细胞比例下降;细胞出现亚二倍峰,凋亡比例明显增加。电镜下全反式维甲酸作用72h后处理组C6细胞呈凋亡改变:如核固缩、染色质趋边凝聚。Western blot检测发现,处理组出现了caspase-3蛋白活性裂解片段。 结论: 全反式维甲酸抑制C6脑胶质瘤细胞生长,全反式维甲酸抑制脑胶质瘤的作用机理可能至少通过改变细胞周期分布、诱导凋亡来实现。     

Nanomolar Concentrations of Epothilone D Inhibit the Proliferation of Glioma Cells and Severely Affect their Tubulin Cytoskeleton

The purpose of this study was to investigate the potential effects of epothilones (EPOs), a new class of microtubule stabilizing cytotoxic drugs, on glioma cells in vitro. The effects of 1, 10 and 100 nM concentrations of EPO D in four malignant human glioma cell lines were measured using a microtiter-tetrazolium assay. Besides the cell lines U87MG, U138MG and LN405, one cell line was used, which had been derived from a recurrent and therapy-resistant glioblastoma in our laboratory. In addition, changes of the cell morphology were followed by light microscopy and changes in the microtubule and actin cytoskeleton were visualized by a confocal laser microscope. In all four human glioma cell lines, 10 and 100 nM concentrations of the drug, applied for 96 h, lead to a highly significant decrease in the viable cell number (p < 0.001). A mean reduction of the viable cell number between 30% and 40% (60% and 90%) was observed for a drug concentration of 10 nM (100 nM). A round cell morphology occured in most EPO treated cells and the organized network of microtubules was shrunk in these round cells. The tubulin immunostaining now appeared amorphous and was restricted to small perinuclear regions. Large actin filaments also disappeared, but actin staining was present in the whole cytosplasm. These results prove that EPOs have antiproliferative effects in glioma cells and affect their tubulin cytoskeleton, as it was previously observed in several types of carcinoma cells.     

胶质瘤干细胞对放射线一定抗拒吗?

放射治疗是恶性胶质瘤最重要的辅助治疗方法之一。近年来多数研究表明胶质瘤干细胞相对于非干细胞对于放射线更加抗拒。但是最近有研究表明,胶质瘤干细胞并不一定比传统胶质瘤细胞系抗拒。并且,报道发现微环境有助于胶质瘤细胞放射损伤的修复。以后的研究需要更加重视胶质瘤细胞在体内对于放射线的反应。     

胶质瘤干细胞样细胞中MGMT表达以及与替莫唑胺的耐药关系研究

背景与目的:O6甲基鸟嘌呤DNA甲基转移酶(O6-methylguanine DNA methyltranferase,MGMT)是一种能将鸟嘌呤DNA第六位氧氧原子上的甲基加合物移除和修复损伤DNA的酶,临床上能影响甲基化类化疗药物的疗效。胶质瘤干细胞样细胞被认为是胶质瘤复发的根源之一。本研究旨在探讨MGMT在胶质瘤干细胞样细胞中的表达以及与替莫唑胺耐药的关系。方法:采用悬浮克隆球形成法自胶质瘤细胞株U251、SKMG-4、SF295、SKMG-1、U373、U87、MGR1和MGR2中富集胶质瘤干细胞样细胞。应用免疫荧光技术检测胶质瘤干细胞样细胞相关分子标志;裸鼠移植瘤试验检测胶质瘤干细胞样细胞的成瘤能力。RT-PCR和Western blot检测胶质瘤干细胞样细胞中MGMT的表达;甲基化特异性PCR分析胶质瘤干细胞样细胞MGMT启动子甲基化状况;CCK-8法检测不同浓度替莫唑胺对胶质瘤干细胞样细胞和胶质瘤细胞增殖的作用。结果:分别自8个胶质瘤细胞株中成功富集胶质瘤干细胞样细胞:U251G、SKMG-4G、SF295G、SKMG-1G、U373G、U87G、MGR1G和MGR2G。胶质瘤干细胞样细胞高表达CD133、Nestin和Sox-2等干细胞标志,而且低表达GFAP和TUJ1。胶质瘤干细胞样细胞均能在裸鼠移植成瘤。MGMT在8株胶质瘤细胞及U87G、MGR1G和MGR2G中为阴性,而在U251G、SKMG-4G、SF295G、SKMG-1G和U373G中为阳性表达。替莫唑胺对胶质瘤干细胞样细胞和胶质瘤细胞的抑制作用差异具有显著性。胶质瘤干细胞样细胞与胶质瘤亲代细胞相比更加耐药(P<0.05)。另外,替莫唑胺对MGMT阳性及MGMT阴性胶质瘤干细胞样细胞IC50间的差异无统计学意义(P>0.05)。结论:MGMT阴性表达的胶质瘤细胞经干细胞样培养后,MGMT表达可转为阳性;胶质瘤干细胞样细胞较胶质瘤亲代细胞更耐受替莫唑胺;MGMT的表达与胶质瘤干细胞样细胞对替莫唑胺的耐受之间无明显关联,提示胶质瘤干细胞样细胞对替莫唑胺的耐药可能还有MGMT以外的机制参与。     

人脑胶质瘤原代细胞培养及体外药物敏感度的实验

目的 探索人脑胶质瘤细胞原代培养的方法,研究不同胶质瘤患者对抗肿瘤药物的敏感度。　方法 采用组织块培养法对39例人脑胶质瘤细胞进行原代培养,用MTT法检测胶质瘤细胞对阿霉素(ADM)、顺铂(DDP)、长春新碱(VCR) 、威猛(teniposide,VM 26)和5 氟尿嘧啶(5 Fu) 5种化疗药物的敏感度,并对其结果进行分析。结果 脑胶质瘤细胞原代培养37例成功,2例失败,成功率94.9%;37例培养成功者药敏检测显示不同个体对不同抗肿瘤药物的抑制率存在明显差异,各药物的平均抑制率依次为VM 26>DDP>5 Fu>ADM>VCR,其敏感率分别为56.8%、51.4%、37.8%、24.3%和13.5%。 结论 体外胶质瘤细胞原代培养和MTT法检测化疗药物的敏感度是可行的,检测化疗药物敏感度对胶质瘤患者个体化的化疗具有一定价值。     

Growth Inhibition and Radiosensitization of Cultured Glioma Cells by Nitric Oxide Generating Agents

The authors examined the effect of nitric oxide (NO) generating agents on the growth and radiosensitivity of cultured glioma cells. Three glioma, rat C6, and human T98G and U87 cell lines were treated with the NO generating agents, S-nitroso-N-acetyl-penicillamine (SNAP) or sodium nitroprusside (SNP). These agents released NO in the cell culture media and inhibited the growth of the glioma cells. Growth-inhibition was attenuated by hemoglobin, a known inhibitor of NO, suggesting it is mediated by NO. When C6 and T98G cells were irradiated in the presence of SNAP or SNP at 100µM, radiosensitization was observed. SNAP at 100µM exhibited a sensitizer enhancement ratio (SER) of 1.4 for C6 cells and 1.8 for T98G cells. SNP at 100µM only radiosensitized T98G cells with a SER of 1.9. The effect of SNP on radiosensitization of C6 cells was unclear. We conclude that NO generating agents are potential growth inhibitors and radiosensitizers for malignant glioma cells. NO mediated radiosensitization of glioma cells by NO generating agents may offer a new therapeutic approach for malignant glioma.     

The Role of Fascin in the Migration and Invasiveness of Malignant Glioma Cells

Malignant glioma is the most common primary brain tumor, and its ability to invade the surrounding brain parenchyma is a leading cause of tumor recurrence and treatment failure. Whereas the molecular mechanisms of glioma invasion are incompletely understood, there is growing evidence that cytoskeletal-matrix interactions contribute to this process. Fascin, an actin-bundling protein, induces parallel actin bundles in cell protrusions and increases cell motility in multiple human malignancies. The role of fascin in glioma invasion remains unclear. We demonstrate that fascin is expressed in a panel of human malignant glioma cell lines, and downregulation of fascin expression in glioma cell lines by small interfering RNA (siRNA) is associated with decreased cellular attachment to extracellular matrix (ECM) and reduced migration. Using immunofluorescence analysis, we show that fascin depletion results in a reduced number of filopodia as well as altered glioma cell shape. In vitro invasiveness of U251, U87, and SNB19 glioma cells was inhibited by fascin siRNA treatment by 52.2%, 40.3%, and 23.8% respectively. Finally, we show a decreased invasiveness of U251-GFP cells by fascin knockdown in an ex vivo rat brain slice model system. This is the first study to demonstrate a role for fascin in glioma cell morphology, motility, and invasiveness.     

Complement activation in vivo in cancer patients receiving C. parvum immunotherapy.

Serum complement levels were assayed in 26 patients with disseminated cancer, who received immunotherapy with infusion of C. parvum. Complement activation, indicated by the consumption of C3 or C4 or both, was found in 46% of the patients. Serum samples showed direct correlation between decreased C3 and conversion of C3 proactivator, whereas such conversion did not occur when C4 alone was decreased. It is concluded that the bypass (properdin) pathway was activated in patients in whom C3 consumption was detected, while the classical (C1) pathway was activated in the patients with C4 consumption unaccompanied by C3 decrease. Direct correlation was observed between delayed cutaneous hypersensitivity reactions to recall antigens and the incidence of C. parvum-associated complement activation.     

C6胶质瘤细胞培养上清诱导神经干细胞迁移的初步研究

背景与目的:研究发现胶质瘤细胞中存在着诱导神经干细胞迁移的物质,本实验旨在观察体外培养的胶质瘤细胞在体外能否引起神经干细胞的迁移,从而为研究胶质瘤细胞中存在促进神经干细胞迁移的物质打下基础;并进一步分离、纯化该物质。方法:分别培养神经干细胞、星形胶质细胞和C6胶质瘤细胞。以星形胶质细胞为对照,做细胞迁移实验,观察其结果;将C6胶质瘤细胞、星形胶质细胞的无血清培养上清分别浓缩,并行SDS-聚丙烯酰胺凝胶电泳,观察其结果;转膜,测序,初步测定这种能诱导神经干细胞迁移的信号物质。结果:(1)C6胶质瘤细胞的培养上清引起神经干细胞迁移的数目明显多于星形胶质细胞的培养上清和新鲜无血清培养基(P<0.05)。(2)将无血清培养的等浓度的C6胶质瘤细胞、星形胶质细胞的上清浓缩蛋白进行SDS-PAGE,可见二者蛋白条带存在明显差异。结论:(1)从新生大鼠大脑皮层组织可以培养出神经干细胞和星形胶质细胞。(2)C6胶质瘤细胞无血清培养的上清中存在着能够诱导神经干细胞迁移的物质。     

Hyperthermia Promotes Apoptosis and Suppresses Invasion in C6 Rat Glioma Cells

Gliomas are a group of heterogeneous primary central nervous system tumors. Hyperthermia has provento be a potential therapeutic tool for cancers in the clinic. However, the molecular mechanisms of hyperthermiaremain unclear. The objective of this study was to investigate the effects of hyperthermia on the invasivenessin C6 glioma cells and related molecular pathways. Here our data show hyperthermia stimulated the release oftumor necrosis factor-alpha (TNF-α) and decreased C6 glioma cell migration and invasive capability at 30, 60,120 and 180 min; with increased spontaneous apoptosis in C6 glioma cells at 120 min. We also found mitogenactivatedprotein kinase (P38 MAPK) protein expression to be increased and nuclear factor-kappa B (NF-κB)protein expression decreased. Based on the results, we conclude that hyperthermia alone reduced invasion ofC6 glioma cells through stimulating TNF-α signaling to activate apoptosis, enhancing P38 MAPK expressionand inhibiting the NF-κB pathway, a first report in C6 rat glioma cells.     

Mild Heat Shock Induces Autophagic Growth Arrest,But Not Apoptosis in U251-MG and U87-MG Human Malignant Glioma Cells

Although hyperthermia has been used as a treatment of malignant brain tumors, it is not yet clear what is the mechanism of the cell growth inhibition by heat shock, especially by the temperature which has clinically been applied to tumor-brain border-zone, 42-43 degrees C. Therefore, we evaluated the change of U251-MG and U87-MG human malignant glioma cells after 43 degrees C-heat shock comparing with that of 45 degrees C. First, we observed that cell growth was transiently inhibited after 43 degrees C-heat shock for 3 or 5 days, in U251-MG or U87-MG cells, respectively, which was followed by regrowth. During the period of transient growth inhibition, mild G2/M arrest was observed. However, apoptosis was observed in only 2.7% or 1.5%, of 43 degrees C-heated cells, in U251-MG or U87-MG cells, respectively. Instead, transmission electron micrography showed the formation of vacuoles, degeneration of mitochondria, and autophagosomes. Moreover, in the both cell lines, flow-cytometric analysis with acridine orange revealed the induction of acidic vesicle organelles, which was blocked by 3-methyladenine (3-MA), suggesting the involvement of autophagy. Furthermore, while 3-MA did not increase the anti-tumor effect of 43 degrees C-heat shock, bafilomycin A1, another autophagy inhibitor, did significantly enhance the effect in U251-MG cells. Taken together, mild heat shock (43 degrees C for 2 h) causes autophagy and mild G2/M arrest, but does not induce apparent apoptosis in U251-MG and U87-MG glioma cells. Inhibition of autophagy with bafilomycin A1 may increase the anti-tumor efficacy of mild heat shock against some malignant glioma cells.     

BCL-2 Family Proteins Modulate Radiosensitivity in Human Malignant Glioma Cells

Radiotherapy is the standard treatment for glioblastoma. Here, we assessed the radiosensitivity of 12 human malignant glioma cell lines in vitro and correlated these data with irradiation-induced cell cycle changes, chemosensitivity profiles and BCL-2 family protein expression. Irradiation at 3Gy failed to cause major cell cycle perturbations. Radioresistance was associated with collateral sensitivity to the topoisomerase II inhibitors, teniposide and doxorubicin. High levels of BCL-X_L and low levels of BAX were independently linked to radioresistance. Ectopic expression of a BAX transgene induced radiosensitization in the LN-18 cell line. Thus, BCL-2 family protein expression modulates radiosensitivity in human glioma cells and targeted alterations in BCL-2 family protein expression are a promising strategy to improve the therapeutic efficacy of radiotherapy for gliomas.