X-rays modulate extracellular matrix in vivo.

X-rays have an antiangiogenic effect in the chicken embryo chorioallantoic membrane (CAM) model of in vivo angiogenesis. Our study demonstrates that X-rays induce an early apoptosis of CAM cells, modulate the synthesis and deposition of extracellular matrix (ECM) proteins involved in regulating angiogenesis and affect angiogenesis induced by tumour cells implanted onto the CAM. Apoptosis was evident within 1-2 hr, but not later than 6 hr after irradiation. Fibronectin, laminin, collagen type I, integrin alpha(v)beta3 and MMP-2 protein amounts were all decreased 6 hr after irradiation. In contrast, collagen type IV, which is restricted to basement membrane, was not affected by irradiation of the CAM. There was a similar decrease of gene expression for fibronectin, laminin, collagen type I and MMP-2, 6 hr after irradiation. The levels of mRNA for integrin alpha(v)beta3 and collagen type IV were unaffected up to 24 hr after irradiation. The decrease in both protein and mRNA levels was reversed at later time points and 48 hr after irradiation, there was a significant increase in the expression of all the genes studied. When C6 glioma tumour cells were implanted on irradiated CAMs, there was a significant increase in the angiogenesis induced by tumour cells, compared to that in non-irradiated CAMs. Therefore, although X-rays have an initial inhibitory effect on angiogenesis, their action on the ECM enhances new vessel formation induced by glioma cells implanted on the tissue.     

Blockage of angiotensin II type I receptor decreases the synthesis of growth factors and induces apoptosis in C6 cultured cells and C6 rat glioma

Angiotensin II (Ang II) is a main effector peptide in the renin-angiotensin system and participates in the regulation of vascular tone. It also has a role in the expression of growth factors that induce neovascularisation which is closely associated to the growth of malignant gliomas. We have shown that the selective blockage of the AT1 receptor of angiotensin inhibits tumour growth, cell proliferation and angiogenesis of C6 rat glioma. The aim of this study was to study the effects of the blockage of AT1 receptor on the synthesis of growth factors, and in the genesis of apoptosis in cultured C6 glioma cells and in rats with C6 glioma. Administration of losartan at doses of 40 or 80 mg kg(-1) to rats with C6 glioma significantly decreased tumoral volume and production of platelet-derived growth factor, vascular endothelial growth factor and basic fibroblast growth factor. It also induced apoptosis in a dose-dependent manner. Administration of Ang II increased cell proliferation of cultured C6 cells which decreased by the administration of losartan. Our results suggest that the selective blockage of AT1 diminishes tumoral growth through inhibition of growth factors and promotion of apoptosis.     

鸦胆子油乳注射液对C6胶质瘤细胞作用的实验研究

背景与目的:鸦胆子油乳注射液在临床上用于许多肿瘤的治疗,然而其确切的分子机制目前尚不完全清楚。本研究探讨鸦胆子油乳注射液对C6胶质瘤细胞增殖作用的影响。方法:体外培养大鼠C6胶质瘤细胞,用MTT比色法检测鸦胆子油乳注射液对C6胶质瘤细胞的抑制作用。用免疫组化检测鸦胆子油乳注射液对C6胶质瘤细胞caspase-3表达的影响。结果:MTT比色法显示鸦胆子油乳注射液对C6胶质瘤细胞的抑制率呈剂量依赖性。免疫组化显示随鸦胆子油乳注射液浓度增加,caspase-3表达明显增多。结论:体外鸦胆子油乳注射液能增加C6胶质瘤细胞凋亡基因caspase-3表达,抑制细胞增殖。     

Sublethal irradiation promotes migration and invasiveness of glioma cells: implications for radiotherapy of human glioblastoma

Human malignant gliomas are highly lethal neoplasms. Involved-field radiotherapy is the most important therapeutic measure. Most relapses originate from the close vicinity of the irradiated target field. Here, we report that sublethal doses of irradiation enhance the migration and invasiveness of human malignant glioma cells. This hitherto unknown biological effect of irradiation is p53 independent, involves enhanced alphavbeta3 integrin expression, an altered profile of matrix metalloproteinase-2 and matrix metalloproteinase-9 (MMP-2 and MMP-9) expression and activity, altered membrane type 1 MMP and tissue inhibitor of metalloproteinases-2 expression, and an altered BCL-2/BAX rheostat favoring resistance to apoptosis. BCL-2 gene transfer and irradiation cooperate to enhance migration and invasiveness in a synergistic manner. Sublethal irradiation of rat 9L glioma cells results in the formation of a greater number of tumor satellites in the rat brain in vivo concomitant with enhanced MMP-2 and reduced tissue inhibitor of metalloproteinases-2 expression. Collectively, these data suggest that the current concepts of involved-field radiotherapy for malignant glioma need to be reconsidered and that the pharmacological inhibition of migration and invasion during radiotherapy may represent a new therapeutic approach to improve the therapeutic efficacy of radiotherapy for malignant glioma.     

Protamine inhibits angiogenesis and growth of C6 rat glioma; a synergistic effect when combined with carmustine

Protamine inhibits angiogenesis and blocks endothelial, fibroblast and platelet growth factors. Human and experimental gliomas spread and grow in response to both paracrine and autocrine release of these factors. Our objective was to study the effect of protamine administration on cell proliferation, angiogenesis and tumoral growth of C6 glioma. Additionally, we compared the antitumoral effect of protamine with that of another inhibitor of angiogenesis, suramin, and investigated a potential synergistic antitumoral action of low doses of protamine combined with the antineoplastic carmustine. C6 glioma cells were implanted subcutaneously in Wistar rats. A highly malignant glioma developed in 80% of animals; when the tumour reached a diameter of 1.5 cm, either protamine, suramin, carmustine or protamine plus carmustine were administered in various doses. Tumour parameters were measured and compared between groups. In a dose-dependent manner, protamine reduced tumour volume (P < 0.001), mitotic index (P < 0.05), vascular density (P < 0.05) and cell viability (P < 0.005) of C6 glioma. An ultrastructural study demonstrated membranous inclusions in the cytoplasm of 28% of tumoral and endothelial cells of tumours from animals treated with protamine. The inhibition of tumoral growth produced by moderate doses of protamine was similar to that produced by toxic doses of suramin. The combination of protamine and carmustine had a synergistic curtailing effect on tumoral growth (P < 0.001). Our results indicate that protamine is an effective agent against glioblastoma; in non-toxic doses it could potentiate the antineoplastic effect of nitrosoureas for the treatment of glial tumours.     

Induction of differentiation and tetraploidy by long-term treatment of C6 rat glioma cells with erucylphosphocholine

Induction of differentiation represents a promising concept for chemotherapy of malignant gliomas, which are often refractory even to the combined treatment with surgery, irradiation and chemotherapy. Since anti-neoplastic alkylphosphocholines can induce differentiation of leukemic cell lines, the effects of the intravenously applicable alkylphosphocholine-derivative erucylphosphocholine (ErPC) on proliferation, morphology and differentiation of the rat glioma cell line C6 was examined in vitro. Short-term exposure to ErPC induced accumulation of the cells in the G2/M-phase of the cell cycle and apoptotic cell death. In contrast, continuous exposure of C6 rat glioma cells to sublethal ErPC doses (30 and 50 microM) caused both the formation of a slower growing tetraploid cell population and astrocytic differentiation. No resistance to in vivo obtainable ErPC concentrations was observed during this treatment. We conclude that ErPC-induced differentiation might be beneficial for a long-term adjuvant chemotherapy of low grade glioma.     

Cas IIgly induces apoptosis in glioma C6 cells in vitro and in vivo through caspase-dependent and caspase-independent mechanisms

In this work, we investigated the effects of Casiopeina II-gly (Cas IIgly)--a new copper compound exhibiting antineoplastic activity--on glioma C6 cells under both in vitro and in vivo conditions, as an approach to identify potential therapeutic agents against malignant glioma. The exposure of C6 cells to Cas IIgly significantly inhibited cell proliferation, increased reactive oxygen species (ROS) formation, and induced apoptosis in a dose-dependent manner. In cultured C6 cells, Cas IIgly caused mitochondrio-nuclear translocation of apoptosis induction factor (AIF) and endonuclease G at all concentrations tested; in contrast, fragmentation of nucleosomal DNA, cytochrome c release, and caspase-3 activation were observed at high concentrations. Administration of N-acetyl-L-cystein, an antioxidant, resulted in significant inhibition of AIF translocation, nucleosomal DNA fragmentation, and caspase-3 activation induced by Cas IIgly. These results suggest that caspase-dependent and caspase-independent pathways both participate in apoptotic events elicited by Cas IIgly. ROS formation induced by Cas IIgly might also be involved in the mitochondrio-nuclear translocation of AIF and apoptosis. In addition, treatment of glioma C6-positive rats with Cas IIgly reduced tumor volume and mitotic and cell proliferation indexes, and increased apoptotic index. Our findings support the use of Cas IIgly for the treatment of malignant gliomas.     

TAM对C6细胞生长与侵袭能力的影响

目的:通过观察TAM对体外培养C6细胞生长状况、迁移能力与MMP-2蛋白表达的影响,为TAM用于胶质瘤的治疗提供理论依据。方法:观察不同剂量TAM对大鼠C6胶质瘤细胞生长曲线、细胞倍增时间及细胞形态的影响,研究TAM对C6细胞的生长抑制作用;细胞划痕法检测不同剂量TAM对C6细胞迁移能力的影响;FITC标记的可激活穿膜肽检测不同剂量TAM对C6细胞MMP-2蛋白表达的影响。结果:TAM显著抑制C6胶质瘤细胞的生长,且存在剂量、时间依赖关系;TAM显著抑制C6细胞迁移,存在剂量依赖关系;TAM对C6细胞活性MMP-2蛋白的表达未见明显影响。结论:虽然TAM不能抑制C6细胞MMP-2蛋白的表达,但可显著抑制其生长与迁移,因此有望用于胶质瘤的化学治疗。     

~(60)Co γ射线对HeLa细胞端粒酶活性的影响

 目的　探讨γ射线对人宫颈癌细胞系HeLa端粒酶活性的影响。方法　不同剂量的γ射线照射HeLa细胞后 2 4h、72h、12 0h ,用TRAP ELISA法检测端粒酶的活性。结果　γ射线照射细胞后 2 4h ,较低剂量 (0 .5～ 1.5 )Gy时 ,端粒酶的活性呈剂量依赖式增加 ;(2～ 3)Gy时增加的幅度减低 ;而较高剂量 (4～ 12 )Gyγ射线照射时 ,又呈剂量依赖式增加。与照射后 2 4h相比 ,在较高剂量 (4～ 12 )Gy照射后 72h及 12 0h ,酶的活性呈剂量依赖式减少。结论　HeLa细胞在较高剂量γ射线照射后 2 4h出现的端粒酶活性上调反应 ,可能是其组分从DNA释放增加或者与端粒酶的核内位置调节有关 ;较低剂量照射后的上调反应 ,可能与DNA的修复 ,稳定断裂的染色体有关。     

多柔比星X射线联合诱导大鼠C6胶质瘤细胞凋亡

目的 :进行胶质瘤细胞凋亡的分子生物学研究及探讨化疗联合放疗治疗新策略在脑胶质瘤治疗中的潜在用途。方法 :通过光镜、电镜、DNA断裂分析 ,进行多柔比星X射线联合诱导C6胶质瘤细胞凋亡研究。结果 :光镜和电镜可见细胞形态学上出现细胞皱缩 ,染色质浓集贴边 ;DNA电泳表现出DNA呈梯状带段裂。结论 :多柔比星、X射线成功地诱导大鼠C6胶质瘤细胞发生凋亡     

The expression of P2X7 receptors in EPCs and their potential role in the targeting of EPCs to brain gliomas

In order to use endothelial progenitor cells (EPCs) as a therapeutic and imaging probe to overcome antiangiogenic resistance for gliomas, how to enhance proliferation and targeting ability of transplanted EPCs is a high priority. Here, we confirmed, for the first time, the expression of P2X₇ receptors in rat spleen-derived EPCs. Activation of P2X₇ receptors in EPCs by BzATP promoted cells proliferation and migration, rather than apoptosis. In vivo, the homing of transplanted EPCs after long-term suppression of P2X₇ receptors by persistent BBG stimulation was evaluated by MRI, immunohistochemistry and flow cytometry. Compared to the group without BBG treatment, less transplanted EPCs homed to gliomas in the group with BBG treatment, especially integrated into the vessels containing tumor-derived endothelial cells in gliomas. Moreover, western blot showed that CXCL1 expression was downregulated in gliomas with BBG treatment, which meant P2X₇ receptors suppression inhibited the homing of EPCs to gliomas through down-regulation of CXCLl expression. Further, effects of P2X₇ receptors on C6 glioma cells or gliomas were evaluated at the same dose of BzATP or BBG used in EPCs experiments in vitro and in vivo. MTT assay and MRI revealed that P2X₇ receptors exerted no significant promoting effect on C6 glioma cells proliferation, gliomas growth and angiogenesis. Taken together, our findings imply the possibility of promoting proliferation and targeting ability of transplanted EPCs to brain gliomas in vivo through P2X₇ receptors, which may provide new perspectives on application of EPCs as a therapeutic and imaging probe to overcome antiangiogenic resistance for gliomas.     

IL-24基因对大鼠胶质瘤细胞生长状况的影响

目的　探讨IL 2 4基因对C6大鼠胶质瘤细胞生长状况的影响。方法　应用逆转录病毒载体 ,将IL 2 4基因导入C6细胞 ,经G4 18筛选后获得表达IL 2 4分子的阳性细胞克隆C6 /IL 2 4 ;用RT PCR方法检测目的基因表达 ;四甲基偶氮唑蓝 (MTT)法检测细胞体外增殖状况 ,流式细胞技术检测细胞的增殖活性 ,并制作荷瘤动物模型 ,观察C6 /IL 2 4和C6细胞的体内致瘤性。结果　RT PCR检测表明 ,外源IL 2 4基因于mRNA水平在C6 /IL 2 4细胞已获得稳定表达。C6 /IL 2 4细胞系的体外增殖性较亲代C6细胞明显下降 ,流式细胞术检测其细胞增殖指数 (PI)为 (2 9.71± 0 .89) %。 9只接种C6 /IL 2 4细胞的实验组大鼠中 ,6只颅内成瘤 ,肿瘤体积为 (14 .0 8± 9.81)mm3 ,明显小于接种C6细胞大鼠的肿瘤体积 (P <0 .0 5 )。结论　外源性IL 2 4基因可部分抑制胶质瘤细胞异常增殖的肿瘤特性。     

Tamoxifen-induced apoptosis of rat C6 glioma cells via PI3K/Akt, JNK and ERK activation

To elucidate the mechanism of TAM treatment on gliomas, we hypothesised that PI3K/Akt and MAPK signaling pathway may play important roles on TAM-induced apoptosis in C6 glioma cells. Our results demonstrated that TAM induced apoptosis of C6 glioma cells in a dose-dependent manner. The activation of AKT significantly decreased in a time-dependent manner in response to TAM treatment, JNK was transiently activated, and subsequently decreased activation and kept stable level, whereas ERK evidenced sustained activations in response to the drug treatment. The inhibition of PI3K/Akt and JNK both accelerated and enhanced TAM-induced apoptosis and ERK inhibition apparently exerted negative effect on apoptosis. We also observed that PI3K/Akt had intimate association with JNK and ERK activation in TAM-induced apoptosis. These findings may provide strategies for the molecularly targeted therapy in malignant gliomas.     

Targeting hyaluronan interactions in malignant gliomas and their drug-resistant multipotent progenitors.

PURPOSE: To determine if hyaluronan oligomers (o-HA) antagonize the malignant properties of glioma cells and treatment-resistant glioma side population (SP) cells in vitro and in vivo. EXPERIMENTAL DESIGN: A single intratumoral injection of o-HA was given to rats bearing spinal cord gliomas 7 days after engraftment of C6 glioma cells. At 14 days, spinal cords were evaluated for tumor size, invasive patterns, proliferation, apoptosis, activation of Akt, and BCRP expression. C6SP were isolated by fluorescence-activated cell sorting and tested for the effects of o-HA on BCRP expression, activation of Akt and epidermal growth factor receptor, drug resistance, and glioma growth in vivo. RESULTS: o-HA treatment decreased tumor cell proliferation, increased apoptosis, and down-regulated activation of Akt and the expression of BCRP. o-HA treatment of C6SP inhibited activation of epidermal growth factor receptor and Akt, decreased BCRP expression, and increased methotrexate cytotoxicity. In vivo, o-HA also suppressed the growth of gliomas that formed after engraftment of C6 or BCRP+ C6SP cells, although most C6SP cells lost their expression of BCRP when grown in vivo. Interestingly, the spinal cord gliomas contained many BCRP+ cells that were not C6 or C6SP cells but that expressed nestin and/or CD45; o-HA treatment significantly decreased the recruitment of these BCRP+ progenitor cells into the engrafted gliomas. CONCLUSIONS: o-HA suppress glioma growth in vivo by enhancing apoptosis, down-regulating key cell survival mechanisms, and possibly by decreasing recruitment of host-derived BCRP+ progenitor cells. Thus, o-HA hold promise as a new biological therapy to inhibit HA-mediated malignant mechanisms in glioma cells and treatment-resistant glioma stem cells.     

Tamoxifen体内外抑制胶质瘤细胞生长研究

目的：探讨Tamoxifen在体内外对胶质瘤细胞的抑制作用及其机制；方法：Tamoxifen在体内外作用于C6大鼠胶质瘤细胞系，并用MTT法、TUNEL法、免疫组化及动态MRI来检测效果；结果：Tamoxifen能在体外明显抑制胶质瘤细胞生长，在体内抑制作用尚不确定；Tamoxifen可抑制PKC及IGF-1表达；结论：Tamoxifen抑制胶质瘤细胞生长的机制之一可能是抑制PKC及IGF-1活性。     

Neuronal and glioma-derived stem cell factor induces angiogenesis within the brain

Stem cell factor (SCF) is overexpressed by neurons following brain injury as well as by glioma cells; however, its role in gliomagenesis remains unclear. Here, we demonstrate that SCF directly activates brain microvascular endothelial cells (ECs) in vitro and induces a potent angiogenic response in vivo. Primary human gliomas express SCF in a grade-dependent manner and induce normal neurons to express SCF in brain regions infiltrated by glioma cells, areas that colocalize with prominent angiogenesis. Downregulation of SCF inhibits tumor-mediated angiogenesis and glioma growth in vivo, whereas overexpression of SCF is associated with shorter survival in patients with malignant gliomas. Thus, the SCF/c-Kit pathway plays an important role in tumor- and normal host cell-induced angiogenesis within the brain.     

Radiosensitizing effect of 5-aminolevulinic acid-induced protoporphyrin IX in glioma cells in vitro

5-Aminolevulinic acid (ALA) is a prodrug used in photodynamic therapy and fluorescence-guided resection of malignant gliomas due to its high cellular uptake in tumours. Porphyrin compounds act not only as photosensitizers but also as radiosensitizers. In the present study, the possible use of 5-ALA as a radiosensitizer for malignant gliomas was examined in vitro. Rat glioma cell lines (9L, C6) were pre-treated with 5-ALA and exposed to ionizing irradiation. The radiosensitizing effect of 5-ALA was evaluated by colony-forming assay. Intracellular reactive oxygen species (ROS) produced by 5-ALA and irradiation were evaluated by confocal laser scanning microscopy. Pre-treatment with 5-ALA enhanced the radiosensitivity of 9L cells to single-dose ionizing irradiation compared with controls (D0 value, 4.35 ± 0.20 and 4.84 ± 0.23 Gy, respectively, P ≤ 0.05). Exposure to multi-dose ionizing irradiation revealed high radiosensitivity in both 9L and C6 cells pre-treated with 5-ALA compared to controls. Production of intracellular ROS increased in 9L cells pre-treated with 5-ALA after ionizing irradiation compared to control cells. Thus, 5-ALA functions as a specific radiosensitizer for malignant gliomas. Intracellular 5-ALA-induced PpIX plays an important role in the production of ROS and the radiosensitizing effect under ionizing irradiation conditions.     

纳米Fe3O4／CD133Ab复合物对胶质瘤U251细胞放疗增敏作用的实验研究

目的 探讨纳米Fe3O4／CD133Ab复合物对脑胶质瘤U251细胞的放射增敏作用。方法 细胞免疫组化法检测脑胶质瘤U251细胞CD133的表达情况;流式细胞分选获得U251-CD133+细胞;MTT法观察纳米Fe3O4／CD133Ab复合物和CD133Ab分别对脑胶质瘤细胞U251及U251-CD133+的细胞毒作用;克隆形成抑制实验检测纳米Fe3O4／CD133Ab复合物和CD133Ab对脑胶质瘤U251细胞放射增敏的影响。结果 脑胶质瘤U251细胞中有CD133分子阳性表达并可以分选出CD133阳性表达细胞;在0.0488～25μg／ml范围内,纳米Fe3O4／CD133Ab复合物作用于脑胶质瘤U251及U251-CD133+细胞24h的细胞毒性呈明显剂量依赖性,与阴性对照组比较,差异有统计学意义（P＞0.05）。纳米Fe3O4／CD133Ab复合物对脑胶质瘤U251和U251-CD133+细胞的增殖抑制率最高值分别为59.46％和56.66％,IC50分别为11.84μg／ml和12.06μg／ml。纳米Fe3O4／CD133Ab复合物+照射组与CD133Ab+照射组比较,细胞存活分数差异有统计学意义（P＜0.05）,在照射4Gy以上时,随X射线剂量增加而放射敏感性增强。结论 纳米Fe3O4／CD133Ab复合物对脑胶质瘤细胞U251和U251-CD133+有细胞毒作用,并且对U251细胞有放射增敏作用。