TrkB-BDNF信号通路对神经母细胞瘤细胞分泌血管内皮生长因子的影响

目的探讨TrkB-BDNF信号通路对神经母细胞瘤(NB)细胞SH-SY5Y分泌血管内皮生长因子(VEGF)的影响。方法 Western blot方法检测全反式维甲酸(ATRA)诱导前后SY5Y细胞TrkB蛋白表达及脑源性神经营养因子(BDNF)刺激后SY5Y细胞磷酸化-TrkB(p-TrkB)蛋白表达;ELISA技术检测ATRA、BDNF、特异性酪氨酸激酶抑制剂K252a及PI3K抑制剂LY294002处理后SY5Y细胞培养上清中VEGF含量。结果 ATRA诱导前,SY5Y细胞中未检测到TrkB蛋白表达;1,10,100 nM/L ATRA处理后,SY5Y细胞中可检测到TrkB蛋白表达,且TrkB蛋白表达水平随ATRA浓度增加逐渐升高,差异有统计学意义。10 nM/L ATRA单独处理组未检测到p-TrkB表达,ATRA+BDNF组可检测p-TrkB蛋白表达。ATRA+BDNF组的VEGF含量明显高于对照组及ATRA组(P<0.01);ATRA+K252a+BDNF组VEGF含量明显低于ATRA+BDNF组(P<0.05);ATRA+LY294002+BD-NF组VEGF含量亦明显低于ATRA+BDNF组(P<0.01)。结论激活TrkB-BDNF信号通路可促进NB细胞合成、分泌VEGF;用K252a阻断TrkB-BDNF信号通路或用LY294002阻断TrkB-BDNF信号下游通路PI3K/Akt均可有效抑制NB细胞合成、分泌VEGF。     

小剂量维甲酸诱导对神经母细胞瘤耐药的影响

目的探讨小剂量维甲酸诱导对神经母细胞瘤(NB)化疗耐药的影响。方法选择人NB细胞株SH SY5Y,用RT PCR方法检测小剂量全反式维甲酸(ATRA)作用下TrkB mRNA水平;通过四甲基偶氮蓝比色(MTT)法及流式细胞仪(FCM)检测ATRA诱导前后顺铂对人NB细胞株SH SY5Y的生长及凋亡的影响。结果SH SY5Y中未检测到TrkB mRNA表达,用1、10、100nM/LATRA诱导5d后可检测到TrkB mRNA表达,且随ATRA浓度增加TrkB mRNA水平逐渐升高。100nM/LATRA诱导7d,TrkB mRNA的相对比值与诱导5d比差异无显著性意义(P>0.05);MTT分析显示:BDNF+顺铂组(无TrkB表达)、ATRA+顺铂组(无BDNF刺激)细胞存活率同单用顺铂组比较无显著性差异(P>0.05);10nM/LATRA+BDNF+顺铂组NB细胞存活率明显高于单用顺铂组(P<0.01);FCM分析显示:ATRA+BDNF+顺铂组NB细胞凋亡率明显低于单用顺铂组(P<0.01)。结论存在BDNF的条件下,小剂量ATRA能阻断顺铂对SH SY5Y的细胞毒性作用,从而使SY5Y细胞对化疗耐药。     

酪氨酸激酶受体B及其配体脑源性神经营养因子水平对神经母细胞瘤耐药的影响

目的 研究酪氨酸激酶受体B（tyrosine kinase receptor,TrkB）及其配体脑源性神经营养因子（brain-derived neurotrophic factor,BDNF）的表达水平对神经母细胞瘤（neuroblastoma,NB）细胞化疗敏感性的影响。方法 Western-blot技术检测不同纳摩尔浓度全反式维甲酸（all trans-retinoic acid,ATRA）诱导后TrkB蛋白水平变化;四甲基偶氮蓝比色（MTT）法检测细胞存活率;流式细胞仪（flow cytometer,FCM）检测细胞凋亡率;透射电镜检测凋亡细胞的形态。结果 （1）不同浓度ATRA（1、10、100nmol／L）处理神经母细胞瘤细胞SY5Y5d,TrkB蛋白水平随ATRA浓度增加而增加;（2）BDNF10ng／ml＋ATRA 10nmol／L＋顺铂（Cisplatin,CP）5μg／ml作用组细胞存活率、凋亡率同单用CP组比较均无显著差异,BDNF（50、100ng／m1）加相同浓度ATRA及CP组细胞存活率均明显高于单用CP组,凋亡率均明显低于单用CP组,BDNF 100ng／ml组存活率高于BDNF 50ng／ml组,凋亡率低于BDNF 50ng／ml组。ATRA 1nmol／L＋BDNF 50ng／ml＋CP 5μg／ml组细胞存活率、凋亡率同单用CP组比较无显著差异,ATRA 10、100 nmol／L加相同浓度BDNF及CP组细胞存活率均明显高于单用CP组,凋亡率均明显低于单用CP组,ATRA 100 1nmol／L组细胞存活率高于ATRA 10nmol／L组,凋亡率低于ATRA 10nmol／L组。（3）透射电镜技术观察到CP作用组可见到较多细胞呈凋亡改变,而ATRA 10nmol／L＋BDNF 50ng／ml＋CP 5μg／ml组细胞形态多数正常。结论 SY5Y对化疗药顺铂的敏感性受TrkB及BDNF水平的影响,二者水平越高越容易产生化疗耐药。     

酪氨酸激酶受体B-脑源性神经营养因子信号传导通路对神经母细胞瘤细胞分泌血管内皮生长因子及基质金属蛋白酶-9的影响

目的 探讨酪氨酸激酶受体B(tyrosine kinase receptor B,TrkB)-脑源性神经营养因子(brain-derived neurotrophic factor,BDNF)信号传导通路对神经母细胞瘤(neuroblastoma,NB)细胞SH-SY5Y分泌血管内皮生长因子(vascular endothelial growth factor,VEGF)及基质金属蛋白酶-9(matrix metalloproteinase-9,MMP-9)的影响.方法 用全反式维甲酸(all-trans retinoic acid,ATRA)诱导SH-SY5Y细胞表达TrkB,加入外源性BDNF,从而激活TrkB-BDNF信号传导通路及其3条下游信号通路.再用特异性酪氨酸激酶抑制剂K252a阻断TrkB-BDNF信号传导通路;用磷脂酰肌醇-3激酶(phosphatidylinositol 3-hydrox y kinase,PBK)抑制剂LY294002、磷脂酶C抑制剂U73122、丝裂原活化蛋白激酶抑制剂U0126分别阻断TrkB-BDNF的3条相应下游信号传导通路.采用酶联免疫吸附法检测细胞培养上清液中VEGF及MMP-9含量.结果 ATRA+ BDNF组VEGF[(485.89±109.99) pg/ml]及MMP-9[(15.73±1.72) pg/ml]含量明显高于对照组及ATRA组(P ＜0.05);ATRA+ BDNF+ K252a组VEGF[(272.42±86.33) pg/ml]及MMP-9[(5.25±1.44) pg/ml]含量明显低于ATRA+ BDNF组(P＜0.05),与对照组及ATRA组比较差异无统计学意义(P＞0.05);ATRA+ BDNF+ LY294002组VEGF[(314.12±24.68) pg/ml]及MMP-9[(4.91±1.08) pg/ml]含量明显低于ATRA+ BDNF组(P＜0.05),与对照组及ATRA组比较差异无统计学意义(P ＞0.05);ATRA+ BDNF+ U73122组VEGF[(444.08±64.49) pg/ml]及MMP-9[(13.28±3.38) pg/ml]含量与ATRA+ BDNF组比较差异无统计学意义(P＞0.05).ATRA+ BDNF+ U0126组VEGF[(429.97±19.95) pg/ml]及MMP-9[(13.96±4.45) pg/ml]含量与ATRA+ BDNF组比较差异无统计学意义(P＞0.05).结论 激活TrkB-BDNF信号传导通路可促进NB细胞合成、分泌VEGF及MMP-9.TrkB-BDNF信号传导通路可能通过进一步激活其下游PI3 K/Akt通路来促进VEGF及MMP-9的合成及分泌,用K252a阻断TrkB-BDNF信号通路、LY294002阻断其下游PI3K通路均可有效抑制NB细胞合成及分泌VEGF及MMP-9.     

苦参碱联合顺铂对SH-SY5Y细胞药物敏感性及TrkB表达的影响

目的探讨不同浓度苦参碱对神经母细胞瘤SH-SY5Y细胞存活及凋亡的影响,及苦参碱降低顺铂化疗耐药性的作用及可能机制。方法分别以全反式维甲酸(ATRA)、脑源性神经生长因子(BDNF)、顺铂、苦参碱处理SH-SY5Y细胞,实验分对照组、ATRA诱导的顺铂干预组、顺铂干预组、苦参碱干预组、苦参碱联合顺铂干预组。应用四甲基偶氮蓝比色法检测苦参碱与顺铂对SH-SY5Y细胞存活率的影响,流式细胞仪检测苦参碱与顺铂对SH-SY5Y细胞凋亡率的影响,Western-blot方法检测SH-SY5Y细胞的p-TrkB表达。结果除ATRA诱导的顺铂干预组外,其余各组SH-SY5Y细胞的存活率及凋亡率与对照组比较,差异均有统计学意义(P<0.05);顺铂干预组与ATRA诱导的顺铂干预组比较,SH-SY5Y细胞的存活率及凋亡率差异有统计学意义(P<0.05);相同浓度的苦参碱干预组与苦参碱联合顺铂干预组比较,SH-SY5Y细胞的存活率及凋亡率差异有统计学意义(P<0.05);苦参碱联合顺铂组与顺铂干预组比较,SH-SY5Y细胞的存活率及凋亡率差异有统计学意义(P<0.05)。苦参碱0.5 mg/ml组与顺铂干预组比较,SH-SY5Y细胞的存活率及凋亡率差异无统计学意义(P>0.05)。各组SH-SY5Y细胞间,p-TrkB的表达水平差异无统计学意义(P>0.05)。结论苦参碱可以抑制SH-SY5Y细胞的增殖并诱导凋亡,从而提高顺铂化疗的敏感性,该作用与TrkB/BDNF信号通路(间)无相关性。     

ATRA诱导神经母细胞瘤细胞分化及TrkB表达的研究

通过对神经母细胞瘤(neuroblastoma，NB)细胞系SMS-KCNR的体外实验，探讨全反式维甲酸(ATRA)对NB细胞增殖抑制的可能分子机制及BDNF(脑源性神经营养因子)-TrkB信号转导途径在NB细胞分化中的作用。通过台盼蓝拒染计数活细胞；用倒置相差显微镜观察加药处理前后细胞形态学变化；通过Northern印迹杂交来分析TrkB基因表达情况的改变。结果：5μM ATRA抑制NB细胞系SMS-KCNR细胞增殖，而5μM ATRA无此作用；ATRA可诱导SMS-KCNR细胞分化成熟；细胞分化过程中伴随TrkB基因表达水平增高。结果显示：5μM ATRA对人NB细胞系MSM-KCNR细胞的体外增殖有抑制作用；ATRA能诱导人NB细胞系SMS-KCNR细胞分化成熟；TrkB基因表达水平的增高可能是ATRA体外诱导NB细胞分化逆转的分子生物学机制之一。     

苦参碱联合顺铂对人肾母细胞瘤SK-NEP-1细胞PDCD4表达的影响

目的探讨苦参碱及苦参碱联合顺铂对人肾母细胞瘤SK—NEP-1细胞存活及凋亡的影响,以及可能的作用机制。方法苦参碱、顺铂单独及联合作用SK-NEP-1细胞,实验分对照组、顺铂干预组、苦参碱干预组、苦参碱联合顺铂干预组。应用四甲基偶氮唑蓝比色法检测SK-NEP-1细胞的存活率,用流式细胞仪检测其凋亡率,逆转录聚合酶链反应法检测其PDCD4mRNA的表达。结果各组SK—NEP-1细胞的存活率及凋亡率与对照组比较、相同浓度的苦参碱干预组与苦参碱联合顺铂干预组比较及苦参碱联合顺铂组与J顿铂干预组比较,SK-NEP-1细胞的存活率及凋亡率差异均有显著性（P〈0．05）。各实验组均能提高PDCD4mRNA的表达,与对照组比较,差异有显著性（P〈0．05）。苦参碱联合顺铂组与苦参碱干预组及顺铂干预组比较,SK—NEP-1细胞PDCD4mRNA表达均显著提高（P〈0．05）。结论苦参碱可浓度依赖性的抑制SK-NEP-1细胞的增殖并诱导其凋亡,从而提高对顺铂化疗的敏感性,该作用可能与提高细胞内PDCD4mRNA的表达有关。     

脑源性神经营养因子对大鼠惊厥性脑损伤的作用及调控因素

目的 观察外源性脑源性神经营养因子(BDNF)、磷酸化cAMP反应元件结合蛋白（pCREB）在活体内对海马BDNF表达的影响及其与神经元凋亡间的关系。方法80只Wistar大鼠，选取40只作为持续惊厥状态（SC）组，制作Wistar鼠SC模型，进一步分为SC-对照亚组（脑室内不注射）、SC-NS亚组（脑室内注射生理盐水）、SC-BDNF亚组（脑室内注射BDNF）和SC-抗pCREB抗体亚组（脑室内注射抗pCREB抗体），每组各10只大鼠。余下40只大鼠作为对照（NC）组，不制备SC模型，进一步分组和处理方法同SC组。采用ELISA检测海马BDNF含量（ pg·μg-1），Annexin V检测海马细胞凋亡。结果①NC-BDNF亚组，注射侧海马BDNF含量为17.24±2.23，明显高于NC-对照亚组5.91±1.63；与NC 对照亚组相比，SC 对照亚组BDNF含量增高，达13.37±5.61。与SC-NS亚组相比，SC-BDNF亚组海马BDNF含量达55.40±4.11，呈显著性增高（P＜0.01)，同时，该侧海马细胞凋亡发生率从（8.36±0.61）%降低至(4.10±1.00)%（P＜0.01)。②NC-抗pCREB抗体亚组注射侧海马BDNF含量为5.94±0.60，与NC 对照亚组差异无统计学意义。与SC-NS亚组（15.77±2.99）相比，SC-抗pCREB抗体亚组注射侧海马BDNF含量急剧下降，为5.53±1.11，并伴有该侧海马细胞凋亡发生率的增加，由（8.36±0.61）%增至（9.37±2.50）% 。③脑室内注射将诱导注射侧海马神经细胞凋亡，而对注射对侧海马影响不大。结论 ①脑室内注射外源性BDNF可影响同侧海马内源性BDNF表达，并对神经元凋亡有一定抑制作用。②选择性阻断CREB的磷酸化，可能通过抑制BDNF的表达，导致神经细胞凋亡。     

脑源性神经营养因子及信号传导通路与缺氧缺血性脑损伤

脑源性神经营养因子(BDNF)是神经营养因子家族中最重要的一员,在神经系统分布广泛.BDNF通过激活酪氨酸受体激酶B(TrkB)及其信号传导通路对神经元的存活、生长、功能、形态和可塑性等起着重要的作用.PI3K/Akt和MAPK/ERK细胞内信号传导通路是BDNF发挥神经保护作用的两条主要途径.近年研究发现,BDNF及其TrkB水平的变化与缺氧缺血性脑损伤(HIBD)的病理生理和治疗机制有着密切的关系.因此,可以通过改变内部或外部条件来增加BDNF的表达,减轻HIBD的损伤.     

脑源性神经营养因子及信号传导通路与缺氧缺血性脑损伤

脑源性神经营养因子(BDNF)是神经营养因子家族中最重要的一员,在神经系统分布广泛.BDNF通过激活酪氨酸受体激酶B(TrkB)及其信号传导通路对神经元的存活、生长、功能、形态和可塑性等起着重要的作用.PI3K/Akt和MAPK/ERK细胞内信号传导通路是BDNF发挥神经保护作用的两条主要途径.近年研究发现,BDNF及...     

Effect of CEP-751 (KT-6587) on neuroblastoma xenografts expressing TrkB

BACKGROUND: The compound CEP-751 (KT-6587), a potent and selective inhibitor of the Trk family of tyrosine kinases, has been shown to inhibit the growth of human neuroblastoma (NB) xenografts in nude mice [1]. PROCEDURE: To address its mechanism of action, we studied SY5Y, a human NB cell line with no detectable Trk expression, and two subclones transfected with TrkB. The transfected clones, SY5Y (G8) and SY5Y (G12), expressed moderate and high levels, respectively, of TrkB mRNA and protein. These TrkB-expressing subclones and the parental line were then grown as xenografts in nude mice, and CEP-751 was used to inhibit TrkB tyrosine kinase activity in these xenografts. Animals were treated twice a day with CEP-751 (21 mg/kg), or with the carrier vehicle as a control. TrkB expression in the resultant tumors was examined by quantitative RT-PCR. The effect of CEP-751 on TrkB activation by BDNF was examined in G12 cells in culture by immunoprecipitation with antipan Trk antiserum, followed by Western blot analysis using antiphosphotyrosine antibodies. To determine if CEP-751 was causing apoptosis, the TUNEL assay was used. RESULTS: CEP-751 had little effect on the growth of SY5Y tumors, but did slow the growth rate of the C8 and G12 tumors. The daily growth rate of the treated tumors was 0.16, 0.13, and 0.10 cm3, respectively, for the SY5Y, G8, and G12 tumors. RT PCR analysis confirmed the expression of TrkB in G8 and G12, but not in SY5Y tumors. Activation of TrkB by BDNF in G12 cells was inhibited by CEP-751 in a dose dependent fashion. The treated tumors showed marked evidence of apoptosis. CONCLUSIONS: These data suggest that the effect of CEP-751 is due, at least in part, to its inhibition of TrkB kinase, and that CEP-751 may become a useful therapeutic tool for the treatment of aggressive neuroblastomas, which often express TrkB.     

ATRA诱导神经母细胞瘤细胞分化及TrkB表达的研究

通过对神经母细胞瘤 (ｎｅｕｒｏｂｌａｓｔｏｍａ,ＮＢ)细胞系ＳＭＳ ＫＣＮＲ的体外实验 ,探讨全反式维甲酸 (ＡＴＲＡ)对ＮＢ细胞增殖抑制的可能分子机制及ＢＤＮＦ(脑源性神经 营养因子 ) ＴｒｋＢ信号转导途径在ＮＢ细胞分化中的作用。通过台盼蓝拒染计数活细胞 ;用倒置相差显微镜观察加药处理前后细胞形态学变化 ;通过Ｎｏｒｔｈｅｒｎ印迹杂交来分析ＴｒｋＢ基因表达情况的改变。结果 :5μＭＡＴＲＡ抑制ＮＢ细胞系ＳＭＳ ＫＣＮＲ细胞增殖 ,而 5ｎＭＡＴＲＡ无此作用 ;ＡＴＲＡ可诱导ＳＭＳ ＫＣＮＲ细胞分化成熟 ;细胞分化过程中伴随ＴｒｋＢ基因表达水平增高。结果显示 :5μＭＡＴＲＡ对人ＮＢ细胞系ＭＳＭ ＫＣＮＲ细胞的体外增殖有抑制作用 ;ＡＴＲＡ能诱导人ＮＢ细胞系ＳＭＳ ＫＣＮＲ细胞分化成熟 ;ＴｒｋＢ基因表达水平的增高可能是ＡＴＲＡ体外诱导ＮＢ细胞分化逆转的分子生物学机制之一。     

Expression of neurotrophin receptor TrkA inhibits angiogenesis in neuroblastoma

BACKGROUND: Mechanisms regulating the expression of angiogenic factors in tumor cells are largely unknown. High expression of the neurotrophin receptor TrkA in neuroblastomas (NB) is associated with favorable prognosis, whereas TrkB is expressed on aggressive, MYCN-amplified NB. PROCEDURE: To investigate the biological effects of TrkA and TrkB expression on angiogenesis in NB, we examined the expression of angiogenic factors in the human NB cell line SY5Y and its TrkA and TrkB transfectants. RESULTS: In comparison to parental SY5Y cells, mRNA and protein levels of angiogenic factors were significantly reduced in SY5Y-TrkA cells, whereas SY5Y-TrkB cells did not demonstrate a significant change. Conditioned medium (CM) of parental SY5Y and SY5Y-TrkB cells induced endothelial cell proliferation, but this effect was completely absent in SY5Y-TrkA cells. TrkA expression also resulted in severely impaired tumorigenicity in a mouse xenograft model, and was associated with reduced angiogenic factor expression and less vascularization of tumors, as determined by immunohistochemistry and an in vivo Matrigel assay.     

Prognostic and biological role of neurotrophin-receptor TrkA and TrkB in neuroblastoma

Expression of different neurotrophin receptors of the tyrosine kinase (Trk) family plays an important role in the biology and clinical behavior of neuroblastomas (NB). Observations from several independent studies suggest that high expression of TrkA is present in NB with favorable biological features and highly correlated with patient survival, whereas TrkB is mainly expressed on unfavorable, aggressive NB with MYCN-amplification. To determine expression of Trk receptors and ligands in primary NB, we developed a reliable semiquantitative duplex RT-PCR protocol, that requires only 1 microgram RNA per tumor sample. Activation of TrkA by its ligand nerve growth factor (NGF) initiates a cascade of signaling events and promotes neuronal differentiation in vitro. Activation of TrkB by its ligand brain derived neurotrophic factor (BDNF) has been associated with proliferation and survival of NB cells. To study Trk signal transduction pathways and their biological effects in NB, we stably expressed TrkA and TrkB cDNA in the human NB cell line SH-SY5Y. Introduction of TrkA and TrkB restored responsiveness of SH-SY5Y cells to the ligands NGF and BDNF, respectively, and resulted in morphological differentiation. Expression of TrkA resulted in growth inhibition of the transfectants compared to parental cells, whereas TrkB transfectants demonstrated an increased proliferation rate. Further insight into the differences of TrkA and TrkB signaling may suggest new options for the treatment of NB. As expression of TrkA is a strong prognostic factor especially in MYCN non-amplified NB, a prospective study of Trk receptor expression using RT-PCR should be performed for German neuroblastoma patients.     

Caspase-8在TRAIL诱导神经母细胞瘤细胞凋亡中的作用

目的：应用干扰素(IFNγ)诱导神经母细胞瘤（neuroblastoma, NB）细胞caspase 8的表达并观察其是否可以恢复NB细胞对肿瘤坏死因子相关凋亡诱导配体（TRAIL）的敏感性。方法：应用RT PCR方法检测IFNγ作用前后NB细胞caspase-8 mRNA的表达;应用Alamar Blue法及流式细胞术检测IFNγ、TRAIL、IFNγ+TRAIL、IFNγ+caspase-8抑制剂zIETD-FMK+TRAIL对NB细胞生长及凋亡的影响;应用比色法测定NB细胞caspase-8相对活性。结果：对TRAIL敏感的CHP212细胞表达caspase-8,且经IFNγ处理后caspase-8 表达水平逐步增加;对TRAIL不敏感的SY5Y细胞不表达caspase-8,IFNγ作用后其caspase-8 mRNA表达明显增加。IFNγ与TRAIL联用对SY5Y细胞有明显诱导凋亡作用。CHP212细胞caspase-8相对活性随TRAIL作用时间的延长逐步升高;IFNγ与TRAIL联合作用的SY5Y细胞caspase-8相对活性明显高于未加药物处理的对照组、IFNγ组、TRAIL组及抑制剂组。结论：表达caspase-8的NB细胞对TRAIL的诱导凋亡作用敏感,TRAIL诱导NB细胞凋亡过程中伴随caspase-8活性的增加。［中国当代儿科杂志,2010,12(11)：902-907］     

神经生长因子受体对神经母细胞瘤血管生成作用的研究(英文)

目的　神经生长因子受体 (TrkA)基因是神经母细胞瘤 (NB)良好预后的标识之一 ,其高表达不仅可以抑制NB增殖和诱导良性分化 ,对NB的血管生长可能有一定的影响。该实验探讨TrkA基因对NB血管生成的作用。方法　 1 5只裸鼠随机分为对照组、空载体组和实验组 (每组 5只 )。利用脂质体转染法将TrkA基因和pBPSTR1空载体转入NBSY5Y细胞 ,分别命名为SY5Y TrkA及SY5Y Vec细胞 ,未转染细胞为SY5Y细胞。将SY5Y ,SY5Y Vec ,SY5Y TrkA细胞分别接种在对照组、空载体组和实验组裸鼠皮下 ,接种 5 0d后处死动物 ,切除肿瘤 ,测量肿瘤体积 ;用RT PCR及免疫组织化学技术检测肿瘤内血管内皮生长因子 (VEGF)的表达 ;计算微血管密度 (MVD)。结果　SY5Y TrkA细胞TrkA表达明显高于SY5Y Vec及SY5Y细胞组 (P <0 .0 1 ) ;实验组肿瘤终体积小于对照组及空载体组 (0 .39± 0 .0 2cm3 vs 1 .74± 0 .4 9cm3 ) ;(0 .39± 0 .0 2cm3 vs 1 .80± 0 .75cm3 ) ,差异有显著性 (均P <0 .0 1 ) ;实验组VEGFmRNA表达低于对照组及空载体组 (0 .1 6± 0 .0 9vs 1 .4 5± 0 .77) ;(0 .1 6± 0 .0 9vs 1 .35± 0 .71 ) ,差异有显著性 (均P <0 .0 1 ) ;实验组VEGF蛋白表达低于对照组及空载体组 (2 .0 0± 0 .6 0vs 5 .6 7± 0 .4 9) ;(2 .0 0± 0 .6 0v     

p75 mediated apoptosis in neuroblastoma cells is inhibited by expression of TrkA

BACKGROUND: Neurotrophins mediate their effects by binding to members of the Trk family of receptor tyrosine kinases and to the low-affinity nerve growth factor receptor p75. Nerve growth factor (NGF) has been demonstrated to support survival and differentiation of neuroblastoma (NB) cells by activation of the TrkA receptor. The p75 receptor belongs to the tumor necrosis factor (TNF) family of death receptors and has been suggested as a receptor that mediates apoptosis in neuronal and NB cells. PROCEDURE: To investigate the effect of p75 expression in NB, we transfected the p75 cDNA into SH-SY5Y cells, an NB cell line lacking expression of both p75 and TrkA. RESULTS: Cell clones expressing elevated levels of p75 showed a high degree of apoptosis even in 10% serum-supplemented medium. Apoptotic signaling by p75 was ligand-independent and only partly caspase-dependent. The level of apoptosis correlated directly with the expression level of the receptor, indicating that p75 may activate the cell death program directly. However, additional transfection of TrkA into SY5Y-p75 cells resulted in a significantly reduced rate of apoptosis even in the absence of NGF. CONCLUSIONS: Thus, expression of the TrkA receptor itself inhibits p75 mediated apoptosis in NB cells.