胶质瘤多药耐药细胞株U251/TMZ的生物学特性

目的探讨胶质瘤U251／替莫唑胺（TMZ）多药耐药细胞株的生物学特性。方法采用TMZ间歇浓度梯度递增法诱导建立胶质瘤多药耐药细胞株U251／TMZ,光镜观察细胞形态,细胞计数计算倍增时间,四甲基偶氮唑蓝法检测耐药指数,流式细胞仪检测细胞周期,逆转录-PCR法检测多药耐药性1（MDRl）、Bcl-2、多药耐药相关蛋白5（MRP5）、肺耐药相关蛋白1（LRPl）等mRNA表达。结果胶质瘤耐药细胞株U251／TMZ对TMZ、依托泊苷、硫酸长春新碱、环磷酰胺、阿霉素的耐药指数分别为4．39、3．61、2．64、2．00、1．63;细胞周期结果显示U251／TMZ细胞系较U251亲本细胞系G0/G1期和s期明显减少（P〈0．05）,GfM期明显增多（P〈0．05）;U251／TMZ倍增时间[（14．64＋1．98）h1较亲本细胞系u251[（10．26＋1．03）h1明显延长（P〈0．05）;U251／TMZ耐药细胞株MDRl、Bcl-2、MRP5、LRPl等mRNA表达均较亲本细胞系U251明显上调。结论间歇TMZ浓度递增法可成功建立人脑胶质瘤U251多药耐药系,MDRl、Bcl-2、MRP5、LRPl的表达明显上调可能与耐药性形成有关。     

恶性胶质瘤耐药细胞通过Beclin1上调自噬抵抗替莫唑胺化疗

目的 分析Beclin 1与临床胶质瘤病理等级和胶质瘤复发间的关系,探讨其在胶质瘤耐药中的作用和机制. 方法 收集南方医科大学珠江医院和南方医院神经外科自2012年4月至2013年4月手术切除的胶质瘤标本53例(WHO分级Ⅰ级7例,复发2例;Ⅱ级9例,复发4例;Ⅲ级11例,复发6例;Ⅳ级9例,复发5例),免疫组化和Western blotting检测胶质瘤标本中Beclin1的表达;体外培养胶质瘤耐药细胞系U251AR和非耐药U251细胞,Western blotting检测细胞中Beclin 1和耐药蛋白P-gP的表达;Western blotting检测双链小分子Beclin 1干扰RNA(siBeclin l)转染U251AR细胞48h后Beclin 1蛋白的表达;CCK8法检测不同浓度替莫唑胺(TMZ)作用U251、U251AR和U251AR-siBeclin 1后细胞活性;Western blotting检测200μmol/L TMZ作用U251、U251AR和U251AR-siBeclin 1 48 h后Capase-3的表达;吖啶橙染色和Western blotting分别检测干扰Beclin 1表达和HCQ对U251AR细胞自噬小体数量和Capase-3表达的影响. 结果 免疫组化染色结果显示Ⅲ、Ⅳ级胶质瘤中Beclin 1阳性细胞数明显高于Ⅰ、Ⅱ级胶质瘤.Western blotting结果显示Ⅳ级、Ⅱ和Ⅲ级、Ⅰ级中Beclin 1的表达依次降低,Ⅲ、Ⅳ级复发肿瘤Beclin 1的表达量明显高于原发肿瘤,差异有统计学意义(P＜0.05); U251AR中Beclin 1和耐药蛋白P-gP的表达量均高于U251细胞.与干扰对照组和空白对照组比较,转染siBeclin 1 48 h后干扰组Beclin 1蛋白的水平明显下降;在含TMZ(50,100,500和1000 μmol/L)培养基中培养24 h后,U251AR细胞存活率明显高于U251和si-Bec1-U251AR细胞,差异有统计学意义(P＜0.05).200 μmol/L TMZ作用48 h后,U251细胞凋亡蛋白Caspase-3的表达量明显高于U251AR和si-Bec l-U251AR细胞.吖啶橙染色显示在TMZ培养U251AR 48 h后,HCQ和Beclin 1干扰都导致自噬小体形成明显减少,Caspase-3的表达增高,差异有统计学意义(P＜0.05). 结论 Beclin 1与胶质瘤恶性程度、复发和耐药相关,可能用于胶质瘤恶性诊断和预后评估.Beclin 1在胶质瘤中的耐药功能可能是通过自噬实现的,联合运用TMZ和自噬抑制剂或Beclin 1干扰剂有助于胶质瘤的治疗.     

表皮生长因子受体拮抗剂靶向抑制胶质瘤细胞增殖的实验研究

目的探讨表皮生长因子受体(EGFR)拮抗剂-吉非替尼对人脑胶质瘤细胞的增殖抑制作用,为胶质瘤干细胞靶向治疗研究作准备。方法荧光定量PCR检测人脑胶质瘤细胞U251、GBM、SHG44及神经干细胞、脑肿瘤干细胞中EG-FR基因的表达。选择不同浓度的吉非替尼作用于U251细胞48h,MTT法检测药物对细胞的抑制率;流式细胞仪分析吉非替尼作用U251细胞后细胞增殖周期和细胞凋亡比率的变化。结果U251和脑肿瘤干细胞中都高表达EGFR。吉非替尼对U251细胞有明显的抑制作用,并呈浓度依赖性,IC50为19.0μM。以12.7μM、19.0μM和25.3μM吉非替尼处理U251细胞,随着药物浓度的增加,G0-G1期细胞比例和细胞凋亡率都逐渐升高。结论EGFR在U251细胞和脑肿瘤干细胞中都高表达,其拮抗剂吉非替尼对U251的细胞增殖有显著的抑制作用,为靶向治疗胶质瘤干细胞的研究开拓了思路。     

过表达TBX2对胶质瘤细胞增殖和侵袭的影响

目的 探讨TBX2表达对胶质瘤细胞增殖、侵袭的影响。方法 采用RT-qPCR和免疫印迹法检测53例胶质瘤组织和瘤旁组织TBX2mRNA和蛋白表达水平。体外培养胶质瘤细胞（U251、U87和SHG-44）和正常星型胶质细胞（HA1800）,采用RT-qPCR和免疫印迹法检测细胞TBX2 mRNA和蛋白表达水平。构建TBX2过表达或低表达U251细胞株,分别采用WST-1法检测胶质瘤细胞增殖能力,Transwell实验检测细胞侵袭能力。结果 胶质瘤组织TBX2 mRNA和蛋白表达水平明显高于瘤旁组织（P<0.05）,而且,高级别胶质瘤TBX2表达水平显著高于低级别胶质瘤（P<0.05）。相比于人正常星型胶质细胞系HA1800,胶质瘤细胞系U251、U87、SHG-44细胞TBX2 mRNA和蛋白表达水平均明显增高（P<0.05）;而且,U251细胞TBX2表达水平显著高于U87和SHG-44细胞（P<0.05）,因此使用U251细胞进行后续实验。过表达TBX2显著增加U251细胞增殖和侵袭能力（P<0.05）,低表达TBX2显著抑制U251细胞增殖和侵袭能力（P<0.05）。结论 胶质瘤TBX2呈高表达,与胶质瘤增殖、侵袭能力有关。     

下调RNF138基因对胶质瘤细胞株U251增殖、凋亡及细胞周期影响的研究

目的探讨RNA干扰下调胶质瘤细胞株高表达基因RNF138对胶质瘤细胞株U251体外增殖、凋亡以及细胞周期的影响。方法构建下调RNF138基因的siRNA,通过慢病毒转染导入胶质瘤细胞株U251,设立阴性干扰对照组及空白对照组,荧光显微镜观察转染效率;实时荧光定量PCR检测敲减效率;运用Cellomics仪器连续检测U251体外增殖情况;流式细胞仪检测U251凋亡及细胞周期变化情况。结果慢病毒载体高效、稳定转染U251细胞,靶向RNF138的siRNA有效抑制RNF138基因表达,使RNF138mRNA表达减少60%,U251体外增殖明显减缓,凋亡明显增加,细胞阻滞在G2/M期。结论 RNA干扰抑制RNF138基因表达可以明显抑制胶质瘤细胞株U251体外增殖,促进其凋亡,影响细胞周期,阻滞细胞分裂。     

shRNA干扰Survivin基因后胶质瘤细胞中Survinvin及mcm2的表达及意义

目的观察小发夹状RNA(shRNA)干扰生存素(Survivin)对脑胶质瘤细胞株U251中Survivin及微小染色体维持蛋白2(MCM2)表达的影响。方法通过脂质体介导对脑胶质瘤细胞株U251、转染Survivin shRNA质粒PG-sur(p Genesil-Suvrivin)及无意义shRNA质粒PG,采用RT-PCR、Western-blot分别对未转染组(U251)、转染无意义序列组(U251-PG)及转染干扰序列组(U251-sur)检测Survivin的mRNA及蛋白表达情况,流式细胞术(FCM)定量测定各组细胞的细胞周期和细胞凋亡,MTT检测细胞增殖能力。采用RT-PCR、Western-blot分别检测转染前后细胞MCM2的mRNA和蛋白的表达情况。结果与其他两组比较,转染干扰序列组细胞Survivin基因的mRNA及蛋白表达抑制效果显著,细胞增殖能力降低,细胞周期G2/M期阻滞显著,细胞凋亡率升高(p<0.05)。MCM2的mRNA和蛋白表达显著降低。结论靶向Survivin基因的特异性shRNA能够在体外明显抑制U251细胞的生长并诱导其发生凋亡及细胞周期阻滞。且本试验结果表明MCM2是一可靠的细胞增殖标记物,且与Survivin之间不是各自孤的,两者间可能起协同作用共同参与胶质瘤的发生。     

胶质瘤细胞系T98G、U87和U251中CYP17A1的表达及意义

目的探讨细胞色素P450c17a酶(CYP17A1)在人神经胶质瘤细胞系T98G、U87和U251中的表达情况。方法采用Western blot和实时荧光定量PCR于蛋白质水平和mRNA水平检测细胞色素P450c17a酶(CYP17A1)在三种人胶质瘤细胞系中的表达。结果 Western blot检测出CYP17A1蛋白在胶质瘤细胞系T98G、U251和U87中的相对表达量为0.518±0.052、0.460±0.034和0.142±0.025。T98G和U251的CYP17A1蛋白表达水平明显高于U87,差异有统计学意义(P0.05)。实时荧光定量PCR检测结果显示CYP17A1的mRNA在T98G、U251和U87中相对转录水平为1.000±0.122、0.960±0.079、0.611±0.045,T98G和U251细胞中CYP17A1的mRNA转录水平均高于U87,差异有统计学意义(P0.05)。同时Western blot和实时荧光定量PCR都指出T98G和U251在CYP17A1在蛋白和mRNA的表达上无统计学差异(P0.05)。结论人胶质瘤细胞系T98G和U251中CYP17A1的表达量较高,这两种细胞系可作为良好的细胞模型用来研究CYP17A1在胶质瘤中的作用机制以及以CYP17A1为靶点的肿瘤治疗等。     

Evi1基因对胶质瘤细胞株U87/U251增殖、侵袭的影响

目的探讨Evi1基因在不同级别胶质瘤组织中的表达,以及调控该基因对胶质瘤细胞株U87和U251细胞增殖、细胞周期和侵袭影响,为靶向癌基因治疗胶质瘤提供客观依据。方法首先通过实时定量PCR(qRT-PCR)分别检测人脑不同级别胶质瘤组织以及U87和U251细胞株中Evil基因的表达水平。用合成的小分子干扰RNA(small interfering RNA,siRNA)干扰下调U87和U251细胞Evi1基因表达作为干扰组,同时设空白和阴性对照组。qRT-PCR检测转染前后Evi1基因在U87和U251细胞中的表达和转染效率。CCK-8法检测实验组细胞的增殖能力,流式细胞仪分析Flow Cytometer(FCM)其细胞周期。Transwell以及划痕试验检测各组U87和U251的侵袭和迁移能力。以及用qRT-PCR分析下调Evi1基因后U87和U251细胞基质金属蛋白酶2(MMP2)的表达水平。结果 Evi1基因在胶质瘤组织中呈现高表达,且随着胶质瘤级别程度增加其表达水平亦上升,其中Ⅲ和Ⅳ级的胶质瘤组织以及U87、U251细胞Evi1基因表达明显高于非瘤脑组织(均P0.05)。通过siRNA下调Evi1基因后,胶质瘤细胞株U87和U251的增殖减缓(均P0.05),其侵袭和迁移能力明显下降(均P0.01),并能阻滞其细胞周期G1期(P0.05)。干扰组U87和U251细胞MMP2表达水平明显降低(均P0.01)。结论 Evi1基因在胶质瘤中呈高表达,干扰U87和U251细胞Evi1基因可抑制胶质瘤的增殖和侵袭。     

长链非编码RNA SNORD3A在脑胶质瘤中的表达变化及功能研究

目的探讨长链非编码(lncRNA)SNORD3A在胶质瘤组织和胶质瘤细胞系中的表达变化,以及对胶质瘤细胞增殖和侵袭能力的影响。方法采用生物信息学方法分析美国国家生物技术信息中心(NCBI)GEO数据库收录的GSE58276中差异表达的lncRNA,采集2017年6月至2019年8月手术切除的胶质瘤组织标本30例,实时荧光定量聚合酶链反应(PCR)检测lncRNA SNORD3A表达水平;小干扰RNA转染胶质瘤细胞系T98G和U251,CCK-8细胞增殖实验检测胶质瘤细胞增殖能力、Transwell细胞侵袭实验检测胶质瘤细胞侵袭能力、Western blotting法检测胶质瘤细胞c-Myc mRNA和蛋白表达变化。结果与对照组相比,胶质瘤组织lncRNA SNORD3A表达水平升高(P=0.000);与HEB细胞相比,胶质瘤细胞系T98G、U87、U251和U373 lncRNA SNORD3A表达升高(均P 0.05)。si-SNORD3A-1组和si-SNORD3A-2组T98G细胞(P=0.001,0.007)和U251细胞(P=0.002,0.009)lncRNA SNORD3A表达水平低于对照组;转染后24、48和72 h,si-SNORD3A-1组和si-SNORD3A-2组T98G细胞(均P=0.000)和U251细胞(均P=0.000)增殖能力低于对照组;转染后48 h,si-SNORD3A-1组和si-SNORD3A-2组穿过小室的T98G和U251细胞数目少于对照组(均P=0.000)、c-Myc mRNA和蛋白表达水平低于对照组(均P 0.01)。结论 lncRNA SNORD3A可能通过靶向c-Myc蛋白促进T98G和U251细胞的增殖和侵袭。     

胶质瘤细胞系A172、U251、U87和SHG-44中HER2的表达及意义

目的 探讨人表皮生长因子受体2(HER2)在人神经胶质瘤细胞系A172、U251、U87和SHG-44中的表达情况.方法 采用Western blot 和流式细胞术(FCM)于蛋白质水平检测HER2在四种人胶质瘤细胞系中的表达.结果 Western blot检测出HER2在人胶质瘤细胞系A172中的表达量最高,U251次之,U87和SHG-44表达量较低.FCM检测结果显示HER2在A172、U251、U87和SHG-44中的阳性率分别为36.5%、21.5%、3.3%和3.5%.结论 人胶质瘤细胞系A172和U251中HER2的表达量较高,这两种细胞系可作为良好的细胞模型来研究HER2分子在胶质瘤中的作用机制以及以HER2为靶点的生物治疗等.     

Pediatric glioblastoma cell line shows different patterns of expression of transmembrane ABC transporters after in vitro exposure to vinblastine

Background  Resistance to drug is a major cause of treatment failure in pediatric brain cancer. The multidrug resistance (MDR) phenotype can be mediated by the superfamily of adenosine triphosphate-binding cassette (ABC) transporters. The dynamics of expression of the MDR genes after exposure to chemotherapy, especially the comparison between pediatric brain tumors of different histology, is poorly described. Objective  To compare the expression profiles of the multidrug resistance genes ABCB1, ABCC1, and ABCG2 in different neuroepithelial pediatric brain tumor cell lines prior and following short-term culture with vinblastine. Methods  Immortalized lineages from pilocytic astrocytoma (R286), anaplasic astrocytoma (UW467), glioblastoma (SF188), and medulloblastoma (UW3) were exposed to vinblastine sulphate at different schedules (10 and 60 nM for 24 and 72 h). Relative amounts of mRNA expression were analyzed by real-time quantitative polymerase chain reaction. Protein expression was assessed by immunohistochemistry for ABCB1, ABCC1, and ABCG2. Results  mRNA expression of ABCB1 increased together with augmenting concentration and time of exposure to vinblastine for R286, UW467, and UW3 cell lines. Interestingly, ABCB1 levels of expression diminished in SF188. Following chemotherapy, mRNA expression of ABCC1 decreased in all cell lines other than glioblastoma. ABCG2 expression was influenced by vinblastine only for UW3. The mRNA levels showed consistent association to protein expression in the selected sets of cell lines analyzed. Conclusions  The pediatric glioblastoma cell line SF188 shows different pattern of expression of multidrug resistance genes when exposed to vinblastine. These preliminary findings may be useful in determining novel strategies of treatment for neuroepithelial pediatric brain tumors. Financial support: FAPESP (grant 2007/04065-9).     

The "Specific" P-Glycoprotein Inhibitor Tariquidar Is Also a Substrate and an Inhibitor for Breast Cancer Resistance Protein (BCRP/ABCG2)

Tariquidar was developed as a specific inhibitor of the efflux transporter ABCB1. Recent positron emission tomographic brain imaging studies using [(11)C]tariquidar to measure ABCB1 (P-gp, P-glycoprotein) density in mice indicate that the inhibitor may not be as specific as previously thought. We examined its selectivity as an inhibitor and a substrate for the human transporters P-gp, breast cancer resistance protein (BCRP, ABCG2), and multidrug resistance protein 1 (MRP1, ABCC1). Our results show that at low concentrations, tariquidar acts selectively as an inhibitor of P-gp and also as a substrate of BCRP. At much higher concentrations (≥100 nM), tariquidar acts as an inhibitor of both P-gp and BCRP. Thus, the in vivo specificity of tariquidar depends on concentration and the relative density and capacity of P-gp vs BCRP.     

Distribution and functional activity of P-glycoprotein and multidrug resistance-associated proteins in human brain microvascular endothelial cells in hippocampal sclerosis

Multidrug resistance protein, also referred as P-glycoprotein (P-gp, MDR1; ABCB1) and multidrug resistance-associated protein (MRP) 1 (ABCC1) and 2 (ABCC2) are, thus far, candidates to cause antiepileptic drug (AED) resistance epilepsy. In this study, we investigated P-gp, MRP1 and MRP2 expression, localization and functional activity on cryosections and isolated human brain-derived microvascular endothelial cells (HBMEC) from epileptic patients (HBMEC-EPI) with hippocampal sclerosis (HS), as compared with HBMEC isolated from normal brain cortex (HBMEC-CTR). We examined the expression and distribution of three transporters, P-gp, MRP1 and MRP2 on two major parts of the resected tissue, the hippocampus and the parahippocampal gyrus (Gph). P-gp showed diffuse expression not only in endothelium but also by parenchymal cells in both the hippocampus and the Gph. MRP1 labeling was observed in parenchymal cells in the Gph. By contrast, MRP2 was mainly found in endothelium of the hippocampus. P-gp and MRP1 expression in the Gph was relatively high in the patient with long-term seizure history. Quantitative RT-PCR analysis of HBMEC revealed that MDR1, MRP1 as well as MRP5 (ABCC5) and MRP6 (ABCC6) were overexpressed in HBMEC-EPI at the mRNA level. HBMEC from both normal and epilepsy groups displayed protein expression of P-gp, whereas MRP1 and MRP2 were seen only in HBMEC-EPI. Accordingly, it is of particular interest that MRP functional activities were observed in HBMEC-EPI, but not in HBMEC-CTR. Our results suggest that complex MDR expression changes not only in the hippocampus but in the Gph may play a role in AED pharmacoresistance in intractable epilepsy patients with mesial temporal lobe epilepsy (MTLE) by altering the permeability of AEDs across the blood-brain barrier (BBB).     

Reversion of multidrug resistance in human glioma by RNA interference

OBJECTIVE: To explore whether the vector construction of short hairpin in vivo could make human glioma cell line BT325 produce RNA interference (RNAi) duplexes and reverse the expression of the MDR1 gene. METHODS: Three 62nt oligonucleotide fragments (shRNA) were constructed according to GeneBank MDR1 sequence and were cloned to the retrovirus-delivered vectors. After these vectors were transfected directly to the BT325 cell by Lipofectamine 2000 with enhanced green fluorescent protein (EGFP) co-transfection, the MDR1 gene silence effects were detected by the changing levels of mRNA and P-glycoprotein (P-gp) including real-time PCR (RT-PCR), Northern blot and Western blot analysis. For assessing multidrug resistance against doxorubicin (DOX) and vincristine (VCR), cell proliferation assays were performed by cell counting kit-8 and IC50 was calculated. RESULTS: The RNAi plasmid vectors were constructed successfully. The gene silence became the strongest after 48 hour transfection from Northern blot; Western blot analysis demonstrated that P-gp expression reduced to 12.9, 30.3 and 4.8%. The chemosensitivity assays showed that the transfected cell could increase the sensitivity of DOX and VCR. Based on the value of IC50, BT325 cells increased sensitivity to drugs obviously. The sequence specific RNAi could inhibit MDR1 mRNA and P-gp expression of the glioma cell line. And it may reverse multidrug resistance phenotype, which may provide promising therapeutic modalities in the treatment of human glioma.     

神经胶质瘤C6/VP16多药耐药细胞株的建立

目的建立神经胶质瘤C6细胞对依托泊苷(VP16)耐药细胞株C6/VP16,探讨其耐药的可能机制。方法采用浓度递增和短期大剂量药物诱导相结合的方法建立大鼠C6/VP16耐药细胞株;光镜下观察C6/VP16细胞株的形态学变化;细胞计数试剂盒-8检测C6/VP16细胞株对VP16、阿霉素(ADM)、长春新碱(VCR)、环磷酰胺(CTX)、替莫唑胺(TMZ)的耐药敏感性;westernblot检测多药耐药相关蛋白1(MRP1)的表达量变化。结果经过65代诱导培养,成功建立可操作的、重复性好的C6/VP16耐药细胞株。C6亲代细胞形态规则、大小均一,生长迅速,紧密生长,每2～3d传代;C6/VP16细胞株,突起增多,生长周期受抑制,生长变缓,每10～12d传代。VP16、TMZ、CTX、ADM和VCR作用C6亲代细胞的半生长抑制浓度(IC50)分别为(0.105±0.043)、(27.284±0.529)、(5.800±0.317)、(6.636±0.315)和(19.146±0.526)μg/ml,而作用C6/VP16细胞株的IC50分别为(0.943±0.052)、(33.251±0.288)、(32.943±0.215)、(35.251±0.126)和(35.604±0.426)μg/ml;VP16、CTX和ADM作用C6/VP16细胞株IC50较C6亲代细胞差异显著(P<0.05)。C6/VP16细胞株MRP1的表达量较亲代C6细胞明显增加(P<0.05)。结论 C6/VP16细胞株对ADM和CTX存在明显交叉耐药,而对TMZ和VCR无明显交叉耐药;多药耐药性是多种机制相互作用的结果,MRP1可能参与其中。     

sLRIG1与胶质瘤耐药细胞株化疗敏感性的关系

目的 探讨可溶性多亮氨酸重复区免疫球蛋白样蛋白1（sLRIG1）与胶质瘤耐药细胞株化疗敏感性之间的关系。方法 浓度梯度递增法建立多药耐药细胞株U251/VP16;CCK-8法检测sLRIG1对U251细胞的抑制率,确定sLRIG1对U251细胞的最佳作用时间及适宜浓度;CCK-8法检测加入sLRIG1前后三种化疗药（依托泊苷、硫酸长春新碱、替莫唑胺）作用于U251/VP16的抑制率变化。结果 成功建立多药耐药细胞株U251/VP16;sLRIG1对U251细胞的最佳作用时间为30 min,适宜浓度范围为100~200 ng/ml;sLRIG1对U251/VP16的抑制率为（23.76±0.02）%;依托泊苷、硫酸长春新碱、替莫唑胺对U251/VP16的抑制率分别为（9.79±0.08）%、（16.71±0.06）%、（27.14±0.09）%;而在加入sLRIG1后抑制率则分别为（20.34±0.03）%、（31.52±0.07）%、（35.21±0.05）%,加入sLRIG1前后三种化疗药的抑制率差异均有统计学意义（P<0.05）。结论 sLRIG1不仅自身能抑制胶质瘤细胞生长,对耐药胶质瘤细胞的化疗也有增敏作用。     

Membrane transporter proteins: a challenge for CNS drug development

Drug transporters are membrane proteins present in various tissues such as the lymphocytes, intestine, liver, kidney, testis, placenta, and central nervous system. These transporters play a significant role in drug absorption and distribution to organic systems, particularly if the organs are protected by blood-organ barriers, such as the blood-brain barrier or the maternal-fetal barrier. In contrast to neurotransmitters and receptor-coupled transporters or other modes of interneuronal transmission, drug transporters are not directly involved in specific neuronal functions, but provide global protection to the central nervous system. The lack of capillary fenestration, the low pinocytic activity and the tight junctions between brain capillary and choroid plexus endothelial cells represent further gatekeepers limiting the entrance of endogenous and exogenous compounds into the central nervous system. Drug transport is a result of the concerted action of efflux and influx pumps (transporters) located both in the basolateral and apical membranes of brain capillary and choroid plexus endothelial cells. By regulating efflux and influx of endogenous or exogenous substances, the blood-brain barrier and, to a lesser extent the blood-cerebrospinal barrier in the ventricles, represents the main interface between the central nervous system and the blood, i.e., the rest of the body. As drug distribution to organs is dependent on the affinity of a substrate for a specific transport system, membrane transporter proteins are increasingly recognized as a key determinant of drug disposition. Many drug transporters are members of the adenosine triphosphate (ATP)-binding cassette (ABC) transporter superfamily or the solute-linked carrier (SLC) class. The multidrug resistance protein MDR1 (ABCB1), also called P-glycoprotein, the multidrug resistance-associated proteins MRP1 (ABCC1) and MRP2 (ABCC2), and the breast cancer-resistance protein BCRP (ABCG2) are ATP-dependent efflux transporters expressed in the blood-brain barrier They belong to the superfamily of ABC transporters, which export drugs from the intracellular to the extracellular milieu. Members of the SLC class of solute carriers include, for example, organic ion transporting peptides, organic cation transporters, and organic ion transporters. They are ATP-independent polypeptides principally expressed at the basolateral membrane of brain capillary and choroid plexus endothelial cells that also mediate drug transport through central nervous system barriers.     

miR-21调控人脑胶质瘤细胞侵袭能力的体外研究

目的 探讨miR-21调控人脑胶质瘤细胞侵袭能力的体外机制.方法 脂质体介导反义miR-21(AS-miR-21)转染体外常规培养的U251细胞,同时设无义寡脱氧核苷酸(ODN)组和对照组.测定荧光素酶活性验证3组细胞中miR-21的表达,Matrigel基质生长实验检测U251细胞的生长情况,Transwell细胞体外迁移实验检测U251细胞的迁移能力,Western blotting检测细胞侵袭相关蛋白局部粘着斑激酶(FAK)、基质金属蛋白酶9/2(MMP-9/2)、人基质金属蛋白酶抑制因子1(TIMP-1)、微管蛋白α(Tubulin-α)的表达,免疫荧光检测细胞Tubulin-α蛋白的形态. 结果 与对照组和无义ODN组比较,转染AS-miR-21组U251细胞miR-21表达水平降低,Matrigel基质生长实验显示转染AS-miR-21组U251细胞体外培养克隆平均直径较小,Transwell细胞体外迁移实验显示转染AS-miR-21组穿膜细胞数较少,Western blotting结果 显示转染AS-miR-21组U251细胞FAK、MMP-9/2表达较低,TIMP-1表达较高,差异均有统计学意义(P＜0.05).Tubulin-α的表达无明显变化,免疫荧光染色显示转染AS-miR-21组Tubulin-α蛋白形态扭曲. 结论 miR-21高表达可以促进U251胶质瘤细胞侵袭生长,提示miR-21可以作为基因治疗脑胶质瘤的候选靶点.