乙型肝炎病毒X蛋白抑制p16蛋白表达及其促进HepG2肝癌细胞生长

目的 探讨乙型肝炎病毒X蛋白(HBx)对肝癌细胞生长的影响及其机制.方法 以HepG2细胞和稳定表达GFP/HBx融合蛋白的HepG2/GFP-HBx为实验细胞,四甲基偶氮唑盐(MTT)法检测细胞吸光度值A490,分析细胞生长增殖;流式细胞术检测细胞周期;甲基化PCR检测细胞p16INK4A基因的甲基化;Western blot检测p16蛋白表达水平. 结果 72 h时HepG2/GFP-HBx细胞组的A490为3.225±0.038,分别与HepG2和HepG2-GFP细胞组的2.012±0.022、2.038±0.029比较,增殖能力明显增强,t值分别为46.86和42.51,P值均＜0.001,差异均有统计学意义.流式细胞术检测示HepG2/GFP-HBx细胞组的G0/G1期细胞占16.45％±0.45％,明显低于HepG2和HepG2/GFP细胞组的44.81％±1.36％、42.76％±1.58％,t值分别为-34.22和-28.88,P值均＜ 0.001,差异均有统计学意义.而5-氮-2 '-脱氧胞苷(5-Aza-CdR)处理的HepG2/GFP-HBx细胞G0/G1期细胞比例为33.25％±0.79％,较未处理HepG2/GFP-HBx细胞组的16.45％±0.45％显著增加,两组比较,t=31.85,P＜0.001,差异有统计学意义.甲基化PCR检测显示HepG2/GFP-HBx细胞组发生了p16INK4A基因甲基化,而HepG2和HepG2-GFP细胞组及5-Aza-CdR处理的HepG2/GFP-HBx细胞组未检测到p16INK4A基因启动子甲基化.Western blot检测示HepG2/GFP-HBx细胞组p16蛋白水平低于HepG2和HepG2/GFP细胞组,而5-Aza-CdR处理HepG2/GFP-HBx细胞后,p16蛋白水平高于未处理的HepG2/GFP-HBx细胞. 结论 HBx蛋白可通过缩短HepG2细胞生长的G0/G1期而加快细胞周期进程,从而促进肝癌细胞生长增殖,其机制可能与HBx蛋白诱导p16INK4A基因启动子甲基化及抑制p16蛋白表达有关.     

HBx基因下调p21对HepG2细胞增殖与凋亡的影响

目的:构建转基因细胞模型HepG2/HBx,观察HBx基因对HepG2细胞增殖、周期和凋亡的影响, 探讨细胞周期蛋白P21在其中的作用和意义.方法:应用脂质体转染和G418筛选构建稳定表达HBx的转基因细胞HepG2/HBx,RT-PCR和Western blot鉴定HBx mRNA与蛋白的表达.分别以四唑蓝(MTT)比色法、流式细胞术检测HepG2/HBx细胞及对照组HepG2与HepG2/pcDNA3.1细胞(转染空载体pcDNA3.1的HepG2细胞)的增殖、周期和凋亡.另半定量RT-PCR检测各组细胞中细胞周期蛋白P21与抑癌基因p53mRNA的表达.结果:HepG2/HBx细胞中有HBx mRNA和蛋白的表达.HepG2/HBx细胞生长速度加快.HepG2/HBx中G0/G1期细胞比例较对照组显著减少(43.34%±3.11%vs57.69±4.28%,P<0.01),S期细胞比例明显增加(28.69%±1.17%vs22.41%±1.99%,P<0.05),同时还发现与对照组相比其凋亡率也显著降低(1.19%±0.06%vs 5.43%±0.42%, P<0.001).细胞周期蛋白p21 mRNA在HepG2/HBx细胞中的表达较对照组细胞显著降低(0.16±0.05vs0.78±0.15,P<0.001),而p53表达则无显著变化.结论:HBx基因可下调细胞周期蛋白P21mRNA的表达,可能参与HBx基因加速HepG2细胞周期进程、促进细胞增殖以及抑制细胞凋亡的作用.     

反义细胞周期素D1基因对肝癌细胞株HepG2的作用

目的通过基因反义封闭技术体外抑制细胞周期素D1(cyclin D1)的表达,研究其对肝癌细胞cyclin D1蛋白表达和细胞增殖的影响。方法以肝癌细胞株HepG2为研究对象,通过转染可表达cyclin D1反义互补脱氧核苷酸(AScDNA)的质粒后,观察cyclin D1反义cDNA对HepG2细胞cyclin D1基因表达及体外增殖活性的影响。结果四甲基偶氮唑盐法检测细胞增殖活性显示转染表达反义cyclin D1的质粒后, HepG2细胞的增殖受到抑制,抑制作用在48 h左右最强;逆转录聚合酶链反应检测显示cyclin D1 mRNA基因的表达明显被抑制;免疫组织化学检测结果显示cyclin D1蛋白表达明显降低; 流式细胞仪检测结果显示G0/G1期的细胞比例增高,G2+M和S期的细胞比例下降,HepG2细胞周期在G1期被阻滞。结论cyclin D1反义cDNA可以特异性的抑制肝癌HepG2细胞株cyclin D1蛋白的表达,从而调控细胞周期,抑制肝癌细胞增殖。利用cyclin D1反义cDNA进行细胞周期调控对于肝细胞癌的生物治疗具有一定的应用前景。     

细粒棘球蚴囊液对HepG2细胞增殖的影响

目的 探讨细粒棘球蚴囊液(HCF)对宿主肝细胞丝裂原活化蛋白激酶信号通路及细胞周期的影响.方法 四甲基偶氮唑盐法检测不同浓度HCF对HepG2细胞的增殖作用.流式细胞仪检测细胞周期.Western blot法检测磷酸化细胞外信号调节激酶(p-ERK)、增殖细胞核抗原(PCNA)、细胞周期蛋白(cyclin) D1、cyclin A、cyclin B1、cyclin E的表达水平.对数据采用重复测量方差分析.结果 在48、72h和96h,15％、30％和60％ HCF组与无胎牛血清比较,能明显促进HepG2细胞的增殖(P值均＜ 0.05).Western blot检测结果显示:15％HCF组p-ERK在48h高表达(F=1.916,P＜ 0.01),cyclin D1在24h高表达(F=3.901,P＜0.01),15％、30％HCF组PCNA分别在48h、72h高表达(F=91.140,P＜0.01),cyclin A分别在48h、72h高表达(F=18.587,P＜0.01),cyclin B1分别在48h、72h高表达(F=2.064,P＜0.01),30％ HCF组cyclin E在96h高表达(F=1.068,P＜0.01).结论 HCF对体外培养的HepG2细胞无毒害作用,对其增殖有一定促进作用.     

PHB1对人肝癌细胞增殖的影响及其作用机制

目的探讨抗增殖蛋白1(prohibitin1,PHB1)对人肝癌细胞增殖的影响及其作用机制。方法构建PHB1真核表达重组质粒(pEGFP-PHB1)和PHB1靶向siRNA质粒(shRNA-PHB1)转染人肝癌细胞HepG2和SMMC-7721,诱导PHB1在人肝癌细胞中表达上调和下调,采用MTT、流式细胞学、荧光定量PCR和免疫印迹等技术检测人肝癌细胞增殖、细胞周期,以及细胞周期关键调控分子的表达情况。结果高表达PHB1可阻滞HepG2和SMMC-7721细胞于G0/G1期[(67.28±2.94)%比(56.71±2.56)%,t=6.64,P=0.00;(69.48±3.82)%比(60.43±2.59)%,t=4.80,P=0.00],使S期比例下降[(14.74±1.45)%比(24.13±1.92)%,t=9.54,P=0.00;(13.73±1.26)%比(25.50±2.30)%,t=10.99,P=0.00],抑制细胞增殖;周期调控分子p53和p21CIP1mRNA和蛋白质水平显著升高,而Cyclin A2、Cyclin E1和CDK2 mRNA和蛋白质水平显著降低(P0.01)。低表达PHB1可促使HepG2和SMMC-7721细胞趋于S期[(31.65±2.71)%比(24.68±1.28)%,t=5.69,P=0.00;(31.02±2.49)%比(25.88±2.40)%,t=3.64,P=0.005],促进细胞增殖;p53、p21CIP1、Cyclin A2、Cyclin E1、CDK2 mRNA和蛋白质水平与PHB1高表达时相反(P0.01)。结论高表达PHB1可以阻滞人肝癌细胞周期于G0/G1期,进而抑制细胞增殖,其作用机制可能与p53介导的G0/G1期相关细胞周期蛋白有关。     

氧化苦参碱对人结肠癌细胞株SW1116细胞周期通路相关调控因子的影响

背景：氧化苦参碱为中药苦参的主要有效成分，研究显示其对结肠癌细胞具有杀伤作用。目的：观察氧化苦参碱对人结肠癌细胞株SW1116细胞周期通路相关调控因子的影响，阐明其抗结肠癌作用的分子机制。方法：分别以2、3、4mg／m1氧化苦参碱干预SW1116细胞24h或48h，以流式细胞仪检测细胞周期，以逆转录聚合酶链反应（RTPCR）和蛋白质印迹法检测细胞周期蛋白（cyclin）D1、细胞周期蛋白依赖性激酶4（CDK4）、CDK抑制剂p53、核转录岗子E2F1和S期激酶相关蛋白2（Skp2）mRNA和蛋白水平的表达。结果：氧化苦参碱干预可使SW1116细胞周期阻滞于G0／G1期，cyc1inD1、CDK4、E2F1和Skp2mRNA和蛋白表达显著下降，p53mRNA和蛋白表达显著上升，作用呈剂量和时间依赖性（P〈0．05）。结论：氧化苦参碱可通过影响细胞周期相关通路以抑制人结肠癌细胞增殖。     

辛伐他汀抑制血管平滑肌细胞增殖及对PTEN、p27蛋白表达的影响

目的：观察辛伐他汀（simvastatin）对血管平滑肌细胞（VSMC）增殖的抑制作用及其对细胞周期和周期蛋白依赖性激酶抑制物p21、p27，细胞G1－S期转换重要调节基因PTEN、c-myc蛋白表达的影响，并进一步观察simvastatin是否通过抑制脂质代谢的中间产物－甲羟戊酸的合成而上调PTEN、p27蛋白的表达及PTEN和p27是否存在上下游关系。方法：[^3H]－胸腺嘧啶核苷酸（[^3H]-TdR）掺入测定VSMC DNA合成，流式细胞仪检测细胞周期情况，Western印迹杂交法检测p21、p27及PTEN、c-myc蛋白表达，人工合成PTEN反义寡核苷酸，并以正义寡核苷酸为对照，以脂质体介导转染细胞，以Western印迹杂交流检测转染效率并观测其对PTEN、p27蛋白表达的影响。结果：simvastatin以剂量依赖关系抑制血清诱导的VSMC[^3H]-胸腺嘧啶核苷酸掺入，使G0／G1期细胞比例明显增多，S期细胞比例显减少，并上调p27及信号通路中常位于p27上游的PTEN的蛋白表达，但不影响p21、c-myc蛋白表达，PTEN反义寡核苷酸下调PTEN蛋白的表达后并不影响p27蛋白表达，200μmol/L甲羟戊酸能显抑simvastatin诱导的PTEN、p27蛋白表达升高。结论：simvastatin能抑制VSMC增殖，使细胞周期停滞于G0／G1期，这一过程可能通过不同的信号途径分别上调PTEN、p27这两个调控G1－S周期转换的基因而实现，而非通过PTEN－p27这一经典通路，simvastatin对PTEN、p27的调节与其抑制甲羟戊酸的合成有关。     

普伐他汀对人结肠癌细胞增殖及COX-2蛋白表达的影响

目的体外观察普伐他汀对人结肠癌细胞HT-29、Ls-174-T细胞增殖、细胞周期及COX-2蛋白表达的影响。方法采用噻唑蓝（MTT）法观察普伐他汀对HT-29和Ls-174-T细胞增殖的影响，流式细胞仪（FCM）研究普伐他汀对细胞周期的作用，免疫细胞化学观察COX-2蛋白的表达。结果体外普伐他汀可抑制HT-29和Ls-174-T细胞增殖，各处理组内G0／G1期细胞增多，但诱导凋亡不明显，体外普伐他汀可减少HT-29和Ls-174-T细胞株COX-2蛋白的表达。结论体外普伐他汀对HT-29和Ls-174-T细胞增殖有抑制作用，该作用可能与使细胞生长阻滞于G0／G1期及抑制COX-2蛋白表达有关。     

甘露糖敏感型绿脓杆菌制剂对肝癌细胞增殖的影响

目的：探讨甘露糖敏感型绿脓杆菌制剂（PA-MSHA）对肝癌细胞增殖的影响及其作用机制。方法培养人肝癌细胞株HepG2和MHCC97 L并分别随机分为对照组、观察1组、观察2组和观察3组。对照组为空白组,观察1组予1．0×10^8/mL PA-MSHA处理,观察2组予2．0×10^8/mL PA-MSHA处理,观察3组予2．0×10^8/mL PA-MSHA＋100 mmol/L甘露糖处理;观察各组干预后1、2、3、4、5、6 h细胞增殖率、细胞周期,测定干预前后相关蛋白表达情况。结果 HepG2和MHCC97L观察1组、观察2组各时间点细胞增殖率明显低于对照组（P＜0．05）,且呈浓度及时间依赖性;观察3组与对照组比较无明显差异;各观察组Cyclin D1、PCNA和CDK2表达均明显低于对照组,p21与p27蛋白表达均明显高于对照组（P均＜0．05）。结论 PA-MSHA对肝癌细胞增殖具有抑制作用,其机制主要是抑制Cyclin D1、PCNA和CDK2表达,促进p21与p27表达通过对相关蛋白进行诱导,促使肝癌细胞周期发生变化,且整个过程中是通过肝癌细胞表面的甘露糖而实现的。     

人激肽释放酶基因转移对大鼠血管平滑肌细胞增殖的影响

目的 探讨重组腺病毒介导的人激肽释放酶(human tissue kallikrein 1,hKLK1)基因转移对血小板源性生长因子-BB(platelet derived growth factor-BB,PDGF-BB)诱导下的自发性高血压大鼠(SHR)血管平滑肌细胞(vascular smooth muscle cells,VSMCSHR)增殖的影响及其机制.方法 自行构建重组腺病毒载体,携带目的 基因hKLK1和标志基因强绿色荧光蛋白.细胞计数法和四甲基偶氮唑盐(MTF)比色法检测细胞增殖,流式细胞仪检测细胞生长周期.蛋白免疫印迹法测定细胞周期素依赖性激酶抑制蛋白p27Kip1、p21Cip1的表达.RT-PCR法测定缓激肽B1受体、B2受体的mRNA表达.结果 (1)hKLK1基因转移呈感染复数依赖性(20～100 M0I)抑制PDGF-BB诱导的VSMCSHR生长,100 MOI时抑制率为39.3%;呈时间依赖性抑制VSMCSHR生长,第5天时达高峰,抑制率为35.2%.(2)hKLK1基因转移可显著抑制PDGF-BB诱导的VSMCSHR增殖,峰值抑制率为30.2%(P＜0.01);细胞周期阻滞于G0/G1期的VSMCSHR明显增多,最大阻滞率为36.4%(P＜0.001).(3)hKLK1基因转移明显上调PDGF-BB诱导VSMCSHR的p27Kip1、p21Cip1表达,而缓激肽B2受体特异性阻断剂Hoe140明显降低p27Kip1、p21Cip1表达.(4)PDGF-BB诱导VSMCSHR的缓激肽B2受体mRNA表达明显增加(P＜0.001),且Hoe140可明显降低其表达(P＜0.01).结论 hKLK1基因转移可抑制PDGF-BB诱导的VSMCSHR增殖,可上调缓激肽B2受体和细胞周期素依赖性激酶抑制蛋白p27Kip1、p21Cip1表达.     

MS-275抑制肝癌细胞HepG2增殖及其相关信号传导机制的体外实验研究

目的研究组蛋白去乙酰化酶(HDAC)抑制剂MS-275诱导人肝癌细胞株HepG2细胞周期阻滞作用,并对其信号传导机制进行初步探讨。方法体外培养人肝癌细胞株HepG2;应用MTT比色法观察MS-275对HepG2的生长抑制作用,应用流式细胞仪检测MS-275对细胞周期的影响;Western印迹分析细胞周期蛋白(Cyclin)D1、p21、p-p38MAPK三种蛋白表达的差异。结果HDAC抑制剂MS-275能抑制肝癌细胞生长,具有时间和剂量的依赖性。可以引起细胞周期G0-G1期阻滞。MS-275可以使HepG2细胞p21蛋白表达提高,CyclinD1蛋白表达降低,在SB203580组两蛋白的表达又恢复到对照组水平。p-p38MAPK蛋白在两组表达均提高。结论MS-275能诱导肝癌细胞株的细胞周期阻滞,这种作用可能是通过p38MAPK信号传导途径介导的,与下调CyclinD1的表达、上调p21的表达有关。     

辛伐他汀对非酒精性脂肪性肝病大鼠肝组织纤维化的影响及分子机制

目的 探讨辛伐他汀对非酒精性脂肪性肝病(NAFLD)肝组织纤维化模型及肝星状细胞的作用及其分子机制.方法 ①体内实验应用高脂饮食建立NAFLD肝组织纤维化大鼠模型,并用辛伐他汀干预,RT-PCR法和Western印迹检测大鼠肝组织中内皮型一氧化氮合酶(eNOS)、诱导型NOS(iNOS)和Ⅰ型胶原mRNA和蛋白的表达.②体外实验采用促进脂肪细胞分化的培养基诱导人肝星状细胞株LX-2细胞获得静止表型,分别用转化生长因子β1( TGF-β1)、NOS抑制剂亚硝基左旋精氨酸甲酯(L-NAME)、辛伐他汀、TGF-β1+辛伐他汀、L-NAME+辛伐他汀处理静止型LX-2细胞,RT-PCR法和Western印迹检测各组LX-2细胞中eNOS、iNOS、α-平滑肌肌动蛋白(α-SMA)、Ⅰ型胶原mRNA及蛋白的变化.结果 ①随造模时间延长,模型组大鼠肝组织eNOS mRNA和蛋白表达逐渐减少,iNOS和Ⅰ型胶原mRNA和蛋白表达逐渐增加,与正常对照组比较差异有统计学意义(P分别＜0.05和0.01).与24周末模型组相比,辛伐他汀干预组大鼠肝组织eNOS mRNA和蛋白的表达分别增加(0.30±0.02比0.24±0.01和0.45±0.04比0.22±0.02,P值均＜0.05),iNOS mRNA和蛋白的表达分别减少,Ⅰ型胶原mRNA和蛋白表达分别减少(P值均＜0.05).模型组大鼠肝组织中eNOS mRNA和蛋白表达与Ⅰ型胶原mRNA和蛋白表达均呈负相关(P值均＜0.01);iNOS mRNA和蛋白表达与Ⅰ型胶原mRNA和蛋白表达均呈正相关(P值均＜0.01).②体外培养LX-2细胞中,L-NAME能抑制LX-2细胞活化,减少eNOS和iNOS的表达,增加α-SMA和Ⅰ型胶原表达,与TGF-β1作用一致;辛伐他汀能直接增加静止型及活化型LX-2细胞中eNOS的表达,减少iNOS的表达,维持其静止表型,抑制其活化.结论 辛伐他汀通过增加LX-2细胞中eNOS表达,减少iNOS表达,减少α-SMA和Ⅰ型胶原生成,抑制或逆转肝纤维化发生和发展.     

Constitutive expression of B-myb can bypass p53-induced Waf1/Cip1-mediated G1 arrest.

Overexpression of wild-type p53 protein has been shown to induce arrest in the G1 stage of the cell cycle and to transactivate expression of the gene that encodes the 21-kDa Waf1/Cip1 protein, a potent inhibitor of cyclin-dependent kinase activity. p53-dependent G1 arrest is accompanied by decreased expression of the B-myb gene, a relative of the c-myb cellular oncogene. In this study we show that B-myb expression is required for cells to progress from G1 into S phase and that high levels of ectopic B-myb expression uncoupled from cell cycle regulation rescues cells from p53-induced G1 arrest even in the presence of Waf1/Cip1 transactivation and inhibition of cyclin E/Cdk2 kinase activity. Cotransfection experiments with p53 expression plasmids and expression plasmids encoding in-frame deletion mutations in B-myb coding sequences indicate that the DNA-binding domain of the B-Myb protein is required for this activity. These results provide evidence of a bypass of p53-induced Waf1/Cip1-mediated cell cycle regulatory pathways by a member of the myb oncogene family.     

3-Hydroxy-3-methylglutaryl CoA reductase inhibitors prevent high glucose-induced proliferation of mesangial cells via modulation of Rho GTPase/ p21 signaling pathway: Implications for diabetic nephropathy

Inhibitors of 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase, also known as statins, are lipid-lowering agents widely used in the prevention of coronary heart disease. Recent experimental and clinical data, however, indicate that the overall benefits of statin therapy may exceed its cholesterol-lowering properties. We postulate that statins may ameliorate the detrimental effects of high glucose (HG)-induced proliferation of mesangial cells (MCs), a feature of early stages of diabetic nephropathy, by preventing Rho isoprenylation. Rat MCs cultured in HG milieu were treated with and without simvastatin, an HMG-CoA reductase inhibitor. Simvastatin inhibited HG-induced MC proliferation as measured by [(3)H]thymidine incorporation. This inhibitory effect was reversed with geranylgeranyl pyrophosphate, an isoprenoid intermediate of the cholesterol biosynthetic pathway. At the cell-cycle level, the HG-induced proliferation of MCs was associated with a decrease in cyclin dependent kinase (CDK) inhibitor p21 protein expression accompanied by an increase in CDK4 and CDK2 kinase activities. Simvastatin reversed the down-regulation of p21 protein expression and decreased CDK4 and CDK2 kinase activities. Exposure of MCs to HG was associated with an increase in membrane-associated Ras and Rho GTPase protein expression. Cotreatment of MCs with simvastatin reversed HG-induced Ras and Rho membrane translocation. Immunofluorescence microscopy revealed that the overexpression of the dominant-negative RhoA led to a significant increase in p21 expression. Our data suggest that simvastatin represses the HG-induced Rho GTPase/p21 signaling in glomerular MCs. Thus, this study provides a molecular basis for the use of statins, independently of their cholesterol-lowering effect, in early stages of diabetic nephropathy.     

Cancer dormancy and cell signaling: induction of p21(waf1) initiated by membrane IgM engagement increases survival of B lymphoma cells.

The p21(WAF1) (p21) cyclin-dependent kinase inhibitor plays a major role in regulating cell cycle arrest. It was recently reported that the p53-independent elevation of p21 protein levels is essential in mediating the G(1) arrest resulting from signal transduction events initiated by the crosslinking of membrane IgM on Daudi Burkitt lymphoma cells. Although the role of p21 in cell cycle regulation is well documented, there is little information concerning its role in antibody-mediated apoptosis. In the present study, we examined the involvement of p21 in the regulation of apoptosis by suppressing its induction in anti-IgM-treated Daudi cells through a p21 antisense expression construct approach. Reduction in induced p21 protein levels resulted in diminished G(1) arrest and increased apoptosis. The increased susceptibility to anti-IgM-mediated apoptosis was associated with increased caspase-3-like activity and poly-(ADP)ribose polymerase cleavage. These data suggest that p21 may directly interfere with the caspase cascade, thus playing a dual role in regulating both cell cycle progression and apoptosis.     

Down-regulation of p21WAF1/CIP1 or p27Kip1 abrogates antiestrogen-mediated cell cycle arrest in human breast cancer cells

Estrogens and antiestrogens influence the G(1) phase of the cell cycle. In MCF-7 breast cancer cells, estrogen stimulated cell cycle progression through loss of the kinase inhibitor proteins (KIPs) p27 and p21 and through G(1) cyclin-dependent kinase (cdk) activation. Treatment with antiestrogen drugs, Tamoxifen or ICI 182780, caused cell cycle arrest, with up-regulation of both p21 and p27 levels, an increase in their binding to cyclin E-cdk2, and kinase inhibition. The requirement for these KIPs in the arrests induced by estradiol depletion or by antiestrogens was investigated with antisense. Antisense inhibition of p21 or p27 expression in estradiol-depleted or antiestrogenarrested MCF-7 led to abrogation of cell cycle arrest, with loss of cyclin E-associated KIPs, activation of cyclin E-cdk2, and S phase entrance. These data demonstrate that depletion of either p21 or p27 can mimic estrogen-stimulated cell cycle activation and indicate that both of these KIPs are critical mediators of the therapeutic effects of antiestrogens in breast cancer.