神经生长导向因子SLIT2抑制结肠癌细胞迁移的作用研究

目的:研究SLIT2基因对结肠癌细胞迁移能力的影响。方法:通过western blot技术检测SLIT2在各种结肠癌细胞系中的表达,采用小干扰RNA转染技术,在低转移细胞系RKO中沉默SLIT2基因表达,并采用PCR和western blot技术验证其干扰效率。采用质粒转染技术,在高转移细胞系LOVO中上调SLIT2基因表达后,通过Transwell迁移实验和划痕愈合实验检测SLIT2表达变化对结肠癌细胞系迁移能力的影响。结果:SLIT2在高转移细胞系LOVO和HCT116中表达明显低于低转移细胞系RKO和HT-29。在低转移细胞系RKO中敲减SLIT2后,Transwell结果显示细胞的迁移能力得到了明显增强(P0.05)。在高转移细胞系LOVO中过表达SLIT2后,细胞的划痕愈合能力和迁移能力则均受到明显抑制(P0.05)。结论:神经生长导向因子SLIT2的表达与结肠癌细胞的迁移潜能相关,体外实验表明SLIT2可抑制结肠癌细胞系LOVO、RKO的迁移能力。     

ATAD3A在结直肠癌组织中的表达及其对细胞生长的影响

目的:探讨三磷酸腺苷酶家族蛋白3A(ATAD3A)在结直肠癌组织中的表达情况,并验证其对结直肠癌细胞RKO和HCT116生长的影响。方法:收集结直肠癌患者配对癌与癌旁组织115例,通过免疫组化方式验证ATAD3A在结直肠癌组织与癌旁的表达差异。采用慢病毒转染和si-RNA干涉的方式构建ATAD3A过表达和敲低肠癌细胞系,并采用MTS,流式检测细胞周期和细胞凋亡等方法验证ATAD3A对结直肠癌细胞系RKO和HCT116的影响。结果:ATAD3A在结直肠癌组织中表达较癌旁组织显著升高(P0.001)。在结直肠癌细胞系RKO和HCT116中过表达ATAD3A后,细胞增殖能力明显增强,处于S期的细胞比例明显增加,而且细胞凋亡数量明显减少。反之,在上述肠癌细胞中干涉ATAD3A后,细胞增殖能力减弱,细胞大部分停滞于G1期,而且凋亡细胞数量明显增多。结论:ATAD3A在结直肠癌组织中表达升高,且ATAD3A通过促进细胞增殖、细胞周期进程和抑制细胞凋亡等方式促进肠癌细胞的生长。     

RNAi引起的Paxillin和p130Cas下调抑制胃癌细胞失巢性生长

P130Cas和paxillin分子是整合素家族下游重要的衔接分子.为了探索这两个分子在肿瘤细胞抗失巢凋亡中的作用,应用RNAi技术分别抑制抗失巢凋亡的胃癌细胞BGC82 3中paxillin和p130cas基因的表达,观察它们对细胞失巢性生长的影响.依据siRNA设计原则,分别设计针对p130cas和paxillin的两条序列;成功的构建了特异性封闭上述两分子的载体pWH1 p130cas和pWH1 paxillin .构建的载体瞬时转染贴壁培养和失巢培养的BGC82 3后,RT PCR和Western印迹检测发现paxillin和p130Cas分子在mRNA及蛋白水平的表达量均明显降低;倒置显微镜下观察发现,贴壁培养的胃癌细胞发生皱缩、脱落;失巢培养的细胞聚集成团的现象受到明显抑制,细胞团比对照组小,且较松散;MTT实验结果表明,失巢培养的BGC82 3pWH1 paxillin 组细胞存活率(32 19%±6 11% )和BGC82 3pWH1 p13 0cas组细胞存活率(2 8 5 2 %±5 0 2 % )与对照组相比显著下降(P <0 0 1vscontrol) ;FCM实验结果发现与失巢培养的对照组相比,BGC82 3pWH1 paxillin和BGC82 3pWH1 p13 0cas组细胞G1期抬高,并出现了凋亡峰.运用RNAi技术分别抑制了BGC82 3细胞中paxillin和p130Cas分子的表达,初步证明paxillin和p130Cas是细胞存活的重要信号分子,在肿瘤细胞抗失巢凋亡过程中具有重要的作用.     

miR-935靶向GLUD1调控LKB1缺失型肺癌失巢凋亡机制

[目的]探讨miR-935靶向GLUD1调控LKB1缺失型肺癌细胞失巢凋亡的潜在机制。[方法]分离条件下培养肺癌细胞构建失巢细胞模型,抽取各个分离时间点的细胞总RNA进行miRNA-seq,过表达或敲低差异miRNA后检测LKB1缺失型肺癌细胞A549和H157的失巢凋亡水平。通过miRDB在线分析和遗传学筛选鉴定miRNA的关键底物。根据是否过表达miR-935分为对照组和miR-935过表达组;根据是否敲低GLUD1分为对照组和GLUD1敲低组。[结果]随着分离时间的延长,肺癌细胞中miR-935的表达水平下降(1.47±0.15 vs 0.09±0.01,P<0.05)、GLUD1的表达水平上升(0.87±0.16 vs 1.44±0.21,P<0.05)。过表达miR-935后,肺癌细胞的失巢凋亡水平上升[(15.87±2.23)%vs(49.79±7.63)%,P<0.05]。敲低GLUD1后,肺癌细胞的失巢凋亡水平显著上升[(16.32±3.11)%vs(48.21±5.67)%,P<0.05]。过表达miR-935后,肺癌细胞中GLUD1 mRNA...     

NDRG1基因过表达对胆囊癌GBS-SD细胞增殖及凋亡的影响

为了探讨N-myc下游调节基因1 (NDRG1)过表达对胆囊癌细胞系GBS-SD细胞增殖、迁移、侵袭和凋亡的影响及其可能的分子机制,本研究采用脂质体介导的重组真核表达质粒pEGFP-NDRG1-N3瞬时转染人胆囊癌GBS-SD细胞,Western blotting检测NDRG1蛋白的表达;MTT比色法和流式细胞术分别检测细胞增殖和细胞周期;Transwell实验检测细胞侵袭和迁移能力。GBS-SD细胞转染pEGFP-NDRG1-N3重组质粒后经表阿霉素(0.4μg/mL)诱导其凋亡,采用Hoechst 33258染色和流式细胞仪检测细胞凋亡;Western blotingt检测Bcl-2、Cleaved caspase-3和Bid蛋白的表达。MTT检测显示,NDRG1过表达组细胞在48 h和72 h的增殖速度均显著高于空载组和对照组(p0.05)。Transwell检测显示,与对照组和空载组相比,NDRG1过表达组细胞的侵袭和迁移能力明显增强。Hoechst 33258染色和流式细胞仪检测显示,经表阿霉素诱导细胞凋亡后,空载组细胞的凋亡率最高,NDRG1过表达组细胞的凋亡率低于空载组,但显著高于对照组。Western blotting检测显示,与对照组和空载组相比,NDRG1过表达组细胞中Bcl-2的表达明显上调,而Cleaved caspase-3和Bid的表达明显下调。本研究表明NDRG1基因过表达可显著促进胆囊癌细胞增殖、迁移、侵袭并抑制其凋亡,其分子机制可能是上调的NDRG1基因能有效调节与细胞凋亡相关基因的表达,从而发挥其介导作用。因此,NDRG1基因可能成为胆囊癌研究中一个新的治疗靶点。     

小G蛋白Ran对胰腺癌细胞增殖和凋亡的调控

目的:探讨Ras超家族的小G蛋白Ran GTPase在胰腺癌组织及细胞中的表达情况,及其对胰腺癌细胞PANC-1增殖和凋亡的影响.方法:选取胰腺癌石蜡标本及相应正常组织标本各27例进行免疫组织化学染色.用LipofectamineTM2000转染Ran干扰RNA (small interference RNA,siRNA)进入胰腺癌细胞系PANC-1干扰其表达,之后利用Western blot观察Ran的表达情况.运用MTT及流式细胞术分别检测各实验组细胞的增殖和凋亡情况.结果:免疫组化染色显示在胰腺癌组织中Ran的表达阳性率及得分均明显高于癌旁正常组织(P＜0.05).将干扰Ran siRNA转染进入细胞系PANC-1中,利用Westemblot发现Ran的表达明显下调.并且通过MTT实验发现在胰腺癌细胞系PANC-1中下调Ran表达能明显抑制该细胞生长(P＜0.05),并使PANC-1细胞凋亡显著增多(P＜0.05).结论:小G蛋白Ran GTPase在胰腺癌组织及细胞系中高表达,且Ran可以促进胰腺癌细胞PANC-1的增殖,抑制其凋亡.     

乙酰肝素酶siRNA对人膀胱癌T24细胞株侵袭能力的影响

目的:观察乙酰肝素酶(Heparanase,HPSE)小干扰R N A(small-interfering RNA,siRNA)对人膀胱癌细胞株侵袭力的影响.方法:体外化学合成一段乙酰肝素酶特异性小干扰RNA(siRNA)序列,以阳离子脂质体介导将不同浓度的siRNA转染至膀胱癌细胞系T24细胞中,应用逆转录—聚合酶链反应(RT-PCR)法检测转染前后T24细胞中HPSE mRNA表达,采用transwell小室侵袭试验测定肿瘤细胞的体外侵袭力.结果:转染HPSE siRNA可以显著降低T24细胞中的HPSE mRNA表达,HPA siRNA处理细胞48小时,与对照组相比,各有效浓度的HPSE siRNA可显著抑制T24细胞的体外侵袭能力(P＜0.05).结论:以siRNA阻遏乙酰肝素酶在膀胱癌细胞中表达可以成功地抑制膀胱癌细胞侵袭能力,通过应用RNA干扰技术等方法抑制乙酰肝素酶活性可能可以应用于临床治疗膀胱癌.     

siRNA沉默VEGF基因对大肠癌细胞生物学特性的影响

目的研究VEGF和受体FLT-1、FLK-1在大肠癌组织中的表达及与临床病理因素之间的关系;观察SiRNA干扰VEGF基因对人大肠癌细胞系Caco-2生物学特性的影响。方法应用免疫组织化学S?P法,检测82例大肠癌及14例大肠正常黏膜组织中VEGF和FLT-1、FLK-1的表达;以脂质体lip-2000为载体,用针对VEGF特异靶点的siRNA转染入人大肠癌细胞系Caco-2后,免疫细胞化学S-P法、Western Blot检测VEGF蛋白表达变化,MTT法检测对细胞增殖的影响;流式细胞技术检测细胞凋亡。结果 (1)大肠癌组织VEGF和受体FLT-1、FLK-1阳性表达率显著高于正常大肠组织(P0.05)。VEGF的表达在有无淋巴结转移组和不同的Duke’s分期中亦有显著差异(P0.05)。(2)VEGF-siRNA转染Caco-2细胞后,免疫细胞化学结果显示转染VEGF-siRNA组阳性细胞呈弱阳性表达,明显减弱;Westernblot结果显示VEGF-siRNA组细胞的蛋白条带亮度明显降低;MTT检测VEGF-siRNA组细胞生长出现明显的抑制(P0.05),不同时段(24h、48h、72h)肿瘤细胞增殖抑制率之间有显著差异(P0.05);流式细胞术检测VEGF-siRNA组出现明显亚二倍体峰,凋亡率显著高于正常对照组(P0.01)。结论 VEGF在大肠癌的进展过程中起重要作用。siRNA干扰VEGF基因能有效抑制人大肠癌细胞系VEGF蛋白表达,细胞增殖能力减弱,促进细胞凋亡。以VEGF基因为靶点,利用siRNA技术进行基因治疗有可能成为一种新的有效手段。     

siRNA抑制Survivin基因对大肠癌细胞HCT116增殖及凋亡的的影响

目的探讨si RNA沉默Survivin基因后对人大肠癌细胞系HCT116的Survivin蛋白表达、细胞增殖及凋亡的影响。方法以脂质体lip-2000为载体,用针对Survivin特异靶点的si RNA转染人大肠癌细胞系HCT116后,应用免疫细胞化学S-P法、Western Blot检测Survivin蛋白表达变化;MTT法检测细胞增殖;流式细胞技术检测细胞凋亡。结果免疫细胞化学结果显示:HCT116的正常对照组、脂质体对照组及阴性错配对照组细胞浆均呈强阳性表达,Survivin-si R-NA组细胞浆Survivin呈弱阳性表达;Western blot结果显示:HCT116细胞系Survivin-si RNA组细胞的蛋白条带亮度均明显低于正常对照组、脂质体对照组和阴性错配对照组;MTT检测结果:与阴性错配对照组相比,Survivin-si RNA组细胞生长出现明显的抑制(P0.05),不同时段(24h、48h、72h)肿瘤细胞增殖抑制率之间有显著差异(P0.05)。流式细胞术检测Survivin-si RNA组细胞凋亡比例为9.72%,明显高于空白对照组及阴性错配对照组(P0.01)。结论si RNA抑制Survivin基因可以抑制大肠癌细胞增殖,促进凋亡;Survivin有望成为大肠癌基因治疗的新靶点。     

双歧杆菌脂磷壁酸对结肠癌细胞抑制增殖和促凋亡的研究

目的 探讨双歧杆菌脂磷壁酸(lipoteichoic acid,LTA)抑制人类结肠癌细胞株HCT116细胞增殖和促进凋亡情况.方法 培养结肠癌细胞株HCT116和提取双歧杆菌LTA;实验分为4组,即LTA低剂量组(20 μg/mL)、中剂量(60 μg/mL)、高剂量(100μg/mL)和HCT116对照组(Control);用四甲基偶氮唑蓝法(MTT)检测LTA对结肠癌细胞增殖的抑制率,流式细胞仪检测LTA对结肠癌细胞周期分布变化和凋亡率,免疫组化分析bcl-2、Cytochrome C和NF-kBp65含量变化,RT-PCR检测TLR2mRNA和TLR4m RNA的表达.结果 MTT法测得LTA各组对结肠癌细胞HCT116均具有较好的抑制(P＜0.01);流式细胞仪检得G0/G1期细胞显著增多(P＜0.01),而G2和S期细胞减少(P＜0.05),细胞凋亡率增加(P＜0.05);免疫组化分析IOD/Area值,bcl-2和NF-kBp65表达显著下调,Cytochrome C显著上升(P＜0.05);RT-PCR测得TLR2 mRNA和TLR4 mRNA的表达均上升(P＜0.05).结论 LTA具有明显的抑制结肠癌细胞增殖和促进凋亡作用,为研制高效、无毒的新型抗结肠癌药物奠定一定的基础.     

Induction of autophagy by dimethyl cardamonin is associated with proliferative arrest in human colorectal carcinoma HCT116 and LOVO cells

Dimethyl cardamonin (2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone; DMC) is a naturally occurring chalcone, and it is the major compound isolated from the leaves of Syzygium samarangense (Blume) Merr. & L.M. Perry (Myrtaceae). Experiments were conducted to determine the effects of DMC on cell proliferation, cell-cycle distribution, and programmed cell death in cultures of human colorectal carcinoma HCT116 and LOVO cells. Results showed that DMC inhibited HCT116 and LOVO cell proliferation and induced G(2) /M cell cycle arrest, which was associated with the conversion of microtubule associated protein light chain 3 (LC3)-I-LC3-II, an autophagosome marker, and the incorporation of monodansylcadaverine (MDC), a marker for the acidic compartment of autolysosomes or acidic vesicular organelles. The treatment of HCT116 and LOVO cells using a combination of DMC with an autophagy inhibitor, such as 3-methyladenine (3-MA), beclin 1 siRNA, or atg5 siRNA, suppressed the effect of DMC-mediated anti-proliferation. These results imply that DMC can suppress colorectal carcinoma HCT116 and LOVO cell proliferation through a G(2) /M phase cell-cycle delay, and can induce autophagy, the hallmark of Type II programmed cell death (PCD). Taken together, our results suggest that DMC may be an effective chemotherapeutic agent for HCT116 and LOVO colorectal carcinoma cells.     

Antiproliferative activity and induction of apoptosis in human colon cancer cells treated in vitro with constituents of a product derived from Pistacia lentiscus L. var. chia

In this report, we demonstrate that a 50% ethanol extract of the plant-derived product, Chios mastic gum (CMG), contains compounds which inhibit proliferation and induce death of HCT116 human colon cancer cells in vitro. CMG-treatment induces cell arrest at G(1), detachment of the cells from the substrate, activation of pro-caspases-8, -9 and -3, and causes several morphological changes typical of apoptosis in cell organelles. These events, furthermore, are time- and dose-dependent, but p53- and p21-independent. Apoptosis induction by CMG is not inhibited in HCT116 cell clones expressing high levels of the anti-apoptotic protein, Bcl-2, or dominant-negative FADD, thereby indicating that CMG induces cell death via a yet-to-be identified pathway, unrelated to the death receptor- and mitochondrion-dependent pathways. The findings presented here suggest that CMG (a) induces an anoikis form of cell death in HCT116 colon cancer cells that includes events associated with caspase-dependent pathways; and (b) might be developed into a chemotherapeutic agent for the treatment of human colon and other cancers.     

Ionizing radiation enhances the expression of the nonsteroidal anti-inflammatory drug-activated gene (NAG1) by increasing the expression of TP53 in human colon cancer cells

The induction of apoptosis in cells of human colon cancer cell lines after gamma irradiation was investigated to determine whether apoptosis was mediated by TP53 and the subsequent expression of its downstream target, the NSAID-activated gene (NAG1). HCT116 (TP53(+/+)), HCT15 (TP53 mutant) and TP53 null HCT116 (TP53(-/-)) cells were irradiated with gamma rays, and apoptosis was measured at various times after irradiation. In HCT116 TP53(+/+) cells, apoptosis was increased after irradiation; the increase was dependent on the time after treatment and the dose of gamma rays. However, in HCT15 TP53 mutant cells and HCT116 TP53(-/-) cells, there were no remarkable changes in apoptosis. The expression of TP53 protein in HCT116 cells was increased after irradiation and was followed by an increase in the expression of NAG1 protein. In contrast, the expression of NAG1 protein in TP53 mutant cells and TP53(-/-) cells was not increased by the radiation treatment, suggesting that NAG1 was required for apoptosis. The expression of NAG1 increased apoptosis in HCT116 cells, but radiation treatment did not further increase apoptosis. The transfection of a NAG1 siRNA into HCT116 cells suppressed radiation-induced apoptosis and inhibited the induction of NAG1 protein without altering the expression of TP53. a NAG1 luciferase promoter construct that included both of the TP53 binding sites, was activated by radiation in dose-dependent manner, while the promoters lacking one or both of the TP53 binding sites in the NAG1 promoter activity either was less responsive or did not respond. The findings reported here indicate that gamma radiation activates the TP53 tumor suppressor, which then increases the expression of NAG1. NAG1 mediates the induction of apoptosis in human colorectal cells.     

Anti-cancer effects of JKA97 are associated with its induction of cell apoptosis via a Bax-dependent and p53-independent pathway

p53, one of the most commonly mutated genes in human cancers, is thought to be associated with cancer development. Hence, screening and identifying natural or synthetic compounds with anti-cancer activity via p53-independent pathway is one of the most challenging tasks for scientists in this field. Compound JKA97 (methoxy-1-styryl-9H-pyrid-[3,4-b]-indole) is a small molecule synthetic anti-cancer agent, with unknown mechanism(s). In this study we have demonstrated that the anti-cancer activity of JKA97 is associated with apoptotic induction via p53-independent mechanisms. We found that co-incubation of human colon cancer HCT116 cells with JKA97 inhibited HCT116 cell anchorage-independent growth in vitro and tumorigenicity in nude mice and also induced a cell apoptotic response, both in the cell culture model and in a tumorigenesis nude mouse model. Further studies showed that JKA97-induced apoptosis was dramatically impaired in Bax knock-out (Bax(-/-)) HCT116 cells, whereas the knock-out of p53 or PUMA did not show any inhibitory effects. The p53-independent apoptotic induction by JKA97 was confirmed in other colon cancer and hepatocarcinoma cell lines. In addition, our results showed an induction of Bax translocation and cytochrome c release from the mitochondria to the cytosol in HCT116 cells, demonstrating that the compound induces apoptosis through a Bax-initiated mitochondria-dependent pathway. These studies provide a molecular basis for the therapeutic application of JKA97 against human cancers with p53 mutations.     

PXR基因外显子3甲基化与肠癌细胞对5氟尿嘧啶的耐药性相关

孕烷X受体（pregnane X receptor, PXR）可通过调节细胞色素P450同工酶3A4 -CYP3A4的表达而影响肿瘤细胞对化疗的敏感性,而其表达水平则会受到自身基因 甲基化的影响.本文研究了结肠癌组织中pxr基因甲基化的分布情况及其对pxr, cyp3a4表达的影响,并在多种结肠癌细胞系中分析了pxr基因甲基化是否与5-氟尿嘧 啶 (5-FU)耐药性相关.收集结肠癌病灶区、癌旁区及正常结肠组织样本,分别提取基因组DNA及RNA.PCR限制性酶切分析检测pxr基因外显子3甲基化;real-time PCR检测pxr及cyp3a4基因的表达.鉴定LOVO、LS180、LS174T、HT29、HCT116等5种结 肠癌细胞中pxr外显子3甲基化与pxr, cyp3a4表达的相关性并分别筛选出PXR高/低表达的细胞株进行5-FU耐药性分析.结果显示,结肠癌病灶组织中pxr外显子3甲基化频率显著增加,伴有pxr,cyp3a4表达的增强.在结肠组织及结肠癌细胞系中,pxr与cyp3a4的表达均密切相关,且均与pxr甲基化程度相关.PXR高表达细胞株LS180对5-FU的耐药性显著升高,以siRNA分别下调pxr及cyp3a4的表达,均可增加LS180对5 -FU的敏感性.结果提示,pxr基因外显子3区甲基化与PXR及CYP3A4的高表达密切相关,并与结肠癌细胞对5-FU的抗药性相关.     

CHOP is involved in endoplasmic reticulum stress-induced apoptosis by enhancing DR5 expression in human carcinoma cells

It has been shown that excess stress to the endoplasmic reticulum (ER) triggers apoptosis, but the mechanisms underlying these processes remain unclear. We and others have reported previously that DR5 expression is up-regulated in thapsigargin (THG)-treated human cancer cells. Here, we provide evidence that CHOP is involved in THG up-regulation of DR5, which is a critical step for ER stress-induced apoptosis in human cancer cells. In human colon cancer HCT116 cells, knockdown of DR5 by siRNA blocked THG-induced Bax conformational change along with caspase-3 activation and cell death. Moreover, inhibition of CHOP expression attenuated DR5 up-regulation and apoptosis induced by THG, whereas ectopic expression of DR5 restored the sensitivity of CHOP siRNA-transfected cells to THG-induced apoptosis. In addition to HCT116 cells, inhibition of CHOP or DR5 induction also attenuated THG-induced cell death in other cancer cell lines including LNCaP, A2780S, and DU145, indicating that CHOP and DR5 are critical for ER stress-mediated apoptosis in human carcinoma cells. Furthermore, we identified a potential CHOP-binding site in the 5'-flanking region of the DR5 gene. Mutation of this site abrogated the enhanced reporter activity in response to THG treatment. Together, our findings suggest that CHOP regulates ER stress-induced apoptosis, at least in part, through enhancing DR5 expression in some types of human cancer cells.     

Metastatic SW620 colon cancer cells are primed for death when detached and can be sensitized to anoikis by the BH3-mimetic ABT-737

Anoikis, a Bax-dependent apoptosis triggered by detachment from the extracellular matrix, is often inhibited in metastatic cancer cells. Using a couple of isogenic human colon cancer cell lines derived either from the primary tumor (SW480) or from a lymph node metastasis (SW620), we found that only SW480 cells were sensitive to anoikis. Bim upregulation but not Mcl-1 degradation was determined to be a critical factor of anoikis initiation in SW480 cells. ERK-mediated phosphorylation targets Bim for ubiquitination and proteasomal degradation. A MEK inhibitor (PD0325901) was able to increase Bim expression in SW620 cells and to sensitize these cells to anoikis. Thus, in both cell lines anoikis is under the control of proteins of the Bcl-2 family. Most interestingly, the BH3-mimetic ABT-737 was found not only to increase the level of apoptosis in suspended SW480 cells but also to sensitize SW620 cells to anoikis. Accordingly, both cell lines cultured in suspension were found to be primed for death, as determined by the detection of Bcl-2:Bim and Bcl-xL:Bim complexes. In contrast, adherent SW480 and SW620 cells were resistant to ABT-737. This indicates that, whether or not they undergo anoikis, colon cancer cells that have detached from the extracellular matrix might go through a transient state, where they are sensitive to BH3 mimetics. This would confer to compounds such as Navitoclax or ABT-199 a therapeutic window where they could have anti-metastatic potential.     

MicroRNA-218 Inhibits Cell Cycle Progression and Promotes Apoptosis in Colon Cancer by Downregulating BMI1 Polycomb Ring Finger Oncogene

Deregulated miRNAs participate in colorectal carcinogenesis. In this study, miR-218 was found to be downregulated in human colorectal cancer (CRC) by miRNA profile assay. miR-218 was silenced or downregulated in all five colon cancer cells (Caco2, HT29, SW620, HCT116 and LoVo) relative to normal colon tissues. miR-218 expression was significantly lower in 46 CRC tumor tissues compared with their adjacent normal tissues (P < 0.001). Potential target genes of miR-218 were predicted and BMI1 polycomb ring finger oncogene (BMI-1), a polycomb ring finger oncogene, was identified as one of the potential targets. Upregulation of BMI-1 was detected in CRC tumors compared with adjacent normal tissues (P < 0.001) and in all five colon cancer cell lines. Transfection of miR-218 in colon cancer cell lines (HCT116, HT29) significantly reduced luciferase activity of the wild-type construct of BMI-1 3′ untranslated region (3′UTR) (P < 0.001), whereas this effect was not seen in the construct with mutant BMI-1 3′UTR, indicating a direct and specific interaction of miR-218 with BMI-1. Ectopic expression of miR-218 in HCT116 and HT29 cells suppressed BMI-1 mRNA and protein expression. In addition, miR-218 suppressed protein expression of BMI-1 downstream targets of cyclin-dependent kinase 4, a cell cycle regulator, while upregulating protein expression of p53. We further revealed that miR-218 induced apoptosis (P < 0.01), inhibited cell proliferation (P < 0.05) and promoted cell cycle arrest in the G2 phase (P < 0.01). In conclusion, miR-218 plays a pivotal role in CRC development through inhibiting cell proliferation and cycle progression and promoting apoptosis by downregulating BMI-1.     

NAG-1 up-regulation mediated by EGR-1 and p53 is critical for quercetin-induced apoptosis in HCT116 colon carcinoma cells

Quercetin, a flavonoid molecule ubiquitously present in nature, has multiple effects on cancer cells, including the inhibition of cell proliferation and migration. However, the responsible molecular mechanisms are not fully understood. We found that quercetin induces the expression of NAG-1 (Non-steroidal anti-inflammatory drug activated gene-1), a TGF-β superfamily protein, during quercetin-induced apoptosis of HCT116 human colon carcinoma cells. Reporter assays using the luciferase constructs containing NAG-1 promoter region demonstrate that early growth response-1 (EGR-1) and p53 are required for quercetin-mediated activation of the NAG-1 promoter. Overexpression of NAG-1 enhanced the apoptotic effect of quercetin, but suppression of quercetin-induced NAG-1 expression by NAG-1 siRNA attenuated quercetin-induced apoptosis in HCT116 cells. Taken together, the present study demonstrates for the first time that quercetin induces apoptosis via NAG-1, providing a mechanistic basis for the apoptotic effect of quercetin in colon carcinoma cells.