黏着斑激酶在结肠癌细胞株中的表达及其RNA干扰载体的构建

目的 检测结肠癌细胞株中FAK的蛋白表达水平,并构建FAK靶向RNA干扰重组体.方法 通过免疫细胞化学SP法和Western Blotting技术检测结肠癌细胞株SW480、HCT116、HT29、LOVO中FAK的表达水平;针对FAK序列设计并合成具有小发夹结构的两条DNA序列,经退火后再重组入pGenesil-1载体,并转化大肠杆菌DH5α,经酶切及测序鉴定后转染结肠癌HT29细胞株.结果 FAK在SW480、HCT116、HT29、LOVO等细胞株中均有较高表达,其中HT29为最高.重组体经鉴定与设计序列一致,并稳定转染HT29细胞.结论 FAK在4个细胞株中高表达可能对结肠癌及其进展有重要作用;FAK靶向RNA干扰重组体的成功构建和转染,为结直肠癌新的基因治疗方法提供可能的思路.     

EphB2蛋白在结直肠癌中的表达及意义

目的:研究EphB2蛋白在不同临床病理分期的结直肠癌组织以及在不同转移能力的结直肠癌细胞株中的表达差异,并初步探讨EphB2对结直肠癌作用的相关机制.方法:运用免疫组织化学法检测43例结直肠癌和10例正常组织中EphB2受体的表达及间质微血管密度(microvascular density,MVD); 体外培养SW480、HT29、HCT116和LoVo 等4种具有不同转移能力的结直肠癌细胞株, Western印迹法检测EphB2蛋白的表达,RT-PCR法检测EphB2 mRNA水平的表达.结果:EphB2在大多数结直肠癌细胞质中表达,EphB2受体的表达和肿瘤的浸润深度以及远处转移呈负相关,与肿瘤组织的分化程度呈正相关,EphB2蛋白的表达与肿瘤的MVD呈正相关;高转移性结直肠癌细胞株HCT116和LoVo中EphB2蛋白及EphB2 mRNA的表达均较低转移性细胞株SW480和HT29明显降低.结论:EphB2表达对肿瘤的生长可能起抑制作用, EphB2表达的减少能促进肿瘤的形成和演进.影响肿瘤血管形成的功能可能是EphB2抑制肿瘤生长机制中的一种.     

甲磺酸阿帕替尼联合放疗协同诱导结直肠癌细胞凋亡的体外研究及机制探讨

摘 要：［目的］ 探究甲磺酸阿帕替尼联合放疗对结直肠癌细胞体外抑制作用。［方法］ 体外培养结直肠癌细胞株HCT116、SW480和HT29，采用MTT法检测HCT116、SW480和HT29细胞株对甲磺酸阿帕替尼的敏感性，以药物敏感性最高的细胞进行后续联合治疗，分为对照组、药物组、放疗组和联合组，应用MTT检测不同处理组细胞的增殖抑制能力，筛选最强联合抑制效果时的药物浓度作为后续试验；Annexin Ⅴ-FITC/PI联合流式细胞术分析不同处理组对HCT116细胞凋亡和细胞周期的影响；ELISA分析不同处理组上清中VEGF分泌水平；Western blot 试验检测VEGFR2、VEGFA、ERK/p-ERK、STAT3/p-STAT3、BAX和BCL2蛋白的表达。［结果］ 甲磺酸阿帕替尼抑制结直肠癌细胞HCT116、SW480和HT29体外增殖且具有剂量依赖性，半数致死浓度(IC50)分别为14.90 μmol/L、25.99 μmol/L和24.19 μmol/L，HCT116细胞药物敏感性显著高于SW480和HT29细胞（P均<0.05），以敏感性最高的HCT116细胞进行不同分组，结果显示甲磺酸阿帕替尼浓度为8 μmol/L时，联合组对比药物组和放疗组显示更强的增殖抑制能力（65.97% vs 25.83% vs 21.97%，P均<0.001）；不同处理组细胞凋亡率有差异（F=237.930，P=0.000），对比药物组（8 μmol/L）和放疗组，联合组细胞凋亡率显著增加［（6.55±0.58）% vs （12.69±0.71）% vs （29.11±2.08）%，P均<0.001］；联合组未能增强阿帕替尼（8 μmol/L）对细胞周期的阻滞（P=0.09）；细胞上清中VEGF分泌水平在4组间无差异（P>0.05），联合组VEGFA蛋白的表达显著下调；但放疗未增加阿帕替尼（8 μmol/L）对VEGFR2的抑制作用；对比药物组（8 μmol/L）和放疗组，联合组增加了促凋亡基因BAX蛋白表达，并抑制抗凋亡基因BCL2蛋白表达，此外联合组处理后p-STAT3蛋白的磷酸化水平显著降低，STAT3和ERK总蛋白水平无改变。［结论］ 甲磺酸阿帕替尼联合放疗可能通过抑制STAT3通路诱导细胞凋亡，从而抑制HCT116细胞的增殖。     

FOXJ1调控AKT信号通路对结直肠癌细胞凋亡和侵袭能力的影响

目的 探讨叉头框转录因子J1(FOXJ1)对人结直肠癌细胞凋亡和侵袭能力的影响及机制.方法 应用Western Blot方法检测人结直肠癌细胞HCT116、HT29、SW480及人正常肠上皮细胞FHC中FOXJ1的表达水平.细胞中转染pEGFP-N1-FOXJ1和pEGFP-N1,Western Blot检测细胞中FOXJ1、活化的含半胱氨酸的天冬氨酸蛋白水解酶3(Cleaved Caspase-3)、基质金属蛋白酶-2(MMP-2)、蛋白激酶B(AKT)、磷酸化的蛋白激酶B(p-AKT)的表达水平,流式细胞仪检测细胞的凋亡情况,Transwell小室检测细胞的侵袭能力.结果 人结直肠癌细胞HCT116、HT29、SW480中FOXJ1的表达水平均明显低于人正常肠上皮细胞FHC(P﹤0.01).人结直肠癌细胞HCT116中FOXJ1的表达水平下降最多,后续选用HCT116细胞继续研究.转染pEGFP-N1后的细胞凋亡率、侵袭细胞数目及细胞中FOXJ1、Cleaved Caspase-3、MMP-2、AKT、p-AKT的表达水平与对照组比较,差异均无统计学意义(P﹥0.05).转染pEGFP-N1-FOXJ1后的细胞凋亡率及细胞中FOXJ1、Cleaved Caspase-3的表达水平明显高于对照组(P﹤0.01);转染pEGFP-N1-FOXJ1后的侵袭细胞数目及细胞中MMP-2、p-AKT的表达水平明显低于对照组(P﹤0.01).结论 FOXJ1在人结直肠癌细胞中过表达.FOXJ1能够促进结直肠癌细胞凋亡,抑制结直肠癌细胞侵袭,其作用机制可能与AKT信号通路有关.     

lncRNA CASC2对结直肠癌细胞功能及血管生成的影响

目的 研究lncRNA CASC2过表达对结直肠癌细胞增殖、迁移、血管生成及Wnt/FZD/β-catenin信号通路的影响.方法 qRT-PCR检测lncRNA CASC2在正常结肠上皮细胞(NCM460)及结直肠癌细胞株(DLD-1、HT29、SW620、HCT116、RKO、LOVO、SW480)中的表达情况;H...     

人参皂苷Rg3调控WNT/β-catenin信号通路抑制结肠癌细胞生长的实验研究

目的探讨人参皂苷Rg3通过影响WNT/β-catenin信号通路中关键蛋白β-catenin从而阻断结肠癌细胞生长机制的研究。方法 MTT法检测不同浓度人参皂苷Rg3对人结肠癌细胞系SW480、HCT116细胞增殖的影响;流式细胞仪检测不同浓度人参皂苷Rg3对SW480、HCT116细胞凋亡及磷酸化β-catenin的影响;RT-PCR和Western blot法检测HCT116细胞中β-catenin及c-myc的表达。结果人参皂苷Rg3具有抑制SW480、HCT116细胞增殖和促进凋亡的能力。一定浓度人参皂苷Rg3能够降低β-catenin蛋白的磷酸化程度,下调β-catenin mRNA的表达,下调β-cetanin和c-myc蛋白的表达。结论人参皂苷Rg3具有一定的抗肿瘤活性,可有效抑制HCT116和SW480细胞生长,且这种作用可能是通过下调β-catenin磷酸化来实现的。     

shRNA干扰CDX2基因表达对裸鼠结直肠癌肝转移瘤的影响

目的:建立人结直肠癌裸鼠肝转移瘤模型,探讨干扰尾型同源盒基因2(caudal-related homeobox 2,CDX2)基因表达对结直肠癌肝转移瘤的影响.方法:通过慢病毒载体将CDX2-shRNA体外转染人结直肠癌细胞SW480、HT29,筛选建立稳定干扰CDX2基因表达细胞株和阴性病毒细胞株;将稳定干扰CDX2基因表达的结直肠癌细胞(SW480-KD、HT29-KD)、空白对照细胞(SW480-CON、HT29-CON)和阴性对照细胞(SW480-NC、HT29-NC)接种到裸鼠脾下极包膜内,建立裸鼠结直肠癌肝转移瘤模型,每天称量裸鼠体质量并观察其摄食、活动及精神情况;50 d后处死裸鼠,分别从大体水平以及镜下观察肝转移瘤情况.结果:成功构建裸鼠结直肠癌肝转移模型,H-E染色确认为结直肠癌肝转移.各细胞干扰组(SW480-KD、HT29-KD)裸鼠体质量明显低于相应空白对照组和阴性对照组[SW480-KD:(15.02±2.00) vs (18.00±2.48)、(18.03 ±2.05) g;F=3.761,P ＜0.05;HT29-KD:(15.39 ±2.16) vs (17.96 ±2.48)、(18.30±1.87) g;F=3.721,P ＜0.05].SW480-KD组肝转移瘤数目明显多于SW480-CON组和SW480-NC组[(57.83 ±22.56)vs (29.50±16.90)、(28.20±15.40)个;F=4.197,P＜ 0.05];HT29-KD组肝转移瘤数目明显多于HT29-CON组和HT29-NC组[(56.83 ±29.16) vs (26.40±12.76)、(21.00±11.50)个;F=4.467,P＜0.05)].结论:脾注射法裸鼠肝转移模型可作为体内研究基因功能的理想模型;干扰CDX2基因表达可促进结直肠癌SW480和HT29细胞在体内的转移.     

阿司匹林对人结肠癌细胞株SW480、HT29中VEGF、β-catenin表达的影响

目的 探讨阿司匹林对人结肠癌细胞株HT-29、SW480生长增殖的影响及其β-catenin、VEGF蛋白和mRNA的表达,并为结直肠癌的预防和治疗提供新的实验和理论依据。方法 采用MTT法检测阿司匹林对SW480、HT-29细胞生长增殖的影响;Real-time PCR和Western blot法检测HT-29、SW480细胞中VEGF、β-catenin mRNA及蛋白的表达情况。结果 在SW480、HT-29细胞的生长增殖过程中,阿司匹林对其有着显著的抑制作用,且具有量效、时效关系;除6 h干预组外,余各组阿司匹林均可抑制VEGF、β-catenin蛋白和mRNA的表达（P＜0.05）。结论 阿司匹林对人结直肠癌细胞株SW480、HT-29的生长增殖具有显著的抑制作用,并对SW480、HT-29中VEGF、β-catenin mRNA和蛋白质的表达具有显著的下调效应;而阿司匹林通过抑制β-catenin的表达,同时调节VEGF抑制肿瘤血管的生成可能是其预防和治疗结直肠癌的作用机制之一。     

miR-302a对结直肠癌细胞奥沙利铂化疗敏感性的影响及机制

目的:探究miR-302a对结直肠癌细胞奥沙利铂化疗敏感性的影响及机制。方法:在四株结直肠癌细胞系HT29、HCT8、SW480、SW1463中,通过转染miR-302a mimic构建miR-302a过表达模型,RT-PCR检测过表达效果;CCK-8法检测转染48 h后高表达miR-302a细胞的增殖能力及对奥沙利铂的敏感性;蛋白质印迹法检测转染后P-gp蛋白及Wnt/β-catenin通路相关蛋白MMP-7、c-Jun、c-myc、β-catenin、LEF1的变化。结果:相比正常小肠上皮细胞HIEC,miR-302a在结直肠癌细胞系HT29、HCT8、SW480、SW1463中的表达较低。转染mimic后,miR-302a的表达明显上调（P<0.001）。增殖实验发现miR-302a的上调并不影响结直肠癌细胞的增殖,而在转染miR-302a的细胞中加入奥沙利铂,miR-302a组HT29、HCT8、SW480和SW1463细胞存活率相比miR-NC组分别降低2.46、1.89、2.39、2.86倍。进一步探究miR-302a增加奥沙利铂敏感性的机制,发现miR-302a可抑制P-gp蛋白的表达,并且抑制Wnt/β-catenin通路相关蛋白MMP-7、c-Jun、c-myc、β-catenin、LEF1的表达。结论:miR-302a可增加结直肠癌细胞奥沙利铂化疗敏感性,其机制可能是通过抑制P-gp的蛋白表达,并抑制Wnt/β-catenin信号通路相关蛋白表达而实现。     

单用TAM及联合应用5-FU对结肠癌细胞株生长抑制作用及增殖凋亡的影响

目的探讨他莫昔芬(tamoxifen,TAM)单独或联合5-FU化疗对结肠癌细胞株生长抑制作用及凋亡的影响.方法应用MTT法,比较单纯应用TAM和TAM与5-FU联合对SW480、HT29细胞株生长抑制作用,通过药物量-效关系曲线,观察TAM有无化疗增敏作用,同时检测PCNA和AI,探讨TAM联合5-FU对增殖、凋亡的影响.结果单独应用TAM对SW480、HT29细胞株无生长抑制作用;TAM联合5-FU在一定浓度时可抑制SW480和HT29细胞的生长,提高对5-FU的敏感性,起到化疗增敏作用.通过对PCNA和AI 2个指标的检测,随着浓度的增加和时间的延长,TAM联合5-FU抑制细胞的增殖和促进细胞的凋亡均呈上升趋势.结论一定浓度的TAM能增加人结肠癌细胞株SW480、HT29对化疗药物5-FU的敏感性,抑制细胞增殖,促进细胞凋亡.     

G6PD对大肠癌细胞生长侵袭的影响及其与HKⅡ的相关性

目的 探讨G6PD对大肠癌HCT116和SW480细胞生长侵袭的影响,以及G6PD与HKⅡ在大肠癌及其癌旁上皮组织中的表达和两者的相关性。方法 将体外培养的大肠癌HCT116和SW480细胞进行G6PD过表达和干扰处理。Western blot法检测细胞中G6PD和HKⅡ的蛋白表达水平;流式细胞术分析细胞周期进程;葡萄糖氧化酶法检测培养液中葡萄糖的含量;划痕实验检测细胞侵袭能力;免疫组织化学法检测大肠癌及癌旁组织中G6PD与HKⅡ蛋白的表达水平。结果 过表达实验中,与Flag转染组相比,Flag-G6PD转染组HCT116和SW480两种细胞培养液中葡萄糖浓度、S期所占比例及侵袭能力均无明显变化;干扰实验中,与阴性对照转染组相比,G6PD-Homo-1504转染组两种细胞的葡萄糖浓度显著升高,S期所占比例和侵袭能力显著降低。G6PD与HKⅡ表达水平呈正相关。结论 干扰G6PD减少了大肠癌细胞葡萄糖的消耗,抑制了细胞的增殖和侵袭能力;同时G6PD对HKⅡ可能存在调控作用。     

Dual antitumor effects of 5-fluorouracil on the cell cycle in colorectal carcinoma cells: a novel target mechanism concept for pharmacokinetic modulating chemotherapy

5-Fluorouracil (5-FU) is one of the most widely used anticancer agents for advanced colorectal carcinoma, but its response rate is only 15%. The "pharmacokinetic modulating chemotherapy" (PMC) regimen that we have advocated has proved to be highly effective in treating colorectal carcinoma. PMC consists of a continuous i.v. infusion of 5-FU over 24 h for 1day a week at 600 mg/m2/day, and an oral dose of uracil-tegafur (UFT), a 5-FU derivative, at 400 mg/day for 5-7 days per week, repeated every week for more than 6 months. Assays of 5-FU in 23 patients receiving this treatment showed serum concentrations ranging from 88 to 1,323 ng/ml. We then analyzed the effects of clinically relevant concentrations of 5-FU found in colorectal cancer patients treated with the PMC regimen on the growth of three human colorectal adenocarcinoma cell lines, SW480 and COLO320DM (mutant p53) and HCT116 (wild-type p53). Exposure of these three cell lines to 5-FU resulted in growth inhibition in a dose-dependent manner. Exposure to 100 ng/ml of 5-FU in SW480 and COLO320DM caused G1 arrest after 24 h and G2 arrest after 72-144 h, and only a minority of the cell population showed apoptotic features, which indicated that most of the cells were killed through mitotic catastrophe, nonapoptotic cell death. On the contrary, exposure to 1000 ng/ml of 5-FU in SW480 and COLO320DM resulted in G1-S-phase arrest and the induction of apoptosis throughout the experimental period. Nuclear cyclin B1 expression was markedly induced with exposure to 100 ng/ml of 5-FU in SW480 and COLO320DM; and expression of 14-3-3sigma protein, a cell cycle inhibitor in the GG phase, was induced in SW480. ICT116 responded to lower concentrations of 5-FU more rapidly: G2 arrest was seen after 24-72 h of exposure to 10 ng/ml of 5-FU, and G,1rrest was seen after 12-24 h of exposure to 100 ng/ml. These results show that 5-FU acts via two different pathways, depending on dose: (a) G,1S-phase cell cycle arrest and apoptosis at 1,000 ng/ml in SW480 and COLO320DM, and 100 ng/ml in HCT116; and (b) G2-M-phase cell cycle arrest and mitotic catastrophe at 100 ng/ll in SW480 and COLO320DM, and 10 ng/ml in HCT116. These results suggest that the efficacy of our PMC regimen is based on targeting at least two different phases of the cell cycle. In our clinical trial, we showed efficacy independent of p53 status, ascertained by cell kinetic analysis in vitro, which may lead to a novel concept of schedule-oriented biochemical modulation of this drug.     

The rapamycin-sensitive signal transduction pathway as a target for cancer therapy.

The high frequency of mutations in cancer cells which result in altered cell cycle regulation and growth signal transduction, conferring a proliferative advantage, indicates that many of these aberrant mechanisms may be strategic targets for cancer therapy. The macrolide fungicide rapamycin, a natural product with potent antimicrobial, immunosuppressant, and anti-tumor properties, inhibits the translation of key mRNAs of proteins required for cell cycle progression from G1 to S phase. Rapamycin binds intracellularly to the immunophilin FK506 binding protein 12 (FKBP12), and the resultant complex inhibits the protein kinase activity of a protein kinase termed mammalian target of rapamycin (mTOR). The inhibition of mTOR, in turn, blocks signals to two separate downstream pathways which control the translation of specific mRNAs required for cell cycle traverse from G1 to S phase. Blocking mTOR affects the activity of the 40S ribosomal protein S6 kinase (p70s6k) and the function of the eukaryotic initiation factor 4E-binding protein-1 (4E-BP1), leading to growth arrest in the the G1 phase of the cell cycle. In addition to its actions on p70s6k and 4E-BP1, rapamycin prevents cyclin-dependent kinase activation, inhibits retinoblastoma protein (pRb) phosphorylation, and accelerates the turnover of cyclin D1 that leads to a deficiency of active cdk4/cyclin D1 complexes, all of which can inhibit cell cycle traverse at the G1/S phase transition. Both rapamycin and CCI-779, an ester analog of rapamycin with improved pharmaceutical properties and aqueous solubility, have demonstrated impressive activity against a broad range of human cancers growing in tissue culture and in human tumor xenograft models, which has supported the development of compounds targeting rapamycin-sensitive signal-transduction pathways. CCI-779 has completed several phase I clinical evaluations and is currently undergoing broad disease-directed efficacy studies. The agent appears to be well tolerated at doses that have resulted in impressive anti-tumor activity in several types of refractory neoplasms. Important challenges during clinical development include the definition of a recommended dose range associated with optimal biological activity and maximal therapeutic indices, as well as the ability to predict which tumors will be sensitive or resistant to CCI-779.     

α4在化学致癌物诱导细胞转化中的作用

目的：探讨α4在化学致癌物诱导细胞转化中的可能作用。方法：采用免疫印迹检测化学致癌物诱导既往转化细胞模型和肝肿瘤细胞株中α4的表达水平，再利用病毒感染法在肝永生化细胞株L02R上构建α4高表达（L02R-α4）和低表达（L02R-SHα4）的细胞株，检测其细胞生长速度和转化能力。进一步选择已建立的细胞株、化学致癌物AFB1诱导转化的细胞（L02RT-AFB1）及肝肿瘤细胞株HepG2和SMMC等，在有或无mTOR通路抑制剂雷帕霉素处理下，通过免疫印迹检测mTOR下游两个分子p70S6K1和4E-BP1的表达及磷酸化水平。结果：在化学致癌物诱导转化的细胞模型和肝肿瘤细胞株中发现α4的表达比对照细胞上调1.9~5.9倍。蛋白印迹结果证实L02R-α4和L02R-SHα4细胞株构建成功，α4表达上调能够促进L02R细胞增殖并发生转化（P＜0.05）。在α4高表达的转化细胞L02R-α4中，p70S6K1和4E-BP1呈高磷酸化状态。当有雷帕霉素作用时，所有细胞中p70S6K1和4E-BP1的磷酸化水平明显下降，在L02R-SHα4细胞中下降尤为显著。结论：α4具有癌基因功能，α4的异常上调激活mTOR通路，促进细胞增殖并诱导细胞恶性转化。     

Mammalian target of rapamycin and S6 kinase 1 positively regulate 6-thioguanine-induced autophagy

DNA mismatch repair (MMR) ensures the fidelity of DNA replication and is required for activation of cell cycle arrest and apoptosis in response to certain classes of DNA damage. We recently reported that MMR is also implicated in initiation of an autophagic response after MMR processing of 6-thioguanine (6-TG). It is now generally believed that autophagy is negatively controlled by mammalian target of rapamycin (mTOR) activity. To determine whether mTOR is involved in 6-TG-induced autophagy, we used rapamycin, a potential anticancer agent, to inhibit mTOR activity. Surprisingly, we find that rapamycin cotreatment inhibits 6-TG-induced autophagy in MMR-proficient human colorectal cancer HCT116 (MLH1(+)) and HT29 cells as measured by LC3 immunoblotting, GFP-LC3 relocalization, and acridine orange staining. Consistently, short interfering RNA silencing of the 70-kDa ribosomal S6 kinase 1 (S6K1), the downstream effector of mTOR, markedly reduces 6-TG-induced autophagy. Furthermore, we show that inhibition of mTOR by rapamycin induces the activation of Akt as shown by increased Akt phosphorylation at Ser(473) and the inhibition of 6-TG-induced apoptosis and cell death. Activated Akt is a well-known inhibitor of autophagy. In conclusion, our data indicate that mTOR-S6K1 positively regulates autophagy after MMR processing of 6-TG probably through its negative feedback inhibition of Akt.     

Insulin-like growth factor-I has different effects on myogenin induction and cell cycle progression in human alveolar and embryonal rhabdomyosarcoma cells

Alveolar rhabdomyosarcoma (RMS) has a much poorer outcome than embryonal RMS. In this study, we found that IGF-I affected the induction of myogenin and cell cycle progression in alveolar RMS cells, but not in embryonal RMS cells. IGF-I enhanced the induction of myogenin protein in alveolar RMS SJ-Rh30 and KP-RMS-MS cells as it did in myoblast C2C12 cells, but not in embryonal RMS RD or KP-RMS-KH cells. IGF-I induction of myogenin protein was blocked by anti-IGF-IR monoclonal antibody alphaIR-3 and the mTOR-specific inhibitor rapamycin. In Rh30mTOR-rr cells, which stably express a rapamycin-resistant mutant mTOR, rapamycin did not inhibit IGF-I induction of myogenin protein. These data suggest that IGF-I induces myogenin in alveolar RMS cells through the IGF-IR/mTOR pathway. In C2C12 cells, IGF-I induces myogenin protein followed by cell cycle arrest leading to myogenic differentiation. IGF-I promoted G1-S cell cycle progression without any signs of terminal differentiation in alveolar RMS cells. On the other hand, IGF-I promoted neither cell cycle arrest nor G1-S cell cycle progression in embryonal RMS cells. In alveolar RMS SJ-Rh30 cells, 4E-BP1, one of two effectors downstream of mTOR, was continuously hyperphosphorylated by IGF-I, whereas in embryonal RMS RD cells, 4E-BP1 was only transiently hyperphosphorylated. These findings suggest that the different effects of IGF-I on myogenin induction and cell cycle progression in alveolar and embryonal RMS cells are due to a difference of phosphorylation status of 4E-BP1. These different responses to IGF-I help to explain immunohistochemical and clinical behavioral differences between alveolar and embryonal RMS.     

Longitudinal inhibition of PI3K/Akt/mTOR signaling by LY294002 and rapamycin induces growth arrest of adult T-cell leukemia cells

This study found that phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling was activated in human T-cell lymphotropic virus type I (HTLV-1)-infected leukemia cells. Rapamycin (1-100 nM, 48h), the inhibitor of mTOR and its analog RAD001 (1-100 nM, 48 h)-induced growth inhibition and G0/G1 cell cycle arrest of these cells in association with de-phosphorylation of p70S6K and 4E-BP-1, although IC50 was not achieved. Paradoxically, rapamycin-stimulated phosphorylation of Akt at Ser473. Blockade of Akt signaling by the PI3K inhibitor LY294002 (1-20 microM, 48 h) also resulted in the growth inhibition and G0/G1 cell cycle arrest of HTLV-1-infected cells, with IC50 ranging from 5 to 20muM, and it caused de-phosphorylation of p70S6K and 4E-BP-1. Of note, when rapamycin was combined with LY294002, rapamycin-induced phosphorylation of Akt was blocked, and the ability of rapamycin to induce growth arrest of HTLV-1-infected T-cells and suppress the p-p70S6K and p-4E-BP-1 proteins was potentiated. Moreover, both LY294002 and rapamycin down-regulated the levels of c-Myc and cyclin D1 proteins in these cells, and their combination further decreased levels of these cell cycle-regulating proteins. Taken together, longitudinal inhibition of PI3K/Akt/mTOR signaling represents a promising treatment strategy for individuals with adult T-cell leukemia.     

Fibronectin stimulates non-small cell lung carcinoma cell growth through activation of Akt/mammalian target of rapamycin/S6 kinase and inactivation of LKB1/AMP-activated protein kinase signal pathways

The Akt/mammalian target of rapamycin (mTOR)/ribosomal protein S6 kinase (p70S6K) pathway is considered a central regulator of protein synthesis and of cell proliferation, differentiation, and survival. However, the role of the Akt/mTOR/p70S6K pathway in lung carcinoma remains unknown. We previously showed that fibronectin, a matrix glycoprotein highly expressed in tobacco-related lung disease, stimulates non-small cell lung carcinoma (NSCLC) cell growth and survival. Herein, we explore the role of the Akt/mTOR/p70S6K pathway in fibronectin-induced NSCLC cell growth. We found that fibronectin stimulated the phosphorylation of Akt, an upstream inducer of mTOR, and induced the phosphorylation of p70S6K1 and eukaryotic initiation factor 4E-binding protein 1 (4E-BP1), two downstream targets of mTOR in NSCLC cells (H1792 and H1838), whereas it inhibited the phosphatase and tensin homologue deleted on chromosome 10, a tumor suppressor protein that antagonizes the phosphatidylinositol 3-kinase/Akt signal. In addition, treatment with fibronectin inhibited the mRNA and protein expression of LKB1 as well as the phosphorylation of AMP-activated protein kinase (AMPKalpha), both known to down-regulate mTOR. Rapamycin, an inhibitor of mTOR, blocked the fibronectin-induced phosphorylation of p70S6K and 4E-BP1. Akt small interfering RNA (siRNA) and an antibody against the fibronectin-binding integrin alpha5beta1 also blocked the p70S6K phosphorylation in response to fibronectin. In contrast, an inhibitor of extracellular signal-regulated kinase 1/2 (PD98095) had no effect on fibronectin-induced phosphorylation of p70S6K. Moreover, the combination of rapamycin and siRNA for Akt blocked fibronectin-induced cell proliferation. Taken together, these observations suggest that fibronectin-induced stimulation of NSCLC cell proliferation requires activation of the Akt/mTOR/p70S6K pathway and is associated with inhibition of LKB1/AMPK signaling.     

Oncogenic tyrosine kinase NPM/ALK induces activation of the rapamycin-sensitive mTOR signaling pathway

The mechanisms of cell transformation mediated by the nucleophosmin (NPM)/anaplastic lymphoma kinase (ALK) tyrosine kinase are only partially understood. Here, we report that cell lines and native tissues derived from the NPM/ALK-expressing T-cell lymphoma display persistent activation of mammalian target of rapamycin (mTOR) as determined by phosphorylation of mTOR targets S6rp and 4E-binding protein 1 (4E-BP1). The mTOR activation is serum growth factor-independent but nutrient-dependent. It is also dependent on the expression and enzymatic activity of NPM/ALK as demonstrated by cell transfection with wild-type and functionally deficient NPM/ALK, small interfering RNA (siRNA)-mediated NPM/ALK depletion and kinase activity suppression using the inhibitor WHI-P154. The NPM/ALK-induced mTOR activation is transduced through the mitogen-induced extracellular kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathway and, to a much lesser degree, through the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway. Accordingly, whereas the low-dose PI3K inhibitor wortmannin and Akt inhibitor III profoundly inhibited Akt phosphorylation, they had a very modest effect on S6rp and 4E-BP1 phosphorylation. In turn, MEK inhibitors U0126 and PD98059 and siRNA-mediated depletion of either ERK1 or ERK2 inhibited S6rp phosphorylation much more effectively. Finally, the mTOR inhibitor rapamycin markedly decreased proliferation and increased the apoptotic rate of ALK+TCL cells. These findings identify mTOR as a novel key target of NPM/ALK and suggest that mTOR inhibitors may prove effective in therapy of ALK-induced malignancies.     

Determinants of rapamycin sensitivity in breast cancer cells.

PURPOSE: Rapamycin inhibits the serine-threonine kinase mammalian target of rapamycin (mTOR), blocking phosphorylation of p70 S6 kinase (S6K1) and 4E-binding protein 1 (4E-BP1) and inhibiting protein translation and cell cycle progression. Rapamycin and its analogues are currently being tested in clinical trials as novel-targeted anticancer agents. Although rapamycin analogues show activity in clinical trials, only some of the treated patients respond. The purpose of this study is to identify determinants of rapamycin sensitivity that may assist the selection of appropriate patients for therapy. EXPERIMENTAL DESIGN: Breast cancer cell lines representing a spectrum of aberrations in the mTOR signaling pathway were tested for rapamycin sensitivity. The expression and phosphorylation state of multiple components of the pathway were tested by Western blot analysis, in the presence and absence of rapamycin. RESULTS: Cell proliferation was significantly inhibited in response to rapamycin in 12 of 15 breast cancer cell lines. The ratio of total protein levels of 4E-BP1 to its binding partner eukaryotic initiation factor 4E did not predict rapamycin sensitivity. In contrast, overexpression of S6K1, and phosphorylated Akt independent of phosphatase and tensin homologue deleted from chromosome 10 status, were associated with rapamycin sensitivity. Targeting S6K1 and Akt with small interfering RNA and dominant-negative constructs, respectively, decreased rapamycin sensitivity. Rapamycin inhibited the phosphorylation of S6K1, ribosomal S6 protein, and 4E-BP1 in rapamycin-resistant as well as -sensitive cells, indicating that its ability to inhibit the mTOR pathway is not sufficient to confer sensitivity to rapamycin. In contrast, rapamycin treatment was associated with decreased cyclin D1 levels in the rapamycin-sensitive cells but not in rapamycin-resistant cells. CONCLUSIONS: Overexpression of S6K1 and expression of phosphorylated Akt should be evaluated as predictors of rapamycin sensitivity in breast cancer patients. Furthermore, changes in cyclin D1 levels provide a potential pharmacodynamic marker of response to rapamycin.