结直肠癌细胞IL-4／Stat6信号传导活性与调节基因差异性表达相关性研究

目的：IL-4介导的Star6信号传导活性在人细胞之间有差异，称为Stat6活化表型。旨在探讨Stat6活化表型及其产生的分子学基础。方法：结直肠癌细胞株HT-29与Caco-2的Star6活化表型用EMSA半定量法测定。Stat6通路调节因子基因水平的表达用RT-PCR法检测。蛋白水平的表达用Western blotting法检测。结果：EMSA分析表明，HT29为高活化表型（Star6^high）而Caco2为零活化表型（Star6^null）。RT-PCR分析显示，与Star6^high HT-29比较，Star6^null Caco-2癌细胞高表达负调节基因SOCS1和SHP1，而低表达正调节因子PP2A催化亚单位编码基因PP2CA和PP2CB。Westernb lotting分析法证实Caco-2癌细胞高表达SOCS1和SHP1蛋白。结论：Star6通路正、负调节基因的表达失衡可能是产生不同Star6活化表型的分子机制之一。     

恩度联合化疗对不同Stat6活化表型直结肠癌细胞的作用

目的研究恩度联合化疗对直结肠癌细胞的抑制作用,并进一步观察不同Stat6表型的直结肠癌细胞对恩度联合化疗药物敏感性的差异。方法采用MTT法检测不同浓度的恩度单药或联合5-Fu及奥沙利铂对2种不同Stat6活化表型的直结肠癌细胞(Caco-2和HT-29)的增殖抑制作用。用流式细胞仪检测不同药物处理组对2种直结肠癌细胞早期凋亡率的影响。结果恩度单药作用于Caco-2和HT-29细胞没有显示出明显的增殖抑制和凋亡促进的作用(P>0.05)。而恩度联合1种或2种化疗药物[(5-Fu)和奥沙利铂(OXP)]对这2种癌细胞的生长抑制和凋亡促进的能力明显升高(P<0.05和P<0.01)。恩度联合化疗药物对Caco-2细胞生长抑制率和早期凋亡率均高于HT-29细胞(P<0.05)。结论恩度联合化疗药物能更好的抑制直结肠癌细胞的增殖能力,不同Stat6活化状态可能成为评价化疗疗效的潜在指标之一。     

不同Stat6表型乳腺癌细胞IL-4/Stat6信号通路调节基因表达的研究

目的:探讨不同乳腺癌细胞株Stat6活化分型的可行性及IL-4的作用机制.方法:流式细胞仪测定不同Stat6表型细胞株ZR-75-1和BT-20的早期凋亡率;应用Affymetrix基因芯片测定IL-4刺激前后的基因表达谱变化.结果:Stat6null表型细胞与Stat6high相比早期凋亡增加(40%vs 12%);在Star6null细胞株有2 193个基因/转录产物表达升高,而Stat6high细胞株中2 600个基因/转录产物表达升高,且Stat6high细胞和Stat6null细胞中与凋亡和转移相关的基因表达谱明显不同;但不论在Stat6high还是Stat6null细胞株,IL-4均上调CCL26、SOCS1、CISH、EGLN3和SIDT1基因,而下调DUSP1、FOS和FOSB基因.结论:在乳腺癌细胞中,IL-4可能像在免疫细胞中一样,通过Stat6或非Stat6途径而发挥功能.     

NGX6对结肠癌细胞系HT-29基因表达谱的影响

背景与目的:结肠癌是最常见的恶性肿瘤之一,其发病机制仍未完全明了。本研究在前期工作的基础上探讨候选抑瘤基因NGX6对结肠癌细胞系HT-29基因表达谱的影响。方法:通过脂质体介导的基因转染构建稳定表达NGX6的结肠癌细胞系pcDNA3.1( )/NGX6/HT-29,以NGX6转染组为实验组,空白质粒转染组为对照组,利用高通量的表达谱芯片BiostarH-80sx1筛选差异表达基因,RT-PCR验证部分基因芯片的实验结果。结果:NGX6基因转染结肠癌细胞系HT-29后引起该细胞系基因表达谱广泛地改变,其中表达差异3倍以上的基因共377个,这些差异表达基因的功能涉及多个方面,包括细胞信号转导﹑细胞周期调控﹑细胞凋亡﹑细胞骨架和运动﹑基因转录和翻译、DNA损伤修复﹑蛋白质合成和代谢等。其中包括一些非常重要的信号转导通路上的分子改变,如Wnt/β-catenin信号通路上的DKK1、ILK、MMP1、COL11A1,ILK信号通路上的ILK,Eph-Ephrins信号通路上的EpHB2,RhoA信号通路上的ROCK2,RanGTPase信号通路上的RANBP1,以及RB/RBBP1信号通路上的RBBP1等。结论:NGX6转染引起了一些非常重要的信号转导通路上的分子改变,可能通过参与调节这些信号转导通路而发挥其抗肿瘤增殖和转移的作用。     

siRNA阻断Stat3信号促进食管鳞癌细胞株凋亡

目的：研究RNA干扰技术沉默Stat3基因对食管鳞癌细胞（EC9706）中持续性激活Stat3信号的阻断作用及对细胞凋亡的影响。方法：将化学合成的100nM的Stat3 siRNA转染EC9706细胞,RT-PCR检测转染前后Stat3 mRNA的表达,Western blot检测转染前后细胞中Bcl-2、Stat3及磷酸化Stat3（p-Stat3）蛋白的表达,凝胶电泳迁移率（EMSA）检测转染前后活化Stat3蛋白的DNA结合活性,流式细胞术检测转染前后细胞凋亡的改变情况。结果：Stat3 siRNA转染细胞48h后细胞形态发生明显的改变,RT-PCR及Western blot结果显示Stat3 siRNA干扰后Stat3mRNA及蛋白表达均受到明显抑制, Stat3信号的激活被阻断,活化Stat3蛋白的核结合活性显著下降。转染后细胞中Bcl-2蛋白的表达明显减少。流式细胞术结果证明Stat3 siRNA可明显促进细胞凋亡。结论：Stat3 siRNA能够特异地阻断食管鳞癌细胞中Stat3 信号的持续性激活并促进肿瘤细胞凋亡。     

SOCS家族分子在肿瘤发生发展中的作用

细胞因子信号转导抑制分子（suppressor of cytokine signaling, SOCS）是一类在细胞信号转导过程中发挥重要作用的负调控因子,家族成员一共有8个,主要通过抑制JAK-STAT信号通路的持续激活而调节细胞的增殖、分化和凋亡。在肿瘤的发生发展过程中,由于SOCS家族基因启动子区CG岛超甲基化、组蛋白异常乙酰化、基因突变、基因缺失等原因导致的SOCS蛋白表达异常,使JAK-STAT被持续活化,从而导致肿瘤的发生发展与转移。本文综述了SOCS家族的发现,成员构成及分子结构,各结构域的功能及其在肿瘤发生发展等方面的最新进展。由于SOCS在肿瘤发生、发展方面的重要作用,SOCS分子作为信号转导途径重要的负调节因子发挥肿瘤抑制作用,使其成为肿瘤治疗的新靶标。     

改变细胞膜脂肪酸组成防治大肠癌的基因治疗研究*

目的:利用脂肪酸去饱和酶基因fat- 1 改变细胞膜脂肪酸组成,进行大肠癌的基因治疗研究。方法:将fat- 1 基因插入腺病毒载体中,与骨架载体同源重组,构建腺病毒重组载体（Ad-GFP-fat1）,通过包装细胞系（293）产生的腺病毒,感染人大肠癌株HT- 29细胞。提取细胞的总RNA,以fat- 1 基因的反义mRNA 作探针,用Northern Blot检测fat- 1 基因在HT- 29细胞内的表达。以流式细胞仪对HT- 29细胞G0/G1 期、S 期、G2/M期所占比例进行检测,分析fat- 1 基因对HT- 29细胞增殖和凋亡的影响。以气相色谱分析仪分析fat- 1 基因对HT- 29细胞细胞膜n-6 PUFAs 和n-3 PUFAs 含量及n-6/n- 3PUFAs 比例的影响。将HT- 29细胞皮下接种于裸鼠右前肢腋下,建立裸鼠HT- 29大肠癌细胞皮下移植瘤模型。成瘤后进行治疗实验,经连续5 次治疗,于最后一次治疗后第3 天处死小鼠,取肿瘤称重。分析fat- 1 基因裸鼠体内抗肿瘤效果。结果:通过基因重组技术,得到高滴度的含fat- 1 基因的重组病毒;腺病毒介导的fat- 1 基因能够在HT- 29细胞中有效表达;fat- 1 基因的表达可降低HT- 29细胞膜n-6/n- 3PUFAs 的比例,有效抑制HT- 29细胞增殖,促进细胞凋亡并能抑制裸鼠移植瘤的发展。结论:fat- 1 基因的表达,可抑制HT- 29细胞的体内外增殖并诱导细胞凋亡,在大肠癌基因治疗中可能具有良好利用价值。      

苦参碱通过bcr-abl介导的MEK-ERK通路抑制人慢性粒细胞白血病K562细胞增殖

目的：探讨MEK-ERK通路在苦参碱抑制人慢性粒细胞白血病K562细胞增殖中的分子机制。方法采用Western blot法检测K562细胞内MEK-ERK通路关键分子MEK1、ERK1／2及其上游接头分子Shc、SHP2的总蛋白和磷酸化蛋白的表达;采用反转录聚合酶链反应（RT-PCR）和Western blot检测bcr-abl及有丝分裂原激活的蛋白激酶（MAPK）下游靶蛋白bcl-xL、Cyclin D1、c-myc及p27在转录及蛋白水平的表达。结果苦参碱可明显抑制K562细胞内MEK1、ERK1／2及Shc、SHP2的磷酸化表达,并可在转录及蛋白水平抑制bcr-abl分子表达。同时,RT-PCR和Western blot实验证实,苦参碱处理后,K562细胞内bcl-xL、Cyclin D1、c-myc表达均明显抑制,细胞周期负调控蛋白p27的表达增加。结论苦参碱对K562细胞的抑制效应与bcr-abl介导的MEK-ERK信号通路活性抑制有关,对信号通路中磷酸化蛋白或激酶分子活性的调控可能是其调控MEK-ERK通路活性的重要分子机制。     

PPARγ活化诱导细胞凋亡和周期阻滞来抑制结肠癌细胞生长

目的探讨过氧化物酶体增殖物激活受体γ(peroxisome proliferator activated receptorγ,PPARγ)在结肠癌细胞株HT-29中的表达及其活化后对结肠癌细胞生长的影响。方法通过RT-PCR和Western blot检测HT-29中PPARγmRNA及蛋白质的表达,四甲基偶氮唑盐(MTT)微量酶反应比色法检测PPARγ配体罗格列酮(rosiglitazone,Rosi)和15d-PGJ2对HT-29细胞生长的影响,荧光显微镜、TUNEL法观察Rosi和15d-PGJ2激活PPARγ后诱导HT-29细胞凋亡形态和生化改变,流式细胞仪(FCM)以碘化丙啶(PI)单染法检测细胞周期。结果RT-PCR及Western blot检测结果表明结肠癌细胞HT-29中存在PPARγmRNA及蛋白质的表达。MTT结果显示Rosi和15d-PGJ2可抑制HT-29细胞生长,且具有时间、剂量依赖效应。荧光显微镜、TUNEL检测显示PPARγ活化后HT-29细胞出现典型的凋亡现象,10μmol/L Rosi或15d-PGJ2作用48h后的细胞凋亡率分别为(17.3±1.9)%及(20.8±2.9)%,与对照组(3.86±0.49)%相比差异均具有统计学意义(P<0.05)。FCM结果显示Rosi和15d-PGJ2激活PPARγ后诱导细胞周期阻滞于G0/G1期,与对照组相比差异有统计学意义(P<0.05)。结论结肠癌细胞HT-29表达PPARγ,其活化可通过诱导细胞凋亡及细胞周期阻滞,抑制结肠癌细胞增长。因此,PPARγ可能为结肠癌治疗的一个新靶点。     

胞黏蛋白对结直肠癌细胞增殖的影响及作用机制的初步探讨

目的:探讨胞黏蛋白在人结直肠癌细胞增殖中的作用及可能的作用机制.方法:分别采用RT-PCR法和免疫荧光法检测结直肠癌HT-29、HCT-116、SW620和SW480细胞中胞黏蛋白的表达情况.MTT法检测阻断剂SecinH3阻断胞黏蛋白,或小分子干扰RNA(small interfering RNA,siRNA)干扰胞黏蛋白-2(ARNO)表达后对HT-29细胞增殖的影响.蛋白质印迹法检测SecinH3阻断或ARNO-siRNA干扰对HT-29细胞中表皮生长因子受体(epidermal growth factor receptor,EGFR)通路分子激活情况的影响,对HCT-116细胞中胰岛素样生长因子Ⅰ型受体(insulin-like growth factor type Ⅰ receptor,IGF-IR)通路分子激活情况的影响.结果:胞黏蛋白的4个亚型在HT-29、HCT-116、SW620和SW480细胞中均有表达:其中以ARNO的表达量较高;SecinH3处理HT-29细胞后使细胞生长受到抑制,作用72 h后细胞增殖抑制率达(57.22±1.01)％,ARNO- siRNA干扰ARNO蛋白的表达亦能使该肿瘤细胞的增殖受到抑制,ARNO- siRNA转染HT-29细胞48 h后,其细胞增殖抑制率为(58.95±3.42)％.蛋白质印迹法检测结果提示,阻断剂SecinH3及ARNO-siRNA均能下调结直肠癌细胞中ARNO蛋白的表达,使HT-29细胞中EGFR信号通路、HCT-116细胞中的IGF-IR信号通路受到抑制,其相应的下游信号通路因子亦出现明显的下调.结论:胞黏蛋白与EGFR或IGF-IR信号通路的活化具有相关性,其有可能成为结直肠癌治疗的一个新的靶点.     

Phenotyping of IL4-induced nuclear Stat6 activity in humans: quantitation after gel shift assay using immortalized cell lines

The IL4-induced Stat6 signaling pathway is active in a variety of cell types, including different cancer cells, and plays an important role in the regulation of gene expression, such as CD23. There are large quantitative differences in DNA-binding activity of IL4-induced Stat6, which are useful for phenotyping activated Stat6 in normal and disease status. However, quantitation of activated Stat6 is challenging and a standardized methodology is needed. Here we have developed a semi-quantitative methodology using gel shift assay in which IL4-induced nuclear Stat6 activities are measured in human EBV-transformed lymphoblastoid cell lines. Using a DNA probe with high affinity Stat6-binding N4 motif and a specific antibody to Stat6, autoradiographs of EMSA gels are recorded by a scan imager and OD readings of antibody super-shifted Stat6 complex bands are obtained. OD readings of all test cell lines are referenced to that of a standard cell line placed in every single experiment and an OD ratio is obtained for each test cell, which allows assignment of Stat6 activational phenotypes. Using this methodology, we have been able to define three Stat6 activational phenotypes termed as Stat6high (intense banding), Stat6low (medium intensity banding), and Stat6null (very low to no discernible banding). These Stat6 phenotypes correlate well with levels of CD23 expression, but not with those of HLA-DR. Pedigree analysis has revealed a Mendelian inheritance pattern for Stat6 phenotypes. The methodology is useful in association studies in human cancer and autoimmune diseases. The Stat6null phenotype may result from a defect in Stat6 signaling which has important implications with respect to the pathogenesis of cancer and Th1/Th2 cytokine imbalance in general. In addition, the defective Stat6null lines discovered here may serve as a natural human model for comprehensive study in the same way as a Stat6 knockout null animal model does.     

Human B lymphoblast cell lines defective of Stat6 signaling produce high levels of proinflammatory cytokines IL-12, TNFalpha and IFNgamma

Based on Stat6 gene knockout animal models, the Stat6 signaling pathway has been suggested to play a role in carcinogenesis and Th1/Th2 cytokine balance. Using a semiquantitative EMSA assay and EBV-transformed human B lymphoblast cell lines, we have previously identified three Stat6 activational phenotypes, termed as Stat6high, Stat6low, and Stat6null. A genetic mechanism has been proposed which determines the IL-4-induced activation of the human Stat6 signaling. With respect to the contribution of variant phenotypes to human disease, we further hypothesize that the Stat6null phenotype may result from a partial defect in Stat6 signaling which resembles Stat6 knockout animals in several functional aspects. The characterization of the human Stat6null phenotype stably displayed by the EBV-B cell lines is easily assailable and possesses important implications with respect to Th1/Th2 cytokine imbalance in diseases such as cancer development/metastasis and inflammatory diseases. In this study, we have extended our investigation to the downstream regulatory consequences associated with these Stat6 phenotypes. Production of three important proinflammatory cytokines, IL-12, TNFalpha and IFNgamma was examined in spontaneous EBV-B cell culture using ELISA methodology. Individual cell lines defined as Stat6null produced significantly higher levels of IL-12, TNFalpha and IFNgamma on day 4 in spontaneous culture in comparison with cell lines characterized as Stat6high and Stat6low. These observations of the human Stat6null phenotype, together with those accruing from Stat6 knockout mouse model studies, suggest that the Stat6 signaling pathway may play a role in maintaining the Th1/Th2 cytokine balance by directly and indirectly down-regulating the production of proinflammatory cytokines, a regulatory process which appears to go awry in inflammatory diseases. Moreover, observations from signal transduction studies in our human B lymphocyte model may be compatible with those in the chosen mouse B lymphocyte for establishing signaling networks by the Alliance for Cellular Signaling (AfCS).     

Aberrant Stat3 signaling by interleukin-4 in malignant glioma cells: involvement of IL-13Ralpha2

Interleukin (IL)-4 exhibits antitumor activity in rodent experimental gliomas, which is likely mediated by the actions of IL-4 on a variety of immune cells present in and around the tumor masses. Here, we show that IL-4, which activates Stat6 in normal human astrocytes and in a variety of other cells, induces an aberrant activation of Stat3 in glioblastoma multiforme (GBM) cells but not in normal human astrocytes. Previously, we have shown that autocrine IL-6 signaling induces a persistent activation of Stat3. Now, we show that Stat3 is further activated by IL-4 stimulation of GBM cells. Expression of IL-13Ralpha2, a decoy receptor for IL-13 that partly blocks IL-4-mediated activation of Stat6 in GBM cells, up-regulates the activation of Stat3 as shown by a small interfering RNA-mediated inhibition of IL-13Ralpha2 expression. In addition, transient expression of the IL-13Ralpha2 transgene in 293T cells increases the IL-4-mediated activation of Stat3 and subsequent expression of Stat3-targeted gene. Coimmunoprecipitation results reveal that IL-13Ralpha2-mediated activation of Stat3 does not require a direct physical interaction between Stat3 and IL-13Ralpha2. Chromatin immunoprecipitation assay employing anti-Stat3 antibody confirms the in vivo binding of activated Stat3 to the promoters of genes that encode antiapoptotic proteins Bcl-2, Bcl-x(L), and Mcl-1. IL-4 significantly up-regulates of the steady-state levels of Bcl-2, Bcl-x(L), and Mcl-1 in GBM cells. These results indicate that IL-4/IL-13 receptor-mediated Stat3 signaling may contribute to the pathogenesis of GBM cells by modulating the expression of the Bcl-2 family of antiapoptotic proteins.     

丁酸钠诱导HT 29结肠癌细胞凋亡及其对 p 53靶基因的调控

目的：〖HT5"SS〗分析丁酸钠对HT29结肠癌细胞p53三个主要靶基因（p21waf1,bax和gadd45）的调控,并探讨其作用机制。〖HT5W〗方法：〖HT5"SS〗HT29细胞常规培养在含有和不含有丁酸钠的培养液中。分别用MTT和流式细胞仪(flow cytometry,FCM) 检测细胞增殖和细胞周期分布,通过形态学观察、亚G1峰的检测和AnnexinVFITC 双标记观察细胞凋亡情况;RTPCR和Western blot分别检测丁酸钠对p21waf1,bax和gadd45三种基因mRNA和蛋白表达水平的影响。〖HT5W〗结果：〖HT5”SS〗丁酸钠以剂量和时间依赖的方式抑制HT29细胞增殖和诱导凋亡,并阻滞细胞于G1期。RTPCR 和Western blot结果显示丁酸钠可以促进p21waf1和bax基因mRNA和蛋白的表达,而对gadd45基因的表达无明显影响。〖HT5W〗结论：〖HT5”SS〗2.5 mmol/L以上浓度的丁酸钠可以抑制HT29细胞增殖并诱导凋亡,该作用可能通过上调p21waf1和bax基因表达而实现。     

Identification of one exon deletion of intestinal alkaline sphingomyelinase in colon cancer HT-29 cells and a differentiation-related expression of the wild-type enzyme in Caco-2 cells

Sphingomyelin (SM) metabolism in the gut has been implicated in colonic tumorigenesis. Intestinal alkaline sphingomyelinase (alk-SMase) hydrolyses SM in the intestinal content and at the brush border. The enzyme activity is decreased in the tissues of human colorectal tumours. This study examines whether site or chain-mutation of alk-SMase occurs in colon cancer HT-29 cells and Caco-2 cells. Total RNA was isolated and the cDNA of alk-SMase was amplified by RT-PCR. The size of the cDNA from HT-29 cells was smaller than that of the wild-type cDNA. DNA sequencing identified a deletion of exon 4 in alk-SMase cDNA in HT-29 cells. No mutation in genomic alk-SMase DNA from exon 3 to 5 was identified. The exon 4 deletion was caused by a shift of RNA splice site in chromosome 17q25. In Caco-2 cells, no mutation of alk-SMase cDNA was identified. Transient expression in COS-7 cells showed that the enzyme from the cDNA in HT-29 cells had little alk-SMase activity whereas that in Caco-2 cells was as active as the wild-type alk-SMase. The deleted region included residue His353, which is predicted to form a substrate-binding site of alk-SMase. H353A substitution resulted in a protein with no alk-SMase activity. In monolayer cultured Caco-2 cells and HT-29 cells the alk-SMase activities were low. However, to culture the cells under polarizing conditions increased alk-SMase activity and reduced SM level in Caco-2 cells. The alk-SMase activity varied in parallel with alkaline phosphatase activity. In conclusion, we identified an inactive deletion in alk-SMase in HT-29 cells, and a differentiation-related expression of the enzyme in Caco-2 cells. The results provide a molecular mechanism related to previous findings of reduced alk-SMase activity in human colon cancers.