胃癌细胞PTEN甲基化与其表达的相关性

目的:探讨胃癌细胞PTEN基因启动子区域甲基化与其mRNA表达的关系.方法:采用甲基化特异性PCR法(MSP)检测四种胃癌细胞系SGC-7901(中度分化)、BGC-823(低度分化细胞)、MGC-803(低度分化细胞)、HGC-27中PTEN基因甲基化状态,RT-PCR检测四种胃癌细胞系PTEN表达水平(未分化).结果:HGC-27、MGC-803、BGC-823细胞系可检测到PTEN基因启动子的甲基化,SGC-7901细胞未检测到甲基化,甲基化水平的顺序依次为:HGC-27最高(138.217±7.898,P<0.01),MGC-803、BGC-823次之(P>0.05).PTENmRNA表达水平的依次顺序为:SGC-7901最高(0.336±0.079,P<0.01),BGC-823、MGC-803次之(P>0.05),HGC-27表达水平最低(0.113±0.047,P<0.05),其表达水平随着其启动子区甲基化水平增高而降低.PTENmRNA表达及其启动子甲基化水平还与胃癌细胞分化程度相关.结论:胃癌细胞PTEN基因启动子区域出现异常甲基化,可能是导致其mRNA表达异常的主要原因,也可能是导致胃癌发生、发展的重要机制之一.     

正常上皮细胞特异性基因甲基化在胃癌发病机制中的研究

目的探讨正常上皮细胞特异性-1基因（NES1）在胃正常卜皮细胞和胃癌细胞株中的表达及其受甲基化调控的影响。方法分别培养胃癌细胞株MKN-28（高分化）、SGC-7901（中分化）、AGS（中分化）、MKN-45（低分化）、HGC-27（未分化）和原代正常胃上皮细胞。提取细胞RNA，荧光定量PCR检测NES1在各细胞株中的表达。以不同浓度的DNA甲基化酶抑制剂5＇-杂氮-2＇-脱氧胞嘧啶（5-azadC）处理胃癌细胞株，荧光定量PCR检测处理后NES1 mRNA表达。同时提取细胞基因组DNA，甲基化修饰后甲基特异性PCR（MSP）分析其CpG岛甲基化状态。结果NES1 mRNA在肿瘤细胞株中的表达较胃正常上皮细胞明显降低。甲基化检测显示，NES1在胃癌细胞株中均存在不同程度的外显子3CpG岛甲基化。NES1表达降低的胃癌细胞株经5-aza-dC去甲基化药物处理后NES1表达均有所上调。结论NES1在一些胃癌细胞株中的低表达与该基因外显子3CpG岛甲基化有关。5-aza-dC可使NESI表达降低的胃癌细胞株重新表达NES1 mRNA，再次证明了NES1基因在胃癌细胞株中的低表达与甲基化有关。NES1基因外显子3甲基化可能是胃癌细胞中NES1表达缺失的分子机制。     

强力霉素对胃癌细胞SGC-7901基质金属蛋白酶-2和基质金属蛋白酶组织抑制因子-2表达的影响

背景：强力霉素对结肠癌细胞的分化和抑制作用已有报道，但其对胃癌细胞的作用尚未见报道。目的：观察强力霉素对人胃癌细胞SGC-7901的生长抑制作用及其对基质金属蛋白酶（MMP）-2和基质金属蛋白酶组织抑制因子（TIMP）-2表达的影响，探索胃癌治疗的新方法。方法：采用不同浓度的强力霉素作用于胃癌细胞SGC-7901，以噻唑蓝（MIT）法测定其细胞毒作用；逆转录聚合酶链反应（RT—PCR）法半定量测定MMP．2和TIMP-2mRNA的表达；免疫组化法观察MMP-2蛋白的表达。结果：强力霉素可抑制胃癌细胞SGC-7901的生长，具有浓度和时间依赖性（P〈0．01）。强力霉素可下调MMP-2mRNA和MMP-2蛋白的表达，上调TIMP-2mRNA的表达，具有浓度依赖性（P〈0．05）。结论：强力霉素能抑制胃癌细胞SGC-7901的生长，其作用机制可能与下调MMP-2表达、上调TIMP-2表达有关。     

抑癌基因PTEN与胃癌细胞分化及侵袭力的机制研究

采用Boyden小室法测定三种不同分化胃癌细胞(SGC-7901、BGC-823、MGC-803、HGC-27)的体外侵袭力、运动力,RT-PCR检测胃癌细胞的PTEN mRNA表达水平,Western blot法检测胃癌细胞FAK、P-FAK蛋白表达水平.发现随着细胞分化程度的升高,PTEN mRNA表达明显增多,P-FAK蛋白表达明显减少,细胞侵袭力和运动力亦明显减弱(P＜0.01或P＜0.05),FAK蛋白表达无明显变化.认为PTEN mRNA、P-FAK蛋白表达水平在评价胃癌细胞体外运动侵袭力方面具有重要价值;PTEN基因可能通过FAK蛋白途径影响胃癌的侵袭转移.     

5-Aza-CdR体外诱导胃癌细胞系p16基因去甲基化及表达增强

目的: 观察去甲基化制剂--5-Aza-CdR对体外培养的胃癌细胞SGC7901 p16基因启动子区甲基化状态及表达的影响, 探讨胃癌细胞p16基因失活的机制及去甲基化制剂对p16基因表达的调控.方法:应用不同浓度的5-Aza-CdR(1×10-7, 5×10-7, 1×10-6, 5×10-6 mol/L)处理体外培养的胃癌细胞SGC7901后, MSP法检测用药前后细胞中p16基因的甲基化状态, RT-PCR及 Western-blot法检测用药前后细胞中p16基因mRNA及蛋白表达的变化.结果: p16基因在胃癌细胞系SGC7901中启动子区呈异常甲基化状态, 在mRNA及蛋白水平低表达. 经过1×10-7, 5×10-7, 1×10-6, 5×10-6 mol/L 5-Aza-CdR处理后, p16基因启动子区呈去甲基化状态, 各组mRNA及蛋白表达相应的比值分别与处理前的比例为2.21±0.36, 2.01±0.31;2.82±0.39, 2.22±0.33;2.98±0.42, 3.15±0.43及3.35±0.55, 3.75±0.61.结论:5-Aza-CdR能逆转胃癌细胞p16基因甲基化状态, 调控p16基因表达.     

胃癌细胞和胃癌多药耐药细胞中P-gp及GST的表达

目的比较胃腺癌SGC-7901细胞和多药耐药细胞SGC-7901/ADR中P-gp和GST表达的差异,进一步探讨胃癌多药耐药机制。方法常规培养人胃癌SGC-7901细胞和多药耐药细胞SGC-7901/ADR。制备细胞爬片,免疫细胞化学方法和灰度测定检测SGC-7901细胞和SGC-7901/ADR中P-gp及GST的表达。结果免疫细胞化学SP法染色后,P-gp蛋白阳性者在胃癌细胞的胞浆和胞膜中可见棕黄色颗粒沉着,GST在胃癌细胞的胞浆中可见棕黄色颗粒。P-gp、GST在胃癌SGC-7901细胞中呈中度表达,在胃癌SGC-7901/ADR细胞中呈高表达,两者比较有显著性差异（P〈0.05）。免疫细胞化学灰度定量测定显示同样的结果。结论 P-gp、GST在胃癌SGC-7901/ADR细胞中的表达较SGC-7901细胞明显增加,可能是胃癌多药耐药的原因之一。     

胃癌组织中E-cadherin、S100A2基因启动子区甲基化的临床意义

目的探讨胃癌组织中E-cadherin、S100A2基因启动子区甲基化的临床意义。方法采用甲基化特异性PCR方法,检测64例胃癌患者（胃癌组）病变组织及15例胃溃疡患者（对照组）正常胃组织中的E-cadherin、S100A2基因启动子区甲基化,分析二者与胃癌生物学特征的关系。结果胃癌组E-cadherin基因启动子区甲基化38例（59.38%）,S100A2基因启动子区甲基化36例（56.25%）;对照组分别为2、2例（13.3%、13.3%）。在胃癌不同大体分型、分化程度及淋巴结转移患者中,E-cadherin、S100A2基因启动子区甲基化率均有统计学差异（P〈0.05或〈0.01）。结论胃癌组织中的E-cadherin、S100A2基因启动子区呈高甲基化状态,甲基化状态与胃癌的分化、转移、侵袭有关。     

PTEN基因表达与胃癌细胞侵袭力的相关性研究

目的探讨PTEN基因mRNA表达与胃癌细胞体外侵袭力的关系。方法采用Boyden小室法测定四种胃癌细胞(SGC-7901、BGC-823、M GC-803、HGC-27)的体外侵袭力、运动力,RT-PCR法检测四种胃癌细胞的PTEN基因mRNA表达水平。结果胃癌细胞体外侵袭力为HGC-27(48±2)、M GC-803(28±2)、BGC-823(30±3)、SGC-7901(13±2);PTEN基因mRNA表达水平为SGC-7901(0.336±0.079)、BGC-823(0.232±0.063)、M GC-803(0.228±0.056)、HGC-27(0.113±0.047);两两比较,P<0.01,>0.05,<0.05。相关分析显示,胃癌细胞体外侵袭力随PTEN基因mRNA表达增高而降低,PTEN基因mRNA表达及胃癌细胞体外侵袭力与细胞分化程度相关。结论PTEN基因参与胃癌的发展过程,并与胃癌的部分生物学行为有关,PTEN基因mRNA表达水平对评价胃癌细胞体外运动侵袭力具有重要价值。     

选择性环氧合酶-2抑制剂NS-398抑制胃癌细胞P-糖蛋白表达

目的 探讨选择性环氧合酶-2（COX-2）抑制剂NS-398对胃癌细胞株SGC-7901 P-糖蛋白（P-gp）表达的影响。方法 胃癌细胞株SGC-7901经浓度分别为0、10、100μmol／L的NS-398处理后，酶联免疫吸附试验检测NS-398对胃癌细胞前列腺素E2（PGF2）分泌的影响，24、48h后用RT-PCR检测多药耐药（mdr）1 mRNA表达，48h后用免疫细胞化学染色法检测P-gp表达。结果 NS-398可显著抑制胃癌细胞株SGC-7901 PGE2分泌，并呈浓度依赖性（P〈0．05）。不同浓度NS-398作用于细胞后，胃癌细胞株SGC-7901的mdr1／P-gp表达受不同程度抑制，100μmol／L的NS-398对mdr1 mRNA表达抑制作用强于10μmol／L（P〈0．01）。不同浓度药物与测量时间为交互作用．作用48h与24h相比，NS-398对mdr1 mRNA表达的抑制作用更强（P〈0．01）。结论 NS-398可抑制SGC-7901的mdr1／Pgp表达，且呈剂量效应关系。NS-398可能通过抑制COX-2活性，抑制COX-2下游产物PGE2表达，从而抑制P-gp表达。选择性COX-2抑制削可能有助于减轻肿瘤细胞对化疗药物的耐药性。     

胃癌细胞多药耐药相关基因的表达与其侵袭转移能力的相关性研究

目的探讨胃癌细胞株BGC-823、SGC-7901的多药耐药相关基因的表达与其侵袭转移能力的关系。方法采用实时荧光定量PCR技术检测胃癌细胞株BGC-823、SGC-7901的多药耐药相关基因(包括ABCB1、MMP2、CDH1、CD44)的mRNA表达水平。采用细胞划痕实验、Transwell迁徙实验评价两株胃癌细胞的侵袭转移能力,进而探讨胃癌细胞多药耐药相关基因的表达与侵袭转移能力的关系。结果荧光定量PCR实验发现胃癌细胞株BGC-823的ABCB1、CDH1、CD44基因表达较SGC-7901高,而MMP2基因的表达在SGC-7901中较高。细胞划痕实验及Transwell迁徙实验显示胃癌细胞株BGC-823的迁徙能力比SGC-7901强。结论胃癌细胞的多药耐药与侵袭转移有一定的关系,CD44的高表达在胃癌细胞的侵袭转移中可能起主要作用。     

Suppression of gastric cancer growth by adenovirus-mediated transfer of the PTEN gene

AIM: To investigate the tumor-suppressive effect of the phosphatase and tensin homologue deleted from chromosome (PTEN) in human gastric cancer cells that were wild type for PTEN. METHODS: Adenoviruses expressing PTEN or luciferase as a control were introduced into gastric cancer cells. The effect of exogenous PTEN gene on the growth and apoptosis of gastric cancer cells that are wtPTEN were examined in vitro and in vivo. RESULTS: Adenovirus-mediated transfer of PTEN (AdPTEN) suppressed cell growth and induced apoptosis significantly in gastric cancer cells (MGC-803, SGC-7901) carrying wtPTEN in comparison with that in normal gastric epithelial cells (GES-1) carrying wtPTEN. This suppression was induced through downregulation of the Akt/PKB pathway, dephosphorylation of focal adhesion kinase and mitogen-activated protein kinase and cell-cycle arrest at the G2/M phase but not at the G1 phase. Furthermore, treatment of human gastric tumor xenografts (MGC-803, SGC-7901) with Ad-PTEN resulted in a significant (P<0.01) suppression of tumor growth. CONCLUSION: These results indicate a significant tumor-suppressive effect of Ad-PTEN against human gastric cancer cells. Thus, Ad-PTEN may be used as a potential therapeutic strategy for treatment of gastric cancers.     

5-Aza-dC及TSA对人胃癌细胞株SGC-7901 Runx3基因甲基化及表达水平的影响

目的:探讨5-Aza-dC及TSA对人胃癌细胞系SGC-7901中抑癌基因Runx3启动子区甲基化、mRNA及蛋白表达水平的影响.方法:单独或联合应用5-Aza-dC及TSA处理体外培养的SGC-7901细胞,提取各组细胞的DNA、RNA及蛋白质,应用甲基化特异性定量PCR法(QMSP)检测Runx3基因启动子区甲基化状态,逆转录PCR法(RT-PCR)检测Runx3mRNA的表达,免疫印迹法(Western blotting)法检测Runx3蛋白表达水平.结果:5-Aza-dC和TSA均能降低Runx3基因启动子区的甲基化水平(5-Aza-dC组及TSA组分别为对照组的0.70倍、0.63倍),提高mRNA表达水平(0.29±0.01、0.28±0.03vs0.14±0.03,P<0.05)及蛋白表达水平(0.35±0.02、0.37±0.02vs0.09±0.01,P<0.05);与单独使用5-Aza-dC和TSA相比,两药联合组Runx3基因启动子区甲基化水平(对照组的0.37倍)及mRNA表达水平(0.45±0.02)和蛋白表达水平(0.50±0.01)均较单药组效果更明显(P<0.05).结论:5-...     

Adenovirus-mediated FasL gene transfer into human gastric carcinoma

AIM: To evaluate the possible value of FasL in gastric cancer gene therapy by investigating the effects of FasL expression on human gastric cancer cell line. METHODS: An adenoviral vector encoding the full-length human FasL cDNA was constructed and used to infect a human gastric cancer (SGC-7901) cell line. FasL expression was confirmed by X-gal staining, flow cytometric analysis and RT-PCR. The effect of FasL on cell proliferation was determined by clonogenic assay, cytotoxicity was detected by MTT assay, and cell viability was measured by trypan blue exclusion. The therapeutic efficiency of Ad-FasL in vivo was investigated with a xenograft tumor model in nude mice. RESULTS: SGC-7901 cells infected with Ad-FasL showed increased expression of FasL, resulting in significantly decreased cell growth and colony-forming activity when compared with control adenovirus-infected cells. The cytotoxicity of anti-Fas antibody (CH-11) in gastric cancer cells was stronger than that of ActD (91±8 vs60±5,P<0.01), and the cytotoxicity of Ad-FasL was stronger than that of CH-11 (60±5 vs50±2, P<0.05). In addition, G1-phase arrest (67.75±0.39 vs 58.03±2.16, P<0.05) and apoptosis were observed in Ad-FasL-infected SGC-7901 cells, and the growth of SGC-7901 xenografts in nude mice was retarded after intra-tumoral injection with Ad-FasL (54% vs 0%,P<0.0001). CONCLUSION: Infection of human gastric carcinoma cells with Ad-FasL induces apoptosis, indicating that this target gene might be of potential value in gene therapy for gastric cancer.     

胃泌素对胃癌细胞EMT和Wnt/β-catenin信号通路相关基因表达的影响

目的探讨高表达胃泌素(gastrin)对胃癌细胞上皮间质转化(EMT)的影响及可能机制。方法用gastrin过表达质粒pcDNA3-gastrin及空载体pcDNA3.1转染胃癌细胞SGC-7901、MKN45,48 h后收集细胞蛋白,Western印迹检测鉴定gastrin表达,检测EMT相关标志物E-钙黏蛋白(cadherin)、N-cadherin、Snail及wnt/β-连环蛋白(catenin)信号通路相关基因wnt3α、β-catenin、c-myc的蛋白表达变化。结果在SGC-7901、MKN45细胞中成功过表达gastrin。与pcDNA3.1空载体转染组相比,pcDNA3.1-gastrin转染SGC-7901、MKN45细胞中上皮标志蛋白E-cadherin表达下调,间质标志蛋白N-cadherin、Snail表达上调,差异有统计学意义(P<0.05);同时Wnt/β-catenin通路蛋白相关蛋白wnt3α、β-catenin及其下游基因c-myc的表达上调,差异有统计学意义(P<0.05)。结论过表达gastrin能够激活Wnt/β-catenin信号通路和促进胃癌细胞SGC-7901和MKN45发生EMT。     

HTRA1 gene expression in gastric epithelial cells

Objective:To explore HtrA1 gene expression aud its regulation in human gastric cancers.Methods:The HtrA1 mRNA levels were examined by QPCR analysis and coufirmed its expression with Northern blot analysis.The HtrA1 protein levels in all six gastric epithelial cell lines were investigated by Western blot analysis.Gene copy number was accessed and then sequenced the coding region from each mRNA in all six cell lines.The HtrA1 promoter region DNA methylation status was detected by using bisulfite sequeucing analysis.Effect of decitabine and TSA on HTRA1 expression in gastric cancer cell line was determined by RTPCR.Results:HIC analysis indicated that HtrA1 was highly expressed in normal epithelium,but dramatically down-regulated in gastric carcinoma tissues and variably expressed in tumor-adjacent tissues.HtrA1 gene expression was dramatically decreased in gastric carcinoma cells compared to nontumorigenic counterparts.The HtrA1 gene loss in any of the 4 breast cancer cell lines was not detected.Total 14 CpGs in this region were all methylated in gastric cancer cells,whereas two normal cells.GES-1 and HFI-145,were having several unmethylated cytosines in this region.HtrA1 showed as~Mr 44,000,Expression of HtrA1 protein was not observed in any of the four gastric caucer cell lines.BGC-823.MKN-45.SGC-7901and MKN-28.HtrA1 expression was observed in the HF1-145and GES-1 cell lines.Conclusions:The epigenetic silencing for HtrA1gene expression could provide a possible strategy for re-activating Htrt1 gene expression in gastric cancer cells.thus facilitating further investigation of HtrA1's role in chemotherapy.     

Xiaotan Sanjie decoction inhibits interleukin-8-induced metastatic potency in gastric cancer

AIM:To investigate the interaction between Xiaotan Sanjie(XTSJ) decoction and interleukin-8(IL-8) and its effect on adhesion,migration and invasion of SGC-7901 gastric cancer cells.METHODS:SGC-7901 gastric cancer cells were exposed to serum containing XTSJ decoction and/orIL-8(1 ng/m L).SGC-7901 cell adhesion to fibronectin,an extracellular matrix component,was detected using the Cell Counting Kit-8.Migration and invasion abilities of SGC-7901 cells were detected by scratch wound and Transwell chamber assays.Then,protein(immunofluorescence and Western blot) and m RNA levels(quantitative polymerase chain reaction) of cluster of differentiation 44(CD44),a cell adhesion molecule,were measured in 72-h-cultured SGC-7901 cells.RESULTS:Cell adhesion was promoted by IL-8(P = 0.001),but was inhibited by XTSJ decoction(P = 0.0001).Similarly,IL-8 promoted SGC-7901 cell invasion(P = 0.003),and XTSJ decoction inhibited cell invasion(P = 0.001).IL-8 induced SGC-7901 cell migration,but this was inhibited by XTSJ decoction.IL-8 up-regulated CD44 protein(P = 0.028) and m RNA expression(P = 0.002),whereas XTSJ decoction inhibited CD44 protein expression(P = 0.0001),but not m RNA expression(P = 0.275).An interaction between XTSJ decoction and IL-8 was confirmed in the invasion(P = 0.001) and CD44 m RNA expression of SGC-7901 cells(P = 0.010),but not in cell adhesion(P = 0.051).CONCLUSION:XTSJ decoction may inhibit adhesion,migration and invasion of gastric cancer cells,which is partly associated with down-regulation of IL-8.