他莫昔芬对转染ERβ1基因的MCF-7细胞生长特性的影响

目的研究在不同处理因子作用下,外源基因ERβ1的表达对MCF-7乳腺癌细胞系生长特性的影响。方法利用脂质体转染方法将ERβ1真核表达载体pcDNA3.1-EGFPERβ1导入MCF-7乳腺癌细胞系。采用Western blot方法检测转染细胞中ERβ1的蛋白表达水平,筛选阳性克隆。以亲本细胞MCF-7为对照,分别在雌激素和雌激素受体拮抗剂他莫昔芬作用下观察细胞的生长特点。结果在转染ERβ1基因的MCF-7细胞系中,Western blot检测证实ERβ1的蛋白表达水平显著增高。在无处理因子的情况下,外源基因ERβ1在MCF-7细胞系中的表达能抑制细胞生长。与亲本细胞MCF-7细胞相比,转染ERβ1的MCF-7细胞对雌激素的敏感性下降,但对他莫昔芬的敏感性无明显变化。结论外源性ERβ1基因在MCF-7乳腺癌细胞中的稳定表达不增加对他莫昔芬的耐药性,但使之对雌激素的敏感性下降。     

ERβ1对乳腺癌MCF-7细胞Efp基因表达的抑制作用

目的 了解雌激素受体β1（ERβ1）对雌激素敏感性指状蛋白（Efp）基因的调节作用,为进一步探讨ERβ对Efp基因的调控机制奠定基础.方法 应用脂质体法将ERβ1真核表达质粒转染至乳腺癌MCF-7细胞中,再用Western blot检测转染细胞中Efp蛋白表达的变化.MTT比色试验观察ERβ1真核表达质粒转染后MCF-7细胞增殖活性的变化.结果 外源性ERβ1真核表达质粒组MCF-7细胞较未转染组MCF-7细胞Efp蛋白表达明显减弱.ERβ1基因转染后的MCF-7细胞的增殖活性降低.结论 ERβ1基因的表达可以抑制人乳腺癌MCF-7细胞中Efp基因的表达,并抑制MCF-7细胞的增殖能力,可能在乳腺肿瘤发生、发展机制中具有重要的作用.     

蛋白质精氨酸甲基转移酶2在乳腺癌细胞中的表达及其对SKBR-3细胞生长特性的影响

目的:探讨蛋白质精氨酸甲基转移酶2(protein arginine methyltransferase 2,PRMT2)基因在多种乳腺癌细胞株中的表达情况,以及外源性PRMT2基因过表达对乳腺癌SKBR-3细胞生长特性的影响.方法:采用real-time RT-PCR法检测PRMT2基因在不同乳腺癌细胞株中的表达,并建立稳定表达pcDNA3.1/NT-GFP-PRMT2的SKBR-3细胞株;激光共聚焦显微镜下观察外源性PRMT2蛋白在细胞中的定位,检测在雌激素和雌激素受体(estrogen receptor,ER)拮抗剂4-OHT作用下过表达PRMT2基因对SKBR-3细胞增殖的影响.结果:PRMT2基因在ERα阳性乳腺癌细胞株中表达水平明显高于ERα阴性乳腺癌细胞株;在转染PRMT2基因的SKBR-3细胞株中,雌激素反应元件-荧光素酶报告基因(estrogen response elements-luciferase reporter,ERE-luc)的转录活性明显升高.在无处理因子情况下,外源基因PRMT2在SKBR-3细胞中的表达对细胞的形态及生长速度无明显影响.与未转染及转染GFP空载体的SKBR-3细胞相比,稳定转染PRMT2基因的SKBR-3细胞对雌激素的敏感性明显下降,但其对4-OHT处理的敏感性降低无明显差异.结论:PRMT2基因表达的多少及部位与乳腺癌细胞中ERα的表达密切相关.外源性PRMT2基因在乳腺癌SKBR-3细胞中稳定表达使细胞对雌激素的敏感性降低,但不增加细胞对ER拮抗剂4-OHT的耐药性.     

ERβ表达载体的构建及其在肿瘤细胞中的功能研究

目的 构建ERβ表达载体,探讨其在肿瘤细胞株中的表达及功能。方法 利用常规PCR技术扩增人全长ERβ编码序列,并将其克隆到真核表达载体pCDNA3中,得到重组质粒pCDNA3-ERβ。用Western blot和体外翻译方法检测ERβ的表达情况。将pCDNA3-ERβ分别转染SV4O病毒转化的胚胎肾细胞293T、乳腺癌细胞MDA-MB-435、MDA-MB-436、SKBR3和前列腺癌细胞PC-3,用含雌激素应答元件的报告基因系统检测ERβ在这些不同细胞中的功能。结果 经酶切鉴定,证实重组质粒pCDNA3-ERβ含有目的基因ERβ。Western blot检测表明,转染pCDNA3-ERβ的细胞表达了相对分子量为63000的ERβ蛋白。体外翻译进一步证实该表达载体翻译了ERβ蛋白。报告基因系统检测表明,ERβ在不同肿瘤细胞中的表达均激活了雌激素应答的ERE和C3报告基因的表达。结论pCDNA3-ERβ在肿瘤细胞中既可表达,又具有功能活性,为进一步研究ERβ在肿瘤细胞中的作用奠定了基础。     

Id2 通过非 HLH 结构域促进 MCF-7 细胞的侵袭性

目的：观察Id2基因转染乳腺癌细胞MCF-7后对细胞生长、侵袭能力的变化，探讨Id2基因缺失HLH结构域后对细胞的影响。方法：以携带Id2-DBM和Id2-DBM-8HLH基因的质粒（pCDNA3．1-Id2-DBM和pCDNA3．1-Id2-DBM-8HLH）经脂质体介导转染MCF-7细胞。RT—PCR法检测转染后Id2、Id2-DBM和Id2-DBM-6HLHmRNA表达水平；MTT法检测MCF-7细胞增殖曲线；划痕实验、transwell小室检测细胞的迁移能力；Western Blot分析Id2对MCF-7细胞E—cad表达的影响。结果：mRNA水平显示质粒均成功转入；细胞生长曲线显示增殖无显著差异；与空载组比较，转染pCDNA3．1-Id2-DBM和pCD．NA3．1-Id2-DBM-8HLH后侵袭能力增强，且E—cad表达降低。结论：Id2蛋白的过表达可以促进乳腺癌细胞MCF-7的侵袭能力，与E—cad的降低有关，且该作用在缺失HLH结构域后仍然存在。     

Id2通过非HLH结构域促进MCF-7细胞的侵袭性

目的：观察Id2基因转染乳腺癌细胞MCF-7后对细胞生长、侵袭能力的变化，探讨Id2基因缺失HLH结构域后对细胞的影响。方法：以携带Id2-DBM和Id2-DBM-8HLH基因的质粒（pCDNA3．1-Id2-DBM和pCDNA3．1-Id2-DBM-8HLH）经脂质体介导转染MCF-7细胞。RT—PCR法检测转染后Id2、Id2-DBM和Id2-DBM-6HLHmRNA表达水平；MTT法检测MCF-7细胞增殖曲线；划痕实验、transwell小室检测细胞的迁移能力；Western Blot分析Id2对MCF-7细胞E—cad表达的影响。结果：mRNA水平显示质粒均成功转入；细胞生长曲线显示增殖无显著差异；与空载组比较，转染pCDNA3．1-Id2-DBM和pCD．NA3．1-Id2-DBM-8HLH后侵袭能力增强，且E—cad表达降低。结论：Id2蛋白的过表达可以促进乳腺癌细胞MCF-7的侵袭能力，与E—cad的降低有关，且该作用在缺失HLH结构域后仍然存在。     

乳腺癌上皮-间质转化后引发BCRP介导的多药耐药的研究

背景与目的:研究发现肿瘤的侵袭浸润和转移增强是上皮-间质转化(epithelial mesenchymal transition, EMT)所致,而EMT的发生也与肿瘤细胞多药耐药现象的发生密切相关.本研究通过分析乳腺癌组织和细胞中EMT与乳腺癌耐药蛋白表达的相关性,探讨EMT对乳腺癌中乳腺癌耐药蛋白(breast cancer resistant protein, BCRP)介导多药耐药的影响.方法:免疫组织化学方法检测乳腺癌组织中Snail、BCRP的表达:构建Snail真核表达载体pCDNA3.1-Snail,转染至MCF-7细胞,采用免疫荧光、Western blot、Real-time PCR检测转录抑制因子snail、上皮标志物E-钙粘素、间质标志物vimentin以及多药耐药蛋白BCRP的表达;MTT法检测细胞对米托蒽醌的耐药指数.结果:免疫组化结果显示乳腺癌组织中Snail、BCRP的表达呈显著相关:免疫荧光、Western blot、Real-time PCR显示与亲本MCF-7细胞相比,转染Snail后的MCF-7细胞中E-cadherin表达水平明显降低,而snail、vimentin和BCRP的表达水平明显增加;MTT结果显示细胞对米托蒽醌的耐药指数增加至9.93.结论:转染snail真核表达载体pCDNA3.1-snail可使乳腺癌MCF-7细胞发生EMT, 并导致细胞中BCRP表达增加,引发BCRP介导的多药耐药.     

TrkA-siRNA增强人乳腺癌MCF-7细胞对紫杉醇的敏感性

目的 探讨靶向抑制TrkA基因表达后,人乳腺癌细胞MCF-7对化疗药物紫杉醇敏感性的变化.方法 8 μmol/L紫杉醇作用于乳腺癌MCF-7亲本细胞株和TrkA-siRNA转染细胞株24、48小时后,MTT法检测细胞增殖抑制效应,Western blot检测凋亡蛋白caspase-3的活化.倒置显微镜观察细胞株生长的形态学变化.结果 紫杉醇作用24、48小时后,其对TrkA-siRNA细胞株的生长抑制均高于MCF-7亲本细胞株(P＜0.05),且48小时抑制率高于24小时(P＜0.05).Western blot结果显示,caspase-3蛋白在紫杉醇作用24小时后被激活,其在TrkA-siRNA细胞株中的表达高于MCF-7亲本细胞株(P＜0.05).结论 TrkA-siRNA能增加乳腺癌细胞对化疗药物紫杉醇的敏感性.     

NO-Aspirin抑制MCF-7乳腺癌细胞的生长以及对Wnt/β-catenin/TCF-4信号通路的影响

目的:探讨NO-ASA(一氧化氮阿斯匹林)对MCF-7人乳腺癌细胞生长的影响及其机制.方法:建立稳定传代的MCF-7细胞系.MT法测定NO-ASA对MCF-7人乳腺癌细胞的增殖抑制作用.应用Western blot法检测对Wnt/β-catenin/TCF-4信号通路的影响.结果:NO-ASA能强烈抑制细胞生长和β-catenin/TCF转录活性;NO-ASA降低了Wnt/β-catenin下游区靶基因细胞周期蛋白D1(cyclin D1)和细胞总β-catenin的表达水平.结论:NO-ASA通过减少β-catenin表达及抑制β-catenin/TCF依赖转录活性,强烈抑制MCF-7人乳腺癌细胞增殖,导致其靶基因一细胞周期蛋白D1表达降低.这为乳腺癌的预防和治疗提供了针对性的合理的方法.     

乳腺癌耐药细胞ER表达状态影响细胞对屈洛昔芬和阿霉素的敏感性

背景与目的：雌激素受体（estrogen receptor,ER)阳性乳腺癌细胞株来源的耐药细胞株中,ER表达缺失或下降,且细胞生长速度减慢,本文的目的是研究MCF－7／Adr乳腺癌耐药细胞株中ER表达状态与细胞对出洛昔芬（droloxifene,Dro)和阿霉素（Adriamycin,Adr)敏感性之间的关系。方法：Western blot法检测MCF－7／Adr及其亲本MCF－7细胞中ER蛋白的表达,构建ER的真核细胞表达质粒（pCER),利用LipofectAMINE^TM将ER基因导入MCF－7／Adr细胞,经G418抗性筛选获得阳性克隆（MTER／Adr),PCR,Western blot法鉴定并检测ER基因的整合和蛋白表达,流式细胞仪检测细胞周期变化,MTT法检测Dro及Adr对细胞增殖的影响。结果：在MCF－7细胞中可检测到ER蛋白 的表达,而MCF－7／Adr细胞中使用Westernblot检测不到ER蛋白的表达,成功构建真核细胞表达质粒pCER并转染MCF－7／Adr细胞,阳性克隆MTER／Adr整合了ER基因并获得表达。经MTT分析,10μmol/LDro对MCF－7细胞的生长有明显的抑制作用。而到20μmol/L时对MCF－7／Adr细胞的生长有抑制作用。ER转染MCF－7／Adr细胞后,15μmol/L的Dro对其生长出现抑制作用,使细胞多分布于G0／G1期。同时细胞对Adro的敏感性下降,结论：MCF－7／MCF－7／Adr细胞部分恢复对Dro和Adr的敏感性。     

A molecular model for the mechanism of acquired tamoxifen resistance in breast cancer

PurposeOestrogen (E₂)-stimulated growth re-emerges after a c-Src inhibitor blocking E₂-induced apoptosis. A resulting cell line, MCF-7:PF, is selected with features of functional oestrogen receptor (ER) and over-expression of insulin-like growth factor-1 receptor beta (IGF-1Rβ). We addressed the question of whether the selective ER modulator (SERM), 4-hydroxytamoxifen (4-OHT) or other SERMs could target ER to prevent E₂-stimulated growth in MCF-7:PF cells.MethodsProtein levels of receptors and signalling pathways were examined by immunoblotting. Expression of mRNA was measured through real-time RT-PCR. Recruitment of ER or nuclear receptor coactivator 3 (SRC3) to the promoter of ER-target gene was detected by chromatin-immunoprecipitation (ChIP).Results4-OHT and other SERMs stimulated cell growth in an ER-dependent manner. However, unlike E₂, 4-OHT suppressed classical ER-target genes as does the pure antioestrogen ICI 182,780 (ICI). ChIP assay indicated that 4-OHT did not recruit ER or SRC3 to the promoter of ER-target gene, pS2. Paradoxically, 4-OHT reduced total IGF-1Rβ but increased phosphorylation of IGF-1Rβ. Mechanistic studies revealed that 4-OHT functioned as an agonist to enhance the non-genomic activity of ER and activate focal adhesion molecules to further increase phosphorylation of IGF-1Rβ. Disruption of membrane-associated signalling, IGF-1R and focal adhesion kinase (FAK), completely abolished 4-OHT-stimulated cell growth.ConclusionsThis study is the first to recapitulate a cellular model in vitro of acquired tamoxifen resistance developed in athymic mice in vivo. Importantly, it provides a rationale that membrane-associated pathways may be valuable therapeutic targets for tamoxifen resistant patients in clinic.     

Farnesol, a mevalonate pathway intermediate, stimulates MCF-7 breast cancer cell growth through farnesoid-X-receptor-mediated estrogen receptor activation

Farnesoid X receptor (FXR) is a metabolic nuclear receptor expressed in the liver and traditionally considered as a bile acid sensor. Yet, FXR has been recently demonstrated in other tissues and cells, such as the kidneys, the adrenals, and arterial smooth muscle cells. Immunohistochemical data reported in this study point to the expression of FXR in human breast cancer. In addition, FXR expression was also found by Western blotting and immunofluorescence microscopy in breast-cancer-derived cell lines MCF-7 (estrogen receptor [ER]-positive) and MDA-MB-231 (ER-negative). The FXR activator farnesol, a mevalonate pathway intermediate, exerts a mitogenic effect on MCF-7 cells. The growth stimulation is completely suppressed by antiestrogens. In contrast, MDA-MB-231 cells appear farnesol-insensitive, suggesting an involvement of ER in farnesol mitogenicity. In accordance with this interpretation, farnesol induces in MCF-7 cells a decrease of ER level, consistent with a phenomenon of receptor downregulation. Farnesol also increases progesterone receptor (PgR) expression in MCF-7 cells and stimulates ER-mediated gene transactivation in MVLN cells (MCF-7 cells stably transfected with an ER reporter gene). Of note, both effects of farnesol on ER expression and activity are completely suppressed by antiestrogens. In addition, farnesol-induced PgR is markedly reduced by FXR gene silencing (siRNA), demonstrating the involvement of FXR in the estrogenic effects of farnesol. Finally, coimmunoprecipitation experiments (FXR immunoprecipitation followed by Western blot analysis of ER in the immunoprecipitate) produced definite evidence that FXR interacts with ER. Altogether, these observations reveal the hitherto unreported presence of FXR in breast cancer and show that the latter receptor functionally interacts with ER. The occurrence of such a crosstalk calls for some caution regarding the pharmacological use of FXR agonists. Fabrice Journe and Guy Laurent contributed equally to this work and should be considered as joint first authors.     

Inhibition of estrogen-dependent breast cell responses with phenylacetate

The aromatic fatty acid phenylacetate (PA) and its analogs have come under intense investigation due to their ability to cause the growth arrest of a variety of neoplasia, including human breast cancer. We have determined that PA and its halide derivative 4-chlorophenylacetate (4-CPA) showed marked antiproliferative activity on 3 of 6 human breast cancer cell lines tested. Interestingly, the 3 cell lines that were growth inhibited by PA and 4-CPA were estrogen receptor (ER) positive (T47-D, MCF-7 and ZR-75-1) whereas those that were little affected by these compounds were ER-negative (MDA-MB-157, MDA-MB-231 and SK-Br-3). Dose response studies indicated that 4-CPA inhibited the growth of the sensitive (ER+) cell lines with a potency 3-4 times that of PA. These findings suggest that there is "cross-talk" between the PA and estrogen signaling pathways such that PA can directly inhibit estrogen-dependent events. This hypothesis was directly tested in vitro using ER+ MCF-7 cells that were stably transfected with a luciferase reporter construct driven by the full length (1745 bp) cyclin D1 promoter (MCF-7-D1). Our experiments with MCF-7-D1 cells indicated that PA and 4-CPA inhibited basal and estrogen-induced reporter gene activity by up to 90%, resulting in almost complete elimination of estrogen-dependent cyclin D1 gene activation. Using a reporter gene construct (ERE(V)-tk-Luc) containing a canonical estrogen response element that was transiently transfected into MCF-7 and MDA-MB-231 cells, we have also demonstrated inhibition of promoter activity by PA and 4-CPA that was directly mediated by blockage of activity through the ERE. Taken together, these findings indicate that PA analogs possess potent antiestrogen properties that may, at least partly, account for their antiproliferative effects on ER+ breast cancer cells. The data suggests a novel mechanism of action that might bypass some of the limitations of conventional antiestrogen therapy.     

Stable transfection of protein kinase C alpha cDNA in hormone-dependent breast cancer cell lines

An inverse relationship between protein kinase C (PKC) activity and oestrogen receptor (ER) expression in human breast cell lines and tumours has been firmly established over the past 10 years. To determine whether specific alterations in PKC expression accompany hormone-independence, we examined the expression of PKC isozymes in the hormone-independent human breast cancer cell clones MCF-7 5C and T47D:C42 compared with their hormone-dependent counterparts, MCF-7 A4, MCF-7 WS8 and T47D:A18 respectively. Both hormone-independent cell clones exhibit elevated PKC alpha expression and increased basal AP-1 activity compared with the hormone-dependent cell clones. To determine whether PKC alpha overexpression is sufficient to mediate the hormone-independent phenotype, we stably transfected an expression plasmid containing PKC alpha cDNA to the T47D:A18 and MCF-7 A4 cell lines. This is the first report of PKC alpha transfection in T47D cells. In contrast to MCF-7 cells, T47D has the propensity to lose the ER and more readily forms tamoxifen-stimulated tumours in athymic mice. We find that in T47D:A18/PKC alpha clones, there is concomitant up-regulation of PKC beta I and delta, whereas in the MCF-7 A4/PKC alpha transfectants PKC epsilon is up-regulated. In T47D:A18, but not in MCF-7 A4, PKC alpha stable transfection is accompanied by down-regulation of ER function whilst basal AP-1 activity is elevated. Our results suggest PKC alpha overexpression may play a role in growth signalling during the shift from hormone dependent to hormone-independent breast cancers.