雌激素受体阳性乳腺癌组织中Efp和Plk3的表达及其临床意义

目的:探讨雌激素受体(estrogen receptor,ER)阳性的乳腺癌患者癌组织中Efp和Plk3的表达及其临床意义和可能的作用机制.方法:采用免疫组织化学法检测于2010年1月至6月在河北医科大学第四医院乳腺科住院的86例ER阳性患者乳腺癌组织中Efp和Hk3的蛋白表达,并分析两者表达的相关性及与临床病理指标的关系.采用qRT-PCR法检测乳腺癌细胞MCF-7和MDA-MB-231中ER、Efp mRNA的表达情况,采用RT-PCR及Western blotting法检测雌激素刺激后ER阳性乳腺癌细胞MCF-7中Efp、Pkk3基因的表达变化,采用Western blotting法检测雌激素及蛋白酶抑制剂MG132处理后MCF-7细胞中Efp、Plk3的表达变化.结果:86例ER阳性的乳腺癌组织中,55例Efp表达阳性(64.0％),28例Plk3表达阳性(32.6％).Efp表达阳性组织中Plk3表达阳性为23.6％,Efp表达阴性组织中Plk3表达阳性为48.4％,Efp和Plk3蛋白表达存在明显的负相关(P＜0.05),Efp蛋白表达与乳腺患者的淋巴结转移状况呈明显正相关(P＜0.05),Plk3蛋白表达与乳腺癌患者的淋巴结转移状况呈明显负相关(P＜0.05).MCF-7细胞ER mRNA高表达,而MDA-MB-231细胞的ER mRNA低表达.MDA-MB-231细胞经雌激素刺激后,Efp mRNA的表达未见明显改变.MCF-7经雌激素刺激后Efp mRNA及蛋白的表达显著增加(P＜0.05),而Hk3 mRNA的表达未见明显改变,未检测到Plk3蛋白的表达.MG132处理后MCF-7细胞中Plk3的蛋白表达明显上调,MCF-7经雌激素刺激后,再用MG132处理,Efp的蛋白表达显著增加(P＜0.05),而Plk3蛋白表达明显下降(P＜0.05).结论:ER阳性乳腺癌中Efp和Plk3蛋白表达存在明显的负相关,Efp可促进Plk3的蛋白降解,并可能参与了ER阳性乳腺癌患者内分泌治疗的耐药过程.     

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.     

肿瘤抗原MAGE-A11促进ER介导的乳腺癌细胞MCF-7的增殖

目的：探讨黑素瘤抗原（melanoma antigen gene, MAGE）-A11对雌激素受体（estrogen receptor, ER）介导的乳腺癌MCF-7细胞增殖的影响。方法： 利用RT-PCR及Western blotting筛选出ER表达阳性的人乳腺癌MCF-7细胞作为模式细胞,采用基因转染、RT-PCR和Western blotting检测MAGE-A11对17β-雌二醇（17β-E）诱导的ER下游靶基因Efp表达的影响,采用免疫共沉淀法检测MCF-7细胞中MAGE-A11和ER蛋白的相互作用,采用MTT法和克隆形成实验分别检测MAGE-A11及17β-E处理对MCF-7细胞生存率和细胞克隆形成数的影响。结果： ER阳性MCF-7细胞经17β-E处理24 h后,下游靶基因Efp的mRNA（2.97±0.16 vs 1.71±0.09,P<0.05）和蛋白表达水平显著升高（2.65±0.12 vs 0.92±0.06, P<0.05）;转染MAGE-A11的MCF-7细胞经17β-E 24 h处理后,其Efp的mRNA（4.01±0.19 vs 2.97±0.16, P<0.05）及蛋白表达（3.52±015 vs 2.65±0.12, P<0.05）更显著增加。免疫共沉淀结果显示,外源性MAGE-A11与ER之间存在相互作用。MCF-7细胞经17β-E处理后细胞增殖率显著增加\[（152±6.7）% vs （108±4.8%）, P<0.05\],转染MAGE-A11的MCF-7细胞经17β-E处理后细胞增殖率更显著增加\[（181±8.6）% vs （152±6.7）%, P<0.05\];17β-E处理后MCF-7细胞克隆形成数显著增多\[（77±5) vs (18±2)个,P<0.05\],转染MAGE-A11的MCF-7细胞经17β-E处理后细胞的克隆形成数更显著增加\[（125±6）vs （77±5）个, P<0.05）。结论： 在ER阳性的乳腺癌MCF-7细胞中,MAGE-A11可通过与ER的相互作用增强ER介导的Efp的表达,从而促进细胞增殖,MAGE-A11可能成为ER阳性乳腺癌内分泌治疗耐药的靶基因。     

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。     

固定后乳腺癌细胞雌激素受体和孕激素受体的FCM和Western blot检测

背景与目的：雌激素受体(estrogen receptor,ER)和孕激素受体(progesterone receptor,PR)水平的定性、定量检测,对乳腺癌患者预后判断和内分泌治疗效果的评价具有重要意义。Western blot法和流式细胞术(flow cytometry,FCM)是蛋白质定性、定量分析的重要手段,但常规Western blot法要求提取新鲜样本的蛋白质。本研究拟建立固定后乳腺癌细胞ER和PR的Western blot检测方法,探索Western blot法和FCM对同批固定样本ER、PR进行同步分析的可行性。方法：取不同乳腺癌细胞株对数生长期新鲜细胞和固定细胞的蛋白提取物,分别用ERα单克隆抗体1D5和PR单克隆抗体PgR636以Western blot法对．ER、PR的表达情况进行检测,并与同期固定细胞的FCM检测结果进行比较。结果：经Westernblot法检测,T-47d、MCF-7、ZR-75-l细胞可见分子量正确的ERα清晰条带,固定T-47d和ZR-75-1细胞的ERα条带较新鲜细胞的条带浓,MM23l细胞ERα检测为阴性;T-47d和ZR-75-1细胞可见清晰且分子量正确的PR条带,固定细胞的PR条带较新鲜细胞的条带浓,MM23l和,MCF-7细胞PR检测为阴性;同期固定细胞ER、PR阳性表达的FCM检测结果与Western blot检测结果一致。结论：不同乳腺癌细胞在经0．25％多聚甲(paraformaldehyde,PFA)和75％乙醇固定后,可用于ER、PR的FCM定量检测,也可用于ER、PR的Western blot分析。     

舒肝凉血方与三苯氧胺合用对人乳腺癌细胞MCF-7生长及ER表达影响

[目的]了解舒肝凉血方与三苯氧胺合用对体外培养的雌激素受体阳性的人乳腺癌细胞MCF-7的生长及雌激素受体表达的影响.[方法]人乳腺癌细胞MCF-7分别加入终浓度20%的含药血清培养液,孵育24、48、72h,MTT法检测各组含药血清对细胞的生长抑制效应.MCF-7细胞加入20%的含药血清培养液,共同孵育48h,提取细胞蛋白质及总RNA,用Western blot法检测各组细胞中雌激素受体α表达,RT-PCR法检测各组细胞ERα mRNA的表达水平.[结果]MTT结果显示,三苯氧胺、中药、三苯氧胺 中药均可抑制MCF-7细胞的体外生长,且有时间依赖性,三苯氧胺加中药组抑制作用最强.采用RT-PCR检测到三苯氧胺组、中药组、三苯氧胺 中药组的ERαmRNA表达略低于对照组,统计学分析差异无显著性.Westem blot结果显示中药组ERα蛋白表达下调,三苯氧胺组及三苯氧胺 中药组的ERα蛋白表达上调.[结论]中药舒肝凉血方与三苯氧胺合用有协同效应,抑制乳腺癌MCF-7细胞的体外生长,并使ERα蛋白的表达上调.     

miR-181a表达水平与ER阳性乳腺癌对内分泌治疗敏感性的关系

目的:研究miR-181a表达水平与雌激素受体（estrogen receptor,ER）阳性乳腺癌对内分泌治疗敏感性之间的关系。方法:采用梯度递增法诱导乳腺癌他莫昔芬耐药细胞株，利用集落形成实验检测细胞对他莫昔芬的敏感性。利用RT-PCR法检测miR-181a表达的情况，利用KM-plotter分析miR-181表达与乳腺癌患者预后之间的关系。结果:我们成功的诱导了MCF-7他莫昔芬继发耐药细胞株TAM-R。RT-PCR分析结果显示:他莫昔芬继发耐药的TAM-R细胞株及原发他莫昔芬耐药BT474细胞株中miR-181a的表达水平均显著高于对他莫昔芬敏感的MCF-7细胞株。生存分析结果显示:miR-181a的表达水平与ER阴性乳腺癌患者的总生存无关，但在ER阳性乳腺癌中miR-181a表达高的患者总生存明显差于miR-181a低表达者。进一步分析结果显示:在ER阳性但未接受内分泌治疗的乳腺癌患者中miR-181a表达与总生存无关，但在ER阳性且接受过内分泌治疗的乳腺癌患者中miR-181a高表达者总生存显著差于miR-181a低表达者。结论:miR-181a高表达ER阳性乳腺癌患者对内分泌治疗敏感性差，miR-181a可能是预测ER 阳性乳腺癌对内分泌治疗敏感性的指标。     

雌激素调节人乳腺癌细胞CD147表达的研究

目的：探究雌激素对人乳腺癌细胞系中CD147表达的调节作用。方法：用雌激素处理人乳腺癌细胞系,RT-PCR及Real-time PCR定量检测用药前后细胞中CD147 mRNA表达水平变化,Western blot检测用药前后细胞中CD147蛋白表达水平变化。结果：经雌激素处理后的ER阳性人乳腺癌细胞系中CD147 mRNA及蛋白的表达均呈上升趋势,而ER阴性人乳腺癌细胞系则无明显变化。结论：雌激素通过ER激活CD147的表达,在乳腺癌的发生发展过程中发挥了重要的作用。     

雌激素受体β及其剪切变异体与乳腺癌他莫昔芬耐药的关系

目的探讨雌激素受体（ER）亚型（ERβ）及其剪切变异体（ERβcx）的表达与乳腺癌他莫昔芬耐药的关系。方法 （1）对乳腺癌他莫西芬敏感MCF-7细胞和他莫西芬耐药MCF-7细胞进行培养,利用去甲基化物5-氮杂胞苷（5-Aza-2-deoxycytidine,5-AZA-CdR）去甲基化的作用,对MCF-7细胞进行药物处理获得MCF-75-AZA-CdR细胞,采用Western blot方法检测3组细胞中ERβ和ERβcx蛋白的表达。（2）取对数生长期生长良好的乳腺癌MCF-7细胞株,按2.5×103细胞/孔接种于96孔细胞培养板板中,实验组分为他莫细芬处理的MCF-7细胞（MCF-7＋TAM组）和MCF-75-AZA-CdR细胞（MCF-75-AZA-CdR细胞＋TAM组）,对照组为MCF-7细胞,采用MTT比色法,观察3组细胞的增殖情况。统计学分析采用单因素方差分析和重复测量方差分析。结果 （1）ERβ蛋白在他莫西芬敏感MCF-7细胞中的表达高于他莫西芬耐药的MCF-7细胞,两组细胞间差异有显著的统计学意义（P=0.000）;ERβcx蛋白表达在两组之间差异无统计学意义（P=0.366）。MCF-75-AZA-CdR细胞ERβ和ERβcx蛋白表达均高于他莫西芬敏感MCF-7细胞和他莫西芬敏耐药MCF-7细胞（P均=0.000）。（2）与对照组MCF-7细胞相比,他莫西芬明显降低了MCF-7＋TAM组和MCF-75-AZA-CdR细胞＋TAM组的细胞增值速度并抑制细胞生长;且他莫西芬抑制细胞增殖作用MCF-75-AZA-CdR细胞＋TAM组强于MCF-7＋TAM组（P=0.000）。结论 ERβ蛋白在他莫西芬敏感MCF-7细胞中的表达高。MCF-75-AZA-CdR细胞中ERβ和ERβcx蛋白的表达均高。他莫西芬抑制细胞增殖作用在他莫西芬处理的MCF-75-AZA-CdR细胞中强     

稳定转染ERβ基因对MCF-7乳腺癌细胞系生长特性的影响

目的研究在不同处理因子作用下,外源基因ERβ的表达对MCF-7乳腺癌细胞系生长特性的影响。方法利用lipofectamine 2000将ERβ真核表达载体pCDNA3,ERβ导入MCF-7乳腺癌细胞系。采用含雌激素应答元件（ERE）的荧光素酶报告基因及Western blot方法,检测转染细胞中ERβ的转录活性和蛋白表达水平,筛选阳性克隆。以亲本细胞MCF-7及转染空载体质粒pCDNA3的MCF-7细胞为对照,在雌激素E2和雌激素受体拮抗剂4-OHT作用下观察细胞的生长特点。结果在转染ERβ基因的MCF3细胞系中,ERβ的转录激活活性明显升高;Western blot检测证实,ERβ的蛋白表达水平显著增高。在无处理因子情况下,外源基因ERβ在MCF-7细胞系中的表达对细胞的形态及生长速度无明显影响。与亲本细胞MCF-7及转染空载体质粒的MCF-7细胞相比,稳定转染ERβ的MCF-7细胞对雌激素的敏感性下降,但对4-OHT处理的敏感性无明显减少。结论外源性ERβ基因在MCF-7乳腺癌细胞中的稳定表达不增加对4-OHT的耐药性,但使之对雌激素的敏感性下降。     

Cytokine receptor CXCR4 mediates estrogen-independent tumorigenesis, metastasis, and resistance to endocrine therapy in human breast cancer

Estrogen independence and progression to a metastatic phenotype are hallmarks of therapeutic resistance and mortality in breast cancer patients. Metastasis has been associated with chemokine signaling through the SDF-1-CXCR4 axis. Thus, the development of estrogen independence and endocrine therapy resistance in breast cancer patients may be driven by SDF-1-CXCR4 signaling. Here we report that CXCR4 overexpression is indeed correlated with worse prognosis and decreased patient survival irrespective of the status of the estrogen receptor (ER). Constitutive activation of CXCR4 in poorly metastatic MCF-7 cells led to enhanced tumor growth and metastases that could be reversed by CXCR4 inhibition. CXCR4 overexpression in MCF-7 cells promoted estrogen independence in vivo, whereas exogenous SDF-1 treatment negated the inhibitory effects of treatment with the anti-estrogen ICI 182,780 on CXCR4-mediated tumor growth. The effects of CXCR4 overexpression were correlated with SDF-1-mediated activation of downstream signaling via ERK1/2 and p38 MAPK (mitogen activated protein kinase) and with an enhancement of ER-mediated gene expression. Together, these results show that enhanced CXCR4 signaling is sufficient to drive ER-positive breast cancers to a metastatic and endocrine therapy-resistant phenotype via increased MAPK signaling. Our findings highlight CXCR4 signaling as a rational therapeutic target for the treatment of ER-positive, estrogen-independent breast carcinomas needing improved clinical management.     

Estrogen-responsive finger protein as a new potential biomarker for breast cancer.

PURPOSE: Estrogen-responsive finger protein (Efp) is a member of RING finger-B box-Coiled Coil family and is also a downstream target of estrogen receptor alpha. Previously, Efp was shown to mediate estrogen-induced cell growth, which suggests possible involvement in the development of human breast carcinomas. In this study, we examined expression of Efp in breast carcinoma tissues and correlated these findings with various clinicopathologic variables. EXPERIMENTAL DESIGN: Thirty frozen specimens of breast carcinomas were used for immunohistochemistry and laser capture microdissection/real-time PCR of Efp. Immunohistochemistry for Efp was also done in 151 breast carcinoma specimens fixed with formalin and embedded in paraffin wax. RESULTS: Efp immunoreactivity was detected in breast carcinoma cells and was significantly associated with the mRNA level (n = 30). Efp immunoreactivity was positively associated with lymph node status or estrogen receptor alpha status and negatively correlated with histologic grade or 14-3-3sigma immunoreactivity (n = 151). Moreover, Efp immunoreactivity was significantly correlated with poor prognosis of breast cancer patients, and multivariate analyses of disease-free survival and overall survival for 151 breast cancer patients showed that Efp immunoreactivity was the independent marker. CONCLUSIONS: Our data suggest that Efp immunoreactivity is a significant prognostic factor in breast cancer patients. These findings may account for an oncogenic role of Efp in the tumor progression of breast carcinoma.     

E R阳性乳腺癌中FGFR1蛋白的表达与ER及预后的关系

背景与目的：乳腺癌是严重危害女性健康的常见恶性肿瘤之一，内分泌治疗是乳腺癌综合治疗中的重要措施之一。约30%激素敏感型乳腺癌患者并不能从内分泌治疗中获益。成纤维细胞生长因子受体1（fibroblast growth factor receptors 1，FGFR1）的表达与雌激素受体（estrogen receptor，ER）阳性乳腺癌患者内分泌治疗耐药可能有关。该研究旨在探讨ER阳性乳腺癌中FGFR1蛋白的表达水平对乳腺癌临床病理学特征及预后的影响。方法：选取哈尔滨医科大学附属肿瘤医院2008年9月-2011年12月收治的184例ER阳性乳腺癌患者，通过免疫组织化学方法检测FGFR1蛋白的表达；采用χ²检验评估FGFR1蛋白水平与乳腺癌临床病理学特征的关系；采用Spearman相关分析评估变量间是否存在相关性；运用COX回归及Kaplan-Meier法分析FGFR1表达水平对乳腺癌预后的影响。结果：在ER阳性乳腺癌中，FGFR1高表达的患者更易发生区域淋巴结转移（P=0.012，r=0.186），且FGFR1的表达水平与ER的表达水平之间存在显著的负相关关系（P=0.011，r=-0.221）。COX单因素分析显示，TNM分期、区域淋巴结转移情况、Ki-67阳性率及FGFR1表达情况与ER阳性乳腺癌预后有关；进一步进行多因素分析发现，淋巴结转移情况（OR=1.744，95%CI：1.002~3.034，P=0.049）和Ki-67阳性率（OR=1.882，95%CI：1.015~3.491，P=0.045）是ER阳性乳腺癌的独立风险因素。Kaplan-Meier生存分析提示，FGFR1高表达患者预后不良（P=0.036）。结论：在ER阳性乳腺癌中，FGFR1蛋白水平与患者ER的表达水平呈显著负相关，且FGFR1高表达提示患者预后不良。     

Loss of pigment epithelium-derived factor: a novel mechanism for the development of endocrine resistance in breast cancer

Introduction

Despite the benefits of endocrine therapies such as tamoxifen and aromatase inhibitors in treating estrogen receptor (ER) alpha-positive breast cancer, many tumors eventually become resistant. The molecular mechanisms governing resistance remain largely unknown. Pigment epithelium-derived factor (PEDF) is a multifunctional secreted glycoprotein that displays broad anti-tumor activity based on dual targeting of the tumor microenvironment (anti-angiogenic action) and the tumor cells (direct anti-tumor action). Recent studies indicate that PEDF expression is significantly reduced in several tumor types, including breast cancer, and that its reduction is associated with disease progression and poor patient outcome. In the current study, we investigated the role of PEDF in the development of endocrine resistance in breast cancer.

Methods

PEDF mRNA and protein levels were measured in several endocrine-resistant breast cancer cell lines including MCF-7:5C, MCF-7:2A, and BT474 and in endocrine-sensitive cell lines MCF-7, T47D, and ZR-75-1 using real-time PCR and western blot analyses. Tissue microarray analysis and immunohistochemistry were used to assess the PEDF protein level in tamoxifen-resistant breast tumors versus primary tumors. Lentiviruses were used to stably express PEDF in endocrine-resistant breast cancer cell lines to determine their sensitivity to tamoxifen following PEDF re-expression.

Results

We found that PEDF mRNA and protein levels were dramatically reduced in endocrine-resistant MCF-7:5C, MCF-7:2A, and BT474 breast cancer cells compared with endocrine-sensitive MCF-7, T47D, and ZR-75-1 cells, and that loss of PEDF was associated with enhanced expression of p^Ser167ERα and the receptor tyrosine kinase rearranged during transfection (RET). Importantly, we found that silencing endogenous PEDF in tamoxifen-sensitive MCF-7 and T47D breast cancer cells conferred tamoxifen resistance whereas re-expression of PEDF in endocrine-resistant MCF-7:5C and MCF-7:2A cells restored their sensitivity to tamoxifen in vitro and in vivo through suppression of RET. Lastly, tissue microarray studies revealed that PEDF protein was reduced in ~52.4% of recurrence tumors (31 out of 59 samples) and loss of PEDF was associated with disease progression and poor patient outcome.

Conclusion

Overall, these findings suggest that PEDF silencing might be a novel mechanism for the development of endocrine resistance in breast cancer and that PEDF expression might be a predictive marker of endocrine sensitivity.     

Effect of estrogen, tamoxifen and epidermal growth factor on the transcriptional regulation of vascular endothelial growth factor in breast cancer cells

BACKGROUND: VEGF (Vascular Endothelial Growth Factor) is a key factor of angiogenesis and high tissue VEGF levels are related to a poor prognosis in breast cancer. MATERIALS AND METHODS: By semi-quantitative RT-PCR, we determined the relative expressions of VEGF mRNA in MCF-7 (both ER-alpha+ and ER-beta+ (mainly ER-alpha+), PR+, bcl-2+, EGFR-) and MB-MDA-231 (only ER-beta+, PR-, EGFR-) breast cancer cells which were treated with estrogen, tamoxifen and EGF (Epidermal Growth Factor). RESULTS: In MCF-7 cell lines, estrogen induced the expression of VEGF mRNA while tamoxifen reduced its expression. Estrogen and tamoxifen did not confer any significant effect on MB-MDA-231 cells and EGF showed no significant effect on MCF-7 or MB-MDA-231. CONCLUSION: Reduced VEGF mRNA expression of MCF-7 cells treated with tamoxifen may be related to the antagonistic effect of tamoxifen on ER-positive breast cancer, and this antagonistic effect may be related to ER-alpha.     

Expression and regulation of Cyr61 in human breast cancer cell lines

We have shown that Cyr61, an angiogenic regulator, is overexpressed in invasive and metastatic human breast cancer cells and tumor biopsies. We have further demonstrated that Cyr61 promotes acquisition of estrogen-independence and anti-estrogen resistance in vivo in breast cancer cells. Moreover, we have demonstrated that Cyr61 induces tumor formation and tumor vascularization in vivo, events mediated through the activation of the MAPK and the Akt signaling pathways. Here we investigate how Cyr61 expression is regulated in both estrogen receptor (ER)-positive and ER-negative breast cancer cells. We demonstrate that Cyr61 mRNA and protein expression is inducible by estrogen and anti-estrogens in ER-positive breast cancer cells. We show that a labile protein as well as a negative regulator might be involved in Cyr61 expression in estrogen-dependent breast cancer cells. Other important regulators of Cyr61 expression in breast cancer cells that we found are the phorbol ester TPA, vitamin D, and retinoic acid. TPA causes positive regulation of Cyr61 expression in ER-positive MCF-7 cells. Vitamin D induces a transient stimulatory effect on Cyr61 gene expression. Lastly, retinoic acid has a negative effect on Cyr61 expression and downregulates its expression in MCF-7 cells. Interestingly, most of these effects are not seen in aggressive breast cancer cells that do not express ER and express high levels of Cyr61, such as the MDA-MB-231 cells. Our results are in agreement with our knowledge that Cyr61 promotes tumor growth, and that tumor-promoting agents have a positive impact on cells that express low levels of Cyr61, such as the ER-positive breast cancer cells; however, these agents have no significant effect on cells that express high levels of Cyr61. Our findings suggest an association between increased Cyr61 expression and an aggressive phenotype of breast cancer cells.     

Leptin as a Potential Target for Estrogen Receptor-Positive Breast Cancer

Purpose

Leptin is a potent adipokine that plays a significant role in tumor development and the progression of breast cancer. The aim of this study was to evaluate whether leptin affects the response to tamoxifen treatment in estrogen receptor (ER)-positive breast cancer cells.

Methods

Leptin, leptin receptor (Ob-R), and activation of signaling pathways were studied by Western immunoblotting. The effects of leptin on tamoxifen-dependent growth inhibition were studied in MCF-7 and T-47D cells.

Results

Leptin was expressed in MCF-7 and T-47D and had a proliferative effect on MCF-7 cells. Leptin significantly inhibited the antiestrogenic effect of tamoxifen in both cells only under β-estradiol (E2) (20 nM) conditions. In MCF-7, the inhibitory effect against tamoxifen was a result from the activation of the ERK1/2 and STAT3 signal transduction pathway.

Conclusion

Leptin interferes with the effects of tamoxifen under E2 stimulated conditions in ER-positive breast cancer cells. These results imply that inhibition of leptin is expected to enhance the response to tamoxifen in ER-positive breast cancer cells, and, therefore, could be a promising way to overcome endocrine resistance.