获得性他莫昔芬耐受MCF-7细胞膜受体的变化及格列卫的逆转作用

目的：探讨耐受他莫昔芬(TAM)的MCF-7细胞膜受体等的变化及格列卫对耐药的逆转作用。方法：MTY法检测TAM对E2、EGF、Insulin刺激的MCF-7增殖的抑制作用；流式细胞术检测与10^-7mol／LTAM孵育8周、16周后的MCF-7细胞ER、PR、EGFR及VEGF的变化，MTY法检测格列卫对耐药的逆转作用。结果：TAM抑制E2、EGF、Insulin刺激的MCF-7增殖；耐受TAM的MCF-7ER、PR表达率由父代的93％、91％下降为41％、36％，EGFR由10％上升为39％，VEGF由36％下降至30％，对EGF刺激的增殖更敏感，格列卫可增强TAM的生长抑制作用。结论：耐受TAM的MCF-7细胞ER、PR表达下降，EGFR表达升高，EGF／EGFR刺激的细胞增殖作用增强，格列卫可能作为对TAM获得性耐药后逆转用药方案或贯序用药方案。     

miR -21通过调控 PTEN 介导乳腺癌他莫昔芬耐药的作用机制

目的：研究 miR -21在乳腺癌他莫昔芬耐药中的作用,寻求逆转他莫昔芬耐药的靶点。方法：荧光实时定量 PCR（RT - QPCR）检测乳腺癌 MCF -7细胞与乳腺癌他莫昔芬耐药细胞株 MCF -7/ TAM 细胞中miR -21的表达;将 miR -21 mimics 转染到 MCF -7细胞内,将 miR -21 inhibitors 转染到 MCF -7/ TAM 细胞内,并应用 RT - QPCR 分别检测细胞内 miR -21的表达变化,给予细胞4-羟他莫昔芬（4- hydroxytamoxifen, OHT）处理后,利用 MTT 法检测细胞增殖的变化;转染 MCF -7/ TAM 细胞 miR -21 inhibitors 及 mimics,利用RT - QPCR 检测细胞中 PTEN 的表达变化。结果：miR -21在 MCF -7/ TAM 细胞表达高于 MCF -7细胞,转染 miR -21 mimics 的 MCF -7细胞 miR -21高表达,PTEN 表达降低,转染 miR -21 inhibitors 的 MCF -7/TAM 细胞 miR -21表达降低,PTEN 表达增高;过表达 miR -21的 MCF -7细胞给予 OHT 处理后,细胞的增殖抑制不明显,而沉默 miR -21的 MCF -7/ TAM 细胞给予 OHT 处理后,细胞增殖明显受到阻滞;转染耐药细胞 miR -21 inhibitors 后,PTEN 表达增高,转染 miR -21 mimics 后,PTEN 表达降低。结论：miR -21通过调控PTEN 的表达在乳腺癌 TAM 耐药中发挥重要作用。     

托瑞米芬和他莫昔芬对MCF7/ADR多药耐药的逆转作用

目的:研究托瑞米芬(toremifene,TOR)和他莫昔芬(tamoxifen,TAM)对乳腺癌耐阿霉素细胞株MCF7/ADR多药耐药的逆转作用及其可能作用机制。方法:采用SRB法测量TOR、TAM对MCF7/ADR细胞的耐药逆转倍数;荧光显微镜、流式细胞仪测定加入TOR、TAM前后耐药细胞内荧光含量表达变化;Westernblotting检测TOR、TAM对P-gp表达的影响。结果:(5、10、20)μmol/L的TOR和TAM对MCF7/ADR耐药的逆转倍数分别为(1.5、7.0、35.4)倍和(2.0、5.4、30.7)倍,而对MCF7/S细胞没有显著性作用。加入TOR、TAM后,MCF7/ADR细胞内ADR荧光的呈现由核外进入核内,荧光含量亦具浓度依赖性提高。MCF7/S细胞P-gp表达阴性,而MCF/ADR细胞P-gp表达阳性。TOR[(5、10、20)μmol/L]与TAM[(5、10)μmol/L]对MCF7/ADR细胞株中的P-gp表达未产生显著性抑制作用。结论:TOR可明显逆转MCF7/ADR细胞株对ADR的耐药性,增强其细胞毒作用,逆转强度与TAM相当。其机制可能是通过对P-gp结构功能的调控来逆转耐药性,而不是通过下调MDR1基因的蛋白水平表达。     

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。     

托瑞米芬和他莫昔芬对MCF7/ADR多药耐药的逆转作用

目的：研究托瑞米芬（toremifene,TOR）和他莫昔芬（tamoxifen,TAM）对乳腺癌耐阿霉素细胞株MCF7/ADR多药耐药的逆转作用及其可能作用机制。方法：采用SRB法测量TOR、TAM对MCF7/ADR细胞的耐药逆转倍数;荧光显微镜、流式细胞仪测定加入TOR、TAM前后耐药细胞内荧光含量表达变化;Westernblotting检测TOR、TAM对P-gp表达的影响。结果：（5、10、20）μmol/L的TOR和TAM对MCF7/ADR耐药的逆转倍数分别为（1.5、7.0、35.4）倍和（2.0、5.4、30.7）倍,而对MCF7/S细胞没有显著性作用。加入TOR、TAM后,MCF7/ADR细胞内ADR荧光的呈现由核外进入核内,荧光含量亦具浓度依赖性提高。MCF7/S细胞P-gp表达阴性,而MCF/ADR细胞P-gp表达阳性。TOR[（5、10、20）μmol/L]与TAM[（5、10）μmol/L]对MCF7/ADR细胞株中的P-gp表达未产生显著性抑制作用。结论：TOR可明显逆转MCF7/ADR细胞株对ADR的耐药性,增强其细胞毒作用,逆转强度与TAM相当。其机制可能是通过对P-gp结构功能的调控来逆转耐药性,而不是通过下调MDR1基因的蛋白水平表达。     

维甲酸联合他莫昔芬对人乳腺癌细胞株作用的研究

目的:探讨他莫昔芬(TAM)与维甲酸(ATRA)联合对人乳腺癌他莫昔芬耐药株的作用.方法:在体外培养条件下,分别或联合应用ATRA和TAM作用于MCF-7人乳腺癌他莫昔芬耐药株(MCF-7/T)及敏感组(MCF-7/S).MTT比色法分析细胞生长抑制作用;用流式细胞仪(FCM)检测细胞周期分布、凋亡率及用药前后Bcl-2、Bax、Fas和FasL蛋白的变化.结果:TAM能抑制ER阳性MCF-7/S的生长,阻滞细胞周期于G0/G1期,并可诱导细胞凋亡,TAM不能抑制MCF-7/T的生长; ATRA预处理细胞24 h后,TAM抗乳腺癌细胞MCF-7/S的作用增强,且恢复了MCF-7/T对TAM的敏感性.ATRA与TAM联用后,MCF-7/T细胞Bcl-2蛋白表达下调,细胞Bax、Fas和FasL蛋白表达水平未见明显变化.结论:体外条件下,TAM通过影响细胞周期、诱导细胞凋亡而发挥抗ER阳性MCF-7/S作用;视黄酸能加强TAM对激素敏感细胞MCF-7/S的抗乳腺癌作用,恢复耐受细胞MCF-7/T对TAM的敏感性.同时恢复TAM对MCF-7/T的促凋亡作用.     

子宫肌瘤组织雌、孕激素受体和表皮生长因子受体的研究

目的 :探讨雌、孕激素和表皮生长因子与子宫肌瘤生长的关系。方法 :应用免疫组化ABC法检测 4 0例子宫肌瘤患者子宫组织雌激素受体 (ER)、孕激素受体 (PR)和表皮生长因子受体(EGFR)的表达 ,同时用磁性微粒载体免疫酶联法 (IEMA)测定血清雌二醇 (E2 )和孕酮 (P)水平 ;用酶联免疫吸附法 (EL ISA)测定血清表皮生长因子 (EGF)水平。结果 :子宫肌瘤组织 ER、EGFR表达显著高于子宫肌层组织 (P<0 .0 5 ,P<0 .0 1) ,子宫肌瘤组织 PR表达显著高于 ER表达 (P<0 .0 0 5 ) ,肌瘤组织和肌层组织分泌期 EGFR表达显著高于增生期 (P<0 .0 5 )。子宫肌瘤组分泌期血清 E2 、P水平显著高于对照组 (P<0 .0 5 ,P<0 .0 0 1) ,肌瘤组和对照组分泌期 EGF水平均明显高于增生期 (P<0 .0 0 1)。结论 :子宫肌瘤的生长与血清 E2 、P水平升高和子宫组织 ER、PR和 EGFR的表达增强有关。P可能诱导 EGF的分泌和 EGFR的表达     

雌激素受体β在乳腺癌他莫昔芬内分泌治疗耐药中的作用

目的：探讨雌激素受体β（estrogen receptor β,ERβ）的表达与乳腺癌他莫昔芬（tamoxifen,TAM）内分泌治疗耐药的相关性及其机制。方法：以前期构建的ERα/ERβ不同表达的人乳腺癌MCF-7细胞株\[M/HK（阴性对照）、M/siα（ERαlow/ERβhigh）、M/siβ（ERαhigh/ERβlow）细胞\]为研究对象,MTT法评估乳腺癌细胞对TAM的耐药性;用半定量RT-PCR法检测细胞中耐药相关基因MDR1、TOPOⅡ、LRP和GST-π的mRNA表达水平,用Western blotting法检测细胞中耐药相关信号通路MAPK、PI3K/Akt的p-ERK、p-Akt蛋白表达水平。结果：与对照组MCF-7细胞相比,MCF-7细胞中的ERβ高表达可促进高浓度TAM（1、5、10 μmol/L）对MCF-7细胞增殖的抑制作用\[（45.788 ± 1.641）% vs （24.288±1.170）%,（57.899±1.583）% vs（31.499±1.978）%,（59.853 ±1.648）% vs（38.039±1.482）%;均P<0.05 ）\],该抑制作用与TAM浓度呈剂量依赖性。ERβ高表达可显著抑制MCF-7细胞耐药基因MDR1、TOPOⅡ、LRP的 mRNA表达水平（0.431±0.032 vs 0.932±0.083,0.234±0.008 vs 0.391±0.002,0.47±0.028 vs 0.586±0.036;均P<0.05);可显著下调Akt和ERK蛋白的磷酸化水平（0224±0.006 vs 0.437±0.007,0.367±0.015 vs 0.756±0.039;均P<0.05)。结论： ERβ表达水平可影响乳腺癌细胞MCF-7对TAM的耐药性,该作用机制可能与耐药基因的表达及PI3K/ AKT、MAPK信号通路激活有关。     

卵巢癌细胞ER亚型和p160共激活因子表达及其与他莫西芬和雌激素敏感相关性

目的:分析比较4种常见的人上皮性卵巢癌细胞系(A2780、CAOV-3、SKOV-3和ES-2)雌激素受体(ER)亚型及p160共激活因子表达及其对他莫西芬(TAM)和雌激素敏感性的关系.方法:采用免疫印迹法和RT-PCR技术检测ERα、ERβ及p160共激活因子的表达,采用MTT试验测定卵巢癌细胞对TAM和17β-雌二醇(E2)的敏感性.结果:4种卵巢癌细胞均表达ERα,其中A2780细胞较低,CAOV-3和SKOV-L3细胞较高,ES-2细胞居中;ERβ的表达情况则与ERα恰好相反;3种p160共激活因子mRNA的表达水平均以A2780细胞为最低,而ES2、SKOV-3和CA-OV-3细胞则依次升高;4种卵巢癌细胞对TAM的敏感性不同,其中A2780细胞最敏感,CAOV-3、SKOV-3和ES-2细胞则有不同程度的耐药性.其耐药倍数分剐为4.98、3.75和2.66;除SKOV-3细胞外,E2对CAOV-3、ES-2和A2780细胞均有不同程度的促增殖作用,其强度依次降低.结论:卵巢癌细胞ERβ表达水平与其对TAM的敏感性呈正相关趋势;3种p160共激活因子表达水平与卵巢癌细胞对TAM的敏感性呈负相关趋势,与ERα而非ERβ的表达水平相一致.     

Investigation of elemene-induced reversal of tamoxifen resistance in MCF-7 cells through oestrogen receptor α (ERα) re-expression

Endocrine therapy is an important therapeutic approach for the treatment of oestrogen receptor (ER)-positive breast cancer. However, a number of these endocrine therapies can fail when the tumour loses its ER expression during treatment. To date, few studies have explored the potential clinical significance of traditional Chinese medicine in inducing the reversal of resistance to endocrine therapy in breast cancers. We used the ER??-negative MCF7 breast cancer cell line to create a tamoxifen (TAM)-resistant cell line, MCF7/TAM cells. After treating MCF7/TAM cells with ELE to induce the re-expression of ER??, we investigated the role and molecular mechanisms by which elemene (ELE) promotes the reversal of resistance to endocrine therapy. We discovered that treatment with 10???g/ml ELE restored the sensitivity of MCF7/TAM cells to TAM. RT-PCR analysis revealed that ELE treatment upregulated ER?? mRNA levels in MCF7/TAM cells, and immunohistochemistry confirmed the upregulation of ER?? expression. Western blot analysis revealed that ELE treatment decreased the protein expression levels of Ras, MEK1/2 and p-ERK1/2 in MCF7/TAM cells. The loss of ER?? expression was the primary reason for TAM resistance in MCF7 cells. The ELE-induced reversal of TAM resistance was mediated by the upregulation of ER?? mRNA and the re-expression of ER?? through the MAPK pathway.     

The effects of gefitinib in tamoxifen‐resistant and hormone‐insensitive breast cancer: A phase II study

Estrogen receptor (ER)‐positive acquired tamoxifen‐resistant (TAM‐R) MCF‐7 breast cancer cell lines exhibit epidermal growth factor receptor (EGFR) expression/signaling and are growth‐inhibited by gefitinib (IRESSA). We examined the effect of gefitinib on ER‐positive TAM‐R and ER‐negative hormone‐insensitive breast cancer in a Phase II study. Fifty‐four patients with breast cancer [ER‐positive/acquired TAM‐R (n = 28); ER‐negative (n = 26)] received oral gefitinib 500 mg/day. Tumor biopsies were taken pre‐ (n = 28) and 8 weeks post‐treatment (n = 14 matched samples). Gefitinib was well tolerated and the clinical benefit rate (objective response or stable disease >24 weeks) was 33.3% overall (n = 18/54), and 53.6 and 11.5% in ER‐positive/TAM‐R and ER‐negative patients, respectively. Pretreatment ER and progesterone receptor‐positivity were associated with response (p < 0.001 and 0.016, respectively) and longer progression‐free survival (PFS; p= 0.001 and 0.013, respectively). All patients expressed EGFR, but high pretreatment levels predicted poorer outcome (p = 0.005) and shorter PFS (p = 0.012) with gefitinib. In patients with clinical benefit, reduced Ki67 staining during treatment (p = 0.024) was commonly observed, and those with >10% decline in EGFR phosphorylation demonstrated parallel decreases in ERK1/2 MAPK phosphorylation. Acquired tamoxifen resistance appears in part mediated through EGFR signaling and can be blocked with gefitinib.     

Endocrine resistance associated with activated ErbB system in breast cancer cells is reversed by inhibiting MAPK or PI3K/Akt signaling pathways

Endocrine therapy resistance is one of the main challenges in the treatment of estrogen receptor positive (ER+) breast cancer patients. This study showed that two ER+ human breast carcinoma cell lines derived from MCF‐7 (MVLN cells) that have acquired under OH‐Tamoxifen selection two distinct phenotypes of endocrine resistance both displayed constitutive activation of the PI3K/Akt and MAPK pathways. Aberrant expression and activation of the ErbB system (phospho‐EGFR, phospho‐ErbB2, phospho‐ErbB3, over‐expression of ErbB4 and over‐expression of several ErbB ligands) were also observed in the two resistant cell lines, suggesting the existence of an autocrine loop leading to constitutive activation of MAPK and PI3K/Akt survival pathways. The recent clinical use of specific signal transduction inhibitors is one of the most promising therapeutic approaches in breast cancers. The MEK inhibitor PD98059 and the PI3K inhibitor LY294002 were both able to enhance the cytostatic effect of OH‐Tamoxifen or fulvestrant on MVLN sensitive cells. In the two resistant cell lines, inhibition of the MAPK or the PI3K/Akt pathways associated with endocrine therapy was sufficient to reverse OH‐Tamoxifen or fulvestrant resistance. Investigating the effect of a combination of both inhibitors on the reversion of OH‐Tamoxifen and fulvestrant resistance in the two resistant cell lines suggested that, in clinical practice, a strategy combining the two inhibitors would be the best approach to target the different endocrine resistance phenotypes possibly present in a tumor. In conclusion, the combination of MAPK and PI3K inhibitors represents a promising strategy to overcome endocrine therapy resistance in ER+ breast cancer patients.     

Tumor‐associated macrophages secrete CC‐chemokine ligand 2 and induce tamoxifen resistance by activating PI3K/Akt/mTOR in breast cancer

Breast cancer is the most prevalent malignancy among women. Although endocrine therapy is effective, the development of endocrine resistance is a major clinical challenge. The tumor microenvironment (TME) promotes tumor malignancy, and tumor‐associated macrophages (TAM) within the TME play a crucial role in endocrine resistance. Herein, we aimed to elucidate the relationship between TAM and the endocrine‐resistant phenotype of breast cancer. Macrophages were cultured with conditioned medium (CM) from tamoxifen‐sensitive (MCF7‐S) or ‐resistant (MCF7‐R) MCF7 breast cancer cells. M2 polarization was detected by CD163 immunofluorescence. To determine the effect on endocrine resistance, MCF7 cells were cultured in the supernatant of different TAM, and then treated with tamoxifen. CC‐chemokine ligand 2 (CCL2) immunohistochemistry was carried out on pathological sections from 100 patients with invasive estrogen receptor‐positive breast cancer. We found that macrophages cultured in the CM of MCF7‐S and MCF7‐R cells were induced into TAM, with a more obvious M2 polarization in the latter. Tamoxifen resistance was increased by culture in TAM medium. TAM secreted CCL2, which increased endocrine resistance in breast cancer cells through activation of the PI3K/Akt/mTOR signaling pathway. High expression of CCL2 was correlated with infiltration of CD163+macrophages (r = 0.548, P < .001), and patients with high CCL2 expression presented shorter progression‐free survival than those with low CCL2 expression (P < .05). We conclude that CCL2 secreted by TAM activates PI3K/Akt/mTOR signaling and promotes an endocrine resistance feedback loop in the TME, suggesting that CCL2 and TAM may be novel therapeutic targets for patients with endocrine‐resistant breast cancer.     

Fulvestrant regulates epidermal growth factor (EGF) family ligands to activate EGF receptor (EGFR) signaling in breast cancer cells

Estrogen receptor-α (ER) targeted therapies are routinely used to treat breast cancer. However, patient responses are limited by resistance to endocrine therapy. Breast cancer cells resistant to the pure steroidal ER antagonist fulvestrant (fulv) demonstrate increased activation of epidermal growth factor receptor (EGFR) family members and downstream ERK signaling. In this study, we investigated the effects of fulv on EGFR signaling and ligand regulation in several breast cancer cell lines. EGFR/HER2/HER3 phosphorylation and ERK1,2 activation were seen after 24–48 h after fulvestrant treatment in ER-positive breast cancer cell lines. 4-Hydroxy-tamoxifen and estradiol did not cause EGFR activation. Fulvestrant did not affect EGFR expression. Cycloheximide abolished the ability of fulv to activate EGFR suggesting the autocrine production of EGFR ligands might be responsible for fulvestrant induced EGFR signaling. qRT-PCR results showed fulv differentially regulated EGFR ligands; HB-EGF mRNA was increased, while amphiregulin and epiregulin mRNAs were decreased. Fulvestrant induced EGFR activation and upregulation of EGFR ligands were ER dependent since fulv treatment in C4-12, an ER-negative cell line derivative of MCF-7 cells, did not result in EGFR activation or change in ligand mRNA levels. ER downregulation by siRNA induced similar EGFR activation and regulation of EGFR ligands as fulvestrant. Neutralizing HB-EGF antibody blocked fulv-induced EGFR activation. Combination of fulv and EGFR family tyrosine kinase inhibitors (erlotinib and lapatinib) significantly decreased EGFR signaling and cell survival. In conclusion, fulvestrant-activated EGFR family members accompanied by ER dependent upregulation of HB-EGF within 48 h. EGF receptor or ligand inhibition might enhance or prolong the therapeutic effects of targeting ER by fulvestrant in breast cancer.     

Acquired antiestrogen resistance in MCF-7 human breast cancer sublines is not accomplished by altered expression of receptors in the ErbB-family

Development of acquired resistance against antiestrogen treatment is a serious problem in human breast cancer, and knowledge of alterations resulting in resistance is important for selection of further treatment. To mimic the clinical situation we have established a series of MCF-7 human breast cancer cell lines by long term treatment with the antiestrogens tamoxifen, ICI 164,384, and ICI 182,780. Common for these cell lines is a decreased expression of the estrogen receptor (ER). In human breast cancer, lack of response to endocrine therapy is often associated with decreased expression of the estrogen receptor and increased expression of epidermal growth factor receptor (EGFR) and/or HER-2/neu (ErbB-2). Our antiestrogen resistant cell lines did not express altered levels of EGFR, HER-2/neu, ErbB-3, or ErbB-4. Estrogen and antiestrogen regulation of HER-2/neu expression was essentially similar in parent and resistant MCF-7 cells. Treatment with antibodies to HER-2/neu (Herceptin^TM) did not affect growth of MCF-7 cells or resistant cells, indicating that in this in vitro model system, acquired antiestrogen resistance does not emerge from activation of the HER-2/neu signaling pathway. In MCF-7 cells transfected with HER-2/neu and/or ErbB-3, overexpression alone did not result in resistance. However, addition of heregulinl-1 abolished the inhibitory activity of ICI 182,780 on both vector and HER-2/neu/ErbB-3 transfected MCF-7 cells, demonstrating that activation of the HER-2/neu receptor signaling pathway can override the growth inhibitory effect of ICI 182,780.     

Characterization of tamoxifen stimulated MCF-7 tumor variants grown in athymic mice

The non-steroidal antiestrogen tamoxifen (TAM) is successfully used to treat all stages of breast cancer in both pre- and postmenopausal women. Unfortunately, most women treated with TAM eventually develop resistant tumor recurrences which require intervention with a second-line endocrine therapy, or cytotoxic chemotherapy if the recurrence is completely endocrine insensitive. There is evidence that some recurrences may in fact be TAM stimulated. MCF-7 human breast cancer cells grown as solid tumors in athymic mice chronically treated with TAM reproducibly develop a TAM stimulated phenotype (Osborneet al., Eur J Cancer Clin Oncol 23: 1189-1196, 1987; Gottardis and Jordan, Cancer Res 48: 5183-5187, 1988; Osborneet al., J Natl Cancer Inst 83: 1477-1482, 1991; Wolfet al., J Natl Cancer Inst 85: 806-812, 1993). Tumors of this type may provide a useful model for a subset of therapeutic failures in the clinic. Therefore, we have extensively studied this model in an attempt to define the mechanism or mechanisms leading to TAM stimulated growth. In this paper we describe the characteristics of 4 TAM stimulated MCF-7 tumor variants. All of these tumors are growth stimulated by TAM, but vary in their response to estradiol (E₂) treatment, and grow poorly in placebo treated hosts. All tumor variants express estrogen receptor (ER) RNA and protein, which at the RNA level appear to be down regulated by TAM, and to a greater extent by E₂. All tumors also express epidermal growth factor receptor (EGFR) RNA, which is down regulated by TAM, and further down regulated by E₂. However, among the tumor variants analyzed, ER and EGFR levels appear to be inversely related. Further, despite the expression of ER by all 4 TAM stimulated tumor variants, E₂ induction of progesterone receptor expression is very weak or entirely absent.     

雌、孕激素受体在托瑞米芬逆转MCF7/ADR细胞耐药中的作用

目的：研究托瑞米芬（toremifene，TOR）对MCF7／ADR细胞耐药的逆转作用及雌孕激素受体可能在其中发挥的作用。方法：采用SRB法测定TOR的耐药逆转倍数；流式细胞仪测定加入TOR后耐药细胞内Rhodamine 123荧光含量表达变化；Western blot检测TOR对P-gP表达的影响；免疫组化测定TOR对细胞雌孕激素受体表达情况的影响。结果：5、10、20moL／L的TOR对MCF7／ADR耐药的逆转倍数分别为1．5、7．0、35．4倍，而对MCF7／S细胞没有显著性作用。加入TOR后，MCF7／ADR细胞内ADR荧光的呈现由核外进入核内，荧光含量显著提高，接近于敏感细胞。MCF7／S细胞中P-gp表达阴性，而MCF／ADR细胞中P-gp表达阳性。5、10、20mol／L TOR对MCF7／ADR细胞中P-gp表达未产生显著性抑制作用。MCF7／S细胞的雌激素受体表达阳性，孕激素受体表达弱阳性。MCF7／ADR细胞的雌、孕激素受体表达均阴性。10mol／L TOR对MCF7／S、MCF7／ADR细胞的雌、孕激素受体表达没有影响。结论：TOR可显著逆转MCF7／ADR细胞对ADR的耐药性。其逆转作用与雌、孕激素受体表达情况无明显关系，可能是通过抑制P-gp药泵功能来实现的。