Epidermal growth factor induces G protein-coupled receptor 30 expression in estrogen receptor-negative breast cancer cells

Different cellular receptors mediate the biological effects induced by estrogens. In addition to the classical nuclear estrogen receptors (ERs)-alpha and -beta, estrogen also signals through the seven-transmembrane G-protein-coupled receptor (GPR)-30. Using as a model system SkBr3 and BT20 breast cancer cells lacking the classical ER, the regulation of GPR30 expression by 17beta-estradiol, the selective GPR30 ligand G-1, IGF-I, and epidermal growth factor (EGF) was evaluated. Transient transfections with an expression plasmid encoding a short 5'-flanking sequence of the GPR30 gene revealed that an activator protein-1 site located within this region is required for the activating potential exhibited only by EGF. Accordingly, EGF up-regulated GPR30 protein levels, which accumulated predominantly in the intracellular compartment. The stimulatory role elicited by EGF on GPR30 expression was triggered through rapid ERK phosphorylation and c-fos induction, which was strongly recruited to the activator protein-1 site found in the short 5'-flanking sequence of the GPR30 gene. Of note, EGF activating the EGF receptor-MAPK transduction pathway stimulated a regulatory loop that subsequently engaged estrogen through GPR30 to boost the proliferation of SkBr3 and BT20 breast tumor cells. The up-regulation of GPR30 by ligand-activated EGF receptor-MAPK signaling provides new insight into the well-known estrogen and EGF cross talk, which, as largely reported, contributes to breast cancer progression. On the basis of our results, the action of EGF may include the up-regulation of GPR30 in facilitating a stimulatory role of estrogen, even in ER-negative breast tumor cells.     

Chemotherapy treatment and survival in older women with estrogen receptor-negative metastatic breast cancer: a population-based analysis

To investigate the survival benefit associated with chemotherapy receipt in older women with estrogen receptor–negative (ER–) Stage IV breast cancer. DESIGN: Observational, retrospective cohort study using Cox proportional hazards regression to determine effect of chemotherapy on hazard of all‐cause mortality. The two samples were an overall sample (n=1,519) and a propensity score–matched sample (n=580) to control for selection to treatment receipt. Hazard ratios (HRs) and 95% confidence intervals (CIs) were obtained for regression models. SETTING: U.S. women within the National Cancer Institute Surveillance, Epidemiology and End Results cancer registries (SEER) linked to Medicare enrollment and claims database. PARTICIPANTS: Female Medicare beneficiaries aged 66 and older with Stage IV ER– breast cancer diagnosed between 1999 and 2005. MEASUREMENTS: Outcome measure was all‐cause death during the follow‐up period. Survival was measured as time from breast cancer diagnosis until death or last follow‐up date. Information on receipt of chemotherapy, defined as chemotherapy received within 6 months after diagnosis, was obtained from linked Medicare claims. RESULTS: One thousand five hundred nineteen ER– women diagnosed with metastatic breast cancer were identified; 494 (33%) received chemotherapy. Chemotherapy was associated with a statistically significant survival benefit (HR=0.61, 95% CI=0.54–0.70). Age did not modify the survival benefit of chemotherapy. CONCLUSION: Chemotherapy received within 6 months after diagnosis was associated with a 39% lower hazard of death within the time period for the study. These findings reflect chemotherapy use outside of the clinical trial setting and have important clinical and policy implications for the study of treatments in older women with advanced ER– breast cancer.     

ARK5 is associated with the invasive and metastatic potential of human breast cancer cells

Purpose  

To investigate the effects of Akt/ARK5 pathways on the metastatic potential of human breast cancer cells.     

Cbl-b shRNA稳定转染乳腺癌MDA-MB-231细胞系的构建

目的构建靶向Cbl-b基因的短发夹环RNA（shRNA）真核质粒表达载体,建立Cbl-b shRNA稳定转染人乳腺癌MDA-MB-231细胞系,为探讨Cbl-b的生物学功能奠定基础。方法设计Cbl-b shRNA序列BLAST进行同源性分析。化学合成法合成shRNA序列,将配对的单链合成双链,以T4连接酶连接于pSilencerTM 4.1-CMV表达载体,加入感受态细胞。将菌液涂布于含有氨苄青霉素的LB平板,筛选阳性菌落,测序确认后进行大量复制、扩增,提取重组质粒。脂质体法将上述质粒转染至MDA-MB-231细胞中,G418持续压力选择和有限稀释法获得稳定转染的细胞系。结果 DNA测序证实靶向Cbl-b基因的shRNA真核质粒表达载体构建正确,G418压力筛选出阳性克隆,Western blot检测发现MDA-MB-231/Cbl-b shRNA转染细胞株中Cbl-b蛋白表达水平明显下调。结论成功构建了基因沉默Cbl-b的MDA-MB-231细胞株,为进一步探讨其生物学功能奠定实验基础。     

Calmodulin, a regulatory partner of the estrogen receptor alpha in breast cancer cells

Although calmodulin (CaM) interaction with estrogen receptor alpha (ERalpha) has been known for more than two decades, it is only recently that the molecular mechanism of CaM-mediated regulation of ERalpha is beginning to emerge. Others and we have identified a putative calmodulin binding site (P(295)LMIKRSKKNSLALSTADQMVS(317)) in ERalpha, at the boundary between the hinge and the ligand binding domain. ERalpha mutations affecting its association with CaM have been reported to generate high basal, estrogen-independent transactivation activity, indicating that the P(295)-T(317) sequence has an inhibitory function. Moreover, we found that a synthetic peptide (ERalpha17p: P(295)-T(311)) containing residues crucial for CaM binding exerts estrogenic effects on breast carcinoma cells. Finally, computer-aided conformational studies revealed that the CaM binding site might associate with a region located downstream in ERalpha (the beta turn/H4 region), this association likely resulting in an auto-inhibitory folding of the receptor. Thus, we propose as a hypothesis that CaM acts as a positive regulator by relieving this ERalpha auto-inhibition.     

Unopposed estrogen therapy and the risk of invasive breast cancer

BACKGROUND: Although short-term unopposed estrogen use does not seem to increase breast cancer risk, the effect of longer-term estrogen use remains unclear. We sought to assess the relationship between longer-term use of unopposed estrogen and the risk of invasive breast cancer over an extended follow-up period. METHODS: Within the Nurses' Health Study, a prospective cohort study, we observed 11 508 postmenopausal women who had a hysterectomy and reported information on estrogen use at baseline (1980). The study population was expanded every 2 years to include women who subsequently became postmenopausal and had a hysterectomy, so that 28 835 women were included in the final follow-up period (2000-2002). Estrogen use was assessed from self-reported data on biennial questionnaires. The main outcome was invasive breast cancer. RESULTS: A total of 934 invasive breast cancers were included in the analysis. Breast cancer risk increased with duration of unopposed estrogen use among longer-term users with the highest risk seen in cancers positive for estrogen receptor (ER+) and progesterone receptor (PR+). The multivariate relative risks (RRs) and 95% confidence intervals (CIs) for breast cancer with current use of unopposed estrogen for less than 5 years, 5 to 9.9 years, 10 to 14.9 years, 15 to 19.9 years, and 20 years or longer were, respectively, 0.96 (95% CI, 0.75-1.22), 0.90 (95% CI, 0.73-1.12), 1.06 (95% CI, 0.87-1.30), 1.18 (95% CI, 0.95-1.48), and 1.42 (95% CI, 1.13-1.77) (P for trend <.001). The risk of ER+/PR+ breast cancers was noted to be statistically significant after 15 years of current use (RR, 1.48; 95% CI, 1.05-2.07). CONCLUSION: Users of unopposed estrogen were at increased risk of breast cancer but only after longer-term use.     

Activated estrogen receptor mediates growth arrest and differentiation of a neuroblastoma cell line.

Several reports demonstrate estrogen receptor involvement in specific brain functions. In addition, estrogen receptors are expressed at early stages of brain development, suggesting that estrogens or related molecules may play an instructive role in the differentiation of specific brain areas. The lack of model systems in which these phenomena could be studied prompted us to develop a neuroblastoma cell line expressing the estrogen receptor. The cell line expresses the hormone receptor at levels compatible with a physiological activity. The activated estrogen receptor is capable of blocking proliferation of the cells without exerting toxic effects. Following growth arrest, the cells display a neuron-like morphology and express tau and synaptophysin, two proteins synthesized in differentiating neurons. The cell line generated will provide a valuable model system for molecular and biochemical studies of the activity of estrogens in neural-derived cells.     

Enhanced expression of trophinin promotes invasive and metastatic potential of human gallbladder cancer cells

Purpose  To study effects of trophinin on the metastatic potential of human gallbladder cancer cells and its potential mechanism. Materials and methods  Expression of trophinin in the highly metastatic GBC-SDH_i cells was investigated by real time RT-PCR and western blot. Recombinant expression plasmid vector of the human trophinin gene was constructed and transfected into GBC-SD cells. Effects of trophinin on the invasion of GBC-SD cells were investigated by adhesion assay and invasion assay in vitro. The siRNA was used to down-regulate the expression of trophinin. Some genes related to the invasion and metastasis of cancer were determined by real time RT-PCR and western blot. The pulmonary metastasis regulated by trophinin was determined in the nude mice. Results  Overexpression of trophinin in GBC-SDH_i cells was confirmed compared with its parental counterparts. Up-regulation of trophinin enhanced the in vitro invasion in the GBC-SD/TRO cells. The enhancement was associated with increasing integrin α3, MMP-7, MMP-9, and Ets-1 expression. The results were further demonstrated by RNA interference experiment in vitro. In in vivo study, we also demonstrated that trophinin-transfected gallbladder cancer cells had more pulmonary metastases than the vector-transfected one or its parental counterparts. Conclusion  Overexpression of trophinin leads to a more invasive phenotype and metastatic potential in human gallbladder cancer, at least in part, through regulating integrin α3, MMP-7, MMP-9, and Ets-1 expression. X.-Z. Chang, J. Yu and X.-H. Zhang have contributed equally to this work.     

Estrogen-dependent rapid activation of protein kinase C in estrogen receptor-positive MCF-7 breast cancer cells and estrogen receptor-negative HCC38 cells is membrane-mediated and inhibited by tamoxifen

We examined protein kinase C (PKC) in the regulation of breast cancer cells by estrogen. Estrogen receptor (ER)- positive (+) MCF-7 and ER-negative (-) HCC38 cells were treated with 17 beta-estradiol (E(2)) or E(2)-BSA, which cannot enter the cell. E(2) and E(2)-BSA rapidly increased PKC-alpha in both cells via phosphatidylinositol-dependent phospholipase C and G protein, but not phospholipase A(2) or arachidonic acid. In MCF-7 cells, E(2) and E(2)-BSA had comparable effects, maximal at 90 min. In HCC38 cells, PKC was maximal at 9 min, with E(2)-BSA more than E(2). Tamoxifen blocked estrogen-dependent PKC in MCF-7 cells and reduced it in HCC38 cells. ER-antagonist ICI 182780, ER-agonist diethylstilbestrol, and antibodies to ER alpha and ER beta had no effect. E(2) stimulated [(3)H]thymidine incorporation in MCF-7 only; E(2)-BSA had no effect. Tamoxifen did not alter E(2)-dependent increases in MCF-7 cells, whereas ICI 182780 reduced DNA synthesis in control and E(2)-treated cultures. PKC activity was positively correlated with tumor severity in 133 breast cancer specimens and was greater in ER(-) tumors. Tamoxifen treatment reduced recurrence, and recurrent tumors had higher PKC activity. This indicates that E(2) rapidly increases PKC activity via membrane pathways not involving ER alpha or ER beta and suggests that tamoxifen works by reducing PKC activity through non-ER alpha/ER beta-dependent mechanisms.     

Clinical relevance of estrogen receptor variants in breast cancer.

It is well accepted that the presence of estrogen receptor (ER) in breast cancer patients correlates with a better prognosis and a higher probability of response to hormonal treatment. Recent data suggest the ER variant isoforms may be common in clinical breast cancer. Furthermore, an association between the expression of such variants and the development of antihormone resistance is discussed. Although several functionally different ER variants have been described, their significance in the prognosis and treatment of breast cancer is still hypothetical.     

Activation of estrogen receptor alpha increases and estrogen receptor beta decreases apolipoprotein E expression in hippocampus in vitro and in vivo

Previous evidence indicates that, in carriers of apolipoprotein E4 (ApoE4), estrogen therapy increased the risk of late-onset Alzheimer's disease (AD), whereas in individuals carrying ApoE2/3, estrogen therapy reduced the risk of AD [Cauley JA, Zmuda JM, Yaffe K, Kuller LH, Ferrell RE, Wisniewski SR, Cummings SR (1999) J Bone Miner Res 14:1175-1181; Yaffe K, Haan M, Byers A, Tangen C, Kuller L (2000) Neurology 54:1949-1954]. Estrogen mechanisms of action are mediated by two estrogen receptors (ERs), ERalpha and ERbeta. In this study, we determined the relationship between ER subtype and estrogen regulation of ApoE expression in HT-22 cells ectopically transfected with ERalpha or ERbeta, in primary cultured rat hippocampal neurons in vitro and in rat hippocampus in vivo by both molecular biological and pharmacological analyses. Results of these analyses demonstrated that activation of ERalpha either by 17beta-estradiol or a specific-agonist, propylpyrazole triol, up-regulated ApoE mRNA and protein expression. In contrast, the ERbeta-selective agonist, diarylpropionitrile, down-regulated ApoE mRNA and protein expression. These results demonstrate that, in vitro and in vivo, ApoE expression can be differentially regulated depending on activation of ER subtypes. These data suggest that use of ER-selective ligands could provide therapeutic benefit to reduce the risk of AD by increasing ApoE expression in ApoE2/3 allele carriers and decreasing ApoE expression in ApoE4 allele carriers.     

Chronic diarrhea--an unusual presentation of metastatic invasive lobular cancer of breast.

We report a 56-year-old lady with chronic diarrhea and weight loss. She had undergone lumpectomy with axillary clearance (node positive) four years ago for invasive lobular carcinoma of breast. Investigations revealed involvement of almost the entire gut with skip areas. Biopsies from the stomach showed presence of signet-ring cells, suggestive of metastases from invasive lobular carcinoma of breast. Estrogen receptor immuno-staining was positive, confirming the diagnosis. She was treated initially with octreotide and later with chemotherapeutic agents, with transient relief in diarrhea. She succumbed eight months later.     

氧化苦参碱对人胰腺癌细胞株SW1990侵袭转移能力的影响

目的 探讨氧化苦参碱对人胰腺癌细胞株SW1990体外迁移及侵袭能力的影响及其作用机制.方法 体外培养人胰腺癌SW1990细胞株,用氧化苦参碱处理SW1990细胞后,采用MTT法检测细胞增殖;通过细胞黏附实验、细胞划痕实验及Transwell小室检测细胞的黏附、迁移及侵袭能力;RT-PCR法检测细胞基质金属蛋白酶2(MMP-2)、血管内皮生长因子(VEGF)mRNA的表达;ELISA法检测细胞VEGF蛋白的含量.结果 氧化苦参碱呈剂量和时间依赖性抑制SW1990细胞的增殖.2 mg/ml氧化苦参碱处理SW1990细胞1 h后,细胞的体外黏附抑制率为(35.23 ±8.56)%;处理24 h后,细胞的过河时间为(65.46±4.25)h,较对照组的(34.50±4.12)h显著延长(P<0.05);穿膜细胞数为(91.9±9.6)个,较对照组的(144.2±17.2)个显著减少(P<0.05);细胞VEGF、MMP-2 mRNA的表达及VEGF蛋白的分泌量均显著下调[0.515 ±0.063比0.817±0.054,0.343±0.072比0.650±0.068,(265.50 ±5.45)pg/ml比(441.06±16.70)pg/ml,P值均<0.05].结论 氧化苦参碱可能通过抑制MMP-2和VEGF表达进而抑制胰腺癌SW1990细胞的增殖、黏附、迁移及侵袭能力.     

The use of selective estrogen receptor modulators and selective estrogen receptor down-regulators in breast cancer

Tamoxifen is one of the most effective treatments for breast cancer through its ability to antagonize estrogen-dependent growth by binding estrogen receptors (ERs) and inhibiting proliferation of breast epithelial cells. However, tamoxifen has estrogenic agonist effects in other tissues such as bone and endometrium due to liganded ER activating target genes in these different types of cell. Several novel anti-estrogen compounds have been developed which have a reduced agonist profile on breast and gynaecological tissues. These compounds offer the potential for enhanced efficacy and reduced toxicity compared with tamoxifen. In advanced breast cancer clinical data exist for two groups of agents: the selective estrogen receptor modulators (SERMs), further divided into "tamoxifen-like" (e.g. toremifene, droloxifene and idoxifene) and "fixed ring" compounds (e.g. raloxifene, arzoxifene and EM-800), and the selective estrogen receptor down-regulators (SERDs; e.g. fulvestrant (ICI 182780), SR 16234 and ZK 191703) also termed "pure anti-estrogens". In phase II trials in tamoxifen-resistant metastatic breast cancer the SERMs show low objective response rates (range 0-15%), suggesting cross resistance with tamoxifen. Randomized phase III trials for toremifene and idoxifene in over 1500 patients showed no significant difference compared with tamoxifen. Fewer clinical data exist for the "fixed ring" SERMs and it remains unclear whether any clinical advantage exists for the "fixed ring" SERMs over tamoxifen as first-line therapy. The main advantage for SERMs such as tamoxifen and raloxifene probably remains in early-stage disease (adjuvant therapy or prevention).Fulvestrant and the other SERDs have a high affinity for the estrogen receptor (ER) compared to tamoxifen, but none of its agonist activities. Of the SERDs, only fulvestrant has entered the clinic and this new agent is showing promising clinical activity in the treatment of advanced breast cancer. Recently published phase III studies have shown fulvestrant to be at least as effective as the third-generation aromatase inhibitor anastrozole in patients whose disease has relapsed or progressed on prior endocrine therapy. Surprisingly, however, in a phase III trial versus tamoxifen for the first-line therapy of advanced breast cancer fulvestrant did not attain the requirements for equivalence to tamoxifen, and in terms of time-to-treatment failure was inferior (5.9 versus 7.8 months for fulvestrant and tamoxifen, respectively; P=0.029). Future clinical studies will evaluate fulvestrant in the neoadjuvant setting together with its optimal sequencing in relation to tamoxifen and other endocrine therapies in advanced disease.