Antiestrogen, trans-tamoxifen modulation of human breast cancer cell growth

To gain further insight into how estrogens modulate cell function, the effects of estrogen on cell proliferation were studied in human breast cancer cells. We examined the effects of estrogen on the proliferation of three human breast cancer cell lines that differed in their estrogen receptor contents. Ten nM estradiol markedly stimulated the proliferation of MCF-7 human breast cancer cells that contained high levels of estrogen receptor (1.15±0.03 pmole/mg protein) over that of control. In T47D cells that contained low levels of estrogen receptor (0.23±0.05 pmole/mg protein), Ten nM estrogen slightly stimulated the proliferation over that of control. MDA-MB-231 cells, that contained no detectable levels of estrogen receptors, had their growth unaffected by estrogen. These results showed their sensitivity to growth stimulation by estrogen correlated well with their estrogen receptor content. Also we examined the effect of estrogen on cellular progesterone receptor level as well as plasminogen activator activity in MCF-7 cells. Ten nM estradiol showed maximal stimulation of progesterone receptor level as well as plasminogen activator activity in MCF-7 cells. It is not clear whether these stimulations of progesterone receptor and plasminogen activator activity by estrogen are related to the estrogen stimulation of cell proliferation of MCF-7 cells. Studies with estrogen in human breast cancer cells in culture indicate that sensitivity to growth stimulation by estrogen correlates well with estrogen receptor contents.     

Sulforaphane halts breast cancer cell growth

Sulforaphane is a chemical found in cruciferous vegetables such as broccoli, sprouts and kale. This compound is a potent inducer of protective enzymes that provide defense against cancer-causing chemicals. Researchers have discovered that sulforaphane can halt human breast cancer cells in their tracks and have identified a new mechanism of action for the compound.     

Estrogen priming in advanced breast cancer

The successful treatment of advanced breast cancer has reached a plateau in recent years. Estrogen priming is a new combination therapy involving estrogens, antiestrogens, and chemotherapy that may result in the improvement of treatment responses. This investigational therapy is designed to synchronize cell cycles with estrogens and antiestrogens in order to enhance the activity of cell cycle-specific anticancer drugs. The pharmacological manipulation of cell growth coupled with appropriate antineoplastic agents could result in a new treatment approach for advanced breast cancer. The rationale and current status of estrogen priming are reviewed.     

雌激素受体β与乳腺癌

乳腺癌是工业化国家女性中最常见的癌症,为排名在肺癌之后的第二大杀手[1].雌激素(estrogen)对于维持正常乳腺组织的发育和功能至关重要,其分泌紊乱可导致某些乳腺癌细胞的恶性增殖.雌激素受体α(estrogen receptorα,ERα)于1986年被克隆后,人们对其分子结构、生理功能和在乳腺癌发生发展过程中的作用进行了深入的研究,以其为靶点的药物也在临床实践中得到了广泛的应用[1,2].1996年又相继从大鼠[3]、人类[4]和小鼠[5]中发现ERβ,从而为进一步揭示包括乳腺癌在内的多种妇女疾病的发病机制开拓了崭新的视野.     

Effect of triphenylacrylonitrile derivatives on estradiol-receptor binding and on human breast cancer cell growth

In a study of a series of 26 triphenylacrylonitrile derivatives (TPEs), we investigated the influence of several possibly interrelated factors on the proliferation of human breast cancer cell lines. (1) Chemical substituents: the test compounds were for the most part para-hydroxylated with increasingly bulky hydrophobic and/or basic side chains [isopropyloxy or (diethylamino)ethoxy] or standard reference compounds. (2) Relative binding affinities (RBAs): they competed diversely for [3H]estradiol (E2) binding to calf uterus cytosol and little, if at all, for binding to the [3H]tamoxifen-labeled antiestrogen binding site (AEBS) in lower speed supernatant. A multiparametric comparison of RBAs recorded for calf, rat, and mouse uterus cytosol estrogen receptor (ER) revealed a possible influence of species-specific receptor conformation and/or environment on binding. (3) Estrogen/antiestrogen potency: their stimulation and inhibition of the proliferation of the ER-positive human breast cancer cell line (MCF7) was measured. Compounds with only hydroxy substituents stimulated proliferation more markedly than methylated derivatives and had a maximum effect at 10(-11)-10(-6) M. Stimulation was related to the RBA for ER. Compounds with isopropyloxy or (diethylamino)ethoxy side chains only weakly stimulated MCF7 cell growth and more powerfully antagonized E2-promoted growth. The extent of inhibition depended upon the bulk of the side chain and could be reversed by 10(-7) M E2. Within the same concentration ranges, the test compounds were without effect on the BT20 ER-negative cell line. (4) Cytostatic and/or cytolytic activity: most compounds could arrest the proliferation of both MCF7 and BT20 cells at concentrations above 3 x 10(-6) M. This activity was thus independent of ER. Nevertheless, those compounds with a charged hydrophobic side chain, which were the most powerful antagonists of E2-promoted cell growth, were also the most cytotoxic. The overall results for all molecules on all parameters were submitted to a multivariate analysis (correspondence analysis) which revealed the progressive influence of increasing substitution by hydroxy and more bulky groups on the generation of antagonist activity and cytotoxicity.     

Estrogen modulation: Tiered testing for human hazard evaluation

Recent concerns about the potential of certain chemicals to modulate estrogen-regulated processes have led to questions as to how chemicals should be tested for such effects. Therefore, AIHC has developed a comprehensive, resource-efficient, and flexible tiered strategy for estrogen modulation (EM) testing. Levels of evaluation include Tier 0, in which exposure, along with alerts based on structure-activity, persistence, bioaccumulation, and other data, are assessed to prioritize chemicals for preliminary testing. In Tier I, short term in vitro, ex vivo, and/or in vivo assays are used to obtain a preliminary indication of EM potential. Among these, an in vivo response assay is considered the most reliable at this time. However, none of these tests are intended for risk assessment, but rather to aid in choosing chemicals for further testing and in guiding the extent of that testing. Tier II is aimed at risk assessment and involves whole animal tests that contain EM-sensitive end points (e.g., two-generation reproduction study). Tier III consists of hypothesis-driven research reserved for situations where targeted research can reduce levels of uncertainty. This tiered approach provides a framework for the strategic and effective application of EM test methods to address specific information needs on a case by case basis.     

Effects of vinorelbine on epidermal growth factor-receptor binding of human breast cancer cell linesin vitro

Epidermal Growth Factor (EGF) is a mitogenic peptide that binds to surface membrane receptors (EGFR) of breast cancer cells. After binding, secondary transmitter molecules are activated by tyrosine phosphorylation of the intracellular receptor domaine. The activity of the EGF/EGFR system can be modulated by a variety of chemically unrelated compounds including cytostatic agents. The purpose of our present study was to determine the effects of vinorelbine, a novel semisynthetic vinca alkaloid on EGF receptor binding on human breast cancer cells. We have found that MDA-231 and MDA-468 cells bind substantially more [¹²⁵I]-EGF after preincubation with vinorelbine. This effect was concentration- and time-dependent reaching a maximum at 100 ng/ml and 24 h incubation. Subsequent experiments showed an increase in the rate of EGF binding as well as maximal binding capacity. Scatchard analysis of binding experiments under equilibrium conditions indicated that this was mainly due to an increase in the number of apparent EGF binding sites. Modulation of EGF receptor binding by vinorelbine was not detectable when isolated membranes were used indicating that intact cytoplasmatic mechanisms are required for the upregulation of EGF receptors.     

胰岛素对人乳腺癌细胞株MDA-MB-543生长的增殖作用

目的探讨胰岛素对人乳腺癌细胞株MDA-MB-543生长的增殖作用。方法将胰岛素直接作用于体外培养的人乳腺癌细胞株(MDA-MB-543),采用四甲基偶氮唑盐(MTT)法检测细胞增殖,流式细胞仪测定细胞周期分布。结果胰岛素在1～10 mU/mL浓度范围内和作用时间2～16 h范围内,对MDA-MB-543增殖作用逐步增强,反映增殖活性的S期和G2/M期细胞比例逐渐增多,其中S期细胞比例与对照组比较有显著性差异(均P<0.05或0.01)。结论胰岛素能加快诱导MDA-MB-543细胞进入细胞周期S期增殖,呈剂量和时间依赖关系,但是短暂和可逆的。     

Estrogen receptors as therapeutic targets in breast cancer

The estrogen receptor alpha (ERalpha) has proven to be the single most important target in breast cancer over the last 30 years. The use of the selective ER modulator (SERM) tamoxifen for the treatment and prevention of breast cancer has changed therapeutics. The SERM raloxifene, approved for the treatment of osteoporosis, lacks tamoxifen's increased risk for endometrial cancer and is being evaluated for the prevention of breast cancer. Other SERMs approved or under development for use against breast cancer or osteoporosis include toremifene, GW5638, GW7604 (the active metabolite of GW5638), idoxifene, lasofoxifene, arzoxifene, bazedoxifene, EM-800 and acolbifene (the active metabolite of EM-800). Aromatase inhibitors (AIs) have recently proven to be more efficacious than tamoxifen as first-line therapy, efficacious for second-line therapy (e.g. against tamoxifen-resistant disease), and useful for extended adjuvant therapy after tamoxifen. The AIs include the non-steroidal agents letrozole and anastrole, and the steroidal agent exemestane. The pure antiestrogen fulvestrant has proven to be just as effective as AIs. Other pure antiestrogens, ZK-703, ZK-253, RU 58668 and TAS-108 show great promise. The development of resistance to endocrine therapy remains a clinically important problem, and laboratory models based on human breast cancer cells grown as tumors in immune-compromised mice have led to important insights into this problem. Progesterone receptor-negative status of ER-positive breast cancers may reflect altered growth factor receptor signaling, and helps to explain why this subclass of tumors exhibits lower response rates to tamoxifen compared to cancers typed progesterone receptor-positive. Crosstalk among plasma membrane-localized ER, growth factor receptor signaling, and nuclear-localized ER provide further insights into antihormonal-resistant breast cancer.     

Frondoside A inhibits human breast cancer cell survival, migration, invasion and the growth of breast tumor xenografts

Breast cancer is a major challenge for pharmacologists to develop new drugs to improve the survival of cancer patients. Frondoside A is a triterpenoid glycoside isolated from the sea cucumber, Cucumaria frondosa. It has been demonstrated that Frondoside A inhibited the growth of pancreatic cancer cells in vitro and in vivo. We investigated the impact of Frondoside A on human breast cancer cell survival, migration and invasion in vitro, and on tumor growth in nude mice, using the human estrogen receptor-negative breast cancer cell line MDA-MB-231. The non-tumorigenic MCF10-A cell line derived from normal human mammary epithelium was used as control. Frondoside A (0.01-5 μM) decreased the viability of breast cancer cells in a concentration- and time-dependent manner, with 50%-effective concentration (EC50) of 2.5 μM at 24h. MCF10-A cells were more resistant to the cytotoxic effect of Frondoside A (EC50 superior to 5 μM at 24 h). In the MDA-MB-231 cells, Frondoside A effectively increased the sub-G1 (apoptotic) cell fraction through the activation of p53, and subsequently the caspases 9 and 3/7 cell death pathways. In addition, Frondoside A induced a concentration-dependent inhibition of MDA-MB-231 cell migration and invasion. In vivo, Frondoside A (100 μg/kg/dayi.p. for 24 days) strongly decreased the growth of MDA-MB-231 tumor xenografts in athymic mice, without manifest toxic side-effects. Moreover, we found that Frondoside A could enhance the killing of breast cancer cells induced by the chemotherapeutic agent paclitaxel. These findings identify Frondoside A as a promising novel therapeutic agent for breast cancer.     

Novel piperidinedione analogs as inhibitors of breast cancer cell growth

We previously reported the utility of antineoplaston-A10 (3-phenylacetylamino-2,6-piperidinedione) as an endogenous cancer protector and immune modulator in breast cancer patients (Cancer Lett., 2000, 157, 57). In this study, four new piperidinedione A10 analogs were synthesized and tested for their antimitotic activity on a human breast cancer cell line against the prototype A10 and the antibreast cancer drug tamoxifen. Moreover, the DNA binding capacity of such compounds was evaluated against A10, (E)-3-(4-Nitrocinnamoylamino)-2,6-piperidinedione "3B" and (E)-3-(4-hydroxycinnamoylamino)-2,6-piperidinedione "3D" were several-fold more potent antiproliferative agents than A10 and tamoxifen. They also had significantly higher capacity to bind DNA than A10. Conversely, (E)-3-(cinnamoylamino)-2,6-piperidinedione "3A" and (E)-3-(4-methoxycinnamoylamino)-2,6-piperidinedione) "3C" had weaker biological profiles than the lead compound A10. Detailed synthetic, spectroscopic, and biological data are reported.     

Inhibitory effect of substituted dextrans on MCF7 human breast cancer cell growth in vitro.

Substituted dextrans can reproduce some of the properties of heparin and can thus be used to alter cellular growth. We studied the effect of heparin (H108), dextran (D), carboxymethylbenzylamide dextran (CMDB) and carboxymethylbenzylamide sulfonate dextran (CMDBS) on the growth of human mammary cells of the MCF7 tumor line. The cells were cultured in minimum Eagle's medium containing 2% fetal calf serum without biopolymer, or with increasing concentrations of H108, D, CMDB or CMDBS. Growth curves were accurately based on cell counting using a Coulter counter. Cell distribution in the various phases of the cycle was analyzed by flow cytometry. Dose-dependent growth inhibitory effects (400-4000 micrograms/ml) were observed. The effect on MCF7 tumor cells was most apparent with CMDBS. The percentage of cells in the S phase decreased with preferential blocking in the G0/G1 phase. Pre-clinical studies can be anticipated as there is an absence of in vivo toxicity.     

The modulation of PD-L1 induced by the oncogenic HBXIP for breast cancer growth

Programmed death ligand-1(PD-L1)/PD-1 checkpoint extensively serves as a central mediator of immunosuppression.A tumor-promoting role for abundant PD-L1 in seve...     

Estrogen receptor enhances the antiproliferative effects of trichostatin A and HC-toxin in human breast cancer cells

Trichostatin A, an antifungal antibiotics, and HC-toxin are potent and specific inhibitors of histone deacetylase activity. Histone deacetylase inhibitors are new class of chemotherapeutic drugs able to induce tumor cell apoptosis and/ or cell cycle arrest. In this study, the antiproliferative activities of trichostatin A and HC-toxin were compared between estrogen receptor positive human breast cancer cell MCF-7 and estrogen receptor negative human breast cancer cell MDA-MB-468. Trichostatin A and HC-toxin showed potent antiproliferative activity in both MCF-7 and MDA-MB-468 cells. In MCF-7 cells that contain high level estrogen receptor, trichostatin A and HC-toxin brought about three-times more potent cell growth inhibitory effect than estrogen receptor negative MDA-MB-468 cells. Both trichostatin A and HC-toxin showed cell cycle arrest at G₂/M phases of MCF-7 and MDA-MB-468 cells in a dose- and time- dependent manner. Trichostatin A and HC-toxin also induced apoptosis from MCF-7 and MDA-MB-468 cells in a dose- and time-dependent manner. Results of this study suggested that antiproliferative effects of trichostatin A and HC-toxin might be involved in estrogen receptor signaling pathway, but cell cycle arrest and apoptosis of trichostatin A and HC-toxin might not be involved in estrogen receptor system of human breast cancer cells.     

Caveolin involvement and modulation in breast cancer

Caveolae are highly enriched in numerous membrane-bound proteins and caveolin-1 is their major component. Caveolae and caveolin proteins are involved in a variety of cellular processes including lipid homeostasis, endocytosis, signal transduction, and tumorigenesis. Breast cancer is one of the most common cancers in women throughout the world. Clinical studies have shown that the correlation of caveolin-1 expression with tumor progression varies with tumor type. The data presented here extend the findings that caveolin-1 suppresses breast cancer but there are controversial studies. The potential function of caveolin-1 in scaffolding signaling factors also demonstrates the importance of its expression control and modulation, correlating with physiological or pathological conditions. Based on current research, this review presents the current understanding of their function and the involvement of caveolin-1 in breast cancer pathogenesis.     

川楝素对乳腺癌MDA-MB-231细胞增殖的抑制作用

目的 探讨川楝素对人三阴性乳腺癌MDA-MB-231细胞生长的抑制作用及其机制.方法 取对数生长期的MDA-MB-231细胞,采用0、6.25、12.50、25.00、50.00和100.00 nmol/L川楝素处理,绘制生长曲线.川楝素0、12.5和50 nmol/L处理72 h后,采用MTS法检测川楝素对MDA-MB-231细胞增殖,流式细胞仪检测乳腺癌细胞凋亡和周期,Western blot检测凋亡相关蛋白半胱氨酶蛋白酶3(Caspase-3)、聚腺苷酸二磷酸核糖转移酶(PARP)和cleave-PARP表达.结果 川楝素呈时间和剂量依赖性抑制MDA-MB-231乳腺癌细胞增殖(P＜0.01).川楝素作用48、72和96 h的半数抑制浓度(IG0)分别为9.32、16.96和122.37nmol/L.川楝素能呈浓度依赖性诱导乳腺癌细胞凋亡(P＜0.01),阻滞细胞在S期(P＜0.01).以0、12.50和50.00 nmol/L川楝素处理MDA-MB-231细胞72 h,其早期凋亡率分别为8.12％、20.85％和67.21％,处于细胞周期S期的细胞占32.69％、47.90％和61.23％,凋亡相关蛋白Caspase-3和PARP减少,cleaved-PARP增多.结论 川楝素对人乳腺癌MDA-MB-231细胞增殖具有抑制作用;其机制可能与诱导细胞凋亡和引起细胞S期阻滞有关.     

Cell type specific, receptor-mediated modulation of growth kinetics in human lung cancer cell lines by nicotine and tobacco-related nitrosamines

The objective of this study was to investigate a potential involvement of nicotinic cholinergic receptors in the mediation of cell type specific biological effects of nicotine and the two tobacco-related nitrosamines N-nitrosodiethylamine (DEN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) on human lung cells. Three well differentiated human lung cancer cell lines that have been reported previously to possess ultrastructural and biochemical features of normal pulmonary neuroendocrine cells, Clara cells and alveolar type II cells, respectively, were used for these experiments. The effects of nicotine, DEN, and NNK on cell proliferation and its modulation by established antagonists of nicotinic and muscarinic cholinergic receptors were studied. In the neuroendocrine cell line, nicotine and the two nitrosamines caused a strong stimulation of cell proliferation that was inhibited by antagonists of nicotinic cholinergic receptors. In the cell lines with features of Clara cells and alveolar type II cells, nicotine did not stimulate cell proliferation. Both nitrosamines stimulated cell proliferation in the cell line with Clara cell features. This effect was not changed by pre-exposure to cholinergic antagonists. The data suggest a selective uptake of nicotine and the two nitrosamines via nicotinic cholinergic receptors in pulmonary neuroendocrine cells.