柠檬苦素类化合物对人乳腺癌细胞(MCF-7)的生长抑制及细胞周期动力学的影响

为了探讨柠檬苦素类似物对乳腺癌细胞MCF-7生长抑制和对细胞周期的影响，应用MTT法和流式细胞仪检测癌细胞株生长和细胞周期.结果显示柠檬苦素类似物能明显抑制MCF-7的生长，抑制率高于70%，并随作用时间和剂量增加其效果增强；柠檬苦素可以影响细胞周期G     

Growth Factor Regulation of Cell Cycle Progression in Mammary Epithelial Cells

Growth factors are among the critical positive and negative regulators of cell proliferation for normal mammary/breast epithelial cells and for breast cancer cells. The mechanisms by which specific growth factors regulate the cell cycle in mammary/breast epithelial cells is beginning to be understood for several growth factor families, including the epidermal growth factor, insulin-like growth factor, and transforming growth factor-beta families. A critical issue for understanding how growth factors regulate the cell cycle in vivo is how individual factors interact with other growth factors or hormones to enhance or inhibit specific molecular targets in the cell cycle machinery. This review addresses what is currently known about how growth factors regulate the cell cycle in mammary/breast epithelial cells both individually and in coordination with other growth regulators.     

Notch signaling in mammary gland tumorigenesis

The Notch receptor protein and its signaling pathway have been well conserved throughout evolution and appear to be pivotal components in cell fate decisions during development. Recent studies suggest that, depending on the cellular and developmental context, Notch signaling may also affect cell proliferation and programmed cell death. Mammals have four related Notch genes. One of these, designated Notch-4, was found to be a common integration site for the mouse mammary tumor virus in mouse mammary tumors. One consequence of this type of viral integration event is the ectopic expression of the intracellular domain of Notch-4 that corresponds to a gain-of-function mutation. Expression of activated Notch-4 in mammary epithelium has profound effects on mammary gland development and tumorigenesis. In this review, we briefly summarize the structure and function of the Notch receptor, as well as the components that comprise and modify the signaling pathway. Finally we discuss the potential role of Notch in mammary gland development and tumorigenesis.     

Estrous Cycle Regulation of Mammary Epithelial Cell Proliferation, Differentiation, and Death in the Sprague-Dawley Rat: A Model for Investigating the Role of Estrous Cycling in Mammary Carcinogenesis

The Sprague-Dawley rat is highly regarded for studies designed to investigate the effects of endocrine modulation on mammary carcinogenesis. In this study, we further evaluate the validity of the Sprague-Dawley rat model for the study of human breast cancer by evaluating the effects of normal 4-day estrous cycling on mammary epithelial cell proliferation, differentiation, and apoptotic death. Trends in mammary gland development with stage of 4-day estrous cycle were evident. Mammary glands isolated from follicular and early luteal stages had predominantly ductal histoarchitecture, whereas glands isolated from mid-late luteal were predominantly lobuloalveolar. Quantitation of BrdU incorporation revealed that epithelial cell proliferation was eight-fold higher in metestrus and diestrus-1 than in proestrus. Expression of -casein and whey acidic protein (WAP)⁴ mRNA was also highly dependent on stage of estrous, with detection restricted to midcycle. Apoptotic cell death of mammary epithelium was found to be suppressed during the peak in cell proliferation. TRPM-2/clusterin mRNA was elevated when apoptosis was low and milk protein mRNA levels were high, consistent with putative roles for TRPM-2/clusterin in inhibiting cell death in regressing tissues and inducing mammary epithelial cell differentiation. Cell proliferation, differentiation, and death occurred only in a subset of epithelial cells per estrous cycle, and these cells appeared randomly distributed throughout multiple ductules and alveoli. These observations suggest that cellular response(s) to ovarian hormone-dependent signals is asynchronous. Cumulatively, these observations demonstrate that rat mammary epithelial cell proliferation, differentiation, and death are under the control of cycling ovarian hormones, similarly to the human mammary epithelium during the menstrual cycle.     

Use of Three-Dimensional Basement Membrane Cultures to Model Oncogene-Induced Changes in Mammary Epithelial Morphogenesis

The development of breast carcinomas involves a complex set of phenotypic alterations in breast epithelial cells and the surrounding microenvironment. While traditional transformation assays provide models for investigating certain aspects of the cellular processes associated with tumor initiation and progression, they do not model alterations in tissue architecture that are critically involved in tumor development. In this review, we provide examples of how three-dimensional (3D) cell culture models can be utilized to dissect the pathways involved in the development of mammary epithelial structures and to elucidate the mechanisms responsible for oncogene-induced phenotypic alterations in epithelial behavior and architecture. Many normal mammary epithelial cell lines undergo a stereotypic morphogenetic process when grown in the presence of exogenous matrix proteins. This 3D morphogenesis culminates in the formation of well-organized, polarized spheroids, and/or tubules that are highly reminiscent of normal glandular architecture. In contrast, transformed cell lines isolated from mammary tumors exhibit significant deviations from normal epithelial behavior in 3D culture. We describe the use of 3D models as a method for both reconstructing and deconstructing the cell biological and biochemical events involved in mammary neoplasia.These authors contributed equally to this review.     

Steroid Receptors and Cell Cycle in Normal Mammary Epithelium

The ovarian steroids estrogen and progesterone (E(2) and P) are essential for normal mammary gland growth and development; however, the mechanisms by which they influence the proliferative activity of the mammary epithelium remain unclear. Mammary epithelial cells cells expressing the receptors for E(2) and P (ER and PR respectively) are separate from, although often adjacent to, those capable of proliferating, implying that the ovarian steroids act indirectly via paracrine or juxtacrine growth factors to stimulate entry into the cell cycle. A large number of candidate factors have been identified in a variety of different experimental systems, and it appears that transforming growth factor beta may play a role in preventing proliferation of steroid receptor-containing cells. Dysregulation of the strict inverse relationship between ERalpha expression and proliferation is detectable in premalignant human breast lesions, indicating that it might be essential to the tumorigenic process. Challenges for the future include determining which of the candidates identified as being mediators of the effects of E(2) are physiologically and clinically relevant as well as finding out how ERalpha-containing cells become proliferative during tumorigenesis. Answering these questions could greatly increase our understanding of the factors controlling mammary gland development and the processes leading to cancer formation.     

An Atlas of Mouse Mammary Gland Development

The mouse mammary gland is a complex tissue, which is continually undergoing changes in structure and function. Embryonically, the gland begins with invasion of the underlying fat pad by a rudimentary ductal structure. Postnatal growth occurs in two phases: ductal growth and early alveolar development during estrous cycles, and cycles of proliferation, differentiation, and death that occur with each pregnancy, lactation, and involution. The variety of epithelial structures and stromal changes throughout the life of a mammary gland makes it a challenge to study. The purpose of this histological review is to give a brief representation of the morphological changes that occur throughout the cycle of mouse mammary gland development so that developmental changes observed in mouse models of mammary development can be appreciated.     

Eph and Ephrin Signaling in Mammary Gland Morphogenesis and Cancer

The Eph family of receptor tyrosine kinases and their membrane-bound ligands, the ephrins, play a central role in pattern formation during embryonic development and there is growing evidence that they are also instrumental in the control of tissue dynamics in the adult. The mammary gland is a paradigm for morphogenic processes occurring in the adult, since the gland develops predominantly postnatally and is subjected to continuous cyclic remodeling according to functional demands. Thus, pattern formation and the establishment of a functional organ structure are permanent themes in the mammary gland life cycle. In this paper we summarize the experimental evidence and discuss possible mechanisms by which Ephs and ephrins are modulating mammary epithelial cell adhesion, communication, and migration. Furthermore, we speculate on the different aspects of their influence on normal mammary gland development, function, and carcinogenesis.     

Bovine Mammary Progenitor Cells: Current Concepts and Future Directions

Although cell number is positively correlated with milk production, much remains to be learned about the bovine mammary stem cell and progenitor cells. Bovine mammary development is driven by many of the same classic mammogenic hormones studied in murine models, yet histologic features of bovine mammary development differ from that of rodent models. Most notably, terminal end buds, as they have been described for murine models, do not exist in the bovine mammary gland. However, among the most important common features of mammary development in disparate species is the involvement of histologically distinct, lightly staining epithelial cells as putative stem and progenitor cells. Although stem cell research has often focused on mammary development, mammary stem cells seemingly provide the basis for mammary growth and cell turnover in the mature animal. These cells provide an obvious focus for research aimed at increasing the efficiency of milk production. This review addresses recent findings concerning the histology and molecular physiology of putative bovine mammary stem and progenitor cell populations, areas where more study is critically needed, and areas where studies of bovine mammary physiology may present a unique opportunity to better understand mammary physiology in many species.     

Observations of cell function and morphology in the presence of silicone gel: an in vitro study

The project described in this article used in vitro tissue culture techniques and flow cytometry to determine if there are alterations in cell morphology in those cells that have been placed in contact with a commercially available medical-grade silicone gel used in mammary implants. We were unable to demonstrate significant changes in cell cycle characteristics following in vitro exposure for 1 to 12 days using human fibroblasts, mouse fibroblasts, and Chinese hamster ovary cells.     

Role of the CDK Inhibitor p27 (Kip1) in Mammary Development and Carcinogenesis: Insights from Knockout Mice

The cyclin-dependent kinase inhibitor p27 (Kip1) is an important cell cycle regulatory gene in breast cancer, and decreased p27 expression is associated with poor prognosis. Some investigations of its role in mammary development have demonstrated reduced cyclin D1 expression and consequent lack of lobuloalveolar development, but others have found increased cyclin E-Cdk2 activity and increased proliferation balanced by increased apoptosis. It is unclear at present why these apparently divergent results have been obtained. Mice with reduced p27 gene dosage alone do not develop mammary carcinomas but do display substantially shorter tumor latency upon overexpression of erbB2, consistent with a role for p27 as a mammary tumor suppressor gene. In this review we summarize these and other data addressing the role of p27 in normal mammary epithelium and experimental models of mammary carcinogenesis.     

Cell Surface β1,4-Galactosyltransferase Function in Mammary Gland Morphogenesis: Insights from Transgenic and Knockout Mouse Models

Development and morphogenesis are profoundly influenced by cell-cell and cell-extracellular matrix (ECM) interactions that are governed by cell surface receptor association with specific ligands. One such receptor is the long isoform of beta1,4-galactosyltransferase I (GalT I), a small proportion of which is targeted to the plasma membrane. Surface-expressed GalT I binds to specific glycoside residues on multiple extracellular ligands, and GalT I binding to specific ligands mediates cell-cell as well as cell-matrix interactions for a variety of cells, including mammary epithelia. Significant insight into surface GalT I function in mammary gland development and morphogenesis has been gained through the analysis of mouse transgenic and knockout models of surface GalT I misexpression. Overexpression of cell surface GalT I leads to impaired lactation as a result of reduced branching and differentiation and elevated apoptosis, while deleting surface GalT I enhances branching and differentiation and reduces apoptosis. These phenotypes can be attributed in large part to altered cell-ECM interactions. The current and future challenges are to use these mouse models to dissect the molecular mechanisms that govern surface GalT I function as a receptor in the normal mammary gland, as well as to assess the potential for surface GalT I misexpression to contribute to disease.     

A Specific Role for Cyclin D1 in Mammary Gland Development

Cyclin D1 is a critical component of the core cell cycle machinery. Mice lacking cyclin D1 develop mammary glands that fail to undergo normal lobuloalveolar proliferation during pregnancy. Thus, cyclin D1 seems to play a critical role in pregnancy-induced proliferation of mammary epithelium. Cyclin D1 also participates in neoplasia, as the majority of human mammary carcinomas contain elevated levels of this cyclin.     

Effect of combined oral contraceptives on breast epithelial proliferation in young women

The mammary gland undergoes morphologic changes during the menstrual cycle. Proliferation of normal breast epithelium is most extensive during the natural luteal phase. To determine the impact of one cycle of a combined oral contraceptive (COC) on breast homeostasis, we evaluated the proliferation index (PI), determined by KI-67 expression, in normal human mammary epithelial cells and correlated it with cellular proliferation in spontaneous menstrual cycles during the same period. Normal breast tissue samples were obtained from 82 patients randomized in two groups. Forty-two women in group A received one cycle of a COC (30 mug ethinyl estradiol and 150 mug levonorgestrel) administrated daily for 21 days, beginning on the first day of the menstrual cycle. Group B patients (n = 40) experienced a natural menstrual cycle. Menstrual cycle phase characterization was based on the date of the last period and subsequent menses and on progesterone serum levels obtained at the time of biopsy. The PI (number of Ki-67-positive nuclei per 1,000 epithelial cells), was significantly larger in group A (5.47 +/- 3.87), than in group B (3.27 +/- 3.24), p < 0.01. A cyclical variation of PI was observed in COC cycles. The rise in PI in the first week of the COC cycles was significantly higher than in the natural cycle (COC = 7.02 +/- 4.94; non-COC = 1.10 +/- 0.67; p < 0.0011). There was no significant difference between the two groups during the other weeks. Additionally, there was an inverse correlation between proliferation and chronological age, irrespective of the stage of the cycle. The PI of COC (p = 0.175) and natural cycles (p = 0.466) were not statistically different in younger patients. COC users have increased proliferative activity at the beginning of the menstrual cycle. This alteration in the pattern of proliferative activity may relate to the increased risk of breast cancer that has been associated with COCs.     

生殖周期中小鼠子宫生长抑素细胞的研究

为了解生殖周期中小鼠子宫生长抑素细胞分布及生长抑素含量的变化。采用免疫细胞化学技术观察小鼠子宫生长抑素细胞分布情况 ;以放射免疫方法检测生殖周期中小鼠子宫生长抑素的水平。结果显示 ,生殖周期中各期小鼠子宫内膜固有层均有生长抑素阳性细胞反应 ,多出现于子宫腺体周围或近肌层处固有层内 ,肌层间结缔组织偶见。妊娠第 17天 ,壁蜕膜内结缔组织及胎盘绒毛膜上皮下方胚性结缔组织 ,富含生长抑素阳性细胞。妊娠期小鼠子宫生长抑素水平明显下降 ,与间情期比较 ,有显著性差异 (P<0 .0 5)。结论 :生殖周期中各期小鼠子宫壁上有生长抑素阳性细胞分布 ;妊娠晚期壁蜕膜和胎盘绒毛膜上皮下方胚性结缔组织 ,含有相当数量生长抑素阳性细胞。妊娠期小鼠子宫生长抑素水平减少。生长抑素的细胞来源及其在生殖周期中对小鼠子宫的调节有待进一步研究     

Notch Signaling in Mammary Development and Oncogenesis

With the discovery of an activated Notch oncogene as a causative agent in mouse mammary tumor virus induced breast cancer in mice, the potential role for Notch signaling in normal and pathological mammary development was revealed. Subsequently, Notch receptors have been found to regulate normal development in many organ systems. In addition, inappropriate Notch signaling has been implicated in cancer of several tissues in humans and animal model systems. Here we review important features of the Notch system, and how it may regulate development and cancer in the mammary gland. A large body of literature from studies in Drosophila and C. elegans has not only revealed molecular details of how the Notch proteins signal to control biology, but shown that Notch receptor activation helps to define how other signaling pathways are interpreted. In many ways the Notch system is used to define the context in which other pathways function to control proliferation, differentiation, cell survival, branching morphogenesis, asymmetric cell division, and angiogenesis--all processes which are critical for normal development and function of the mammary gland.     

Common Integration Sites for MMTV in Viral Induced Mouse Mammary Tumors

The paradigm of mammary cancer induction by the mouse mammary tumor virus (MMTV) is used to illustrate the body of evidence that supports the hypothesis that mammary epithelial stem/progenitor cells represent targets for oncogenic transformation. It is argued that this is not a special case applicable only to MMTV-induced mammary cancer, because MMTV acts as an environmental mutagen producing random interruptions in the somatic DNA of infected cells by insertion of proviral DNA copies. In addition to disrupting the host genome, the proviral DNA also influences gene expression through its associated enhancer sequences over significant inter-genomic distances. Genes commonly affected by MMTV insertion in multiple individual tumors include, the Wnt, FGF, RSpo gene families as well as eIF3e and Notch4. All of these gene families are known to play essential roles in stem cell maintenance and behavior in a variety of organs. The MMTV-induced mutations accumulate in cells that are long-lived and possess the properties of stem cells, namely, self-renewal and the capacity to produce divergent epithelial progeny through asymmetric division. The evidence shows that epithelial cells with these properties are present in normal mammary glands, may be infected with MMTV, become transformed to produce epithelial hyperplasia through MMTV-induced mutagenesis and progress to frank mammary malignancy. Retroviral marking via MMTV proviral insertion demonstrates that this process progresses from a single mammary epithelial cell that possesses all of the features ascribed to tissue-specific stem cells.