Inappropriate P-cadherin expression in the mouse mammary epithelium is compatible with normal mammary gland function

Cadherins comprise a family of cell-cell adhesion proteins critical to the architecture and function of tissues. Expression of family members E-, N-, and P-cadherin is regulated in a spatial and temporal fashion in the developing and adult organism. Using in vivo and in vitro experimental systems, perturbation of cadherin expression by genetic deletion, overexpression, mutant dominant-negative constructs, and, to a lesser degree, expression of an inappropriate cadherin have all been shown to alter embryogenesis, tissue architecture, and cell behavior. Here we studied how expression of an inappropriate cadherin affects the adult mouse mammary gland. Human P-cadherin was expressed in mammary epithelial cells under control of the mouse mammary tumor virus (MMTV) promoter, and the effect on mammary gland behavior was studied. Typically, E-cadherin is expressed by mammary epithelial cells, whereas P-cadherin is found in myoepithelial cells and cap cells of the ductal terminal end bud. However, breast cancers frequently express P-cadherin, even though they are thought to arise from epithelial cells, and it is a marker of poor prognosis. We developed two independent transgenic mouse lines that exhibited high levels of P-cadherin protein expression in the mammary epithelium. P-cadherin was detected in most, but not all, luminal epithelial cells, and was appropriately localized to cell-cell borders. It was detected in the mammary glands of virgin, pregnant, lactating, post-lactation, and aged parous female mice. Despite the robust and widespread expression of an inappropriate cadherin, no effect was observed on mammary gland morphogenesis, architecture, lactation, or involution in transgenic mice compared to wild-type mice. No mammary tumors formed spontaneously in either wild-type or transgenic mice. Moreover, mammary tumors induced by the neu oncogene, which was introduced by a breeding strategy, showed no differences between mice with or without hP-cadherin. Surprisingly, however, none of the tumors expressed hP-cadherin protein. Together, our studies show no apparent effect on adult mammary gland or tumor behavior by inappropriate expression of P-cadherin in normal mammary epithelial cells.     

Cadherins and the mammary gland

Cadherin cell-cell adhesion proteins are critical for the formation of tissues from single cells. E-and P-cadherin play important roles in the architecture and function of the normal mammary gland. In breast cancers, the expression, or lack thereof, of E-cadherin can differentiate tumor types, whereas the misexpression of either P-cadherin or N-cadherin can be a marker of poor prognosis or increased malignancy, respectively. Additional research is needed to more precisely define the roles of both classical and desmosomal cadherins and their downstream signaling events, in the development and malignant behavior of breast cancers.     

Long-term organ culture of mouse mammary gland

Summary A method for maintaining mouse mammary gland in organ culture for periods of at least 30 days is described. Strips of the number four mammary glands were cultured in individual tubes while fully submerged in Medium 199 supplemented with insulin, aldosterone, ovine prolactin and bovine growth hormone. Exchange processes were aided by slowly rotating the tubes during culture. Mammary tissue from midpregnant BALB/c and virgin GR/A mice was induced to undergo lobulo-alveolar development, secrete and remain differentiated and metabolically active for the period of culture. Cells of both the ductal and alveolar epithelium continued to synthesize DNA and divide. The submerged roller-tube culture allows the use of larger pieces of tissue than can be accommodated in static culture, and the technique may prove applicable to the culture of a variety of tissues.     

Matrix metalloproteinases and their role in psoriasis

This review summarizes the contribution of matrix metalloproteinases to the pathogenesis of psoriasis. In psoriasis, matrix metalloproteinases are involved in the structural changes of the epidermis via the modification of intracellular contacts and the composition of the extracellular matrix, promoting angiogenesis in the dermal blood vessels and the infiltration of immune cells. Moreover, some matrix metalloproteinases become differentially expressed during the disease eruption and their expression correlates with the clinical score. A separate section of the review is dedicated to the pharmacological approaches that are used to control matrix metalloproteinases, such as oral metalloproteinase inhibitors, such as azasugars and phosphonamides.     

Matrix metalloproteinases in tumor-host cell communication

The microenvironment or stroma immediately surrounding tumor cells consists of a three-dimensional extracellular matrix (ECM) and stromal cells such as fibroblasts and inflammatory cells. The matrix metalloproteinases (MMPs) constitute a family of over 24 members, which collectively are capable of degrading virtually the entire ECM. Strict regulation of MMP expression is critical in order to maintain proper ECM homeostasis, but in disease states such as cancer there is often a high level of MMP activity at the tumor-stroma interface. Several studies have documented the importance of MMP-mediated ECM destruction in the successful dissemination of several tumor types, but it has become increasingly clear that they are also involved in earlier stages of tumorigenesis. MMPs are implicated in a wide variety of roles that can assist tumor initiation, growth, migration, angiogenesis, the selection of apoptosis-resistant subpopulations, and in invasion and metastasis. Interestingly, the factors responsible for many of these effects are derived from the cell surfaces of the tumor or stromal cells or are embedded in the ECM. Therefore, the MMPs can no longer be thought of solely as ECM destructionists, but as part of an elegant communication system through which the tumor interacts with the stroma.     

High-affinity folate binding in human mammary gland

High-affinity³H-folate binding in Triton X-100 solubilized human mammary gland tissue displayed characteristics, e.g. apparent positive cooperativity and increasing affinity with decreasing concentration of folate binding protein, shown to be typical of specific folate binding. Radioligand dissociation was slow at pH 7.4. A major fraction of the bound radioligand dissociated rapidly at pH 3.5, while a residual binding of 20% persisted even after prolonged dialysis at pH 3.5. Gel chromatography revealed two major folate binding proteins (M_r100 kDa and 25 kDa). However, only one single band was detectable on SDS-PAGE immunoblotting. The highest folate binding activity per g protein was associated with the upper triglyceride-containing layer of the 1000 g supernatant of the homogenate. The folate binding protein extracted from this layer had a low cross-reactivity (<5%) with rabbit antibodies against 25 kDa human milk folate binding protein. The folate binding protein in the 1000 g pellet and the aqueous phase of the 1000 g supernatant was present at a low concentration and had a cross-reactivity of 100%.     

Effect of mammogenic hormones on the expression of FGF7, FGF10 and their receptor in mouse mammary gland

To investigate the regulation of estrogen, progesterone and prolactin stimulating the development of mammary gland, the Kunming mice were used as experimental animals in this study. Through the experiment in vitro, the effect of mammogenic hormones were systematically investigated on expression of FGF7 and FGF10 and their receptor in different periods. The results are as follows: in mammary glands of mice, 17 beta-estradiol increased the expression of FGF7; progesterone did not affect the expression of FGF7; prolactin up-regulated the expression of FGF7 significantly in pregnancy and lactation. 17 beta-estradiol increased the expression of FGF10; progesterone and prolactin reduced the expression of FGF10 significantly in virgin; prolactin significantly increased the expression of FGF10 in pregnancy. When 17 beta-estradiol in the body was in relatively high proportion, it would lower the expression of KGFR; while 17 beta-estradiol in the body was in relatively low proportion, it would increase the expression of KGFR. Low concentration of progesterone increased the expression of KGFR and high progesterone did not affect the expression of KGFR. Prolactin increased the expression of KGFR significantly in pregnancy and lactation.     

Effect of mammogenic hormones on the expression of dFGF7, FGF10 and their receptor in mouse mammary gland

To investigate the regulation of estrogen, progesterone and prolactin stimulating the development of mammary gland, the Kunming mice were used as experimental animals in this study.Through the ex-periment in vitro, the effect of mammogenic hormones were systematically investigated on expression of FGF7 and FGF10 and their receptor in different periods.The results are as follows:in mammary glands of mice, 17 beta-estradiol increased the expression of FGF7;progesterone did not affect the expression of FGF7;prolactin up-regulated the expression of FGF7 significantly in pregnancy and lac-tation.17 beta-estradiol increased the expression of FGF10;progesterone and prolactin reduced the expression of FGF10 significantly in virgin;prolactin significantly increased the expression of FGF10 in pregnancy.When 17 beta-estradiol in the body was in relatively high proportion, it would lower the ex-pression of KGFR;while 17 beta-estradiol in the body was in relatively low proportion, it would increase the expression of KGFR.Low concentration of progesterone increased the expression of KGFR and high progesterone did not affect the expression of KGFR.Prolactin increased the expression of KGFR significantly in pregnancy and lactation.     

Advances in assays of matrix metalloproteinases (MMPs) and their inhibitors

Matrix metalloproteinases (MMPs) play an important role in many physiological and pathological processes. To assay the activities of MMPs is important in diagnosis and therapy of the MMPs associated diseases, such as neoplastic, rheumatic and cardiovascular diseases. Several assay systems have been developed, which include bioassay, zymography assay, immunoassay, fluorimetric assay, radio isotopic assay, phage-displayed assay, multiple-enzyme/multiple-reagent assay and activity-based profiling assay. The principle, application, advantage and disadvantage of these assays have been reviewed in this article.     

Matrix metalloproteinases and gastrointestinal cancers: Impacts of dietary antioxidants

The process of carcinogenesis is tightly regulated by antioxidant enzymes and matrix degrading enzymes, namely, matrix metalloproteinases(MMPs). Degradation of extracellular matrix(ECM) proteins like collagen, proteoglycan, laminin, elastin and fibronectin is considered to be the prerequisite for tumor invasion and metastasis. MMPs can degrade essentially all of the ECM components and, most MMPs also substantially contribute to angiogenesis, differentiation, proliferation and apoptosis. Hence, MMPs are important regulators of tumor growth both at the primary site and in distant metastases; thus the enzymes are considered as important targets for cancer therapy. The implications of MMPs in cancers are no longer mysterious; however, the mechanism of action is yet to be explained. Herein, our major interest is to clarify how MMPs are tied up with gastrointestinal cancers. Gastrointestinal cancer is a variety of cancer types, including the cancers of gastrointestinal tract and organs, i.e., esophagus, stomach, biliary system, pancreas, small intestine, large intestine, rectum and anus. The activity of MMPs is regulated by its endogenous inhibitor tissue inhibitor of metallopro-teinase(TIMP) which bind MMPs with a 1:1 stoichiometry. In addition, RECK(reversion including cysteinerich protein with kazal motifs) is a membrane bound glycoprotein that inhibits MMP-2,-9 and-14. Moreover, α2-macroglobulin mediates the uptake of several MMPs thereby inhibit their activity. Cancerous conditions increase intrinsic reactive oxygen species(ROS) through mitochondrial dysfunction leading to altered protease/anti-protease balance. ROS, an index of oxidative stress is also involved in tumorigenesis by activation of different MAP kinase pathways including MMP induction. Oxidative stress is involved in cancer by changing the activity and expression of regulatory proteins especially MMPs. Epidemiological studies have shown that high intake of fruits that rich in antioxidants is associated with a lower cancer incidence. Evidence indicates that some antioxidants inhibit the growth of malignant cells by inducing apoptosis and inhibiting the activity of MMPs. This review is discussed in six subchapters, as follows.     

Role of ovarian secretions in mammary gland development and function in ruminants

The mammary gland is a dynamic organ that undergoes cyclic developmental and regressive changes during the lifetime of a female mammal. Mammogenesis begins during embryonic life with the development of the first mammary gland rudiments and ductal system. After birth, during the pre-pubertal period, the ductal growth of the mammary parenchyma occurs through the fat pad. In most of the ruminant species allometric mammary parenchyma development begins with the onset of cyclic ovarian secretions activity. The two main hormones secreted during an ovarian cycle are estradiol and progesterone. These steroid hormones are derived from cholesterol and are synthesized by theca and granulosa cells in ovaries. During puberty, the mammary parenchyma develops in a compact, highly arborescent parenchymal mass surrounded by a dense connective matrix. Ductal elongation and lobulo-alveolar development are accomplished during growth and pregnancy to prepare for future milk production. At the end of lactation, the mammary gland undergoes involution, which corresponds to a regression of the secretory tissue, a reduction in the alveolar size and a loss of mammary epithelial cells (MECs). Ovarian steroids (estradiol and progesterone) appear to be key regulators of the different stages of mammogenesis and mammary function. Through this review, the role and the importance of ovarian steroids on mammary gland and on MECs is described.     

乳腺上皮细胞微量元素转运机制研究进展

新生儿生长发育所需的微量元素主要从母乳中获得,微量元素参与了机体的许多生命活动,如酶的活性、细胞增殖及分化等。乳腺上皮细胞含有多种微量元素转运体系,如锌离子转运体系（Zip／ZnT）、铁离子转运体系（DMTl／FPN）和铜离子转运体系（Ctrl／ATP7）。在分泌乳汁的同时,这些转运蛋白对锌、铁、铜等微量元素的吸收、转运和分泌起着重要的作用。同时这些微量元素的转运及代谢受到多种因素的调控,使母乳中微量元素含量达到动态稳定,以满足新生儿生长发育各阶段对微量元素的需求。对近年来锌、铁、铜三种微量元素在乳腺上皮细胞内转运机制的研究进展进行综述。     

Microarray analysis of gene expression profiles in the bovine mammary gland during lactation

Mammary glands undergo functional and metabolic changes during virgin, lactation and dry periods. A total of 122 genes were identified as differentially expressed, including 79 up-regulated and 43 down-regulated genes during lactation compared with virgin and dry periods. Gene ontology analysis showed the functional classification of the up-regulated genes in lactation, including transport, biosynthetic process, signal transduction, catalytic activity, immune system process, cell death, and positive regulation of the developmental process. Microarray data clarified molecular events in bovine mammary gland lactation.     

Gene expression profiling in porcine mammary gland during lactation and identification of breed-and developmental-stage-specific genes

A total of 28941 ESTs were sequenced from five 5′-directed non-normalized cDNA libraries, which were assembled into 2212 contigs and 5642 singlets using CAP3. These sequences were annotated and clustered into 6857 unique genes, 2072 of which having no functional annotations were considered as novel genes. These genes were further classified into Gene Ontology categories. By comparing the expression profiles, we identified some breed-and developmental-stage-specific gene groups. These genes may be relative to reproductive performance or play important roles in milk synthesis, secretion and mammary involution. The unknown EST sequences and expression profiles at different developmental stages and breeds are very important resources for further research.     

Matrix metalloproteinases: protective roles in cancer

The original notion that matrix metalloproteinases (MMPs) act as tumour and metastasis-promoting enzymes by clearing a path for tumour cells to invade and metastasize has been challenged in the last decade. It has become clear that MMPs are involved in numerous steps of tumour progression and metastasis, and hence are now considered to be multifaceted proteases. Moreover, more recent experimental evidence indicates that some members of the MMP family behave as tumour-suppressor enzymes and should therefore be regarded as anti-targets in cancer therapy. The complexity of the pro- and anti-tumorigenic and -metastatic functions might partly explain why broad-spectrum MMP inhibitors failed in phase III clinical trials. This review will provide a focussed overview of the published data on the tumour-suppressive behaviour of MMPs.     

Gene expression profiling in porcine mammary gland during lactation and identification of breed-and developmental-stage-specific genes

The mammary gland provides an excellent system to study questions pertaining to organogenesis, cell differentiation and oncogenesis. Intensive efforts have been made to understand the development of the mammary gland, particularly in terms of lactogenesis…     

Expression of human lysozyme mRNA in the mammary gland of transgenic mice

Owing to its inherent antimicrobial effect and positive charge, the expression of human lysozyme in bovine milk could be beneficial by altering the overal microbial level and the functional and physical properties of the milk. We have used transgenic mice as model systems to evaluate the expression of human lysozyme containing fusion gene constructs in the mammary gland. Expression of human lysozyme was targeted to the mammary gland by using the 5 promoter elements of either the bovine (line B mice) or _s1 (line H mice) casein genes coupled to the cDNA for human lysozyme. Expression of human lysozyme mRNA was not found in mammary tissue from any of line B mice. Tissues were analysed from six lines of H mice and two, H6 and H5, were found to express human lysozyme mRNA in the mammary gland at 42% and 116%, respectively, of the levels of the endogenous mouse whey acidic protein gene. At peak lactation, female mice homozygous for the H5 and H6 transgene have approximately twice the amount of mRNA encoding human lysozyme as hemizygous animals. Expression levels of human lysozyme mRNA in the mammary gland at time points representing late pregnancy, early, peak and late lactation corresponded to the profile of casein gene expression. Human lysozyme mRNA expression was not observed in transgenic males, virgin females or in the kidney, liver, spleen or brain of lactating females. A very low level of expression of human lysozyme mRNA was observed in the salivary gland of line H5.     

Matrix metalloproteinases as stromal effectors of human carcinoma progression: Therapeutic implications

The matrix metalloproteinases (MMPs) are extracellular zinc-enzymes implicated in a number of physiological and pathological tissue remodeling processes, including cancer progression. For a long time they have been thought to be produced by malignant cells and to specifically contribute to tumor invasion, through their ability to degrade extracellular matrix components. However, studies performed over the last few years have demonstrated that extracellular proteinases implicated in the progression of human carcinomas, including most MMPs, are in fact predominantly expressed by stromal and not by cancer cells. Furthermore, membrane receptors, activators and/or binding sites for some of these proteinases are also predominantly found to be associated with stromal cells. These findings, together with the observation that MMPs can cleave some molecules implicated in controlling growth factor activities, suggest that the role of MMPs during cancer progression is not limited to facilitating malignant cell invasion alone but is also likely to participate in other aspects of the malignant phenotype. MMPs should in fact be regarded as pan-regulators of tissue neoformation characteristic of malignant tumors, which includes both epithelial cell expansion and stroma formation. In this context, synthetic MMP inhibitors which are presently designed should lead to the development of a new generation of anticancer agents which additional beneficial properties compared to the existing cytotoxic agents used in the treatment of human malignancies.     

The role of microRNAs regulating the expression of matrix metalloproteinases (MMPs) in breast cancer development,progression, and metastasis

MicroRNAs (miRNAs) regulate several biological and physiological processes in mammalian cells, including cellular proliferation, differentiation, apoptosis, and metabolism. Recent studies have confirmed the alteration of them during the cancer development. Matrix metalloproteinases (MMPs), belonging to the large family of proteases, have also been demonstrated to play crucial roles in tissue remodeling, and to support cancer progression and metastasis. There are several known miRNAs which regulate the MMP family and their expression. The expression profiles of miRNAs involved in MMP regulation, change during cancer progression, and metastasis. The present review focuses on important miRNAs capable of targeting MMPs through direct and indirect interactions during the breast cancer development, progression, and metastasis.