Muc1 And Metastatic Cancer: Expression, Function And Therapeutic Targeting.
Source: Cell Adhesion & Migration
MUC1 is a transmembrane mucin that is often overexpressed in metastatic cancers and often used as a diagnostic marker for metastatic progression. The extracellular domain of MUC1 can serve as a ligand for stromal and endothelial cell adhesion receptors, and the cytoplasmic domain engages in several interactions that can result in increased migration and invasion, as well as survival. In this review, we address the role of MUC1 in metastatic progression by assessing clinical studies reporting MUC1 levels at various disease stages, reviewing mouse models utilized to study the role of MUC1 in metastatic progression, discuss mechanisms of MUC1 upregulation, and detail MUC1 protein interactions and signaling events. We review interactions between MUC1 and the extracellular environment, with proteins colocalized in the plasma membrane and/or cytoplasmic proteins, and summarize the role of MUC1 in the nucleus as a transcriptional cofactor. Finally, we review recent publications describing current therapies targeting MUC1 in patients with advanced disease and the stage of these therapies in preclinical development or clinical trials.<br /><br />
Muc1 Drives C Met Dependent Migration And Scattering.
Source: Molecular Cancer Research : Mcr
The transmembrane mucin MUC1 is overexpressed in most ductal carcinomas, and its overexpression is frequently associated with metastatic progression. MUC1 can drive tumor initiation and progression via interactions with many oncogenic partners, including β-catenin, the EGF receptor (EGFR) and Src. The decoy peptide protein transduction domain MUC1 inhibitory peptide (PMIP) has been shown to inhibit the tumor promoting activities of MUC1 in breast and lung cancer, including cell growth and invasion, and its usage suppresses metastatic progression in mouse models of breast cancer. To further characterize the reduced metastasis observed upon PMIP treatment, we conducted motility assays and observed that PMIP inhibits cell motility of breast cancer cells. To determine the mechanism by which PMIP inhibits motility, we evaluated changes in global gene transcription upon PMIP treatment, and identified a number of genes with altered expression in response to PMIP. Among these genes is the metastatic mediator, c-Met, a transmembrane tyrosine kinase that can promote cell scattering, migration, and invasion. To further investigate the role of c-Met in MUC1-dependent metastatic events, we evaluated the effects of MUC1 expression and EGFR activation on breast cancer cell scattering, branching, and migration. We found that MUC1 strongly promoted all of these events and this effect was further amplified by EGF treatment. Importantly, the effect of MUC1 and EGF on these phenotypes was dependent upon c-Met activity. Overall, these results indicate that PMIP can block the expression of a key metastatic mediator, further advancing its potential use as a clinical therapeutic.<br /><br />
Hugl1 And Hugl2 In Mammary Epithelial Cells: Polarity, Proliferation, And Differentiation.
Source: Plo S One
Loss of epithelial polarity is described as a hallmark of epithelial cancer. To determine the role of Hugl1 and Hugl2 expression in the breast, we investigated their localization in human mammary duct tissue and the effects of expression modulation in normal and cancer cell lines on polarity, proliferation and differentiation. Expression of Hugl1 and Hugl2 was silenced in both MCF10A cells and Human Mammary Epithelial Cells and cell lines were grown in 2-D on plastic and in 3-D in Matrigel to form acini. Cells in monolayer were compared for proliferative and phenotypic changes while acini were examined for differences in size, ability to form a hollow lumen, nuclear size and shape, and localization of key domain-specific proteins as a measure of polarity. We detected overlapping but distinct localization of Hugl1 and Hugl2 in the human mammary gland, with Hugl1 expressed in both luminal and myoepithelium and Hugl2 largely restricted to myoepithelium. On a plastic surface, loss of Hugl1 or Hugl2 in normal epithelium induced a mesenchymal phenotype, and these cells formed large cellular masses when grown in Matrigel. In addition, loss of Hugl1 or Hugl2 expression in MCF10A cells resulted in increased proliferation on Matrigel, while gain of Hugl1 expression in tumor cells suppressed proliferation. Loss of polarity was also observed with knockdown of either Hugl1 or Hugl2, with cells growing in Matrigel appearing as a multilayered epithelium, with randomly oriented Golgi and multiple enlarged nuclei. Furthermore, Hugl1 knock down resulted in a loss of membrane identity and the development of cellular asymmetries in Human Mammary Epithelial Cells. Overall, these data demonstrate an essential role for both Hugl1 and Hugl2 in the maintenance of breast epithelial polarity and differentiated cell morphology, as well as growth control.<br /><br />
Cd44 Promotes Epithelial Mammary Gland Development And Exhibits Altered Localization During Cancer Progression.
Source: Genes & Cancer
The basal cell layer has emerged as a critical player in cancer progression, and understanding the molecular contribution of specific cell types is important in treatment and prevention. The adhesion receptor CD44, which mediates epithelial-stromal and cell-cell interactions, has been shown to both promote and suppress tumor progression. To better understand the normal function of CD44, we have investigated its role in mouse mammary gland development and its expression in human breast and prostate cancer. We have found that CD44 is expressed in the myoepithelium of the developing mammary gland and modulates ductal development of FVB/N mice. The loss of CD44 results in defective luminal-myoepithelial cell-cell adhesion and promotes the mixing of luminal and myoepithelial layers, disrupting epithelial bilayer organization, and CD44-null mice experience delayed ductal outgrowth and impaired terminal end bud formation. The myoepithelial expression of CD44 is also relevant to its expression in cancer, as CD44 is expressed in the basal cells of early-stage breast and prostate cancer but exhibits altered localization with increasing tumorigenicity and is strongly expressed by tumor epithelium.<br /><br />
Understanding The Dual Nature Of Cd44 In Breast Cancer Progression.
Source: Molecular Cancer Research : Mcr
CD44 has been the subject of extensive research for more than 3 decades because of its role in breast cancer, in addition to many physiological processes, but interestingly, conflicting data implicate CD44 in both tumor suppression and tumor promotion. CD44 has been shown to promote protumorigenic signaling and advance the metastatic cascade. On the other hand, CD44 has been shown to suppress growth and metastasis. Histopathological studies of human breast cancer have correlated CD44 expression with both favorable and unfavorable clinical outcomes. In recent years, CD44 has garnered significant attention because of its utility as a stem cell marker and has surfaced as a potential therapeutic target, necessitating a greater understanding of CD44 in breast cancer. In this review, we attempt to unify the literature implicating CD44 in both tumor promotion and suppression, and explain its dualistic nature.<br><br>
Cell Receptor And Surface Ligand Density Effects On Dynamic States Of Adhering Circulating Tumor Cells.
Source: Lab On A Chip
Dynamic states of cancer cells moving under shear flow in an antibody-functionalized microchannel are investigated experimentally and theoretically. The cell motion is analyzed with the aid of a simplified physical model featuring a receptor-coated rigid sphere moving above a solid surface with immobilized ligands. The motion of the sphere is described by the Langevin equation accounting for the hydrodynamic loadings, gravitational force, receptor-ligand bindings, and thermal fluctuations; the receptor-ligand bonds are modeled as linear springs. Depending on the applied shear flow rate, three dynamic states of cell motion have been identified: (i) free motion, (ii) rolling adhesion, and (iii) firm adhesion. Of particular interest is the fraction of captured circulating tumor cells, defined as the capture ratio, via specific receptor-ligand bonds. The cell capture ratio decreases with increasing shear flow rate with a characteristic rate. Based on both experimental and theoretical results, the characteristic flow rate increases monotonically with increasing either cell-receptor or surface-ligand density within certain ranges. Utilizing it as a scaling parameter, flow-rate dependent capture ratios for various cell-surface combinations collapse onto a single curve described by an exponential formula.<br><br>
A High Performance Microsystem For Isolating Circulating Tumor Cells.
Source: Lab On A Chip
A unique flow field pattern in a bio-functional microchannel is utilized to significantly enhance the performance of a microsystem developed for selectively isolating circulating tumor cells from cell suspensions. For high performance of such systems, disposal of maximum non-target species is just as important as retention of maximum target species; unfortunately, most studies ignore or fail to report this aspect. Therefore, sensitivity and specificity are introduced as quantitative criteria to evaluate the system performance enabling a direct comparison among systems employing different techniques. The newly proposed fluidic scheme combines a slow flow field, for maximum target-cell attachment, followed by a faster flow field, for maximum detachment of non-target cells. Suspensions of homogeneous or binary mixtures of circulating breast tumor cells, with varying relative concentrations, were driven through antibody-functionalized microchannels. Either EpCAM or cadherin-11 transmembrane receptors were targeted to selectively capture target cells from the suspensions. Cadherin-11-expressing MDA-MB-231 cancer cells were used as target cells, while BT-20 cells were used as non-target cells as they do not express cadherin-11. The attachment and detachment of these two cell lines are characterized, and a two-step attachment/detachment flow field pattern is implemented to enhance the system performance in capturing target cells from binary mixtures. While the system sensitivity remains high, above 0.95, the specificity increases from about 0.85 to 0.95 solely due to the second detachment step even for a 1 : 1000 relative concentration of the target cells.<br><br>
Pilot Study On The Effects Of Dietary Conjugated Linoleic Acid On Tumorigenesis And Gene Expression In Py Mt Transgenic Mice.
Conjugated linoleic acid (CLA) is a class of commercially available fatty acids that have been associated with anticancer properties in rodent models of chemical carcinogenesis. We conducted a pilot study to examine the antitumor effect of dietary CLA in a polyoma virus-middle T antigen (PyMT) mouse model of invasive breast cancer. Virgin 4-week-old PyMT mice were administered a mixed-isomer CLA diet (1% wt/wt) or control AIN-93G diet for 4 weeks (N = 6 and 5, respectively) and tumor burden was assessed at 8 weeks of age. Thoracic mammary glands were prepared as whole mounts with other glands being formalin fixed and paraffin embedded for histology and immunohistochemistry (IHC). Total RNA was prepared for microarray and real-time reverse transcription-polymerase chain reaction analysis. Western blots were performed for protein expression analysis. Tumor incidence was significantly increased in CLA-treated animals compared with controls (P = 0.009) and occurred with extensive lobular-alveolar expansion and loss of mammary adipose tissue. More than 100 genes were downregulated > or = 2-fold in the CLA-treated group compared with controls, including adipose-specific markers, as wells as cytoskeletal and adhesion-related genes. This was supported by dramatic decreases in the epithelial adherens E-cadherin and beta-catenin as demonstrated by IHC. Taken together, these results suggest that dietary CLA affects the mammary stromal environment, leading to tumor progression and cellular expansion in the PyMT mouse model. Further studies of the potential for cancer promotion are needed, especially because mixed-isomer CLA formulations are sold commercially as a nutritional supplement.<br><br>
Muc1 Regulates Nuclear Localization And Function Of The Epidermal Growth Factor Receptor.
Source: Journal Of Cell Science
Alteration of protein trafficking and localization is associated with several diseases, including cystic fibrosis, breast cancer, colorectal cancer, leukemia and diabetes. Specifically, aberrant nuclear localization of the epidermal growth factor receptor (EGFR), a receptor tyrosine kinase, is a poor prognostic indicator in several epithelial carcinomas. It is now appreciated that in addition to signaling from the plasma membrane, EGFR also trafficks to the nucleus, and can directly bind the promoter regions of genes encoding cyclin D1 (CCND1) and B-Myb (MYBL2). We have previously established that loss of MUC1 in an EGFR-dependent transgenic mouse model of breast cancer correlates with the loss of cyclin D1 expression. Here, we provide evidence for a novel regulatory function of MUC1 in the trafficking and nuclear activity of EGFR. We found that MUC1 and EGFR interact in the nucleus of breast cancer cells, which promotes the accumulation of chromatin-bound EGFR. Additionally, the presence of MUC1 results in significant colocalization of EGFR and phosphorylated RNA polymerase II, indicating that MUC1 influences the association of EGFR with transcriptionally active promoter regions. Importantly, we found that the loss of MUC1 expression resulted in a decrease in the interaction between EGFR and the CCND1 promoter, which translated to a significant decrease in cyclin D1 protein expression. This data offers insights into a novel regulatory mechanism of EGFR nuclear function and could have important implications for evaluating nuclear localization in cancer.<br><br>
Anti Cancer Therapies That Utilize Cell Penetrating Peptides.
Source: Recent Patents On Anti Cancer Drug Discovery
Cell penetrating peptides (CPPs) are 9-35mer cationic and/or amphipathic peptides that are rapidly internalized across cell membranes. Importantly, they can be linked to a variety of cargo, including anti-cancer therapeutics, making CPPs an efficient, effective and non-toxic mechanism for drug delivery. In this review, we discuss a number of CPP conjugated therapies (CTTs) that are either patented are in the progress of patenting, and show strong promise for clinical efficacy. The CTTs discussed here target a number of different processes specific to cancer progression, including proliferation, survival and migration. In addition, many of these CTTs also increase sensitivity to current anti-cancer therapy modalities, including radiation and other DNA damaging chemotherapies, thereby decreasing the toxic dosage required for effective treatment. Mechanistically, these CTTs function in a dominant-negative manner by blocking tumor-specific protein-protein interactions with the CPP-conjugated peptide or protein. The treatment of both cell lines and mouse models demonstrates that this method of molecular targeting results in equal if not greater efficacy than current standards of care, including DNA damaging agents and topoisomerase inhibitors. For the treatment of invasive carcinoma, these CTTs have significant clinical potential to deliver highly targeted therapies without sacrificing the patient's quality of life.<br><br>
Matrix Hyaluronan Alters Epidermal Growth Factor Receptor Dependent Cell Morphology.
Source: Cell Adhesion & Migration
EGFR, a critical regulator of oncogenic signaling during cancer progression, is capable of integrating multireceptor signaling pathways that promote metastasis. EGFR is subject to regulatory cues from the extracellular matrix (ECM), of which hyaluronan (HA) is a major component. In mammary tumors, HA is deposited in the ECM where it functions in biomechanical support and modulates intracellular signaling. We utilized a 3D collagen system in which HA is either polymerized in collagen matrix or provided soluble in the media (sHA). Here we report that collagen-embedded HA (eHA) inhibits EGFR activation, filopodia formation and cell spreading on a collagen matrix. These findings demonstrate a novel role for eHA as a protective molecule when encountered in the collagen matrix during cancer progression.<br><br>
Intracellular Muc1 Peptides Inhibit Cancer Progression.
Source: Clinical Cancer Research : An Official Journal Of The American Association For Cancer Research
PURPOSE:<br />During cancer progression, the oncoprotein MUC1 binds beta-catenin while simultaneously inhibiting the degradation of the epidermal growth factor receptor (EGFR), resulting in enhanced transformation and metastasis. The purpose of this study was to design a peptide-based therapy that would block these intracellular protein-protein interactions as a treatment for metastatic breast cancer.<br /><br />EXPERIMENTAL DESIGN:<br />The amino acid residues responsible for these interactions lie in tandem in the cytoplasmic domain of MUC1, and we have targeted this sequence to produce a MUC1 peptide that blocks the protumorigenic functions of MUC1. We designed the MUC1 inhibitory peptide (MIP) to block the intracellular interactions between MUC1/beta-catenin and MUC1/EGFR. To allow for cellular uptake we synthesized MIP adjacent to the protein transduction domain, PTD4 (PMIP).<br /><br />RESULTS:<br />We have found that PMIP acts in a dominant-negative fashion, blocking both MUC1/beta-catenin and MUC1/EGFR interactions. In addition, PMIP induces ligand-dependent reduction of EGFR levels. These effects correspond to a significant reduction in proliferation, migration, and invasion of metastatic breast cancer cells in vitro, and inhibition of tumor growth and recurrence in an established MDA-MB-231 immunocompromised (SCID) mouse model. Importantly, PMIP also inhibits genetically driven breast cancer progression, as injection of tumor-bearing MMTV-pyV mT transgenic mice with PMIP results in tumor regression and a significant inhibition of tumor growth rate.<br /><br />CONCLUSIONS:<br />These data show that intracellular MUC1 peptides possess significant antitumor activity and have important clinical applications in the treatment of cancer.<br /><br />
Transforming Growth Factor Alpha Dependent Cancer Progression Is Modulated By Muc1.
Source: Cancer Research
Transforming growth factor alpha (TGFalpha) is a potent inducer of cellular transformation, through its binding and activation of the epidermal growth factor receptor (EGFR). Previous studies in our laboratory showed that EGFR could also be affected by the glycoprotein MUC1, which inhibits ligand-stimulated degradation of EGFR in breast epithelial cell lines. To determine the effect of Muc1 expression on TGFalpha/EGFR-dependent breast transformation, we crossed the WAP-TGFalpha transgenic mouse model of breast cancer onto a Muc1-null background. We found that the loss of Muc1 expression dramatically affects mammary gland transformation and progression. Although 100% of WAP-TGFalpha/Muc1(+/+) mice form mammary gland tumors by 1 year, only 37% of WAP-TGFalpha/Muc1(-/-) form tumors by this time. This difference is also associated with a delay in onset, with a doubling of onset time observed in the WAP-TGFalpha/Muc1(-/-) compared with the WAP-TGFalpha/Muc1(+/+) mice. Analysis of signal transduction pathways revealed that activation of cyclin D1 expression is significantly suppressed in tumors derived from WAP-TGFalpha/Muc1(-/-) animals compared with those expressing Muc1. The loss of Muc1 expression also results in a significant inhibition in the formation of hyperplastic lesions during tumor progression. On the C57Bl/6 inbred background, pulmonary lesions were observed in 28 of 29 WAP-TGFalpha/Muc1(+/+) animals (including one metastatic pulmonary adenocarcinoma and multiple perivascular lymphomas), although none were detected in the WAP-TGFalpha/Muc1(-/-) animals. Together, these data indicate that Muc1 is an important modulator of TGFalpha-dependent tumor progression.<br /><br />
Muc1 Is A Novel Regulator Of Erb B1 Receptor Trafficking.
ErbB receptors are key regulators of cell survival and growth in normal and transformed tissues. The oncogenic glycoprotein MUC1 is a binding partner and substrate for erbB1 and MUC1 expression can potentiate erbB-dependent signal transduction. After receptor activation, erbB1 is typically downregulated via an endocytic pathway that results in receptor degradation or recycling. We report here that MUC1 expression inhibits the degradation of ligand-activated erbB1. Through the use of both RNAi-mediated knock down and overexpression constructs of MUC1, we show that MUC1 expression inhibits erbB1 degradation after ligand treatment in breast epithelial cells. This MUC1-mediated protection against erbB1 degradation can increase total cellular pools of erbB1 over time. Biotinylation of surface proteins demonstrates that cell-surface associated erbB1 receptor is protected by MUC1 against ligand-induced degradation, although this is accompanied by an increase in erbB1 internalization. The MUC1-mediated protection against degradation occurs with a decrease in EGF-stimulated ubiquitination of erbB1, and an increase in erbB1 recycling. These data indicate that MUC1 expression is a potent regulator of erbB1 receptor stability upon activation and may promote transformation through the inhibition of erbB1 degradation.<br /><br />
Cd44 Attenuates Metastatic Invasion During Breast Cancer Progression.
Source: Cancer Research
Metastatic invasion is the primary cause of breast cancer mortality, and adhesion receptors, such as CD44, are believed to be critical in this process. Historically, primary breast tumor epithelium has been investigated in isolation from other tissue components, leading to the common interpretation that CD44 and its primary ligand, hyaluronan, promote invasion. Here, we provide in vivo evidence showing CD44 antagonism to breast cancer metastasis. In a mouse model of spontaneously metastasizing breast cancer (MMTV-PyV mT), we found that loss of CD44 promotes metastasis to the lung. Localization studies, in combination with a novel hyaluronan synthase-GFP transgenic mouse, show a restricted pattern of expression for CD44 and hyaluronan. Whereas CD44 is expressed in tumor epithelium, hyaluronan synthase expression is restricted to stromal-associated cells. This distinct CD44 and hyaluronan pattern of distribution suggests a role for epithelial-stromal interaction in CD44 function. To define the relevance of this spatial regulation, we developed an in vitro invasion assay to emulate invasion into the extracellular matrix. Invasion of CD44-positive tumor cells was inhibited in hyaluronan-containing matrices, whereas blocking CD44-hyaluronan association increased invasion. Collectively, these data show that during breast cancer progression, hyaluronan-CD44 dynamics occurring through epithelial-stromal interactions are protective against metastasis.<br /><br />
Muc1 Overexpression Results In Mammary Gland Tumorigenesis And Prolonged Alveolar Differentiation.
MUC1 is a transmembrane mucin that was initially cloned from malignant mammary epithelial cells as a tumor antigen. More than 90% of human breast carcinomas overexpress MUC1. Numerous studies have demonstrated an interaction between MUC1 and other oncogenic proteins such as beta-catenin, erbB receptors and c-Src, but a functional role for MUC1 in transformation has not been identified. We previously reported the development of transgenic mice that overexpress human MUC1 in the mouse mammary gland (MMTV-MUC1). Analysis of these transgenic mice at an early age demonstrated the ability of MUC1 to potentiate EGF-dependent activation of MAP kinase signaling pathways in the lactating mammary gland. We now report that multiparous MMTV-MUC1 transgenic mice stochastically develop unifocal mammary gland carcinomas late in life. Molecular analysis of these tumors shows a tumor-specific coimmunoprecipitation between MUC1 and beta-catenin. Examination of the contralateral glands in MMTV-MUC1 transgenics demonstrates that the development of frank carcinomas is accompanied by a failure of multiparous glands to undergo postlactational involution. Furthermore, uniparous MMTV-MUC1 transgenic mice display decreased postlactational apoptosis, elevated whey acidic protein expression and aberrant pErk2 activation. These findings are the first to determine that MUC1 overexpression promotes in vivo transformation of the mammary gland.<br /><br />
Muc1 Can Interact With Adenomatous Polyposis Coli In Breast Cancer.
Source: Biochemical And Biophysical Research Communications
The MUC1 tumor antigen is overexpressed on most breast tumors and metastases. It interacts with signaling proteins such as the ErbB kinases and beta-catenin, and is involved in mammary gland oncogenesis and tumor progression. Herein, we report a novel interaction between MUC1 and adenomatous polyposis coli (APC), a tumor suppressor involved in downregulating beta-catenin signaling. Initially identified in colorectal cancer, APC is also downregulated in breast tumors and presumably involved in mammary carcinogenesis. MUC1 and APC co-immunoprecipitate from the ZR-75-1 human breast carcinoma cell line and co-localize in mouse mammary glands and tumors. These studies also indicate that the association of MUC1 and APC may be increased by epidermal growth factor stimulation. Intriguingly, the co-immunoprecipitation of MUC1 and APC increases in human breast tumors and metastases as compared to adjacent normal tissues, indicating that this association may play a role in the formation and progression of breast tumors.<br /><br />
Form And Function Of Developing Heart Valves: Coordination By Extracellular Matrix And Growth Factor Signaling.
Source: Journal Of Molecular Medicine (Berlin, Germany)
It is becoming clear that converging pathways coordinate early heart valve development and remodeling into functional valve leaflets. The integration of these pathways begins with macro and molecular interactions outside the cell in the extracellular matrix separating the myocardial and endocardial tissue components of the rudimentary heart. Such interactions regulate events at the cell surface through receptors, proteases, and other membrane molecules which in turn transduce signals into the cell. These signals trigger intracellular cascades that transduce cellular responses through both transcription factor and cofactor activation mediating gene induction or suppression. Chamber septation and valve formation occur from these coordinated molecular events within the endocardial cushions to sustain unidirectional blood flow and embryo viability. This review discusses the emerging connection between extracellular matrix and growth factor receptor signaling during endocardial cushion morphogenesis by highlighting the extracellular component, hyaluronan, and erbB receptor functions during early valve development.<br /><br />
Muc1 Alters Beta Catenin Dependent Tumor Formation And Promotes Cellular Invasion.
MUC1 is aberrantly expressed in greater than 90% of all breast carcinomas, yet its function as a tumor antigen is not fully understood. Recently, studies have shown that MUC1 interacts with beta-catenin, erbB receptors, src, GSK-3beta and protein kinase Cdelta, possibly in a complex that promotes the disassembly of adherens junctions and the invasion of cells. Here we show that the deletion of Muc1 expression from MMTV-Wnt-1 transgenic mice results in a significant increase in the time to mammary gland tumor onset. Analysis of MMTV-Wnt-1 tumors on a wild-type Muc1 background shows a tumor-specific complex formation between Muc1 and beta-catenin that can be observed in both the membrane and the cytoplasm of transformed epithelium. Analysis of primary human adenocarcinomas revealed that this MUC1/beta-catenin interaction occurs in both primary and metastatic tumors, but is dramatically increased in metastatic lesions. Addition of MUC1-cytoplasmic domain peptides to the invasive MDA-MB-468 and MDA-MB-231 cell lines increases their invasive capability, and these peptides colocalize with both beta-catenin and the focal adhesion protein vinculin, primarily at sites of membrane invasion into a collagen matrix. These data indicate a potential mechanism for MUC1 promotion of invasive tumorigenesis in the breast through the modulation of beta-catenin localization and subsequent cytoskeletal dynamics.<br /><br />
Heart Valve Mesenchyme Formation Is Dependent On Hyaluronan Augmented Activation Of Erb B2 Erb B3 Receptors.
Source: Nature Medicine
Heart septation and valve malformations constitute the most common anatomical birth defects. These structures arise from the endocardial cushions within the atrioventricular canal (AVC) through dynamic interactions between cushion cells and the extracellular matrix (termed cardiac jelly). Transformation of endothelial cells to mesenchymal cells is essential for the proper development of the AVC and subsequent septation and valve formation. Atrioventricular septal defects can result from incomplete endocardial cushion morphogenesis. We show that hyaluronan-deficient AVC explants from Has2(-/-) embryos, which normally lack mesenchyme formation, are rescued by heregulin treatment, which restores phosphorylation of ErbB2 and ErbB3. These events were blocked using a soluble ErbB3 molecule, as well as with an inhibitor of ErbB2, herstatin. We show further that ErbB3 is activated during hyaluronan treatment of Has2(-/-) explants. These data provide a link between extracellular matrix-hyaluronan and ErbB receptor activation during development of early heart-valve and septal mesenchyme.<br /><br />
Erb B Beta Catenin Complexes Are Associated With Human Infiltrating Ductal Breast And Murine Mammary Tumor Virus (Mmtv) Wnt 1 And Mmtv C Neu Transgenic Carcinomas.
Source: The Journal Of Biological Chemistry
Simultaneous deregulation of both Wnt and ErbB growth factors has previously been shown to result in the cooperative induction of mammary gland tumors. Using the murine mammary tumor virus (MMTV)-Wnt-1 transgenic model of mammary carcinoma, we have identified an unvarying association between beta-catenin and epidermal growth factor receptor/c-Neu (ErbB1/ErbB2) heterodimers in mammary gland tumors, indicating a requirement for ErbB signaling in Wnt-mediated tumorigenesis. Expansion of these observations to a second transgenic model, MMTV-c-Neu, demonstrated similar tumor-specific interactions, including an ErbB1 ligand-inducible phosphorylation of both beta-catenin and c-Neu. Direct relevance of these findings to human breast cancer was established upon examination of a set of human infiltrating ductal breast adenocarcinoma and lymph node metastasis tissues taken at surgery. These data revealed increased levels of beta-catenin in tumors and metastases versus normal breast as well as an association between beta-catenin and c-Neu that measurably occurs only in neoplasia, most strongly in metastatic lesions. These studies have identified a seemingly indispensable interaction between beta-catenin and epidermal growth factor receptor/c-Neu heterodimers in Wnt-1-mediated breast tumorigenesis that may indicate a fundamental signaling event in human metastatic progression.<br /><br />
Transgenic Muc1 Interacts With Epidermal Growth Factor Receptor And Correlates With Mitogen Activated Protein Kinase Activation In The Mouse Mammary Gland.
Source: The Journal Of Biological Chemistry
MUC1 is a large (>400 kDa), heavily glycosylated transmembrane protein that is aberrantly expressed on greater than 90% of human breast carcinomas and subsequent metastases. The precise function of MUC1 overexpression in tumorigenesis is unknown, although various domains of MUC1 have been implicated in cell adhesion, cell signaling, and immunoregulation. Stimulation of the MDA-MB-468 breast cancer line as well as mouse mammary glands with epidermal growth factor results in the co-immunoprecipitation of MUC1 with a tyrosine-phosphorylated protein of approximately 180 kDa. We have generated transgenic lines overexpressing full-length (MMF), cytoplasmic tail deleted (DeltaCT), or tandem repeat deleted (DeltaTR)-human MUC1 under the control of the mouse mammary tumor virus promoter to further examine the role of MUC1 in signaling and tumorigenesis. Immunoprecipitation experiments revealed that full-length transgenic MUC1 physically associates with all four erbB receptors, and co-localizes with erbB1 in the lactating gland. Furthermore, we detected a sharp increase in ERK1/2 activation in MUC1 transgenic mammary glands compared with Muc1 null and wild-type animals. These results point to a novel function of increased MUC1 expression, potentiation of erbB signaling through the activation of mitogenic MAP kinase pathways.<br /><br />
Cooperative Induction Of Mammary Tumorigenesis By Tg Falpha And Wnts.
We previously reported that multiparous WAP-TGFalpha transgenic mice develop mammary gland carcinomas with complete incidence. TGFalpha-induced tumors appear stochastically and with relatively long latency, indicating an additional requirement for other genetic alterations. To identify genes that cooperate with TGFalpha in mammary tumorigenesis, we used a retroviral insertion approach featuring a cloned and infectious hybrid MMTV (C3H/Mtv-1; (Shackleford and Varmus, 1988)). Tumor latency was decreased approximately 30% in MMTV-infected WAP-TGFalpha transgenic animals compared to noninfected transgenic controls, and > 30% of the corresponding tumors displayed evidence of integrated C3H/Mtv-1 DNA. PCR-based analyses of DNAs from two virus-infected, transgenic tumors revealed integration of hybrid MMTV in 3' untranslated exons of the Wnt-1 or Wnt-3 oncogenes. Moreover, Northern blots confirmed dramatic induction of Wnt-1 or Wnt-3 transcripts in the respective tumors, indicating that MMTV integration resulted in activated expression of these genes. Semiquantitative RT-PCR analyses showed that overexpression of Wnt-1 or Wnt-3 was a common occurrence in MMTV-infected WAP-TGFalpha tumors, and some noninfected WAP-TGFalpha tumors also showed evidence of elevated Wnt-3 transcripts. Collectively, these results reveal cooperative induction of mammary gland tumorigenesis by simultaneous deregulation of EGF-like (TGFalpha) and Wnt growth factors.<br /><br />
Dynamic Expression And Activation Of Erbb Receptors In The Developing Mouse Mammary Gland.
Source: Cell Growth & Differentiation : The Molecular Biology Journal Of The American Association For Cancer Research
The complex system of ERBB receptors and ligands is implicated in growth and differentiation of the mammary gland. However, it has not been comprehensively examined in this dynamic tissue. Combined RNA and protein analyses of glands in different stages from virgin to involution revealed differential expression of the four ERBB receptors, as well as distinctive patterns of ERBB ligand expression that suggested specialized function. ERBB localization was linked to mammary gland function. Thus, in the virgin gland, ERBB1 and ERBB2 were colocalized to all major cell types during ductal morphogenesis but differentially localized in the mature gland. All four ERBB receptors were restricted to epithelia in the differentiated gland. Analyses of ERBB tyrosine phosphorylation provided strong evidence of interaction between the four receptors in this physiological context. Thus, exogenous EGF induced stage-dependent transphosphorylation of ERBB2-4 as well as ERBB1, whereas endogenous phosphorylation of all four receptors peaked in late pregnancy and lactation.<br /><br />
Characterization Of The Mouse Transforming Growth Factor Alpha Gene: Its Expression During Eyelid Development And In Waved 1 Tissues.
Source: Cell Growth & Differentiation : The Molecular Biology Journal Of The American Association For Cancer Research
The spontaneous mouse waved 1 (wa1) mutation is allelic with the transforming growth factor alpha (TGF-alpha) gene and produces phenotypes similar to those of TGF-alpha knockout mice. Here, we show that TGF-alpha mRNA and protein levels are measurable in wa1 tissues but reduced 5- to 30-fold relative to wild type. Because the wa1-coding sequence is identical to that of the normal mRNA, wa1 is not a null mutation. Nuclear run-on analyses revealed decreased transcription of the TGF-alpha gene in wa1 tissues, but the sequence of a 3.2-kb 5' flanking fragment containing the promoter was unaltered. Moreover, pulsed field gel electrophoresis analysis did not reveal alterations within 750 kb upstream or 350 kb downstream of the gene, and chromosome 6 was karyotypically normal. Hence, we speculate that the wa1 mutation may be subtle and/or reside at a greater distance from the TGF-alpha gene. TGF-alpha deficiency elicits a spectrum of variably penetrant eye anomalies in wa1 and knockout mice that are associated with open eyes at birth. We found that late-gestation wa1 and TGF-alpha-null embryos display a significant delay in eyelid closure, although the eyes of most embryos fuse prior to birth. In situ hybridization localized TGF-alpha expression to the advancing margins of the eyelid epithelium and epidermal growth factor receptor expression throughout the eyelid and corneal epithelia. These results suggest that eye problems observed in TGF-alpha-deficient adult mice arise from premature exposure and trauma to open eyes during or following parturition.<br /><br />
Inhibition Of Mammary Gland Involution Is Associated With Transforming Growth Factor Alpha But Not C Myc Induced Tumorigenesis In Transgenic Mice.
Source: Cancer Research
Deregulated expression of transforming growth factor alpha (TGF-alpha) or c-myc has been implicated in the genesis of human breast cancer. To better characterize the role of these molecules in this disease, we generated transgenic mice that express TGF-alpha or c-myc under control of the mouse whey acidic protein (WAP) promoter. We then compared the resulting mammary gland neoplasia in these mice and in previously described mice expressing a metallothionein-driven TGF-alpha transgene. Nonvirgin female mice in all transgenic lineages developed mammary tumors with 100% incidence but variable latency. Among TGF-alpha lines, mean survival time correlated with the level of transgene expression, and the average life spans of high-expressing WAP-TGF-alpha and WAP-c-myc mice were similarly reduced. The majority of TGF-alpha-induced tumors were relatively well-differentiated adenomas and adenocarcinomas; in contrast, WAP-c-myc tumors were poorly differentiated, solid carcinomas with a minority of adenocarcinomas. Most TGF-alpha and all c-myc-induced tumors were transplantable, but lung metastases were infrequently observed in all transgenic lines. WAP-TGF-alpha-induced tumors, in marked contrast to those induced by WAP-c-myc, displayed frequent induction of cyclin D1 mRNA, suggesting that expression of this gene may complement that of TGF-alpha during mammary tumor development. Expression of TGF-alpha also induced precocious development of pregnant glands and delayed or inhibited mammary involution. As a result, multiparious MT-TGF-alpha and especially WAP-TGF-alpha females accumulated large numbers of hyperplastic alveolar nodules that resembled the more differentiated TGF-alpha-induced tumors. Finally, coexpression of WAP-c-myc and WAP-TGF-alpha transgenes markedly decreased tumor latency, increased tumor growth, and even induced mammary tumors in virgin female and male mice. These findings provide further evidence for the importance of deregulated TGF-alpha expression in multistage carcinogenesis, and they suggest that in the mammary gland the mechanism of TGF-alpha-induced transformation may depend on postlactational survival of differentiated epithelium. They also provide evidence of a potent tumorigenic collaboration between TGF-alpha and c-myc in mammary epithelium.<br /><br />