Hypoxia increases VEGF-A production by prostate cancer and bone marrow stromal cells and initiates paracrine activation of bone marrow endothelial cells

Hypoxia develops at sites of rapid cancer growth near sites of poorly organized vasculature. Heparin binding growth factors (HBGFs) support neoangiogenesis of tumors. We examined the effect of culturing bone-targeted, metastatic C4-2B prostate cancer cells and bone stromal derived HS27a cells under hypoxic conditions on expression of vascular endothelial growth factor (VEGF) family members. A sealed chamber infused with 1% (hypoxic) or 20% (normoxic) O(2) was used. Both cell lines produced VEGF-A in normoxia, but little or no HB-EGF, another HBGF. HS27a cells produced low levels of FGF-2 and HGF, but little or none was secreted by C4-2B cells. Levels of VEGF-A in conditioned medium (CM) from both cell lines doubled when cultured in hypoxia. Similar changes in VEGF-A mRNA levels were seen. Receptor expression was unchanged by hypoxia. Changes in VEGF-A expression during hypoxia were preceded by nuclear accumulation of hypoxia inducible factor-1alpha (HIF-1alpha). Bone marrow endothelial (BME) cells express high levels of VEGFR2/flk-1, and are targets of VEGF-A induced neovascularization. BME cells proliferated in response to treatment with HS27a CM, but not C4-2B CM. BME cells formed tube-like angiogenic structures on growth factor reduced Matrigel in response to CM from HS27a or C4-2B cells. This response was greater when CM was produced under hypoxia, and was reduced by VEGF-A or FGF-2 neutralizing antibodies. We conclude that hypoxia triggers a physiologically relevant increase in VEGF-A by prostate cancer and bone marrow stromal cells which involves a paracrine loop that recruits and activates BME to support tumor neovascularization-related processes.

Repression of HIP/RPL29 expression induces differentiation in colon cancer cells

We had previously shown that the expression of heparin/heparan sulfate interacting protein/ribosomal protein L29 (HIP/RPL29) was upregulated in colon cancer tissues. The present study investigated the role of HIP/RPL29 in differentiation in colon cancer cells. Inducing cellular differentiation in HT-29 cells by both sodium butyrate and glucose deprivation resulted in a significant downregulation of HIP/RPL29 expression. The beta-catenin/Tcf-4 pathway is the most important pathway controlling the switch between cellular differentiation and proliferation in intestinal epithelial cells. Inducing differentiation by dominant-negative inhibition of the beta-catenin/Tcf-4 complexes in LS174T cells also resulted in downregulation of HIP/RPL29. To determine whether a lower expression of HIP/RPL29 could induce differentiation in cancer cells, small interfering RNA (siRNA) targeting HIP/RPL29 was transfected into LS174T cells. The resultant knockdown of HIP/RPL29 expression induced cellular differentiation, as shown by the increased expression of two known markers of differentiation in LS174T cells, galectin-4 and mucin-2. In addition, the differentiation process induced by repression of HIP/RPL29 expression was accompanied by the upregulation of p21 and p53. In conclusion, HIP/RPL29 plays a role in the cellular differentiation process in colon cancer cells. The differentiation process is at least partially mediated by the upregulation of p21 and p53 pathways.

Progesterone receptor isoforms A and B differentially regulate MUC1 expression in uterine epithelial cells

MUC1 expression responds differently to changes in progesterone (P) levels in mouse vs. human uterine epithelium. Two isoforms of progesterone receptor, PRA and PRB, mediate the physiological effects of P. Using transient transfection of a human uterine epithelial cell line, HEC-1A, we showed that liganded PRB stimulated MUC1 gene activity. PRA alone had little effect on MUC1 promoter activity, but antagonized the PRB-mediated stimulation. The region from 523 to 570 bp upstream of the transcriptional start site was shown to be required for the P response. Mutation of two potential P-responsive element (PRE) half-sites in this region partially inhibited the PRB-mediated response, and one PRE half-site disrupted binding of both PRB and PRA to a consensus PRE in an EMSA. These along with other studies indicated that multiple cis elements in the -523- to -570-bp region cooperate to mediate P responsiveness, and that PR interaction with other transcription factors in this region is likely. Using ovariectomized wild-type, PR knockout (PRKO), PRAKO, and PRBKO mice, P antagonism of estrogen-stimulated Muc1 protein and mRNA expression was shown to be dependent on PRA. In summary, these data show that liganded PRB stimulates MUC1 expression in human uterine epithelial cells, whereas liganded PRA antagonizes MUC1 expression in both human and mouse uterine epithelial cells. The differential MUC1 response to P in these two species may be due to dissimilar expression of the two PR isoforms in the uterine epithelium.

Ribozyme-mediated perlecan knockdown impairs chondrogenic differentiation of C3H10T1/2 fibroblasts

Perlecan (Pln) is an abundant heparan sulfate (HS) proteoglycan in the pericellular matrix of developing cartilage, and its absence dramatically disrupts endochondral bone formation. This study examined two previously unexamined aspects of the function of Pln in mesenchymal chondrogenesis in vitro. Using the well-established high-density micromass model of chondrogenic differentiation, we first examined the requirement for endogenous Pln synthesis and secretion through the use of Pln-targeted ribozymes in murine C3H10T1/2 embryonic fibroblasts. Second, we examined the ability of the unique N-terminal, HS-bearing Pln domain I (PlnDI) to synergize with exogenous bone morphogenetic protein-2 (BMP-2) to support later stage chondrogenic maturation of cellular condensations. The results provide clear evidence that the function of Pln in late stage chondrogenesis requires Pln biosynthesis and secretion, because 60%-70% reductions in Pln greatly diminish chondrogenic marker expression in micromass culture. Additionally, these data support the idea that while early chondrocyte differentiation can be supported by exogenous HS-decorated PlnDI, efficient late stage PlnDI-supported chondrogenesis requires both BMP-2 and Pln biosynthesis.

Perlecan knockdown in metastatic prostate cancer cells reduces heparin-binding growth factor responses in vitro and tumor growth in vivo

Perlecan (Pln) is a major heparan sulfate proteoglycan (HSPG) of extracellular matrices and bone marrow stroma. Pln, via glycosaminoglycans in domains I and V, acts as a co-receptor for delivery of heparin binding growth factors (HBGFs) that support cancer growth and vascularization. Specifically, glycosaminoglycans bind HBGFs and activate HBGF receptors, including those for FGF-2 and VEGF-A. The contribution of Pln to prostate cancer growth was tested using a ribozyme approach to knockdown Pln expression levels. Transfection into the androgen-independent, bone targeted prostate cancer line, C4-2B, and efficient stable knockdown of Pln was demonstrated by quantitative PCR, immunohistochemistry and immunoblotting. Three individually isolated subclones with 75-80% knockdown in Pln mRNA, protein expression and secretion into ECM were used to study in vitro growth responses to FGF-2 and VEGF-A. While cells with normal Pln levels responded to both HBGFs, knockdown cells responded poorly. All lines responded to serum growth factors and IGF-I. Anchorage-independent growth assays showed reduced colony size and cohesiveness by all Pln deficient subclones compared to parental C4-2B cells. In vivo effects of Pln knockdown were measured by inoculating knockdown and control ribozyme transfected cell lines into athymic mice. A reduced growth rate, smaller tumor size, diminished vascularization and failure to elevate serum PSA characterized mice bearing Pln knockdown C4-2B cells. Poor vascularization correlated with reduced levels of VEGF-A secreted by Pln knockdown lines. We conclude that Pln is an essential ECM component involved in growth responses of metastatic prostate cancer cells to HBGFs deposited in local and metastatic microenvironment.

Decidual differentiation of stromal cells promotes Proprotein Convertase 5/6 expression and lefty processing

Lefty/Ebaf polypeptides, novel members of the TGF-beta superfamily, are involved in endometrial differentiation and embryo implantation. Recently, we showed that, during undisturbed estrous cycle, lefty is present in mouse uterine horn primarily in a precursor form. Here, we show that decidual differentiation of endometrial stroma leads to increased lefty (approximately 3.1- to 3.6-fold in vivo and 5- to 8-fold in vitro) and processing of its precursor primarily to its long form. This event occurs on d 5 of pregnancy, and is paralleled by proprotein convertase (PC)5/6 up-regulation (approximately 6-fold increase for PC5A and 3-fold increase for PC5B) in decidualized uterine horn, independent of embryo implantation. Among the known convertases, only PC5/6A processes lefty to its long form. Taken together, the findings show that decidualized differentiation of stroma, which is a prerequisite for embryo implantation, leads to processing of lefty by PC5/6A.

Differentiation-induced loss of heparan sulfate in human exostosis derived chondrocytes

An exostosis or osteochondroma is an aberrant bony growth occurring next to the growth plate either as an isolated growth abnormality or as part of the Hereditary Multiple Exostosis (HME) syndrome. Mutations in either exostosin 1 (EXT1) or exostosin 2 (EXT2) gene cause the HME syndrome and also some isolated osteochondromas. The EXT1 and EXT2 genes are glycosyltransferases that function as hetero-oligomers in the Golgi to add repeating glycosaminoglycans (GAGs) to heparan sulfate (HS) chains. Previously, we demonstrated that HS is markedly diminished in the exostosis cartilage cap and that the HS proteoglycan, perlecan, has an abnormal distribution in these caps. The present studies were undertaken to evaluate which chondrocyte-specific functions are associated with diminished HS synthesis in human chondrocytes harboring either EXT1 or EXT2 mutations. Systematic evaluation of exostosis cartilage caps and chondrocytes, both in vitro and in vivo, suggests that chondrocyte-specific cell functions account for diminished HS levels. In addition, we provide evidence that perichondrial cells give rise to chondrocytes that clonally expand and develop into an exostosis. Undifferentiated EXT chondrocytes synthesized amounts of HS similar to control chondrocytes; however, EXT chondrocytes displayed very poor survival in vitro under conditions that promote normal chondrocyte differentiation with high efficiency. Collectively, these observations suggest that loss of one copy of either the EXT1 or EXT2 gene product compromises the perichondrial chondrocytes' ability to differentiate normally and to survive in a differentiated state in vitro. In vivo, these compromised responses may lead to abnormal chondrocyte growth, perhaps from a perichondrial stem cell reserve.

Heparan sulfate proteoglycans: key players in cartilage biology

The extracellular matrix (ECM) plays a fundamental role in skeletal patterning and formation of the vertebrate skeleton. This review focuses on the fundamental roles associated with heparan sulfate (HS) proteoglycans in the ECM during cartilage development, which include regulation of gene expression, presentation of growth factors, establishment of morphogen gradients, and modulation of blood homeostasis. The importance of enzymes involved in biosynthesis and assembly of heparan sulfate is also discussed. Finally, the current evidence for functions of individual HS proteoglycans and biosynthetic enzymes based upon human genetic mutation associations with disease and genetic manipulation in transgenic mice is presented. These findings highlight the important role played by HS proteoglycans, such as perlecan, in cartilage development and skeletal growth.

Perlecan domain I promotes fibroblast growth factor 2 delivery in collagen I fibril scaffolds

Perlecan, a heparan sulfate proteoglycan, is widely distributed in developing and adult tissues and plays multiple, important physiological roles. Studies with knockout mouse models indicate that expression of perlecan and heparan sulfate is critical for proper skeletal morphogenesis. Heparan sulfate chains bind and potentiate the activities of various growth factors such as fibroblast growth factor 2 (FGF-2). Previous studies indicate that important biological activities are associated with the heparan sulfate-bearing domain I of perlecan (PlnDI; French et al. J. Bone Miner. Res. 17 , 48, 2002). In the present study, we have used recombinant, glycosaminoglycan-bearing PlnDI to reconstitute three-dimensional scaffolds of collagen I. Collagen I fibrils bound PlnDI much better than native collagen I monomers or heat-denatured collagen I preparations. Heparitinase digestion demonstrated that recombinant PlnDI was substituted with heparan sulfate and that these heparan sulfate chains were critically important not only for efficient integration of PlnDI into scaffolds, but also for FGF-2 binding and retention. PlnDI-containing collagen I scaffolds to which FGF-2 was bound sustained growth of both MG63, an osteoblastic cell line, and human bone marrow stromal cells (hBMSCs) significantly better than scaffolds lacking either PlnDI or FGF-2. Collectively, these studies demonstrate the utility of PlnDI in creating scaffolds that better mimic natural extracellular matrices and better support key biological activities.

Compartmental distinctions in uterine Muc-1 expression during early pregnancy in cynomolgous macaque (Macaca fascicularis) and baboon (Papio anubis)

BACKGROUND

Loss of the transmembrane mucin, Muc-1, is a molecular correlate of the acquisition of uterine receptivity to embryo adhesion in most species examined. In macaques, two distinct adhesion events occur at opposite sides of the uterus. Attachment to the secondary site is delayed relative to the primary site. The aim was to determine if Muc-1 is removed at secondary sites prior to trophoblast attachment.

METHODS

We examined Muc-1 expression in the uteri of cynomolgus macaque and baboon during early implantation by immunocytochemistry.

RESULTS

Luminal epithelia were devoid of Muc-1 at all stages examined at both primary and secondary adhesion sites. Loss of Muc-1 in luminal epithelia was found to be maternally determined, accompanied membrane transformation in both macaque and baboon, and at secondary implantation sites, preceded trophoblast attachment. In contrast, glandular epithelia in pregnant macaques exhibited a temporal and compartmentalized gradient of Muc-1 loss confined to the implantation sites. Glandular epithelia in the pregnant baboon uterus were uniformly negative for Muc-1.

CONCLUSIONS

Restriction of the Muc-1 loss in glandular epithelia to conceptual cycles may reflect the fundamental distinctions among epithelia of the various uterine compartments and the differential modulation of Muc-1 that occurs within these compartments in conceptual and non-conceptual cycles.

Phosphorylated osteopontin promotes migration of human choriocarcinoma cells via a p70 S6 kinase-dependent pathway

This study examined the role of osteopontin (OPN), a phosphorylated secreted glycoprotein, in the promotion of trophoblastic cell migration, an early event in the embryo implantation process. Three human choriocarcinoma cell lines, namely JAR, BeWo, and JEG-3, were treated with variants of OPN differing in the extent of phosphorylation following sequential dephosphorylation with tartrate-resistant acid phosphatase (TRAP), and their migratory response was measured. The highly phosphorylated human milk form of OPN (OPN-1) strongly triggered migration in all three cell lines, whereas the less phosphorylated variants, OPN-2a and OPN-2b, failed to stimulate migration. JAR cell migration in response to OPN-1 was accompanied by a rapid rearrangement of actin filaments to the cellular membrane. Using broad spectrum protein kinase profiling, we identified p70 S6 kinase as a major signal transduction pathway activated by OPN-1 during the migratory response in JAR cells. Activation was blocked completely by rapamycin and LY294002, thus demonstrating that OPN-1-stimulated migration occurs through mTOR and PI3K pathways, respectively. Conversely, PD98059 did not affect the activation of p70 S6 kinase by OPN-1, therefore, this response does not involve the Ras/ MAPK signaling cascade. Together, these data show that the highly phosphorylated human OPN-1 can stimulate trophoblastic cell migration and provides evidence for the involvement of the PI3K/mTOR/p70 S6 kinase pathway in the JAR cells response. Because both OPN and TRAP are expressed in the uterus during early pregnancy, it is conceivable that extracellular phosphatases such as TRAP may modify OPN charge state and thus modulate cell migration.

MUC1 expression in human prostate cancer cell lines and primary tumors

MUC1 expression was evaluated in normal prostate epithelial cells (PrEC), and prostate cancer cell lines in response to dihydrotestosterone (DHT), interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) treatment. Expression of MUC1 core protein was stimulated in PrEC and PC-3 cells after cytokine treatment, but was highly and constitutively expressed by DU-145 cells. MUC1 was not expressed by LNCaP, C4-2 or C4-2B cells under any condition. DHT alone or in combination with cytokines had no effect on MUC1 expression in any cell line tested. Using antibodies capable of detecting all isoforms of MUC1 core protein independent of their glycosylation state, immunohistochemical staining of tissue microarrays containing both nontumor and tumor tissue revealed that only 17% of tumor tissues and 41% of nontumor tissues stained positively for MUC1. Staining patterns in tumor tissue varied from focal apical staining to diffuse cytoplasmic staining. Neither the presence of MUC1 core protein nor its subcellular distribution correlated with Gleason grade. These data indicate that MUC1 is a poor marker of prostate cancer progression. Furthermore, IFN-gamma and TNF-alpha strongly induce MUC1 expression in both normal prostate epithelia and certain prostate tumor cell lines and may exacerbate pathologies associated with MUC1-positive prostate cancers.

Tumor necrosis factor alpha stimulates MUC1 synthesis and ectodomain release in a human uterine epithelial cell line

Regulation of MUC1 expression and removal is a salient feature of embryo implantation, bacterial clearance, and tumor progression. In some species, embryo implantation is accompanied by a transcriptional decline in uterine epithelial expression of MUC1. In other species, MUC1 is locally removed at blastocyst attachment sites, suggesting a proteolytic activity. Previously, we demonstrated that MUC1 is proteolytically released from the surface of a human uterine epithelial cell line, HES, and identified TNFalpha converting enzyme/a disintegrin and metalloprotease 17 as a constitutive and phorbol ester-stimulated MUC1 sheddase. The aims of the current study were to test the ability of soluble factors elevated during the periimplantation interval in vivo to stimulate ectodomain shedding of MUC1 from HES uterine epithelial cells and to characterize the nature of this proteolytic activity(ies). We identified TNFalpha as a prospective endogenous stimulus of MUC1 ectodomain release and of MUC1 and TNFalpha converting enzyme/a disintegrin and metalloprotease 17 expression. Moreover, we established that TNFalpha-stimulated MUC1 shedding occurs independently of increased de novo protein synthesis and demonstrated that the TNFalpha-induced increase in MUC1 gene expression is mediated through the kappaB site in the MUC1 promoter. Finally, we determined that the TNFalpha-sensitive MUC1 sheddase is inhibited by the metalloprotease inhibitor, TNFalpha protease inhibitor (TAPI), and the endogenous tissue inhibitor of metalloprotease-3. Collectively, these studies provide the initial in vitro characterization of a putative physiological stimulus of MUC1 ectodomain release and establish the nature of the metalloproteolytic activity(ies) involved.

Heparanase Degrades Syndecan-1 and Perlecan Heparan Sulfate

Heparanase (HPSE-1) is involved in the degradation of both cell-surface and extracellular matrix (ECM) heparan sulfate (HS) in normal and neoplastic tissues. Degradation of heparan sulfate proteoglycans (HSPG) in mammalian cells is dependent upon the enzymatic activity of HPSE-1, an endo-beta-d-glucuronidase, which cleaves HS using a specific endoglycosidic hydrolysis rather than an eliminase type of action. Elevated HPSE-1 levels are associated with metastatic cancers, directly implicating HPSE-1 in tumor progression. The mechanism of HPSE-1 action to promote tumor progression may involve multiple substrates because HS is present on both cell-surface and ECM proteoglycans. However, the specific targets of HPSE-1 action are not known. Of particular interest is the relationship between HPSE-1 and HSPG, known for their involvement in tumor progression. Syndecan-1, an HSPG, is ubiquitously expressed at the cell surface, and its role in cancer progression may depend upon its degradation. Conversely, another HSPG, perlecan, is an important component of basement membranes and ECM, which can promote invasive behavior. Down-regulation of perlecan expression suppresses the invasive behavior of neoplastic cells in vitro and inhibits tumor growth and angiogenesis in vivo. In this work we demonstrate the following. 1) HPSE-1 cleaves HS present on the cell surface of metastatic melanoma cells. 2) HPSE-1 specifically degrades HS chains of purified syndecan-1 or perlecan HS. 3) Syndecan-1 does not directly inhibit HPSE-1 enzymatic activity. 4) The presence of exogenous syndecan-1 inhibits HPSE-1-mediated invasive behavior of melanoma cells by in vitro chemoinvasion assays. 5) Inhibition of HPSE-1-induced invasion requires syndecan-1 HS chains. These results demonstrate that cell-surface syndecan-1 and ECM perlecan are degradative targets of HPSE-1, and syndecan-1 regulates HPSE-1 biological activity. This suggest that expression of syndecan-1 on the melanoma cell surface and its degradation by HPSE-1 are important determinants in the control of tumor cell invasion and metastasis.

Perlecan Functions in Chondrogenesis: Insights from in vitro and in vivo Models

Perlecan is a large heparan sulfate proteoglycan that is typically found in basal lamina of adult and embryonic tissues. Recent studies have demonstrated that perlecan accumulates impressively during cartilage development and is maintained as the major heparan sulfate proteoglycan of adult cartilage. In vertebrates, perlecan mutations result in skeletal defects. Moreover, in vitro studies indicate that perlecan can stimulate early stages of cartilage differentiation and cooperate with chondrogenic growth factors to promote this process. This short article will summarize these results and propose a model for perlecan function that incorporates these genetic and cell biological findings.

Heparin/heparan sulfate interacting protein plays a role in apoptosis induced by anticancer drugs

Heparin/heparan sulfate interacting protein (HIP, also known as ribosome protein L29) is involved in cell-cell and cell-extracellular matrix interactions and influences cell proliferation, migration and differentiation. In the present study, we investigated the role of HIP in anticancer drug-induced apoptosis. Both colon cancer HCT-116 and HT-29 cells showed dose-dependent down-regulation of HIP expression when treated with sodium butyrate. The down-regulation was negatively correlated with the percentage of apoptotic cells (R = -0.955, P = 0.03 and R = -0.792, P = 0.06 for HCT-116 and HT-29 cells, respectively). The correlation between HIP expression and apoptosis in HCT-116 cells was also evident in the differential expression of HIP in the floating and adherent cell populations. Most apoptotic cells were distributed in the floating population. HIP expression in this population was approximately 30% lower than adherent and untreated control cells. HIP expression in HCT-116 cells was also significantly decreased in parallel with apoptosis after treatment with 50 micro M camptothecin and 20 micro M 5-fluorouracil. This indicates that the down-regulation of HIP may be a general phenomenon in anticancer drug-induced apoptosis. The down-regulation of HIP occurred in the early phase of apoptosis, in parallel with the activation of caspase-3 and the externalization of phosphatidylserine. The functional significance of HIP in apoptosis was shown by knocking down the expression of HIP using small interfering RNA. A 50% reduction in HIP expression was sufficient to increase the percentage of apoptotic cells (from 11 to 20%) and increase the sensitivity of the cells to apoptosis induced by 1 mM butyrate by 60%. These results indicate that HIP may play an important role in anticancer drug-induced apoptosis.

MUC1: a multifunctional cell surface component of reproductive tissue epithelia

MUC1 is a large, transmembrane mucin glycoprotein expressed at the apical surface of a variety of reproductive tract epithelia. Functions attributed to MUC1 include those generally associated with mucins such as lubrication and hydration of cell surfaces as well as protection from microorganisms and degradative enzymes. In addition, MUC1 is an effective inhibitor of both cell-cell and cell-extracellular matrix interactions in both normal and malignant contexts. Moreover, a series of recent studies has shown that the highly conserved cytoplasmic tail of MUC1 interacts specifically with a series of important signal transducing molecules including beta-catenin, Grb2 and erbB family members. MUC1 expression in normal epithelia can be quite dynamic, varying in response to steroid hormone or cytokine influences. Following malignant transformation, MUC1 often becomes highly overexpressed, loses its apical restriction, and displays aberrant glycosylation and altered mRNA splice variants. Regulation of MUC1 expression can occur at the transcriptional level. In addition, post-translational regulation of cell surface expression occurs via the activity of cell surface proteases or "sheddases" that release soluble forms of the large ectodomains. This review will briefly summarize studies of MUC1 expression and function in reproductive tissues with particular emphasis on the uterus. In addition, current knowledge of the mechanisms of MUC1 gene regulation, metabolic processing and potential signal transducing functions will be presented.

Heparan sulfate proteoglycans: Coordinators of multiple signaling pathways during chondrogenesis

Heparan sulfate proteoglycans are abundantly expressed in the pericellular matrix of both developing and mature cartilage. Increasing evidence indicates that the action of numerous chondroregulatory molecules depends on these proteoglycans. This review summarizes the current understanding of the interactions of heparan sulfate chains of cartilage proteoglycans with both soluble and nonsoluble ligands during the process of chondrogenesis. In addition, the consequences of mutating genes encoding heparan sulfate biosynthetic enzymes or heparan sulfate proteoglycan core proteins on cartilage development are discussed.

A heparin binding synthetic peptide from human HIP / RPL29 fails to specifically differentiate between anticoagulantly active and inactive species of heparin

Despite extensive progress in determining structures within heparin and heparan sulfate (Hp/HS) and the discovery of numerous proteinaceous binding partners for Hp/HS so far; the only detailed characterization of a specific protein-glycosaminoglycan interaction is antithrombin III (ATIII) binding to a Hp pentasaccharide containing a unique 3-O-sulfated glucosamine residue. Previously, it was reported from our laboratories that a 16 amino acid synthetic peptide derived from the C-terminus of human HIP/RPL29 (HIP peptide-1) enriched for ATIII-dependent anticoagulant activity, presumably by specifically binding the ATIII pentasaccharide. Herein, we demonstrate that HIP peptide-1 cannot enrich ATIII-dependent anticoagulant activity from a starting pool of porcine intestinal mucosa Hp through a bio-specific interaction. However, a HIP peptide-1 column can be used to enrich for anticoagulantly active Hp from a diverse pool of glycosaminoglycans known as Hp byproducts by a mechanism of nonspecific charge interactions. Thus, HIP peptide-1 cannot recognize Hp via bio-specific interactions but binds glycosaminoglycans by non-specific charge interactions.

Synergistic stimulation of MUC1 expression in normal breast epithelia and breast cancer cells by interferon-gamma and tumor necrosis factor-alpha

The MUC1 gene encodes a transmembrane mucin glycoprotein that is overexpressed in human breast cancers. Persistent stimulation by proinflammatory cytokines may contribute to increased MUC1 transcription by tumor cells. We demonstrate that MUC1 expression in T47D breast cancer cells and normal human mammary epithelial cells (HMEC) is enhanced by tumor necrosis factor-alpha (TNF-alpha) in the presence of interferon-gamma (IFN-gamma). MUC1 responsiveness to these cytokines was modest in T47D cells and robustly induced in HMEC. Transient transfection of T47D cells with mutant MUC1 promoter constructs revealed that a kappaB site at -589/-580 and the STAT-binding element at -503/-495 and were required for cooperative stimulation by TNFalpha and IFN-gamma. Binding of NFkappaB p65 to the MUC1 kappaB site was induced by TNF-alpha treatment, as demonstrated by electrophoretic mobility shift assay. Specific mutation of the kappaB site prevented binding of NFkappaB p65 and blocked TNF-alpha stimulation of MUC1 promoter activity. Collectively, these studies demonstrate synergistic stimulation of MUC1 expression by TNF-alpha and IFN-gamma that is mediated by independent actions of NFkappaB p65 and STAT1alpha upon kappaB and STAT sites, respectively, in the MUC1 promoter. Strong induction of MUC1 expression by these proinflammatory cytokines is clearly evident in normal mammary epithelium. In contrast, breast tumor cells appear to override normal regulatory responses via as yet undefined cis-elements.

Tumor necrosis factor-alpha converting enzyme/ADAM 17 mediates MUC1 shedding

MUC1 clearance from the uterine epithelial cell surface is a prerequisite for the creation of an environment conducive to embryo implantation. In some species, reduced mRNA levels along with metabolic turnover account for loss of MUC1 during the receptive phase throughout the uterine epithelium. In other species, MUC1 is rapidly lost solely at the site of blastocyst attachment, suggesting the action of a protease. Correlative studies also indicate the presence of soluble forms of MUC1 in cell culture supernatants in vitro and in bodily fluids in vivo. To characterize the proteolytic activity mediating MUC1 release, shedding of MUC1 was analyzed in a human uterine epithelial cell line (HES) that abundantly expresses and readily sheds MUC1. MUC1 release was stimulated by phorbol 12-myristate 13-acetate and was markedly inhibited by the synthetic peptide hydroxamate metalloprotease inhibitor, tumor necrosis factor-alpha protease inhibitor (TAPI), as well as by an endogenous inhibitor of matrix metalloproteases, tissue inhibitor of metalloproteases (TIMP)-3. These characteristics along with studies conducted with cell lines genetically deficient in various ADAMs (for a disintegrin and metalloprotease) identified tumor necrosis factor-alpha converting enzyme (TACE)/ADAM 17 as a MUC1 sheddase. Furthermore, both TACE and MUC1 were expressed in human uterine epithelia during the receptive phase, and co-immunoprecipitation experiments revealed a physical interaction between TACE and MUC1 in HES cells. These studies establish a proteolytic mechanism for MUC1 clearance from a human uterine epithelial cell line and identify TACE as a MUC1 sheddase.

Perlecan-stimulated nodules undergo chondrogenic maturation in response to rhBMP-2 treatment in vitro

The heparan sulfate proteoglycan, perlecan, is localized to hypertrophic chondrocytes in the growth plates of long bones. Mice mutants for perlecan display severe cartilage and skeletal defects. Previously, we demonstrated that C3H10T1/2 fibroblasts cultured on perlecan stimulated extensive formation of dense nodules reminiscent of embryonic cartilaginous condensations. These nodules stain intensely with Alcian blue, and antibodies specific for collagen type II and aggrecan; however, nodules do not express collagen type X, a marker of chondrogenic maturation. In this investigation, we tested the hypothesis that addition of rhBMP-2 to perlecan-induced nodules would promote chondrogenic maturation in vitro. C3H10T1/2 fibroblasts were seeded in Lab-Tek chambered "Permanox" slides uncoated or coated with perlecan (B&D, 5 microg/well), at a density of 2 x 10(5) cells/well. The cells were maintained in CMRL-1066 media supplemented with ascorbic acid, citrate, and pyruvate (50 ng/ml). C3H10T1/2 fibroblasts seeded on perlecan-coated wells began to condense and form cell aggregates within 15 min. On the third day postplating, the media was replaced and supplemented with or without rhBMP-2 (50 ng/ml, Genetics Institute). On day 6 of culture, microscopy revealed that rhBMP-2-treated cultures had significantly proliferated; however, untreated cultures had not. By day 12 of culture, confocal microscopy revealed that perlecan-stimulated nodules treated with rhBMP-2 express a late stage marker of chondrogenesis (collagen type X). Morphologically, cells expressing collagen type X in rhBMP-2-treated nodules appear larger in diameter, relative to cells not expressing collagen type X. Cells cultured on plastic and treated with rhBMP-2 did not form nodules, but attached and spread, yielding a high-density monolayer. In response to rhBMP-2 treatment, these cells also express collagen type X. However, the appearance of collagen type X occurs at a later time point relative to the appearance of collagen type X in perlecan-stimulated nodules. Thus, perlecan-stimulated nodules do mature at a faster rate when treated with rhBMP-2 relative to monolayer cells.