Characterization of Circulating Tumor DNA for Genetic Assessment of solid Tumors

Personalized cancer therapy requires characterization of the current status of an individual's cancer, necessitating invasive tumor tissue biopsies at diagnosis, during treatment and at progression. Serial acquisition of solid tumor biopsies during treatment to characterize mutations related to acquired resistance may not be medically feasible. Circulating tumor DNA (ctDNA) in plasma offers a possible noninvasive "real time" tool for tumor characterization, providing accessible genetic biomarkers for cancer diagnosis, prognosis, and response to therapy.

Global analysis of nuclear receptor expression and dysregulation in human osteoarthritic articular cartilage: reduced LXR signaling contributes to catabolic metabolism typical of osteoarthritis

OBJECTIVE

Compare the expression and regulation of nuclear receptors (NRs) in osteoarthritic and normal human articular cartilage.

METHOD

The transcriptional levels of 48 NRs and additional related proteins were measured in mRNA from human articular cartilage from subjects with osteoarthritis (OA) and compared to samples from subjects without OA, using microarrays, individual quantitative reverse transcriptase polymerase chain reaction assays, and a custom human NR TaqMan Low Density Array (TLDA). The functional effect of liver X receptor (LXR) activity in cartilage was studied by measuring proteoglycan (PG) synthesis and degradation in articular cartilage explant cultures following treatment with the synthetic LXR agonist T0901317.

RESULTS

Thirty-one of 48 NRs analyzed by TLDA were found to be measurably expressed in human articular cartilage; 23 of these 31 NRs showed significantly altered expression in OA vs unaffected cartilage. Among these, LXRalpha and LXRbeta, and their heterodimeric partners retinoid X receptor (RXR)alpha and RXRbeta were all expressed at significantly lower levels in OA cartilage, as were LXR target genes ABCG1 and apolipoproteins D and E. Addition of LXR agonist to human OA articular chondrocytes and to cartilage explant cultures resulted in activation of LXR-mediated transcription and significant reduction of both basal and interleukin (IL)-1-mediated PG degradation.

CONCLUSIONS

Articular cartilage expresses a substantial number of NRs, and a large proportion of the expressed NRs are dysregulated in OA. In particular, LXR signaling in OA articular cartilage is impaired, and stimulation of LXR transcriptional activity can counteract the catabolic effects of IL-1. We conclude that LXR agonism may be a possible therapeutic option for OA.

In vitro allergen challenge of peripheral blood induces differential gene expression in mononuclear cells of asthmatic patients: inhibition of cytosolic phospholipase A2alpha overcomes the asthma-associated response

BACKGROUND

Existing treatments for asthma are not effective in all patients and disease exacerbations are common, highlighting the need for increased understanding of disease mechanisms and novel treatment strategies. The leukotriene pathway including the enzyme responsible for arachidonic acid release from cellular phospholipids, cPLA(2)alpha, is a major contributor to asthmatic responses and an attractive target in asthma therapies.

OBJECTIVE

The study reported here investigates (a) the differential effects of in vitro exposure of peripheral blood mononuclear cells (PBMCs) to allergen between asthma and healthy subjects, and (b) the contribution of cPLA(2)alpha to these differences in gene expression.

METHODS

In vitro responses of asthma (N=26) and healthy (N=11) subject PBMC samples to allergen stimulation in the presence and absence of cPLA(2)alpha inhibition or 5-lipoxygenase inhibition were compared at the gene expression level using oligonucleotide arrays and at the protein level using ELISA.

RESULTS

Subject samples within both asthma and healthy groups showed allergen-dependent cytokine production and allergen-dependent gene expression changes, although transcriptional profiling identified 153 genes that were modulated significantly differently by allergen between asthma and healthy subjects. Among these were genes previously associated with asthma, but the majority (about 80%) have not previously been associated with asthma.

CONCLUSIONS

Transcriptional profiling elucidated novel gene expression differences between the asthmatic and healthy subject samples. Although 5-lipoxygenase inhibition did not significantly affect allergen-modulated gene expression, the inhibition of cPLA(2)alpha activity affected many of the allergen-dependent, asthma-associated gene expression changes.

Gene expression analysis in a murine model of allergic asthma reveals overlapping disease and therapy dependent pathways in the lung

Accumulating evidence in animal models and human asthma support a central role for IL-13 signaling in disease pathogenesis. In order to identify asthma and therapy associated genes, global transcriptional changes were monitored in mouse lung following antigen challenge (ovalbumin (OVA)), either alone or in the presence of a soluble IL-13 antagonist. Changes in whole lung gene expression after instillation of mIL-13 were also measured both in wild type and STAT6 deficient mice. A striking overlap in the gene expression profiles induced by either OVA challenge or mIL-13 was observed, further strengthening the relationship of IL-13 signaling to asthma. Consistent with results from functional studies, a subset of the OVA-induced gene expression was significantly inhibited by a soluble IL-13 antagonist while IL-13-modulated gene expression was completely attenuated in the absence of STAT6-mediated signaling. Results from these experiments greatly expand our understanding of asthma and provide novel molecular targets for therapy and potential biomarkers of IL-13 antagonism.

The therapeutic utility of Interleukin-11 in the treatment of inflammatory disease

Interleukin-11 (IL-11) is a pleiotropic cytokine that exhibits anti-inflammatory and mucosal protective effects in a variety of animal models of acute and chronic inflammation, such as mucositis, inflammatory bowel disease and autoimmune joint disease. This reduction in inflammation and epithelial damage is mediated in part through effects of recombinant human (rh) IL-11 on macrophage effector function and epithelial cell growth. In vitro studies indicate that rhIL-11 inhibits tumour necrosis factor (TNF)-alpha, IL-1beta, IL-12, IL-6, and nitric oxide production from activated macrophages. Analysis of the effects of rhIL-11 on transcription factors that activate pro-inflammatory cytokines demonstrate that the level of induced nuclear factor kappa B (NF-kappaB) binding activity in the nucleus of rhIL-11-treated peritoneal macrophages is significantly reduced. Studies of normal intestinal epithelial cells indicate that rhIL-11 reduces the rate of cellular proliferation. Analysis of cell-cycle progression demonstrates that growth inhibition of epithelial cells by rhIL-11 correlates with delayed entry into S phase and suppression of pRB phosphorylation. IL-11 also protects intestinal crypt stem cells from radiation- or chemotherapy-induced insults. Such immunomodulatory and epithelial activities may contribute to the protective effects of this cytokine and support the clinical utility of rhIL-11 in the treatment of mucositis, as well as a variety of chronic inflammatory diseases, such as Crohn's disease and rheumatoid arthritis.

Mechanistic toxicogenomic analysis of WAY-144122 administration in Sprague–Dawley rats

Application of global gene expression analysis in the study of mechanisms of toxicity could provide a more comprehensive interpretation of the molecular basis of drug action. WAY-144122 has pharmacological activity against several targets improving insulin responsiveness and favorably altering lipid profiles. Normal rats treated with suprapharmacological doses of WAY-144122 for 28 days exhibited drug-related effects in the liver and ovary. To determine the molecular mechanism underlying these effects, we employed global gene expression profiling to measure RNA levels in these target organs obtained from WAY-144122-treated rats administered test article for 1, 3, 7, and 14 days. Genes altered in expression by WAY-144122 were functionally categorized and related to their biological activity. In the liver, WAY-144122 caused a widespread up-regulation of genes involved in lipid mobilization, peroxisomal proliferation, and fatty acid beta-oxidation. In the ovary, we observed reduced expression of genes encoding luteinizing hormone receptor, follistatin, and enzymes in the estradiol synthesis pathway. Transcriptional changes in both organs precede histopathological effects. Profiling analysis allowed us to formulate hypotheses for molecular mechanisms underlying the physiological observations. In the liver, transcriptional changes suggest that WAY-144122 induced increased metabolic activity and peroxisomal proliferation resulting in increased liver weight and hepatocellular hypertrophy. We propose decreased estradiol synthesis as the underlying mechanism for the observed follicular atrophy in the ovary. Importantly, in this study, we have identified potential molecular mechanisms of drug effect in expression profiles before observation of physiological changes.

Pharmacogenomic analysis of rhIL-11 treatment in the HLA-B27 rat model of inflammatory bowel disease

Recombinant human interleukin-11 (rhIL-11) reduces the clinical signs and histological lesions of inflammatory bowel disease (IBD) in transgenic rats expressing the human major histocompatability complex (MHC) class I allele, HLA-B27. To elucidate the pharmacogenomic effects of rhIL-11 in this model, we examined the global gene expression pattern in inflamed colonic tissue before and following rhIL-11 treatment using oligonucleotide microarrays. In total, 175 disease-related genes were identified. Increased expression of genes involved in antigen presentation, cell death and inflammation, and decreased expression of metabolic genes was associated with disease. A total of 27 disease-related genes returned to normal expression levels following rhIL-11 treatment including the MHC class II gene RT1-DMbeta. rhIL-11 induced the expression of four intestinal epithelial growth factors. These gene expression patterns indicate that treatment of inflammatory bowel disease with rhIL-11 affects class II antigen processing and colonic epithelial cell proliferation and metabolism.

Molecular classification of psoriasis disease-associated genes through pharmacogenomic expression profiling

Psoriasis is recognized as the most common T cell-mediated inflammatory disease in humans. Genetic linkage to as many as six distinct disease loci has been established but the molecular etiology and genetics remain unknown. To begin to identify psoriasis disease-related genes and construct in vivo pathways of the inflammatory process, a genome-wide expression screen of multiple psoriasis patients was undertaken. A comprehensive list of 159 genes that define psoriasis in molecular terms was generated; numerous genes in this set mapped to six different disease-associated loci. To further interpret the functional role of this gene set in the disease process, a longitudinal pharmacogenomic study was initiated to understand how expression levels of these transcripts are altered following patient treatment with therapeutic agents that antagonize calcineurin or NF-KB pathways. Transcript levels for a subset of these 159 genes changed significantly in those patients who responded to therapy and many of the changes preceded clinical improvement. The disease-related gene map provides new insights into the pathogenesis of psoriasis, wound healing and cellular-immune reactions occurring in human skin as well as other T cell-mediated autoimmune diseases. In addition, it provides a set of candidate genes that may serve as novel therapeutic intervention points as well as surrogate and predictive markers of treatment outcome.

Protective effect of rhIL-11 in a murine model of acetaminophen-induced hepatotoxicity

Acetaminophen intoxication results in hepatotoxicity associated with increased serum concentrations of hepatocellular leakage enzymes such as aspartate aminotransferase, lactate dehydrogenase, and alanine aminotransferase, centrilobular degeneration and necrosis, and activation of Kupffer cells. Recombinant human Interleukin-11 (rhIL-11) downregulates the production of proinflammatory mediators from activated macrophages and has direct effects on hepatocyte gene expression. Based on these biological activities of rhIL-11, the effect of pretreatment with rhIL-11 in a murine model of acetaminophen-induced hepatotoxicity was examined. Administration of 500 microg/kg acetaminophen to B6C3F1 mice resulted in progressive hepatotoxicity as demonstrated by elevated serum concentrations of hepatocellular leakage enzymes and TNFalpha and histopathology. Pretreatment with 250 or 500 microg/kg of subcutaneously administered rhIL-11 2 hours before acetaminophen administration reduced serum concentrations of hepatocellular leakage enzymes and TNFalpha by 40-50%. This was associated with a statistically significant decrease in mean severity score for centrilobular hemorrhage and necrosis from grade 3 to grade 2 for rhIL-11-treated animals compared to vehicle. These results indicate that treatment with rhIL-11 has a protective effect in a model of acetaminophen-induced liver damage.

Interleukin-11 modulates Th1/Th2 cytokine production from activated CD4+ T cells

Recombinant human interleukin-11 (rHuIL-11) is a pleiotropic cytokine with effects on multiple cell types. rHuIL-11 reduces activated macrophage activity and downregulates production of proinflammatory mediators, such as tumor necrosis factor-alpha (TNF-alpha) and nitric oxide (NO). In vitro and in vivo, rHuIL-11 inhibits production of key immunostimulatory cytokines, including IL-12 and interferon-gamma (IFN-gamma). rHuIL-11 has recently demonstrated immunomodulatory activity to downregulate IFN-gamma production, increase IL-4 production, and reduce inflammatory tissue injury in a human psoriasis clinical trial. The cellular mechanisms of these effects are not fully elucidated. We demonstrate here that expression of gp130 and IL-11 receptor (IL-11R) alpha mRNA, components of the IL-11R complex, are detected in human and murine CD4(+) and CD8(+) lymphocytes, suggesting that rHuIL-11 can directly interact with T cells. In a cell culture model of murine T cell differentiation, rHuIL-11 acts to inhibit IL-2 production as well as IL-12-induced IFN-gamma production and enhances IL-4 and IL-10 production. rHuIL-11 had no effect on T cell proliferation. The ability of rHuIL-11 to modulate cytokine production from activated CD4(+) T cells provides a mechanism through which rHuIL-11 may ameliorate such inflammatory diseases as psoriasis.

Subcutaneous or oral administration of rhIL-11 modulated the contact hypersensitivity response

Recombinant human interleukin 11 (rhIL-11) is a multifunctional cytokine with immunomodulatory activity on both T cells and macrophages. The effects of rhIL-11 in a murine model of contact hypersensitivity (CHS) response have been studied. The CHS response is a T cell-mediated response directed against chemically modified self-proteins following epidermal exposure to haptens. CHS is generated in two phases. The sensitization phase involves dermal dendritic cell recognition of haptenized proteins and antigen presentation. The effector phase involves T cell recognition and activation. In mice sensitized with oxazolone, CHS was induced by secondary challenge to the right ear and measured by ear swelling 24 h later. rhIL-11 significantly suppressed CHS as measured by ear swelling and tissue myeloperoxidase activity when injected subcutaneously for 5 days from the day of sensitization or when administered only on the day before and the day of challenge, but was not effective when administered prior to or on the day of sensitization. These results indicate that subcutaneously administered rhIL-11 may modulate the effector phase of CHS. Administration of rhIL-11 as an oral gavage prior to sensitization also reduced CHS. However oral administration of rhIL-11 after sensitization had no effect. These results suggest that orally and subcutaneously administered rhIL-11 may act through different mechanisms to affect CHS.

Defining mechanisms of action of interleukin-11 on the progression of radiation-induced oral mucositis in hamsters

Oral ulcerative mucositis is a common toxicity associated with drug and radiation therapy for cancer. It impacts on quality of life and economic outcomes, as well as morbidity and mortality. Mucositis is often associated with dose limitations for chemotherapy or is a cause for dose interruption for radiation. The complexity of mucositis as a biological process has only been recently appreciated. It has been suggested that the condition represents a sequential interaction of oral mucosal cells and tissues, pro-inflammatory cytokines and local factors such as saliva and the oral microbiota. The recognition that the pathophysiology of mucositis is a multifactorial process was partially suggested by the observation that interleukin-11 (IL-11), a pleotropic cytokine, favorably altered the course of chemotherapy-induced mucositis in an animal model. In the current study, we evaluated a series of biologic and morphologic outcomes to determine their roles and sequence in the development of experimental radiation-induced mucositis and to evaluate the effects of IL-11 in attenuating them. Our results suggest that IL-11 favorably modulates acute radiation-induced mucositis by attenuating pro-inflammatory cytokine expression. Data are also presented which help define the pathobiological sequence of mucositis.

IL-12-Dependent enhancement of CTL response to weak class I-restricted peptide immunogens requires coimmunization with T helper cell immunogens

The effect of in vivo administration of rmIL-12 on the CTL response to immunization with a weakly immunogenic class I-restricted peptide emulsified in incomplete Freund's adjuvant was investigated. In the absence of IL-12, peptide-specific CTL responses were significantly greater following coimmunization with class I-restricted peptide and T helper cell antigens than following immunization with the class I-restricted peptide alone. IL-12-dependent enhancement of the CTL response to peptide immunization was demonstrated in the presence of, but not in the absence of, coimmunization with T helper cell antigen. These findings indicate that IL-12 enhancement of the CTL response to weak class I-restricted immunogens is T helper cell dependent. Treatment with rmIL-12 also enhanced the CTL response to immunization with cDNA encoding both CTL and T helper cell epitopes. These findings are relevant to the design of vaccines containing tumor-associated class I-restricted peptides currently being tested as an immunotherapy for cancer patients.

A CTL assay requiring only 150 microliter of mouse blood

In this paper, we present a method for measuring antigen specific cytotoxic T lymphocyte (CTL) activity from individual mouse peripheral blood samples without animal sacrifice. Peripheral blood cells are stimulated in vitro with a cocktail of antigen, cytokines, costimulatory molecules and irradiated feeder cells resulting, 7 days later, in a readily detectable antigen specific signal from a well plated under limiting dilution conditions. This highly sensitive and antigen specific assay is more efficient than conventional CTL assays and thus increases the number of mice that can be tested in a single assay. Since blood samples can be assayed from an individual mouse at multiple times during the course of an in vivo study, the assay can facilitate and strengthen correlative studies on CTL responses and in vivo results.

Interleukin-11 therapy selectively downregulates type I cytokine proinflammatory pathways in psoriasis lesions

Psoriasis is a chronic inflammatory skin disease in which epidermal hyperplasia results from skin infiltration by type I T lymphocytes and release of associated cytokines. A multifunctional cytokine, rhIL-11, modulates macrophage and type I T-lymphocyte function in cell culture and shows anti-inflammatory activity in animal models. We are testing subcutaneous delivery of rhIL-11 to patients with psoriasis in a phase 1 open-label dose-escalation clinical trial. Tissue was obtained from lesional and uninvolved skin before and during treatment with rhIL-11 and was examined by histology/immunohistochemistry and quantitative RT-PCR. Expression of over 35 genes was examined in all patients, and multiple genetic markers of psoriasis were identified. Expression of numerous proinflammatory genes was elevated in psoriatic tissue compared with nonlesional skin. Seven of 12 patients responded well to rhIL-11 treatment. Amelioration of disease by rhIL-11, as shown by reduced keratinocyte proliferation and cutaneous inflammation, was associated with decreased expression of products of disease-related genes, including K16, iNOS, IFN-gamma, IL-8, IL-12, TNF-alpha, IL-1beta, and CD8, and with increased expression of endogenous IL-11. We believe that this is the first study in humans to indicate that type I cytokines can be selectively suppressed by an exogenous immune-modifying therapy. The study highlights the utility of pharmacogenomic monitoring to track patient responsiveness and to elucidate anti-inflammatory mechanisms.

Interleukin-11 reduces T-cell-dependent experimental liver injury in mice

Recombinant human interleukin-11 (rhIL-11) is a multifunctional cytokine that can reduce inflammation through the downregulation of multiple pro-inflammatory mediators from activated macrophages. rhIL-11 also inhibits production of several immunostimulatory cytokines such as IL-12 and interferon gamma (IFN-gamma) and has shown biological activity in multiple animal models of inflammatory disease consistent with immunomodulatory effects on macrophages and T cells. To further elucidate the anti-inflammatory activity of rhIL-11 in vivo, the effect of rhIL-11 in a model of Concanavalin A (Con-A)-induced T-cell-mediated hepatotoxicity was examined. Administration of a single dose of rhIL-11 before Con-A administration reduced centrilobular liver necrosis and enhanced survival. A dose-dependent reduction in serum levels of liver enzymes, tumor necrosis factor alpha (TNF-alpha), and IFN-gamma corresponded with this amelioration of liver damage. No significant change in infiltrating lymphocyte populations in the liver was observed following rhIL-11 treatment. Taken together, these results indicate that rhIL-11 ameliorates T-cell-mediated hepatic injury and suggests its therapeutic potential to treat inflammatory liver disease.

Immune response enhancement by in vivo administration of B7.2Ig, a soluble costimulatory protein

The identification of both class I- and class II-restricted tumor-associated peptides recognized by T cells has led to the test of these peptides as immunogens in experimental immunotherapy for cancer patients. However, optimal T cell activation requires signaling both through the T cell receptor for antigen and through costimulatory pathways. B7.1 and B7.2 are powerful costimulatory molecules expressed on the surface of antigen-presenting cells. Using a mouse model, we have sought to optimize costimulatory signals during antipeptide responses by administering a soluble form of B7.2 at the time of peptide immunization. Administration of B7. 2Ig fusion protein significantly enhanced T helper cell and CTL responses. These findings suggest that soluble forms of human B7.2 protein may provide a straightforward and practical method of supplying optimal costimulation during clinical immunotherapy.

Hematopoietic, immunomodulatory and epithelial effects of interleukin-11

Interleukin 11 (IL-11) is a pleiotropic cytokine with biological activities on many different cell types. Recombinant human IL-11 (rhIL-11) is produced by recombinant DNA technology in Escherichia coli. Both in vitro and in vivo, rhIL-11 has shown effects on multiple hematopoietic cell types. Its predominant in vivo hematopoietic activity is the stimulation of peripheral platelet counts in both normal and myelosuppressed animals. This activity is mediated through effects on both early and late progenitor cells to stimulate megakaryocyte differentiation and maturation. rhIL-11 has been approved for the treatment of chemotherapy-induced thrombocytopenia. The hematopoietic effects of rhIL-11 are most likely direct effects on progenitor cells and megakaryocytes in combination with other cytokines or growth factors. rhIL-11 also induces secretion of acute phase proteins (ferritin, haptoglobin, C-reactive protein, and fibrinogen) from the liver. The induction of heme oxidase and inhibition of several P450 oxidases have been reported from in vitro studies. In vivo, rhIL-11 treatment decreases sodium excretion by the kidney by an unknown mechanism and induces hemodilution. rhIL-11 also exhibits anti-inflammatory effects in a variety of animal models of acute and chronic inflammation, including inflammatory bowel disease, inflammatory skin disease, autoimmune joint disease, and various infection-endotoxemia syndromes. rhIL-11 has trophic effects on non-transformed intestinal epithelium under conditions of mucosal damage. The mechanism of the anti-inflammatory activity of rhIL-11 has been extensively studied. rhIL-11 directly affects macrophage and T cell effector function. rhIL-11 inhibits tumor necrosis factor-alpha (TNF alpha), interleukin 1beta (IL-1beta), interleukin 12 (IL-12), interleukin 6 (IL-6), and nitric oxide (NO) production from activated macrophages in vitro. The inhibition of cytokine production was associated with inhibition of nuclear translocation of the transcription factor, nuclear factor kappa B (NF-kappaB). The block to NF-kappaB nuclear translocation correlates with the ability of rhIL-11 to maintain or enhance production of the inhibitors of NF-kappaB, IkappaB-alpha and IkappaB-beta. In addition to effects on macrophages, rhIL-11 also reduces CD4+ T cell production of Th1 cytokines, such as IFN gamma induced by IL-12, while enhancing Th2 cytokine production. rhIL-11 also blocks IFN gamma production in vivo. The molecular effects of rhIL-11 have also been studied in a clinical trial. Molecular analysis of skin biopsies of patients with psoriasis before and during rhIL-11 treatment demonstrates a decrease in mRNA levels of TNF alpha, IFN gamma and iNOS. These activities suggest that in addition to its thrombopoietic clinical use, rhIL-11 may also be valuable in the treatment of inflammatory diseases. The clinical utility of the anti-inflammatory properties of rhIL-11 is being investigated in patients with Crohn's disease, psoriasis and rheumatoid arthritis. These diseases are believed to be initiated and maintained by activated CD4+ Th1 cells in conjunction with activated macrophages.

von Willebrand factor elevates plasma factor VIII without induction of factor VIII messenger RNA in the liver

Factor VIII and von Willebrand factor (vWF) circulate in the plasma as a noncovalent protein complex. Circulating levels of factor VIII are coordinately regulated with circulating levels of vWF in which the ratio is maintained at 1 molecule of factor VIII for 50 to 100 vWF subunits. Infusion of vWF into vWF-deficient animal models and human patients yields a secondary increase in circulating levels of factor VIII. We have studied the mechanism of the secondary rise in factor VIII in a porcine model of vWF deficiency. On infusion of vWF into a vWF-deficient pig there was an approximately fivefold increase in circulating factor VIII activity. Liver biopsies were taken pre- and post-vWF infusion for isolation of total messenger RNA (mRNA). Factor VIII-specific mRNA was measured by an RNAse protection assay. The results showed no difference in the liver-specific factor VIII mRNA on vWF infusion. These results indicate that the secondary rise in factor VIII levels in response to exogenous vWF infusion is not dependent on increased steady-state levels of factor VIII mRNA in the liver.

Molecular effects of recombinant human interleukin-11 in the HLA-B27 rat model of inflammatory bowel disease

Recombinant human interleukin-11 (rhIL-11) is a pleiotropic cytokine with effects on multiple cell types. In addition to thrombopoietic activity, rhIL-11 has demonstrated anti-inflammatory activity in vitro and in vivo. rhIL-11 treatment reduces clinical signs and histologic lesions of colitis in transgenic rats expressing the human major histocompatibility complex (MHC) Class I allele, HLA-B27. We have investigated the effects of rhIL-11 at the molecular and cellular level in this model of inflammatory bowel disease. RT-PCR analysis of colonic RNA revealed that treatment with rhIL-11 down-regulated expression of proinflammatory cytokines including TNF-alpha, IL-1beta, and IFN-gamma. rhIL-11 also reduced the level of myeloperoxidase activity in the cecum indicating reduced inflammation. After stimulation in vitro with anti-CD3 antibody, spleen cell cultures derived from rhIL-11-treated rats produced less IFN-gamma, TNF-alpha, and IL-2 than cultures derived from vehicle-treated rats. These molecular and cellular effects correlated with amelioration of disease as measured by stool character and histologic lesion scores. These findings suggest that rhIL-11 acts to reduce inflammation through modulation of multiple proinflammatory mediators including products of activated T cells. This study has identified pharmacodynamic markers of rhIL-11 anti-inflammatory activity in vivo and supports rhIL-11 therapy to treat inflammatory bowel disease.

Recombinant human interleukin-11 does not affect functions of purified human neutrophils in vitro

Recombinant human interleukin-11 (rHu-IL-11) is a multifunctional cytokine with thrombopoietic activity and demonstrated clinical efficacy in treating chemotherapy-induced thrombocytopenia. rHu-IL-11 also exhibits anti-inflammatory activity and is currently in clinical trials for the treatment of several inflammatory diseases. As neutrophils are involved in both innate immunity and an acute inflammatory response, the effect of rHU-IL-11 on the function of human peripheral blood neutrophils in vitro was examined. rHu-IL-11 was not cytotoxic and did not induce superoxide anion production or the release of granular enzymes from resting neutrophils. Phagocytosis and chemotaxis were unaffected. rHu-IL-11 treatment did not block the response of neutrophils to stimulation. Pretreatment with rHu-IL-11 did not reduce production of IL-8 following activation with lipopolysaccharide (LPS) or zymosan A particles. Pretreatment with rHu-IL-11 did not affect the release of lysozyme and beta-glucuronidase in response to A23187 or PMA-stimulated production of superoxide anion. These results indicate that rHu-IL-11 does not directly modulate key functions of neutrophils in vitro.

IL-11 regulates macrophage effector function through the inhibition of nuclear factor-kappaB

Recombinant human IL-11 (rhIL-11) is an anti-inflammatory cytokine that can reduce the production of inflammatory mediators such as TNF-alpha, IL-1beta, IL-12, IL-6, and nitric oxide. Inhibition of proinflammatory cytokine production from activated macrophages was associated with a reduction in the levels of LPS-induced TNF-alpha, IL-1beta, IL-6, and IL-12 p40 mRNA. Analysis of rhIL-11 effects on transcription factors that activate proinflammatory cytokines demonstrated that the level of LPS-induced NF-kappaB binding activity in the nucleus of rhIL-11-treated peritoneal macrophages was significantly reduced. The block to NF-kappaB nuclear translocation correlated with the ability of rhIL-11 to maintain or increase protein levels of the inhibitors of NF-kappaB, IkappaB-alpha, and IkappaB-beta following LPS treatment. Furthermore, rhIL-11-treatment of LPS macrophages resulted in significant elevation of IkappaB-alpha and IkappaB-beta mRNA levels. These results suggest that the anti-inflammatory activity of rhIL-11 is mediated in part by inhibition of NF-kappaB-dependent transcriptional activation. Furthermore, these studies demonstrate for the first time the regulation of IkappaB-beta by an anti-inflammatory cytokine. Given the finding that inappropriate activation of NF-kappaB contributes to multiple inflammatory conditions, the ability of rhIL-11 to inhibit the binding activity of this pleiotropic transcription factor indicates that rhIL-11 has therapeutic potential in a wide range of diseases.

IL-11 regulates macrophage effector function through the inhibition of nuclear factor-kappaB

Recombinant human IL-11 (rhIL-11) is an anti-inflammatory cytokine that can reduce the production of inflammatory mediators such as TNF-alpha, IL-1beta, IL-12, IL-6, and nitric oxide. Inhibition of proinflammatory cytokine production from activated macrophages was associated with a reduction in the levels of LPS-induced TNF-alpha, IL-1beta, IL-6, and IL-12 p40 mRNA. Analysis of rhIL-11 effects on transcription factors that activate proinflammatory cytokines demonstrated that the level of LPS-induced NF-kappaB binding activity in the nucleus of rhIL-11-treated peritoneal macrophages was significantly reduced. The block to NF-kappaB nuclear translocation correlated with the ability of rhIL-11 to maintain or increase protein levels of the inhibitors of NF-kappaB, IkappaB-alpha, and IkappaB-beta following LPS treatment. Furthermore, rhIL-11-treatment of LPS macrophages resulted in significant elevation of IkappaB-alpha and IkappaB-beta mRNA levels. These results suggest that the anti-inflammatory activity of rhIL-11 is mediated in part by inhibition of NF-kappaB-dependent transcriptional activation. Furthermore, these studies demonstrate for the first time the regulation of IkappaB-beta by an anti-inflammatory cytokine. Given the finding that inappropriate activation of NF-kappaB contributes to multiple inflammatory conditions, the ability of rhIL-11 to inhibit the binding activity of this pleiotropic transcription factor indicates that rhIL-11 has therapeutic potential in a wide range of diseases.

Multiple control elements mediate activation of the murine and human interleukin 12 p40 promoters: evidence of functional synergy between C/EBP and Rel proteins

Interleukin 12 (IL-12) is a heterodimeric cytokine whose activity is critical for T-helper 1 responses. The gene for the IL-12 p40 subunit is expressed in macrophages following induction by bacterial products, and its expression is augmented by gamma interferon. In this study, we performed a functional analysis of the murine and human p40 promoters in the murine macrophage cell line RAW 264.7. Transcription from the murine p40 promoter was strongly induced by lipopolysaccharide and heat-killed Listeria monocytogenes (HKLM), but promoter activity was not enhanced by gamma interferon. Multiple cis-acting elements involved in activated transcription were identified through an extensive mutant analysis. The most critical element, whose activity is conserved in mice and humans, is located between positions -96 and -88 relative to the murine transcription start site. This element exhibits functional synergy with a previously described NF-kappaB half-site which interacts with Rel proteins. DNase I footprinting and electrophoretic mobility shift assays demonstrated that C/EBP proteins interact with the critical element, but in nuclear extracts, cooperative binding of C/EBP and Rel proteins to their respective sites was not observed. Interestingly, promoter activity was induced by HKLM in the presence of cycloheximide, consistent with induction by posttranslational mechanisms. The results suggest that C/EBP and Rel proteins play important roles in the activation of IL-12 p40 transcription by bacteria. However, many complex interactions will need to be clarified to fully understand p40 regulation.

Immunoglobulin binding protein (BiP) function is required to protect cells from endoplasmic reticulum stress but is not required for the secretion of selective proteins

BiP/GRP78 is a lumenal stress protein of the endoplasmic reticulum (ER) that interacts with polypeptide folding intermediates transiting the secretory compartment. We have studied the secretion and the stress response in Chinese hamster ovary (CHO) cells that overexpress either wild-type immunoglobulin binding protein (BiP) or a BiP deletion molecule (residues 175-201) that can bind peptides and ATP but is defective in ATP hydrolysis and concomitant peptide release. Overexpressed wild-type BiP was localized to the ER and unique vesicles within the nucleus, whereas overexpressed ATPase-defective BiP was localized to the ER and cytoplasmic vesicles but was absent from the nucleus. Compared with wild-type CHO cells, overexpression of ATPase-defective BiP prevented secretion of factor VIII, a coagulation factor that extensively binds BiP in the lumen of the ER. Under these conditions factor VIII was stably associated with the ATPase-defective BiP. In contrast, the secretion of monocyte/macrophage colony stimulating factor, a protein that is not detected in association with BiP, was not affected by overexpression of ATPase-defective BiP. These results show that BiP function is not required for secretion of some proteins and suggest that some proteins do not interact with BiP upon transport through the ER. The presence of unfolded protein in the ER induces transcription of BiP and also elicits a general inhibition of protein synthesis. Overexpression of wild-type BiP prevented the stress-mediated transcriptional induction of BiP in response to either calcium ionophore A23187 treatment or tunicamycin treatment. In contrast, overexpression of ATPase-defective BiP did not prevent the stress induction of BiP, showing that the ATPase activity is required to inhibit transcriptional induction. Overexpression of wild-type BiP, but not ATPase-defective BiP, increased survival of cells treated with A23187. The increased survival mediated by overexpressed wild-type BiP correlated with reduced translation inhibition in response to the stress condition. These results indicate that overexpressed BiP alleviated the stress in the ER to prevent BiP transcriptional induction and permit continued translation of cellular mRNAs.

Recombinant human IL-11 attenuates the inflammatory response through down-regulation of proinflammatory cytokine release and nitric oxide production

To elucidate the molecular mechanisms regulating the anti-inflammatory activities of recombinant human (rh)IL-11, the ability of rhIL-11 to reduce serum levels of inflammatory mediators such as TNF-alpha, IL-1beta, IL-12, and IFN-gamma in LPS-treated mice and to down-regulate macrophage function in culture was investigated. In a mouse model of endotoxemia, pretreatment with rhIL-11 blocked LPS-induced elevation of TNF-alpha, IL-1beta, and IFN-gamma serum levels, but had no effect on IL-12 p40, IL-6, or IL-10 serum levels. The effects of rhIL-11 on the production of inflammatory mediators in vivo may occur in part through direct interactions with macrophages. rhIL-11 pretreatment of thioglycollate-elicited peritoneal macrophages resulted in greater than 60% inhibition of LPS-induced production of TNF-alpha, IL-1beta, IL-12 p40, and nitric oxide. The activity of rhIL-11 was not mediated through induction of IL-10, IL-6, or TGF-beta1. These results indicate that the ability of rhIL-11 to modulate the inflammatory response is not dependent on known anti-inflammatory cytokines and substantiate a role for this cytokine in the attenuation of inflammatory conditions.

Recombinant human IL-11 attenuates the inflammatory response through down-regulation of proinflammatory cytokine release and nitric oxide production

To elucidate the molecular mechanisms regulating the anti-inflammatory activities of recombinant human (rh)IL-11, the ability of rhIL-11 to reduce serum levels of inflammatory mediators such as TNF-alpha, IL-1beta, IL-12, and IFN-gamma in LPS-treated mice and to down-regulate macrophage function in culture was investigated. In a mouse model of endotoxemia, pretreatment with rhIL-11 blocked LPS-induced elevation of TNF-alpha, IL-1beta, and IFN-gamma serum levels, but had no effect on IL-12 p40, IL-6, or IL-10 serum levels. The effects of rhIL-11 on the production of inflammatory mediators in vivo may occur in part through direct interactions with macrophages. rhIL-11 pretreatment of thioglycollate-elicited peritoneal macrophages resulted in greater than 60% inhibition of LPS-induced production of TNF-alpha, IL-1beta, IL-12 p40, and nitric oxide. The activity of rhIL-11 was not mediated through induction of IL-10, IL-6, or TGF-beta1. These results indicate that the ability of rhIL-11 to modulate the inflammatory response is not dependent on known anti-inflammatory cytokines and substantiate a role for this cytokine in the attenuation of inflammatory conditions.

Interleukin-11 induces intestinal epithelial cell growth arrest through effects on retinoblastoma protein phosphorylation

Recombinant human (rh) interleukin (IL)-11 has been shown to reduce gastrointestinal mucosal injury after chemotherapy or irradiation in several animal models. As reduction of cellular proliferation can be cytoprotective, we have examined the effect of rhIL-11 compared with transforming growth factor (TGF)-beta 1 on the proliferation and cell cycle progression of a rat intestinal cell line, IEC-6. IEC-6 cells treated with rhIL-11 or rhTGF-beta 1 exhibited a reduced proliferative rate as measured by cell counts and [3H]thymidine incorporation. The presence of neutralizing anti-TGF-beta 1 antibodies did not block the antiproliferative effect of rhIL-11 indicating that the rhIL-11 activity was not mediated through the induction of endogenous TGF-beta 1 production. Growth inhibition correlated with delayed entry into S phase of the cell cycle. Cell cycle arrest was associated with suppression of retinoblastoma protein phosphorylation. Transient cell cycle arrest is a possible mechanism by which rhIL-11 may protect intestinal epithelial cells from damage induced by chemotherapy or radiation therapy. This study provides a rationale for the clinical use of rhIL-11 to preserve the integrity of the gastrointestinal mucosa during cancer treatment regimens.

The levels of endoplasmic reticulum proteins and ATP affect folding and secretion of selective proteins

Proteins transiting the endoplasmic reticulum (ER) interact with a number of lumenal proteins, such as the glucose regulated proteins (GRPs), that either facilitate or prohibit protein folding and transport out of the ER compartment. We compared the relative amounts of mRNA encoding lumenal ER proteins in cells that secrete high levels of protein to those that do not secrete significant levels of protein. One of these proteins, GRP78, is thought to act as a chaperone to assist protein folding. We evaluated the effect of altered GRP78 expression on the secretion efficiency of heterologous proteins expressed in CHO cells. The secretion efficiency of proteins detected in significant association with GRP78 was reduced when GRP78 levels were overexpressed and improved when GRP78 levels were reduced. The results suggest that GRP78 does not act in a positive manner to promote protein folding and/or secretion. In addition, proteins that interact with GRP78 displayed a unique high requirement for intracellular ATP for secretion. Expression of firefly luciferase in the lumen of the ER detected ATP in the ER lumen of intact cells as monitored by light emission. Since luciferase light emission is proportional to ATP concentration, the amount of light emission may provide an approach to study the effect of altered ER intralumenal ATP on protein folding and secretion.

Regulation of PACE propeptide-processing activity: requirement for a post-endoplasmic reticulum compartment and autoproteolytic activation

PACE (paired basic amino acid cleaving enzyme) is a subtilisin-like serine protease involved in processing of propeptides in the constitutive secretory pathway. We here demonstrate that the transmembrane and cytoplasmic domains of PACE are required for retention in the secretory pathway but not for propeptide-cleaving activity. Addition of the endoplasmic reticulum retention signal Lys-Asp-Glu-Leu (KDEL) to the carboxyl terminus of the truncated molecule resulted in intracellular retention of the protein and loss of activity, indicating that the endoplasmic reticulum is an inappropriate environment for propeptide processing. In addition, mutation of a consensus PACE cleavage site within the amino-terminal region prevented processing of PACE to a mature form and destroyed activity. These data indicate that PACE is synthesized as a proprotein which requires autoproteolytic removal of an 81-residue pro sequence for optimal activity. A mutant form of PACE that lacked the pro sequence was nonfunctional, and addition of a pro sequence from a homologous subtilisin-like serine protease, PC2, did not restore activity. By analogy to the bacterial subtilisin family, the propeptide of PACE may guide the folding of PACE into an active enzyme.

Overexpression of GRP78 mitigates stress induction of glucose regulated proteins and blocks secretion of selective proteins in Chinese hamster ovary cells

GRP78 is a resident protein of the endoplasmic reticulum (ER) and a member of the glucose regulated protein (GRP) family. Many secretion incompetent proteins are found in stable association with GRP78 and are retained in the ER. Some proteins which are destined for secretion transiently associate with GRP78. To further increase our understanding of the role of GRP78 in secretion, we have stably overexpressed GRP78 in Chinese hamster ovary (CHO) cells and examined the effect on protein secretion and the stress response. GRP78 overexpressing cells treated with tunicamycin or A23187 exhibited a reduced induction of endogenous GRP78 and GRP94 mRNAs compared to wild-type CHO cells. This suggests that GRP78 overexpression either alleviates the stress or is directly involved in signaling stress-induced expression of GRPs. Transient expression of secreted proteins was used to measure secretion efficiency in the GRP78 overexpressing cells. Secretion of von Willebrand factor and a mutant form of factor VIII, two proteins which transiently associate with GRP78, was reduced by GRP78 overexpression. In contrast, secretion of M-CSF, which was not detected in association with GRP78, was unaffected. This indicates that elevated levels of GRP78 may increase stable association and decrease the secretion efficiency of proteins which normally transiently associate with GRP78. These results indicate that one function of GRP78 is selective protein retention in the ER.

The role of von Willebrand factor multimers and propeptide cleavage in binding and stabilization of factor VIII

von Willebrand factor (vWF) is a multimeric glycoprotein that promotes platelet aggregation and stabilizes coagulation factor VIII in the plasma. vWF is also required for the stable accumulation of recombinant factor VIII secreted from cells in a heterologous expression system. In this report, we show that vWF can promote the in vitro reconstitution of factor VIII activity from dissociated heavy and light chains of factor VIII, suggesting that vWF may act to promote stable assembly of factor VIII subunits at the site of secretion. The structural requirements for vWF propeptide cleavage and for vWF multimerization in its binding and stabilization of factor VIII was examined using specifically altered recombinant vWF. The mutant vWF molecules were also assayed for their function in ristocetin-induced platelet agglutination mediated through the platelet receptor GPIb. Deletion of the vWF propeptide produced a dimeric vWF molecule that failed to mediate platelet agglutination, suggesting that multimerization is required for vWF to attain functional GPIb binding. This mature dimeric form of vWF, however, was fully capable of binding to and supporting stable secretion of factor VIII. A vWF mutant with an altered propeptide cleavage site formed large multimers of uncleaved pro-vWF that functioned in platelet agglutination. However, this noncleavage mutant neither bound to or supported stable accumulation of factor VIII. Analysis of the vWF propeptide, expressed independently, demonstrated that it could not bind factor VIII or stabilize its secretion. These results show that the dimeric mature vWF subunit is sufficient to bind and stabilize factor VIII and that the presence of uncleaved vWF propeptide inhibits both factor VIII binding and stabilization.

Molecular cloning and characterization of a complete Chinese hamster provirus related to intracisternal A particle genomes

We report here the nucleotide sequence of a full-length Chinese hamster genomic proviral element, CHIAP34. CHIAP34 is 6,403 bp long with long terminal repeats of 311 bp at each end. The genetic organization of CHIAP34 was determined by comparison with intracisternal A particle (IAP) genetic elements from the mouse and Syrian hamster. Extensive homology at the nucleotide and deduced amino acid sequence levels was observed between CHIAP34 and the mouse and Syrian hamster IAP elements. CHIAP34 may represent a defective Chinese hamster IAP genetic element. The gag gene consists of 837 codons, of which 558 codons are in a single long open reading frame followed by several frameshifts. The pol gene begins with a -1 frameshift and consists of a long open reading frame of 753 codons followed by a short open reading frame of 103 codons. The putative env region contains multiple termination codons in all reading frames. CHIAP34 is representative of the predominant retroviral elements in the Chinese hamster ovary cell genome present at around 80 copies per haploid genome.

The importance of N- and O-linked oligosaccharides for the biosynthesis and in vitro and in vivo biologic activities of erythropoietin

Erythropoietin (EPO) plays a critical role in stimulating the proliferation and differentiation of erythroid precursor cells. EPO is heavily glycosylated with three asparagine (N)-linked tetraantennary oligosaccharides that may contain N-acetyl-lactosamine repeats and a single serine (O)-linked oligosaccharide. EPO expressed in Chinese hamster ovary cells exhibits biologic properties and amino acid and carbohydrate composition similar to natural urinary EPO. The importance of the complex N-linked and the O-linked carbohydrate was studied by expressing EPO in cells that are deficient in UDP-galactose/UDP-N-acetylgalactosamine 4-epimerase activity. In these cells, the ability to add galactose and N-acetylgalactosamine to glycoproteins can be controlled by the addition of these sugars to the culture medium. The results demonstrate that a block in O-linked glycosylation and/or the ability to process N-linked carbohydrate to completion does not alter EPO secretion. EPO produced without O-linked carbohydrate exhibits normal in vitro and in vivo biologic activity and in vivo clearance. However, EPO produced with incompletely processed N-linked oligosaccharides exhibits normal in vitro activity but is at least 500-fold less effective in stimulating erythropoiesis in vivo. Studies on the survival of bioactive EPO remaining in the circulation demonstrated that EPO with incomplete N-linked oligosaccharides exhibits a sevenfold increased rate of clearance. However, this increased clearance may not fully account for the 500-fold loss of in vivo activity. These results suggest a potentially important unique requirement for appropriate complex N-linked oligosaccharides for the intrinsic biologic activity of EPO in vivo.

The stress response in Chinese hamster ovary cells. Regulation of ERp72 and protein disulfide isomerase expression and secretion

Expression of the glucose-regulated proteins (GRPs), GRP78 and GRP94, is induced by a variety of stress conditions including treatment of cells with tunicamycin or the calcium ionophore A23187. The stimulus for induction of these resident endoplasmic reticulum (ER) proteins appears to be accumulation of misfolded or underglycosylated protein within the ER. We have studied the induction of mRNAs encoding two other resident ER proteins, ERp72 and protein disulfide isomerase (PDI), during the stress response in Chinese hamster ovary cells. ERp72 shares amino acid sequence homology with PDI within the presumed catalytic active sites. ERp72 mRNA and, to a lesser degree, PDI mRNA were induced by treatment of Chinese hamster ovary cells with tunicamycin or A23187. These results identify ERp72 as a member of the GRP family. Stable high level overproduction of ERp72 or PDI from recombinant expression vectors did not alter the constitutive or induced expression of other GRPs. High level overexpression resulted in secretion of the overproduced protein specifically but not other resident ER proteins. This suggests that the ER retention mechanism is mediated by more specific interactions than just KDEL sequence recognition.

High level synthesis of immunoglobulins in Chinese hamster ovary cells

The expression of lambda L and microH chain cDNA was examined in Chinese hamster ovary cells. Each cDNA was linked to a different, amplifiable, selectable drug marker gene, and expression was monitored in the presence of increasing concentrations of the selective drugs. Cells were obtained that produced greater than 60 micrograms/10(6) cells/48 h of assembled antibody. This Chinese hamster ovary cell-synthesized IgM was polymeric, and exhibited specific hapten binding and C fixation. The expression strategy employed here may prove useful for the future production of genetically engineered antibodies and other multi-subunit proteins.

High level synthesis of immunoglobulins in Chinese hamster ovary cells

The expression of lambda L and microH chain cDNA was examined in Chinese hamster ovary cells. Each cDNA was linked to a different, amplifiable, selectable drug marker gene, and expression was monitored in the presence of increasing concentrations of the selective drugs. Cells were obtained that produced greater than 60 micrograms/10(6) cells/48 h of assembled antibody. This Chinese hamster ovary cell-synthesized IgM was polymeric, and exhibited specific hapten binding and C fixation. The expression strategy employed here may prove useful for the future production of genetically engineered antibodies and other multi-subunit proteins.

Protein dissociation from GRP78 and secretion are blocked by depletion of cellular ATP levels

Secretory proteins expressed in Chinese hamster ovary (CHO) cells interact to various degrees with glucose-regulated protein 78 (GRP78), a resident protein of the endoplasmic reticulum. von Willebrand factor (vWF) and wild-type tissue plasminogen activator (tPA) are efficiently secreted and exhibit a slight transient association with GRP78. Factor VIII and unglycosylated tPA are inefficiently secreted and display a more stable association with GRP78. We have studied the effect of ATP depletion mediated by carbonyl cyanide 3-chlorophenylhydrazone (CCCP) treatment on GRP78 association and secretion of factor VIII and vWF that are coexpressed in CHO cells. Low concentrations of CCCP in the medium prevented disassociation of factor VIII from GRP78 and blocked its secretion. In the same cells, higher concentrations of CCCP were required to block secretion of vWF. Thus, the block to factor VIII secretion at low CCCP concentrations did not result from a general defect in secretion. Secretion of unglycosylated tPA but not wild-type tPA from CHO cells was also blocked by low concentrations of CCCP. The increased sensitivity to CCCP concentration observed for secretion of factor VIII and unglycosylated tPA compared to wild-type tPA and vWF correlates with their degree of interaction with GRP78. In vivo, dissociation from GRP78 may be a primary ATP-dependent step in transport from the endoplasmic reticulum. ATP requirements for secretion of various proteins may vary.

Increased synthesis of secreted proteins induces expression of glucose-regulated proteins in butyrate-treated Chinese hamster ovary cells

The effects of increased synthesis of secreted proteins expressed from stably integrated heterologous genes in Chinese hamster ovary (CHO) cells following treatment with sodium butyrate was studied. Butyrate treatment increased expression of mRNA transcribed from the adenovirus major late promoter in combination with the SV40 enhancer for Factor VIII, von Willebrand factor, and erythropoietin. Increased levels of mRNA were compared to increases in intracellular primary translation product and secreted protein. While von Willebrand factor and erythropoietin were efficiently secreted, Factor VIII was not. Increased expression of all these proteins induced expression of the glucose-regulated proteins, GRP78 and GRP94. However, increased Factor VIII synthesis was correlated with an 80-fold increase in GRP78 mRNA and a 10-fold increase in GRP94 mRNA. These data suggest that elevated levels of newly synthesized secretion-competent protein as well as misfolded protein induce the glucose-regulated proteins.

Effect of von Willebrand factor coexpression on the synthesis and secretion of factor VIII in Chinese hamster ovary cells

In plasma, antihemophilic factor (factor VIII) exists as a 200-kilodalton heavy-chain polypeptide in a metal ion association with an 80-kilodalton light-chain polypeptide. This complex is bound by hydrophobic and hydrophilic interactions to a large multimeric glycoprotein, von Willebrand factor (vWF). Accumulation of secreted human factor VIII activity expressed in Chinese hamster ovary cells requires the addition of serum in the growth medium, which provides vWF. Here we report that coexpression of vWF with factor VIII in Chinese hamster ovary cells resulted in increased stable accumulation of factor VIII activity in the absence of serum in the growth medium. In the coexpressing cells, the vWF cDNA transcription unit was transcribed to yield mRNA which was efficiently translated. vWF was properly processed and secreted to yield disulfide-bonded high-molecular-weight multimers similar to those observed in vWF secreted from human endothelial cells. Nuclear run-on assays showed that the factor VIII gene was transcribed at a level similar to that of the vWF gene, but the mRNA did not accumulate to high levels in the cytoplasm. In addition, although the translation efficiency of the factor VIII mRNA was similar to that of vWF, the processing and secretion of the factor VIII primary translation product was dramatically reduced compared with vWF. These results demonstrate that in Chinese hamster ovary cells both factor VIII mRNA accumulation and the processing and secretion of the primary factor VIII translation product are inefficient processes.

Reduction of endogenous GRP78 levels improves secretion of a heterologous protein in CHO cells

GRP78 is localized in the endoplasmic reticulum and associates with improperly folded or underglycosylated proteins. The role of GRP78 in secretion was studied in Chinese hamster ovary cells expressing a tissue plasminogen activator (tPA) variant which lacks potential N-linked glycosylation site sequences because of mutagenesis. The expression of variant tPA resulted in elevated levels of GRP78 and its stable association with tPA. The introduction of antisense GRP78 genes resulted in a two- to threefold reduction in GRP78 levels compared with those of the original cells. Cells with reduced levels of GRP78 secreted two- to threefold-higher levels of tPA activity. tPA expressed in these cells displayed reduced association with GRP78, and a greater proportion was processed to the mature form and secreted. These results demonstrate that reduction of GRP78 level can improve the secretion of an associated protein.

Synthesis, processing, and secretion of recombinant human factor VIII expressed in mammalian cells

The synthesis, processing, and secretion of factor VIII expressed from heterologous genes introduced into Chinese hamster ovary cells has been studied. The results show factor VIII to be synthesized as a primary translation product of approximately 230 kDa that can be detected in the lumen of the endoplasmic reticulum. In this compartment, the majority of the factor VIII is in a complex with a resident protein of the endoplasmic reticulum, binding protein, and may never appear in the medium. Some factor VIII transits the endoplasmic reticulum to the Golgi apparatus, where it is cleaved to generate the mature heavy and light chains. In the absence of von Willebrand factor in the medium, the secreted heavy and light chains are unassociated and subsequently degraded. In the presence of von Willebrand factor in the medium, the heavy and light chains are secreted as a stable complex and activity accumulates linearly with time. The utilization and complexity of asparagine-linked carbohydrate present on the secreted recombinant-derived factor VIII and human plasma-derived factor VIII were compared and found to be very similar. In both cases, the asparagine-linked carbohydrate moieties on the heavy chain are primarily of the hybrid or complex-type. In contrast, the factor VIII from both sources contains a high-mannose type of asparagine-linked carbohydrate on the light chain.

The relationship of N-linked glycosylation and heavy chain-binding protein association with the secretion of glycoproteins

The relationship of N-linked glycosylation and association with heavy chain binding protein (BiP) to the secretion of Factor VIII (FVIII), von Willebrand Factor (vWF), and tissue plasminogen activator (tPA) was studied in Chinese hamster ovary (CHO) cells. FVIII has a heavily glycosylated region containing 20 clustered potential N-linked glycosylation sites. A significant proportion of FVIII was detected in a stable complex with BiP and not secreted. Deletion of the heavily glycosylated region resulted in reduced association with BiP and more efficient secretion. Tunicamycin treatment of cells producing this deleted form of FVIII resulted in stable association of unglycosylated FVIII with BiP and inhibition of efficient secretion. vWF contains 17 potential N-linked glycosylation sites scattered throughout the molecule. vWF was transiently associated with BiP and efficiently secreted demonstrating that CHO cells are competent to secrete a highly glycosylated protein. tPA, which has three utilized N-linked glycosylation sites, exhibited low level association with BiP and was efficiently secreted. Disruption of N-linked glycosylation of tPA by either site-directed mutagenesis or tunicamycin treatment resulted in reduced levels of secretion and increased association with BiP. This effect was enhanced by high levels of tPA expression. The glycosylation state and extent of association with BiP could be correlated with secretion efficiency.

Determinants for receptor interaction and cell killing on the avian retrovirus glycoprotein gp85

The virion envelope glycoprotein gp85 confers a high degree of subgroup specificity for interaction with distinct cell receptors. Specific subgroups of gp85 have been associated with a cytopathic virus-cell interaction, most likely resulting from reduced resistance to superinfection, which allows the buildup of excessive amounts of viral DNA. Previous nucleotide sequence analysis of the gp85 coding region identified small regions of variable amino acid sequence within a conserved framework. To define the role of these variable regions we constructed a series of molecular clones carrying novel combinations of variable regions from viruses. Analysis of rescued virus shows that receptor binding is determined by the interaction of two major regions and one minor region in the middle of gp85. Cytopathogenicity is not associated with any specific variable region but rather with the ability to recognize the subgroup B receptor on chicken cells.

Production of infectious poliovirus from cloned cDNA is dramatically increased by SV40 transcription and replication signals

Sub-genomic cDNA clones representing the entire genomic RNA of poliovirus Type 1 (Mahoney) have been isolated in E. coli. Construction of a complete cDNA copy of the poliovirus genome in the EcoRI site of plasmid vector pBR325 from these clones is described. Introduction of plasmid DNA containing the complete cDNA copy of polio RNA into cultured primate cells by transfection produces infectious poliovirus. The virus produced by such a transfection appears to be identical to wild type poliovirus. Isolation of a polio recombinant plasmid containing SV40 transcription and replication signals is also described. Transfection of COS-1 cells with this plasmid yields greater than 1,600 plaque-forming units (PFU) per microgram of input DNA.