Regulation of the Expression, Oligomerisation and Signaling of the Inhibitory Receptor CLEC12A by Cysteine Residues in the Stalk Region

CLEC12A is a myeloid inhibitory receptor that negatively regulates inflammation in mouse models of autoimmune and autoinflammatory arthritis. Reduced CLEC12A expression enhances myeloid cell activation and inflammation in CLEC12A knock-out mice with collagen antibody-induced or gout-like arthritis. Similarly to other C-type lectin receptors, CLEC12A harbours a stalk domain between its ligand binding and transmembrane domains. While it is presumed that the cysteines in the stalk domain have multimerisation properties, their role in CLEC12A expression and/or signaling remain unknown. We thus used site-directed mutagenesis to determine whether the stalk domain cysteines play a role in CLEC12A expression, internalisation, oligomerisation, and/or signaling. Mutation of C118 blocks CLEC12A transport through the secretory pathway diminishing its cell-surface expression. In contrast, mutating C130 does not affect CLEC12A cell-surface expression but increases its oligomerisation, inducing ligand-independent phosphorylation of the receptor. Moreover, we provide evidence that CLEC12A dimerisation is regulated in a redox-dependent manner. We also show that antibody-induced CLEC12A cross-linking induces flotillin oligomerisation in insoluble membrane domains in which CLEC12A signals. Taken together, these data indicate that the stalk cysteines in CLEC12A differentially modulate this inhibitory receptor’s expression, oligomerisation and signaling, suggestive of the regulation of CLEC12A in a redox-dependent manner during inflammation.

Dual action of a selective cyclooxygenase-2 inhibitor on vascular endothelial growth factor expression in human hepatocellular carcinoma cells: novel involvement of discoidin domain receptor 2

PURPOSE

Vascular endothelial growth factor (VEGF) greatly contributes to the progression of hepatocellular carcinoma (HCC). It is reported that a selective cyclooxygenase-2 (COX-2) inhibitor inhibits cellular proliferation and may attenuate VEGF expression in HCC. We propose that different cascades in the VEGF pathway respond to COX-2 inhibition, depending on the cell types.

METHODS

The six human HCC cell lines--Hep3B, SNU387, SNU182, SNU423, SNU449, and PLC/PRF5--were cultured under normoxic and hypoxic conditions. Cells were treated with a selective COX-2 inhibitor (NS-398) and discoidin domain receptor 2 (DDR2) siRNA, and microarray analysis was performed.

RESULTS

NS-398 inhibited HCC proliferation and decreased the expression level of VEGF in HCC cells only under normoxia conditions. In hypoxia conditions, VEGF expression level in Hep3B cell was suppressed, while that in SNU387 cell was increased by NS-398 (P < 0.001). The NS-398-induced increase in VEGF expression in SNU387 cell was associated with the up-regulation of the DDR2 gene. NS-398-treated SNU series cells and PLC/PRF5 cells displayed a robust increase in DDR2 mRNA expression. Also, transfection with DDR2 siRNA decreased the VEGF expression level of SNU387, 423, 449 cells under hypoxia conditions (P < 0.05). In vivo chromatin immunoprecipitation assay demonstrated that NS-398 induces the enhancement of HIF-1α binding on VEGF promoter, leading to the increase in VEGF gene expression in hypoxic conditions. There is strong evidence that it is related to the DDR2 gene expression in SNU387 cells.

CONCLUSION

These findings disclose a novel cell-dependent regulatory mechanism of VEGF involving DDR2 gene in HCC cells.

Expression and mutation analysis of the discoidin domain receptors 1 and 2 in non-small cell lung carcinoma

The discoidin domain receptors, (DDR)1 and DDR2, have been linked to numerous human cancers. We sought to determine expression levels of DDRs in human lung cancer, investigate prognostic determinates, and determine the prevalence of recently reported mutations in these receptor tyrosine kinases. Tumour samples from 146 non-small cell lung carcinoma (NSCLC) patients were analysed for relative expression of DDR1 and DDR2 using quantitative real-time PCR (qRT-PCR). An additional 23 matched tumour and normal tissues were tested for differential expression of DDR1 and DDR2, and previously reported somatic mutations. Discoidin domain receptor 1 was found to be significantly upregulated by 2.15-fold (P=0.0005) and DDR2 significantly downregulated to an equivalent extent (P=0.0001) in tumour vs normal lung tissue. Discoidin domain receptor 2 expression was not predictive for patient survival; however, DDR1 expression was significantly associated with overall (hazard ratio (HR) 0.43, 95% CI=0.22–0.83, P=0.014) and disease-free survival (HR=0.56, 95% CI=0.33–0.94, P=0.029). Multivariate analysis revealed DDR1 is an independent favourable predictor for prognosis independent of tumour differentiation, stage, histology, and patient age. However, contrary to previous work, we did not observe DDR mutations. We conclude that whereas altered expression of DDRs may contribute to malignant progression of NSCLC, it is unlikely that this results from mutations in the DDR1 and DDR2 genes that we investigated.

Increased expression of the collagen internalization receptor uPARAP/Endo180 in the stroma of head and neck cancer

Local growth, invasion, and metastasis of malignancies of the head and neck involve extensive degradation and remodeling of the underlying, collagen-rich connective tissue. Urokinase plasminogen activator receptor-associated protein (uPARAP)/Endo180 is an endocytic receptor recently shown to play a critical role in the uptake and intracellular degradation of collagen by mesenchymal cells. As a step toward determining the putative function of uPARAP/Endo180 in head and neck cancer progression, we used immunohistochemistry to determine the expression of this collagen internalization receptor in 112 human squamous cell carcinomas and 19 normal or tumor-adjacent head and neck tissue samples from the tongue, gingiva, cheek, tonsils, palate, floor of mouth, larynx, maxillary sinus, upper jaw, nasopharynx/nasal cavity, and lymph nodes. Specificity of detection was verified by staining of serial sections with two different monoclonal antibodies against two non-overlapping epitopes on uPARAP/Endo180 and by the use of isotype-matched non-immune antibodies. uPARAP/Endo180 expression was observed in stromal fibroblast-like, vimentin-positive cells. Furthermore, expression of the collagen internalization receptor was increased in tumor stroma compared with tumor-adjacent connective tissue or normal submucosal connective tissue and was most prominent in poorly differentiated tumors. These data suggest that uPARAP/Endo180 participates in the connective tissue destruction during head and neck squamous cell carcinoma progression by mediating cellular uptake and lysosomal degradation of collagen.

A high-potassium diet reduces infarct size and improves vascular structure in hypertensive rats

High-potassium diets can improve vascular function, yet the effects of potassium supplementation on ischemic stroke have not been studied. We hypothesized that dietary potassium supplementation would reduce ischemic cerebral infarct size by reversing cerebral artery hypertrophy. Six-week-old male stroke-prone spontaneously hypertensive rats (SHRSP) were fed diets containing 0.79% potassium (LK) or 2.11% potassium (HK) for 6 wk; Wistar-Kyoto (WKY) rats were fed the LK diet. The HK diet did not reduce blood pressure, as measured by telemetry, in the SHRSP. Cerebral ischemia was induced by middle cerebral artery (MCA) occlusion. The resultant infarct was smaller in the HK-SHRSP than in the LK-SHRSP: 55.1 +/- 6.3 vs. 71.4 +/- 2.4% of the hemisphere infarcted (P < 0.05). Infarcts were smaller in WKY rats (33.5 +/- 4.8%) than in LK-SHRSP or HK-SHRSP. The vessel wall of MCAs from LK-SHRSP was hypertrophied compared with WKY rats; this was reversed in HK-SHRSP. RT-PCR analysis of the cerebral vessels showed that expression of platelet-derived growth factor receptors-alpha and -beta, epidermal growth factor receptor, and collagen I and III was increased in the vessels from LK-SHRSP compared with WKY rats and reduced in HK-SHRSP. These results suggest that potassium supplementation provides neuroprotection in a model of ischemic stroke independent of blood pressure and possibly through changes in vascular structure.

Suppression of discoidin domain receptor 1 by RNA interference attenuates lung inflammation

Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase whose ligand is collagen. Recently, we have reported the association of DDR1 in the cytokine production of human leukocytes in in vitro and in vivo expression in idiopathic pulmonary fibrosis. However, its role in in vivo inflammation has not been fully elucidated. Small interference RNA (siRNA) can induce specific suppression of in vitro and in vivo gene expression. In this study, using a bleomycin-induced pulmonary fibrosis mouse model, we administered siRNA against DDR1 transnasally and evaluated histological changes, cytokine expression, and signaling molecule activation in the lungs. Histologically, siRNA against DDR1 successfully reduced in vivo DDR1 expression and attenuated bleomycin-induced infiltration of inflammatory cells. Furthermore, it significantly reduced inflammatory cell counts and concentrations of cytokines such as MCP-1, MIP-1alpha, and MIP-2 in bronchoalveolar lavage fluid. Subsequently, bleomycin-induced up-regulation of TGF-beta in bronchoalveolar lavage fluid was significantly inhibited, and collagen deposition in the lungs was reduced. Furthermore, siRNA against DDR1 significantly inhibited bleomycin-induced P38 MAPK activation in the lungs. Considered together, we propose that DDR1 contributes to the development of bleomycin-induced pulmonary inflammation and fibrosis.

Localization of Discoidin Domain Receptors in Rat Kidney

BACKGROUND/AIM

The discoidin domain receptors (DDRs) DDR1 and DDR2 are cardinal members of a receptor tyrosine kinase subfamily, activated by collagens. They are candidate effectors in tissue injury and fibrosis. We investigated the DDR expression in normal and remnant rat kidneys.

METHODS

The DDR expression in kidney and other tissues was examined by indirect immunofluorescence, immunoblotting, and ribonuclease protection assays. The expression patterns in remnant and control kidneys were compared at 2-, 4-, and 8-week time points, following induction of injury.

RESULTS

DDR1 is expressed in basolateral membranes of select nephron segments, from the connecting tubule to the renal papilla. DDR2 is expressed in apical membranes of select nephron segments, from the loop of Henle to the macula densa. The DDR1 protein expression is upregulated within the glomeruli of remnant kidneys. The distribution of DDR2 in remnant kidneys is similar to that in controls. The DDR mRNA levels in remnant and control kidneys were not significantly different, at any time point.

CONCLUSIONS

The DDR1 localization in the rat kidney is consistent with roles in cell-matrix interactions. Upregulation within glomeruli of remnant kidneys suggests the possibility of additional roles in kidney injury. The DDR2 localization in adult rat kidneys is inconsistent with roles in cell-matrix interactions.

Activation of Discoidin Domain Receptor 1 Facilitates the Maturation of Human Monocyte-Derived Dendritic Cells Through the TNF Receptor Associated Factor 6/TGF-β-Activated Protein Kinase 1 Binding Protein 1β/p38α Mitogen-Activated Protein Kinase Signaling Cascade

Maturation of dendritic cells (DCs) is critical for their ability to stimulate resting naive T cells in primary immune responses. Previous studies demonstrated that collagen, such as type I collagen, could facilitate DC maturation; however, the basis of collagen-mediated DC maturation remains unclear. Discoidin domain receptor 1 (DDR1) is a nonintegrin collagen receptor constitutively expressed in a variety of epithelial cells, including tumor cells, and is inducible in leukocytes. In this study, we evaluated the role of DDR1 in DC maturation using human monocyte-derived DCs. Two DDR1 isoforms, DDR1a and DDR1b, were expressed in both immature and mature DCs. Activation of DDR1 on immature DCs resulted in their partial maturation; however, DDR1 activation markedly amplified TNF-alpha- and LPS-induced phenotypic and functional maturation of DCs through activation of p38 mitogen-activated protein kinase (MAPK), suggesting the involvement of DDR1b in this process. Activation of DDR1b on differentiated DDR1b-overexpressing THP-1 cells or DDR1 on mature DCs induced the formation of TNFR associated factor 6 (TRAF6)/TGF-beta-activated kinase 1 binding protein 1beta/p38alpha MAPK complex and p38alpha autophosphorylation. Transfection of differentiated DDR1b-overexpressing THP-1 cells with dominant negative TRAF6 completely abrogated DDR1b-mediated p38 MAPK phosphorylation, indicating a critical role of TRAF6 in DDR1b-mediated p38 MAPK activation. Taken together, our data suggest that DDR1b-collagen interaction augments the maturation of DCs in a tissue microenvironment through a unique TRAF6/TGF-beta-activated kinase 1 binding protein 1beta/p38alpha MAPK signaling cascade and contributes to the development of adaptive immune responses.

Preferential survival of CD8 T and NK cells expressing high levels of CD94

The Qa-1(b)/Qdm tetramer binds to CD94/NKG2 receptors expressed at high levels on approximately 50% of murine NK cells. Although very few CD8 T cells from naive mice express CD94/NKG2 receptors, approximately 50% of CD8 T cells taken from mice undergoing a secondary response against Listeria monocytogenes (LM) are CD94(high) and bind the tetramer. Although CD94(int) NK cells do not bind the tetramer, CD94(int) CD8 T cells do, and this binding is dependent on the CD8 coreceptor. We found that the extent of apoptosis in CD8 T and NK cells was inversely related to the expression of CD94, with lower levels of apoptosis seen in CD94(high) cells after 1-3 days of culture. The difference in CD8 T cell survival was evident as early as 6 h after culture and persisted until nearly all the CD94(neg/int) cells were apoptotic by 48 h. In contrast, expression of inhibitory Ly-49A,G2,C/I molecules was associated with higher levels of apoptosis. Cross-linking CD94/NKG2 receptors on CD8 T cells from a mouse undergoing an LM infection further reduced the percentage of apoptotic cells on the CD94-expressing populations, while cross-linking Ly-49I had no effect on CD8 T cells expressing Ly-49I. Cross-linking CD3 on CD8 T cells from a mouse undergoing a secondary LM infection increases the extent of apoptosis, but this is prevented by cross-linking CD94/NKG2 receptors at the same time. Similar results were observed with NK cells in that the CD94(high) population displayed less apoptosis than CD94(int) cells after 1-3 days in culture. Therefore, the expression of CD94/NKG2 is correlated with a lower level of apoptosis and may play an important role in the maintenance of CD8 T and NK cells.

Molecular modes of action of cephalotaxine and homoharringtonine from the coniferous tree Cephalotaxus hainanensis in human tumor cell lines

Homoharringtonine (HHT) is an ester of cephalotaxine (CET), both of which derive from the Chinese coniferous tree Cephalotaxus hainanensis. HHT inhibited tumor cell growth at molar ranges comparable to established cytostatic drugs, whereas CET was 3-4 orders of magnitude less active. Inhibition concentration 50% (IC50) values of CET and HHT were significantly correlated to doxorubicin, vincristine, methotrexate, cisplatin, or camptothecin in 55 cell lines of the Developmental Therapeutics Program of the National Cancer Institute (NCI, Bethesda, Md., USA). We tested both drugs for resistance of cell lines which selectively overexpress the multidrug resistance (MDR)-conferring genes P-glycoprotein/ MDR1 (CEM/ADR5000), MDR-related protein 1 MRP1 (HL60/AR), and breast cancer resistance protein BCRP (MDA-MB-231-BCRP). A threefold and ninefold resistance to HHT and CET, respectively, was found in CEM/ADR5000 cells, while the other MDR cell lines did not show cross-resistance compared to their drug-sensitive counterparts. As the tumor suppressor p53 is another important factor of chemoresistance, we also analyzed the possibility that p53 affects the response of tumor cells to CET and HHT. Comparing the p53 mutational status of the 55 NCI cell lines (http://dtp.nci.nih.gov) with the IC50 values showed a significant correlation. Thus, CET and HHT were more active in cell lines without p53 mutation. We correlated the IC50 values of CET and HHT with the cell doubling times of the 55 NCI cell lines as proliferation parameter and observed that rapidly growing cells were more susceptible than slowly growing cell lines. We conducted a search mining the NCI's database for the mRNA expression of 465 genes in 55 cell lines and correlated the data with the IC50 values for CET and HHT. Of these genes 61 (=13%) correlated with the IC50 values for CET and 122 (=26%) with the IC50 values for HHT indicating the multifactorial mode of action of these drugs in cancer cells. We have chosen one example from these genes to test a causative role for drug response. U-87MG.DeltaEGFR cells transfected with an epidermal growth factor receptor ( EGFR) gene truncated in its extracellular domain through a deletion of exons 2-7 (Delta EGFR) were 14-fold more resistant to HHT than control cells transfected with mock expression vector or non-transfected cells. The present investigation presents a starting point to dissect the genes and molecular pathways involved in the tumor cells' response to CET and HHT in greater detail.

Elevated expression of tyrosine kinase DDR2 in primary biliary cirrhosis

BACKGROUND

Primary biliary cirrhosis (PBC) is characterized by chronic progressive destruction of small intrahepatic bile ducts with portal inflammation and cholestasis, leading to fibrosis.

METHODS

We utilized a novel restriction analysis system to profile the expression of tyrosine kinases (TKs). This methodology targets a conserved sequence present in the majority of human TKs, and exploits the known restriction map of the TK cDNA sequences. We isolated mRNA from biliary epithelial cell (BEC)-enriched cell fractions, amplified the TK transcripts using degenerative primers, and identified specific TKs by restriction enzyme digest analysis and then performed in situ hybridization.

RESULTS

BEC-enriched samples from PBC livers displayed marked expression of discoidin domain receptor-2 (DDR2), whereas, non-diseased livers showed no detectable DDR2. Furthermore, in situ hybridization of PBC livers revealed that DDR2 is expressed in the small bile duct epithelial regions as well as in fibroblasts/stromal cells of fibrotic regions. A similar pattern was observed in livers of primary sclerosing cholangitis (PSC), although the amount of small ducts that were positively stained was lower than in PBC. Furthermore, cirrhotic livers of patients with other diseases, including alcoholic liver disease and chronic hepatitis C, DDR2 transcripts were noted only within fibrotic lesions and the degree of intensity was much lower than in PBC and PSC.

CONCLUSIONS

DDR2, a TK that is stimulated by fibrillar collagens that accumulate in cirrhotic livers, is present at elevated levels in the small bile ducts of PBC patients. DDR2 is part of a positive feedback loop in which its enhanced expression leads to enhanced deposition of fibrillar collagens (types I andIII). These fibrillar collagens can also provide binding sites for immune mediators, such as cytokines and chemokines. Therefore, unusually high DDR2 expression in the bile ducts of PBC patients could contribute to duct injury by altering local cytokine levels and thereby increasing immune-mediated damage.

Overexpression of vascular endothelial growth factor (VEGF) and its cellular receptor KDR (VEGFR-2) in the bone marrow of patients with acute myeloid leukemia

Vascular endothelial growth factor (VEGF) and its cellular receptor VEGFR-2 have been implicated as the main endothelial pathway required for tumor neovascularization. However, the importance of the VEGF/VEGFR-2 system for angiogenesis in hematologic malignancies such as AML remains to be elucidated. In 32 patients with newly diagnosed untreated AML, we observed by immunohistochemical analysis of bone marrow biopsies significantly higher levels of VEGF and VEGFR-2 expression than in 10 control patients (P <0.001). In contrast, VEGFR-1 staining levels in AML patients were in the same range as in the controls. Expression of VEGF and VEGFR-2 was significantly higher in patients with a high degree of microvessel density compared to those with a low degree (VEGF: P =0.024; VEGFR-2: P =0.040) and correlated well with bone marrow microvessel density (r(s)=0.566 and 0.609, respectively; P <0.001). Furthermore, in patients who achieved a complete remission following induction chemotherapy VEGFR-2 staining levels decreased into the normal range. In conclusion, our results provide evidence for increased expression of VEGF/VEGFR-2 of leukemic blasts and correlation with angiogenesis in the bone marrow of AML patients. Thus, VEGF/VEGFR-2 might constitute promising targets for antiangiogenic and antileukemic treatment strategies in AML.

Shear stress induces expression of vascular endothelial growth factor receptor Flk-1/KDR through the CT-rich Sp1 binding site

Fluid shear stress is 1 of the major factors that control gene expression in vascular endothelial cells. We investigated the role of shear stress in the regulation of the expression of fetal liver kinase-1/kinase domain region (Flk-1/KDR), a vascular endothelial growth factor receptor, by using human umbilical vein endothelial cells. Laminar shear stress (15 dyne/cm2) elevated Flk-1/KDR mRNA levels by approximately 3-fold for 8 hours, and the expression was upregulated within the range of 5 to 40 dyne/cm2. Deletion analysis of the 5'-flanking region of the Flk-1/KDR gene promoter by use of a luciferase reporter vector revealed that a shear stress-responsive element resided in the sequence between -94 and -31 bp, which contained putative nuclear factor-kappaB, activator protein-2, and GC-rich Sp1 and CT-rich Sp1 binding sites. Electrophoretic mobility shift assay demonstrated that nuclear extract was bound to the GC-rich Sp1 sites and the CT-rich Sp1 site with a similar pattern. However, shear stress enhanced the DNA-protein interactions only on the CT-rich Sp1 site but not on the GC-rich Sp1 sites. A 3-bp mutation in the CT-rich Sp1 site eliminated the response to shear stress in electrophoretic mobility shift assay and luciferase reporter assay. These results suggest that shear stress induces Flk-1/KDR expression through the CT-rich Sp1 binding site.

Sequence-dependent effects of ZD1839 ('Iressa') in combination with cytotoxic treatment in human head and neck cancer

Elevated levels of epidermal growth factor receptor in head and neck cancer have been extensively reported, and are correlated with poor prognosis. The combination of cisplatin and 5-fluorouracil is a standard treatment regimen for head and neck cancer, with radiation representing another therapeutic option. Six head and neck cancer cell lines were used to study the cytotoxic effects of combining ZD1839 ('Iressa'), a new selective epidermal growth factor receptor tyrosine kinase inhibitor, and radiation. Two of the cell lines were also used to study the combination of ZD1839 and cisplatin/5-fluorouracil. Cytotoxic effects were assessed by the MTT test. The results indicated that ZD1839 applied before radiation gave the best effects (P=0.002); an effect that was strongest in those p53-mutated cell lines that express the highest epidermal growth factor receptor levels. The effects of ZD1839 with cisplatin and/or 5-fluorouracil were sequence dependent (P<0.003), with the best results achieved when ZD1839 was applied first. For the triple combinations, ZD1839 applied before cisplatin and 5-fluorouracil resulted in a slight synergistic effect (P=0.03), although the effect was greater when ZD1839 was applied both before and during cytotoxic drug exposure. In conclusion, ZD1839 applied before radiation and before and/or during cisplatin/5-fluorouracil may improve the efficacy of treatment for head and neck cancer.

The urokinase plasminogen activator receptor-associated protein/endo180 is coexpressed with its interaction partners urokinase plasminogen activator receptor and matrix metalloprotease-13 during osteogenesis

The urokinase plasminogen activator receptor-associated protein/Endo180 (uPARAP/Endo180) is a newly discovered member of the macrophage mannose receptor family that was reported to interact with ligand-bound urokinase plasminogen activator receptor (uPAR), matrix metalloprotease-13 (MMP-13), and collagen V on the cell surface. We have determined the sites of expression of this novel receptor during murine postimplantation development. uPARAP/Endo180 was expressed in all tissues undergoing primary ossification, including the developing bones of the viscerocranium and calvarium that ossify intramembranously, and developing long bones undergoing endochondral ossification. uPARAP/Endo180 mRNA was expressed by both immature osteoblasts and by mature osteocalcin-producing osteoblasts-osteocytes, and was coexpressed with MMP-13. Interestingly, osteoblasts also expressed uPAR. Besides bone-forming tissues, uPARAP/Endo180 expression was detected only in a mesenchymal condensation of the midbrain and in the developing lungs. The data suggest a function of this novel protease receptor in bone development, possibly mediated through its interactions with uPAR, MMP-13, or collagen V.

Discoidin domain receptor 1 functions in axon extension of cerebellar granule neurons

In the developing cerebellum, granule neuron axon outgrowth is a key step toward establishing proper connections with Purkinje neurons, the principal output neuron of the cerebellum. During a search for genes that function in this process, we identified a receptor tyrosine kinase discoidin domain receptor 1 (DDR1) expressed in granule cells throughout their development. Overexpression of a dominant-negative form of DDR1 in immature granule cells results in severe reduction of neurite outgrowth in vitro, in dissociated primary culture, and in vivo, in organotypic slices of neonatal cerebellum. Granule cells that fail to extend axons are positive for differentiation markers such as TAG-1 and the neuron-specific class III beta-tubulin, suggesting that development is affected after granule cells commit to terminal differentiation. DDR1 activation appears to be mediated by its ligand, collagen, which is localized to the pial layer of the developing cerebellum, thereby leading to granule cell parallel fiber extension. Our results therefore indicate that collagen-DDR1 signaling is essential for granule neuron axon formation and further suggest a unique role of pia in cerebellar cortex histogenesis.

The role of vascular endothelial growth factor in human dental pulp cells: induction of chemotaxis, proliferation, and differentiation and activation of the AP-1-dependent signaling pathway

Vascular endothelial growth factor (VEGF) is a potent mitogen in endothelial cells, but little is known about its activity in other cell types. To clarify the role of VEGF in human dental pulp cells and pulp tissue, we investigated the effects of VEGF on the chemotaxis, proliferation, and differentiation of human dental pulp cells. VEGF induced a strong chemotactic response in human dental pulp cells in a dose-dependent manner. VEGF also marginally enhanced the proliferation of human dental pulp cells and induced an increase in alkaline phosphatase in human dental pulp cells. However, these effects of VEGF were not observed in reference to human skin fibroblasts. Analyses by the reverse-transcription/polymerase-chain-reaction method and flow cytometry showed that the mRNAs of two VEGF receptors, fins-like tyrosine kinase and kinase insert domain-containing receptor, were expressed in human dental pulp cells, whereas only fms-like tyrosine kinase mRNA was expressed in human skin fibroblasts. VEGF induced the activation of activator protein 1 (AP-1) and c-fos mRNA expression in human dental pulp cells. The AP-1 inhibitor curcumin strongly inhibited VEGF-induced alkaline phosphatase production in human dental pulp cells. In addition, VEGF antisense oligonucleotide suppressed the production of VEGF and alkaline phosphatase in human dental pulp cells. These results suggest that VEGF produced by human dental pulp cells acts directly upon human dental pulp cells in an autocrine manner, and may promote the chemotaxis, proliferation, and/or differentiation of human dental pulp cells via the utilization of kinase insert domain-containing receptor and in part through AP-1 by increasing c-fos.

Disordered expression of inhibitory receptors on the NK1-type natural killer (NK) leukaemic cells from patients with hypersensitivity to mosquito bites

Recent studies have revealed the existence of a distinct type of NK cell leukaemia of the juvenile type, which presents with hypersensitivity to mosquito bites (HMB) as an essential clinical manifestation and is infected with clonal Epstein-Barr virus (EBV). This disorder is thus called HMB-EBV-NK disease and has been reported in Orientals, mostly from Japan. We investigated the profile of cytokine production and the expression of both types of NK inhibitory receptors, i.e. CD94 lectin-like dimers and killer-cell immunoglobulin-like receptors, in NK leukaemic cells from three patients with HMB-EBV-NK disease. It was found that freshly isolated NK leukaemic cells expressed mRNA for interferon-gamma (IFN-gamma) and additionally produced IL-10 upon stimulation with IL-2, indicating that the NK cells were of NK1 type. More than 98% of NK cells from the patients bore CD94 at a higher level than did normal NK cells, whereas p70 or NKAT2, belonging to immunoglobulin-like receptor, was not expressed in those NK cells. Freshly isolated leukaemic NK cells transcribed mRNA for CD94-associated molecule NKG2C at an abnormally high level, and upon stimulation with IL-2 and/or IL-12 they expressed NKG2A as well. The disordered expression of these inhibitory receptors not only provides some insights into the pathogenesis of HMB-EBV-NK disease but also can be used as phenotypic markers for the diagnosis of this type of NK cell leukaemia.

Expression of vascular endothelial growth factor (VEGF) and VEGF receptors in human neuroblastomas

BACKGROUND

Vascular endothelial growth factor (VEGF) is a specific endothelial cell mitogen that stimulates angiogenesis and plays a crucial role in tumor growth. The aim of the present study was to evaluate the expression of VEGF and of its two high-affinity tyrosine kinase receptors (KDR and Flt-1) in neuroblastoma surgical samples and cell lines.

PROCEDURE

The VEGF, KDR, and Flt-1 mRNA expression in neuroblastoma surgical samples and cell lines was studied by RT-PCR. The receptors were identified in [(125)I]VEGF binding and in functional studies (effect on cell growth). VEGF production by neuroblastomas was investigated by the ELISA method.

RESULTS

It was possible to observe the mRNAs encoding for VEGF and its two receptors in some of the surgical specimens examined, including most of the high-grade tumors. It was also possible to demonstrate that the SK-N-BE cell line expressed VEGF, KDR, and Flt-1 mRNAs as well as biologically active receptors: The cells bound [(125)I]-VEGF, and their growth was stimulated by exogenous VEGF. Moreover, VEGF protein could be detected in their culture conditioned medium.

CONCLUSIONS

These results suggest that, in addition to its effect on angiogenesis, VEGF may affect neuroblastoma cell growth directly and could be an autocrine growth factor.

Identification of CD66a and CD66b as the major galectin-3 receptor candidates in human neutrophils

The mammalian lectin galectin-3 is a potent stimulus of human neutrophils, provided that the receptor(s) for the lectin has been mobilized to the cell surface before activation. We have recently shown that the receptors for galectin-3 are stored in intracellular mobilizable granules. Here we show supportive evidence for this in that DMSO-differentiated (neutrophil-like) HL-60 cells, which lack gelatinase and specific granules, are nonresponsive when exposed to galectin-3. Neutrophil granules were subsequently used for isolation of galectin-3 receptors by affinity chromatography. Proteins eluted from a galectin-3-Sepharose column by lactose were analyzed on SDS-polyacrylamide gels and showed two major bands of 100 and 160 kDa and a minor band of 120 kDa. By immunoblotting, these proteins were shown to correspond to CD66a (160 kDa), CD66b (100 kDa), and lysosome-associated membrane glycoprotein-1 and -2 (Lamp-1 and -2; 120 kDa). The unresponsive HL-60 cells lacked the CD66 Ags but contained the Lamps, implying that neutrophil CD66a and/or CD66b may be the functional galectin-3 receptors. This conclusion was supported by the subcellular localization of the CD66 proteins to the gelatinase and specific granules in resting neutrophils.

The receptor-mediated uptake, survival, replication, and drug sensitivity of Mycobacterium tuberculosis within the macrophage-like cell line THP-1: a comparison with human monocyte-derived macrophages

We have compared the interaction of Mycobacterium tuberculosis with the human macrophage-like cell line THP-1 and with human monocyte-derived macrophages (MDM). The association of M. tuberculosis with THP-1 and MDM was comparable in both the presence and the absence of serum. For both cells, serum-mediated binding was much greater than nonopsonic binding and was mediated by a heat-labile serum component. Nonopsonic binding of M. tuberculosis to both cells could be inhibited by antibodies recognizing CD11b and by mannan and glucan. Intracellular M. tuberculosis grew progressively in infected MDM and THP-1 cells. Treatment of the infected MDM and THP-1 cells with the anti-mycobacterial isoniazid resulted in the rapid killing of the intracellular mycobacteria. Differentiated, adherent THP-1 cells bound IgG and complement-coated particles at levels similar to those of MDM. However, binding of zymosan by THP-1 cells was significantly lower than that seen for MDM.

APCs express DCIR, a novel C-type lectin surface receptor containing an immunoreceptor tyrosine-based inhibitory motif

We have identified a novel member of the calcium-dependent (C-type) lectin family. This molecule, designated DCIR (for dendritic cell (DC) immunoreceptor), is a type II membrane glycoprotein of 237 aa with a single carbohydrate recognition domain (CRD), closest in homology to those of the macrophage lectin and hepatic asialoglycoprotein receptors. The intracellular domain of DCIR contains a consensus immunoreceptor tyrosine-based inhibitory motif. A mouse cDNA, encoding a homologous protein has been identified. Northern blot analysis showed DCIR mRNA to be predominantly transcribed in hematopoietic tissues. The gene encoding human DCIR was localized to chromosome 12p13, in a region close to the NK gene complex. Unlike members of this complex, DCIR displays a typical lectin CRD rather than an NK cell type extracellular domain, and was expressed on DC, monocytes, macrophages, B lymphocytes, and granulocytes, but not detected on NK and T cells. DCIR was strongly expressed by DC derived from blood monocytes cultured with GM-CSF and IL-4. DCIR was mostly expressed by monocyte-related rather than Langerhans cell related DC obtained from CD34+ progenitor cells. Finally, DCIR expression was down-regulated by signals inducing DC maturation such as CD40 ligand, LPS, or TNF-alpha. Thus, DCIR is differentially expressed on DC depending on their origin and stage of maturation/activation. DCIR represents a novel surface molecule expressed by Ag presenting cells, and of potential importance in regulation of DC function.

Testosterone induces vascular endothelial growth factor synthesis in the ventral prostate in castrated rats

PURPOSE

Recent studies suggest that the vasculature is important for the control of prostate growth. Castration induces an involution of the prostate gland and its vasculature. Replacement of testosterone stimulates endothelial cell proliferation and normalizes vascular volumes and blood flow several days before organ regrowth. Antiangiogenesis treatment inhibits the growth of prostate tumors. Understanding the regulation of the prostate vasculature may therefore provide important knowledge of the mechanisms responsible for the growth of non-malignant and malignant prostate tissue. Castration induced regression and testosterone stimulated regrowth of the prostatic vasculature have here been used to study the involvement of the angiogenic factor vascular endothelial growth factor (VEGF) and its receptors flt-1 and flk-1/KDR in the regulation of the prostatic vasculature.

MATERIALS AND METHODS

VEGF, flt-1, and flk-1/KDR levels were quantified in the rat ventral prostate following castration and testosterone replacement. Methods used were competitive RT-PCR, Western blot and immunohistochemistry.

RESULTS

VEGF mRNA and protein levels were significantly decreased by castration and testosterone treatment induced VEGF synthesis in the rat ventral prostate epithelium. Flt-1 and flk-1/KDR receptor levels were unaffected by castration and testosterone treatment.

CONCLUSIONS

Castration down regulates VEGF and testosterone induces VEGF synthesis in epithelial cells in the rat ventral prostate.

Increased expression of angiogenic factors in human colonic angiodysplasia

OBJECTIVE

Angiodysplasia of the colon is a distinct vascular abnormality characterized by focal accumulation of ectatic vessels in the mucosa and submucosa. To investigate whether angiogenesis contributes to the pathogenesis of human colonic angiodysplasia, we examined the expression of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF), and its endothelial cell receptors flt-1 and KDR.

METHODS

Immunohistochemistry was performed in sections of specimens obtained from 18 patients with colonic angiodysplasia and from eight patients with colon cancer and its adjacent, histologically normal margins of resection. We used affinity-purified rabbit polyclonal antibodies and a streptoavidin-biotin peroxidase method.

RESULTS

We detected strong immunoreactivity for vascular endothelial growth factor, homogeneously distributed in the endothelial lining of blood vessels of all sizes in 16 (89%) specimens of colonic angiodysplasia and in seven (88%) patients with colon cancer. In contrast, very limited immunoreactivity was found in normal colon. Vascular staining for flt-1 was observed in eight (44%) and one (12.5%) of the colonic angiodysplasia or colon cancer specimens, respectively, but not in normal colon. Vascular immunoreactivity for basic fibroblast growth factor was observed in seven (39%) specimens from patients with colonic angiodysplasia, whereas either very limited or no immunostaining was found in sections from specimens of patients with colon cancer and its normal margins.

CONCLUSIONS

In human colonic angiodysplasia, increased expression of angiogenic factors is likely to play a pathogenic role.

Expression of soluble VEGF receptor 2 and characterization of its binding by surface plasmon resonance

Vascular endothelial growth factor (VEGF) is an endothelial cell specific mitogen that induces angiogenesis in several pathological conditions. To block angiogenesis, soluble VEGF receptor can be used. In this study, we describe a method for high yield expression of soluble VEGF receptor 2 (sFlk-1) in a baculovirus expression system (30 mg purified sFlk-1 per L of insect cell supernatant). We also determined the binding constants for both human and mouse VEGF to the recombinant receptor by surface plasmon resonance. In this cell-free assay, under the given experimental conditions, the on-rate ka was 0.5-2.2 x 10(6) M-1s-1 and the off-rate kd was 2-4 x 10(-4) s-1 (KD = 2-6 x 10(-10) M). To our knowledge this is the first study to report on- and off-rates for the VEGF:sFlk-1 interaction. Heparin was not required for the binding of VEGF to sFlk-1 in this assay. The obtained values will serve as baseline parameters for the design of improved versions of recombinant soluble VEGF receptor.

Eicosapentaenoic acid attenuates vascular endothelial growth factor-induced proliferation via inhibiting Flk-1 receptor expression in bovine carotid artery endothelial cells

Eicosapentaenoic acid (EPA; 20:5, n-3) can restrain tumor growth and metastasis in vivo; however, the mechanism of its antitumor effect is still not fully understood. Angiogenesis is a crucial process for tumor growth and metastasis and inhibition of tumor angiogenesis can suppress tumor growth and metastasis in vivo. Vascular endothelial growth factor (VEGF) is an important angiogenic factor. In this study, we investigated the mechanisms of the inhibitory effect of EPA on VEGF-induced proliferation of bovine carotid artery endothelial (BAE) cells. BAE cells, treated with 0-5 microg/ml EPA for 48 h, displayed a dose-dependent suppression to VEGF (0.2 nM)-induced proliferation. Similar inhibitory effect was not found in BAE cells treated with arachidonic acid (AA; 20:4, n-6), or docasahexaenoic acid (DHA; 22:5, n-3). In contrast to its effect on VEGF-induced proliferation, EPA had no inhibition to basic fibroblast growth factor (bFGF, 0.2 nM)-induced proliferation in BAE cells. Both VEGF and bFGF activated mitogen-activated protein (MAP) kinase in BAE cells; however, EPA selectively inhibited VEGF-induced, but not bFGF-induced activation of MAP kinase. Flk-1 expression was inhibited dose-dependently in EPA-treated cells, whereas Flt-1 expression was increased in EPA treated cells. This in vitro inhibitory effect by EPA on Flk-1 receptor expression provides indirect evidence that one of the mechanisms of EPA for antitumor action in vivo maybe related to its antiangiogenic action.

Direct visualization of renal vascular morphogenesis in Flk1 heterozygous mutant mice

Flk1, a receptor tyrosine kinase for vascular endothelial growth factor (VEGF), is the earliest known marker for endothelial precursors (angioblasts). We examined heterozygous mice in which the Flk1 gene was partially replaced by a promoter-less LacZ insert and used beta-galactosidase histochemistry to view cells transcribing Flk1. In day 10 (E10) embryos, a Flk1-positive network surrounded the metanephric blastema, and, at E11, a vessel entered the metanephros from its ventral aspect alongside the ingrowing ureteric bud. However, aortic branches did not engage embryonic kidneys at these time points. In newborns, beta-galactosidase was localized exclusively and intensely to endothelial cells of all vessels and glomeruli. In contrast, when E12 kidneys grown in organ culture for 6 days were examined, only scattered Flk1-positive cells were seen, glomeruli were unlabeled, and vessels were absent. When organ-cultured kidneys were then grafted into wild-type anterior eye chambers, numerous Flk1-positive endothelial cells in vessels and glomeruli were found, all stemming from the graft. Image analysis showed that grafts with the most abundant glomerulo- and tubulogenesis were also those with the richest expression of Flk1. We conclude that 1) kidney microvessels precede renal artery development, 2) angioblast differentiation is arrested in organ culture but released on grafting when vasculogenesis resumes, and 3) nephrogenesis and microvessel assembly are tightly coupled in vivo.

Participation of the CD94 receptor complex in costimulation of human natural killer cells

Optimal proliferation and expansion of human NK cells require mitogenic cytokines together with cell contact-dependent co-stimulation. Production of mAb that can modulate human NK cell proliferation yielded NKH3, which recognizes the CD94 Ag. NKH3 immunoprecipitates contain approximately 70-kDa heterodimeric complexes consisting of a approximately 25-kDa glycoprotein and approximately 40- to 45-kDa molecules. Analysis by two-dimensional isoelectric focusing/SDS-PAGE suggests that several different 40- to 45-kDa species are present in the CD94 receptor complex in human NK cells. NKH3 reacted with essentially all resting NK cells, although CD94 is expressed at higher levels on the CD56(bright) (i.e., high level of CD56) CD16(dim/neg) (i.e., low level of or absent CD16) subpopulation than on the more abundant CD56(dim)CD16(bright) NK cell subset. Moreover, the Z199 mAb, which appears to recognize NKG2-A species that can form heterodimers with CD94, stained virtually all CD56(bright) NK cells, but only a subset of CD56(dim) NK cells. Ligation of CD94 augmented the proliferation of CD56(bright) NK cells in response to IL-2 or IL-15 by as much as 10-fold. Secretion of IFN-gamma by CD56(bright) NK cells stimulated with IL-2 or IL-15 was also enhanced up to 10-fold after CD94 ligation. CD94 mAb did not consistently costimulate proliferation of or IFN-gamma production by CD56(dim) NK cells cultured with IL-2 or IL-15. In contrast, irradiated K562 cells costimulated proliferation of both CD56(bright) and CD56(dim) NK cells. These results indicate that CD56(bright) and CD56(dim) NK cells can be costimulated through different receptors, which may allow these distinct NK cell subsets to be independently regulated in vivo.

HLA class I-specific inhibitory receptors in human T lymphocytes: interleukin 15-induced expression of CD94/NKG2A in superantigen- or alloantigen-activated CD8+ T cells

A fraction of human T lymphocytes, predominantly CD8+, express receptors for HLA class I molecules typical of natural killer cells (natural killer receptors or NKRs) that inhibit T cell receptor-mediated functions. Herein, we analyzed possible mechanism(s) leading to the expression of NKRs by T cells responding to superantigens or allogeneic cells in vitro. We show that, in the presence of interleukin 15 (IL-15), T cells (depleted of NKR+ cells) responding to toxic shock syndrome toxin 1 de novo express CD94, a molecule that is part of a heterodimeric NKR with a broad specificity for different HLA class I alleles. Maximal CD94 expression occurred when IL-15 was added shortly after the cells were placed into culture, and CD94 expression started 4-6 days after addition of IL-15. Although both CD4+ and CD8+ cells expressed CD94, the simultaneous expression of NKG2A (i.e., the other component of the CD94/NKG2A inhibitory NKR) was confined to CD8+ cells. Similar data were obtained in T cell populations activated in mixed lymphocyte cultures in the presence of IL-15. The expression of CD94/NKG2A led to an impairment of allo-specific cytolytic activity by mixed lymphocyte culture-derived T cell populations or clones. Remarkably, cytolysis could be restored by the addition of anti-CD94 mAb, i.e., by masking the inhibitory NKRs.

Expression and function of NKRP1A molecule on human monocytes and dendritic cells

In this study, we analyzed the expression and function of the lymphocyte surface lectin NKRP1A on peripheral blood monocytes (Mo) or Mo and dendritic cells (DC) derived from thymic and bone marrow precursors. De novo expression of NKRP1A and CD14 molecules was detected upon culture of CD2- CD3- CD14- CD16- CD1a- NKRP1A- immature thymic precursors for 7 days in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF). Under these culture conditions, by day 21, a fraction of cells had lost CD14 and acquired both CD80 (B7.1) and CD86 (B7.2) molecules. These cells displayed a DC-like morphology and were surface NKRP1A positive. CD34+ NKRP1A- CD14- precursors, isolated from bone marrow and cultured in the presence of GM-CSF, also expressed both NKRP1A and CD14: these antigens were newly expressed on about one third of cells which had lost the CD34 precursor marker. In addition, NKRP1A was constitutively present on resting CD14+ peripheral blood Mo. When these cells were cultured in the presence of GM-CSF, the resulting DC population retained the expression of NKRP1A and acquired CD80, while they lost the CD14 antigen. Functional analysis revealed that the engagement of NKRP1A molecule leads to a strong intracellular calcium ([Ca2+]i) increase both in resting peripheral blood Mo and in vitro-derived DC. [Ca2+]i increase was mainly due to extracellular calcium influx, as it was completely abrogated by the addition of EGTA. More importantly, the engagement of the NKRP1A molecule induced interleukin (IL)-1 beta and IL-12 production by resting Mo and DC, respectively. Altogether these data indicate that NKRP1A lectin is present at the surface of Mo and DC and may play a relevant role in the activation and function of both cell types.

Halting angiogenesis suppresses carcinoma cell invasion

The importance of angiogenesis in malignant tumor growth has been interpreted mainly in terms of oxygen and nutrient supply. Here we demonstrate its fundamental role for tumor invasion of malignant human keratinocytes in surface transplants on nude mice. Distinct patterns of angiogenesis and vascular endothelial growth factor receptor-2 (VEGFR-2) expression allowed us to distinguish between benign and malignant cells. Functional inactivation of VEGF-R2 by a blocking antibody disrupted ongoing angiogenesis and prevented invasion of malignant cells, without reducing tumor cell proliferation. The reversion of a malignant into a benign phenotype by halting angiogenesis demonstrates a significant function of vascular endothelium for tumor invasion.

Induction of germinal center B cell markers in vitro by activated CD4+ T lymphocytes: the role of CD40 ligand, soluble factors, and B cell antigen receptor cross-linking

Following primary immunization, B cells differentiate to memory cells with help from T cells. The specialized path to B cell memory takes place in lymphoid germinal centers (GC), where mouse B cells up-regulate peanut agglutinin receptor (PNA-R), B7-2 (CD86), and MHC class II expression. Using an in vitro culture system, we have studied how different stimuli can enhance the expression of these markers. We show that PNA-R is up-regulated when splenic B cells are cocultured with anti-CD3-stimulated CD4+, but not CD8+, T cells and that this process requires CD40-CD40 ligand engagement. Increased expression of PNA-R is also inducible with supernatants of activated CD4+, but not CD8+, T cells in combination with mitogenic signals, such as anti-Ig, anti-CD40, or LPS, but not by either supernatants or mitogenic signals alone. Unlike with PNA-R, increased expression of B7-2 and I-A occurs in response to activated T cells of either CD4+ and CD8+ subsets or their supernatants, does not require CD40 costimulation, and is readily induced with mitogenic signals alone. Taken together, these results indicate that PNA-R up-regulation has more restricted signaling requirements than B7-2 or I-A, and that it can be induced/maintained by Ag receptor cross-linking or CD40 engagement, as long as there is an appropriate cytokine milieu.

A molecular epidemiological approach to the study of expression of a metastasis marker in primary melanomas and its correlation with individual patient's risk of recurrence or metastasis

Tumour cells in malignant melanomas express molecules associated with tumour progression; however, up until now, no marker has been able to identify the tumour cells from which metastases are derived. It has recently been shown that in human melanoma cell lines, populations expressing peanut agglutinin (PNA)-binding glycoproteins are able to generate metastases, and that such cells do exist in primary human melanomas, their presence being associated with the degree of local invasion that governs the metastasis risk. To further investigate the correlation between the expression of PNA-binding glycoconjugates by cells from primary melanomas and the patient's individual risk of recurrence or metastasis, a molecular epidemiological approach employing histochemical techniques within a case-control design was developed. The main objective of this study is to determine whether an histochemical staining with the lectin PNA of cells in the primary lesion is associated with an increased risk of local recurrence of metastasis, and with survival, independently of Breslow's tumour thickness. The study comprises the comparison of the PNA labelling index and of the type and intratumour location of the staining as a function of clinical outcome in two matched series of patients with known clinical outcome: patients who had died at 5 years and patients alive at 5 years (to assess association with survival), and patients who experienced a recurrence within the first 5 years and patients alive without recurrence at 5 years (to assess association with risk of recurrence). A matched case-control design was used with a variable number of controls matched to each case. Apart from age (+/-5 years), sex and centre where diagnosis was made, matching was made on histogenetic type and primary tumour thickness (four categories being considered: <0.75, 0.76-1.5, 1.51-3 and >3 mm).

Hypoxia and cobalt stimulate vascular endothelial growth factor receptor gene expression in rats

This study aimed to examine the influence of acute tissue hypo-oxygenation on the expression of the vascular endothelial growth factor (VEGF) receptor genes. To this end male Sprague-Dawley rats were exposed to different hypoxic conditions such as 10% or 8% oxygen, 0.1% carbon monoxide and cobalt chloride (60 mg/kg) for 6 h and the abundance of flt-1, flt-4 and flk-1 mRNA in lungs and livers was determined by RNase protection assay. The relative proportions of flt-1, flt-4 and flk-1 were 10:2.5:1 and 10:10:2 in normoxic lungs and livers, respectively. It was found that 8% but not 10% oxygen increased flt-1 mRNA two- to three-fold in both organs, whilst flt-4 and flk-1 mRNA were not changed by acute inspiratory hypoxia. Carbon monoxide inhalation also increased flt-1 mRNA but not flt-4 or flk-1 mRNA in both organs. Subcutaneous cobalt administration increased flt-1 mRNA in the livers only, whilst flt-4 and flk-1 mRNA remained unchanged. These findings show that acute tissue hypo-oxygenation is a rather selective stimulus for flt-1 gene expression. The efficiency of the different manoeuvres applied to stimulate flt-1 gene expression is rather similar to the stimulation of erythropoietin gene expression. It is not unreasonable to assume, therefore, that the oxygen-dependent regulation of both genes at the cellular level has significant similarities.

Downregulation of vascular endothelial growth factor receptors by tumor necrosis factor-alpha in cultured human vascular endothelial cells

Vascular endothelial growth factor (VEGF) potently stimulates angiogenesis, whereas TNF-alpha has both pro- and anti-angiogenic activity. By measuring thymidine uptake, we found that TNF-alpha blocked a 2.3-fold increase in DNA synthesis induced by VEGF in human endothelial cells. To explore the possibility that the two interact to regulate endothelial cell proliferation, we examined the effect of TNF-alpha on VEGF receptor expression. In venous and arterial endothelial cells, TNF-alpha potently reduced mRNA transcripts of the two VEGF receptors (KDR/flk-1 and flt-1) in a dose- and time-dependent fashion. TNF-alpha at 1 ng/ml induced maximal inhibition of mRNA expression, which fell by approximately 70% after 24 h. TNF-alpha treatment did not significantly affect the KDR/flk-1 half-life but did decrease its rate of transcription to 40% of control. The decrease in KDR/flk-1 mRNA depended partially on new protein synthesis and was abolished by phorbol ester pretreatment. TNF-alpha decreased the amount of 35S-labeled KDR/flk-1 immunoprecipitated by an antibody specific for KDR/flk-1 to 18% of control. We conclude that TNF-alpha downregulates expression of both VEGF receptors in human endothelial cells and that this effect is transcriptional (at least for KDR/flk-1). These data support the hypothesis that TNF-alpha exerts its antiangiogenic effect in part by modulating the VEGF-specific angiogenic pathway.

Influence of culture media and multidrug resistance on the wheat germ agglutinin (WGA) glycocytochemical expression of two human glioblastoma cell lines

Over the last two decades, many studies carried out with the aid of lectins have firmly established that cell glycans usually change in the course of the normal processes of growth and development, as well as in pathological situations. We describe here the in vivo binding expression of wheat germ agglutinin (WGA) to the U87 and U373 human glioblastoma cell lines exposed to various culture media i.e., media supplemented with either 10% (FCS10) or 1% (FCS1) fetal calf serum with or without 10 n Mol/l 17 beta-oestradiol (E2). After exposure to chemotherapeutic agents, the resistant variants (CR) developed by the two cell lines were also investigated. The quantitative cytochemical assessment of WGA binding was assessed by means of a cell image processor, which was also used to determine ploidy level (on Feulgen-stained nuclei) by means of DNA histogram typing (DHT). Our results clearly demonstrate that when U373 cells are cultured with E2, this steroid can modify the expression of WGA binding, whereas U87 cells were unaffected. Similarly, lowering the FCS level enhanced the WGA binding of the U373 cell line. Multidrug-resistant cell variants were associated with both aneuploidy and a dramatic decrease in cytochemical WGA expression.

Possible participation of autocrine and paracrine vascular endothelial growth factors in hypoxia-induced proliferation of endothelial cells and pericytes

Hypoxia is the principal factor that causes angiogenesis. These experiments were conducted to explore how it induces the proliferation of vascular cells, a key step in angiogenesis. Human umbilical vein endothelial cells and bovine retinal pericytes were grown in controlled atmosphere culture chambers containing various concentrations of oxygen. The numbers of both endothelial cells and pericytes increased significantly under hypoxic conditions; the O2 concentrations that achieved maximal growth promotion were 10% for endothelial cells and 2.5% for pericytes. Quantitative reverse transcription-polymerase chain reaction analysis revealed that mRNAs coding for the secretory forms of vascular endothelial growth factor (VEGF), a mitogen specific to endothelial cells, were present in both endothelial cells and pericytes and that their levels increased significantly in the two cell types as the atmospheric O2 concentration decreased. The two genes for VEGF receptors, kinase insert domain-containing receptor (kdr) and fms-like tyrosine kinase 1 (flt1), were found to be constitutively expressed in endothelial cells, and their relative mRNA levels were ranked in that order. On the other hand, only flt1 mRNA was detected in pericytes under hypoxic conditions. Furthermore, most antisense oligodeoxyribonucleotides complementary to VEGF mRNAs efficiently inhibited DNA synthesis in endothelial cells cultured under hypoxic conditions. These results indicate that autocrine and paracrine VEGFs may take part in the hypoxia-induced proliferation of endothelial cells.

A novel promoter for vascular endothelial growth factor receptor (flt-1) that confers endothelial-specific gene expression

The human transmembrane fms-like receptor tyrosine kinase Flt-1 is one of the receptors for vascular endothelial growth factor, a growth factor which induces endothelial proliferation and vascular permeability. Flt-1 is expressed specifically in endothelium and is likely to play a role in tumor angiogenesis and embryonic vascularization. To elucidate the molecular basis for the endothelial specific expression of Flt-1, the promoter region has been isolated and functionally characterized. The promoter region contains a TATA box, a GC-rich region, and putative transcription factor binding elements such as cAMP response element binding protein/activating transcription factor (CREB/ATF) and ets. Adenovirus-mediated transient expression of the flt-1 promoter/luciferase fusion gene in endothelial cells and other cell types demonstrated that a 1-kilobase fragment of the 5'-flanking region of flt-1 is involved in the endothelial-specific expression. A CREB/ATF element was found to be essential for basal transcription of the flt-1 expression. In addition, we also showed that the first intron negatively regulates flt-1 promoter activity. The flt-1 promoter will be useful in functional studies on the regulation of endothelial-specific gene expression and also as a tool in targeting the expression of exogenously introduced genes to the endothelium.

A histochemical study of the distribution of lectin binding sites in the developing oocytes of the lancelet Branchiostoma belcheri

The distribution of carbohydrate moieties in lancelet (Branchiostoma belcheri) oocytes has been studied at different stages of development, using a peroxidase-labeled lectin incubation technique, the PAS-reaction and Alcian Blue staining. Binding sites of 5 lectins, indicating the presence of different sugar moieties (Wheat germ agglutinin (WGA) for N-acetylglucosamine, Concanavalin A (Con A) for glucose/mannose, Helix pomatia agglutinin (HPA) for N-acetyl-D-galactosamine, Ricinus communis agglutinin (RCA-I) for galactose and Ulex europaeus agglutinin (UEA-I) for fucose), were identified and were shown to undergo considerable variation during oocyte development. In the previtellogenic stage, HPA, RCA-I and UEA-I were not identified on the oocyte surface, but WGA and Con A gave strongly positive reactions at this site. In the cytoplasm, 4 lectins (Con A, HPA, RCA-I and UEA-I) gave a weak or moderate reaction, and Con A was also observed in the perinuclear region. In vitellogenic oocytes, these 4 lectins were found to also bind to the nuclear envelope, karyoplasm and nucleolus, and, with the exception of Con A, could also be found in the nuclei of more mature stages. The cytoplasmic yolk granules and Golgi vesicles of the vitellogenic oocyte, were moderately positive for Con A, HPA, RCA-I and UEA-I, but HPA, RCA-I and UEA-I were only weakly bound at the oocyte surface. In mature oocytes, all 5 lectins bound moderately or strongly to yolk granules and cell surface. HPA, RCA-I and UEA-I bound moderately or strongly to various nuclear compartments.(ABSTRACT TRUNCATED AT 250 WORDS)

IL-4 induction of VCAM-1 on endothelial cells involves activation of a protein tyrosine kinase

IL-4 triggers tyrosine phosphorylation of a single major substrate (M(r) 145,000) in cultured human endothelial cells (EC) as detected by Western blot of whole cell lysates or of anti-phosphotyrosine immunoprecipitates. Phosphorylation of this substrate depends on IL-4 concentration (appearance at 10 U/ml, maximal at 300 to 1000 U/ml) and time of treatment (onset by 1 min, peak at 5 to30 min, duration of 60 to 120 min). Immunoprecipitation with specific mAb identified the phosphorylated substrate as the IL-4R. Treatment of EC with IL-4 alone causes only a small increase in the expression of vascular cell adhesion molecule-1 (VCAM-1), but IL-4 significantly augments the level of VCAM-1 expression induced by PMA. Pretreatment of EC with herbimycin A (0.5 to 1.0 microgram/ml) for 12 to 18 h abrogates both IL-4-induced tyrosine phosphorylation and IL-4-augmented VCAM-1 expression. This concentration of herbimycin A does not inhibit and may augment PMA-induced VCAM-1 expression in replicate wells. These observations suggest that IL-4 induction of VCAM-1 in EC involves the activation of an as yet unidentified protein tyrosine kinase that phosphorylates the IL-4R.

Expression patterns of the novel receptor-like tyrosine kinase, DDR, in human breast tumours

Using a reverse transcriptase-polymerase chain reaction based differential screening procedure, we have identified the discoidin domain receptor as a protein tyrosine kinase that is expressed in lymph nodes containing breast tumour metastases. By Northern blotting and in situ hybridisation we have demonstrated the expression of the discoidin domain receptor in human primary breast tumour samples, metastasis-containing lymph nodes and a number of normal tissues. Direct comparison of malignant breast and adjacent normal epithelial tissue revealed over expression in the tumour cells.

IL-4R alpha and gamma chain expression in LPS- and IL-4-stimulated MONO-MAC-6 cells

Short-term stimulation of peripheral blood monocytes (PBMo) and cells of the monocytic cell line MONO-MAC-6 with lipopoly-saccharide (LPS) induces high tumor necrosis factor (TNF)alpha mRNA levels. In contrast to the results obtained with primary cells, this effect could not be inhibited by preincubating the cell line with recombinant human interleukin-4 (rh IL-4). This deficiency in response to the cytokine was not caused by a general unresponsiveness of MONO-MAC-6 cells to IL-4. Thus, the expression of the monocyte-associated differentiation markers CD14 and monocyte-specific esterase (MSE), upregulated by long-term stimulation with LPS, could be decreased by IL-4. Long-term LPS treatment apparently induced IL-4 responsiveness of the cell line. While IL-4R alpha mRNA was upregulated about 3-fold, this positive effect was not apparent at the cell surface protein level. In contrast to the constitutive alpha chain expression, the IL-4R gamma chain expression could not be detected with a specific mAb nor by Northern blot analysis. However, reverse transcriptase polymerase chain reaction (RT-PCR) demonstrated the presence of low-level IL-4R gamma chain mRNA in the cell line. We suggest that the low reactivity of the cells to IL-4 might be correlated with the low expression of the gamma chain.

Vascular endothelial growth factor and glioma angiogenesis: coordinate induction of VEGF receptors, distribution of VEGF protein and possible in vivo regulatory mechanisms

We have previously suggested that tumor angiogenesis in human gliomas is regulated by a paracrine mechanism involving vascular endothelial growth factor (VEGF) and flt-1 (VEGF-receptor 1). VEGF, an endothelial-cell-specific mitogen, is abundantly expressed in glioma cells which reside along necrotic areas, whereas flt-1, a tyrosine-kinase receptor for VEGF, is expressed in tumor endothelial cells, but not in endothelial cells in normal adult brain. Recently, a second tyrosine-kinase receptor which binds VEGF with high affinity, designated KDR or flk-1, has been described. We performed in situ hybridization for VEGF mRNA, flt-1 mRNA and KDR mRNA on serial sections of normal brain, low-grade and high-grade glioma specimens. We show that KDR mRNA is co-expressed with flt-1 in vascular cells in glioblastoma but not in low-grade glioma. Since flt-1 and KDR are not expressed in endothelial cells in the normal adult brain, the coordinate up-regulation of 2 receptors for VEGF appears to be a critical event which controls tumor angiogenesis. Immunocytochemistry with a monoclonal anti-VEGF antibody revealed significant amounts of VEGF protein in the same glioma cells that expressed VEGF mRNA. The largest amount of VEGF immunoreactivity, however, was detected on the vasculature of glioblastomas, the site where VEGF exerts its biological functions. These findings suggest that VEGF is produced and secreted by glioma cells and acts on tumor endothelial cells which express VEGF receptors. To further characterize VEGF-producer cells in vivo, we investigated cellular proliferation, immunoreactivity to the p53 tumor-suppressor gene product and epidermal-growth-factor-receptor (EGFR) expression on serial sections by immunocytochemistry. VEGF-producer cells did not show increased cellular proliferation, p53 immunoreactivity or EGFR immunoreactivity as compared with glioma cells which did not express VEGF. Our studies therefore do not demonstrate evidence for a growth advantage of VEGF-producer cells in vivo or VEGF induction by p53 mutation or EGFR over-expression.

Interaction of the c-fes proto-oncogene product with the interleukin-4 receptor

Interleukin-4 (IL-4) regulates proliferation and differentiation of a variety of hematopoietic cell lineages through binding to the IL-4 receptor (IL-4R). Recently, we have demonstrated that IL-4 induces tyrosine phosphorylation of several proteins including the IL-4R and also induces association of phosphatidylinositol-3 kinase with the IL-4R. Since IL-4 induces tyrosine phosphorylation, we speculated that some tyrosine kinase may associate with the IL-4R. In this study, we demonstrate that IL-4 induces tyrosine phosphorylation of a protein closely related to, or identical to the c-fes protooncogene-encoded protein tyrosine kinase (FES). Furthermore, tyrosine phosphorylated FES or the closely related protein is found associated with the IL-4R. We also demonstrate that FES associates with the IL-4R in COS7 cells transfected with cDNA expression plasmids encoding these two proteins and in transfected COS7 cells IL-4 augments association of FES with the IL-4R and tyrosine phosphorylation of both FES and the IL-4R. Through a deletion analysis of the IL-4R we have identified a putative FES-binding site in the cytoplasmic domain of the IL-4R.

The interleukin-4 receptor: signal transduction by a hematopoietin receptor

Over the last several years, the receptors for numerous cytokines have been molecularly characterized. Analysis of their amino acid sequences shows that some of these receptors bear certain motifs in their extracellular domains that define a family of receptors called the Hematopoietin receptor superfamily. Significant advances in characterizing the structure, function, and mechanisms of signal transduction have been made for several members of this family. The purpose of this review is to discuss the recent advances made for one of the family members, the interleukin (IL) 4 receptor. Other receptor systems have recently been reviewed elsewhere. The IL-4 receptor consists of, at the minimum, the cloned 140 kDa IL-4-binding chain with the potential for associating with other chains. The IL-4 receptor transduces its signal by activating a tyrosine kinase that phosphorylates cellular substrates, including the receptor itself, and the 170 kDa substrate called 4PS. Phosphorylated 4PS interacts with the SH2 domain of the enzyme PI-3'-kinase and increases its enzymatic activity. These early events in the IL-4 receptor initiated signaling pathway may trigger a series of signals that will ultimately lead to an IL-4 specific biologic outcome.

Vortex flow filtration of mammalian and insect cells

The use of vortex flow filtration for harvesting cells or conditioned medium from large scale bioreactors has proven to be an efficient, low shear method of cell concentration and conditioned medium clarification. Several 8-10 L batches of the human histiocytic lymphoma U-937 cell line (ATCC CRL 1593) were concentrated to less than 1 L by vortex flow filtration through a 3.0 microns membrane. An aggressive filtration regimen caused a 17% loss of cell viability and a 32% loss of IL-4 receptor binding capacity when compared to a batch centrifuged control. A reduction of the rotor speed from 1500 to 500 RPM and reduction of system back pressure from 10 to 0 PSIG resulted in cell viability and IL-4 binding capacity comparable to the control. Several 10 L batches of baculovirus infected Sf-9 cells were also concentrated to less than 1 L by vortex flow filtration through a 3.0 microns membrane. SDS-PAGE analysis of filtrate samples showed that aggressive filtration caused cell damage which led to contamination of the process stream by cellular lysate. When rotor speed was reduced to 500 RPM and system back pressure was reduced to 0 PSIG, the amount of contaminating lysate proteins in filtrate samples was comparable to a batch centrifuged control.

Tumor necrosis factor upregulates interleukin-4 receptors on murine sarcoma cells

We have previously shown that murine solid tumor cells express high affinity IL-4 receptors (IL-4R) which are internalized after binding to ligand. In the present study, we have examined the regulation of IL-4R by TNF. We demonstrate that TNF upregulated the expression of IL-4R on murine MCA-106 sarcoma cells. Maximum upregulation of IL-4R surface expression occurred after 24 h, whereas, maximum elevation in IL-4R mRNA levels was observed after only 4 hours of TNF treatment. This increase in mRNA levels for IL-4R occurred in a dose dependent manner. As little as 0.83 ng/ml of TNF significantly upregulated mRNA levels, whereas maximum effect was obtained with 83 ng/ml TNF. IL-4 receptor density was increased in response to TNF, no effect on IL-4R affinity was observed. Cycloheximide and Actinomycin D treatment decreased the surface expression of IL-4R by 50% in about 2 h and 7 h, respectively, in both TNF treated and untreated cells indicating the half life for the IL-4R protein expression. These studies may help understand the mechanism of cytokine interaction on tumor cells.

Immunostaining of interleukin-4 receptor on human renal cell carcinoma

Immunocytochemistry on three primary cultures of RCC tumor cells and immunohistochemistry on five frozen sections of RCC were performed by utilizing a monoclonal antibody (M-57) to human IL-4R. We found that all three RCC tumor cell cytospin preparations stained with anti-IL-4R monoclonal antibody. Tumor cells stained with IgG control did not show any staining. Similarly, five histologically proven RCC frozen sections prepared from nephrectomy specimens had moderate to intense immunoreactivity to IL-4 receptor antibody. RCC sections stained with normal mouse IgG2b showed only background type staining. Frozen section prepared from uninvolved kidney showed only nonspecific staining. A flow cytometric analysis of primary cultures of RCC tumor cells confirmed the immunohistochemical data and showed that almost all of the cells were positive for IL-4 receptor expression. These results demonstrate that human RCC express immunoreactive IL-4 receptors, which may be a target for diagnosis and therapy by an anti-IL-4 receptor antibody fused to toxins or radionuclides or alternatively by IL-4 toxins.

Production of soluble IL-4 receptors by murine spleen cells is regulated by T cell activation and IL-4

Many cytokine receptors exist naturally as both membrane-bound and soluble forms. Whereas the membrane receptors have an obvious role in signal transduction, the putative immunoregulatory role played by the soluble receptors remains unclear. Although natural forms of soluble IL-4R (sIL-4R) are known to be present in the biologic fluids of normal mice, the mechanisms regulating the production of sIL-4R have not been characterized. In this study, we have developed an ELISA that allows the measurement of sIL-4R without interference from endogenous IL-4, and have analyzed the effect of cellular activation and several cytokines on the secretion of sIL-4R by murine splenic cells. Although normal spleen cells in culture produced low, but detectable levels of sIL-4R under basal conditions, stimulation with the T cell-mitogens, Con A or soluble anti-CD3 antibodies, caused a 10- to 40-fold increase in the production of sIL-4R. Stimulation of B lymphocytes with LPS, however, did not result in significant up-regulation of sIL-4R secretion. Moreover, IL-4, but not other cytokines, was also a potent inducer of sIL-4R production by spleen cells, even in the absence of other stimuli. Blocking experiments with an anti-IL-4 antibody, 11B11, demonstrated that the effect of T cell-mitogens is partially mediated by endogenously produced IL-4. Cell depletion experiments suggested that although the effect of T cell-mitogens was dependent on the presence of viable T cells, all major cell types including T cells, B cells, and macrophages, either resting or activated, were able to up-regulate their secretion of sIL-4R in response to IL-4. Unlike many activities of IL-4, the secretion of sIL-4R by IL-4-stimulated splenic cells was not antagonized by IFN-gamma. These results suggest that the production of sIL-4R is regulated by stimuli leading to T cell activation and IL-4 secretion and are consistent with sIL-4R having an important role in the regulation of IL-4 activity in vivo.

Interferon-gamma antagonizes interleukin-6-induced expression of interleukin-4 receptors in murine myeloid cells by a transcriptional mechanism

The murine myeloid leukemia cell line M1 induced by interleukin-6 (IL-6) is a model system to study the differentiation of blast cells to mature macrophages. We have recently shown that IL-6 induces the expression of the IL-4 receptor (IL-4R) in these cells. In the present study we investigate the mechanism of action of interferon-gamma (IFN-gamma), an antagonist of IL-4 in numerous cells and a cofactor in both induction and suppression of myelopoiesis, on the expression of IL-4R. Flow cytometry shows that IFN-gamma downregulates the IL-6-induced expression of IL-4R whereas it has no such effect on the high-affinity receptors for monomeric IgG2a (Fc gamma RI). As demonstrated by Scatchard analysis, the number of IL-4R decreases by more than 50% after IFN-gamma treatment whereas the receptor affinity remains unchanged. Northern analysis shows that this decrease is paralleled by a decrease in IL-4R mRNA but not Fc gamma RI or lysozyme mRNA. Nuclear run-on analysis shows that IFN-gamma suppresses the IL-6-induced transcription of the IL-4R gene, whereas actinomycin-D chase experiments showed no change of IL-4R mRNA stability. Furthermore, the production of soluble IL-4R protein is suppressed by IFN-gamma as well. These data explain how IL-4R can be modulated by IFN-gamma in myeloid cells and are consistent with the myelosuppressive capacity of IFN-gamma.