Showing papers by "Kari Alitalo published in 1998"

Vascular endothelial growth factor D (VEGF-D) is a ligand for the tyrosine kinases VEGF receptor 2 (Flk1) and VEGF receptor 3 (Flt4)

Abstract: We have identified a member of the VEGF family by computer-based homology searching and have designated it VEGF-D. VEGF-D is most closely related to VEGF-C by virtue of the presence of N- and C-terminal extensions that are not found in other VEGF family members. In adult human tissues, VEGF-D mRNA is most abundant in heart, lung, skeletal muscle, colon, and small intestine. Analyses of VEGF-D receptor specificity revealed that VEGF-D is a ligand for both VEGF receptors (VEGFRs) VEGFR-2 (Flk1) and VEGFR-3 (Flt4) and can activate these receptors. However, VEGF-D does not bind to VEGFR-1. Expression of a truncated derivative of VEGF-D demonstrated that the receptor-binding capacities reside in the portion of the molecule that is most closely related in primary structure to other VEGF family members and that corresponds to the mature form of VEGF-C. In addition, VEGF-D is a mitogen for endothelial cells. The structural and functional similarities between VEGF-D and VEGF-C define a subfamily of the VEGFs.

Cardiovascular Failure in Mouse Embryos Deficient in VEGF Receptor-3

Abstract: Vascular endothelial growth factor (VEGF) is a key regulator of blood vessel development in embryos and angiogenesis in adult tissues. Unlike VEGF, the related VEGF-C stimulates the growth of lymphatic vessels through its specific lymphatic endothelial receptor VEGFR-3. Here it is shown that targeted inactivation of the gene encoding VEGFR-3 resulted in defective blood vessel development in early mouse embryos. Vasculogenesis and angiogenesis occurred, but large vessels became abnormally organized with defective lumens, leading to fluid accumulation in the pericardial cavity and cardiovascular failure at embryonic day 9.5. Thus, VEGFR-3 has an essential role in the development of the embryonic cardiovascular system before the emergence of the lymphatic vessels.

Vascular endothelial growth factor C induces angiogenesis in vivo

Abstract: Vascular endothelial growth factor C (VEGF-C) recently has been described to be a relatively specific growth factor for the lymphatic vascular system. Here we report that ectopic application of recombinant VEGF-C also has potent angiogenic effects in vivo. VEGF-C is sufficiently potent to stimulate neovascularization from limbal vessels in the mouse cornea. Similar to VEGF, the angiogenic response of corneas induced by VEGF-C is intensive, with a high density of new capillaries. However, the outgrowth of microvessels stimulated by VEGF-C was significantly longer than that induced by VEGF. In the developing embryo, VEGF-C was able to induce branch sprouts from the established blood vessels. VEGF-C also induced an elongated, spindle-like cell shape change and actin reorganization in both VEGF receptor (VEGFR)-2 and VEGFR-3-overexpressing endothelial cells, but not in VEGFR-1-expressing cells. Further, both VEGFR-2 and VEGFR-3 could mediate proliferative and chemotactic responses in endothelial cells on VEGF-C stimulation. Thus, VEGF-C may regulate physiological angiogenesis and participate in the development and progression of angiogenic diseases in addition to lymphangiogenesis.

Vascular endothelial growth factor B (VEGF-B) binds to VEGF receptor-1 and regulates plasminogen activator activity in endothelial cells.

Abstract: The vascular endothelial growth factor (VEGF) family has recently expanded by the identification and cloning of three additional members, namely VEGF-B, VEGF-C, and VEGF-D. In this study we demonstrate that VEGF-B binds selectively to VEGF receptor-1/Flt-1. This binding can be blocked by excess VEGF, indicating that the interaction sites on the receptor are at least partially overlapping. Mutating the putative VEGF receptor-1/Flt-1 binding determinants Asp63, Asp64, and Glu67 to alanine residues in VEGF-B reduced the affinity to VEGF receptor-1 but did not abolish binding. Mutational analysis of conserved cysteines contributing to VEGF-B dimer formation suggest a structural conservation with VEGF and platelet-derived growth factor. Proteolytic processing of the 60-kDa VEGF-B186 dimer results in a 34-kDa dimer containing the receptor-binding epitopes. The binding of VEGF-B to its receptor on endothelial cells leads to increased expression and activity of urokinase type plasminogen activator and plasminogen activator inhibitor 1, suggesting a role for VEGF-B in the regulation of extracellular matrix degradation, cell adhesion, and migration.

Vascular endothelial growth factors VEGF-B and VEGF-C are expressed in human tumors

Abstract: The growth of solid tumors is dependent on angiogenesis, the formation of new blood vessels. Vascular endothelial growth factor (VEGF) is a secreted endothelial-cell-specific mitogen. We have recently characterized two novel endothelial growth factors with structural homology to VEGF and named them VEGF-B and VEGF-C. To further define the roles of VEGF-B and VEGF-C, we have studied their expression in a variety of human tumors, both malignant and benign. VEGF-B mRNA was detected in most of the tumor samples studied, and the mRNA and the protein product were localized to tumor cells. Endothelial cells of tumor vessels were also immunoreactive for VEGF-B, probably representing the binding sites of the VEGF-B polypeptide secreted by adjacent tumor cells. VEGF-C mRNA was detected in approximately one-half of the cancers analyzed. Via in situ hybridization, VEGF-C mRNA was also localized to tumor cells. All lymphomas studied contained low levels of VEGF-C mRNA, possibly reflecting the cell-specific pattern of expression of the VEGF-C gene in the corresponding normal cells. The expression of VEGF-C is associated with the development of lymphatic vessels, and VEGF-C could be an important factor regulating the mutual paracrine relationships between tumor cells and lymphatic endothelial cells. Furthermore, VEGF-C and VEGF-B can, similarly to VEGF, be involved in tumor angiogenesis.

Lymphatic Endothelium and Kaposi's Sarcoma Spindle Cells Detected by Antibodies against the Vascular Endothelial Growth Factor Receptor-3

Abstract: Lymphatic vessels have been difficult to study in detail in normal and tumor tissues because of the lack of molecular markers. Here, monoclonal antibodies against the extracellular domain of the vascular endothelial growth factor-C receptor that we have named VEGFR-3 were found to specifically stain endothelial cells of lymphatic vessels and vessels around tumors such as lymphoma and in situ breast carcinoma. Interestingly, the spindle cells of several cutaneous nodular AIDS-associated Kaposi's sarcomas and the endothelium around the nodules were also VEGFR-3 positive. The first specific molecular marker for the lymphatic endothelium should provide a useful tool for the analysis of lymphatic vessels in malignant tumors and their metastases and the cellular origin and differentiation of Kaposi's sarcomas.

Peripheral Blood Platelets Express VEGF-C and VEGF which Are Released during Platelet Activation

Abstract: VEGF-C is a recently characterised endothelial growth factor structurally related to vascular endothelial growth factor (VEGF). We studied the expression of VEGF-C and VEGF in the cells of peripheral blood and in the umbilical cord blood CD 34+ cells, representing haematopoietic progenitor cells. Expression of VEGF-C was detected in the CD34+ cells. In peripheral blood VEGF-C mRNA was restricted to platelets and T-cells. In contrast to the expression pattern of VEGF-C, VEGF mRNA was detected in all peripheral blood cell fractions studied, and also in CD34+ cells. VEGF-C mRNA was also detected in fresh bone marrow samples of acute leukaemia patients, but the expression did not show lineage specificity. VEGF-C and VEGF polypeptides were present in platelets and they were released from activated platelets together with the release of b-thromboglobulin, suggesting that VEGF-C and VEGF reside in the a-granules of platelets. VEGF-C and VEGF, released from activated platelets, may have a role in angiogenesis during wound healing, and possibly also in other pathological conditions, such as atherosclerosis, tumour growth, and metastasis formation.

Expression of the Vascular Endothelial Growth Factor C Receptor VEGFR-3 in Lymphatic Endothelium of the Skin and in Vascular Tumors

Abstract: It is difficult to identify lymph vessels in tissue sections by histochemical staining, and thus a specific marker for lymphatic endothelial cells would be more practical in histopathological diagnostics. Here we have applied a specific antigenic marker for lymphatic endothelial cells in the human skin, the vascular endothelial growth factor receptor-3 (VEGFR-3), and show that it identifies a distinct vessel population both in fetal and adult skin, which has properties of lymphatic vessels. The expression of VEGFR-3 was studied in normal human skin by in situ hybridization, iodinated ligand binding, and immunohistochemistry. A subset of developing vessels expressed the VEGFR-3 mRNA in fetal skin as shown by in situ hybridization and radioiodinated vascular endothelial growth factor (VEGF)-C bound selectively to a subset of vessels in adult skin that had morphological characteristics of lymphatic vessels. Monoclonal antibodies against the extracellular domain of VEGFR-3 stained specifically endothelial cells of dermal lymph vessels, in contrast to PAL-E antibodies, which stained only blood vessel endothelia. In addition, staining for VEGFR-3 was strongly positive in the endothelium of cutaneous lymphangiomatosis, but staining of endothelial cells in cutaneous hemangiomas was weaker. These results establish the utility of anti-VEGFR-3 antibodies in the identification of lymphovascular channels in the skin and in the differential diagnosis of skin lesions involving lymphatic or blood vascular endothelium.

Vascular endothelial growth factor (VEGF)-C synergizes with basic fibroblast growth factor and VEGF in the induction of angiogenesis in vitro and alters endothelial cell extracellular proteolytic activity

Abstract: Vascular endothelial growth factor-C (VEGF-C) is a recently characterized member of the VEGF family of angiogenic polypeptides. We demonstrate here that VEGF-C is angiogenic in vitro when added to bovine aortic or lymphatic endothelial (BAE and BLE) cells but has little or no effect on bovine microvascular endothelial (BME) cells. As reported previously for VEGF, VEGF-C and basic fibroblast growth factor (bFGF) induced a synergistic in vitro angiogenic response in all three cells lines. Unexpectedly, VEGF and VEGF-C also synergized in the in vitro angiogenic response when assessed on BAE cells. Characterization of VEGF receptor (VEGFR) expression revealed that BME, BAE, and BLE cell lines express VEGFR-1 and -2, whereas of the three cell lines assessed, only BAE cells express VEGFR-3. We also demonstrate that VEGF-C increases plasminogen activator (PA) activity in the three bovine endothelial cell lines and that this is accompanied by a concomitant increase in PA inhibitor-1. Addition of a2-antiplasmin to BME cells co-treated with bFGF and VEGF-C partially inhibited collagen gel invasion. These results demonstrate, first, that by acting in concert with bFGF or VEGF, VEGF-C has a potent synergistic effect on the induction of angiogenesis in vitro and, second, that like VEGF and bFGF, VEGF-C is capable of altering endothelial cell extracellular proteolytic activity. These observations also highlight the notion of context, i.e., that the activity of an angiogenesis-regulating cytokine depends on the presence and concentration of other cytokines in the pericellular environment of the responding endothelial cell. J. Cell. Physiol. 177:439‐452, 1998. q 1998 Wiley-Liss, Inc.

Overexpression of VEGF in Testis and Epididymis Causes Infertility in Transgenic Mice: Evidence for Nonendothelial Targets for VEGF

Abstract: Vascular endothelial growth factor (VEGF) is a key regulator of endothelial growth and permeability. However, VEGF may also target nonendothelial cells, as VEGF receptors and responsiveness have been detected for example in monocytes, and high concentrations of VEGF have been reported in human semen. In this work we present evidence that overexpression of VEGF in the testis and epididymis of transgenic mice under the mouse mammary tumor virus (MMTV) LTR promoter causes infertility. The testes of the transgenic mice exhibited spermatogenic arrest and increased capillary density. The ductus epididymidis was dilated, containing areas of epithelial hyperplasia. The number of subepithelial capillaries in the epididymis was also increased and these vessels were highly permeable as judged by the detection of extravasated fibrinogen products. Intriguingly, the expression of VEGF receptor-1 (VEGFR-1) was detected in certain spermatogenic cells in addition to vascular endothelium, and both VEGFR-1 and VEGFR-2 were also found in the Leydig cells of the testis. The infertility of the MMTV-VEGF male mice could thus result from VEGF acting on both endothelial and nonendothelial cells of the male genital tract. Taken together, these findings suggest that the VEGF transgene has nonendothelial target cells in the testis and that VEGF may regulate male fertility.

Is Angiopoietin-2 Necessary for the Initiation of Tumor Angiogenesis?

Abstract: Almost all functional cells are located within 30 μm of a blood capillary. Acute changes in blood flow are regulated in response to tissue needs by changes in the constriction level of blood vessels, 1 whereas long-term regulation of tissue perfusion is achieved by growth of new blood vessels or by vascular regression. 2 Physiological angiogenesis is limited to wound healing and changes in female reproductive organs during the menstrual cycle and pregnancy but blood vessels maintain their ability to grow and regress throughout life. Changes in the vasculature occur in association with many pathological processes, such as ocular neovascularization, inflammatory diseases, and cancer. 3 The concept that solid tumor growth depends on angiogenesis is well established. 4 Indeed, tumor size is restricted to a few cubic millimeters if it is not able to attract new blood vessels. The primitive embryonic vasculature is laid down by vasculogenesis, 5 which involves in situ differentiation of endothelial cells (ECs) from mesodermal precursors and their organization into a primary vascular plexus. In adults, all new blood vessels appear to be formed by angiogenesis, which is based on sprouting of blood vessels from existing ones or on intussusceptive growth involving in situ remodeling of the vessels by protruding interstitial tissue columns. In embryos, some developing organs including the brain and kidneys are vascularized by angiogenesis. The initiation of blood vessel growth involves focal reduction of intercellular interactions and interactions between the cells of the blood vessel and the surrounding extracellular matrix (ECM). This is associated with a loss of pericytes (PCs) and possibly of smooth muscle cells (SMCs) from the existing vessels. 2 Many angiogenic factors have been shown to be mitogenic and chemoattractive for ECs. The ECs have been shown to distort malleable substrata in a process called traction 6,7 and the reorganized ECM may facilitate the formation of complex weblike EC structures. Formation of functional blood vessels requires remodeling of this EC meshwork. Initiation of blood flow enables adaptation to changing blood and oxygen pressure conditions and further remodeling of the vascular network. 8 The maturation of newly formed vessels involves the accumulation of a basal lamina and tightly associated PCs or SMCs on the abluminal side. Although many phases of vessel growth overlap, this classification shows that complex orchestration is required in order for angiogenesis to proceed. Numerous substances can trigger the angiogenic process by causing a reprogramming of cells in the blood vessels 9 and these responses are beginning to be elucidated. In this issue of The American Journal of Pathology, Stratmann et al 10 report their novel finding that the angiopoietin-2 (Ang-2) signaling molecule is up-regulated in a spotlike fashion in the endothelium of growing blood vessels in glioblastoma. The authors also show that angiopoietin-1 (Ang-1), a related signaling molecule, is secreted from tumor cells and that Tie-2, a receptor for both Ang-1 and Ang-2, is up-regulated in the endothelium of vessels undergoing angiogenesis.

Avian vegf-c : cloning, embryonic expression pattern and stimulation of the differentiation of vegfr2-expressing endothelial cell precursors

Abstract: VEGF-C is a recently discovered secreted polypeptide related to the angiogenic mitogen VEGF. We have isolated the quail VEGF-C cDNA and shown that its protein product is secreted from transfected cells and interacts with the avian VEGFR3 and VEGFR2. In situ hybridization shows that quail VEGF-C mRNA is strongly expressed in regions destined to be rich in lymphatic vessels, particularly the mesenteries, mesocardium and myotome, in the region surrounding the jugular veins, and in the kidney. These expression sites are similar to those observed in the mouse embryo (E. Kukk, A. Lymboussaki, S. Taira, A. Kaipainen, M. Jeltsch, V. Joukov and K. Alitalo, 1996, Development 122, 3829-3837). We have observed VEGFR3-positive endothelial cells in proximity to most of the VEGF-C-expressing sites, suggesting functional relationships between this receptor-ligand couple. The comparison of the VEGF and VEGFR2 knockout phenotypes had suggested the existence of another ligand for VEGFR2. We therefore investigated the effect of VEGF-C on VEGFR2-positive cells isolated from the posterior mesoderm of gastrulating embryos. We have recently shown that VEGF binding triggers endothelial differentiation of these cells, whereas hemopoietic differentiation appears to be mediated by binding of a so far unidentified VEGFR2 ligand. We show here that VEGF-C also triggers endothelial differentiation of these cells, presumably via VEGFR2. These results indicate that VEGF and VEGF-C can act in a redundant manner via VEGFR2. In conclusion, VEGF-C appears to act during two different developmental phases, one early in posterior mesodermal VEGFR2-positive endothelial cell precursors which are negative for VEGFR3 and one later in regions rich in lymphatic vessels at a time when endothelial cells express both VEGFR2 and VEGFR3.

Vascular endothelial growth factor c (vegf-c) protein and gene, mutants thereof, and uses thereof

Abstract: Provided are purified and isolated VEGF-C polypeptides capable of binding to at least one of KDR receptor tyrosine kinase (VEGFR-2) and Flt4 receptor tyrosine kinase (VEGFR-3); analogs of such peptides that have VEGF-C-like or VEGF-like biological activities or that are VEGF or VEGF-C inhibitors; polynucleotides encoding the polypeptides; vectors and host cells that embody the polynucleotides; pharmaceutical compositions and diagnostic reagents comprising the polypeptides; and methods of making and using the polypeptides.

Expression vectors and cell lines expressing vascular endothelial growth factor d, and method of treating melanomas

Abstract: This invention relates to expression vectors comprising VEGF-D and its biologically active derivatives, cell lines stably expressing VEGF-D and its biologically active derivatives, and to a method of making a polypeptide using these expression vectors and host cells. The invention also relates to a method for treating and alleviating melanomas or tumors expressing VEGF-D and various diseases.

Co-amplification of a novel cyclophilin-like gene (PPIE) with L-myc in small cell lung cancer cell lines.

Abstract: Specific genetic alterations affecting proto-oncogenes of the myc gene family are frequently detected in human lung cancer. Among 11 SCLC cell lines with L-myc gene amplification, four were found to have alteration of the RLF gene by Southern blot and RT-PCR analyses. One cell line, NCI-H378, contained aberrantly-sized L-myc-hybridizing bands by Southern and Northern blot hybridization but had no alteration of RLF. Some L-myc-hybridizing cDNAs from NCI-H378 contained a novel sequence with close homology to the cyclophilins joined to antisense L-myc exon 2 sequence. Full length cDNAs isolated from human skeletal muscle containing only the novel sequence identify open reading frames of 301 and 296 amino acids and differ in the C-terminal region by 22 and 17 amino acids. This gene, tentatively named PPIE (peptidyl-prolyl cis-trans isomerase E), has 83% amino acid identity with the central conserved region of cyclophilin A, is evolutionarily conserved by Southern blot, and exhibits differential tissue expression with highest levels found in muscle and brain. Co-amplification of PPIE was observed in seven of eleven L-myc amplified cell lines. Analysis of radiation hybrids suggests that the gene order is RLF-PPIE-L-myc on chromosome 1p and pulse-field gel electrophoresis localizes all three genes to an 800 megabase Mlu I fragment. The prognostic and functional consequences of PPIE gene amplification in SCLC can now be determined.

Stimulation, modulation and/or inhibition of endothelial proteolytic activity and/or angiogenic activity

Abstract: Vascular endothelial growth factor-B (VEGF-B) and vascular endothelial growth factor-C (VEGF-C) are angiogenic polypeptides. It has been shown that VEGF-B and -C are angiogenic in vitro especially in combination with bFGF. VEGF-C also increases plasminogen activator (PA) activity in bovine endothelial cell lines and this is accompanied by a concomitant increase in PA inhibitor-1. Addition of alpha-2-antiplasmin to bovine endothelial cells co-treated with bFGF and VEGF-C partially inhibits collagen gel invasion.

Expression vectors and cell lines expressing vascular endothelial growth factor D

Abstract: This invention relates to expression vectors comprising VEGF-D and its biologically active derivatives, cell lines stably expressing VEGF-D and its biologically active derivatives, and to a method of making a polypeptide using these expression vectors and host cells. The invention also relates to a method for treating and alleviating melanomas or tumors expressing VEGF-D and various diseases.

Proteine et gene du facteur de croissance vasculaire endothelial c (vegf-c), mutants de ce dernier et utilisations

Abstract: Polypeptides VEGF-C purifies et isoles, capables de se lier a au moins une des tyrosine kinases suivantes: tyrosine kinase a recepteur KDR (VEGFR-2) et tyrosine kinase a recepteur Flt4 (VEGFR-3). L'invention concerne egalement des analogues de tels peptides, presentant des activites biologiques de type VEGF-C ou VEGF ou qui sont des inhibiteurs de VEGF ou de VEGF-C, ainsi que des polynucleotides codant ces polypeptides, des vecteurs et cellules hotes qui contiennent ces polynucleotides, des compositions pharmaceutiques et reactifs pour diagnostic contenant ces polypeptides et des procedes pour produire et utiliser ces polypeptides.

Mutants of vascular endothelial growth factor c (vegf-c) and uses thereof

Abstract: Provided are purified and isolated VEGF-C polypeptides capable of binding to at least one of KDR receptor tyrosine kinase (VEGFR-2) and Flt4 receptor tyrosine kinase (VEGFR-3); analogs of such peptides that have VEGF-C-like or VEGF-like biological activities or that are VEGF or VEGF-C inhibitors; polynucleotides encoding the polypeptides; vectors and host cells that embody the polynucleotides; pharmaceutical compositions and diagnostic reagents comprising the polypeptides; and methods of making and using the polypeptides.