Showing papers on "Angiogenesis published in 1991"
TL;DR: The number of microvessels per 200x field in the areas of most intensive neovascularization in an invasive breast carcinoma may be an independent predictor of metastatic disease either in axillary lymph nodes or at distant sites (or both).
Abstract: Background. Experimental evidence suggests that the growth of a tumor beyond a certain size requires angiogenesis, which may also permit metastasis. To investigate how tumor angiogenesis correlates with metastases in breast carcinoma, we counted microvessels (capillaries and venules) and graded the density of microvessels within the initial invasive carcinomas of 49 patients (30 with metastases and 19 without). Methods. Using light microscopy, we highlighted the vessels by staining their endothelial cells immunocyto-chemically for factor VIII. The microvessels were carefully counted (per 200×field), and their density was graded (1 to 4+), in the most active areas of neovascularization, without knowledge of the outcome in the patient, the presence or absence of metastases, or any other pertinent variable. Results. Both microvessel counts and density grades correlated with metastatic disease. The mean (±SD) count and grade in the patients with metastases were 101±49.3 and 2.95±1.00 vessels, respect...
5,699 citations
TL;DR: General themes are emerging that yield new strategies for prognosis and therapy of hu- man metastatic cancer, and an imbalanced regulation of motility and proteoly- sis appears to be required for invasion and metastasis.
2,776 citations
TL;DR: The goal of this review is to describe those stimulators and inhibitors of angiogenesis that have been best-characterized.
Abstract: Proliferation of blood vessels is a process necessary for the nonnal growth and development of tissue (36). In the adult, angiogenesis occurs infrequently. Exceptions are found in the female reproductive system, where angiogenesis occurs in the follicle during its development, in the corpus luteum during ovulation, and in the placenta after pregnancy. These periods of angiogenesis are relatively brief and tightly regulated. Nonnal angiogenesis also occurs as part of the body's repair processes, e.g. in the healing of wounds and fractures. By contrast, uncontrolled angiogenesis can often be pathological. For example, the growth of solid tumors depends on vascularization (37), and in diabetic retinopathy vascularization of the retina often leads to blindness. Given the physiologic and pathological importance of angiogenesis, much effort in the last twenty years has been devoted to the isolation, characteriza tion, and purification of factors that can either stimulate or inhibit an giogenesis. Several bioassays have been developed to measure angiogenesis. The most common ones are endothelial cell migration (47) and proliferation (38) in vitro, and capillary growth in vivo in the developing chick chorioallantoic membrane (CAM) (4) and the cornea (45). The goal of this review is to describe those stimulators and inhibitors of angiogenesis that have been best-characterized.
990 citations
TL;DR: Ligand autoradiography on rat tissue sections demonstrates that VEGF binding sites are associated with vascular endothelial cells of both fenestrated and non‐fenestrated capillaries and with the endothelium of large vessels, while no displaceable binding is evident on non‐endothelial cells.
Abstract: Vascular endothelial growth factor (VEGF) was identified as a heparin-binding polypeptide mitogen with a target cell specificity restricted to vascular endothelial cells. Molecular cloning reveals the existence of four species of VEGF having 121, 165, 189, and 206 amino acids. These have strikingly different secretion patterns, which suggests multiple physiological roles for this family of polypeptides. The two shorter forms are efficiently secreted, while the longer ones are mostly cell-associated. Alternative splicing of mRNA, rather that transcription from different genes, is the mechanism for their generation. In situ hybridization reveals that the VEGF mRNA is widely distributed in most tissues and organs and expressed at particularly high levels in areas of active vascular proliferation, like the ovarian corpus luteum. Ligand autoradiography on rat tissue sections demonstrates that VEGF binding sites are associated with vascular endothelial cells of both fenestrated and non-fenestrated capillaries and with the endothelium of large vessels, while no displaceable binding is evident on non-endothelial cell types. These findings support the hypothesis that VEGF plays a highly specific role in the maintenance and in the induction of growth of vascular endothelial cells.
721 citations
TL;DR: It is demonstrated that PECAM-1 mediates cell-cell adhesion and support the idea that it may be involved in some of the interactive events taking place during thrombosis, wound healing, and angiogenesis.
Abstract: PECAM-1 is a 130-120-kD integral membrane glycoprotein found on the surface of platelets, at endothelial intercellular junctions in culture, and on cells of myeloid lineage. Previous studies have shown that it is a member of the immunoglobulin gene superfamily and that antibodies against the bovine form of this protein (endoCAM) can inhibit endothelial cell-cell interactions. These data suggest that PECAM-1 may function as a vascular cell adhesion molecule. The function of this molecule has been further evaluated by transfecting cells with a full-length PECAM-1 cDNA. Transfected COS-7, mouse 3T3 and L cells expressed a 130-120-kD glycoprotein on their cell surface that reacted with anti-PECAM-1 polyclonal and monoclonal antibodies. COS-7 and 3T3 cell transfectants formed cell-cell junctions that were highly enriched in PECAM-1, reminiscent of its distribution at endothelial cell-cell borders. In contrast, this protein remained diffusely distributed within the plasma membrane of PECAM-1 transfected cells that were in contact with mock transfectants. Mouse L cells stably transfected with PECAM-1 demonstrated calcium-dependent aggregation that was inhibited by anti-PECAM antibodies. These results demonstrate that PECAM-1 mediates cell-cell adhesion and support the idea that it may be involved in some of the interactive events taking place during thrombosis, wound healing, and angiogenesis.
709 citations
TL;DR: Results demonstrate the regulation of PA and PAI-1 production by VEGF in microvascular endothelial cells and are in accord with the hypothesis that extracellular proteolysis, appropriately balanced by protease inhibitors, is required for normal capillary morphogenesis.
625 citations
TL;DR: The clinical potential and specific application of 'angiomodulatory' strategies are discussed and their roles in wound healing are discussed.
620 citations
TL;DR: In this multistep tumorigenesis pathway of dermal fibrosarcomas, there appears to be a discrete switch to the angiogenic phenotype that correlates with the export of bFGF, a knownAngiogenic factor.
533 citations
TL;DR: These studies indicate that VPF is synthesized by tumor cells in vivo and accumulates in nearby blood vessels, its target of action.
Abstract: Vascular permeability factor (VPF) is a highly conserved 34-42-kD protein secreted by many tumor cells. Among the most potent vascular permeability-enhancing factors known, VPF is also a selective vascular endothelial cell mitogen, and therefore has been called vascular endothelial cell growth factor (VEGF). Our goal was to define the cellular sites of VPF (VEGF) synthesis and accumulation in tumors in vivo. Immunohistochemical studies were performed on solid and ascites guinea pig line 1 and line 10 bile duct carcinomas using antibodies directed against peptides synthesized to represent the NH2-terminal and internal sequences of VPF. These antibodies stained tumor cells and, uniformly and most intensely, the endothelium of immediately adjacent blood vessels, both preexisting and those newly induced by tumor angiogenesis. A similar pattern of VPF staining was observed in autochthonous human lymphoma. In situ hybridization demonstrated VPF mRNA in nearly all line 10 tumor cells but not in tumor blood vessels, indicating that immunohistochemical labeling of tumor vessels with antibodies to VPF peptides reflects uptake of VPF, not endogenous synthesis. VPF protein staining was evident in adjacent preexisting venules and small veins as early as 5 h after tumor transplant and plateaued at maximally intense levels in newly induced tumor vessels by approximately 5 d. VPF-stained vessels were also hyperpermeable to macromolecules as judged by their capacity to accumulate circulating colloidal carbon. In contrast, vessels more than approximately 0.5 mm distant from tumors were not hyperpermeable and did not exhibit immunohistochemical staining for VPF. Vessel staining disappeared within 24-48 h of tumor rejection. These studies indicate that VPF is synthesized by tumor cells in vivo and accumulates in nearby blood vessels, its target of action. Because leaky tumor vessels initiate a cascade of events, which include plasma extravasation and which lead ultimately to angiogenesis and tumor stroma formation, VPF may have a pivotal role in promoting tumor growth. Also, VPF immunostaining provides a new marker for tumor blood vessels that may be exploitable for tumor imaging or therapy.
525 citations
TL;DR: Vascular permeability factor, also known as vascular endothelial growth factor (VEGF), is a potent polypeptide regulator of blood vessel function and regulates the expression of tissue factor and the glucose transporter.
Abstract: Vascular permeability factor (VPF), also known as vascular endothelial growth factor (VEGF), is a potent polypeptide regulator of blood vessel function. VPF promotes an array of responses in endothelium, including hyperpermeability, endothelial cell growth, angiogenesis, and enhanced glucose transport. VPF regulates the expression of tissue factor and the glucose transporter. All of the endothelial cell responses to VPF are evidently mediated by high affinity cell surface receptors. Thus, endothelial cells have a unique and specific spectrum of responses to VPF. Since each of the responses of endothelial cells to VPF are also elicited by agonists, such as bFGF, TNF, histamine and others, it remains a major challenge to determine how post-receptor signalling pathways maintain both specificity and redundancy in cellular responses to various agonists.
331 citations
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TL;DR: Histological observation showed that the antitumor effect of 3H3 was due to the inhibition of bFGF-induced angiogenesis, providing direct causal evidence for the hypothesis that tumor growth isAngiogenesis dependent.
Abstract: Basic fibroblast growth factor (bFGF) is a potent angiogenic mitogen. To elucidate the effect of bFGF inhibitors in vivo, anti-bFGF immunoneutralizing monoclonal antibody was prepared. One monoclonal antibody against human bFGF, obtained by cell fusion and designated 3H3, completely inhibited bFGF-induced proliferation of human umbilical vein endothelial cells at a concentration of 100 ng/ml. 3H3 did not bind to acidic fibroblast growth factor or HST1 protein, indicating high specificity for bFGF. Furthermore, the immunoneutralizing activity of 3H3 was examined in vivo. K1000 cells (a BALB/c 3T3 transformant in which the leader sequence-fused bFGF gene was transfected) were transplanted s.c. into BALB/c nude mice. Growth of the tumor cells was inhibited by i.v. treatment with 3H3 at a concentration of 200 micrograms/mouse. Histological observation showed that the antitumor effect of 3H3 was due to the inhibition of bFGF-induced angiogenesis. This experiment provides direct causal evidence for the hypothesis that tumor growth is angiogenesis dependent. This finding could also have implications for the development of novel therapeutic approaches to angiogenic solid tumors.
TL;DR: Macrophage-derived factors that can alter this structure via degradation or via the clotting system will also be discussed, as the extracellular matrix appears to be involved in the control of angiogenesis.
TL;DR: A probabilistic mathematical model of angiogenesis is developed based upon specific microvessel endothelial cell (MEC) functions involved in vessel growth, predicting that both random motility and chemotaxis are MEC functions critically involved in determining the rate and morphology of new microvessels network growth.
TL;DR: The anti-angiogenic activity of AGM-1470, a new synthetic analog of fumagillin isolated from Aspergillus fumigatus, was extensively examined both in vitro and in vivo using four different types of assay and compared to that of the fumgillin parent.
TL;DR: G- CSF and GM-CSF induce endothelial cells to express an activation/differentiation program (including proliferation and migration) related to angiogenesis, and the combination of a nonangiogenic dose of bFGF with G-CSf resulted in an angiogenic response higher than that elicited by either individual cytokines.
Abstract: This study was designed to identify the set of functions activated in cultured endothelial cells by the hematopoietic growth factors, granulocyte colony-stimulating factor (G-CSF) and granulocyte macrophage-colony-stimulating factor (GM-CSF), and to compare them with those elicited by prototypic cytokines active on these cells. Moreover, indications as to the in vivo relevance of in vitro effects were obtained. G-CSF and GM-CSF induced endothelial cells to proliferate and migrate. In contrast, unlike appropriate reference cytokines (IL-1 and tumor necrosis factor, IFN-gamma), G-CSF and GM-CSF did not modulate endothelial cell functions related to hemostasis-thrombosis (production of procoagulant activity and of platelet activating factor), inflammation (expression of leukocyte adhesion molecule-1 and production of platelet activating factor), and accessory function (expression of class II antigens of MHC). Other colony-stimulating factors (IL-3 and macrophage-colony-stimulating factor) were inactive on all functions tested. In comparison to basic fibroblast growth factor (bFGF), G-CSF and GM-CSF induced lower maximal proliferation of endothelial cells, whereas migration was of the same order of magnitude. G-CSF and GM-CSF stimulated repair of mechanically wounded endothelial monolayers. Exposure to both cytokines induced shape changes and cytoskeletal reorganization consistent with a migratory phenotype. To explore the in vivo relevance of the in vitro effects of these cytokines on endothelium, we studied the angiogenic activity of human G-CSF in the rabbit cornea. G-CSF, but not the heat-inactivated molecule, had definite angiogenic activity, without any sign of inflammatory reactions. G-CSF was less active than bFGF. However, the combination of a nonangiogenic dose of bFGF with G-CSF resulted in an angiogenic response higher than that elicited by either individual cytokines. Thus, G-CSF and GM-CSF induce endothelial cells to express an activation/differentiation program (including proliferation and migration) related to angiogenesis.
TL;DR: Results and studies on the properties of other ECM‐immobilized enzymes and growth factors suggest that the ECM provides a storage depot for biologically active molecules which are thereby stabilized and protected and may allow a more localized and presistent mode of action, as compared to the same molecules in a fluid phase.
Abstract: Despite the ubiquitous presence of basic fibroblast growth factor (bFGF) in normal tissues, endothelial cell proliferation in these tissues is usually very low, suggesting that bFGF is somehow sequestered from its site of action. Immunohistochemical staining revealed the localization of bFGF in basement membranes of diverse tissues, suggesting that the extracellular matrix (ECM) may serve as a reservoir for bFGF. Moreover, functional studies indicated that bFGF is an ECM component required for supporting endothelial cell proliferation and neuronal differentiation. We have found that bFGF is bound to heparan sulfate (HS) in the ECM and is released in an active form when the ECM-HS is degraded by heparanase expressed by normal and malignant cells (i.e. platelets, neutrophils, lymphoma cells). It is proposed that restriction of bFGF bioavailability by binding to ECM and local regulation of its release provide a novel mechanism for neovascularization in normal and pathological situations. The subendothelial ECM contains also tissue type-and urokinase type-plasminogen activators which participate in cell invasion and tissue remodeling. These results and studies on the properties of other ECM-immobilized enzymes (i.e. thrombin, plasmin, lipoprotein lipase) and growth factors (GM-CSF, IL-3, osteogenin), suggest that the ECM provides a storage depot for biologically active molecules which are thereby stabilized and protected. This may allow a more localized and presistent mode of action, as compared to the same molecules in a fluid phase.
TL;DR: The authors showed that an acid-stable form of bFGF could be administered orally to rats with duodenal ulcers and promoted a ninefold increase of angiogenesis in the ulcer bed and accelerated ulcer healing more potently than cimetidine.
Abstract: The complete purification of the first angiogenic molecule, basic fibroblast growth factor (bFGF), was carried out in the authors' laboratory in 1983. Application of this peptide to chronic wounds enhances angiogenesis and accelerates wound healing. The authors showed that an acid-stable form of bFGF (i.e., bFGF-CS23) could be administered orally to rats with duodenal ulcers. The peptide promoted a ninefold increase of angiogenesis in the ulcer bed and accelerated ulcer healing more potently than cimetidine. Basic fibroblast growth factor did not reduce gastric acid. The authors now show that bFGF exists as a naturally occurring peptide in rat and human gastric and duodenal mucosa. This endogenous bFGF is present also in the bed of chronic ulcers in rats. Sucralfate binds bFGF and protects it from acid degradation. The sucralfate is angiogenic, based on its affinity for bFGF. When sucralfate is administered orally to rats, it significantly elevates the level of bFGF in the ulcer bed. Cimetidine, by its capacity to reduce gastric acid, also elevates bFGF in the ulcer bed. A hypothetical model is proposed in which prevention of ulcer formation or accelerated healing of ulcers by conventional therapies may be FGF dependent. Acid-stable bFGF-CS23 may be considered as a form of replacement therapy in the treatment of duodenal ulcers.
TL;DR: Results suggest that thrombospondin is an inhibitor of angiogenesis in vitro and are consistent with its proposed roles as a destabilizer of endothelial cell focal contacts and as an inhibitors of endothelium cell proliferation.
Abstract: The response of endothelial cells to angiogenic stimuli has been shown to be influenced by the extracellular microenvironment. We tested whether thrombospondin, an extracellular matrix protein, modulated the spontaneous formation of cords by endothelial cells in vitro. Despite continued proliferation, a decrease in secreted thrombospondin was detected in cord-containing, as compared with subconfluent, cultures of both aortic and microvascular endothelial cells. Consistent with this trend, mRNA levels of thrombospondin decreased by factors of 16 in aortic and 60 in microvascular cultures that contained endothelial cords. Since thrombospondin was immunolocalized to fibrillar arrays that appeared to be associated with endothelial cords, we added anti-thrombospondin IgG to cord-forming cultures to limit the availability of the protein during this process. In the presence of anti-thrombospondin antibodies, there was a 33-50% increase in cord formation. These results suggest that thrombospondin is an inhibitor of angiogenesis in vitro and are consistent with its proposed roles as a destabilizer of endothelial cell focal contacts and as an inhibitor of endothelial cell proliferation.
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TL;DR: It is suggested that investigation of agents that disrupt collagenolysis may similarly identify otherAngiogenesis inhibitors and further clarify the mechanisms of angiogenesis.
Abstract: We describe a new inhibitor of angiogenesis, minocycline, a semisynthetic tetracycline antimicrobial with anticollagenase properties. Minocycline was incorporated into controlled release polymers and tested in the rabbit cornea against neovascularization in the presence of the VX2 carcinoma. Inhibition by minocycline was shown to be comparable to that of the combination of heparin and cortisone, a potent inhibitor of angiogenesis. Minocycline decreased tumor-induced angiogenesis by a factor of 4.5, 4.4, and 2.9 at 7, 14, and 21 days, respectively. At the end of the experiment, whereas the corneas with empty polymers had large, invasive, exophytic tumors, none of the corneas with minocycline had such vascular masses. Recently, studies of agents that disrupt collagen synthesis and deposition have yielded several new angiogenesis inhibitors. We suggest that investigation of agents that disrupt collagenolysis may similarly identify other angiogenesis inhibitors and further clarify the mechanisms of angiogenesis.
TL;DR: Recognition of the importance of ECM and cell shape during capillary morphogenesis has led to the identification of a series of new angiogenesis inhibitors and elucidation of the molecular mechanism of capillary regulation may result in development of even more potent angiogenic modulators in the future.
Abstract: Capillary endothelial (CE) cells require two extracellular signals in order to switch from quiescence to growth and back to differentiation during angiogenesis: soluble angiogenic factors and insoluble extracellular matrix (ECM) molecules. Soluble endothelial mitogens, such as basic fibroblast growth factor (FGF), act over large distances to trigger capillary growth, whereas ECM molecules act locally to modulate cell responsiveness to these soluble cues. Recent studies reveal that ECM molecules regulate CE cell growth and differentiation by modulating cell shape and by activating intracellular chemical signaling pathways inside the cell. Recognition of the importance of ECM and cell shape during capillary morphogenesis has led to the identification of a series of new angiogenesis inhibitors. Elucidation of the molecular mechanism of capillary regulation may result in development of even more potent angiogenesis modulators in the future.
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TL;DR: For the visualization of the tumor vasculature, antibodies recognizing endothelial markers, especially monoclonal antibodies PAL-E and BMA 120, are preferable to those recognizing pericytes or basal lamina; within the microvasculature of tumors and granulation tissue, a heterogeneity of expression of endothelial and pericyte markers is observed.
Abstract: The structure and function of the tumor microvasculature is of great interest for cancer biology, diagnosis, and therapy The distribution of endothelial cells, pericytes, and basal lamina in tumors is not well documented In this study, the authors investigated the distribution of markers for these different components in a series of malignant human tumors and in human granulation tissue, both situations with extensive angiogenesis Their results show a striking heterogeneity in the expression of markers for pericytes and endothelial cells between different tumors, but also within a single tumor lesion To be able to distinguish between these two adjacent cell types decisively, all marker studies were carried out both on the light and the electron microscopical level and compared with staining results in granulation tissue of cutaneous wounds in healthy volunteers and of decubitus lesions In granulation tissue of decubitus lesions, well-defined zones with increasing levels of maturation can be delineated It was found that antibodies recognizing von Willebrand factor often failed to stain the tumor capillaries Of the pericyte markers, alpha-smooth muscle actin was only locally expressed by pericytes in the tumor vasculature, whereas the high-molecular-weight melanoma-associated antigen, a chondroitin sulfate proteoglycan, stained the microvasculature broadly Staining of the basal lamina components collagen type IV and laminin was, within the tumor, not restricted to the microvasculature From their findings the authors conclude that 1) for the visualization of the tumor vasculature, antibodies recognizing endothelial markers, especially monoclonal antibodies PAL-E and BMA 120, are preferable to those recognizing pericytes or basal lamina; 2) within the microvasculature of tumors and granulation tissue, a heterogeneity of expression of endothelial and pericyte markers is observed; 3) during the formation of granulation tissue, all three microvascular components can be demonstrated already in the histologically earliest stage, suggesting not only an involvement of endothelial cells but also of pericytes and basal lamina in the initial steps of angiogenesis in wound healing
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TL;DR: The problem of how tumors switch to the angiogenic phenotype during tumorigenesis is studied by using transgenic mice in which tumors develop at a predictable time and in discrete prevascular and vascular stages to discover antiangiogenic therapies directed at the source ofAngiogenic activity.
Abstract: Tumor growth and metastasis are angiogenesis-dependent. Virtually all solid tumors are neovascularized by the time they are detected. However, there is a prevascular phase during early tumor development where few or no tumor cells are angiogenic and expansion of the tumor is restricted to a few mm3. When enough tumor cells become angiogenic, the tumor can expand progressively and shed metastatic cells. This angiogenic switch has recently been quantitated for human breast cancer, as well as for prostate cancer. We have studied the problem of how tumors switch to the angiogenic phenotype by using transgenic mice in which tumors develop at a predictable time and in discrete prevascular and vascular stages. When the transgene is the bovine papilloma virus (BPV) genome, angiogenic fibrosarcomas develop from non-angiogenic precursors called fibromatoses. The fibrosarcomas secrete growth factors for capillary endothelial cells. In contrast, the fibromatoses do not secrete endothelial cell growth factors. When the transgene consists of the large "T" antigen of SV40 under the control of the rat insulin promoter, 70% of pancreatic islets become hyperplastic and 4-10% of these become angiogenic at 6-7 weeks. Tumors arise from these neovascularized hyperplastic islets and reach > 1000 x the volume of the preangiogenic islets. The onset of angiogenic activity coincides with the secretion of acidic fibroblast growth factor (aFGF) and other growth factors not fully identified at this writing. These studies help to explain the switch to the angiogenic phenotype during tumorigenesis and provide models to discover antiangiogenic therapies directed at the source of angiogenic activity. Such therapy, when developed, may be co-administered with currently available angiogenesis inhibitors which are directed at the target of angiogenic activity, vascular endothelial cells.
TL;DR: In vitro 16K PRL is a potent and specific angiolytic factor, i.e. it inhibits angiogenesis and has potential as a therapeutic agent for the treatment of cancer.
Abstract: Intact 23 kilodalton (kDa), rat PRL is enzymatically cleaved in many target tissues to a 16 kDa (16K PRL) and an 8 kDa fragment. After reduction of an internal disulfide bond the fragments are released. 16K PRL was shown to be a potent mitogen on mammary epithelial cells via PRL receptors. Since estradiol-induced prolactinomas develop a new blood supply we tested the action of intact PRL and 16K PRL on growth of new vessels (angiogenesis). The angiogenic action of intact PRL and 16K PRL was tested in cultured bovine brain and adrenal cortex endothelial cells. Basal (b) or b-fibroblast growth factor (FGF) stimulated growth was estimated by counting cells or measuring the level of incorporation of 3H-thymidine into DNA. Paradoxically, 16K PRL inhibited the basal and FGF-stimulated growth of cultured endothelial cells in a dose-dependent fashion. Intact PRL or the cleaved but not reduced PRL were inactive even at a 100-fold higher concentration. When reformation of disulfide bonds was inhibited by carbamidom...
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TL;DR: Type I collagen might facilitate the active migration of endothelial cells, or the stabilization of the resulting tubes, with SPARC directing the re-organization and dynamic assembly of the tubular network.
TL;DR: This review describes and evaluates the methodology and specific features of some of the most frequently used of the neovascular (angiogenic) response assays, both in vitro and in vivo, for the study of new blood vessel growth.
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TL;DR: The present findings support the conclusion that both r PF4 and rPF4-241 inhibit tumor growth by suppression of tumor-induced neovascularization and suggest that PF4 may play a more specific role in modulation of blood vessel development than previously recognized.
Abstract: An analogue of human platelet factor 4 (PF4) lacking affinity for heparin was specifically designed to evaluate the importance of this property in the antitumor effects of recombinant PF4. The purified protein, recombinant PF4-241 (rPF4-241), failed to bind heparin but retained the ability to suppress the growth of tumors in mice. Daily intralesional injections of rPF4-241 significantly inhibited the growth of the B-16 melanoma in syngeneic mice without direct inhibitory effects on B-16 cell growth in vitro. Similar antitumor effects were observed with the human colon carcinoma, HCT-116, grown in nude mice, indicating that the inhibitory activity was neither tumor-type specific nor T-cell dependent. rPF4-241 inhibited endothelial cell proliferation in vitro with dose dependence similar to the native sequence rPF4. Both rPF4 and rPF4-241 inhibited angiogenesis in the chicken chorioallantoic membrane. The analogue, however, was inhibitory at lower concentrations than rPF4 in the chorioallantoic membrane system and its inhibitory effects were not abrogated by the presence of heparin. The present findings support the conclusion that both rPF4 and rPF4-241 inhibit tumor growth by suppression of tumor-induced neovascularization. The finding that this activity is independent of heparin binding may allow the development of PF4-based angiostatic agents with reduced toxicity and improved bioavailability. These results also suggest that PF4 may play a more specific role in modulation of blood vessel development than previously recognized.
Journal Article•
TL;DR: It was concluded that solid tumor growth inhibition by CDPGYIGSR-NH2 was due not a direct effect on cell growth but to antiangiogenic effect mediated by the inhibition of endothelial cell migration.
Abstract: A laminin-derived synthetic peptide, Cys-Asp-Pro-Gly-Tyr-Ile-Gly-Ser-Arg-NH 2 (CDPGYIGSR-NH 2 ), containing an active site for cell binding inhibited both angiogenesis and solid tumor growth. It potently suppressed both embryonic angiogenesis of the chick chorioallantoic membrane and migration of vascular endothelial cells induced by a tumor-conditioned medium but neither the in vitro proliferation of endothelial cells nor that of tumor cells. Additionally, in in vivo tests, CDPGYIGSR-NH 2 markedly inhibited both the growth of s.c. solid tumor of Sarcoma 180 and that of Lewis lung carcinoma (3LL) in the lungs. On the contrary, ascitic tumor growth of Sarcoma 180 was not affected by this peptide, even though the same cell source was used. It was concluded that solid tumor growth inhibition by CDPGYIGSR-NH 2 was due not to a direct effect on cell growth but to an antiangiogenic effect mediated by the inhibition of endothelial cell migration.
TL;DR: The histochemical data reported here support the conclusions of earlier avian studies by showing distinct vascular patterns in the initial formation of vessels from isolated angioblasts followed by the extension and organization of the initial vascular structures (angiogenesis).
TL;DR: Results show that basic fibroblast growth factor, besides stimulating uPA production by vascular endothelial cells, also increases the production of receptors, which modulates their capacity to focalize this enzyme on the cell surface, which may be important in the degradative processes that occur during angiogenesis.
Abstract: Basic fibroblast growth factor, a potent angiogenesis inducer, stimulates urokinase (uPA) production by vascular endothelial cells. In both basic fibroblast growth factor-stimulated and -nonstimulated bovine capillary endothelial and human umbilical vein endothelial cells single-chain uPA binding is mediated by a membrane protein with a Mr of 42,000. Exposure of bovine capillary or endothelial human umbilical vein endothelial cells to pmolar concentrations of basic fibroblast growth factor results in a dose-dependent, protein synthesis-dependent increase in the number of membrane receptors for uPA (19,500-187,000) and in a parallel decrease in their affinity (KD = 0.144-0.790 nM). With both cells, single-chain uPA binding is competed by synthetic peptides whose sequence corresponds to the receptor-binding sequence in the NH2-terminal domain of uPA. Exposure of bovine capillary endothelial cells to transforming growth factor beta 1, which inhibits uPA production and upregulates type 1 plasminogen activator inhibitor, the major endothelial cell plasminogen activator inhibitor, has no effect on uPA receptor levels. These results show that basic fibroblast growth factor, besides stimulating uPA production by vascular endothelial cells, also increases the production of receptors, which modulates their capacity to focalize this enzyme on the cell surface. This effect may be important in the degradative processes that occur during angiogenesis.
TL;DR: Data suggest that the PDGF-B signalling pathway appears to switch from an autocrine to a paracrine mechanism to stimulate growth of surrounding PDGF beta-receptor-positive mesenchymal stromal cells.
Abstract: We have examined the role of platelet-derived growth factor (PDGF) ligand and receptor genes in the angiogenic process of the developing human placenta. In situ hybridization analysis of first trimester placentae showed that most microcapillary endothelial cells coexpress the PDGF-B and PDGF beta-receptor genes. This observation indicates that PDGF-B may participate in placental angiogenesis by forming autostimulatory loops in capillary endothelial cells to promote cell proliferation. Endothelial cells of macro blood vessels maintained high PDGF-B expression, whereas PDGF beta-receptor mRNA was not detectable. In contrast, PDGF beta-receptor mRNA was readily detectable in fibroblast-like cells and smooth muscle cells in the surrounding intima of intermediate and macro blood vessels. Taken together, these data suggest that the PDGF-B signalling pathway appears to switch from an autocrine to a paracrine mechanism to stimulate growth of surrounding PDGF beta-receptor-positive mesenchymal stromal cells. Smooth muscle cells of the blood vessel intima also expressed the PDGF-A gene, the protein product of which is presumably targeted to the fibroblast-like cells of the mesenchymal stroma as these cells were the only ones expressing the PDGF alpha-receptor. PDGF-A expression was also detected in columnar cytotrophoblasts where it may have a potential role in stimulating mesenchymal cell growth at the base of the growing placental villi. We discuss the possibility that the regulation of the PDGF-B and beta-receptor gene expression might represent the potential targets for primary angiogenic factors.