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At least 649 records · Page 36Linked to original sources
PubMed2006

Pro-angiogenesis action of thyroid hormone and analogs in a three-dimensional in vitro microvascular endothelial sprouting model.

AIM: Our laboratory has recently demonstrated the pro-angiogenesis effects of thyroid hormone in the chick chorioallantoic membrane model. METHODS: Generation of new blood vessels from existing vessels was promoted two- to three-fold by either L-thyroxine (T4) or 3,5,3'-triiodo-L-thyronine (T3) at total hormone concentrations of T7-T9 M. RESULTS: T4-agarose, a formulation of thyroid hormone that does not cross the cell membrane, produced a potent pro-angiogenesis effect comparable to that obtained with T3 or T4. In the present investigation, T3, T4, T4-agarose, and basic fibroblast growth factor, each added to vascular endothelial growth factor, produced comparable pro-angiogenesis effects in the in vitro three-dimensional human microvascular endothelial sprouting model. The pro-angiogenesis effect of the thyroid hormone analogs was blocked by PD 98059, an inhibitor of the mitogen-activated protein kinase (MAPK; ERK1/2) signal transduction cascade. A specific avb3 integrin antagonist (XT199) also inhibited the pro-angiogenesis effect of either thyroid hormone analogs or T4-agarose. Tetrac, a thyroid hormone analog that blocks cell surface-initiated actions of T4 and T3, inhibited the pro-angiogenesis response of thyroid hormone. CONCLUSIONS: T4, T3, and T4-agarose are pro-angiogenic in the three-dimensional human microvascular endothelial sprouting model, an action that is initiated at the plasma membrane, involves avb3 integrin receptors, and is MAPK-dependent.

Cells, Cultured↗
PubMed1987

Fibrin containing gels induce angiogenesis. Implications for tumor stroma generation and wound healing.

Fibrin deposition is a consistent early event in solid tumors and healing wounds and precedes new blood vessel ingrowth in both. We now demonstrate that fibrin gels of themselves induce an angiogenic response in the absence of tumor cells or platelets. Angiogenesis was enhanced when certain chemoattractants or mitogens were included in the fibrin gel. Newly devised, inert plastic chambers with one porous surface were filled with varying contents and were implanted in the subcutaneous space of guinea pigs. Chambers filled with cross-linked homologous fibrin or plasma induced an angiogenic response within 4 days. Vessels entered chambers through the surface pores and flared out radially; angiogenesis was quantitated by point counting. Vessels were functional and matured along a gradient that proceeded from distal (least mature) to proximal. The intensity of the angiogenic response was enhanced when zymosan activated serum, an N-formylmethionine tripeptide, or platelet-derived growth factor was included in the fibrin matrix. Prior aldehyde fixation or boiling of fibrin-filled chambers inhibited angiogenesis, as did high concentrations of hyaluronic acid. Chambers filled with type I collagen or agarose did not induce new blood vessel formation, but addition of collagen did not reduce fibrin's capacity to initiate angiogenesis. The novel assay introduced here offers several advantages that should facilitate the study of angiogenesis. These include reproducibility, low background, objective and quantitative scoring, and the capacity to evaluate native molecules in animals of several species. Taken together, our findings strongly implicate fibrin or related proteins in the pathogenesis of angiogenesis and offer a new approach for elucidating the underlying molecular mechanisms.

Animals↗
PubMed1994

Postreceptor signal transduction mechanisms involved in octreotide-induced inhibition of angiogenesis.

BACKGROUND: Somatostatin analogues inhibit peptide release and cell growth through multiple postreceptor signal transduction mechanisms (PRSTM), including G proteins (GP), cyclic adenosine monophosphate (cAMP), calcium, protein kinase C (PKC), and tyrosine phosphatase (TP). Octreotide acetate (OA), a somatostatin analogue, has been shown to inhibit angiogenesis; however, the PRSTM involved are unknown. METHODS: Fertilized chicken eggs were obtained and incubated. On day 3, embryos were removed and placed in plastic wrap hammocks. On day 7, disks containing OA, test substances that interfere with PRSTM, or combinations of OA plus a test substance were placed on the developing chorioallantoic membrane. Blood vessel growth under each disk was assessed at 24 hours. Data were evaluated by chi-squared analysis. RESULTS: OA's ability to inhibit angiogenesis is significantly diminished when combined with calcium, bradykinin (increases calcium), pertussis toxin (inhibits GP), or 3-isobutyl-1-methylxanthine (increases cAMP). In contrast, no significant decrease is noted in OA's ability to inhibit angiogenesis when combined with phorbol ester (activates PKC) or vanadate (inhibits TP). CONCLUSIONS: OA-induced inhibition of angiogenesis is GP, calcium, and cAMP dependent and is PKC and TP independent. Better understanding of the PRSTM involved with OA-induced inhibition of angiogenesis may lead to enhancement of OA's effect on angiogenesis.

Animals↗
PubMed1995

Vascular permeability factor/vascular endothelial growth factor, microvascular hyperpermeability, and angiogenesis.

VPF/VEGF is a multifunctional cytokine that contributes to angiogenesis by both direct and indirect mechanisms. On the one hand, VPF/VEGF stimulates the ECs lining nearby microvessels to proliferate, to migrate, and to alter their pattern of gene expression. On the other hand, VPF/VEGF renders these same microvascular ECs hyperpermeable so that they spill plasma proteins into the extravascular space, leading to the clotting of extravasated fibrinogen with deposition of a fibrin gel. Extravascular fibrin serves as a provisional matrix that favors and supports the ingrowth of new blood vessels and other mesenchymal cells that generate mature, vascularized stroma. These same principles apply in tumors, in several examples of non-neoplastic pathology, and in physiological processes that involve angiogenesis and new stroma generation. In all of these examples, microvascular hyperpermeability and the introduction of a provisional, plasma-derived matrix precede and accompany the onset of EC division and new blood vessel formation. It would seem, therefore, that tumors have "borrowed" fundamental mechanisms that developed in multicellular organisms for purposes of tissue defense, renewal, and repair. VPF/VEGF, therefore has taught us something new about angiogenesis; namely, that vascular hyperpermeability and consequent plasma protein extravasation are important, perhaps essential, elements in its generation. However, this finding raises a paradox. While VPF/VEGF induces vascular hyperpermeability, other potent angiogenic factors apparently do not, at least in subtoxic concentrations that are more than sufficient to induce angiogenesis. Nonetheless, wherever angiogenesis has been studied, the newly generated vessels have been found to be hyperpermeable. How, therefore, do angiogenic factors other than VPF/VEGF lead to the formation of new and leaky blood vessels? We do not as yet have a complete answer to this question. One possibility is that at least some angiogenic factors mediate their effect by inducing or stimulating the expression of VPF/VEGF. In fact, there is already one clear example of this. TGF-alpha is a potent angiogenic factor but does not itself increase microvascular permeability. However, TGF-alpha strikingly upregulates VPF/VEGF expression in cultured keratinocytes and is thought to be responsible, at least in part, for the overexpression of VPF/VEGF in psoriasis. Moreover, overexpression of TGF-alpha, along with that of the EGF receptor with which it interacts, is characteristic of many malignant tumors, raising the possibility that TGF-alpha acts to stimulate VPF/VEGF expression in other types of epithelial cells and in this manner induces angiogenesis.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Ovarian angiogenesis. Phenotypic characterization of endothelial cells in a physiological model of blood vessel growth and regression.

Angiogenesis occurs during embryogenesis and is a down-regulated process in the healthy adult that is almost exclusively linked to pathological conditions such as tumor growth, wound healing, and inflammation. Physiological angiogenic processes in the adult are restricted to the female reproductive system where they occur cyclically during the ovarian and uterine cycle as well as during pregnancy. By systematically analyzing the phenotypic changes of endothelial cells during bovine corpus luteum (CL) formation and regression, we have established a physiological model of blood vessel growth and regression. Quantitation of vessel density, percentage of vessels with lumen, and ratio of Bandeiraea simplicifolia-I to von Willebrand Factor-positive endothelial cells were established as parameters of angiogenesis. Sprouting endothelial cells invade the growing CL and continue to grow throughout the first third of the ovarian cycle. Thereafter the mature CL is characterized by a dense network of vessels with gradually decreasing vessel density. During luteolysis and for several weeks thereafter (regressing and residual CL) all newly formed vessels regress, which is accompanied by gradual foreshortening and rounding of endothelial cells and subsequent detachment. Based on histochemical detection of nucleosomal fragmentation products physiological blood vessel regression in the cyclic CL does not appear to involve endothelial cell apoptosis. Lectin histochemical analysis revealed a distinct alteration of endothelial cell glycoconjugate expression during ovarian angiogenesis comparable with the distinct pattern of hyperglycosylation of cultured migrating endothelial cells (up-regulation of binding sites for Lycopersicon esculentum lectin, wheat germ agglutinin, neuraminidase-treated peanut agglutinin, and Ricinus communis agglutinin-I on sprouting ECs). Northern blot analysis of glycosyltransferases during the different stages of angiogenesis revealed an up-regulation of beta-galactoside alpha 2,6-sialyltransferase and alpha 1,3-galactosyltransferase mRNA expression during the angiogenic stages of CL formation. These data establish the ovarian angiogenesis model as a suitable experimental system to study the functional and phenotypic properties of endothelial cells in sprouting and regressing blood vessels and provide additional evidence for the importance of endothelial cell surface glycoconjugates during angiogenesis.

Animals↗
PubMed1996

Transforming growth factor beta1 induces angiogenesis in vivo with a threshold pattern.

SUMMARY: The true role of transforming growth factor beta1 (TGFbeta) on angiogenesis is in question. Several in vitro studies have shown inhibition of proliferation and migration of endothelial cells (EC). However, some investigators have observed that TGFbeta stimulates the formation of EC tubes in vitro. Fewer in vivo studies have been performed, but these also show discrepancies: some report angiogenic induction and at least one reports inhibition. We used the disc angiogenesis system (DAS) to measure the in vivo effect of TGFbeta. Discs containing 1 ng to 2000 ng of TGFbeta were placed subcutaneously in mice, removed after a growth period of 14 days, measured by three different techniques, and compared with spontaneous growth controls and with positive controls containing prostaglandin El. Tritiated thymidine was used to determine proliferation of EC. The discs were also examined morphologically for patterns of vessel and stromal proliferation. The contribution of native TGFbeta to the spontaneous angiogenesis of wound healing was tested using a monoclonal anti-TGFbeta antibody. The combined effect of TGFbeta and fibroblast growth factor (bFGF) was studied by using suboptimal doses of both (500 ng and 10 microg, respectively). Although TGFbeta doses of 1 ng to 500 ng failed to induce angiogenesis, 1000 ng induced a significant level of angiogenesis which was maintained at 2000 ng. This effect was the same regardless of the method of quantification: centripetal growth of the vessels, size of fibrovascular growth area, or amount of incorporation of tritiated thymidine. The anti-TGFbeta antibody decreased the spontaneous vascular growth below the level of controls containing irrelevant IgG. The combination of TGFbeta and bFGF at suboptimal doses did not increase or decrease the angiogenic response. Discs containing TGFbeta showed more collagen and greater accumulation of neutrophils than control discs or discs containing other cytokines. In conclusion, TGFbeta1 is angiogenic in vivo, when it reaches a threshold of 1 microg, but is not angiogenic at doses of 1 to 500 ng. Endogenous TGFbeta contributes to spontaneous (wound healing) angiogenesis. At the suboptimal doses of TGFbeta and bFGF used, there is no evidence of a combined angiogenic effect. The angiogenic effect of TGFbeta is probably indirect, requiring recruitment of leukocytes that secondarily release angiogenic substances. This secondary effect may explain some of the discrepancies between the in vitro and in vivo effects of TGFbeta.

Alprostadil↗
PubMed1997

Paradoxical effects of intra-arterial administration of basic fibroblast growth factor on inflammatory angiogenesis in rats.

The authors studied the effects of basic fibroblast growth factor (b-FGF) on inflammatory angiogenesis in rats. In the corneal cauterization model b-FGF was given intra-arterially (i.a.) (carotid) and in the mesenteric window angiogenesis model, topically (i.e., intraperitoneally (i.p.)). The corneal cauterization was done under anaesthesia by topical application of silver nitrate. Mesenteric window angiogenesis was induced by injection of saline or b-FGF for four days. There were the same two groups of treatment in both models b-FGF 2.5 micrograms/kg/day or saline 1.2-5 ml/kg/day. The area of neovessels and the number of polymorphonuclear cells/field were considered for the corneal angiogenesis, the total length of neovessels was measured for the mesenteric window angiogenesis. The results were expressed as mean values (s.d.). When given i.a., b-FGF significantly reduced the number of polymorphonuclear cells three days after corneal cauterization (from 107 +/- 27 to 41.8 +/- 26, p < 0.01) and inhibited the area covered by neovessels (30 +/- 7.7% vs 51 +/- 20%, p < 0.01) after five days. In contrast, given through the extracellular space, it significantly stimulated the length of mesenteric window microvessels (169 +/- 60 mm vs 90 +/- 31 mm, p < 0.05). These results suggest that b-FGF stimulates inflammatory angiogenesis through interaction with extracellular matrix components, but inhibits it directly when given intra-arterially.

Administration, Topical↗
PubMed1996

Vitamin D3 is a potent inhibitor of tumor cell-induced angiogenesis.

Vitamin D3 derivative 1,25-dihydroxyvitamin D3 (1,25[OH]2D3) exerts various biological effects in cells that possess vitamin D3 receptor (VDR), including enhancement of cell differentiation and inhibition of cell proliferation. These activities of 1,25(OH)2D3 might be responsible for its anti-neoplastic effects, as shown in various experimental systems. The aim of this study was to compare the anti-angiogenic activity of 1,25(OH)2D3, retinoids, and interleukin-12 (IL-12) in an experimental tumor cell-induced angiogenesis assay in mice. Tumor cell-induced angiogenesis assay was performed in x-ray immunosuppressed BALB/c mice by intradermal injections of human tumor cell lines of different origin. The injections resulted within 3 d in a local formation of new blood vessels, and the intensity of angiogenesis correlated with the number of injected cells. Systemic treatment of the mouse recipients with 1,25(OH)2D3 significantly decreased angiogenesis, comparable to the effect of retinoids (all-trans retinoic acid [RA], 9-cis RA and 13-cis RA) and of IL-12. In vitro preincubation of the cells with all compounds (except IL-12) led to the inhibition of their angiogenic capability in vivo. Moreover, combination of 1,25(OH)2D3 and retinoids resulted in a synergistic inhibition of angiogenesis. The results strongly suggest that anti-angiogenic compounds with relatively low toxicity (e.g., 1,25(OH)2D3, retinoids, and IL-12) and their combinations could be beneficial in the treatment of some angiogenesis-associated malignancies.

Animals↗
PubMed1997

Relationship of tumor angiogenesis and nuclear p53 accumulation in invasive bladder cancer.

The purpose of this investigation was to evaluate the relationship between tumor angiogenesis and nuclear p53 accumulation in invasive bladder cancer. We studied 161 patients with invasive transitional cell carcinoma of the bladder who had previously undergone radical cystectomy. Analysis was performed to determine the presence of p53 nuclear accumulation and extent of tumor-associated angiogenesis. p53 status identified a group of patients at high risk for tumor progression (p53-altered tumors), and microvessel density determinations added additional prognostic information by identifying a subset of aggressive tumors within the wild-type p53 subgroup. At 5 years, patients with tumors exhibiting no evidence of p53 alterations and low microvessel counts demonstrated 3% recurrence and 88% survival, compared to 43% recurrence and 59% overall survival for patients with intermediate vessel counts and 61% recurrence and 43% overall survival for patients with the highest vessel counts (P < 0.001 and P = 0.003, respectively). Angiogenesis also provides additional prognostic information to patients with tumors that demonstrate p53 alterations. An association between angiogenesis and p53 status did exist (P = 0. 05); however, 27% of the tumors that showed no evidence of p53 alterations exhibited high microvessel counts, and 26% of tumors with evidence of p53 alterations had low microvessel counts. Tumor-associated angiogenesis adds additional useful prognostic information to that which is obtained from p53 status in patients with invasive transitional cell carcinoma of the bladder. Although an association between p53 status and the degree of angiogenesis was identified, other factors appear to play a role in the regulation of tumor-induced neovasularization.

Biomarkers, Tumor↗
PubMed1996

Determination of angiogenesis adds information to estrogen receptor status in predicting the efficacy of adjuvant tamoxifen in node-positive breast cancer patients.

There is experimental and clinical evidence that angiogenesis is involved in breast cancer progression and metastasis. To investigate whether the determination of angiogenesis adds prognostic information to the estrogen receptor (ER) status, we studied a series of 178 node-positive breast cancer patients, with a median follow-up time exceeding 5 years, treated with adjuvant tamoxifen (TAM). We assessed angiogenesis by the quantification of the intratumoral microvessel density and the determination of the Chalkley score using light microscopy. Microvessels were immunostained using the anti-CD31 antibody. The other features studied were ER status and the conventional clinicopathological prognostic indicators. Results were pooled from two collaborating Centers using Chalkley counts to convert intratumoral microvessel density to a common quantification system. We found that Chalkley score was not associated with any other feature studied. In univariate analysis, Chalkley score was significantly predictive of both relapse-free survival (RFS) and overall survival (OS; P < 0. 00001 and P = 0.00004, respectively). Likewise, ER status, the number of metastatic axillary nodes, histological grading, and tumor size were significantly predictive for RFS and OS. Cox multivariate analysis showed that Chalkley score was the strongest significant independent predictor of outcome. For RFS, ER status, the number of metastatic nodes, and histological grading also retained significance. For OS, the number of metastatic nodes, tumor size, and histological grading were independent prognostic factors. The joint assessment of the above variables had a satisfactory prognostic capability, as found using the Harrel statistics (c = 0. 77). These results suggest the validity of using Chalkley counts to assess and compare angiogenesis for prognostic purposes between different Centers. We found that angiogenesis adds significant prognostic information to ER status in predicting the outcome of breast cancer patients treated with adjuvant TAM. In fact, irrespective of the ER status, the patients with highly angiogenic tumors had a poor outcome, even if treated with TAM. For these patients, the inhibition of angiogenesis with specific angioinhibitory drugs may be a promising new therapeutic strategy.

Breast Neoplasms↗
PubMed2000

Angiogenesis: new insights and therapeutic potential.

Angiogenesis, the formation of vessels from pre-existing vessels, is of critical importance not only during normal growth, but also in pathological situations. In the latter, some diseases are enhanced by excessive vascular growth (e.g., tumors), whereas in others inadequate vascular growth contributes to morbidity and mortality (e. g., ischemic heart disease). Our current state of knowledge makes it clear that the cascade of angiogenic events depends on complex processes that include cell-cell interactions, various intracellular signaling pathways, and the appropriate extracellular microenvironment. The literature regarding angiogenesis has increased exponentially during the last decade. Progress in this area is largely a consequence of advances in our understanding of angiogenic growth factor and cytokine function, in part due to the determination of their complete amino acid sequences and cloning of their genes. Other factors also play key roles in angiogenesis, including the extracellular matrix, adhesion molecules and their inhibitors, and metabolic and mechanical factors. The potential for developing therapeutic protocols has been enhanced by data from both in vitro and in vivo studies and has provided the rationale for clinic trials. Angiogenic therapy strategies include inhibition of aberrant angiogenesis, as seen in tumors or diabetes, as well as stimulation of angiogenesis in conditions of ischemia, such as ischemic heart or peripheral vascular disease. Anat Rec (New Anat) 261:126-135, 2000.

Angiogenesis Inducing Agents↗
PubMed2007

Molecular imaging of angiogenesis.

Angiogenesis (the growth of new blood vessels) is a complex multistep process that involves multiple cell types, numerous growth factors, and complex regulatory checks and balances. Tight control of vascular remodeling evolved to ensure stability of the vasculature while maintaining the body's ability to rapidly mount an angiogenic response requiring a high degree of plasticity. Angiogenesis is critical not only for physiological development, but also for the progression of pathologies, and is thus a target for therapeutic intervention. The importance of the process coupled with the ease of access for delivery of contrast agents makes the vasculature at large, and angiogenesis in particular, a favorable target of functional and molecular imaging. Recent developments in molecular imaging tools have expanded our views to encompass many components of the process. Functional imaging of blood volume, vessel permeability, and vasoreactivity is complemented by novel contrast agents that reveal specific targets on endothelial cells. Methods have been developed to label vascular cells so as to track their recruitment to sites of angiogenesis, and new "smart" contrast agents have been designed to reveal the activity of enzymatic reactions in altering the extracellular matrix (ECM) during angiogenesis.

Angiogenesis Inducing Agents↗
PubMed2002

Effect of sulfated beta-cyclodextrin, a water soluble cycloamylose, on the promotion and/or inhibition of angiogenesis.

Previous studies have reported that sulfated b b-cyclodextrin, a naturally occurring cycloamylose built up from six to eight glucopyranose units, when administered alone promotes angiogenesis, but administered with an angiostatic steroid inhibits angiogenesis in the cick embryo bioassay. In our experiments sulfated b b-cyclodextrin has been shown to possess many properties unrelated to its classical functions in the promotion and inhibition of angiogenesis that were not previously described. We studied the angiogenic and angiostatic properties of b b-cyclodextrin in a subcutaneous plastic sponge model in mice. We realized two set of experiments. In each set mice were randomized into five groups (n= 5 mice). The first group was treated with sulfated b b-cyclodextrin (200 ng), the second group was treated with sulfated b b-cyclodextrin (2000 ng), the third group received unsubstituted b b-cyclodextrin (2000 ng), the fourth group was treated with sulfated b b-cyclodextrin (20000 ng) and the last group was used as a control group. In all groups compounds were administered intraperitoneally 4 days after subcutaneous implantation of a sterile polyvinyl sponge on day 0, controls were not treated. Cyclodextrin administered alone at low drug concentration (200 ng) promoted angiogenesis and increased the development of venules in the sponge matrix. However, cyclodextrin administered at high drug concentration (2000 and 20 000 ng) reduced the vessel index in the sponge and areas of microhemorrhages were observed. From our results we propose that b b-cyclodextrin contains both a promoter and an inhibitor of angiogenesis and that the activation of both is drug concentration dependent.

Analysis of Variance↗
PubMed2005

Sex steroid regulation of angiogenesis in breast tissue.

Angiogenesis is essential for normal function in the female reproductive tract and a prerequisite for growth and metastasis of solid tumors. Several factors, both inducers and inhibitors, play essential roles in the regulation of the angiogenic process. Exposure to sex steroids increases the risk of breast cancer but the mechanisms are poorly understood and the importance of angiogenesis in breast carcinogenesis is undefined. In the female reproductive tract ovarian hormones tightly regulate angiogenesis. The breast is also a target organ for sex steroids but very little is known about sex steroid effects on angiogenesis in normal breast tissue and breast cancer. In this review several regulators of angiogenesis, and their relation to sex steroids, in breast tissue are discussed. Increased knowledge in this area is of utmost importance for future therapeutic treatment options and for breast cancer prevention.

Angiogenesis Inducing Agents↗
PubMed2001

Angiogenesis: regulators and clinical applications.

Angiogenesis is a fundamental process in reproduction and wound healing. Under these conditions, neovascularization is tightly regulated. Unregulated angiogenesis may lead to several angiogenic diseases and is thought to be indispensable for solid tumor growth and metastasis. The construction of a vascular network requires different sequential steps including the release of proteases from "activated" endothelial cells with subsequent degradation of the basement membrane surrounding the existing vessel, migration of endothelial cells into the interstitial space, endothelial cell proliferation, and differentiation into mature blood vessels. These processes are mediated by a wide range of angiogenic inducers, including growth factors, chemokines, angiogenic enzymes, endothelial specific receptors, and adhesion molecules. Finally, when sufficient neovascularization has occurred, angiogenic factors are down-regulated or the local concentration of inhibitors increases. As a result, the endothelial cells become quiescent, and the vessels remain or regress if no longer needed. Thus, angiogenesis requires many interactions that must be tightly regulated in a spatial and temporal manner. Each of these processes presents possible targets for therapeutic intervention. Synthetic inhibitors of cell invasion (marimastat, Neovastat, AG-3340), adhesion (Vitaxin), or proliferation (TNP-470, thalidomide, Combretastatin A-4), or compounds that interfere with angiogenic growth factors (interferon-alpha, suramin, and analogues) or their receptors (SU6668, SU5416), as well as endogenous inhibitors of angiogenesis (endostatin, interleukin-12) are being evaluated in clinical trials against a variety of solid tumors. As basic knowledge about the control of angiogenesis and its role in tumor growth and metastasis increases, it may be possible in the future to develop specific anti-angiogenic agents that offer a potential therapy for cancer and angiogenic diseases.

Angiogenesis Inducing Agents↗
PubMed2001

[Anti-angiogenesis - a therapy concept in the treatment of head and neck carcinomas? A review].

BACKGROUND: Head and neck squamous cell carcinoma (HNSCC) is an aggressive malignancy that is now the sixth most common neoplasm in the world. Despite numerous advances in treatment, the long-term survival has remained the same for the last 25 years. Angiogenesis has been shown to be important for HNSCC tumour growth and metastasis. Therefore, inhibitors of angiogenesis are a new class of anti-neoplastic substances that might be a powerful complement to conventional therapy in HNSCC. MATERIAL AND METHODS: The role of angiogenesis in HNSCC as well as preclinical and clinical trials concerning inhibitors of tumor-angiogenesis are discussed here. RESULTS: Many of the investigated angiogenesis inhibitors demonstrated anti-tumor effects in preclinical and clinical trials. In a few cases, partial remission was observed. CONCLUSIONS: Anti-angiogenic therapy will undoubtly have the potential to change standard tumor therapies. Some anti-angiogenic substances appear to be promising candidates for a clinical use in the therapy of HNSCC.

Adult↗
PubMed2004

Hirudo medicinalis: avascular tissues for clear-cut angiogenesis studies?

Basic studies on angiogenesis in normal and pathologic conditions, as well as research on drugs or genes/proteins that stimulate or regulate the angiogenic process, can rely on an increasing number of experimental models. Among non-mammalian models, Zebrafish is adopted by an increasing number of research groups. Moreover, angiogenesis and vasculogenesis in invertebrates like the leech Hirudo medicinalis share a high degree of similarity with the same processes occurring in humans, both under the structural/functional and biochemical points of view. Interestingly, Hirudo angiogenic growth factor receptors respond to corresponding human/mammalian recombinant growth factors and cytokines; in addition, Hirudo endogenous angiogenic growth factors and receptors react with antibodies against their human/mammalian counterparts. Furthermore, as it will be shown in this review, Hirudo has the unique advantage of having a virtually avascular muscular body wall, whereas the reliability of such a peculiar feature as a model for physiologically vascularised mammalian tissues has to be thoroughly investigated. Hirudo has proven so far to allow unambiguous, clear-cut studies on the angiogenic potential of gene-products or drugs, as well as on the anti-angiogenic compounds. This article will review the biology of angiogenesis in Hirudo and the data so far collected on angiogenesis stimulation/modulation in this model; an example describing a study on the biological activity of a naked DNA vector for angiogenesis gene therapy will also be provided.

Angiogenesis Inducing Agents↗
PubMed2004

CXCL1/macrophage inflammatory protein-2-induced angiogenesis in vivo is mediated by neutrophil-derived vascular endothelial growth factor-A.

The angiogenic activity of CXC-ELR(+) chemokines, including CXCL8/IL-8, CXCL1/macrophage inflammatory protein-2 (MIP-2), and CXCL1/growth-related oncogene-alpha in the Matrigel sponge angiogenesis assay in vivo, is strictly neutrophil dependent, as neutrophil depletion of the animals completely abrogates the angiogenic response. In this study, we demonstrate that mice deficient in the src family kinases, Hck and Fgr (hck(-/-)fgr(-/-)), are unable to develop an angiogenic response to CXCL1/MIP-2, although they respond normally to vascular endothelial growth factor-A (VEGF-A). Histological examination of the CXCL1/MIP-2-containing Matrigel implants isolated from wild-type or hck(-/-)fgr(-/-) mice showed the presence of an extensive neutrophil infiltrate, excluding a defective neutrophil recruitment into the Matrigel sponges. Accordingly, neutrophils from hck(-/-)fgr(-/-) mice normally migrated and released gelatinase B in response to CXCL1/MIP-2 in vitro, similarly to wild-type neutrophils. However, unlike wild-type neutrophils, those from hck(-/-)fgr(-/-) mice were completely unable to release VEGF-A upon stimulation with CXCL1/MIP-2. Furthermore, neutralizing anti-VEGF-A Abs abrogated the angiogenic response to CXCL1/MIP-2 in wild-type mice and CXCL1/MIP-2 induced angiogenesis in the chick embryo chorioallantoic membrane assay, indicating that neutrophil-derived VEGF-A is a major mediator of CXCL1/MIP-2-induced angiogenesis. Finally, in vitro kinase assays confirmed that CXCL1/MIP-2 activates Hck and Fgr in murine neutrophils. Taken together, these data demonstrate that CXCL1/MIP-2 leads to recruitment of neutrophils that, in turn, release biologically active VEGF-A, resulting in angiogenesis in vivo. Our observations delineate a novel mechanism by which CXCL1/MIP-2 induces neutrophil-dependent angiogenesis in vivo.

Angiogenesis Inducing Agents↗