Potential role of the angiopoietin/tie2 system in ischemia-induced retinal neovascularization

PURPOSE

Ischemia-induced neovascularization can cause catastrophic loss of vision in retinal disorders such as diabetic retinopathy. Recent studies have shown that the angiopoietin-Tie2 system is a major regulator of vascular integrity and is involved in pathologic angiogenesis. In the study described herein, the role of these molecules in ischemic retinal disorders was investigated.

METHODS

Human epiretinal membranes were examined by immunohistochemistry, In situ hybridization, and reverse transcription-polymerase chain reaction (RT-PCR) analysis. Effects of angiopoietins on tube formation were studied in vitro in bovine retinal capillary endothelial cells (BRECs) and in a murine model of ischemia-induced retinal neovascularization.

RESULTS

In human epiretinal membranes surgically obtained from eyes with ischemic retinal disorders, substantial upregulation of angiopoietin 2 (Ang2) and the receptor Tie2 was recorded than in those from eyes with nonischemic diseases, whereas expression of Ang1 was constant in all membranes. Both Ang1 and Ang2 promoted tube-forming activity and enhanced the effects of vascular endothelial growth factor (VEGF) in cultured BRECs. Soluble Tie2 fusion protein (sTie2-Fc), which precluded modulation of VEGF-dependent tube formation by the angiopoietins, suppressed both VEGF and hypoxia-conditioned, medium-induced tube-forming activity in BRECs. Intravitreal injection of sTie2-Fc, soluble Flt-1 fusion protein (sFlt-1-Fc), and both chimeric proteins suppressed retinal angiogenesis in a murine model of retinal ischemia in the order of sTie2-Fc < sFlt-1-Fc < sTie2-Fc+sFlt-1-Fc.

CONCLUSIONS

These results reinforce the substantial role of the angiopoietins/Tie2 system in ischemia-induced angiogenesis as well as the VEGF system and suggest that combined inhibition of Tie2 and VEGF signaling may be more effective in halting or preventing pathologic angiogenesis in ischemic retinal disorders.

Use of adenovirus vectors for functional gene analysis in the chicken chorioallantoic membrane

The chicken chorioallantoic membrane (CAM) assay represents one of the most widely used in vivo screening assay for genes with angiogenic (blood vessel-inducing) or angiostatic (inhibition of vessel formation or their destruction) activities. Here we show that adenovirus gene transfer vectors infect cells in the CAM and lead to expression of the viral transgene. Furthermore, infection with an adenovirus vector containing the human vascular endothelial growth factor gene induced the formation of new blood vessels. This improved method saves a considerable amount of time in the identification of genes that can influence blood vessel formation because the expensive and time-consuming production and purification of recombinant protein can be omitted.

CDT6-expression can alter tumor sensitivity to chemotherapy

BACKGROUND

Cornea-derived transcript 6 (CDT6 = AngX) has been shown to have an anti-tumor effect.

MATERIALS AND METHODS

We transfected the murine melanoma cell line B16-F10 with the CDT6 gene and compared the sensitivity to cytostatic drugs of the resulting cell line, B16-CDT6, to that of the empty vector-transfected control cell line B16-CMV.

RESULTS

The B16-CDT6 line showed a significantly increased sensitivity to doxorubicin as well as a tendency towards a decreased sensitivity to cisplatin. To further resolve the mechanism of the increase in sensitivity to doxorubicin, we also tested the cytotoxic agents vincristine, etoposide and taxol. However no difference in sensitivity for these drugs was found between the B16-CDT6 and the control cell line.

CONCLUSION

CDT6 increased the sensitivity to doxorubicin in a mechanism probably not related to interference with the efflux pumps MRP, Pgp or the DNA-associated target enzyme topoisomerase II. Altered gene expression induced by gene therapy might influence tumor sensitivity to chemotherapy.

[The molecular genetics of rheumatoid arthritis disease gene]

Rheumatoid arthritis(RA) is a chronic polyarthritis of unknown etiology affecting approximately 1% of the population worldwide. Previous studies have shown that the ratio of the risk for siblings of patients with the disease versus the prevalence of that disease in the general population (lambda s) is much greater in RA, suggesting that genetic factors may be involved in familial clustering. Using microsatellite marker analysis and sib-pair linkage study, we have identified three chromosome regions D1S214/253, D8S556 and DXS1232/984 as candidate loci for RA disease genes. In this article, we review the molecular genetic findings on the RA disease genes located respectively at each of the above chromosome regions. We show that the death receptor 3(DR3) gene, a Fas family member, containing nucleotide polymorphism is the candidate disease gene located at D1S214/253. We also identify the mutant forms of angiopoietin-1(Ang-1) and Dbl proto-oncogenes respectively as the candidate genes located at D8S556 and DXS1232/984. We surmise that these mutations are responsible for the impairment of apoptosis induction, angiogenesis and leukocyte function in the patients, which may predispose to autoimmunity.

Angiogenic gene therapy

Angiogenesis, which is defined as the outgrowth of nutritive vessels from locally preexisting ones, is primarily based on the outgrowth of locally present endothelial cells and implies a delicate balance where both stimulating and inhibitory factors can influence the outcome. The primary players starting the process are the vascular endothelial growth factors (VEGFs), which stimulate endothelial cell growth, although some other key factors such as fibroblast growth factors (FGFs), placental growth factors (PIGFs), platelet-derived growth factors (PDGFs) and angiopoietins must come into play for vessels to mature and not deteriorate. Two possibilities exist in terms of local delivery of the angiogenic proteins. One is the delivery of the protein in a slow-release formulation. Fibrin or alginate formulations have been implanted, sub-epicardially releasing FGF. Another approach to get a local delivery over a period of time is gene therapy by local delivery of the vector carrying the therapeutic gene or with the development of vectors that are taken up and expressed only in the organ of interest. A transient overexpression, desirable for the treatment of ischemic heart disease, can be achieved with adenoviral vectors or naked plasmid. With VEGF gene transfection, angiogenesis and reendothelialization were demonstrated in animal cardiac ischemia models showing proof of principle for cardiac therapy and paving the way for clinical trials. Currently, about 200 patients have been treated with intramyocardial VEGF gene therapy for peripheral occlusive artery disease or for myocardial ischemia. Reported adverse events have been few and no worsening of atherosclerosis following treatment has been observed.

Angiogenesis induced by advanced glycation end products and its prevention by cerivastatin

We previously have found that advanced glycation end products (AGE), senescent macroproteins formed at an accelerated rate in diabetes, arise in vivo not only from glucose but also from reducing sugars. Furthermore, we recently have shown that glyceraldehyde- and glycolaldehyde-derived AGE (glycer- and glycol-AGE) are mainly involved in loss of pericytes, the earliest histopathological hallmark of diabetic retinopathy. However, the effects of these AGE proteins on angiogenesis, another vascular derangement in diabetic retinopathy, remain to be elucidated. In this study, we investigated whether these AGE proteins elicit changes in cultured endothelial cells that are associated with angiogenesis. When human skin microvascular endothelial cells (EC) were cultured with glycer-AGE or glycol-AGE, growth and tube formation of EC, the key steps of angiogenesis, were significantly stimulated. The AGE-induced growth stimulation was significantly enhanced in AGE receptor (RAGE)-overexpressed EC. Furthermore, AGE increased transcriptional activity of nuclear factor-kB (NF-kB) and activator protein-1 (AP-1) and then up-regulated mRNA levels of vascular endothelial growth factor (VEGF) and angiopoietin-2 (Ang-2) in EC. Cerivastatin, a hydroxymethylglutaryl CoA reductase inhibitor; pyrrolidinedithiocarbamate; or curcumin was found to completely prevent the AGE-induced increase in NF-kB and AP-1 activity, VEGF mRNA up-regulation, and the resultant increase in DNA synthesis in microvascular EC. These results suggest that the AGE-RAGE interaction elicited angiogenesis through the transcriptional activation of the VEGF gene via NF-kB and AP-1 factors. By blocking AGE-RAGE signaling pathways, cerivastatin might be a promising remedy for treating patients with proliferative diabetic retinopathy.

Effects of vascular endothelial growth factor (VEGF)A and VEGFB gene transfer on vascular reserve in a conscious rabbit hindlimb ischaemia model

1. As a result of the ageing population, there are increasing numbers of patients with severe peripheral vascular occlusive disease associated with intermittent claudication (pain on walking) and decreased exercise tolerance. There is a great clinical need for pharmacological treatments that may stimulate collateral blood vessel growth, increase vascularity and improve skeletal muscle function. 2. Therapeutic angiogenesis using growth factors such as vascular endothelial growth factor (VEGF) has been used to improve collateral artery development in myocardial or skeletal muscle ischaemia. The broad aims of the work briefly summarized here were to compare the effects of VEGFA165 and VEGFB167 (500 micro g, i.m., gene transfer) on calf blood pressure ratio and reactive hyperaemia in a chronic rabbit preparation with unilateral limb ischaemia. 3. Unilateral femoral artery ligation caused an immediate deficit (compared with the contralateral limb) of 72% in calf systolic blood pressure. There were improvements 14 days after ligation with VEGFA and VEGFB treatments compared with the vehicle control plasmid treatment, but a deficit remained of some 32%. 4. Reactive hyperaemic responses were significantly attenuated 7 days after ligation in the vehicle and VEGFA treatment groups. On day 14, this loss of vascular reserve was restored in the VEGFA group, but remained in the vehicle group (-30%). In VEGFB-treated animals, there was no deficit in reserve 7-14 days post-ligation. 5. In conclusion, there is considerable value in the serial measurements of calf blood pressure ratio and reactive hyperaemia in the rabbit unilateral hindlimb ischaemia model. Gene transfer of either VEGFA or VEGFB allowed significant improvements in these indices compared with vehicle but, at 14 days post-ligation, large deficits still remained. Studies extending this experimental period are in progress.

Human vascular endothelial growth factor B: characterization of recombinant isoforms and generation of neutralizing monoclonal antibodies

1. The vascular endothelial growth factor (VEGF) family is a focus of interest with respect to novel therapies for cardiovascular disease. Members of this family bind differentially to three receptor tyrosine kinases, namely VEGF-R1, -R2 and -R3, and to the semaphorin receptors neuropilin 1 and 2. The role of VEGF-R1 and the factors that interact exclusively with this receptor (VEGF-B and placenta growth factor) has remained controversial. 2. To further elucidate the role of VEGF-B in blood vessel formation and function, we have expressed, purified and refolded both naturally occurring VEGF-B isoforms and a truncated amino acid 10-108 form. All refolded proteins have been demonstrated to bind to VEGF-R1 with appropriate kinetics in biosensor-based analysis. 3. Robust cell assays for VEGF-R1 ligands, such as VEGF-B, have been problematic. We have developed an assay based on a chimeric receptor consisting of extracellular domains 1-4 of VEGF-R1 and the transmembrane and intracellular domains of gp130. The cell line expresses luciferase to high levels 24 h after exposure to VEGF-A and both refolded VEGF-B167 and the short 10-108 isoform have been demonstrated to be active in this assay. 4. The novel cell-based assay, in combination with a variety of immunochemical approaches, has been used to identify and characterize monoclonal antibodies that neutralize VEGF-B activity.

Angiopoietin-1 and vascular endothelial growth factor expression in human esophageal cancer

Angiopoietin-1 (Ang-1) has been shown to act as an angiogenic promoter in embryonic angiogenesis by promoting vascular branching, pericyte recruitment and endothelial survival. Ang-1 expression has not been examined in human esophageal cancer. We examined Ang-1 and vascular endothelial growth factor (VEGF) gene expression in tumors from 45 esophageal cancer patients who underwent surgical resection. Forty (88.9%) of the 45 esophageal cancers revealed Ang-1 gene expression. VEGF121, VEGF165 and VEGF189 isoforms were detected in 93.3 (42/45), 55.6 (25/45) and 26.7% (12/45) of the cases, respectively. Ang-1 gene expression was significantly correlated with VEGF121 and VEGF165 gene expression (P=0.0289 and P=0.0127, respectively, Fisher's test). The results suggest that Ang-1 is associated with neovascularization in the cancer stroma through VEGF net-works in esophageal cancer.

Expression of angiogenic and neurotrophic factors in the human amnion and choriodecidua

OBJECTIVE

Our objective was to identify the novel or differential expression of growth or development associated genes in the human gestational membranes that might play roles in pregnancy or in term or preterm parturition.

STUDY DESIGN

Complementary DNA arrays were probed with [alpha(33)P]dCTP-labeled-complementary DNA that was prepared from the RNA of reflected amnion and choriodecidua that represent term not-in-labor, term spontaneous labor, and preterm labor with and without chorioamnionitis (n = 4 per group). Differential expression (term not-in-labor vs term spontaneous labor or preterm labor with chorioamnionitis vs preterm labor without chorioamnionitis) was evaluated by Wilcoxon tests.

RESULTS

All 16 amnion samples expressed angiogenic factors (endothelin-2 and -3, vascular endothelial growth factor, and vascular endothelial growth factor-B) and neurotrophic factors (ephrin-A2, ephrin receptors-A2, -B1, -B3, -B4, and -B5, neuropilin-2, p75/nerve growth factor receptor and semaphorin-F). In both amnion and choriodecidua, the expression of vascular endothelial growth factor and the angiopoietin receptor, Tie-2, were greater with term spontaneous labor than with term not-in-labor (P <.05); increased VEGF receptor-2 (flk-1) expression was observed in term spontaneous labor choriodecidua (P <.05) but not amnion. Ephrin-A1 expression increased with term spontaneous labor in both tissues (P <.05). Semaphorin-F expression decreased with preterm labor with chorioamnionitis in choriodecidua (P <.05), although the trend was not significant in amnion (P =.1).

CONCLUSION

Neurotrophic and angiogenic factor genes are expressed in amnion and choriodecidual membranes. Several of the genes exhibit differential expression with labor at term or in association with infection preterm, which suggests roles in or associated with these processes.

Correlation between interleukin 10 and vascular endothelial growth factor expression in human esophageal cancer

Interleukin 10 (IL-10) is an immunosuppressive cytokine produced by T-lymphocytes, and is a regulatory molecule for angiogenesis in various cancers. We examined IL-10 and vascular endothelial growth factor (VEGF) gene expression in 45 esophageal cancer patients who underwent surgical resection. Thirty-seven (82.2%) of the 45 esophageal cancers revealed IL-10 gene expression. VEGF121, VEGF165 and VEGF189 isoforms were detected in 93.3% (42/45), 55.6% (25/45) and 26.7% (12/45) of cases, respectively. IL-10 gene expression was significantly correlated with VEGF121 gene expression (P=0.0039, Fisher's test). The results suggested that IL-10 stimulates angiogenic factor gene expression.

Expression of CYR61, an angiogenic immediate early gene, in arteriosclerosis and its regulation by angiotensin II

BACKGROUND

The renin-angiotensin system is thought to be involved in development and progression of arteriosclerosis, thereby contributing to adverse cardiovascular events. To elucidate the role of angiotensin II (Ang II) at a cellular level, we analyzed the Ang II-induced gene expression profile.

METHODS AND RESULTS

Genes induced on Ang II stimulation (10(-7) mol/L, 45 minutes) in rat smooth muscle cells were analyzed by polymerase chain reaction selected subtraction. In addition to known genes, such as interleukin 6, leukemia inhibitory factor, and c-fos, we identified CYR61, an angiogenic immediate early gene. Northern blot analysis revealed a rapid 2.5-fold increase of CYR61 transcript levels by Ang II, peaking at 30 minutes, which was blunted by Ang II type 1 receptor blockade. Exposure of rat aortic rings to Ang II (30 minutes) revealed a 2-fold, and intraperitoneal injection of Ang II (30 minutes) in mice a 3-fold, increase of aortic CYR61 transcripts. In arteriosclerotic aortas of apolipoprotein E-deficient mice, CYR61 transcripts confirmed by in situ hybridization and proteins shown by immunohistochemistry were elevated, whereas they were hardly detectable in wild types. In human carotid atherectomies and arteriosclerotic coronary arteries, immunohistochemical analysis revealed expression of CYR61 within connective tissue in neointima, adventitia, and surrounding small capillaries and blood vessels, colocalized with ACE and Ang II. Normal human arteries showed no significant staining for CYR61.

CONCLUSIONS

CYR61, an angiogenic factor, is induced by Ang II in vascular cells and tissue. The expression of CYR61, colocalized with Ang II and ACE, in small vessels of human arteriosclerotic lesions is consistent with the notion that the activated renin-angiotensin system may contribute to plaque neovascularization by enhancing regulators of microvessel formation and cell proliferation.

Up-regulated gene expression of angiogenesis factors in post-chemotherapeutic lung cancer tissues determined by cDNA macroarray

The differential expressions of hundreds of tightly transcriptionally controlled genes in freshly isolated human lung cancers and respective normal lung tissues were analyzed by the cDNA macroarray technique. Three lung cancer patients received pre-operative chemotherapy with cisplatin containing regimens. After chemotherapy, these patients underwent surgery, and poly (A)-RNA expressions of 588 genes in the samples prepared from the lung cancer and normal lung tissues were compared. These expressions of the 588 genes were demonstrated by spotting onto a filter. Histogram analysis of gene expression revealed the tumors to show commonly up-regulated expression of angiogenesis and invasion related genes and adhesion molecules such as fibroblast growth factor 3 (FGFR3), matrix metalloproteinase (MMP)15, 16 and 10, integrin beta 4, integrin alpha 9, endonexin, and several types of collagens. Thus, post-chemotherapeutic tissues from lung cancer parents are characterized by remarkable up-regulation of molecules related to angiogenesis, invasion and adhesion. Tree view showed close clustering of angiogenesis related genes. Furthermore, when the angiogenesis related genes were selected and clustered, they were categorized into three groups depending upon gene expression profiles. These results suggest that angiogenesis related molecules are suitable candidates for target-based therapeutics and angiogenesis inhibitors are expected to be effective in lung cancer patients pretreated with chemotherapy.

Expression and localization of angiogenin in placenta: enhanced levels at term over first trimester villi

Human angiogenin, a 14-kDa non-glycosylated polypeptide with both angiogenic and ribonucleolytic activities, is implicated in angiogenesis, a complex process of proliferation and formation of new capillary blood vessels from existing blood vessels. Placental growth requires extensive angiogenesis, which develops its vascular structure in both fetal chorionic villi and maternal deciduas. In this study, we investigated the expression profiles of angiogenin in placental villi from early and late gestation at both mRNA and protein levels using explant cultures in vitro followed by RT-PCR, immunoblot, and immunohistochemical analyses. From functionally active placental explants, angiogenin was detected in conditioned media of all the samples from first trimester and term group. The mean levels of angiogenin produced by term villi were found to be 2.6-, 2.1-, and 2.2-fold higher (P < 0.01) than first trimester villi at 24, 48, and 72 hr of culture, respectively. Expression profiles of angiogenin from term and first trimester villi seem to agree with its mRNA levels and immunoblot analysis; the expression in term villi was twice that in first trimester villi. The presence of angiogenin in placental villi and upregulation of its production towards term indicate that angiogenin production by the placenta is specific to the developmental stage. In conclusion, the observed changes in the localization and mRNA expression of angiogenin during placental development raise the possibility that it is involved in morphological and angiogenic changes in this endocrine organ vital to the successful fetal outcome during pregnancy.

Angiogenic gene therapy for experimental critical limb ischemia: acceleration of limb loss by overexpression of vascular endothelial growth factor 165 but not of fibroblast growth factor-2

Recent studies suggest the possible therapeutic effect of intramuscular vascular endothelial growth factor (VEGF) gene transfer in individuals with critical limb ischemia. Little information, however, is available regarding (1) the required expression level of VEGF for therapeutic effect, (2) the related expression of endogenous angiogenic factors, including fibroblast growth factor-2 (FGF-2), and (3) the related adverse effects due to overexpression of VEGF. To address these issues, we tested effects of overexpression of VEGF165 using recombinant Sendai virus (SeV), as directly compared with FGF-2 gene transfer. Intramuscular injection of SeV strongly boosted FGF-2, resulting in significant therapeutic effects for limb salvage with increased blood perfusion associated with enhanced endogenous VEGF expression in murine models of critical limb ischemia. In contrast, VEGF165 overexpression, 5-times higher than that of baseline on day 1, also strongly evoked endogenous VEGF in muscles, resulting in an accelerated limb amputation without recovery of blood perfusion. Interestingly, viable skeletal muscles of either VEGF165- or FGF-2-treated ischemic limbs showed similar platelet-endothelial cell adhesion molecule-1-positive vessel densities. Maturation of newly formed vessels suggested by smooth muscle cell actin-positive cell lining, however, was significantly disturbed in muscles with VEGF. Further, therapeutic effects of FGF-2 were completely diminished by anti-VEGF neutralizing antibody in vivo, thus indicating that endogenous VEGF does contribute to the effect of FGF-2. These results suggest that VEGF is necessary, but should be delicately regulated to lower expression to treat ischemic limb. The therapeutic effect of FGF-2, associated with the harmonized angiogenic effects seen with endogenous VEGF, provides important insights into therapeutic angiogenesis.

Expression of angiopoietin-2 and vascular endothelial growth factor in mice cerebral cortex after permanent focal cerebral ischemia

AIM

To study the expressions of vascular endothelial growth factor (VEG F), angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), Tie-1, and Tie-2 in C57BL/6 mouse brain after permanent focal cerebral ischemia.

METHODS

The mRNA levels of VEGF, Ang-1, Ang-2, Tie-1, and Tie-2 were measured by semiquantitative reverse transcription polymerase chain reaction (RT-PCR). The protein express ions of VEGF and Ang-2 were determined by immunohistochemistry.

RESULTS

Low mRNA levels of VEGF, Ang-1, Ang-2, Tie-1, and Tie-2 were constitutively expressed in the normal cortex of mouse. After middle cerebral artery occlusion (MCAO), the expressions of VEGF, Ang-2, and Tie-2 mRNA were dramatically increased in the infarcted cortex and the elevation was remained through 7 d of ischemia. However, the levels of Ang-1 and Tie-1 mRNA were unchanged in the infarcted cortex. Immunoreactivities of Ang-2 or VEGF were hardly observed in the normal cortex. Ang-2 protein was evidently detected in the infarct core 8 h after MCAO and in t he perifocal area 1 d after MCAO. Expression of VEGF protein was elevated in the infarct core 2 h after MCAO and in the perifocal area 1 d after MCAO. Immunoreaction was restricted to endothelial cells and glial-like cells within the infarct core and perifocal area.

CONCLUSION

The expressions of An g-2 and VEGF are induced after focal cerebral ischemia, which may contribute to the angiogenic response in the cortex of ischemic brain.

Enhanced expression of vascular endothelial growth factor (VEGF) plays a critical role in the tumor progression potential induced by simian virus 40 large T antigen

Vascular endothelial growth factor (VEGF), an important angiogenic factor, regulates cell proliferation, differentiation, and apoptosis through activation of its tyrosine-kinase receptors, such as Flt-1 and Flk-1/Kdr. Human malignant mesothelioma cells (HMC), which have wild-type p53, express VEGF and exhibit cell growth increased by VEGF. Here, we demonstrate that early transforming proteins of simian virus (SV) 40, large tumor antigen (Tag) and small tumor antigen (tag), which have been associated with mesotheliomas, enhanced HMC proliferation by inducing VEGF expression. SV40-Tag expression potently increased VEGF protein and mRNA levels in several HMC lines. This effect was suppressed by the protein synthesis inhibitor, cycloheximide. Inactivation of the VEGF signal transduction pathway by expression of soluble form of Flt-1 inhibited Flk-1/Kdr activation and HMC proliferation induced by SV40 early genes. Experiments with SV40 mutants revealed that SV40-Tag, but not -tag, is involved in the VEGF promoter activation. However, concomitant expression of SV40-tag enhanced Tag function. In addition, SV40-Tag expression sustained VEGF induction in colon carcinoma cell line (CCL)-233, which have wild-type p53, but not in CCL-238, which lack functional p53. These data indicate that VEGF regulation by SV40 transforming proteins can represent a key event in SV40 signaling relevant for tumor progression.

Adrenomedullin promotes formation of xenografted endometrial tumors by stimulation of autocrine growth and angiogenesis

The angiogenic peptide adrenomedullin (ADM) has been implicated as a mediator of the increased risk of endometrial hyperplasia and cancer resulting from the use of tamoxifen for the treatment and prevention of breast cancer. ADM has been shown to be induced by tamoxifen in the endometrium and to be a growth factor for endometrial endothelial cells in vitro. We have now shown ADM to be strongly angiogenic in the mouse subcutaneous sponge angiogenesis assay. To examine the role of ADM in tumor growth, the ADM cDNA was transfected into endometrial carcinoma cells followed by xenografting into athymic mice. Two endometrial cancer cell lines were employed, those in which transfection and expression of ADM resulted in no effect on growthin vitro (Ishikawa cells) and those in which expressionof exogenous ADM stimulated in vitro growth (RL95.2 cells). A clear enhancement of tumor growth was seen with both cell lines but the effect was far greater with the RL95.2 cells. We conclude that ADM is pro-tumorigenic by stimulating either angiogenesis alone or by stimulating angiogenesis and carcinoma cell growth directly. The combined activities lead to a striking increase in tumor growth. These results provide the first direct evidence of tumorigenic activity of ADM and provide further support for ADMs involvement in tamoxifen induced endometrial neoplasia.

Role of placenta growth factor in cardiovascular health

Placenta growth factor (PlGF), a member of the cysteine-knot family, is an angiogenic protein. The PlGF gene has been conserved across different species of the animal kingdom. It is expressed primarily in the placenta, especially in the later stages of gestation. PlGF expression is upregulated during pathological conditions such as ischemia of the heart and myocardial infarction. It is now known that PlGF can modulate the activity of vascular endothelial growth factor, the most potent of all angiogenic inducers and hence makes it an attractive target for therapeutic strategies. Recent structural studies on different isoforms of PlGF promise to reveal important topological and molecular details of these proteins that may be of potential use in the design of effective small molecule inhibitors to combat pathological angiogenesis.

Biomedical significance of endothelial cell specific growth factor, angiopoietin

Until recently, vascular endothelial growth factor (VEGF) was the only growth factor proven to be specific and critical for blood vessel formation. Other long-known factors, such as the fibroblast growth factors (FGFs), platelet-derived growth factor, or transforming growth factor-beta, had profound effects in endothelial cells. But such factors were nonspecific, in that they could act on many other cells, and it seemed unlikely that these growth factors would be effective targets for treatment of endothelial cell diseases. A recently discovered endothelial cell specific growth factor, angiopoietin, has greatly contributed to our understanding of the development, physiology, and pathology of endothelial cells (Davis et al., 1996; Yancopoulos et al., 2000). The recent studies that identified and characterized the physiological and pathological roles of angiopoietin have allowed us to widen and deepen our knowledge about blood vessel formation and vascular endothelial function. Therefore, in this review, we describe the biomedical significance of these endothelial cell growth factors, the angiopoietins, in the vascular system under normal and pathological states.

Inhibition of constitutive NF-kappa B activity suppresses tumorigenicity of Ewing sarcoma EW7 cells

Ewing sarcoma is 1 of the most aggressive tumors that can affect children and young adults. Despite advances in therapy, the prognosis remains poor emphasizing the need for defining new targets for treatment. We investigated a possible role of nuclear factor-kappa B (NF-kappa B) activity of Ewing sarcoma-derived EW7 cells in their tumorigenicity. In these cells, expression of a degradation-resistant form of the inhibitory factor I kappa B alpha inhibited NF-kappa B activity without affecting their in vitro proliferation rate. It causes, however, a remarkable loss of their ability to generate tumors in nude mice that correlates with both a decrease in extracellular matrix (ECM) protein secretion and an acquisition of sensitivity to murine tumor necrosis factor alpha (TNF alpha)-induced apoptosis. These data support the concept that NF-kappa B activity plays a role in the tumorigenicity of Ewing sarcoma cells, identifying NF-kappa B as a potential target for reducing Ewing tumor progression.

The prognostic value of metalloproteinases and angiogenic factors in ovarian carcinoma

The objective of this study was to analyze the correlation between matrix metalloproteinases (MMPs) and angiogenic genes and survival in advanced-stage ovarian carcinomas. Primary and metastatic ovarian carcinomas from patients diagnosed with FIGO stage III-IV disease and followed up to 20 years were studied using mRNA in situ hybridization (ISH). Expression of MMP-2, MMP-9, membrane-type 1-MMP (MT1-MMP), the MMP inhibitor TIMP-2, vascular endothelial growth factor (VEGF), interleukin-8 (IL-8) and basic fibroblast growth factor (bFGF) was studied. MMP-2, MMP-9 and TIMP-2 mRNA was detected in both tumor and stromal cells, while MT1-MMP was largely confined to tumor cells. In univariate analysis of primary tumors, TIMP-2 and MMP-9 mRNA expression correlated with poor outcome. In metastatic lesions, mRNA expression of TIMP-2, MMP-2, and MT1-MMP correlated with poor survival. In a multivariate analysis of primary tumors, TIMP-2 expression in stromal cells (P=0.006) and MMP-9 expression in tumor cells (P=0.011) retained their predictive value. Intense expression of bFGF mRNA and weak expression of IL-8 mRNA was detected in both stromal and tumor cells in most cases, while VEGF mRNA expression was limited to a few cases. Angiogenic mRNA expression showed no correlation with disease outcome in survival analysis (P>0.05). We conclude that bFGF is the major angiogenic factor expressed in ovarian carcinoma at the mRNA level. MMP-2, MMP-9, MT1-MMP and TIMP-2 are valid markers of poor survival in advanced-stage ovarian carcinoma.

Postischemic angiogenic factor expression in stroke-prone rats

Spontaneously hypertensive stroke-prone rats (SHRSP), a model for genetic stroke susceptibility, suffer spontaneous stroke and enhanced injury after experimental stroke, in part due to abnormal cerebrovascular development. We hypothesized that angiopoietin system genes in SHRSP may follow unique patterns of expression after experimentally induced stroke. SHRSP, hypertensive control rats (SHR), and normotensive controls (WKY) were subjected to experimental middle cerebral artery occlusion, and brain RNA was analyzed for expression of angiogenic genes. Expression of angiopoietin-2 increased after stroke in all rat strains and was significantly enhanced in SHRSP compared with control strains. In addition, expression of angiopoietin-1 and the angiopoietin receptor dropped markedly after stroke in SHRSP animals, but was not different after ischemia in SHR and WKY strains. Thus, the SHRSP brain elaborates a unique and specific pattern of angiopoietin system gene expression after stroke which may underlie stroke susceptibility of these rats.