A new impedimetric biosensor utilizing VEGF receptor-1 (Flt-1): early diagnosis of vascular endothelial growth factor in breast cancer

A new impedimetric biosensor, based on the use of vascular endothelial growth factor receptor-1 (VEGF-R1), was developed for the determination of vascular endothelial growth factor (VEGF). VEGF-R1 was immobilized through covalent coupling with 3-mercaptopropionic acid which formed a self-assembled monolayer on gold electrodes. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy techniques were employed to characterize the immobilization process and to detect VEGF. To successfully construct the biosensor current, experimental parameters were optimized. Kramers-Kronig Transform was performed on the experimental impedance data. The obtained results provided a linear response range from 10 to 70 pg/mL human VEGF. The applicability of the developed biosensor in the determination of VEGF in a spiked artificial human serum sample was experienced, yielding average recovery of 101%, in that order, with an average relative deviation value less than 5%.     

A Novel Biosensing System Using Biological Receptor for Analysis of Vascular Endothelial Growth Factor

An immunosensor with rapid and ultrasensitive response for vascular endothelial growth factor (VEGF) has been built up with 4-aminothiophenol (4-ATP) onto the gold surfaces. Quantitative analysis of VEGF was performed by recording the impedance changing of the gold electrode surface by binding of VEGF. The human vascular endothelial growth factor receptor 1 (VEGF-R1, Flt-1) was used as a biorecognition element for the first time in the literature. VEGF-R1 was covalently immobilized via 4-ATP self-assembled monolayer formed on gold thin film covered surface. Construction of the biosensor was carefully characterised by the techniques such as electrochemistry and electrochemical impedance spectroscopy. In order to characterize impedance data, Kramers–Kronig transform was performed on the experimental impedance data. The limit of detection of the immunosensor for qualitative detection was 100 pg/mL while the LOD for quantitative detection could down to 100 pg/mL by using the VEGF-R1 based biosensor. Finally, artificial serum samples spiked with VEGF was analyzed by the proposed immunosensor to investigate useful of the biosensor for early biomarker diagnosis.     

Vascular endothelial growth factor, vascular endothelial growth factor receptor-3 and cyclooxygenase-2 expression in psoriasis

OBJECTIVE: To investigate expression patterns and relationship of vascular endothelial growth factor (VEGF), vascular endothelial receptor-3 (VEGF-R3) (FLT-4) and cyclooxygenase-2 (COX-2) in psoriasis. STUDY DESIGN: Forty-three patients were included in this study. The clinical severity of psoriasis was assessed using the psoriasis area and severity index (PASI). Punch biopsy samples both from psoriatic and nonlesional skin were taken and VEGF, VEGF-R3 and COX-2 expressions determined. RESULTS: VEGF, VEGF-R3 and COX-2 expressions were detected in 90.9%, 78.0% and 86.4% of psoriatic and 84.1%, 71.8%, and 84.1% of nonlesional skin, respectively. Epidermal VEGF, VEGF-R3 and COX-2 expressions were detected in 56.8%, 77.8% and 34.1 of psoriatic and 75%, 78.1% and 65.9% of nonlesional skin, respectively. In dermis, VEGF, VEGF-R3 and COX-2 expression was observed in 88.6%, 77.5% and 84.1% of psoriatic and 81.8%, 64.1% and 77.3% of nonlesional skin, respectively. Among the PASI subgroups no statistically significant differences were detected for VEGF, VEGF-R3 and COX-2 expression. CONCLUSION: Our study demonstrated that VEGF, VEGF-R3 and COX-2 expression in psoriatic and nonlesional skin is significantly high in epidermis and dermis. Although there was significant concordance between VEGF and VEGF-R3 expressions in psoriatic lesions, there seems to be no concordance between the others.     

Six placenta permeability-related genes: molecular characterization and expression analysis in pigs

The nutrient transportation ability of placenta depends on placental size, vascular density and permeability. Regulation of angiogenesis in the placenta is critical for successful gestation. Placenta vascularity exhibits disparity in different gestation stages and different pig breeds. To investigate the expression of genes related to permeability in the porcine placenta of different gestation stages and breeds, molecular cloning and gene expression analysis of six porcine genes, vascular endothelial growth factor (VEGF), VEGF-R1, VEGF-R2, endothelial nitric oxide synthase (eNOS), vascular endothelial cadherin (CDH5) and β-arrestin2 (Arrb2), were performed in this study. The results demonstrated that from gestation day 33 to day 90, Landrace exhibited significant increase (P < 0.05) in placental VEGF and Arrb2 mRNA expression. Moreover, expression levels of VEGF, VEGF-R1, VEGF-R2 and eNOS mRNA were higher (P < 0.01) in the placenta of Erhualian than those in Landrace on day 90 of gestation. In contrast, CDH5 placental mRNA expression level exhibited significant decrease (P < 0.05) from day 33 to day 90 gestation in Landrace. Erhualian placental CDH5 and Arrb2 expression levels were significantly lower (P < 0.01) than those in Landrace conceptuses on day 90 of gestation. Our study offered new data on the expression of genes in VEGF signal transduction pathway in porcine placenta.     

Complete structure of an increasing capillary permeability protein (ICPP) purified from Vipera lebetina venom. ICPP is angiogenic via vascular endothelial growth factor receptor signalling

The partial sequence of the increasing capillary permeability protein (ICPP) purified from Vipera lebetina venom revealed a strong homology to vascular endothelial growth factor (VEGF)-A. We now report its complete amino acid sequence determined by Edman degradation and its biological effects on mouse and human vascular endothelial cells. ICPP is a homodimeric protein linked by cysteine disulfide bonds of 25115 Da revealed by mass spectrometry. Each monomer is composed of 110 amino acids including eight cysteine residues and a pyroglutamic acid at the N-terminal extremity. ICPP shares 52% sequence identity with human VEGF but lacks the heparin binding domain and Asn glycosylation site. Besides its strong capillary permeability activity, ICPP was found to be a potent in vitro angiogenic factor when added to mouse embryonic stem cells or human umbilical vein endothelial cells. ICPP was found to be as potent as human VEGF165 in activating p42/p44 MAPK, in reinitiation of DNA synthesis in human umbilical vein endothelial cells, and in promoting in vitro angiogenesis of mouse embryonic stem cells. All these biological actions, including capillary permeability in mice, were fully inhibited by 1 microm of a new specific VEGF receptor tyrosine kinase inhibitor (ZM317450) from AstraZeneca that belongs to the anilinocinnoline family of compounds. Indeed, up to a 30 times higher concentration of inhibitor did not affect platelet-derived growth factor, epidermal growth factor, FGF-2, insulin, alpha-thrombin, or fetal calf serum-induced p42/p44 MAPK and reinitiation of DNA synthesis. Therefore, we conclude that this venom-derived ICPP exerts its biological action (permeability and angiogenesis) through activation of VEGF receptor signaling (VEGF-R2 and possibly VEGF-R1).     

Newly identified biologically active and proteolysis-resistant VEGF-A isoform VEGF111 is induced by genotoxic agents

Ultraviolet B and genotoxic drugs induce the expression of a vascular endothelial growth factor A (VEGF-A) splice variant (VEGF111) encoded by exons 1–4 and 8 in many cultured cells. Although not detected in a series of normal human and mouse tissue, VEGF111 expression is induced in MCF-7 xenografts in nude mice upon treatment by camptothecin. The skipping of exons that contain proteolytic cleavage sites and extracellular matrix–binding domains makes VEGF111 diffusible and resistant to proteolysis. Recombinant VEGF111 activates VEGF receptor 2 (VEGF-R2) and extracellularly regulated kinase 1/2 in human umbilical vascular endothelial cells and porcine aortic endothelial cells expressing VEGF-R2. The mitogenic and chemotactic activity and VEGF111's ability to promote vascular network formation during embyonic stem cell differentiation are similar to those of VEGF121 and 165. Tumors in nude mice formed by HEK293 cells expressing VEGF111 develop a more widespread network of numerous small vessels in the peritumoral tissue than those expressing other isoforms. Its potent angiogenic activity and remarkable resistance to proteolysis makes VEGF111 a potential adverse factor during chemotherapy but a beneficial therapeutic tool for ischemic diseases.     

Vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF) expression during induced luteolysis in the bovine corpus luteum

Angiogenic factors, like vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF), and their receptors, are strongly regulated during the development of bovine corpus luteum (CL). The aim of this study was to investigate real-time changes of these factors in luteal tissue of cows (n = 4-5 per group) in the mid-luteal phase (day 8-12) after intramuscular injection of the PGF2alpha-analog Cloprostenol. Before (control) and 2, 4, 12, 48, and 64 hr after prostaglandin (PG) injection, CL were collected by transvaginal ovariectomy. RT-PCR for VEGF, VEGF-receptor type 1 (VEGF-R1), VEGF-R2, acidic FGF (FGF-1), basic FGF (FGF-2), and FGF-receptor (FGF-R) was performed. Additionally, the protein concentration for VEGF was determined. The mRNA expression of VEGF and its two receptors (VEGF-R1 and -R2) was significantly downregulated during structural luteolysis (after 12 hr). VEGF protein concentration already significantly declined 2 hr after PGF2alpha. Surprisingly FGF-1 and FGF-2 were significantly and maximally upregulated during functional luteolysis (until 12 hr). Furthermore, FGF-R mRNA was significantly upregulated at 2 hr after PGF2alpha, when compared with the control group. During structural luteolysis, the expression of FGFs and their receptors was not significantly different from control, except FGF-2 mRNA, which was downregulated at 64 hr. We conclude that the cessation of VEGF-support for the CL plays a role during structural luteolysis, whereas FGFs seem to have a major impact on functional luteolysis. The possible role of these growth factors could be a transient counter-regulation of luteolysis, but also an involvement in preventing inflammatory reactions during luteal regression.     

Aberrant,ectopic expression of VEGF and VEGF receptors 1 and 2 in malignant colonic epithelial cells. Implications for these cells growth via an autocrine mechanism

Vascular endothelial growth factor A (referred to as VEGF) is implicated in colon cancer growth. Currently, the main accepted mechanism by which VEGF promotes colon cancer growth is via the stimulation of angiogenesis, which was originally postulated by late Judah Folkman. However, the cellular source of VEGF in colon cancer tissue; and, the expression of VEGF and its receptors VEGF-R1 and VEGF-R2 in colon cancer cells are not fully known and are subjects of controversy.     

Circulating vascular endothelial growth factor and its soluble receptors in patients with liver cirrhosis: possible association with hepatic function impairment

Recent studies provided in vivo evidences of an increased angiogenesis in animal model of portal hypertension and cirrhosis which was linked to increased expression of vascular endothelial growth factor. The aim of study was to evaluate the plasma concentration of VEGF and its receptors in liver cirrhosis and the possible association with the degree of liver insufficiency. Methods. Vascular endothelial growth factor (VEGF) and its soluble receptors: sVEGF-R1, sVEGF-R2 were measured in plasma of 78 patients with liver cirrhosis by ELISA. Results. The significant increase of plasma VEGF and sVEGF-R1 was observed in liver cirrhosis compared to healthy individuals (153.1+/-51.9 vs. 46.8+/-4.1pg/mL, P<0.05; 279.8+/-34.3 vs. 105.1+/-5.9pg/mL, P<0.001, respectively). Plasma VEGF and foremost sVEGF R1 showed significant associations with biochemical indices of liver function. Among clinical parameters, only ascites revealed significant association with plasma VEGR and sVEGF-R1. VEGF and sVEGF-R1 were increased respectively to the degree of liver insufficiency. It was demonstrated through a significant positive correlation with Child-Pugh score and MELD classification. In conclusion, our study suggests that serum VEGF and VEGF-R1 may reflect the hepatic function impairment in liver cirrhosis and seems to be associated with portal hypertension symptoms.     

Decay-accelerating factor induction on vascular endothelium by vascular endothelial growth factor (VEGF) is mediated via a VEGF receptor-2 (VEGF-R2)- and protein kinase C-alpha/epsilon (PKCalpha/epsilon)-dependent cytoprotective signaling pathway and is inhibited by cyclosporin A

Decay-accelerating factor (DAF), a membrane-bound complement regulatory protein, is up-regulated on endothelial cells (ECs) following treatment with vascular endothelial growth factor (VEGF), providing enhanced protection from complement-mediated injury. We explored the signaling pathways involved in this response. Incubation of human umbilical vein ECs with VEGF induced a 3-fold increase in DAF expression. Inhibition by flk-1 kinase inhibitor SU1498 and failure of placental growth factor (PlGF) to up-regulate DAF confirmed the role of VEGF-R2. The response was also blocked by pretreatment with phospholipase C-gamma (PLCgamma) inhibitor U71322 and protein kinase C (PKC) antagonist GF109203X. In contrast, no effect was seen with nitric oxide synthase inhibitor N(G)-monomethyl-l-arginine (l-NMMA). Use of PKC agonists and isozyme-specific pseudosubstrate peptide antagonists suggested a role for PKCalpha and -epsilon in VEGF-mediated DAF up-regulation. This was confirmed by transfection of ECs with PKCalpha and -epsilon dominant-negative constructs, which in combination completely abrogated induction of DAF by VEGF. In contrast, LY290042, a phosphoinositide 3-kinase (PI3K) inhibitor, significantly augmented DAF expression, suggesting a negative regulatory role for phosphoinositide 3-kinase. The widely used immunosuppressive drug cyclosporin A (CsA) inhibited DAF induction by VEGF in a dose-dependent manner. The VEGF-induced DAF expression was functionally effective, significantly reducing complement-mediated EC lysis, and this cytoprotective effect was reversed by CsA. These data provide evidence for a VEGF-R2-, phospholipase C-gamma-, and PKCalpha/epsilon-mediated cytoprotective pathway in ECs. This may represent an important mechanism for the maintenance of vascular integrity during chronic inflammation involving complement activation. Moreover, inhibition of this pathway by CsA may play a role in CsA-mediated vascular injury.     

Angiogenesis activators and inhibitors differentially regulate caveolin-1 expression and caveolae formation in vascular endothelial cells. Angiogenesis inhibitors block vascular endothelial growth factor-induced down-regulation of caveolin-1.

Angiogenesis is the process by which new blood vessels are formed via proliferation of vascular endothelial cells. A variety of angiogenesis inhibitors that antagonize the effects of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) have recently been identified. However, the mechanism by which these diverse angiogenesis inhibitors exert their common effects remains largely unknown. Caveolin-1 and -2 are known to be highly expressed in vascular endothelial cells both in vitro and in vivo. Here, we examine the potential role of caveolins in the angiogenic response. For this purpose, we used the well established human umbilical vein endothelial cell line, ECV 304. Treatment of ECV 304 cells with known angiogenic growth factors (VEGF, bFGF, or hepatocyte growth factor/scatter factor), resulted in a dramatic reduction in the expression of caveolin-1. This down-regulation event was selective for caveolin-1, as caveolin-2 levels remained constant under these conditions of growth factor stimulation. VEGF-induced down-regulation of caveolin-1 expression also resulted in the morphological loss of cell surface caveolae organelles as seen by transmission electron microscopy. A variety of well characterized angiogenesis inhibitors (including angiostatin, fumagillin, 2-methoxy estradiol, transforming growth factor-beta, and thalidomide) effectively blocked VEGF-induced down-regulation of caveolin-1 as seen by immunoblotting and immunofluorescence microscopy. However, treatment with angiogenesis inhibitors alone did not significantly affect the expression of caveolin-1. PD98059, a specific inhibitor of mitogen-activated protein kinase and a known angiogenesis inhibitor, also blocked the observed VEGF-induced down-regulation of caveolin-1. Furthermore, we show that caveolin-1 can function as a negative regulator of VEGF-R (KDR) signal transduction in vivo. Thus, down-regulation of caveolin-1 may be an important step along the pathway toward endothelial cell proliferation.     

Expression of Vascular Endothelial Growth Factor A and Its Type 1 Receptor in Supratentorial Neoplasm

Background:Vascular endothelial growth factor (VEGF) is one of the primary angiogenesis regulators in solid cancers. Brain solid tumors are life-threatening diseases in which angiogenesis is an important phase of tumor development and progression. In the present study, VEGF-A and VEGF receptor (VEGF-R1) gene expression was evaluated in CNS brain tumors.Methods:VEGF-A and VEGF-R1 expression was quantified using real-time PCR on fresh biopsies of 38 supratentorial brain tumors compared to 30 non-tumoral tissues. Then, the correlations were investigated with clinic-pathological and demographic factors of the patients.Results:PCR product sequencing confirmed the validity of qRT-PCR. Although VEGF-A and VEGF-R1 expression showed increasing trends with the progression of cell proliferation in different stages of astrocytoma, VEGF-R1 did not meet the 95% confidence interval in other brain tumors. An increasing trend in VEGF-A expression and a declining trend in VEGF-R1 expression from Stage I to II were observed in meningioma. VEGF-A and VEGF-R1 expression had no significant correlation with age and gender. Although peritumoral brain edema (PTBE) in astrocytoma was significantly associated with tumor stages, VEGF-A and VEGF-R1 were not correlated with PTBE in meningioma and metastasis.Conclusion:VEGF-A is a valuable factor for the prognosis of PTBE and malignancy in astrocytoma and is helpful in monitoring treatment approaches.Key Words: Angiogenesis, Brain edema, Brain neoplasm, Peritumoral brain, VEGF, VEGFR1     

Differential expression of the vascular endothelial growth factor-receptor system in the gravid uterus of yorkshire and Meishan pigs

Litter size in the pig is limited by uterine capacity, which is dependent on uterine size, placental size, and vascularity. Placentae of U.S. pig breeds, such as the Yorkshire, exhibit marked growth from mid to late gestation, increasing their surface area of endometrial attachment. In contrast, placentae of the prolific Chinese Meishan pig exhibit little growth from mid to late gestation; instead, they exhibit a marked and progressive increase in the density of placental blood vessels. Vascular endothelial growth factor (VEGF) is a potent angiogenic and permeability-enhancing factor that is produced and secreted by placentae of several species, including the pig. The activity of VEGF is mediated through two specific receptors (VEGF-R1 and VEGF-R2), both of which are expressed by placental and endometrial tissues in pigs and are thought to play a role in mediating increased vascularization and/or permeability at the fetal-maternal interface. The objectives of the present study were to determine concentrations of VEGF in fetal blood and placental fluids as well as placental and adjacent endometrial mRNA expression of VEGF, VEGF-R1, and VEGF-R2 on Days 30, 50, 70, 90, and 110 of gestation in Yorkshire and Meishan pigs. Day 90 Meishan conceptuses exhibited marked increases (P < 0.05) in placental VEGF mRNA expression as well as fetal blood and allantoic fluid concentrations of VEGF, which remained elevated through Day 110. In contrast, Yorkshire conceptuses failed to exhibit increases in placental VEGF mRNA expression or concentrations of VEGF in fetal blood or allantoic fluid until Day 110. Receptor mRNA expression patterns differed between Meishan and Yorkshire conceptuses, but no difference was found in their expression levels. Placental efficiency (fetal weight/placental weight) was higher (P < 0.05) on Days 90 and 110 in Meishan than in Yorkshire conceptuses. The earlier increase in VEGF protein and mRNA expression in the Meishan versus the Yorkshire conceptus may explain the previously reported increased vascularity and increased placental efficiency of this breed compared the Yorkshire breed.     

Angiogenesis and diabetes: different responses to pro-angiogenic factors in the chorioallantoic membrane assay

Hyperglycemia induces defects in angiogenesis without alteration in the expression of major vascular growth factors in the chicken chorioallantoic membrane (CAM) model. A direct negative effect of hyperglycemia on angiogenesis may participate in failures of "therapeutic angiogenesis" trials. Here, we tested the hypothesis that the response to pro-angiogenic molecules such as angiotensin-converting enzyme (ACE), endothelin-1 (ET-1), and vascular endothelial growth factor-A (VEGF) is altered by hyperglycemia. Transfected (Chinese hamster ovary [CHO] or human embryonic kidney [HEK]) cells overexpressing ACE, ET-1, or VEGF were deposed onto the CAM of hyperglycemic or control embryos. The proangiogenic effect was evaluated 3 d later by angiography and histological analyses. Gene expression in response to these factors was assessed by in situ hybridization. Only VEGF overexpression evoked a proangiogenic response in the CAM from hyperglycemic embryos, upregulating the expression of endogenous VEGF, VEGF-R2, and Tie-2, all of them related to activation of endothelial cells. In conclusion, in a model where hyperglycemia does not alter the major vascular growth factor expression, the negative effect of diabetes on capillary density was overcome only by VEGF overexpression, whereas responses to other vasoactive peptides were practically abolished under hyperglycemic conditions.     

血管内皮细胞生长因子在非血管新生方面的重要功能

血管内皮细胞生长因子(vascular endothelial growth factor,VEGF或VEGF-A),又称为血管通透因子(vascular permeable factor,VPF)是一种具有多种功能的生物大分子,它是分泌性糖蛋白生长因子超家族中的一员.VEGF主要通过两个高亲和力的酪氨酸激酶受体来传递各种信号:VEGF受体1和2(VEGFR1,VEGFR2),从而引起细胞的多种生理反应.在胚胎时期,VEGF可以促进血管内皮细胞的增殖、迁移、管状形成和提高内皮细胞的存活率,对于血管新生和发育十分关键;而在成体时期,VEGF则主要参与正常血管结构的维持,并调节生理和病理性血管新生.近几年来的临床试验表明,使用多种阻断VEGF作用的抑制剂能有效促进肿瘤血管的退化和减小肿瘤的体积,但是同时在部分病人中也观察到了多方面的副作用.这些结果显示,VEGF也具有非血管新生方面的重要功能.因此,在研制基于拮抗VEGF作用的抗癌药物时,这些功能更不容忽视.研究表明,在成体的小肠、胰岛、甲状腺、肾脏和肝脏等器官组织中,VEGF都发挥着十分重要的作用,如果VEGF水平降低,这些器官组织的毛细血管网状结构将部分退化.VEGF还可以促进骨髓形成、组织修复与再生、促进卵巢囊泡成熟,并且参与血栓、炎症反应和缺氧缺血的病理过程.本文主要对VEGF在血管新生之外的功能及其分子机制进行了简要探讨.     

Vascular endothelial growth factor accelerates compensatory lung growth after unilateral pneumonectomy

We hypothesize that compensatory lung growth after unilateral pneumonectomy in a murine model is, in part, angiogenesis dependent and can be altered using angiogenic agents, possibly through regulation of endothelial cell proliferation and apoptosis. Left pneumonectomy was performed in mice. Mice were then treated with proangiogenic factors [vascular endothelial growth factor (VEGF); basic fibroblast growth factor (bFGF)], VEGF receptor antibodies (MF-1, DC101), and VEGF receptor small molecule chemical inhibitors. Lung volume and mass were measured. The lungs were analyzed using immunohistochemistry by CD31 staining, terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling, type II pneumocytes staining, and proliferating cell nuclear antigen. Compensatory lung growth was complete by postoperative day 10 and was associated with diffuse apoptosis of endothelial cells and pneumocytes. This process was accelerated by VEGF, such that growth was complete by postoperative day 4 with similar associated apoptosis. bFGF had no effect on lung growth. MF-1 and DC101 had no effect. The VEGF receptor small molecule chemical inhibitors also had no effect. VEGF, but not bFGF, accelerates growth. VEGF receptor inhibitors do not block growth, suggesting that other proangiogenic factors play a role or can compensate for VEGF receptor blockade. Diffuse apoptosis, endothelial cell and pneumocyte, occurs at cessation of both normal compensatory and VEGF-accelerated growth. Angiogenesis modulators may control growth via regulation of endothelial cell proliferation and apoptosis, although the exact relationship between endothelial cells and pneumocytes has yet to be determined. The fact that bFGF did not accelerate growth in our model when it did accelerate regeneration in the liver model suggests that angiogenesis during organ regeneration is regulated in an organ-specific manner.     

Evidence of the presence of a specific vascular endothelial growth factor in fetal bovine retina

The presence of a vascular endothelial cell growth factor (VEGF) in the retina was reported in a previous study. The present experiments show that VEGF exhibits a pronounced synergism with the serum-derived factor and the vascular endothelium (VE) effectors in stimulating the proliferation of vascular VE cells. VEGF shows a chromatographic multiplicity with the 25,000-D component as the smallest subunit. Mg2+ is the specific divalent cation that retains the VEGF molecule in the aggregated form and enhances the activity, both total and specific. In addition, VEGF is highly specific for endothelial cells and is distinctly different from FGF, EGF, and insulin in terms of molecular weight (MW) and cell specificity. Under our assay conditions, VEGF has no stimulatory effect on other cell lines examined, including lens epithelial cells, corneal epithelial cells, corneal keratocytes, Walker 256 carcinoma, and fibroblasts. These findings indicate that VEGF possesses characteristic properties not reported for other growth factors, and that VEGF is distinctly different from the growth factors isolated from the retina in other laboratories. The present study suggests that VEGF in the retina represents a new type of growth factor. The need to employ a highly defined assay condition could have eluded the detection of this factor in other laboratories.