Suramin inhibits bFGF-induced endothelial cell proliferation and angiogenesis in the chick chorioallantoic membrane.

The effects of suramin, an inhibitor of growth factor mitogenic activity, were evaluated on basic fibroblast growth factor (bFGF)-induced proliferation of bovine aortic endothelial cells and on angiogenesis in the chorioallantoic membrane (CAM) of chick embryos. The role of bFGF gene expression in endothelial cell growth was also investigated by using an antisense oligodeoxynucleotide to bFGF. The 4-fold increase in [3H]-thymidine uptake in endothelial cells in vitro upon stimulation with 10 ng ml-1 of bFGF was inhibited by suramin 300 micrograms ml-1. bFGF antisense oligomer (10 microM) reduced [3H]-thymidine incorporation in exponentially growing cells by 76%; this effect was reversed by bFGF 10 ng ml-1. In the CAM of chick embryos suramin 50 micrograms was a more potent inhibitor of angiogenesis than the combination of heparin 60 micrograms/hydrocortisone 50 micrograms; the mean value of the area with reduced vascularity was significantly larger in suramin-treated CAMs (2.4 cm2) than in heparin/hydrocortisone (0.6 cm2), while the reduction of vascular density was similar (- 35 and - 29% compared to controls, respectively), In conclusion, the effects of treatments with bFGF and bFGF antisense oligomer demonstrate that bFGF plays a relevant role in endothelial cell proliferation and may be the target of suramin since the drug is able to suppress basal and bFGF-induced endothelial cell growth; in addition to this, suramin is a more potent angiogenesis inhibitor in the CAM than the combination of heparin/hydrocortisone.     

Levels of soluble vascular endothelial growth factor (VEGF) receptor 1 in astrocytic tumors and its relation to malignancy, vascularity, and VEGF-A.

PURPOSE: Vascular endothelial growth factor (VEGF)-A isa key mediator of angiogenesis in malignant gliomas. Soluble VEGF receptor 1 (sVEGFR-1) can complex VEGF-A and reduce its bioavailability. In several animal models sVEGFR-1 inhibited angiogenesis and tumor growth. We analyzed the levels of endogenous sVEGFR-1 in gliomas of different malignancy grades in relation to tumor vascularity and VEGF-A. EXPERIMENTAL DESIGN: The concentration of sVEGFR-1 was determined by ELISA in 104 gliomas and normal brain. Levels of sVEGFR-1 were compared with malignancy grade, microvessel density, and VEGF-A concentration. Effects of sVEGFR-1 on glioma extract-induced endothelial cell chemotaxis were analyzed in vitro. RESULTS: The concentration of sVEGFR-1 correlated with the malignancy grade and was 12-fold higher in glioblastomas than in diffuse astrocytomas (P < 0.001), with intermediate levels for anaplastic astrocytomas. VEGF-A levels were 30-fold higher (P < 0.001) in glioblastomas than in diffuse astrocytomas. The sVEGFR-1:VEGF-A ratio was 0.27 in glioblastomas and 0.70 in diffuse astrocytomas. Both sVEGFR-1 and VEGF-A correlated with microvessel density (P < 0.001) and with each other (P < 0.001); sVEGFR-1 and VEGF-A also correlated with each other when only glioblastomas were analyzed (P = 0.001). In vitro, recombinant sVEGFR-1 inhibited endothelial cell chemotaxis induced by tumor extracts. CONCLUSIONS: Although absolute levels of sVEGFR-1 are increased in the more malignant gliomas, the sVEGFR-1:VEGF-A ratio is decreased 2.6-fold in glioblastomas compared with diffuse astrocytomas, suggesting that the ensuing increased bioavailability of VEGF-A favors angiogenesis. The inhibition of tumor extract-induced endothelial chemotaxis by sVEGFR-1 suggests that sVEGFR-1 could be useful as an angiogenesis inhibitor in the specific context of human gliomas.     

Angiogenesis in myelodysplastic syndromes

It is now well established that solid tumour growth depends on angiogenesis. However, less is known about the generation of new vessels in haematological malignancies and, in particular, in preleukaemic-myelodysplastic syndromes (MDS). In this study, bone marrow microvessel density (MVD) was assessed by immunohistochemistry and compared in trephine biopsies from 14 controls, five infectious disease (ID), 82 MDS, 15 acute myeloid leukaemia (AML) and 14 myeloproliferative disorder (MPD) patients. Statistical analysis (P < 0.001) demonstrated that MDS MVD was higher than in controls and ID (21 +/- 9 vs 6 +/- 2 and 10 +/- 8 respectively) but lower than AML (30 +/- 12) and MPD (40 +/- 12). Among MDS-FAB subtypes, MVD was significantly higher in RAEB-t, CMML and fibrosis subsets compared to RA, RARS and RAEB subsets (P= 0.008). To further investigate angiogenesis machinery, the expression of vascular endothelial growth factor (VEGF) was evaluated by means of immunohistochemistry in control, MDS, AML and MPD biopsies. Even though VEGF mRNA expression was reported in the past in AML cell cultures and cell lines, in our samples VEGF expression was found to be particularly strong in most of the megakaryocytes but significantly less prominent in other cell populations including blasts. Since our findings suggest a correlation between angiogenesis and progression to leukaemia, additional work is now warranted to determine what regulates the generation of new vessels in MDS and leukaemia.     

人骨肉瘤鸡胚移植瘤模型的生物学特性研究

目的:建立人骨肉瘤鸡胚移植瘤模型,研究其形态学及生物学特性。方法:将人骨肉瘤细胞接种于鸡胚绒毛尿囊膜(chick embryo chorioallantoic membrane,CAM),观察影响骨肉瘤鸡胚移植瘤成活的因素、移植瘤生长特性、形态学特征和生物学性状。结果:建立了人骨肉瘤鸡胚移植瘤模型。移植瘤易于生长,具有较强的血管诱导作用。光镜下移植瘤具有与人骨肉瘤类似的组织结构。结论:该模型易于复制,能动态观察骨肉瘤诱导的血管生成过程,可用于骨肉瘤的生物学行为研究、药物筛选等领域。     

Expansion of microvascular bed and increased solute flux in human Basal cell carcinoma in vivo,measured by fluorescein video angiography

Human basal cell carcinoma (BCC) offers a unique opportunity to assess directly the microvascular abnormalities in a human cancer in vivo. Our objectives were to assess angiogenesis, perfusion, and changes in small solute exchange kinetics. The microcirculation of BCC and a normal (control) skin site was studied in 15 patients by laser Doppler fluximetry and videoangiography after rapid i.v. fluorescein injection. Microvascular morphometry was analyzed off line. Sodium fluorescein accumulation/clearance was recorded for 30 min, and fluorescence intensity (FI) was quantified by computer analysis of videotape image gray levels. In BCCs, the microvascular area fraction was 2.6-fold greater, microvessel length density 2.0-fold greater, average vessel image width 2.1-fold greater, and red cell flux 3.9-fold greater than in control sites (P < 0.01, paired t tests). The initial rate of rise of FI over 10 s was approximately 3-fold greater in BCC than control and correlated with vascular area fraction and red cell flux. Tissue then equilibrated faster in BCC, rate constant -(13.0 +/- 5.6) x 10(-3) s(-1) (mean +/- SD), than controls -(5.3 +/- 1.7) x 10(-3) s(-1), and plasma clearance was 2.6-fold higher in BCC than controls (P < 0.01, paired t test). Similarly, the rate constant of the subsequent clearance phase was approximately 2-fold greater in BCC, -(0.53 +/- 0.19) x 10(-3) s(-1), than controls, -(0.27 +/- 0.22) x 10(-3) s(-1) (P < 0.01). Removal rate constants were an order of magnitude slower than accumulation rate constants. The results demonstrate angiogenesis, increased perfusion, and a more rapid exchange of small solute in human BCC. FI itself is rejected as an index of permeability to small solutes (cf. 29) because it depends also on blood flow, endothelial area, microvascular volume, and interstitial fluid volume.     

Ethanol stimulates tumor progression and expression of vascular endothelial growth factor in chick embryos

BACKGROUND: The mechanisms by which alcohol consumption causes cancer have not been established due to a lack of experimental studies. METHODS: A chick embryo chorioallantoic membrane (CAM) model that bore human fibrosarcoma (HT1080) was used to determine whether the administration of physiologically relevant doses of ethanol could stimulate tumor growth, angiogenesis, metastasis, and vascular endothelial growth factor (VEGF) expression in tumors. HT1080 cells were inoculated onto the "upper CAM" on Day 8, saline or ethanol was administrated at a dose of 0.25 g/kg per day on the CAM, and the tumors were harvested on Day 17. VEGF mRNA and protein were determined by Northern blot analysis and enzyme-linked immunosorbent assay. Intratumoral vascular volume density (IVVD) was determined by point counting on periodic acid-Schiff-stained sections. Intravasation of HT1080 cells was determined using human-Alu polymerase chain reaction analysis. The effects of ethanol on VEGF expression and cell proliferation were examined in cultured HT1080 cells. RESULTS: Ethanol treatment for 9 days caused a 2.2-fold increase in tumor volume (867 +/- 138 mm(3) vs. 402 +/- 28 mm(3)), a 2.1-fold increase in IVVD (0.021 +/- 0.004 mm(3)/mm(3) vs. 0.010 mm(3)/mm(3) +/- 0.002 mm(3)/mm(3)), and a significant increase in VEGF mRNA or protein expression in tumors compared with a group of control embryos (n = 6 embryos; P < 0.01). Ethanol treatment caused an increase > 8-fold in the intravasated HT1080 cells in the CAM group compared with the control group (n = 6 embryos; P < 0.01). Physiologically relevant levels of ethanol (10 mM and 20 mM) caused a dose-related increase in VEGF mRNA and protein expression in cultured HT1080 cells. The ethanol-HT1080-conditioned media increased the proliferation of endothelial cells, but not of HT1080 cells. CONCLUSIONS: The findings suggest that the induction of angiogenesis and VEGF expression by ethanol represents an important mechanism of cancer progression associated with alcoholic beverage consumption.     

Vascular endothelial growth factor (VEGF) in breast cancer: comparison of plasma, serum, and tissue VEGF and microvessel density and effects of tamoxifen

The assessment of angiogenesis in breast cancer is of importance as a key indicator of survival and response to therapy. Circulating vascular endothelial growth factor (VEGF) measurements may provide a less subjective analysis than microvessel density (MVD) or immunohistochemical analysis of VEGF expression; however, most studies have used serum, which is now known to largely reflect platelet-derived VEGF concentrations. This study examined for the first time both plasma (VEGFp) and serum (VEGFs) VEGF concentrations in 201 blood samples from pre- and postmenopausal healthy controls and from patients with benign breast disease, localized breast cancer, breast cancer in remission, or metastatic breast cancer and related these to other clinicopathological markers. VEGFp but not VEGFs concentrations of patients with localized disease were significantly elevated compared with normal controls (P = 0.016). Patients with metastatic disease had higher VEGFp and VEGFs levels than normal controls (P < 0.001, P = 0.044 respectively), and higher VEGFp, but not VEGFs, than patients with benign disease (P = 0.009) and patients with localized disease (P = 0.004). However, the highest VEGFp and VEGFs concentrations were seen in patients in remission compared with normal controls (P < 0.001 and P = 0.008, respectively). VEGFp concentrations in patients in remission were also higher than in patients with benign disease (P = 0.01) or patients with localized disease (P = 0.005). Tamoxifen treatment was significantly associated with higher circulating and platelet-derived VEGF levels. Circulating VEGF did not correlate with any clinicopathological factor, including MVD or VEGF expression. VEGF expression was significantly correlated with estrogen receptor status and inversely correlated with tumor grade. MVD correlated with tumor size. Tamoxifen-induced increases in VEGF may be important in clinical prognosis or associated pathologies.     

Overexpression of vascular endothelial growth factor (VEGF) and its cellular receptor KDR (VEGFR-2) in the bone marrow of patients with acute myeloid leukemia.

Vascular endothelial growth factor (VEGF) and its cellular receptor VEGFR-2 have been implicated as the main endothelial pathway required for tumor neovascularization. However, the importance of the VEGF/VEGFR-2 system for angiogenesis in hematologic malignancies such as AML remains to be elucidated. In 32 patients with newly diagnosed untreated AML, we observed by immunohistochemical analysis of bone marrow biopsies significantly higher levels of VEGF and VEGFR-2 expression than in 10 control patients (P <0.001). In contrast, VEGFR-1 staining levels in AML patients were in the same range as in the controls. Expression of VEGF and VEGFR-2 was significantly higher in patients with a high degree of microvessel density compared to those with a low degree (VEGF: P =0.024; VEGFR-2: P =0.040) and correlated well with bone marrow microvessel density (r(s)=0.566 and 0.609, respectively; P <0.001). Furthermore, in patients who achieved a complete remission following induction chemotherapy VEGFR-2 staining levels decreased into the normal range. In conclusion, our results provide evidence for increased expression of VEGF/VEGFR-2 of leukemic blasts and correlation with angiogenesis in the bone marrow of AML patients. Thus, VEGF/VEGFR-2 might constitute promising targets for antiangiogenic and antileukemic treatment strategies in AML.     

X-rays modulate extracellular matrix in vivo.

X-rays have an antiangiogenic effect in the chicken embryo chorioallantoic membrane (CAM) model of in vivo angiogenesis. Our study demonstrates that X-rays induce an early apoptosis of CAM cells, modulate the synthesis and deposition of extracellular matrix (ECM) proteins involved in regulating angiogenesis and affect angiogenesis induced by tumour cells implanted onto the CAM. Apoptosis was evident within 1-2 hr, but not later than 6 hr after irradiation. Fibronectin, laminin, collagen type I, integrin alpha(v)beta3 and MMP-2 protein amounts were all decreased 6 hr after irradiation. In contrast, collagen type IV, which is restricted to basement membrane, was not affected by irradiation of the CAM. There was a similar decrease of gene expression for fibronectin, laminin, collagen type I and MMP-2, 6 hr after irradiation. The levels of mRNA for integrin alpha(v)beta3 and collagen type IV were unaffected up to 24 hr after irradiation. The decrease in both protein and mRNA levels was reversed at later time points and 48 hr after irradiation, there was a significant increase in the expression of all the genes studied. When C6 glioma tumour cells were implanted on irradiated CAMs, there was a significant increase in the angiogenesis induced by tumour cells, compared to that in non-irradiated CAMs. Therefore, although X-rays have an initial inhibitory effect on angiogenesis, their action on the ECM enhances new vessel formation induced by glioma cells implanted on the tissue.     

The functional role of cell adhesion molecules in tumor angiogenesis

Cell adhesion molecules (CAMs) are cell surface glycoproteins that mediate the physical interactions between adjacent cells and between cells and the surrounding extracellular matrix. CAMs belong to different protein families, depending on their structural and functional properties. Furthermore, the expression of certain CAMs under physiological conditions is restricted to specific cell types. Besides playing a key homeostatic role in maintaining the architecture of quiescent tissues, CAMs have also to adapt to the microenvironmental changes that occur during certain physiological and pathological processes. This is best exemplified by cancer vascularization, where the expression and function of vascular CAMs are dynamically regulated in response to tissue alterations induced by tumor growth as well as by changes in the surrounding stroma. This enables endothelial cells (ECs) to leave the quiescent state and re-enter the angiogenic cascade. The latter is a multistep process carried out by different types of specialized ECs. This review describes the actual or supposed function of the various CAM subsets in the sequential series of events that underlie vascular changes during tumor angiogenesis. Notably, elucidating the mechanism of action of endothelial CAMs in cancer vasculature is expected to open new therapeutic avenues aimed at interfering with tumor growth and dissemination.     

Inhibition of neuroblastoma-induced angiogenesis by fenretinide.

Retinoids are a class of natural or synthetic compounds that participate in the control of cell proliferation, differentiation and fetal development. The synthetic retinoid fenretinide (HPR) inhibits carcinogenesis in various animal models. Retinoids have also been suggested to be effective inhibitors of angiogenesis. The effects of HPR on certain endothelial cell functions were investigated in vitro, and its effects on angiogenesis was studied in vivo, by using the chorioallantoic membrane (CAM) assay. HPR inhibited vascular endothelial growth factor- (VEGF-) and fibroblast growth factor-2- (FGF-2)-induced endothelial cell proliferation without affecting endothelial motility; moreover, HPR inhibited growth factor-induced angiogenesis in the CAM assay. Furthermore, a significant antiangiogenic potential of HPR has also been observed in neuroblastoma (NB) biopsy-induced angiogenesis in vivo. We previously demonstrated that supernatants derived from NB cell lines stimulated endothelial cell proliferation. In the present study, we found that this effect was abolished when NB cells were incubated in the presence of HPR. VEGF- and FGF-2-specific ELISA assays, performed on both NB cells derived from conditioned medium and cellular extracts, indicated no consistent effect of HPR on the level of these angiogenic cytokines. Moreover, RT-PCR analysis of VEGF and FGF-2 gene expression confirmed the above lack of effect. HPR was also able to significantly repress the spontaneous growth of endothelial cells, requiring at least 48-72 hr of treatment with HPR, followed by a progressive accumulation of cells in G(1) at subsequent time points. Finally, immunohistochemistry experiments performed in the CAM assay demonstrated that endothelial staining of both VEGF receptor 2 and FGF-2 receptor-2 was reduced after implantation of HPR-loaded sponges, as compared to control CAMs. These data suggest that HPR exerts its antiangiogenic activity through both a direct effect on endothelial cell proliferative activity and an inhibitory effect on the responsivity of the endothelial cells to the proliferative stimuli mediated by angiogenic growth factors.     

Treatment of human metastatic transitional cell carcinoma of the bladder in a murine model with the anti-vascular endothelial growth factor receptor monoclonal antibody DC101 and paclitaxel.

Vascular endothelial cell growth factor (VEGF) regulates angiogenesis and metastasis of bladder cancer (transitional cell carcinoma, TCC) through binding to VEGF receptor-2 (VEGFR-2). In this study, we evaluated whether the anti-VEGFR monoclonal antibody (Mab) DC101 in combination with paclitaxel inhibited tumorigenesis, angiogenesis, and metastasis of human TCC growing within the bladder of athymic nude mice. In vivo therapy with Mab DC101 and paclitaxel induced significant regression of bladder tumors compared with either agent alone. Median bladder weights were reduced from 601 mg in untreated controls, 422 mg in mice treated with paclitaxel alone (P < 0.005), 361 mg in mice treated with DC101 alone (P < 0.005), and 113 mg in mice that received combination therapy (P < 0.0005). Only one of nine mice developed spontaneous lymph node metastasis after combined treatment, compared with seven of seven untreated controls (P < 0.0005), six of eight after DC101 (P < 0.01), and five of eight mice after paclitaxel (P < 0.05). Combined treatment with both paclitaxel and DC101 inhibited tumor-induced neovascularity compared with all other groups (P < 0.005), without altering the expression of VEGF or flk1. Mab DC101 and paclitaxel combined enhanced apoptosis in the tumor and endothelial cells compared with other treatment (P < 0.005). These studies indicate that Mab DC101, which blocks VEGFR-2 function, has significant efficacy against human TCC, especially when combined with the chemotherapeutic agent paclitaxel. The antitumor effect was mediated by inhibition of angiogenesis and induction of both tumor cell and endothelial cell apoptosis.     

Complementary medicine use before and 1 year following genetic testing for BRCA1/2 mutations.

PURPOSE: We explored change in complementary and alternative medicine (CAM) use by unaffected women and cancer survivors from enrollment into a randomized BRCA1/2 testing program to CAM use 1 year following results disclosure.METHODS: A cohort of 243 high-risk women completed questionnaires at enrollment into a BRCA1/2 randomized trial and 1 year post results disclosure. Uses of several CAMs for cancer prevention were explored, including ingestible, behavioral, and physical modalities. Assessment of the change in CAM use from baseline to 1 year follow-up was conducted using a repeated self-administered questionnaire. Correlates of the number of CAMs used at 1 year were explored using multivariable linear regression models.RESULTS: Among the subset of women who changed their CAM behavior from enrollment to 1 year following BRCA1/2 results disclosure, there was a significantly higher proportion who changed from no CAM use to CAM use among the overall cohort (P=0.01), among women without cancer at enrollment (P=0.003), among women found to be BRCA1/2 carriers (P=0.03), and among women randomized to the genetic counseling intervention arm of the study (P=0.009). Number of CAMs used at 1 year was positively associated with number of CAMs used at baseline, sunscreen use, and BRCA1/2 mutation status.CONCLUSION: High-risk women who have received BRCA1/2 counseling and testing frequently adopt new CAM use in the first year after learning their genetic status. Mutation carriers frequently initiate CAM use after learning their genetic status as part of their cancer preventive regimen. Further studies are warranted to determine the efficacy of CAM-related strategies for cancer prevention.     

Antiangiogenic and antiproliferative activity of suramin analogues

The purpose of this study was to test the ability of 70 polyanionic analogues of suramin to inhibit angiogenesis. The ID₅₀, the dose that produced 50% inhibition of angiogenesis, was determined for suramin and each of the analogues by measuring the ability of various amounts to inhibit angiogenesis in vivo in the chick egg chorioallantoic membrane (CAM) assay. Of the 70 analogues, 11 had antiangiogenic activities similar to suramin and an additional 7 were significantly more potent than suramin. All seven of these analogues were from the naphthalenetrisulfonic acid group and contained large urea groups. The benzene sulfonic and disulfonic acid analogues were less active inhibitors of angiogenesis than the naphthalenetrisulfonic acid analogues. Replacement of the naphthalenetrisulfonic acid groups by aliphatic carboxylic acids or benzoic acid gave analogues with very little antiangiogenic activity. In subsequent experiments, the antiproliferative activity of selected analogues on basic FGF (bFGF)-stimulated growth of immortalized human microvascular endothelial cells in vitro was determined. Analogues that inhibited angiogenesis to a greater extent than suramin in the CAM assay generally showed a greater antiproliferative effect on bFGF-induced growth of human microvascular endothelial cells. These results suggest that some of the polyanionic analogues may be potent therapeutic agents for cancers and angiogenesis-dependent diseases. Received: 21 October 1996 / Accepted: 8 May 1997     

Epo is involved in angiogenesis in human glioma

In this study, the extent of angiogenesis, evaluated as microvascular density, and the immunoreactivity of tumor cells to erythropoietin (Epo) and of endothelial cells to Epo receptor (EpoR) have been correlated in human glioma specimens, and the effect of anti-Epo antibody on glioma-induced angiogenesis in vivo in the chick embryo chorioallantoic membrane (CAM) has been investigated. Results show that: (1) Epo/EpoR expression correlates with angiogenesis, (2) in the CAM assay, tumor bioptic specimens induce a strong angiogenic response, comparable to that induced by VEGF, and (3) an anti-Epo antibody co-administered with tumor bioptic specimens significantly inhibits the angiogenic response. These findings suggest the presence of a loop in the Epo/EpoR system, i.e. Epo is secreted by glioma tumor cells and it affects glioma vascular endothelial cells via its receptor and promotes angiogenesis in a paracrine manner. Moreover, as demonstrated by in vivo experiments, Epo is responsible for the strong angiogenic response induced by human glioma bioptic specimens, because an anti-Epo antibody is able to significantly inhibit this response.     

Selenium-induced inhibition of angiogenesis in mammary cancer at chemopreventive levels of intake

The trace element nutrient selenium (Se) has been shown to possess cancer-preventive activity in both animal models and humans, but the mechanisms by which this occurs remain to be elucidated. Because angiogenesis is obligatory for the genesis and growth of solid cancers, we investigated, in the study presented here, the hypothesis that Se may exert its cancer-preventive activity, at least in part, by inhibiting cancer-associated angiogenesis. The effects of chemopreventive levels of Se on the intra-tumoral microvessel density and the expression of vascular endothelial growth factor in 1-methyl-1-nitrosourea-induced rat mammary carcinomas and on the proliferation and survival and matrix metalloproteinase activity of human umbilical vein endothelial cells in vitro were examined. Increased Se intake as Se-enriched garlic, sodium selenite, or Se-methylselenocysteine led to a significant reduction of intra-tumoral microvessel density in mammary carcinomas, irrespective of the manner by which Se was provided: continuous exposure (7-wk feeding) with a chemoprevention protocol or acute bolus exposure (3 d) after carcinomas had established. Compared with the untreated controls, significantly lower levels of vascular endothelial growth factor expression were observed in a sizeable proportion of the Se-treated carcinomas. In contrast to the mammary carcinomas, the microvessel density of the uninvolved mammary glands was not altered by Se treatment. In cell culture, direct exposure of human umbilical vein endothelial cells to Se induced cell death predominantly through apoptosis, decreased the gelatinolytic activities of matrix metalloproteinase-2, or both. These results indicate a potential for Se metabolites to inhibit key attributes (proliferation, survival, and matrix degradation) of endothelial cells critical for angiogenic sprouting. Therefore, inhibition of angiogenesis associated with cancer may be a novel mechanism for the anticancer activity of Se in vivo, and multiple mechanisms are probably involved in mediating the anti-angiogenic activity.     

Inhibition by doxycycline of angiogenesis in the chicken chorioallantoic membrane (CAM)

Doxycycline, a tetracycline derivative, has many properties in addition to its antibiotic activity, including inhibition of matrix metalloproteinases (MMPs) and the ability to chelate divalent cations including Ca²⁺. It has been shown to inhibit endothelial cell growth in vitro, and reduce the development of experimental tumours, especially bone metastasis in a model of breast cancer. We examined the effects of doxycycline on angiogenesis in the chicken chorioallantoic membrane (CAM) model, and showed that doxycycline will cause loss of the chorionic plexus in CAMs when applied at day 8 of incubation, and the duration of this inhibition was dose-dependent. Repeated doses prolonged the inhibition, but following removal of the doxycycline there was rapid recovery of the chorionic plexus. The effects of doxycycline are in part mimicked by the MMP inhibitor 1,10-phenanthroline, and more closely by the Ca²⁺-chelating agent EGTA. Doxycycline was equally effective in causing loss of the chorionic plexus by day 11 in CAMs, a time at which the blood vessels are established. Doxycycline has important potential as an antiangiogenic treatment. It is capable of inhibiting angiogenesis in an in vivo model, including the removal of comparatively mature endothelial cells. The response is sensitive to the dosing regimen and the effect is rapidly reversible.     

Antineoplastic effects of chemotherapeutic agents are potentiated by NM-3, an inhibitor of angiogenesis

Antiangiogenic therapy, although effective in shrinking tumors, has not yet been established as a standalone treatment for cancer. This therapeutic limitation can be overcome by combining angiogenesis inhibitors with chemotherapeutic agents. NM-3, a small molecule isocoumarin, is a recently discovered angiogenesis inhibitor. Here we demonstrate that NM-3 inhibits the proliferation of human umbilical vein endothelial cells in vitro, at concentrations 10-fold less than those required to inhibit normal fibroblasts or tumor cells (HT29, MKN28, and MCF-7). NM-3 alone inhibits endothelial sprouting and tube formation in vitro. The results also show that synergistic antiproliferative activity is observed when human umbilical vein endothelial cells are treated with NM-3 in combination with 5-fluorouracil. The effects of treatment with NM-3 and various chemotherapeutic agents were also evaluated in tumor xenografts. The results demonstrate that combined treatment with NM-3 and chemotherapeutic agents significantly reduced mean tumor volume compared with either treatment alone, with no effects on body weight changes. Taken together, these findings demonstrate that NM-3 is a well-tolerated angiogenesis inhibitor that significantly increases the efficacy of existing antineoplastic agents.     

Correlations between cyclooxygenase-2 expression and angiogenic factors in primary tumors and liver metastases in colorectal cancer

BACKGROUND: Angiogenesis is required for growth and metastasis of colorectal cancer (CRC), and several positive regulators of tumor angiogenesis have been identified. Cyclooxygenase-2 (COX-2), known to be elevated in several human cancers, regulates angiogenesis by inducing angiogenic factors. The aim of this study was to clarify the levels and evaluate the relationships of COX-2, vascular endothelial growth factor A and C, thymidine phosphorylase (TP) and microvascular density (MVD) in paired tissue specimens between primary CRC and corresponding metastatic liver cancer. METHODS: Tissue samples from pairs of primary tumors and corresponding metastatic liver tumors from 44 patients with CRC were immunohistochemically evaluated for COX-2, VEGF-A, VEGF-C, TP and MVD. RESULTS: The primary and corresponding metastatic liver tumors tended to show concordant immunoreactivity for COX-2 (P = 0.005, rs = 0.428), VEGF-A (P = 0.039, rs = 0.314), TP (P = 0.005, rs = 0.422) and MVD (P = 0.046, rs = 0.304) by Spearman rank test. The rate of COX-2 immunoreactivity was higher in liver metastases than in primary tumors (P = 0.002), while the rate of VEGF-A was higher in primary tumors than in liver metastases (P = 0.0004). The incidence of TP immunoreactivity and the level of MVD did not differ between primary and metastatic liver tumors (P = 0.247; P = 0.229). Significant correlations were found between COX-2 immunoreactivity and VEGF-A immunoreactivity in metastatic liver tumors (P = 0.033) as well as in primary tumors (P = 0.008). CONCLUSION: The positive correlations between COX-2, VEGF-A, TP and MVD in primary CRC and liver metastasis as demonstrated here will help to predict the angiogenic activity of liver metastasis by analyzing primary tumors, allowing for individualized cancer treatment options.