Anti-angiogenesis therapy and strategies for integrating it with adjuvant therapy

Angiogenesis at the Interface between Basic and Clinical Research

The field of antiangiogenesis has shown a remarkably rapid evolution from the discovery at the bench to translation into the clinic. Currently a wide variety of compounds are in clinical trial as inhibitors of angiogenesis, and new compounds are being frequently added. The target cell of most angiogenesis inhibitors is the endothelial cell, with inhibitors that selectively affect a number of endothelial cell functions acquired during angiogenesis, including activation, proliferation, migration, invasion and survival. The endothelial cell may also be targeted by chemotherapeutic agents currently in use. The high doses and intermittent treatment schedules used to fight resistant tumor cells may be altered towards lower doses and chronic administration to obtain selective inhibition of angiogenic factor-stimulated endothelial cells as adjuvant therapy. Finally, gene therapy is a promising route for the delivery of novel protein inhibitors of angiogenesis, and is actively being investigated.

Deciphering the anti-angiogenic effect of endostatin/cyclophosphamide to normalize tumor micrangium through notch signaling pathway in colon cancer

Background

The invasion of colon cancer is associated with the tumor angiogenesis. Endostatin is an important anti-angiogenic agent, and the additive effect of endostatin with a chemotherapeutic agent, cyclophosphamide, on micrangium has not been established.

Methods

Male BALB/c strain nude mice were injected with human colorectal carcinoma cells (HCT-116). The mice were divided into four groups (n = 15, each group) and were treated with different concentrations of endostatin (15, 10, and 5 mg/kg/day), cyclophosphamide (20, 10, and 5 mg/kg/day), and combination of endostatin/cyclophosphamide (15 + 20, 15 + 10, and 15 + 5 mg/kg/day). The tumor inhibition rate was evaluated, followed by the quantification of messenger ribonucleic acid (mRNA) and protein expression of notch signaling components NOTCH-1, NOTCH-3, NOTCH-4, JAG-1, DLL-4, Hes-1, and Hey-1 using quantitative polymerase chain reaction (qPCR). The protein expression of NOTCH-3, JAG-1, and DLL-4 was confirmed using western blotting. Microvessel density (MVD) was evaluated to detect micrangium following the treatment.

Results

The endostatin/cyclophosphamide-treated samples exhibited an additive effect on the tumor inhibition rate and the microvessel count. NOTCH-1, NOTCH-3, NOTCH-4, JAG-1, Hes-1, and Hey-1 expression levels were highly correlated and downregulated in the treated samples, whereas DLL-4 expression was upregulated that accounted for its anti-angiogenic property.

Conclusions

The combination treatment of colon cancer with endostatin and a chemotherapeutic agent, cyclophosphamide proves to be an efficient therapeutic strategy to inhibit the rapid vasculature formation confirmed by the differential expression of notch signaling components.

TIMP-1 overexpression in lung carcinoma enhances tumor kinetics and angiogenesis in brain metastasis

Tissue inhibitors of matrix metalloproteinase (TIMP) orchestrate many biologic activities, including inhibition of matrix metalloproteinase activity, activation of pro-matrix metalloproteinases, and regulation of cell proliferation, angiogenesis, and apoptosis induction. Tissue inhibitors of matrix metalloproteinase can play a protective role during tumor invasion and metastasis, but elevated TIMP messenger RNA levels have also been associated with aggressive cancers and poor clinical outcome. We examined the potential roles of TIMP-1 in H2009 lung adenocarcinoma cells and in cells transfected with a human TIMP-1-overexpressing vector (HB-6 and HB-1). Tumors resulting from the implantation of parental cell lines and transfected HB-1 cells into the brains of nude mice had a typical carcinoma profile, but human TIMP-1-overexpressing tumors showed enhanced tumor kinetics and focally more infiltrative features; vessel density assessed with anti-CD31 immunohistochemistry was also greater within HB-1 tumor implants. Similar effects on HB-6 and HB-1 cells versus parental cell lines and empty vector clones were observed in endothelial cell assays. Anchorage-independent growth and invasion through Matrigel were also increased in TIMP-1-overexpressing cells. Together, these results indicate tumor-promoting functions of TIMP-1 through alterations in angiogenesis, increased tumorigenicity, and invasive behavior. Although matrix metalloproteinase inhibition has been the traditionally identified function of TIMP-1, matrix metalloproteinase-independent interactions may contribute to the growth of metastatic carcinomas in the brain.

Anti-tumor effect of a novel soluble recombinant human endostatin: administered as a single agent or in combination with chemotherapy agents in mouse tumor models

Background

Angiogenesis has become an attractive target in cancer treatment. Endostatin is one of the potent anti-angiogenesis agents. Its recombinant form expressed in the yeast system is currently under clinical trials. Endostatin suppresses tumor formation through the inhibition of blood vessel growth. It is anticipated that combined therapy using endostatin and cytotoxic compounds may exert an additive effect. In the present study, we expressed and purified recombinant human endostatin (rhEndostatin) that contained 3 additional amino acid residues (arginine, glycine, and serine) at the amino-terminus and 6 histidine residues in its carboxyl terminus. The recombinant protein was expressed in E. Coli and refolded into a soluble form in a large scale purification process. The protein exhibited a potent anti-tumor activity in bioassays. Furthermore, rhEndostatin showed an additive effect with chemotherapy agents including cyclophosphamide (CTX) and cisplatin (DDP).

Methods

rhEndostatin cDNA was cloned into PQE vector and expressed in E. Coli. The protein was refolded through dialysis with an optimized protocol. To establish tumor models, nude mice were subcutaneously injected with human cancer cells (lung carcinoma A549, hepatocellular carcinoma QGY-7703, or breast cancer Bcap37). rhEndostatin and/or DDP was administered peritumorally to evaluate the rate of growth inhibition of A549 tumors. For the tumor metastasis model, mice were injected intravenously with mouse melanoma B16 cells. One day after tumor cell injection, a single dose of rhEndostatin, or in combination with CTX, was administered intravenously or at a site close to the tumor.

Results

rhEndostatin reduced the growth of A549, QGY-7703, and Bcap37 xenograft tumors in a dose dependent manner. When it was administered peritumorally, rhEndostatin exhibited a more potent inhibitory activity. Furthermore, rhEndostatin displayed an additive effect with CTX or DDP on the inhibition of metastasis of B16 tumors or growth of A549 tumors.

Conclusion

Soluble rhEndostatin exhibits a potent anti-tumor activity in mouse xenograft models and it also has an additive effect with CTX and DDP, implying possible applications in clinical settings.

Inhibitory effect of Bifidobacterium infantis-mediated sKDR prokaryotic expression system on angiogenesis and growth of Lewis lung cancer in mice

BACKGROUND

To construct the Bifidobacterium infantis-mediated soluble kinase insert domain receptor (sKDR) prokaryotic expression system and to observe its inhibitory effect on growth of human umbilicus vessel endothelial cells (HUVECs) in vitro and Lewis lung cancer (LLC) on mice in vivo.

METHODS

The Bifidobacterium infantis-mediated sKDR prokaryotic expression system was constructed through electroporation and subsequently identified through PCR and Western blot analysis. HUVECs were added to the products of this system to evaluate the anti-angiogenesis effect through MTT assay in vitro. The LLC mice models were divided into three groups: one group treated with saline (group a); one group treated with recombinant Bifidobacterium infantis containing pTRKH2-PsT plasmid group (group b); and one group treated with recombinant Bifidobacterium infantis containing pTRKH2-PsT/sKDR plasmid group (group c). The quality of life and survival of mice were recorded. Tumor volume, tumor weight, inhibitive rate, and necrosis rate of tumor were also evaluated. Necrosis of tumor and signals of blood flow in tumors were detected through color Doppler ultrasound. In addition, microvessel density (MVD) of the tumor tissues was assessed through CD31 immunohistochemical analysis.

RESULTS

The positively transformed Bifidobacterium infantis with recombinant pTRKH2-PsT/sKDR plasmid was established, and was able to express sKDR at gene and protein levels. The proliferation of HUVECs cultivated with the extract of positively transformed bacteria was inhibited significantly compared with other groups (P < 0. 05). The quality of life of mice in group c was better than in group a and b. The recombinant Bifidobacterium infantis containing pTRKH2-PsT/sKDR plasmid enhanced the efficacy of tumor growth suppression and prolongation of survival, increased the necrosis rate of tumor significantly, and could obviously decrease MVD and the signals of blood flow in tumors.

CONCLUSION

The Bifidobacterium infantis-mediated sKDR prokaryotic expression system was constructed successfully. This system could express sKDR at gene and protein levels and significantly inhibit the growth of HUVECs induced by VEGF in vitro. Moreover, it could inhibit tumor growth and safely prolong the survival time of LLC C57BL/6 mice.

Antiangiogenic gene therapy of experimental pancreatic tumor by sFlt-1 plasmid DNA carried by RGD-modified crosslinked polyplex micelles

Disulfide crosslinked polyplex micelles with RGD peptides were formed through ion complexation of thiolated c(RGDfK)-poly(ethylene glycol)-block-poly(L-lysine) (c(RGDfK)-PEG-P(Lys-SH)) and plasmid DNA encoding sFlt-1 and tested for their therapeutic effect in BxPC3 pancreatic adenocarcinoma tumor bearing mice. These micelles, systemically injected, demonstrated significant inhibition of tumor growth up to day 18, as a result of the antiangiogenic effect that was confirmed by vascular density measurements. Significant therapeutic activity of the 15% crosslinked micelle (c(RGDfK)-PEG-P(Lys-SH15)) was achieved by combined effect of increased tumor accumulation, interaction with endothelial cells and enhanced intracellular uptake through receptor-mediated endocytosis. These results suggest that RGD targeted crosslinked polyplex micelles can be effective plasmid DNA carriers for antiangiogenic gene therapy.

Vascular endothelial growth factor immunoneutralization in combination with cisplatin reduces EAC tumor growth

In the present study, we evaluated the effects of a neutralizing anti-Vascular Endothelial Growth Factor (VEGF) polyclonal antibody on murine EAC tumor growth both in vitro and in vivo. Furthermore, we investigated if in the presence of effective VEGF blockade, a conventional chemotherapeutic drug Cisplatin could be effective, and if so would there be an additive effect of the combination regimen. An in vitro cell proliferation assay using MTT kit showed that VEGF antibody alone inhibited proliferation of EAC cells significantly in all the three time intervals (p<0.05). But cisplatin treatment in combination with VEGF antibody resulted in highly significant inhibition (p<0.001) of cell proliferation. Apoptosis assay by FACS analysis showed that VEGF antibody-cisplatin combination treatment induced apoptosis in cultured EAC cells. Intraperitoneal administration of VEGF antibody (100 mug/dose) and cisplatin (0.5 mg/kg/dose) combination was observed to be more effective in reducing tumor burden and increasing life span when compared to VEGF antibody or cisplatin treatment alone in EAC solid tumor bearing mice. In EAC ascites tumor model, all the three types of treatment inhibited tumor burden and increased life span, but the inhibition was less compared to EAC solid tumor bearing mice. VEGF antibody singly and in combination with cisplatin reduced neoangiogenesis and vascular hyperpermeability. However, it is clear from the results that the combination treatment had no additive effect in reducing vascular hyperpermeability. Serum VEGF was not reduced significantly after treatment in EAC ascites tumor bearing mice, whereas in EAC solid tumor bearing mice it was reduced significantly after treatment. The results clearly show that though alone cisplatin showed antitumor efficacy but it had no significant inhibitory effect on neoangiogenesis and vascular hyperpermeability. Thus the present study suggests that anti-VEGF agent can be combined with traditional treatment modalities to ensure more effectiveness.

Combination of MIG (CXCL9) chemokine gene therapy with low-dose cisplatin improves therapeutic efficacy against murine carcinoma

MIG (monokine induced by interferon-gamma) is a CXC chemokine ligand (CXCL9) that can potently inhibit angiogenesis, and displays thymus-dependent antitumor effects. The effectiveness of a treatment combining gene therapy with plasmid-borne MIG (pORF-MIG) and low-dose cisplatin chemotherapy was determined using colon carcinoma (CT26) and Lewis lung carcinoma (LL/2c) murine models. The program was carried out via intramuscular delivery of pORF-MIG at 100 mug/mouse twice a week for 4 weeks, and/or intraperitoneal delivery of cisplatin at 0.6 mg/kg/mouse every 3 days for 48 days. Tumor volume and survival time were evaluated after treatment. CD31 immunohistochemical staining in tumor tissues and alginate capsule models in vivo was used to evaluate angiogenesis. Induction of apoptosis and cytotoxic T-lymphocyte (CTL) activity were also assessed. The combination of pORF-MIG and low-dose cisplatin produced significant antitumor activity, with complete tumor regression in 4/10 of CT26 colon carcinomas and 3/10 of LL/2c lung carcinomas, low vascularity, in alginate capsules, apparently degraded tumor microvessel density, and increased induction of apoptotic and CTL activities compared with either treatment alone. This study suggests that the combination of pORF-MIG plus cisplatin augments the inhibition of angiogenesis and the induction of apoptosis or CTL activity, all of which enhance antitumor activity. These findings may prove useful in further explorations of the application of combinatorial approaches to the treatment of solid tumors.

Validation of laser Doppler fluxmetry as a method of assessing neo-angiogenesis in laryngeal tumours

Our intention was to validate the hypothesis that laser Doppler fluxmetry would give a valid representation of underlying tissue blood flow and would provide a reliable tool for measuring blood flow in human laryngeal cancers. This was an experimental prospective study. We performed laser Doppler fluxmetry on 20 patients with laryngeal cancer and compared the values obtained through this method with manual counting of microvessel density from biopsies, the accepted gold standard. We demonstrated good inter- and intraobserver variability in our estimation of microvessel density. We then compared microvessel density with laser Doppler fluxmetry, and using Spearman's test to assess nonparametric correlation, we obtained a correlation coefficient of 0.4 (P value: 0.15). To our knowledge, this study is the first of its kind to demonstrate a positive trend between angiogenesis measured conventionally when compared with laser Doppler fluxmetry.

Hypericin in the dark inhibits key steps of angiogenesis in vitro

Photoactivated hypericin has a potent cytotoxic effect over a wide range of cells. However, very recently hypericin has been shown to have antitumoral and antimetastatic effects in the dark. The aim of this study was to test whether hypericin in the dark affects angiogenesis. Different in vitro assays were used to study the potential effects of this compound on key steps of angiogenesis, namely, a colorimetric assay of cell proliferation/viability, a tubular formation on Matrigel assay, zymographic assays for gelatinases and urokinase, a wound assay for migration and a fluorometric assay for invasion through Matrigel. In this report, we show for the first time that hypericin kept in the dark inhibits several key steps of the angiogenic process, namely, bovine endothelial cell proliferation, formation of tubular-like structures on Matrigel, migration and invasion, as well as extracellular matrix degrading urokinase.

Sensitization of tumor-associated endothelial cell apoptosis by the novel vascular-targeting agent ZD6126 in combination with cisplatin

PURPOSE

ZD6126 is a novel vascular-targeting agent that selectively disrupts the tubulin cytoskeleton of endothelial cells. In the immature vessels characteristic of tumor vasculature, this leads to endothelial cell contraction, blood vessel congestion, and, consequently, tumor cell death. ZD6126 has been shown to delay tumor growth in a range of xenograft models. The antitumor effect of ZD6126 can be increased in combination with cisplatin or radiation therapy, although the precise mechanism of this enhancement has not been demonstrated. ZD6126 treatment has also been shown to inhibit lung metastasis, and the present study has explored the potential to increase the antimetastatic effect of ZD6126 by combining with cisplatin, and the underlining mechanism has been investigated.

EXPERIMENTAL DESIGN

Human lung adenocarcinoma PC14PE6 cells were injected into the tail vein of nude mice. Five weeks after injection animals were treated with ZD6126 (200 mg/kg i.p.), cisplatin (6 mg/kg i.v.), or a combination of the two agents. The animals were sacrificed 24 hours later, and the extent of lung metastases and the presence of apoptotic cells were assessed.

RESULTS

Histologic analysis revealed that the ZD6126/cisplatin combination resulted in a 2 to 4-fold increase in the total number of tumor-associated apoptotic cells compared with either treatment alone. ZD6126 alone induced apoptosis of tumor-associated endothelial cells in tumors, and the extent of apoptosis was increased 2-fold in combination with cisplatin. The lung weight was significantly reduced, and the number of metastatic nodules significantly was lower in the combined treatment group than in the control group.

CONCLUSIONS

These data suggest that the antimetastatic effect of the vascular-targeting agent ZD6126 can be increased by use in combination with cisplatin, which increases the incidence of endothelial cell apoptosis.

Antiangiogenic, antimicrobial, and cytotoxic potential of sponge-associated bacteria

The bacteria associated with marine invertebrates are a rich source of bioactive metabolites. In the present study bacteria associated with the sponge Suberites domuncula and its primmorphs (3-dimensional aggregates containing proliferating cells) were isolated and cultured. These bacteria were extracted, and the extracts were assayed for antiangiogenic, hemolytic, antimicrobial, and cytotoxic activities. Our studies revealed that extract obtained from the bacterium (PB2) isolated from sponge primmorphs is a potent angiogenesis inhibitor. In the chick chorio-allantoic membrane (CAM) assay, it showed 50% activity at 5 microg ml(-1) and 100% activity at 10 and 20 microg ml(-1) concentrations. Extracts obtained from 5 bacterial strains isolated from sponge and its primmorphs showed hemolytic activity. The sponge-associated bacteria belonging to the alpha subdivision of Proteobacteria and the primmorph-associated bacterium identified as a possible novel Pseudomonas sp. displayed remarkable antimicrobial activity. It is important to note that these bacterial extracts were strongly active against multidrug-resistant clinical strains such as Staphylococcus aureus and Staphylococcus epidermidis, isolated from hospital patients. The bacterial extracts having antimicrobial activity also showed cytotoxicity against HeLa and PC12 cells. In summary, this investigation explores the importance of sponge-associated bacteria as a valuable resource for the discovery of novel bioactive molecules.

Tanshinone IIA isolated from Salvia miltiorrhiza elicits the cell death of human endothelial cells

Tanshinone IIA, a major component extracted from the traditional herbal medicine, Salvia miltiorrhiza Bunge, is known to exhibit potent cytotoxicity against various human carcinoma cells in vitro. However, the mechanism by which tanshinone IIA produces this anti-tumor effect remains unknown. Since anti-neovascularization has generally been regarded as an effective strategy for anti-cancer therapy, we decided to investigate the mechanism underlying tanshinone IIA-mediated death of human endothelial cells. In this study, we demonstrate that tanshinone IIA elicits human endothelial cell death independent of oxidative stress. These events are partially calcium-dependent and actually dependent upon NAD(P)H: quinone oxidoreductase (NQO1) activity. Tanshinone IIA induces an increase in intracellular calcium, which triggers the release of cytochrome c, thus causing loss of the mitochondrial membrane potential (MMP), resulting in the subsequent activation of caspases. Blocking the induction of Ca2+ perturbation with BAPTA-AM partially rescued cells from tanshinone IIA-induced cytotoxicity. Additionally, blocking NQO1 activity with dicoumoral or inhibiting caspase activities with the general caspase inhibitor, z-VAD-fmk, prevented cell death induced by tanshinone IIA. Therefore, our results imply that tanshinone IIA-mediated cytotoxicity against human endothelial cells may occur through activation of NQO1, which induces a calcium imbalance and mitochondrial dysfunction, thus stimulating caspase activity.

Hyperforin, a bio-active compound of St. John's Wort, is a new inhibitor of angiogenesis targeting several key steps of the process

Hyperforin, a phloroglucinol derivative found in St. John's wort related mainly to its antidepressant effects, has been reported recently to induce apoptosis in tumour cells and to inhibit cancer invasion and metastasis. We show that hyperforin inhibits angiogenesis in vitro in bovine aortic endothelial cells and in vivo in the chorioallantoic membrane assay. In a variety of experimental systems representing the sequential events of the angiogenic process, hyperforin treatment of endothelial cells resulted in strong inhibitory effects. Hyperforin inhibited the growth of endothelial cells in culture. Capillary tube formation on Matrigel was abrogated completely by addition of hypeforin at the low micromolar range. Hyperforin also exhibited a clear inhibitory effect on the invasive capabilities of endothelial cells. Zymographic assays showed that hyperforin treatment produced a complete inhibition of urokinase and a remarkable inhibition of matrix metalloproteinase 2. Our data indicates that hyperforin is a compound that interferes with key events in angiogenesis, confirming the recent and growing evidence about a potential role of this compound in cancer and metastasis inhibition and making it a promising drug for further evaluation in the treatment of angiogenesis-related pathologies.

Effects of ursolic acid on different steps of the angiogenic process

Ursolic acid is a triterpenoid with pleiotropic biological effects. In this report, we study the effects of ursolic acid on different key steps of angiogenesis. Our results show that ursolic acid is able to inhibit key steps of angiogenesis in vitro, including endothelial cell proliferation, migration, and differentiation. At the same time, it seems to stimulate other key steps of angiogenesis, such as extracellular matrix degradation by MMP-2 and urokinase. Although ursolic acid can inhibit in vivo angiogenesis in the CAM assay, the different signs of the effects it causes on different steps of angiogenesis force one to be cautious concerning its anti-angiogenic potential.

Hypoxia-inducible factors 1alpha and 2alpha are related to vascular endothelial growth factor expression and a poorer prognosis in nodular malignant melanomas of the skin

Hypoxia is a key regulatory factor in tumour growth, activating angiogenesis, glycolysis and cell migration. It is readily recognized by the intracellular accumulation of hypoxia-inducible factor 1alpha (HIF1alpha) and HIF2alpha. Accumulation of HIF1alpha and HIF2alpha was detected immunohistochemically in a series of 46 nodular malignant melanomas of the skin (epithelioid cell variant), treated with wide local excision. The results were correlated with vascular density (VD) and expression of the angiogenesis-stimulating factors vascular endothelial growth factor (VEGF) and thymidine phosphorylase (TP). Further associations were sought with patient prognosis and the important histopathological features of Breslow's thickness, Clark's level of invasion, mitotic rate, inflammatory cell infiltrates and tumour ulceration. HIF1alpha and HIF2alpha accumulation in malignant melanomas was directly correlated with VEGF expression. Tumours with high VEGF or HIF2alpha expression were associated with a poorer prognosis on both univariate and multivariate analyses. Tumours displaying high VD were also associated with a poor prognosis, but only on univariate analysis. Such vascularized malignant melanomas had only a limited inflammatory cell response. TP and VEGF were frequently co-expressed. The value of Breslow's thickness and Clark's level in prognosis was reaffirmed, although only on univariate analysis. Overexpression of the transcription factors HIF1alpha and HIF2alpha are linked to VEGF expression in nodular malignant melanomas. Loss of immune surveillance, as indicated by a limited inflammatory cell response, was also associated with high angiogenic activity. HIF2alpha, VEGF and, to a lesser extent, VD are important prognostic factors in these cutaneous tumours.

Study of puupehenone and related compounds as inhibitors of angiogenesis

Puupehenone, a sesquiterpene produced by certain sponges, was selected in the course of a blind screening for new potential inhibitors of angiogenesis. In our study, we compare the potential anti-angiogenic activities of puupehenone and another 11 related compounds that were either natural products from marine origin or their synthetic derivatives. The effects of these compounds were determined with cell growth and differentiation assays on bovine aorta endothelial cells. Our results show that these compounds are weak inhibitors to cell growth and are not selective for endothelial cells. However, contrary to cell growth, the differentiation of endothelial cells into tubular structures was completely inhibited by 7 of these compounds at concentrations equal or lower than 3 microM. Three of these compounds, isozonarol, 8-epipuupehedione and 8 epi-9,11-dihydropuupehedione, completely inhibited the in vivo angiogenesis in the CAM assay at doses equal or lower than 30 nmol/egg. Further characterisation showed that these 3 terpenes also inhibited endothelial cell production of urokinase and invasion. One compound (8-epipuupehedione) inhibited endothelial cell migration in a dose-dependent manner. The anti-angiogenic properties of the selected compounds, the simplicity of their structures and the feasibility of their synthesis make them attractive drugs for further evaluation in the treatment of angiogenesis-related pathologies.

Biotherapeutic approaches to pancreatic cancer

The incidence of adenocarcinoma of the pancreas has risen steadily over the past four decades. Since pancreatic cancer is usually diagnosed at an advanced stage and because of the lack of effective therapies, the prognosis of such patients is extremely poor. Despite advances in our understanding of the molecular biology of pancreatic cancer, the systemic treatment of this disease remains unsatisfactory. Conventional chemotherapy has not produced dramatic improvements in response rates or patient survival. New treatment strategies are clearly needed. This paper will review emerging therapies for pancreatic carcinoma. A deeper understanding of the molecular biology of cell growth and proliferation, as well as of neoplastic cell transformation, has led to advances in several areas, including the use of hormones and antihormones as adjuvant therapy; inhibition of tumour growth and metastasis by inhibitors of matrix metalloproteases and angiogenesis, and by small molecules, such as retinoids, which interfere with progression through the cell cycle; immunotherapy with monoclonal antibodies; disruption of intracellular signal transduction with farnesyltransferase inhibitors; and, finally, gene therapy with specifically designed vaccines.

A critical review of vascular endothelial growth factor (VEGF) analysis in peripheral blood: is the current literature meaningful?

Vascular endothelial growth factor (VEGF) is a potent angiogenic growth factor with a key role in many physiological and pathological processes. Investigation into the implications of circulating levels of this cytokine is progressing at an exponential rate. However, there are important inconsistencies between reports ranging from method of sample collection, processing, software manipulation and data interpretation and controversy as to whether plasma, serum or whole blood will provide the best prognostic information. Different techniques of centrifugation and temperature on sample handling and the impact of in vitro collection of blood on subsequent VEGF results have not been fully appreciated. We provide a critical review of the literature, report the results of our further investigations, suggest a uniform protocol for handling blood samples and highlight previously unsuspected problems in data interpretation.

Phase I pharmacokinetic and pharmacodynamic study of recombinant human endostatin in patients with advanced solid tumors

PURPOSE

Endostatin is the first endogenous angiogenesis inhibitor to enter clinical trials. Laboratory investigations with endostatin have indicated broad antitumor activity coupled with remarkably low toxicity. A phase I trial of recombinant human endostatin was designed to evaluate toxicity and explore biologic effectiveness in patients with refractory solid tumors.

PATIENTS AND METHODS

Endostatin was administered as a 1-hour intravenous infusion given daily for a 28-day cycle. A starting dose of 30 mg/m2 was explored with subsequent dose escalations of 60, 100, 150, 225, and 300 mg/m2. Assessment of serum pharmacokinetics was performed on all 21 patients. Western blot assay and mass spectroscopy were employed to evaluate endostatin metabolism. Circulating levels of endogenous proangiogenic growth factors were examined. Tumor and tumor blood supply were imaged by dynamic computed tomography (CT), magnetic resonance imaging, ultrasound, and positron emission tomography.

RESULTS

Endostatin given on this schedule was essentially free of significant drug-related toxicity. Two transient episodes of grade 1 rash were observed. No clinical responses were observed. Endostatin pharmacokinetics were linear with dose, and serum concentrations were achieved that are associated with antitumor activity in preclinical models. No aggregate effect on circulating proangiogenic growth factors were seen, although several patients exhibited persistent declines in vascular endothelial growth factor levels while enrolled in the study. A few patients demonstrated changes in their dynamic CT scans suggestive of a decline in microvessel density, although overall, no consistent effect of endostatin on tumor vasculature was seen.

CONCLUSION

Endostatin given daily as a 1-hour intravenous infusion was well tolerated without dose-limiting toxicity at doses up to 300 mg/m2.

Antiangiogenic activity of aeroplysinin-1, a brominated compound isolated from a marine sponge

(+)-aeroplysinin-1, an antibacterial brominated compound produced by certain sponges, was selected during a blind high-throughput screening for new potential antiangiogenic compounds obtained from marine organisms. In a variety of experimental systems, representing the sequential events of the angiogenic process, aeroplysinin-1 treatment of endothelial cells resulted in strong inhibitory effects. Aeroplysinin-1 inhibited the growth of endothelial cells in culture and induced endothelial cell apoptosis. Capillary tube formation on Matrigel was completely abrogated by addition of aeroplysinin-1 at the low micromolar range. Aeroplysinin-1 also exhibited a clear inhibitory effect on the migration capabilities of endothelial cells. Zymographic assays showed that aeroplysinin-1 treatment produced a decrease in the concentration of matrix metalloproteinase-2 and urokinase in conditioned medium from endothelial cells. Finally, aeroplysinin-1 exhibited a dose-dependent inhibitory effect on the in vivo chorioallantoic membrane assay, showing potent apoptosis-inducing activity in the developing endothelium. The in vivo inhibition of angiogenesis by aeroplysinin-1 was confirmed by the Matrigel plug assay. Together, our data indicate that aeroplysinin-1 is a compound that interferes with key events in angiogenesis, making it a promising drug for further evaluation in the treatment of angiogenesis-related pathologies.

Intratumoral gene therapy of malignant brain tumor in a rat model with angiostatin delivered by adeno-associated viral (AAV) vector

We have utilized a recombinant adeno-associated viral (AAV) vector carrying the angiostatin gene as an anti-angiogenesis strategy to treat the malignant brain tumor in a C6 glioma/Wistar rat model. Angiostatin, as a potent angiogenesis inhibitor, shows high promises as an anti-cancer drug through the inhibition of tumor neovessel formation. However, sustained in vivo protein delivery is required to achieve the therapeutic effects. The AAV vector has been proven to be able to deliver sustained and high-level gene expression in vivo, and therefore, is well suited to such a purpose. In this study, we implanted 5 x 10(5) C6 glioma cells into the rat brain 7 days before gene therapy. Intratumoral injection of a high-titer AAV-angiostatin vector has rendered efficacious tumor suppression and resulted in long-term survival in 40% of the treated rats, whereas the control AAV-GFP vector did not have any therapeutic benefits. In addition, we have investigated the combined gene therapy of an adenoviral vector carrying the suicidal thymidine kinase gene along with the AAV-angiostatin vector. The combined therapy offered the best tumor-suppressive effects and increased long-term survival to 55% in the treated rats. Our study has demonstrated the potential of using AAV as a safe and effective vector for anti-angiogenic gene therapy of brain tumors.

There may never be a final cure for breast cancer

This paper challenges the perception that the success of the human genome project has brought us to the threshold of a cure for many common cancers. Paradoxically, the message emerging from the genetics of breast cancer may be that the genetic damage associated with malignant transformation, and the mutations predisposing to the disease in our gene pool, may prove impossible to eliminate.

Pancreatic cancer: a review of emerging therapies

The incidence of adenocarcinoma of the pancreas has risen steadily over the past 4 decades. Since pancreatic cancer is diagnosed at an advanced stage, and because of the lack of effective therapies, the prognosis of such patients is extremely poor. Despite advances in our understanding of the molecular biology of pancreatic cancer, the systemic treatment of this disease remains unsatisfactory. Conventional chemotherapy has not produced dramatic improvements in response rates or patient survival. New treatment strategies are clearly needed. This paper reviews emerging therapies for pancreatic carcinoma. A more profound understanding of the molecular biology of cell growth and proliferation, as well as of neoplastic cell transformation, has led to advances in several areas, including the use of somatostatin analogues and antiandrogens as adjuvant therapy; inhibition of tumour growth and metastasis by inhibitors of matrix metalloproteinases and angiogenesis, and by small molecules such as retinoids, which interfere with progression through the cell cycle; immunotherapy with monoclonal antibodies; disruption of intracellular signal transduction with farnesyltransferase inhibitors; and finally gene therapy with specifically designed vaccines.

Imaging of tumour neovasculature by targeting the TGF-beta binding receptor endoglin

In vivo imaging of endothelial markers in intact tumour neovasculature would have applications in assessing the efficacy of anti-angiogenic agents in clinical trials. Although a variety of different endothelial markers have been described, few have been evaluated as imaging markers. The transforming growth factor-beta (TGF-beta) binding receptor endoglin is a proliferation-associated endothelial marker. We hypothesised that endoglin would be an ideal target for imaging since it is strongly upregulated in proliferating endothelial cells of the tumour neovasculature. We used a radiolabelled monoclonal anti-endoglin antibody and compared its neovascular binding, accumulation and in vivo behaviour to an isotype-matched control IgG(2a). Our data show that the probe binds specifically and rapidly within minutes in vivo and that correlative autoradiography and immunohistology support the in vivo imaging findings. Imaging of abundantly expressed endothelial targets circumvents delivery barriers normally associated with other tumour targeting strategies, and can potentially be used to quantitate molecular angiogenic markers.

Thrombospondin-2: a potent endogenous inhibitor of tumor growth and angiogenesis

Recent evidence suggests a potential role for thrombospondin-2 (TSP-2), a matricellular glycoprotein, in the regulation of primary angiogenesis. To directly examine the biological effect of TSP-2 expression on tumor growth and angiogenesis, human A431 squamous cell carcinoma cells, which do not express TSP-2, were stably transfected with a murine TSP-2 expression vector or with vector alone. A431 cells expressing TSP-2 did not show an altered growth rate, colony-forming ability, or susceptibility to induction of apoptosis in vitro. However, injection of TSP-2-transfected clones into the dermis of nude mice resulted in pronounced inhibition of tumor growth that was significantly stronger than the inhibition observed in A431 clones stably transfected with a thrombospondin-1 (TSP-1) expression vector, and combined overexpression of TSP-1 and TSP-2 completely prevented tumor formation. Extensive areas of necrosis were observed in TSP-2-expressing tumors, and both the density and the size of tumor vessels were significantly reduced, although tumor cell expression of the major tumor angiogenesis factor, vascular endothelial growth factor, was maintained at high levels. These findings establish TSP-2 as a potent endogenous inhibitor of tumor growth and angiogenesis.

New vessels, new approaches: angiogenesis as a therapeutic target in musculoskeletal disorders

Musculoskeletal disorders such as rheumatoid arthritis (RA) and osteoarthritis are a common cause of pain and disability. The vasculature is an important component of the musculoskeletal system, and vascularization is a key event in the development of normal cartilage and bone. By promoting the delivery of nutrients, oxygen and cells, blood vessels help maintain the structural and functional integrity of joints and soft tissue and may facilitate tissue repair and healing. The identification of pro-angiogenic mediators such as vascular endothelial growth factor (VEGF) has led to the development of antiangiogenic therapies for the treatment of neoplastic diseases. The important role of angiogenesis, and especially VEGF, in the pathogenesis of joint disorders such as RA suggests that antiangiogenic therapy may be a useful adjunct to existing approaches in RA.