Angiostatin gene transfer: inhibition of tumor growth in vivo by blockage of endothelial cell proliferation associated with a mitosis arrest

Genetic Delivery and Gene Therapy in Pulmonary Hypertension

Pulmonary hypertension (PH) is a progressive complex fatal disease of multiple etiologies. Hyperproliferation and resistance to apoptosis of vascular cells of intimal, medial, and adventitial layers of pulmonary vessels trigger excessive pulmonary vascular remodeling and vasoconstriction in the course of pulmonary arterial hypertension (PAH), a subgroup of PH. Multiple gene mutation/s or dysregulated gene expression contribute to the pathogenesis of PAH by endorsing the proliferation and promoting the resistance to apoptosis of pulmonary vascular cells. Given the vital role of these cells in PAH progression, the development of safe and efficient-gene therapeutic approaches that lead to restoration or down-regulation of gene expression, generally involved in the etiology of the disease is the need of the hour. Currently, none of the FDA-approved drugs provides a cure against PH, hence innovative tools may offer a novel treatment paradigm for this progressive and lethal disorder by silencing pathological genes, expressing therapeutic proteins, or through gene-editing applications. Here, we review the effectiveness and limitations of the presently available gene therapy approaches for PH. We provide a brief survey of commonly existing and currently applicable gene transfer methods for pulmonary vascular cells in vitro and describe some more recent developments for gene delivery existing in the field of PH in vivo.

The Role of Fibrinolytic Regulators in Vascular Dysfunction of Systemic Sclerosis

Systemic sclerosis (SSc) is a connective tissue disease of autoimmune origin characterized by vascular dysfunction and extensive fibrosis of the skin and visceral organs. Vascular dysfunction is caused by endothelial cell (EC) apoptosis, defective angiogenesis, defective vasculogenesis, endothelial-to-mesenchymal transition (EndoMT), and coagulation abnormalities, and exacerbates the disease. Fibrinolytic regulators, such as plasminogen (Plg), plasmin, α2-antiplasmin (α2AP), tissue-type plasminogen activator (tPA), urokinase-type plasminogen activator (uPA) and its receptor (uPAR), plasminogen activator inhibitor 1 (PAI-1), and angiostatin, are considered to play an important role in the maintenance of endothelial homeostasis, and are associated with the endothelial dysfunction of SSc. This review considers the roles of fibrinolytic factors in vascular dysfunction of SSc.

Generation of Expression Plasmids for Angiostatin, Endostatin and Timp-2 for Cancer Gene Therapy

Antiangiogenic therapy may represent a promising approach to cancer treatment. Indeed, the efficacy of endogenous angiogenesis inhibitors, including angiostatin, endostatin and TIMPs, has been demonstrated in many types of solid tumors in animal models. In view of the possible problems associated with long-term administration of inhibitors as recombinant proteins, we propose their delivery as nucleic acids through a gene therapy approach. To this end, eukaryotic expression constructs for murine angiostatin and endostatin as well as human TIMP-2 were generated, and characterized in vitro. All constructs carry the relevant cDNAs under the control of the strong HCMV promoter/enhancer, and cleavable leader signals to allow protein secretion. Expression of the angiogenesis inhibitors was detected by in vitro transcription/translation experiments as well as transfection of 293T cells, followed by Western blotting (WB) or radioimmunoprecipitation analysis of both cell lysates and supernatants (SNs). These constructs might be used for in vivo intramuscular delivery of plasmid DNA and as a set of reagents for the development of retroviral as well as adeno-associated viral (AAV) vectors expressing angiogenesis inhibitors.

From Inflammation to Current and Alternative Therapies Involved in Wound Healing

Wound healing is a complex event that develops in three overlapping phases: inflammatory, proliferative, and remodeling. These phases are distinct in function and histological characteristics. However, they depend on the interaction of cytokines, growth factors, chemokines, and chemical mediators from cells to perform regulatory events. In this article, we will review the pathway in the skin healing cascade, relating the major chemical inflammatory mediators, cellular and molecular, as well as demonstrating the local and systemic factors that interfere in healing and disorders associated with tissue repair deficiency. Finally, we will discuss the current therapeutic interventions in the wounds treatment, and the alternative therapies used as promising results in the development of new products with healing potential.

Negative regulators of angiogenesis: important targets for treatment of exudative AMD

Angiogenesis contributes to the pathogenesis of many diseases including exudative age-related macular degeneration (AMD). It is normally kept in check by a tightly balanced production of pro- and anti-angiogenic factors. The up-regulation of the pro-angiogenic factor, vascular endothelial growth factor (VEGF), is intimately linked to the pathogenesis of exudative AMD, and its antagonism has been effectively targeted for treatment. However, very little is known about potential changes in expression of anti-angiogenic factors and the role they play in choroidal vascular homeostasis and neovascularization associated with AMD. Here, we will discuss the important role of thrombospondins and pigment epithelium-derived factor, two major endogenous inhibitors of angiogenesis, in retinal and choroidal vascular homeostasis and their potential alterations during AMD and choroidal neovascularization (CNV). We will review the cell autonomous function of these proteins in retinal and choroidal vascular cells. We will also discuss the potential targeting of these molecules and use of their mimetic peptides for therapeutic development for exudative AMD.

Molecular underpinnings of corneal angiogenesis: advances over the past decade

The cornea is maintained in an avascular state by maintaining an environment whereby anti-angiogenic factors take the upper hand over factors promoting angiogenesis. Many of the common pathologies affecting the cornea involve the disruption of such equilibrium and the shift towards new vessel formation, leading to corneal opacity and eventually-vision loss. Therefore it is of paramount importance that the molecular underpinnings of corneal neovascularization (CNV) be clearly understood, in order to develop better targeted treatments. This article is a review of the literature on the recent discoveries regarding pro-angiogenic factors of the cornea (such as vascular endothelial growth factors, fibroblast growth factor and matrix metalloproteinases) and anti-angiogenic factors of the cornea (such as endostatins and neostatins). Further, we review the molecular underpinnings of lymphangiogenesis, a process now known to be almost separate from (yet related to) hemangiogenesis.

Tumour Angiogenesis and Angiogenic Inhibitors: A Review

Angiogenesis is a complex process depending on the coordination of many regulators and there by activating angiogenic switch. Recent advances in understanding of angiogenic mechanism have lead to the development of several anti-angiogenic and anti-metastatic agents that use the strategy of regulation of angiogenic switch. Antiangiogenic therapy is a form of treatment not cure for cancer and represents a highly effective strategy for destroying tumour because vascular supply is the fundamental requirement for growth of tumour. Because of the quiescent nature of normal adult vasculature, angiogenic inhibitors are expected to confer a degree of specificity when compared to nonspecific modalities of chemo and radiotherapy, so it has the advantage of less toxicities, does not induce drug resistance and deliver a relatively non toxic, long term treatment of tumour.

Midkine lacking its last 40 amino acids acts on endothelial and neuroblastoma tumor cells and inhibits tumor development

Midkine (MDK) is a member of a new family of neurotrophic factors considered as rate-limiting growth and angiogenic factors implicated in the onset, invasion, and metastatic process of neuronal tumors, including neuroblastoma. We showed that all neuroblastoma cell lines highly expressed MDK, indicating that it is a critical player in tumor development, which may henceforth represent an attractive therapeutic target. We showed that the knockdown of MDK expression by siRNA led to a marked and significant decrease in neuroblastoma (IGR-N91 and SH-SY5Y) cell proliferation in vitro. Using a new strategy, we then evaluated the antitumor effect of a truncated MDK protein, lacking the C-terminal 81-121 portion of the molecule (MDKΔ81-121), which may act as a dominant-negative effector for its mitogenic, angiogenic, and tumorigenic activities by heterodimerizing with the wild-type protein. In vitro studies showed that MDKΔ81-121 selectively inhibited MDK-dependent tumor cells and was able to strongly reduce endothelial cell proliferation and migration and to induce ER stress-mediated apoptosis. We then investigated the effects of MDKΔ81-121 in vivo using electrotransfer of a plasmid encoding a secretable form of MDKΔ81-121 into tibialis cranialis muscles of nude mice. We showed that MDKΔ81-121 dramatically inhibited (up to 91%) tumor development and growth. This inhibition was correlated with the detection of the MDKΔ81-121 molecule in plasma and the suppression of intratumor neovascularization. Our findings demonstrate that MDK inhibition is a tractable therapeutic target for this lethal pediatric malignancy.

The Role of Chemotherapy in the Treatment of Malignant Astrocytomas

Malignant astrocytomas are aggressive neoplasms with a dismal prognosis despite optimal treatment. Maximal resective surgery is traditionally complemented by radiation therapy. Chemotherapy is now used on patients as initial therapy when their functional status is congruent with further treatment. The classic agents used are nitrosoureas, but temozolomide has taken the front seat recently, with recent data demonstrating increased survival when this agent is used concurrently with radiation therapy in newly diagnosed glioblastoma patients. A new class of agents, refered to as biological modifiers, are increasingly used in clinical trials in an effort to affect the intrinsic biologic aberrations harboured by tumor cells. These drugs comprise differentiation agents, anti-angiogenic agents, matrix-metalloproteinase inhibitors and signal transduction inhibitors, among others. This article reviews the standard cytotoxic agents that have been used to treat malignant astrocytomas, and the different combination regimens offering promise. In addition, recent advances with biological modifiers are also discussed.

Ad-endostatin treatment combined with low-dose irradiation in a murine lung cancer model

Radiation therapy is a conventional strategy for treating advanced lung cancer yet is accompanied by serious side-effects. Its combination with other strategies, such as antiangiogenesis and gene therapy, has shown excellent prospects. As one of the potent endogenous vascular inhibitors, endostatin has been widely used in the antiangiogenic gene therapy of tumors. In the present study, LL/2 cells were infected with a recombinant adenovirus encoding endostatin (Ad-endostatin) to express endostatin. The results showed that LL/2 cells infected with the Ad-endostatin efficiently and longlastingly expressed endostatin. In order to further explore the role of Ad-endostatin combined with irradiation in the treatment of cancer, a murine lung cancer model was established and treated with Ad-endostatin combined with low-dose irradiation. The results showed that the combination treatment markedly inhibited tumor growth and metastasis, and prolonged the survival time of the tumor-bearing mice. Furthermore, this significant antitumor activity was associated with lower levels of microvessel density and anoxia factors in the Ad-Endo combined with irradiation group, and with an increased apoptotic index of tumor cells. In addition, no serious side-effects were noted in the combination group. Based on our findings, Ad-endostatin combined with low-dose irradiation may be a rational alternative treatment for lung cancer and other solid tumors.

Murine experimental autoimmune encephalomyelitis is diminished by treatment with the angiogenesis inhibitors B20-4.1.1 and angiostatin (K1-3)

Angiogenesis is the formation of new blood vessels form pre-existing vasculature whose contribution to inflammatory conditions of the Central Nervous System is being studied in order to generate novel therapeutic targets. This study is the first to investigate the impact of two particular angiogenesis inhibitors on murine Experimental Autoimmune Encephalomyelitis (EAE), an inflammatory disease that mimics aspects of the human disease Multiple Sclerosis. The inhibitors were chosen to reduce angiogenesis by complimentary means. Extrinsic factors were targeted with B20-4.1.1 through its ability to bind to murine Vascular Endothelial Growth Factor (VEGF). Vascular processes connected to angiogenesis were targeted directly with K(1-3), the first three kringle domains of angiostatin. Mice treated with B20-4.1.1 and K(1-3) from onset of signs had reduced clinical scores 18–21 days after EAE induction. Both agents suppressed spinal cord angiogenesis without effect on local VEGF expression. B20-4.1.1 reduced spinal cord vascular permeability while K(1-3) had no effect. T cell infiltration into the spinal cord at day 21 was unaffected by either treatment. B20-4.1.1 reduced peripheral T cell proliferation while K(1-3) had no effect. Lymphoid cells from treated mice produced reduced levels of the T helper-17 (Th-17) cell cytokine interleukin (IL)-17 with no effect on the Th-1 cytokine interferon (IFN)-γ or Th-2 cytokine IL-4. However, when both drugs were added in vitro to naive T cells or to antigen stimulated T cells from mice with untreated EAE they had no effect on proliferation or levels of IL-17 or IFN-γ. We conclude that these angiogenesis inhibitors mitigate EAE by both suppressing spinal cord angiogenesis and reducing peripheral T cell activation.

Temporal and pharmacological characterization of angiostatin release and generation by human platelets: implications for endothelial cell migration

Platelets play an important role in thrombosis and in neo-vascularisation as they release and produce factors that both promote and suppress angiogenesis. Amongst these factors is the angiogenesis inhibitor angiostatin, which is released during thrombus formation. The impact of anti-thrombotic agents and the kinetics of platelet angiostatin release are unknown. Hence, our objectives were to characterize platelet angiostatin release temporally and pharmacologically and to determine how angiostatin release influences endothelial cell migration, an early stage of angiogenesis. We hypothesized anti-platelet agents would suppress angiostatin release but not generation by platelets. Human platelets were aggregated and temporal angiostatin release was compared to vascular endothelial growth factor (VEGF). Immuno-gold electron microscopy and immunofluorescence microscopy identified α-granules as storage organelles of platelet angiostatin. Acetylsalicylic acid, MRS2395, GPIIb/IIIa blocking peptide, and aprotinin were used to characterize platelet angiostatin release and generation. An endothelial cell migration assay was performed under hypoxic conditions to determine the effects of pharmacological platelet and angiostatin inhibition. Compared to VEGF, angiostatin generation and release from α-granules occurred later temporally during platelet aggregation. Consequently, collagen-activated platelet releasates stimulated endothelial cell migration more potently than maximally-aggregated platelets. Platelet inhibitors prostacyclin, S-nitroso-glutathione, acetylsalicylic acid, and GPIIb/IIIa blocking peptide, but not a P2Y12 inhibitor, suppressed angiostatin release but not generation. Suppression of angiostatin generation in the presence of acetylsalicylic acid enhanced platelet-stimulated endothelial migration. Hence, the temporal and pharmacological modulation of platelet angiostatin release may have significant consequences for neo-vascularization following thrombus formation.

Effects of Nicotine on the Number and Activity of Circulating Endothelial Progenitor Cells

Recently, some studies have shown that nicotine increased neovascularization, which involves endothelial progenitor cells (EPCs). The effects of nicotine on EPCs are still unclear at present. Therefore, the authors investigated whether nicotine had influences on EPC number and activity. The EPCs were stimulated with nicotine (to make a series of final concentrations: 10(-12) mol/L, 10(-10) mol/L, 10(-8) mol/L, 10(-6) mol/L, 10(-4) mol/L) or vehicle control for the respective time points(12, 18, 24, 32, and 48 hours). The EPCs were characterized as adherent cells double positive for DiLDL uptake and lectin binding by direct fluorescent staining under a laser-scanning confocal microscope. They were further documented by demonstrating the expression of KDR, VEGFR-2, and AC133 with flow cytometry. The EPC proliferation, migration, and in vitro vasculogenesis activity were assayed with the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay; the modified Boyden chamber assay; and the in vitro vasculogenesis kit, respectively. The EPC adhesion assay was performed by replating those on fibronectin-coated dishes and then counting the adherent cells. As a result, nicotine dose dependently increased the EPC number and the proliferative, migratory, adhesive, and in vitro vasculogenesis capacity at nicotine concentrations of 10(-12) to 10(-8) mol/L. The peak effects on EPCs were observed at concentrations of nicotine 10(-8) mol/L, similar to those in the blood of smokers. In addition, nicotine (10(-8) mol/L) time dependently increased the EPC number and activity. However, cytotoxicity was seen at higher nicotine concentrations (> 10(-6) mol/L). In conclusion, nicotine had complex effects on EPCs: nicotine might induce the augmentation of EPCs with enhanced functional activity at relatively low concentrations. However, cytotoxicity was seen at higher nicotine concentrations.

Angiostatin inhibits endothelial MMP-2 and MMP-14 expression: a hypoxia specific mechanism of action

Angiostatin is an angiogenesis inhibitor in part generated by and released from platelets. Since platelets upon thrombus formation can give rise to areas of hypoxia, we investigated the effects of angiostatin on endothelial cell migration and apoptosis during hypoxia. Human microvascular endothelial cells (HMVEC-L) were exposed to angiostatin under normoxic or hypoxic conditions. Apoptosis was measured by flow-cytometry. HMVEC-L migration was studied using a modified Boyden Chamber assay, in which migration is MMP-dependent. MMP-2, MMP-14, and VEGF levels were measured using immunoblot, Q-PCR and ELISA. During hypoxia HMVEC-L were protected from angiostatin-induced apoptosis due to increased hypoxia-induced VEGF expression. However, MMP-dependent migration of HMVEC-L was inhibited by angiostatin under hypoxic but not normoxic conditions. Angiostatin decreased MMP-2 at the gene and protein levels only in HMVEC-L exposed to hypoxia. A similar result was obtained for MMP-14. Higher angiostatin concentrations, as would be seen during thrombosis, induced HMVEC-L apoptosis, which was not rescued by VEGF. Under hypoxic conditions angiostatin's primary anti-angiogenic mechanism is likely inhibition of endothelial cell MMP-dependent endothelial cell migration. Only at higher concentrations does angiostatin induce endothelial cell death. This study identifies a novel angiostatin anti-angiogenesis mechanism that is only triggered under pathological-like conditions.

Macrophage inhibitory cytokine-1 stimulates proliferation of human umbilical vein endothelial cells by up-regulating cyclins D1 and E through the PI3K/Akt-, ERK-, and JNK-dependent AP-1 and E2F activation signaling pathways

Macrophage inhibitory cytokine-1 (MIC-1) is highly associated with malignant human cancers and has been suggested to be involved in tumor angiogenesis. In the present study, we examined the effect of MIC-1 on endothelial cell proliferation to confirm the angiogenesis-promoting role of MIC-1. MIC-1 treatment accelerated progression of the G(1) stage in the cell cycle of human umbilical vein endothelial cells (HUVECs), leading to an increased cell proliferation rate. MIC-1 augmented the levels of cyclins D1 and E without altering the levels of cyclin-dependent kinase (CDK) inhibitors, thereby increasing protein kinase activity of CDKs and subsequent phosphorylation of the Rb protein followed by nuclear translocation of E2F. MIC-1-induced expression of cyclins D1 and E was mediated by AP-1 and E2F-1 transcription factors, and among the AP-1 members, c-Jun and JunD appeared to participate in MIC-1-dependent transcription of the cyclin D1 gene. Additionally, the PI3K/Akt, JNK, and ERK pathways were found to mediate MIC-1-induced cyclin D1 expression in HUVECs. Importantly, lung endothelial cells isolated from MIC-1 transgenic mouse displayed a higher proliferation rate and cyclin D1 and E levels relative to their wild-type counterparts. These results suggest that MIC-1 secreted from cancer cells stimulates endothelial cell proliferation by enhancing AP-1- and E2F-dependent expression of G(1) cyclins via PI3K/Akt, JNK, and ERK signaling pathways, potentially leading to enhanced tumor angiogenesis.

Inflammatory corneal neovascularization: etiopathogenesis

There is a delicate balance between pro-angiogenic stimuli and anti-angiogenic stimuli in the normal cornea. This balance allows the cornea to normally exist in a relatively avascular state, which is needed for optical clarity and vision. However, in the setting of inflammation, this balance may be shifted in favor of neovascularization. This paper reviews the literature on corneal inflammatory neovascularization beginning with the pro-angiogenic factors, such as Vascular Endothelial Growth Factor and Fibroblast Growth Factor, which help to facilitate the development of new corneal vessels. Subsequently the anti-angiogenic factors and their role in preventing neovascularization in the normal cornea are reviewed. Finally, a review of several etiologies of inflammatory neovascularization is presented with attention to the processes that allow the pro-angiogenic stimuli to overwhelm the anti-angiogenic factors.

High efficacy and minimal peptide required for the anti-angiogenic and anti-hepatocarcinoma activities of plasminogen K5

Kringle 5(K5) is the fifth kringle domain of human plasminogen and its anti-angiogenic activity is more potent than angiostatin that includes the first four kringle fragment of plasminogen. Our recent study demonstrated that K5 suppressed hepatocarcinoma growth by anti-angiogenesis. To find high efficacy and minimal peptide sequence required for the anti-angiogenic and anti-tumour activities of K5, two deletion mutants of K5 were generated. The amino acid residues outside kringle domain of intact K5 (Pro452-Ala542) were deleted to form K5mut1(Cys462-Cys541). The residue Cys462 was deleted again to form K5mut2(Met463-Cys541). K5mut1 specifically inhibited proliferation, migration and induced apoptosis of endothelial cells, with an apparent two-fold enhanced activity than K5. Intraperitoneal injection of K5mut1 resulted in more potent tumour growth inhibition and microvessel density reduction than K5 both in HepA-grafted and Bel7402-xenografted hepatocarcinoma mouse models. These results suggested that K5mut1 has more potent anti-angiogenic activity than intact K5. K5mut2, which lacks only the amino terminal cysteine of K5mut1, completely lost the activity, suggesting that the kringle domain is essential for the activity of K5. The activity was enhanced to K5mut1 level when five acidic amino acids of K5 in NH₂ terminal outside kringle domain were replaced by five serine residues (K5mut3). The shielding effect of acidic amino acids may explain why K5mut1 has higher activity. K5, K5mut1 and K5mut3 held characteristic β-sheet spectrum while K5mut2 adopted random coil structure. These results suggest that K5mut1 with high efficacy is the minimal active peptide sequence of K5 and may have therapeutic potential in liver cancer.

Single doublecortin gene therapy significantly reduces glioma tumor volume

We employed lentivirus-based doublecortin (DCX), as a glioma suppressor gene therapy in an intracranial glioma tumor xenograft model in nude rats. Single DCX-expressing lentivirus was directly administered into the tumor on day 8 after U87 tumor cell implantation. DCX treatment significantly reduced U87 glioma tumor volume (approximately 60%) on day 14 after DCX lentivirus injection and significantly improved median survival of tumor-bearing nude rats. DCX synthesis induced neuronal markers MAP2, TUJ1, and PSA-NCAM and the glial marker glial fibrillary acidic protein (GFAP) in the implanted U87 glioma tumors. DCX synthesis induced GFAP that colocalized with tubulin in the mitotic stage, inhibited cleavage furrow during cytokinesis, and blocked mitosis in glioma cells. DCX lentivirus infection did not induce apoptosis but significantly inhibited expression of the proliferation marker Ki-67 and the blood vessel marker von-Willebrand factor (vWF). U87 and other glioma cells except for brain tumor stem cells (BTSCs) do not express neuronal markers or both neuronal and glial markers. DCX-synthesizing glioma cells express a phenotype of antiangiogenic BTSC-like cells with terminal differentiation that causes remission of glioma cells by blocking mitosis via a novel DCX/GFAP pathway. Direct local delivery of lentivirus-based DCX gene therapy is a potential differentiation-based therapeutic approach for the treatment of glioma.

Efficient delivery of angiostatin K1-5 into tumors following insertion of an NGR peptide into adenovirus capsid

Adenovirus (Ad)-mediated delivery of anti-angiogenic molecules into tumors constitutes an appealing approach for growth inhibition. However, lack of expression on tumors of Ad receptors leads to weak tumor transduction. Therefore, to provide Ad with a new entry pathway into tumors, an NGR peptide was inserted into either fiber (AdFNGR) or hexon (AdHNGR) capsid proteins. This strategy provided Ad with a very efficient entry pathway in both endothelial cells and tumor cells, with the highest efficacy observed for AdHNGR. Using pharmacological, biochemical and genetic approaches, AdHNGR and AdFNGR were shown to bind not only to CD13 receptor, but also to alphavbeta3 integrins. Both vectors were efficient tools to deliver angiostatin K1-5 cDNA into endothelial cells, thus leading to a dramatic inhibition of their proliferation and increased cell death. Although AdHNGR and Adwt were found to display similar gene transduction efficacy in Lewis lung carcinoma (LLC), pseudotyping AdHNGR with an Ad3-fiber unmasked the ability of NGR-peptide to target these tumors. As a result, delivery of angiostatin K1-5 cDNA into highly aggressive tumors translated into a stronger inhibition of their growth. Altogether, our results suggest that NGR-bearing Ad are valuable tools to realize the potential of this anti-angiogenic approach to anti-tumor therapy.

Novel aspects of corneal angiogenic and lymphangiogenic privilege

In this article, we provide the results of experimental studies demonstrating that corneal avascularity is an active process involving the production of anti-angiogenic factors, which counterbalance the pro-angiogenic/lymphangiogenic factors that are upregulated during wound healing. We also summarize pertinent published reports regarding corneal neovascularization (NV), corneal lymphangiogenesis and corneal angiogenic/lymphangiogenic privilege. We outline the clinical causes of corneal NV, and discuss the angiogenic proteins (VEGF and bFGF) and angiogenesis regulatory proteins. We also describe the role of matrix metalloproteinases MMP-2, -7, and MT1-MMP, anti-angiogenic factors, and lymphangiogenic regulatory proteins during corneal wound healing. Established and potential new therapies for the treatment of corneal neovascularization are also discussed.

Breast cancer cell surface annexin II induces cell migration and neoangiogenesis via tPA dependent plasmin generation

Annexin II, an abundant phospholipids binding cell surface protein, binds tPA and functions as a regulator of fibrinolysis. Annexin II also mediates angiogenesis and enhances tumor growth and metastasis. However, the mechanism supporting this role is not known. Using human breast cancer model we show that invasive human breast cancer cells (MDA-MB231) synthesize annexin II and tissue plasminogen activator (tPA). In vitro both annexin II and tPA interacts which in turn convert zymogen plasminogen to reactive enzyme plasmin. Cell surface produced plasmin inhibited the migration of MDA-MB231 cells. Silencing of annexin II gene in MDA-MB231 cells abolished tPA binding therefore inhibited tPA dependent plasmin generation. These annexin II suppressed MDA-MB231 cells showed reduced motility. Immunohistochemical analysis of prediagnosed clinical specimens showed abundant secretion of tPA and expression of annexin II on the surface of invasive human breast cancer cells which correlates with neovascularization of the tumor. Taken together, these data indicate that annexin II may regulate localized plasmin generation in breast cancer. This may be an early event switching breast cancer from the prevascular phase to the vascular phase and thus contributing to aggressive cancer with the possibility of metastasis. The data provide a mechanism explaining the role of annexin II in breast cancer progression and suggest that annexin II may be an attractive target for therapeutic strategies aimed to inhibit angiogenesis and breast cancer.

Cloning, expression and in vitro evaluation of recombinant canine Tum5, an angiostatic domain of mammalian type IV collagen

The process of new blood vessel formation within and around neoplastic tissue, termed angiogenesis, is a significant factor in the development, progression and metastasis of malignant tumours in all species. A major cause of death in cancer patients is the development of treatment-resistant metastatic disease, which may be avoided by therapies that target the genetically stable population of vascular endothelial cells within tumours. Tumstatin is a small protein formed by the cleavage of the alpha-3 subunit of the non-collagenous domain of mammalian type IV collagen. Recombinant human Tumstatin has been shown to have potent angiostatic properties in vitro and in vivo. Tumstatin is a potent initiator of apoptosis and inhibits the proliferation and migration of vascular endothelial cells in cell culture. Recently, a fragment of Tumstatin, termed Tum5, has been shown to have biologic activity similar to the parent compound. The systemic administration of angiostatic proteins like Tum5 may result in the remission of established tumours, while preventing or delaying the onset of clinically detectable metastasis. Recombinant canine Tum5 (cTum5) was cloned and its protein expression induced in a prokaryotic vector. The resulting cTum5 protein caused dose-dependent inhibition of vascular endothelial cells in vitro, which appears to be mediated through apoptosis.

Combining kallistatin gene therapy and meloxicam to treat hepatocellular carcinoma in mice

Hepatocellular carcinoma (HCC) is one of the most common cancer-related causes of death, and conventional treatments offer unsatisfactory response. We have previously reported that kallistatin gene therapy suppressed the growth of HCC tumors by its anti-angiogenic activity, and meloxicam, a selective COX-2 inhibitor, inhibited proliferation and induced apoptosis of human HCC cells in vitro. The aim of this study was to determine whether combining kallistatin gene therapy and meloxicam could offer a better therapeutic effect to combat HCC in mice. A kallistatin expression plasmid was constructed and its expression was detected after intratumoral gene transfer. Both kallistatin gene therapy and meloxicam suppressed the growth of subcutaneous human HepG2 tumors established in BALB/c nude mice, and the combinational therapy showed a stronger effect in suppressing tumor growth, tumor angiogenesis and cell proliferation, and increasing cell apoptosis, than the respective monotherapies. Gene transfer of kallistatin inhibited tumor angiogenesis, and slightly inhibited cell proliferation and increased cell apoptosis in situ, but had no effect on expression of vascular endothelial growth factor, basic fibroblast growth factor, proliferating cell nuclear antigen, Bcl-2, Bax, or activation of caspase-3. Meloxicam therapy inhibited cell proliferation, induced cell apoptosis, reduced expression of proliferating cell nuclear antigen, increased activation of caspase-3, and upregulated Bax. Meloxicam also slightly inhibited tumor angiogenesis with no effect on the expression of vascular endothelial growth factor or basic fibroblast growth factor. Combining two novel anticancer agents, kallistatin targeting tumoral vascularization and meloxicam targeting cell proliferation and apoptosis, warrants investigation as a therapeutic strategy to combat HCC.

Adeno-associated virus-mediated expression of kallistatin suppresses local and remote hepatocellular carcinomas

BACKGROUND

The current treatments for hepatocellular carcinoma (HCC) are poor, particularly for metastatic HCC. Intraportal transfusion of adeno-associated virus (AAV) leads to long-term and persistent transgenic expression in livers. Kallistatin, a novel angiogenesis inhibitor, exhibits anti-tumor activity. The aim of the study was to investigate whether intraportal injection of AAV-kallistatin could suppress local and metastatic HCC in mice.

METHODS

An AAV vector encoding kallistatin was constructed, and its transduction efficiency by intraportal transfusion in livers was examined by RT-PCR, immunohistochemical and Western blotting analysis. The anti-tumor activity was tested in three HCC models including hepatic and subcutaneous human Hep3B HCC tumors in BALB/c athymic (nu/nu) mice, and subcutaneous mouse BNL HCC tumors in BALB/c mice. Tumor cell proliferation in situ was examined by anti-Ki-67 staining, and apoptosis by TUNEL.

RESULTS

Gene transfection by rAAV-kallistatin inhibited proliferation of human umbilical vein endothelial cells and HCC cells in vitro. Intraportal injection of rAAV-kallistatin resulted in persistent and specific expression of kallistatin in livers detected by RT-PCR and immunohistochemical analysis, and kallistatin protein in circulation detected by Western blotting analysis. Intraportal injection of rAAV-kallistatin significantly suppressed angiogenesis and growth of hepatic Hep3B tumors. The kallistatin released by hepatocytes into the circulation suppressed remote Hep3B and BNL tumors established subcutaneously. The rAAV-kallistatin gene therapy significantly inhibited tumor cell proliferation and induced apoptosis.

CONCLUSIONS

Intraportal injection of rAAV-kallistatin suppressed hepatic and subcutaneous HCC tumors, relying on its anti-angiogenic and anti-proliferative activities.

Plasminogen derivatives encoding kringles 1-4 and kringles 1-5 exert indirect antiangiogenic and direct antitumoral effects in experimental lung cancer

Recently, increasing evidence has been found demonstrating direct effects of angiostatin on tumor cells themselves. We have applied the plasminogen derivatives K1-4 and K1-5 to a lung cancer model to analyse indirect angiostatic effects against endothelial and direct effects against tumor cells. In accordance with preceding findings both derivatives inhibited endothelial cell functions in vitro. Additionally K1-4 and K1-5 have also shown substantial anti-proliferative and pro-apoptotic effects in tumor cells and have inhibited tumor growth. In addition our data supports the recent conclusion that plasminogen derivatives have a dual antitumor mechanism affecting both tumor angiogenesis and tumor cells.

Prostate-restricted replicative adenovirus expressing human endostatin-angiostatin fusion gene exhibiting dramatic antitumor efficacy

PURPOSE

Our previous studies coadministering a replication-deficient adenovirus expressing endostatin and angiostatin fusion gene (EndoAngio) and a prostate-restricted, replication-competent adenovirus (PRRA) showed dramatic antitumor efficacy. This study integrated EndoAngio with an improved PRRA vector to make a single antiangiogenic PRRA, thereby exerting a similarly dramatic antitumor effect with feasibility for future clinical trials.

EXPERIMENTAL DESIGN

We developed an antiangiogenic PRRA with structural improvements. The antitumor efficacy of EndoAngio-PRRA was evaluated in prostate-specific antigen/prostate-specific membrane antigen (PSA/PSMA)-positive, androgen-independent CWR22rv tumor models. The tumor vasculature and cell morphology were observed by dual-photon microscopy. The antiangiogenic effect of EndoAngio delivered by PRRA and the killing activity of EndoAngio-PRRA were evaluated in vitro. Virus-inactivated conditioned media from virus-infected PSA/PSMA-positive cells were tested for apoptosis induction in prostate cancer cells.

RESULTS

Our novel EndoAngio-PRRA is a strong antiangiogenic and antitumor agent. Nine of 10 CWR22rv tumors treated by EndoAngio-PRRA completely regressed, with 1 tumor remaining in a dormant status for 26 weeks after treatment. Dual-photon microscopy revealed that EndoAngio-PRRA not only inhibited the development of tumor vasculature but also induced apoptosis in tumor cells. Subsequent in vitro study indicated that EndoAngio-PRRA exhibited stronger tumor-specific killing activity than enhanced green fluorescent protein-PRRA, which expresses enhanced green fluorescent protein instead of EndoAngio. Virus-inactivated conditioned medium from EndoAngio-PRRA-infected PSA/PSMA-positive cells induced apoptosis in C4-2 and CWR22rv cells.

CONCLUSIONS

EndoAngio-PRRA uniquely combines three distinct antitumor effects to eliminate androgen-independent prostate cancer: antiangiogenesis, viral oncolysis, and apoptosis. This novel antiangiogenic PRRA represents a powerful agent feasible for future clinical trials for prostate cancer therapy.

Position-dependent expression of GADD45alpha in rat brain tumours

Although the complex and multifactorial process of tumour growth has been extensively studied for decades, our understanding of the fundamental relationship between tumour growth dynamics and genetic expression profile remains incomplete. Recent studies of tumour dynamics indicate that gene expression in solid tumours would depend on the distance from the centre of the tumour. Since tumour proliferative activity is mainly localised to its external zone, and taking into account that generation and expansion of genetic mutations depend on the number of cell divisions, important differences in gene expression between central and peripheral sections of the same tumour are to be expected. Here, we have studied variations in the genetic expression profile between peripheral and internal samples of the same brain tumour. We have carried out microarray analysis of mRNA expression, and found a differential profile of genetic expression between the two cell subsets. In particular, one major nuclear protein that regulates cell responses to DNA-damaging and stress signals, GADD45alpha, was expressed at much lower levels in the peripheral zone, as compared to tumour core samples. These differences in GADD45alpha mRNA transcription levels have been confirmed by quantitative analysis via real time PCR, and protein levels of GADD45alpha also exhibit the same pattern of differential expression. Our findings suggest that GADD45alpha might play a major role in the regulation of brain tumour invasive potential.

Kallikrein-binding protein suppresses growth of hepatocellular carcinoma by anti-angiogenic activity

Effect of kallikrein-binding protein (KBP), an endogenous angiogenic inhibitor, on the growth of hepatocellular carcinoma and the possible mechanism were investigated. KBP inhibited proliferation and induced apoptosis of endothelial cells, but had no effect on the proliferation and apoptosis of hepatocarcinoma cell line HepG2. Intraperitoneal injection of KBP significantly suppressed the tumor growth and inhibited intratumoral neovascularization both in grafted hepatocarcinoma mice and xenografted hepatocarcinoma athymic mice. Moreover, KBP reduced expression of VEGF and HIF-1alpha nuclear translocation in HepG2 cells and xenografts. Down-regulation of VEGF in tumor cells through inhibiting HIF-1alpha may represent a novel mechanism for the anti-angiogenic and anti-tumor activity of KBP.

Angiostatin and integrin ?v?3 in the feline, bovine, canine, equine, porcine and murine retina and cornea

PURPOSE

Angiogenesis is tightly controlled in the ocular tissues of domestic animals but its mechanisms are not fully understood. This is largely because of insufficient data on the expression of molecules that impact angiogenesis. Because angiostatin and one of its receptors integrin alphavbeta3 inhibit and promote angiogenesis, respectively, we hypothesized that the normal retina and cornea of domestic animals would express angiostatin but not integrin alphavbeta3.

PROCEDURE

Normal eyes of the cat, cow, dog, horse, pig and rat were evaluated for angiostatin and integrin alphavbeta3 by light and electron immunocytochemistry and estern blots.

RESULTS

Angiostatin was detected in the corneal epithelium of the cat, dog, horse, pig and rat, but was not found in cow corneal epithelium. Angiostatin was localized in the nerve fiber layer, ganglion cell layer, inner and outer plexiform layers, and the photoreceptor layer of the cat, cow, dog and rat. Horse and pig retinas showed additional staining in the matrix of the inner nuclear layer. Immunogold electron microscopy further confirmed angiostatin in cat retina. Western blots showed angiostatin in corneal and retinal homogenates. Integrin alphavbeta3 was absent in cornea and retina of all the species studied.

CONCLUSION

These data show that angiostatin, an inhibitor of angiogenesis, is present while integrin alphavbeta3, which promotes angiogenesis, is absent in normal cornea and retina of the domestic animals in this study with the exception being angiostatin absence in cow corneal epithelium. Therefore, angiostatin may contribute to the anti-angiogenic environment in the normal domestic animal eye while its absence in the cow may contribute to greater propensity for corneal vascularization. Because integrin alphavbeta3 is one of the receptors for angiostatin, its absence may prevent angiostatin from killing normal retinal and corneal cells.

Gene transfer of endostatin enhances the efficacy of doxorubicin to suppress human hepatocellular carcinomas in mice

Hepatocellular carcinoma (HCC) is one of the most common cancer-related causes of death, and is chemoresistant to anticancer drugs. Anti-angiogenic therapy has been shown to enhance the efficacy of chemotherapy to treat solid tumors. The aim of the present study was to determine whether endostatin, a potent antiangiogenic agent, could enhance the efficacy of doxorubicin to combat HCC. An endostatin expression plasmid was constructed and its expression in vitro and in vivo was detected after gene transfer. Recombinant endostatin inhibited angiogenesis in the chorioallantoic membrane assay, and showed synergistic effects with doxorubicin in inhibiting the in vitro proliferation of endothelial cells, but not that of tumor cells. Both endostatin gene therapy and doxorubicin suppressed the growth of subcutaneous human HepG2 tumors established in BALB/c nude mice, and tumor angiogenesis. Combination therapy with endostatin gene therapy and doxorubicin showed a stronger effect in suppressing tumor growth, and tumor angiogenesis, than the respective monotherapies. Gene transfer of endostatin down-regulated the expression of both hypoxia-inducible factor-1alpha and vascular endothelial growth factor (VEGF), whereas doxorubicin only down-regulated VEGF expression. Endostatin and doxorubicin synergized to down-regulate VEGF expression. Endostatin and doxorubicin combination therapy warrants investigation as a therapeutic strategy to combat HCC.

Endostatin gene therapy enhances the efficacy of paclitaxel to suppress breast cancers and metastases in mice

Chemotherapy combined with antiangiogenic therapy is more effective than chemotherapy alone. The aim of this study was to investigate whether endostatin, a potent anti-angiogenic agent, could enhance the efficacy of paclitaxel to combat breast cancer. An expression plasmid encoding mouse endostatin (End-pcDNA3.1) was constructed, which produced intense expression of endostatin and inhibited angiogenesis in the chorioallantoic membrane assay. 4T1 breast tumors were established in BALB/c mice by subcutaneous injection of 1 x 10(5) 4T1 cells. The End-pcDNA3.1 plasmid diluted in the transfection reagent FuGENE was injected into the tumors (around 100 mm(2)), and paclitaxel was injected i.p. into the mice. Endostatin gene therapy synergized with paclitaxel in suppressing the growth of 4T1 tumors and their metastasis to the lung and liver. Both endostatin and paclitaxel inhibited tumor angiogenesis and induced cell apoptosis. Despite the finding that endostatin was superior to paclitaxel at inhibiting tumor angiogenesis, paclitaxel was nevertheless more effective at inducing tumor apoptosis. The combination of paclitaxel and endostatin was more effective in suppressing tumor growth, metastases, angiogenesis, and inducing apoptosis than the respective monotherapies. The combinational therapy with endostatin and paclitaxel warrants future investigation as a therapeutic strategy to combat breast cancer.

Antitumor effects of non-replicative herpes simplex vectors expressing antiangiogenic proteins and thymidine kinase on Lewis lung carcinoma establishment and growth

There is growing evidence that combinations of antiangiogenic proteins with other antineoplastic treatments such as chemo- or radiotherapy and suicide genes-mediated tumor cytotoxicity lead to synergistic effects. In the present work, we tested the activity of two non-replicative herpes simplex virus (HSV)-1-based vectors, encoding human endostatin::angiostatin or endostatin::kringle5 fusion proteins in combination with HSV-1 thymidine kinase (TK) molecule, on endothelial cells (ECs) and Lewis lung carcinoma (LLC) cells. We observed a significant reduction of the in vitro growth, migration and tube formation by primary ECs upon direct infection with the two recombinant vectors or cultivation with conditioned media obtained from the vector-infected LLC cells. Moreover, direct cytotoxic effect of HSV-1 TK on both LLC and ECs was demonstrated. We then tested the vectors in vivo in two experimental settings, that is, LLC tumor growth or establishment, in C57BL/6 mice. The treatment of pre-established subcutaneous tumors with the recombinant vectors with ganciclovir (GCV) induced a significant reduction of tumor growth rate, while the in vitro infection of LLC cells with the antiangiogenic vectors before their implantation in mice flanks, either in presence or absence of GCV, completely abolished the tumor establishment.

Angiogenesis in diabetic nephropathy

Angiogenesis, the formation of new blood vessels from pre-existing vasculature, plays a key role in both physiologic and pathologic events, including wound healing, cancer, and diabetes. Neovascularization has been implicated in the genesis of diverse diabetic complications such as retinopathy, impaired wound healing, neuropathy, and, most recently, diabetic nephropathy. Diabetic nephropathy is one of the major microvascular-associated complications in diabetes and is the leading cause of end-stage renal disease worldwide. In this review we describe the major factors involved in the pathologic glomerular microvascular alterations in response to hyperglycemia and the possible use of anti-angiogenic therapies for the treatment of diabetic nephropathy.

Anti-angiogenic gene therapy of cancer: current status and future prospects

The discovery of endogenous inhibitors of angiogenesis has made it possible to test the hypothesis that blocking the angiogenic switch may keep tumor growth in check, and has added a new investigational arm to the field of cancer gene therapy. Angiogenesis inhibitors are heterogeneous in origin and potency, and their growing list includes proteolysis products of larger molecules with a different function, such as angiostatin, endostatin and vasostatin, modulators of vascular endothelial growth factor activity, such as sFLT-1, and some cytokines/chemokines with marked anti-endothelial activity, such as IL-12, IFN-alpha, and CXCL10. Pre-clinical studies have clearly indicated that these factors are essentially cytostatic and that they need long-term administration in order to obtain prolonged anti-tumor effects, representing a rational basis for their delivery by a gene therapy approach. The experimental approaches attempted to date, reviewed herein, indicate overall that anti-angiogenic gene therapy has efficacy mainly as an early intervention strategy and that a better understanding of the biological mechanisms underlying resistance to angiogenesis inhibition, as well as appropriate combined treatments, are required to generate a conceptual advancement which could drive the field towards successful management of established tumors.

Different ways to antiangiogenesis by angiostatin and suramin, and quantitation of angiostatin-induced antiangiogenesis

Angiogenesis, i.e. sprouting of new vessels, their remodelling and regression, is a prerequisite for growth and differentiation of organs and tissues. It is involved in many pathological processes, particularly growth and metastasis of tumours. Angiostatic therapy is a promising new strategy in the treatment of cancer. Angiogenesis inhibitors could intervene in the different phases of the angiogenic cascade, i.e. migration, proliferation, differentiation and three-dimensional organisation of endothelial cells, to inhibit the generation of tumour vessels. The aim of this study was to explore whether in a previously validated in vitro model for quantitation of angiogenesis the effects of the angiostatic factors angiostatin and suramin can be investigated and quantified. Examination of angiostatin and suramin showed that angiostatin-induced antiangiogenesis resulted in inverse angiogenesis. The addition of suramin initially resulted in increased angiogenesis. However, long-term incubation ultimately led to disintegration of endothelial structures, thus establishing the angiostatic effects of suramin. Antiangiogenesis was not only quantified using the previously validated method. It also lent itself to assessment of the extent of antiangiogenesis within the various phases of the angiogenic cascade. This method may therefore be employed in trial studies of potential angiostatic substances and related cellular mechanisms.

Respective roles of TNF-alpha and IL-6 in the immune response-elicited by adenovirus-mediated gene transfer in mice

The immunogenicity of recombinant adenoviruses (Ad) constitutes a major concern for their use in gene therapy. Antibody- and cell-mediated immune responses triggered by adenoviral vectors hamper long-term transgene expression and efficient viral readministration. We previously reported that interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha play an essential role in both the acute phase and antibody response against Ad, respectively. As TNF-alpha controls the immune response and the development of the immune system, we examined here the consequence of blockade of TNF-alpha activity through Ad-mediated gene delivery of a dimeric mouse TNFR1-IgG fusion protein on transgene expression from a second Ad. Ad encoding TNFR1-IgG (AdTNFR1-Ig) was injected intravenously along with Ad encoding beta-galactosidase or alpha1-antitrypsin transgene in wild-type (IL-6(+/+)) but also in IL-6-deficient mice (IL-6(-/-)) to analyze how TNF-alpha and IL-6 diminish liver gene transfer efficacy. Blockade of TNF-alpha leads to increased transgene expression in both wild-type and IL-6(-/-) mice due to a reduced inflammatory response and to diminished recruitment of macrophages and NK cells towards the liver. Antibody responses against adenoviral particles and expressed transgenes were only delayed in AdTNFR1-Ig-treated wild-type mice, but were markedly reduced in AdTNFR1-Ig-treated IL-6(-/-) mice. Finally, treatment of mice with etanercept, a clinically approved anti-TNF-alpha drug, confirmed the importance of controlling proinflammatory cytokines during gene therapy by adenoviral vectors.

A gene transfer comparative study of HSA-conjugated antiangiogenic factors in a transgenic mouse model of metastatic ocular cancer

Different antiangiogenic and antimetastatic recombinant adenoviruses were tested in a transgenic mouse model of metastatic ocular cancer (TRP1/SV40 Tag transgenic mice), which is a highly aggressive tumor, developed from the pigmented epithelium of the retina. These vectors, encoding amino-terminal fragments of urokinase plasminogen activator (ATF), angiostatin Kringles (K1-3), endostatin (ES) and canstatin (Can) coupled to human serum albumin (HSA) were injected to assess their metastatic and antiangiogenic activities in our model. Compared to AdCO1 control group, AdATF-HSA did not significantly reduce metastatic growth. In contrast, mice treated with AdK1-3-HSA, AdES-HSA and AdCan-HSA displayed significantly smaller metastases (1.19+/-1.19, 0.87+/-1.5, 0.43+/-0.56 vs controls 4.04+/-5.12 mm3). Moreover, a stronger inhibition of metastatic growth was obtained with AdCan-HSA than with AdK1-3-HSA (P=0.04). Median survival was improved by 4 weeks. A close correlation was observed between the effects of these viruses on metastatic growth and their capacity to inhibit tumor angiogenesis. Our study indicates that systemic antiangiogenic factors production by recombinant adenoviruses, particularly Can, might represent an effective way of delaying metastatic growth via inhibition of angiogenesis.

Antibody-directed targeting of angiostatin's receptor annexin II inhibits Lewis Lung Carcinoma tumor growth via blocking of plasminogen activation: Possible biochemical mechanism of angiostatin's action

Angiostatin, the N-terminal four kringles (K1-4) of parent molecule plasminogen, is reported to block Lewis Lung Carcinoma (LLC) tumor growth and metastasis. However, angiostatin's mechanism of action is unclear. We earlier reported that angiostatin binds to cell surface annexin II through the lysine-binding domain (kringles 1-4) [Tuszynski, G.P., Sharma, M., Rothman, V.L., Sharma, M.C., 2002. Angiostatin binds to tyrosine kinase substrate annexin II through the lysine-binding domain in endothelial cells. Microvasc. Res. 64:448-462.]). We now show that annexin II on the cell surface of LLC cells regulates conversion of plasminogen to plasmin. Activation of plasminogen to plasmin is time-dependent, with the linear activation lasting up to 120 min. Monoclonal antibodies to annexin II reduced plasminogen activation by 92.6%, suggesting a specific role of annexin II in plasmin generation. Angiostatin also reduced plasmin generation by 81.6%, suggesting that angiostatin may be competing with plasminogen through lysine-binding domain. epsilon-Aminocaproic acid, a lysine analogue, effectively blocked plasminogen activation indicating that, indeed, the lysine-binding site of the kringles domain is required for activation. These data suggest that annexin II may be a receptor target for angiostatin's action. Therefore, we tested the effect of high affinity monoclonal antibody to annexin II in mouse model of LLC. A single dose of antibody treatment inhibited LLC tumor growth almost 70% with concomitant inhibition of circulating plasmin generation and its proteolytic activity. Taken together, it is possible that inhibition of LLC tumor growth and metastasis reported by angiostatin therapy may be due to blocking of annexin-II-dependent plasmin generation. Plasmin is known to influence angiogenic, invasive and metastatic capability of tumors.

New therapies for hepatocellular carcinoma

Hepatocellular carcinoma (HCC), one of the most common cancers worldwide, is often diagnosed at an advanced stage when most potentially curative therapies such as resection, transplantation or percutaneous and transarterial interventions are of limited efficacy. The fact that HCC is resistant to conventional chemotherapy, and is rarely amenable to radiotherapy, leaves this disease with no effective therapeutic options and a very poor prognosis. Therefore, the development of more effective therapeutic tools and strategies is much needed. HCCs are phenotypically and genetically heterogeneous tumors that commonly emerge on a background of chronic liver disease. However, in spite of this heterogeneity recent insights into the biology of HCC suggest that certain signaling pathways and molecular alterations are likely to play essential roles in HCC development by promoting cell growth and survival. The identification of such mechanisms may open new avenues for the prevention and treatment of HCC through the development of targeted therapies. In this review we will describe the new potential therapeutic targets and clinical developments that have emerged from progress in the knowledge of HCC biology, In addition, recent advances in gene therapy and combined cell and gene therapy, together with new radiotherapy techniques and immunotherapy in patients with HCC will be discussed.

Expression of non-signaling membrane-anchored death receptors protects murine livers in different models of hepatitis

Fas and tumor necrosis factor receptor 1 (TNFR1) are death receptors involved in various diseases such as hepatitis, sepsis, or graft rejection. Neutralizing antibodies to death ligands or soluble death receptors can inhibit cell death; however, they induce side effects because of their systemic actions. To specifically block death signaling to target cells, we created death domain-deficient (DeltaDD) membrane-anchored receptors, delivered to the liver by either recombinant adenovirus or hydrodynamic pressure of nonviral recombinant plasmids. In anti-Fas antibody-induced fulminant hepatitis, mice expressing recombinant Fas-decoy receptors (FasDeltaDD) in their livers were completely protected against apoptosis and survived fulminant hepatitis. In T-cell-dependent concanavalin A-induced autoimmune hepatitis, FasDeltaDD antagonist expression prevented hepatocyte damage and mouse death. Finally, TNFR1DeltaDD effectively protected mice against LPS-induced septic shock. In conclusion, such DeltaDD-decoy receptors act as dominant-negative receptors exerting local inhibition, while avoiding systemic neutralization of apoptosis ligands, and might have therapeutic potential in hepatitis.

Combination therapy of androgen-independent prostate cancer using a prostate restricted replicative adenovirus and a replication-defective adenovirus encoding human endostatin-angiostatin fusion gene

Although prostate-restricted replicative adenovirus has exhibited significant antitumor efficacy in preclinical studies, it is necessary to develop more potent adenoviruses for prostate cancer gene therapy. We evaluated the synergistic killing effect of prostate-restricted replicative adenovirus and AdEndoAngio, a replication-defective adenovirus expressing the endostatin-angiostatin fusion protein (EndoAngio). When coadministered with AdEndoAngio, prostate-restricted replicative adenovirus significantly elevated EndoAngio expression, suggesting that AdEndoAngio coreplicates with prostate-restricted replicative adenovirus. Conditioned medium from prostate cancer cells infected by prostate-restricted replicative adenovirus plus AdEndoAngio inhibited the growth, tubular network formation, and migration of human umbilical vein endothelial cells better than conditioned medium from prostate cancer cells infected by AdEndoAngio alone. Furthermore, in vivo animal studies showed that the coadministration of prostate-restricted replicative adenovirus plus AdEndoAngio resulted in the complete regression of seven out of eight treated androgen-independent CWR22rv tumors, with a tumor nodule maintaining a small size for 14 weeks. The residual single tumor exhibited extreme pathologic features together with more endostatin-reactive antibody-labeled tumor cells and fewer CD31-reactive antibody-labeled capillaries than the AdEndoAngio-treated tumors. These results show that combination therapy using prostate-restricted replicative adenovirus together with antiangiogenic therapy has more potent antitumor effects and advantages than single prostate-restricted replicative adenovirus and deserves more extensive investigation.

Angiogenesis-associated protein annexin II in breast cancer: selective expression in invasive breast cancer and contribution to tumor invasion and progression

Many advanced human tumors including breast cancer overproduce plasmin that is known to promote angiogenesis and metastasis. The mechanism of this effect is poorly understood. Here we report that annexin II, an endothelial co-receptor for tPA (tissue-type plasminogen activator) and plasminogen, was undetectable in normal and hyperplastic ductal epithelial cells and ductal complexes. By contrast, it was consistently expressed in invasive breast cancer and ductal carcinoma in situ (DCIS) indicating its involvement in breast cancer. Using the well established invasive/metastatic MDA-MB231 cell line and the noninvasive/nonmetastatic MCF-7 human breast cancer cell line, we investigated the mechanism by which annexin II regulates breast cancer progression and metastasis. Western and Northern blot analyses demonstrate selective expression of annexin II in MDA-MB231 cells but not in poorly invasive MCF-7 cells suggesting its participation in invasive breast cancer. Since annexin II is a receptor for plasminogen, we tested whether MDA-MB231 cells are capable of producing plasmin in vitro. MDA-MB231 cell membranes induced plasmin generation in a time-dependent manner while those from MCF-7 cells failed to convert plasminogen to plasmin. The generated plasmin is capable of degrading ECM consequently facilitating cell invasion and migration, biological functions required for angiogenesis and metastasis. Plasmin generation and its dependent invasion and migration can be blocked by a monoclonal antibody to annexin II or angiostatin, potent inhibitors of angiogenesis, breast cancer, and metastasis. Our findings indicate that annexin II-dependent localized plasmin generation by human breast cancer cells could contribute to angiogenesis and metastasis. These results suggest that annexin II may be an attractive target for new anti-angiogenic and anti-breast cancer therapies.

Suppression of angiogenesis, tumor growth, and metastasis by adenovirus-mediated gene transfer of human angiotensinogen

Angiogenesis is essential for tumor growth and metastatic dissemination. We have previously shown that human angiotensinogen (AGT) can in vitro inhibit endothelial cell proliferation and migration, capillary-like tube formation, and neovascularization. To determine whether AGT can exert an antitumoral effect through its antiangiogenic properties, we constructed a recombinant adenovirus carrying the human angiotensinogen gene under the control of the cytomegalovirus promoter (AdAGT). In vitro studies showed that AdAGT selectively inhibited endothelial cell proliferation. In vivo, injections of AdAGT into preestablished human MDA-MB-231 mammary carcinomas in nude mice inhibited tumor growth by 70% compared to controls, with 21% total regression. This effect was associated with the suppression of intratumoral vascularization and marked necrosis. Furthermore, in vitroAdAGT infection of MDA-MB-231 and murine melanoma B16F10 cells strongly blocked their in vivo tumorigenicity. Then, in mice expressing high levels of AGT (i.e., either iv injected with AdAGT or HuAGT transgenic mice), the number of B16F10 pulmonary metastases was 85% lower than in control C57BL/6 mice. Our data demonstrate that AGT is a very potent antiangiogenic factor in vivo, independent of angiotensin II generation. Its delivery by gene transfer represents a promising new strategy to block primary tumor growth and to prevent metastasis.

Inhibition of angiogenesis and tumor progression by hydrodynamic cotransfection of angiostatin K1-3, endostatin, and saxatilin genes

In vivo expression of angiostatin and endostatin, two different types of endothelial cell growth inhibitor, have been reported to inhibit vascularization in tumor tissues, resulting in tumor growth inhibition. Recently, in vivo expression of saxatilin, a novel disintegrin purified from snake (Gloydius saxatilis) venom, was able to strongly inhibit endothelial cell proliferation and smooth muscle cell migration, resulting in tumor growth inhibition. However, the antitumor efficacy of the individual antiangiogenic molecules expressed in vivo was not sufficiently potent to induce tumor regression in animal models. Therefore, in this study, we have systemically examined how combinational transfer of angiostatin, endostatin, and saxatilin genes affects neovascularization in tumor tissues and tumor progression in a mouse model. In Matrigel-implanted mice, cotransfection with plasmids encoding angiostatin K1-3 (pFLAG-Angio K1/3), endostatin (pFLAG-Endo), and saxatilin (pFLAG-Sax) resulted in the most effective inhibition of angiogenesis. In addition, hydrodynamic cotransfection of the three genes induced more inhibition of B16BL6 melanoma growth and pulmonary metastasis than other combinations of transfected genes. Compared with the empty vector-treated control group, cotreatment with the three plasmids reduced B16BL6 tumor growth by 89% and pulmonary metastasis by 90%. These results provide additional evidence supporting the combined systemic expression of antiangiogenic factors, such as angiostatin K1-3, endostatin, and saxatilin, as an alternative procedure for antiangiogenic cancer therapy.

Recombinant human prothrombin kringle-2 induces bovine capillary endothelial cell cycle arrest at G0-G1 phase through inhibition of cyclin D1/CDK4 complex: modulation of reactive oxygen species generation and up-regulation of cyclin-dependent kinase inhibitors

Prothrombin is a plasma glycoprotein involved in blood coagulation and, as we have previously reported, prothrombin kringles inhibit BCE (bovine capillary endothelial) cell proliferation. To reveal the mechanism, we investigated the influence of rk-2 (recombinant human prothrombin kringle-2) on the BCE cell cycle progression and ROS (reactive oxygen species) generation using FACS (fluorescence-activated cell sorter) analysis. Cell cycle analysis showed a decrease of G(1) phase cells in cells treated with bFGF (basic fibroblast growth factor) and an increase in cells treated with rk-2, as compared with the control cells. But, the portion of the S phase was reversed. In Western blot analysis, bFGF induced cytoplasmic translocation of p21(Waf1/Cip1) and p27(Kip1) and phosphorylation of p27(Kip1) but rk-2 treatment inhibited translocation of p21(Waf1/Cip1) and p27(Kip1) from nucleus to cytoplasm and phosphorylation of p27(Kip1). Also, rk-2 induced up-regulation of p53 and nuclear p21(Waf1/Cip1) and inhibited the cyclin D1/CDK4 (cyclin-dependent kinase 4) complex. The ROS level of rk-2-treated BCE cells was increased 2-fold when compared with the control, but treatment with NAC (N-Acetyl-L: -cysteine), an anti-oxidant, decreased ROS generation about 55% as compared with the rk-2 treatment. NAC treatment also restored cell cycle progression inhibited by rk-2 and down-regulated p53 and nuclear p21(Waf1/Cip1) expression induced by rk-2.These data suggest that rk-2 induces the BCE cell cycle arrest at G(0)-G(1) phase through inhibition of the cyclin D1/CDK4 complex caused by increase of ROS generation and nuclear cyclin-dependent kinase inhibitors.

Corneal angiogenic privilege: angiogenic and antiangiogenic factors in corneal avascularity, vasculogenesis, and wound healing (an American Ophthalmological Society thesis)

PURPOSE

To determine the molecular basis of corneal avascularity during wound healing and determine the role of angiogenic and antiangiogenic factors in corneal vasculogenesis.

METHODS

The expression of proangiogenic factors (vascular endothelial growth factor [VEGF]; basic fibroblast growth factor [bFGF]; matrix metalloproteinase-2 [MMP-2]; and membrane-type 1-MMP [MT1-MMP]) and antiangiogenic factors (pigment epithelium-derived factor [PEDF]; angiostatin; restin; and endostatin) was analyzed in avascular corneas and in models of corneal neovascularization (bFGF pellet implantation, intrastromal injection of MT1-MMP cDNA, and surgically induced partial limbal deficiency).

RESULTS

Immunohistochemistry demonstrated the presence of antiangiogenic factors (PEDF, angiostatin, restin, and endostatin) and proangiogenic molecules (VEGF, bFGF, MMP-2, and MT1-MMP) in the cornea after wounding. Proangiogenic MMPs were upregulated in stromal fibroblasts in the vicinity of invading vessels following bFGF pellet implantation. Corneal neovascularization (NV) was also induced by intrastromal injection of MT1-MMP naked cDNA in conjunction with de-epithelialization. Partial limbal deficiency (HLD-) resulted in corneal NV in MMP-7 and MMP-3 knockout mice but not in wild type controls.

CONCLUSIONS

Corneal angiogenic privilege is an active process involving the production of antiangiogenic factors to counterbalance the proangiogenic factors (which are upregulated after wound healing even in the absence of new vessels). Our finding that the potent antiangiogenic factors, angiostatin and endostatin, are colocalized with several MMPs during wound healing suggests that MMPs may be involved in the elaboration of these antiangiogenic molecules by proteolytic processing of substrates within the cornea.

Adenoviral vectors expressing human endostatin-angiostatin and soluble Tie2: enhanced suppression of tumor growth and antiangiogenic effects in a prostate tumor model

Angiogenesis is essential for prostate cancer development and metastasis. Antiangiogenic therapy targeting tumor neovasculature, therefore, represents a promising approach for prostate cancer treatment. We hypothesized that adenoviral-mediated delivery of a combination of antiangiogenic factors might have an enhanced antitumor response. We developed the adenoviral vectors Ad-hEndo-angio, expressing a unique, chimeric human endostatin-angiostatin fusion protein, and Ad-sTie2, expressing a soluble form of endothelium-specific receptor tyrosine kinase Tie2. Matrigel angiogenesis assays using Ad-hEndo-angio revealed significant inhibition of tubular network formation and endothelial sprouting compared to Ad-sTie2. In vivo studies in a bilateral PC-3 tumor xenograft model following either intratumoral or systemic administration of Ad-hEndo-angio led to enhanced tumor growth suppression compared to Ad-sTie2. A novel finding is that an intratumoral, combination therapy employing one-half the dose of Ad-hEndo-angio as well as Ad-sTie2 led to a complete regression of the injected, as well as the contralateral uninjected, tumor and prolonged the tumor-free survival in 80% of the animals. In addition, a novel, real-time, intravital imaging modality was used to monitor antiangiogenic responses following adenoviral-mediated gene transfer. These results suggest that a combinatorial antiangiogenic gene therapy approach involving Ad-hEndo-angio and Ad-sTie2 could become a novel form of treatment for localized human prostate cancer.