Inhibition of tumor angiogenesis by angiostatin: from recombinant protein to gene therapy

IL10-modified Human Mesenchymal Stem Cells inhibit Pancreatic Cancer growth through Angiogenesis Inhibition

In the present study, we constructed the recombinant plasmid IL10-PEGFP-C1 and successfully transfected into human mesenchymal stem cells. After culturing for 72 h, the levels of IL6 and TNF-α in the supernatant of the MSCs-IL10 group were significantly lower than the vector group and the control group (17.6 ± 0.68vs73.8 ± 0.8 and 74.4 ± 1.5) µg/L and (65.05 ± 3.8 vs 203.2 ± 2.4 and 201.3 ± 3.7) µg/L, respectively (p < 0.001) .The animal experiments showed that the volume of subcutaneous tumors in the MSCs-IL10 group in vivo was a significantly less level compared to that in MSC control and the blank control groups (76.84 ± 20.11) mm³ vs (518. 344 ± 48.66) mm³, (576.99± 49.88) mm³, (P < 0. 05) and they have a longer life time. Further we found the mass concentrations of IL6 and TNF-α in the blood serum of MSC-IL10 group were lower than the vector group and the control group (64.42 ± 10.9 vs120.83 ± 15.52 and 122.65 ± 13.71) and (40.05 ± 5.63 vs 126.78 ±1.89 and 105.83 ± 2.16) µg/L respectively (p < 0.001). CD31 immunohistochemistry and alginate encapsulation experiments showed tumor angiogenesis were inhibited in MSCs-IL10 group in comparison to the control and vector group (P < 0.001), FITC-labeled dextran intake was also lower than the other groups (P < 0.01). Collectively, this study suggested IL10 could inhibit the growth of the transplanted tumor in vivo and prolong survival of mice, and the primary mechanism may be the indirect inhibition of pro-inflammatory cytokines IL6 and TNF-α secretion and tumor angiogenesis formation.

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.

Combination of oncolytic herpes simplex viruses armed with angiostatin and IL-12 enhances antitumor efficacy in human glioblastoma models

Oncolytic herpes simplex virus (oHSV) can potentially spread throughout the tumor, reach isolated infiltrating cells, kill them, and deliver anticancer agents. However, the host responds to oHSV by inducing intratumoral infiltration of macrophages that can engulf the virus, limiting the potential of this therapeutic strategy. Hypervascularity is a pathognomonic feature of glioblastoma (GBM) and is a promising therapeutic target. Antiangiogenic treatments have multiple benefits, including the capacity to increase oHSV efficacy by suppressing macrophage extravasation and infiltration into the tumor. Angiostatin is an antiangiogenic polypeptide, and interleukin-12 (IL-12) is an immunostimulatory cytokine with strong antiangiogenic effects. Clinical use of each has been limited by delivery issues and systemic toxicity. We tested a combination treatment strategy using oHSVs expressing angiostatin (G47Δ-mAngio) and IL-12 (G47Δ-mIL12) in two orthotopic human GBM models. Intratumoral injection of G47Δ-mAngio and G47Δ-mIL12 in mice bearing intracranial U87 or tumors derived from glioblastoma stem cells significantly prolonged survival compared to each armed oHSV alone. This was associated with increased antiangiogenesis and virus spread and decreased macrophages. These data support the paradigm of using oHSV expressing different antiangiogenic agents and show for the first time that oHSVs expressing angiostatin and IL-12 can improve efficacy in human GBM models.

Future prospects and challenges of antiangiogenic cancer gene therapy

In 1971 Judah Folkman proposed the concept of antiangiogenesis as a therapeutic target for cancer. More than 30 years later, concept became reality with the approval of the antivascular endothelial growth factor (VEGF) monoclonal antibody bevacizumab as a first-line treatment for metastatic colorectal cancer. Monoclonal antibodies and small molecular drugs are the most widely applied methods for inhibition of angiogenesis. The efficacy of these antiangiogenic modalities has been proven, in both preclinical and clinical settings. Although angiogenesis plays a major role in wound healing, hypoxia, and in the female reproductive cycle, inhibition of angiogenesis seems to be a relatively safe therapeutic option against cancers, and has therefore become a logical arena for a wide range of experimentation. The twentieth century has shown the boom of gene therapy and thus it has been applied also in the antiangiogenic setting. This review summarizes methods to induce antiangiogenic responses with gene therapy and discusses the obstacles and future prospects of antiangiogenic cancer gene therapy.

Ocular angiogenesis: mechanisms and recent advances in therapy

Ocular angiogenesis, the formation of new blood vessels from the existing vascular tree, is an important cause for severe loss of vision. It can occur in a spectrum of ocular disorders such as age-related macular degeneration (AMD), diabetic retinopathy, retinal artery or vein occlusion, and retinopathy of prematurity (ROP). One of the underlying causes of vision loss in proliferative retinal diseases is the increased vascular permeability leading to retinal edema, vascular fragility resulting in hemorrhage, or fibrovascular proliferation with tractional and rhegmatogenous retinal detachment. Pro- and antiangiogenic factors regulate an "angiogenic switch," which when turned on, leads to the pathogenesis of the above ocular diseases. Although neovascularization tends to occur at a relatively late stage in the course of many ocular disorders, it is an attractive target for therapeutic intervention, since it represents a final common pathway in processes that are multifactorial in etiology and is the event that typically leads directly to visual loss. Identification of these angiogenesis regulators has enabled the development of novel therapeutic approaches. In this light, antibodies directed against common markers of neovasculature, expressed in different diseases, may open up a very general and widely applicable approach for diagnostic and therapeutic interventions. Local gene transfer, that is, the intraocular delivery of recombinant viruses carrying genes encoding angiostatic proteins and small interfering RNA (siRNA) against vascular endothelial growth factor (VEGF) and VEGF receptors, offers the possibility of targeted, sustained, and regulatable delivery of angiostatic proteins and other angiogenic regulators to the retina. Recent progress has enabled the planning of clinical trials of gene therapy for ocular neovascularization.

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.

AAV-HGFK1 and Ad-p53 cocktail therapy prolongs survival of mice with colon cancer

This study tried to evaluate the application of a novel cancer gene therapy using recombinant adeno-associated virus (AAV) carrying the kringle 1 domain of human hepatocyte growth factor (AAV-HGFK1) in combination with recombinant adenovirus carrying p53 gene (Ad-p53). BALB/c and nude mice models of colon cancer were established and the mice were treated with AAV-HGFK1 alone or in combination with Ad-p53. Combination of AAV-HGFK1 and Ad-p53 significantly prolonged the survival of the mice and also significantly inhibited primary and secondary tumor growth. Histochemical examination of the tumors revealed that AAV-HGFK1+Ad-p53 combinatorial treatment not only induced necrosis and apoptosis in the tumors but also suppressed tumor angiogenesis. The antiangiogenesis effect could likely be attributed to the ability of AAV-HGFK1+Ad-p53 viral cocktail to inhibit endothelial cell migration and proliferation. AAV-HGFK1+Ad-p53 also inhibited tumor cell growth in vitro by inhibiting epidermal growth factor receptor phosphorylation. Therefore, AAV-HGFK1+Ad-p53 cocktail therapy has a significantly higher therapeutic effect than AAV-HGFK1 or Ad-p53 alone and is a novel promising gene therapy for colon cancer.

Lipoprotein[a] and cancer: Anti-neoplastic effect besides its cardiovascular potency

While the death rate from cancer has substantially decreased over the past decade, the search for effective and tolerable therapies is a great challenge as yet. The evidence that malignant cells cannot grow to a clinically detectable tumor mass and spread in the absence of an adequate vascular support, has opened a new area of research towards the selective inhibition or even destruction of tumor vessels. Angiostatin and angiostatin-related proteins are a family of specific angiogenesis inhibitors produced by tumors from a family of naturally occurring proteins, which also includes plasminogen and lipoprotein[a]. The anti-angiogenic activity of these proteins resides in cryptic and highly-repetitive molecular domains hidden within the protein moiety, called kringles. Lipoprotein[a] is an intriguing molecule consisting of a low-density lipoprotein core in addition to the covalently bound apolipoprotein[a]. Apolipoprotein[a] is characterized by an inactive protease domain, a single copy of the plasminogen kringle V and multiple repeats of domains homologous to the plasminogen kringle IV. Reliable studies on animal models indicate that the proteolytic break-down products of apolipoprotein[a] would posses anti-angiogenic and anti-tumoral properties both in vitro and in vivo, a premise to develop novel therapeutic modalities which may efficiently suppress tumor growth and metastasis. This review is focused on the biochemical structure, metabolism and the anti-angiogenic activity of this unique and elusive kringle-containing lipoprotein.

Anti-angiogenesis and anti-tumor activity of recombinant anginex

Anginex, a synthetic 33-mer angiostatic peptide, specifically inhibits vascular endothelial cell proliferation and migration along with induction of apoptosis in endothelial cells. Here we report on the in vivo characterization of recombinant anginex and use of the artificial anginex gene for gene therapy approaches. Tumor growth of human MA148 ovarian carcinoma in athymic mice was inhibited by 80% when treated with recombinant anginex. Histological analysis of the tumors showed an approximate 2.5-fold reduction of microvessel density, suggesting that angiogenesis inhibition is the cause of the anti-tumor effect. Furthermore, there was a significant correlation between the gene expression patterns of 16 angiogenesis-related factors after treatment with both recombinant and synthetic anginex. To validate the applicability of the anginex gene for gene therapy, stable transfectants of murine B16F10 melanoma cells expressing recombinant anginex were made. Supernatants of these cells inhibited endothelial cell proliferation in vitro. Furthermore, after subcutaneous injection of these cells in C57BL/6 mice, an extensive delay in tumor growth was observed. These data show that the artificial anginex gene can be used to produce a recombinant protein with similar activity as its synthetic counterpart and that the gene can be applied in gene therapy approaches for cancer treatment.

Effects of the angiogenesis inhibitor angiostatin on the growth of CC531 colon carcinoma cells in vitro and in a laparoscopic animal model of peritoneal carcinomatosis

BACKGROUND

As angiogenesis is one of the key steps in tumor growth, invasion, and metastasis, antiangiogenic therapy is supposed to be an attractive approach for antitumor treatment. We investigated the cytotoxic, anti-adhesive, and anti-invasive effects of angiostatin in vitro and on intraperitoneal tumor growth in a laparoscopic rat model of peritoneal carcinomatosis using CC531 colon adenocarcinoma cells.

METHODS

The in vitro adhesion and cytotoxicity assays were performed with microtiter plates, and the invasion assay with Transwell dual chambers. Normal saline was used as control. In in vivo experiments, CC531 adenocarcinoma cells were intraperitoneally given to Wistar Albino Glaxo rats after the establishment of a pneumoperitoneum. The animals received angiostatin in different doses intraperitoneally, and in some, angiostatin was additionally administered subcutaneously. Saline was used as control. After 21 days, the animals were euthanized to determine the intra-abdominal tumor weight.

RESULTS

In in vitro experiments, there was no effect of angiostatin on the viability of tumor cells in the cytotoxicity assay, but there was a significant inhibition of tumor cell adhesion and invasion (p<0.05 and p<0.01) in all angiostatin concentrations. In in vivo experiments, an intraperitoneal application of 20 microg angiostatin, but not 10 microg, significantly (p<0.005) decreased the intraperitoneal tumor weight compared with controls. This effect was most pronounced after the combined intraperitoneal and subcutaneous applications.

CONCLUSION

Angiostatin given intraperitoneally at a dose of 20 microg alone or in combination with subcutaneous application significantly diminishes intraperitoneal tumor growth in rats undergoing laparoscopy. This may offer additional therapeutic options for patients undergoing laparoscopic surgery for colorectal cancer.

The antiangiogenic tissue kallikrein pattern of endothelial cells in systemic sclerosis

OBJECTIVE

Postnatal angiogenesis relies on a proper response of endothelial cells to angiogenic stimuli. In systemic sclerosis (SSc), endothelial cells are unresponsive to angiogenic factors. Since circumstantial and experimental evidence points to tissue kallikreins as powerful effectors of the angiogenic response, we undertook this study to investigate the kallikrein pattern of normal and SSc endothelial cells in order to identify differences that can account for defective angiogenesis.

METHODS

Expression of 14 tissue kallikreins was studied by a microarray approach, by reverse transcription-polymerase chain reaction, and by Western blotting in endothelial cells isolated from the skin of clinically healthy subjects and SSc patients. Cell proliferation was quantified by direct cell counting. Invasion and capillary morphogenesis were evaluated in a Boyden chamber and in culture flasks layered with Matrigel. Cyclic nucleotide production was measured by enzyme immunoassay. MAP kinase and ERK activation were measured by Western blotting.

RESULTS

Endothelial cells from SSc patients showed poor expression of kallikreins 9, 11, and 12 compared with endothelial cells from normal subjects. Antibodies against the relevant kallikreins on normal endothelial cells revealed that while kallikreins 9, 11, and 12 induced cell growth, only kallikrein 12 regulated invasion and capillary morphogenesis. Buffering of kallikrein 12 with antibodies resulted in the acquisition of an SSc-like pattern by normal cells in in vitro angiogenesis. Reduction of cAMP and cGMP production and of ERK phosphorylation upon administration of antikallikrein antibodies revealed that the activity of kallikreins 9, 11, and 12 was mediated by kinins.

CONCLUSION

Reduction of tissue kallikreins 9, 11, and 12 may be relevant to reduced angiogenesis in SSc patients.

Antiangiogenic peptides and proteins: from experimental tools to clinical drugs

The formation of a 'tumor-associated vasculature', a process referred to as tumor angiogenesis, is a stromal reaction essential for tumor progression. Inhibition of tumor angiogenesis suppresses tumor growth in many experimental models, thereby indicating that tumor-associated vasculature may be a relevant target to inhibit tumor progression. Among the antiangiogenic molecules reported to date many are peptides and proteins. They include cytokines, chemokines, antibodies to vascular growth factors and growth factor receptors, soluble receptors, fragments derived from extracellular matrix proteins and small synthetic peptides. The polypeptide tumor necrosis factor (TNF, Beromun) was the first drug registered for the regional treatment of human cancer, whose mechanisms of action involved selective disruption of the tumor vasculature. More recently, bevacizumab (Avastin), an antibody against vascular endothelial growth factor (VEGF)-A, was approved as the first systemic antiangiogenic drug that had a significant impact on the survival of patients with advanced colorectal cancer, in combination with chemotherapy. Several additional peptides and antibodies with antiangiogenic activity are currently tested in clinical trials for their therapeutic efficacy. Thus, peptides, polypeptides and antibodies are emerging as leading molecules among the plethora of compounds with antiangiogenic activity. In this article, we will review some of these molecules and discuss their mechanism of action and their potential therapeutic use as anticancer agents in humans.

Characterization and biological activities of recombinant human plasminogen kringle 1-3 produced in Escherichia coli

Angiogenesis, the formation of new capillaries from preexisting blood vessels, is involved in many pathological conditions, for example, tumorigenesis, diabetic retinopathy, and rheumatoid arthritis. Angiostatin, which contains the kringle 1-4 domains of plasminogen, is known to be a potent inhibitor of angiogenesis and a strong suppressor of various solid tumors. In this study, we expressed recombinant protein containing the kringle 1-3 domains of human plasminogen in Escherichia coli and investigated its biological activities. The protein was successfully refolded from inclusion bodies and purified at a 30% overall yield, as a single peak by HPLC. The purified recombinant protein had biochemical properties that were similar to those of the native form, which included molecular size, lysine-binding capacity, and immunoreactivity with a specific antibody. The recombinant protein was also found to strongly inhibit the proliferation of bovine capillary endothelial cells in vitro, and the formation of new capillaries on chick embryos. In addition, it suppressed the growth of primary Lewis lung carcinoma and B16 melanoma in an in vivo mouse model. Our findings suggest that the recombinant kringle 1-3 domains in a prokaryote expression system have anti-angiogenic activities, which may be useful in clinical and basic research in the field of angiogenesis.

Revisiting immunosurveillance and immunostimulation: Implications for cancer immunotherapy

Experimental and clinical experience demonstrates that the resolution of a pathogenic challenge depends not only on the presence or absence of an immune reaction, but also on the initiation of the proper type of immune reaction. The initiation of a non-protective type of immune reaction will not only result in a lack of protection, but may also exacerbate the underlying condition. For example, in cancer, constituents of the immune system have been shown to augment tumor proliferation, angiogenesis, and metastases. This review discusses the duality of the role of the immune system in cancer, from the theories of immunosurveillance and immunostimulation to current studies, which illustrate that the immune system has both a protective role and a tumor-promoting role in neoplasia. The potential of using chemotherapy to inhibit a tumor-promoting immune reaction is also discussed.

Expression of human apolipoprotein(a) kringles in colon cancer cells suppresses angiogenesis-dependent tumor growth and peritoneal dissemination

BACKGROUND

Anti-angiogenesis therapy has been regarded as a promising treatment of cancer based on the fact that most tumors and their metastasis are angiogenesis-dependent. Gene therapy can potentially expand the horizons of tumor angiogenesis therapy by virtue of its ability to produce high concentrations of therapeutic agents in a local area for a sustained period. The present study was performed to evaluate the therapeutic potential of gene therapy for the treatment of cancer and metastasis.

METHODS

The murine colon carcinoma cell line CT26 was manipulated ex vivo to express an anti-angiogenic molecule, LK68, consisting of human apolipoprotein(a) kringle domains, KIV(9)-KIV(10)-KV, using retrovirus-mediated gene transfer. Its effects on colon tumor growth and metastasis were evaluated in experimental animal models established by injecting LK68-expressing and control CT26 cells subcutaneously or into the peritoneal cavity of BALB/c mice, respectively.

RESULTS

Expression of LK68 significantly suppressed colon tumor growth in mice, but did not influence the growth of tumor cells in vitro. Immunohistochemical analysis of tumor tissues revealed a significant reduction in microvessel density in LK68-expressing tumors. Thus, the suppression of tumor growth appears to result mainly from inhibition of tumor angiogenesis. This decrease in vessel density is correlated with a notable increase in tumor cell apoptosis in vivo, but has no influence on proliferation. Moreover, expression of LK68 prevents peritoneal dissemination, and consequently improves overall host survival.

CONCLUSIONS

These results collectively indicate that a gene therapy strategy using LK68 cDNA is useful for the treatment for both colon tumor growth and peritoneal dissemination.

Suppression of Colorectal Cancer Liver Metastasis and Extension of Survival by Expression of Apolipoprotein(a) Kringles

The formation of hepatic metastases in colorectal cancer is the main cause of patient death. Current therapies directed at hepatic metastasis of colorectal cancer have had minimal impact on outcome. Therefore, alternative treatment strategies for liver metastasis require development. The present study was performed to evaluate the application of cDNA of LK68 encoding apolipoprotein(a) kringles IV-9, IV-10, and V as possible candidates for gene therapy treatment of this life-threatening disease. The murine colorectal cancer cell line CT26 was transduced ex vivo with LK68 cDNA via retroviral gene transfer, and an experimental model of hepatic metastasis was established by injecting LK68-expressing and control cells into the spleens of BALB/c mice. Expression of LK68 did not affect the growth characteristics and viability of transduced CT26 cells in vitro. LK68 produced from CT26 cells substantially inhibited the migration of endothelial cells in vitro. In vivo, substantial suppression of liver metastasis and prolonged survival were observed in mice bearing LK68-expressing CT26 cells, compared with controls. LK68-expressing liver metastases were restricted to smaller sizes and displayed decreased microvessel density and increased tumor cell apoptosis. Our data collectively indicate that LK68 suppresses angiogenesis-dependent progression of prevascular micrometastases to macroscopic tumors and their growth, which are clinically accessible and biologically relevant therapeutic targets. We propose that antiangiogenic gene therapy with LK68 is a promising strategy for the treatment of colorectal cancer liver metastasis.

Dose-dependent neovascularization-promoting effect of adenovirus vector CI-1023 in a rat hindlimb ischaemic model

CI-1023 (AdGVVEGF121.10) is a replication-deficient adenovirus vector (complete E1a-, partial E1b-, partial E3-) delivering human vascular endothelial growth factor-121 gene. Previous studies from this group have established that CI-1023 can successfully transfer human vascular endothelial growth factor-121 gene resulting in local tissue expression of vascular endothelial growth factor protein. The purpose of this study was to evaluate neovascularization-promoting potency and efficacy of CI-1023 in a wide dose range. In a rat hindlimb ischaemic model, we measured neovascularization-promoting effect of CI-1023 using three end-points: post mortem angiography, immuno-histochemistry and Laser Doppler scanning of tissue blood perfusion. Neovascularization-promoting activity of CI-1023 over the dose range of 4 x 10(6) pu-4 x 10(10) pu was evaluated. Our data demonstrated an obvious dose-dependent effect between 4 x 10(6) pu-4 x 10(8) pu. The neovascularizing effect is somewhat plateaued at the levels between 4 x 10(8) pu and 4 x 10(10) pu. We conclude CI-1023 is a potent neovascularization-promoting compound, with a dose-dependent effect between 4 x 10(6) pu-4 x 10(8) pu in the rat hindlimb ischaemic model.

The tyrp1-Tag/tyrp1-FGFR1-DN Bigenic Mouse

We describe herein a new transgenic mouse tumor model in which fibroblast growth factor (FGF) receptor activity is selectively inhibited. Tyrp1-Tag mice that develop early vascularized tumors of the retinal pigment epithelium were crossed with tyrp1-FGFR1-DN mice that express dominant-negative FGF receptors in the retinal pigment epithelium to generate bigenic mice. Initial angiogenesis-independent tumor growth progressed equally in tyrp1-Tag and bigenic mice with no significant differences in the number of dividing and apoptotic cells within the tumor. By contrast, at a later stage when tyrp1-Tag tumors rapidly expanded to fill the entire eye posterior chamber and migrate along the optic nerve toward the chiasma, bigenic tumors remained small and were poorly vascularized. Secondary tumors of small size developed in only 20% of bigenic mice by 1 month. Immunohistochemical analysis of secondary tumors from bigenic mice showed a reduction of angiogenesis and an increase in apoptosis in tumor cells. Tumor cells from bigenic mice expressed high levels of truncated FGF receptors and did not induce endothelial tube formation in vitro. All in all, this indicates that the tyrp1-Tag mouse may be a useful model to study selective tumor inhibition and the effect of antitumor therapy that targets a specific growth factor pathway. FGF receptors are required at the onset of tumor invasion and angiogenesis in ocular tumors and are good therapeutic targets in this model. The bigenic mouse may also constitute a useful model to answer more fundamental questions of cancer biology such as the mechanism of tumor escape.