Molecular targeting of angiogenesis for imaging and therapy

Exosomal miR-423-5p Derived from Cerebrospinal Fluid Pulsation Stress-Stimulated Osteoblasts Improves Angiogenesis of Endothelial Cells via DUSP8/ERK1/2 Signaling Pathway

Exosomes secreted from osteoblasts (OBs) can regulate the angiogenesis of endothelial cells (ECs); however, whether cerebrospinal fluid pulsation (CSFP) stress, a special mechanical stimulation, can influence the cell's communication in the context of angiogenesis remains unknown. In this study, the effect of exosomes derived from CSFP stress-stimulated OBs on facilitating the angiogenesis of ECs was investigated. First, OBs were cultured in a CSFP bioreactor, and exosomes derived from OBs were isolated and identified. Cell Counting Kit 8 assay, transwell migration assay, wound healing migration assay, and tube formation assay were conducted to assess the effects of CSFP stress-stimulated OBs-derived exosomes (CSFP-Exos) on the angiogenesis of ECs. Then high-throughput RNA sequencing was used to determine the miRNA profiles of Non-CSFP stress-stimulated OBs-derived exosomes (NCSFP-Exos) and CSFP-Exos, and the luciferase reporter gene assay was performed to confirm the binging of miR-423-5p to DUSP8. In addition, the Matrigel plug assay was performed to explore whether exosomal miR-423-5p has the same effects in vivo. Our results suggested that CSFP-Exos can promote the angiogenesis of ECs, and miR-423-5p was enriched in CSFP-Exos. Moreover, miR-423-5p could promote the effect of angiogenesis via directly targeting dual-specificity phosphatase 8 (DUSP8), which inhibited the ERK1/2 signaling pathway. In conclusion, exosomal miR-423-5p derived from CSFP stress-stimulated OBs could promote the angiogenesis of ECs by the DUSP8/ERK1/2 signaling pathway.

Targeting of externalized αB-crystallin on irradiated endothelial cells with pro-thrombotic vascular targeting agents: Potential applications for brain arteriovenous malformations

BACKGROUND

Vascular targeting uses molecular markers on the surface of diseased vasculature for ligand-directed drug delivery to induce vessel occlusion or destruction. In the absence of discriminatory markers, such as in brain arteriovenous malformations (AVMs), stereotactic radiosurgery may be used to prime molecular changes on the endothelial surface. This study explored αB-crystallin (CRYAB) as a radiation induced target and pre-tested the specificity and efficacy of a CRYAB-targeting coaguligand for in vitro thrombus induction.

METHODS

A parallel-plate flow system was established to circulate human whole blood over a layer of human brain endothelial cells. A conjugate of anti-CRYAB antibody and thrombin was injected into the circuit to compare binding and thrombus formation on cells with or without prior radiation treatment (0-25 Gy).

RESULTS

Radiation increased CRYAB expression and surface exposure in human brain endothelial cells. In the parallel-plate flow system, the targeted anti-CRYAB-thrombin conjugate increased thrombus formation on the surface of irradiated cells relative to non-irradiated cells and to a non-targeting IgG-thrombin conjugate. Fibrin deposition and accumulation of fibrinogen degradation products increased significantly at radiation doses at or above 15 Gy with conjugate concentrations of 1.25 and 2.5 μg/mL.

CONCLUSIONS

CRYAB exposure can be detected at the surface of human brain endothelial cells in response to irradiation. Pro-thrombotic CRYAB-targeting conjugates can bind under high flow conditions and in the presence of whole blood induce stable thrombus formation with high specificity and efficacy on irradiated surfaces. CRYAB provides a novel radiation marker for potential vascular targeting in irradiated brain AVMs.

Single Photon Emission Computed Tomography Tracer

Single photon emission computed tomography (SPECT) is the state-of-the-art imaging modality in nuclear medicine despite the fact that only a few new SPECT tracers have become available in the past 20 years. Critical for the future success of SPECT is the design of new and specific tracers for the detection, localization, and staging of a disease and for monitoring therapy. The utility of SPECT imaging to address oncologic questions is dependent on radiotracers that ideally exhibit excellent tissue penetration, high affinity to the tumor-associated target structure, specific uptake and retention in the malignant lesions, and rapid clearance from non-targeted tissues and organs. In general, a target-specific SPECT radiopharmaceutical can be divided into two main parts: a targeting biomolecule (e.g., peptide, antibody fragment) and a γ-radiation-emitting radionuclide (e.g., ^99mTc, ¹²³I). If radiometals are used as the radiation source, a bifunctional chelator is needed to link the radioisotope to the targeting entity. In a rational SPECT tracer design, these single components have to be critically evaluated in order to achieve a balance among the demands for adequate target binding, and a rapid clearance of the radiotracer. The focus of this chapter is to depict recent developments of tumor-targeted SPECT radiotracers for imaging of cancer diseases. Possibilities for optimization of tracer design and potential causes for design failure are discussed and highlighted with selected examples.

Peripheral artery disease: the new frontiers of imaging techniques to evaluate the evolution of regenerative medicine

Introduction: Stem cells (ESC, iPSC, MSC) are known to have intrinsic regenerative properties. In the last decades numerous findings have favored the development of innovative therapeutic protocols based on the use of stem cells (Regenerative Medicine/Cell Therapy) for the treatment of numerous diseases including PAD, with promising results in preclinical studies. So far, several clinical studies have shown a general improvement of the patient's clinical outcome, however they possess many critical issues caused by the non-randomized design of the limited number of patients examined, the type cells to be used, their dosage, the short duration of treatment and also their delivery strategy. Areas covered: In this context, the use of the most advanced molecular imaging techniques will allow the visualization of very important physio-pathological processes otherwise invisible with conventional techniques, such as angiogenesis, also providing important structural and functional data. Expert opinion: The new frontier of cell therapy applied to PAD, potentially able to stop or even the process that causes the disease, with particular emphasis on the clinical aspects that different types of cells involve and on the use of more innovative molecular imaging techniques now available.

Immunoscintigraphy of patients with head and neck carcinomas, with an anti-angiogenetic antibody fragment

Objective

In a phase I/II clinical study, we investigated tumor targeting in patients with head and neck squamous cell carcinomas (SCC), using an antibody directed against the extra-domain-B of fibronectin (EDB), a marker of angiogenesis and tissue remodeling.

Study Design And Setting

Five patients with SCC were injected with the 123-iodine-radiolabeled L19(scFv)2 antibody and underwent scintigraphic detection with single photon emission tomography with computerized tomography (SPECT/CT). In addition, 18 F-fluorodeoxyglucose ( 18 FDG) positron emission tomography with computerized tomography (PET/CT) was performed.

Results

Successful targeting of the primary tumor could be achieved in 4 of 5 patients and was comparable to PET imaging. No side effects were observed.

Conclusions

Tumor targeting with the L19(scFv)2 antibody is also feasible for head and neck SCC.

Significance

These results may serve as a base for future therapeutical applications in human beings, with modified versions of the L19(scFv)2 antibody, designed to selectively deliver bioactive molecules into malignant tumors.

Design and evaluation of radiolabeled tracers for tumor imaging

The growing understanding of tumor biology and the identification of tumor-specific genetic and molecular alterations, such as the overexpression of membrane receptors and other proteins, allows for personalization of patient management using targeted therapies. However, this puts stringent demands on the diagnostic tools used to identify patients who are likely to respond to a particular treatment. Radionuclide molecular imaging is a promising noninvasive method to visualize and characterize the expression of such targets. A number of different proteins, from full-length antibodies and their derivatives to small scaffold proteins and peptide receptor-ligands, have been applied to molecular imaging, each demonstrating strengths and weaknesses. Here, we discuss the concept of molecular targeting and, in particular, molecular imaging of cancer-associated targets. Additionally, we describe important biotechnological considerations and desired features when designing and developing tracers for radionuclide molecular imaging.

Synthesis and application of cNGR-containing imaging agents for detection of angiogenesis

Angiogenesis is a multi-step process regulated by pro- and anti-angiogenic factors. Inhibition of angiogenesis is a potential anti cancer treatment strategy that is now investigated clinically. In addition, advances in the understanding of the angiogenic process have led to the development of new angiogenesis therapies for ischemic heart disease. Currently, researchers search for objective measures that indicate pharmacological responses to pro- and anti-angiogenic drugs and therefore, there is a great interest in techniques to visualize angiogenesis noninvasively. As CD13 is selectively expressed in angiogenic blood vessels, it can serve as a target for molecular imaging tracers to noninvasively visualize angiogenic processes in animal models and patients. Here, an overview on the currently used CD13 targeted molecular imaging probes for noninvasive visualization of angiogenesis is given.

Single photon emission computed tomography tracer

Single photon emission computed tomography (SPECT) is the state-of-the-art imaging modality in nuclear medicine despite the fact that only a few new SPECT tracers have become available in the past 20 years. Critical for the future success of SPECT is the design of new and specific tracers for the detection, localization, and staging of a disease and for monitoring therapy. The utility of SPECT imaging to address oncologic questions is dependent on radiotracers that ideally exhibit excellent tissue penetration, high affinity to the tumor-associated target structure, specific uptake and retention in the malignant lesions, and rapid clearance from non-targeted tissues and organs. In general, a target-specific SPECT radiopharmaceutical can be divided into two main parts: a targeting biomolecule (e.g. peptide, antibody fragment) and a γ-radiation emitting radionuclide (e.g. (99m)Tc, (123)I). If radiometals are used as the radiation source, a bifunctional chelator is needed to link the radioisotope to the targeting entity. In a rational SPECT tracer design these single components have to be critically evaluated in order to achieve a balance among the demands for adequate target binding, and a rapid clearance of the radiotracer. The focus of this chapter is to depict recent developments of tumor-targeted SPECT radiotracers for imaging of cancer diseases. Possibilities for optimization of tracer design and potential causes for design failure are discussed and highlighted with selected examples.

Inhibitory effects of SY0916, a platelet-activating factor receptor antagonist, on the angiogenesis of human umbilical vascular endothelial cells

SY0916 is a novel platelet-activating factor receptor antagonist. The objective of this study is to explore the anti-angiogenesis effects of SY0916 on human umbilical vascular endothelial cell (HUVEC) and to understand its possible mechanism. The effect of SY0916 on proliferation of HUVEC was measured by the MTT method, whereas the effect of SY0916 on HUVEC chemotaxis was carried out by Boyden chamber assay. The activities of metalloproteinase (MMP)-9 and MMP-2 were detected using gelatin zymography, and the expression of intercellular adhesion molecules-1 (ICAM-1) was measured by Western blot analysis. The 2D tube formation experiment of HUVEC with 10% fetal calf serum on Matrigel was also evaluated. It was shown that SY0916 had significant inhibitory effects on the proliferation and the chemotaxis of HUVEC induced by phorbol-12-myristate-13-acetate in a positive dose-dependent manner. Furthermore, SY0916 could significantly suppress the activity of MMP-2 and MMP-9 and decrease the expression of ICAM-1 in HUVEC. In 2D tube formation test, SY0916 could effectively inhibit the formation of vascular structure on Matrigel. The results showed that SY0916 could block the chemotaxis of HUVEC, and then inhibit the tube formation on Matrigel. Such anti-angiogenesis effect of SY0916 on HUVEC might relate to downregulate the expressions of MMP-2, MMP-9, and ICAM-1.

Concomitant vascular GRP-receptor and VEGF-receptor expression in human tumors: molecular basis for dual targeting of tumoral vasculature

Gastrin-releasing peptide (GRP) and GRP receptors (GRPR) play a role in tumor angiogenesis. Recently, GRPR were found to be frequently expressed in the vasculature of a large variety of human cancers. Here, we characterize these GRPR by comparing the vascular GRPR expression and localization in a selection of human cancers with that of an established biological marker of neoangiogenesis, the vascular endothelial growth factor (VEGF) receptor. In vitro quantitative receptor autoradiography was performed in parallel for GRPR and VEGF receptors (VEGFR) in 32 human tumors of various origins, using ¹²⁵I-Tyr-bombesin and ¹²⁵I-VEGF₁₆₅ as radioligands, respectively. Moreover, VEGFR-2 was evaluated immunohistochemically. All tumors expressed GRPR and VEGFR in their vascular system. VEGFR were expressed in the endothelium in the majority of the vessels. GRPR were expressed in a subpopulation of vessels, preferably in their muscular coat. The vessels expressing GRPR were all VEGFR-positive whereas the VEGFR-expressing vessels were not all GRPR-positive. GRPR expressing vessels were found immunohistochemically to co-express VEGFR-2. Remarkably, the density of vascular GRPR was much higher than that of VEGFR. The concomitant expression of GRPR with VEGFR appears to be a frequent phenomenon in many human cancers. The GRPR, localized and expressed in extremely high density in a subgroup of vessels, may function as target for antiangiogenic tumor therapy or angiodestructive targeted radiotherapy with radiolabeled bombesin analogs alone, or preferably together with VEGFR targeted therapy.

PET and PET/CT for unknown primary tumors

Carcinoma of unknown primary (CUP) is defined as histologically proven metastatic disease that, after a complete diagnostic work-up, yields no primary detectable tumor. CUP is one of the ten most frequent cancers, with overall poor outcome. Detection of the unknown primary tumor is of crucial importance in this scenario, since it might help to select and offer definitive treatment, which, in turn, may improve patient prognosis. Additional diagnostic work-up, usually consisting of a combination of several radiological and endoscopic investigations and serum tumor marker studies, can be time consuming, expensive, and pose a significant burden to the patient. The final diagnostic yield of these tests is often limited. Combined positron emission tomography/computed tomography (PET/CT), using the radiotracer (18)F-fluoro-2-deoxyglucose (FDG), may be of great value in the management of patients with CUP for the detection of primary tumors. This chapter gives a brief introduction to the syndrome of CUP, followed by an outline of the rationale, use, and utility of FDG-PET/CT in CUP, and concludes with a discussion on the challenges and future directions in the diagnostic management of patients with CUP.

MR reporter gene imaging of endostatin expression and therapy

PURPOSE

The aim of this study is to monitor endostatin gene expression and therapy using transferrin receptor (TfR) as reporter gene and transferrin conjugate of ultrasmall supramagnetic iron oxide nanoparticle (Tf-USPIO) as magnetic resonance (MR) reporter probe.

PROCEDURE

A retroviral plasmid (pLP-LNCX) encoding mouse endostatin and TfR was constructed, and packaged with a titer of 4 × 10(7)colony-forming units per millimeter. MDA-MB-231 breast tumors were established in BALB/c mice by subcutaneous injection of 2 × 10(6) MDA-MB-231 cells. Mice were intratumorally injected with recombinant retrovirus and imaged with MR using Tf-USPIO. Western blot, Prussian blue, and immunohistochemical staining were performed to validate the magnetic resonance imaging results. The antitumor effect of retro-endostatin (ES)-TfR was also evaluated by intratumoral injection of the viral vector.

RESULTS

The expression of both endostatin and TfR genes in MDA-MB-231 cells after retroviral transfection was confirmed by Western blot and flow cytometry. Tf-USPIO conjugate binds specifically to cells stably transfected with retro-ES-TfR. After intravenous injection of the Tf-USPIO conjugate, there was a more pronounced decrease in T2 relaxation time in tumors treated with retro-ES-TfR than in tumors treated with empty retrovirus retro-LNCX. The expression of ES gene significantly delayed the growth of MDA-MB-231 tumor and reduction of microvessel density and VEGF level as compared to those without viral transfection or transfected with empty retro-LNCX vector.

CONCLUSIONS

Endostatin therapeutic gene expression was visualized successfully using TfR reporter gene and Tf-USPIO MR reporter probe, which indicates that MR reporter gene imaging may be valuable in gene therapy to evaluate therapeutic gene expression and treatment efficacy.

PET and SPECT in cardiovascular molecular imaging

The current focus of cardiovascular medicine is on early detection and prevention of disease, to control the escalating costs of health care. To achieve this goal, novel imaging approaches that allow for early detection of disease and risk stratification are needed. Traditionally, the diagnosis, monitoring, and prognostication of cardiovascular disease were based on techniques that measured changes in metabolism, blood flow, and biological function. Molecular imaging is emerging as a new tool for the noninvasive detection of biological processes that can differentiate and characterize tissues before manifestation of gross anatomical features or physiological consequences. Leading the way are techniques involving high-sensitivity radiotracers that could revolutionize current diagnostic paradigms. This Review provides an overview of selected molecular-based single photon emission CT (SPECT) and PET imaging strategies for the evaluation of cardiovascular disease-including the evaluation of myocardial metabolism and neurohumoral activity of the heart-and potential future targeted methods of evaluating critical molecular processes, such as atherosclerosis, ventricular remodeling after myocardial infarction, and ischemia-associated angiogenesis.

Molecular imaging using contrast-enhanced ultrasound: evaluation of angiogenesis and cell therapy

The field of regenerative medicine and its applications for cardiovascular diseases continues to grow rapidly, fuelled by the increasing numbers of symptomatic patients who are not candidates for conventional revascularization procedures and remain refractory to maximal medical therapy. Therapeutic angiogenesis, initially in the form of the administration of growth factor protein or gene therapy and, more recently, in the form of adult progenitor cell therapy, has emerged as a promising new method of treatment for patients with ischaemic heart disease and peripheral arterial disease. There is a growing interest in non-invasive imaging techniques to evaluate the response to angiogenic gene-and cell-based therapies. Contrast-enhanced ultrasound (CEU) techniques using site-specific microbubbles have recently been developed for the molecular imaging of the vascular phenotype that characterizes angiogenesis. These methods have now been modified to allow the imaging of progenitor cell engraftment into neovessels. These molecular imaging techniques using contrast ultrasound and targeted microbubbles have the potential to further characterize the angiogenic response, aid in the optimization of gene- and cell-based strategies of therapeutic neovascularization, and ultimately serve to monitor the therapeutic effects in patients enrolled in clinical trials of regenerative therapies. This review will focus specifically on CEU molecular imaging techniques for the evaluation of angiogenesis and cell therapies in cardiovascular diseases, including: (i) an overview of the techniques and results of pre-clinical studies; (ii) a comparison of CEU molecular imaging techniques with other available molecular imaging modalities; and (iii) a discussion of the future role of CEU molecular imaging in the field of regenerative medicine.

Proteomics technologies in endometriosis

Endometriosis is a common disorder that is associated with infertility and pelvic pain. Diagnosis is based on the visualization of endometriotic lesions during surgery as no reliable serum marker is currently available. The etiology of endometriosis is largely unknown. Over the last 20 years, several proteomics technologies have been used to research novel proteins with a potential etiological role in endometriosis, and to identify candidate serum markers for this condition. While some molecules identified by proteomics technologies may have a relevant role in the pathogenesis of endometriosis, the research of potential serum markers for this condition is still far from any clinical application. This review summarizes the state of the art and potential applications of proteomics in endometriosis research.

Ligand-based vascular targeting of disease

This review illustrates the basic principles of ligand-based vascular targeting and presents some of the most advanced results obtained in this field, not only in terms of biopharmaceuticals, which are currently being investigated in clinical and preclinical studies, but also in terms of enabling technologies that facilitate target and ligand discovery. Whereas most of the vascular targeting research activities have so far concentrated on tumoral angiogenesis, the development of non-oncological applications has recently gained momentum and is likely to become an important area of modern pharmaceutical research.

Imaging techniques for the vulnerable coronary plaque

The goal of this article is to illustrate the main invasive and noninvasive diagnostic modalities to image the vulnerable coronary plaque, which is responsible for acute coronary syndrome. The main epidemiologic and histological issues are briefly discussed in order to provide an adequate background. Comprehensive coronary atherosclerosis imaging should involve visualization of the entire coronary artery tree and plaque characterization, including three-dimensional morphology, relationship with the lumen, composition, vascular remodelling and presence of inflammation. No single technique provides such a comprehensive description, and no available modality extensively identifies the vulnerable plaque. In particular, we describe multislice computed tomography, which at present seems to be the most promising noninvasive tool for an exhaustive image-based quantification of coronary atherosclerosis.

Antibody-mediated delivery of IL-10 inhibits the progression of established collagen-induced arthritis

The antibody-mediated targeted delivery of cytokines to sites of disease is a promising avenue for cancer therapy, but it is largely unexplored for the treatment of chronic inflammatory conditions. Using both radioactive and fluorescent techniques, the human monoclonal antibodies L19 and G11 (specific to two markers of angiogenesis that are virtually undetectable in normal adult tissues) were found to selectively localize at arthritic sites in the murine collagen-induced model of rheumatoid arthritis following intravenous (i.v.) administration. The same animal model was used to study the therapeutic action of the L19 antibody fused to the cytokines IL-2, tumour necrosis factor (TNF) and IL-10. Whereas L19-IL-2 and L19-TNF treatment led to increased arthritic scores and paw swellings, the fusion protein L19-IL-10 displayed a therapeutic activity, which was superior to the activity of IL-10 fused to an antibody of irrelevant specificity in the mouse. The anti-inflammatory cytokine IL-10 has been investigated for the treatment of patients with rheumatoid arthritis, but clinical development plans have been discontinued because of a lack of efficacy. Because the antigen recognised by L19 is strongly expressed at sites of arthritis in humans and identical in both mice and humans, it suggests that the fusion protein L19-IL-10 might help overcome some of the clinical limitations of IL-10 and provide a therapeutic benefit to patients with chronic inflammatory disorders, including arthritis.

A human mAb specific to oncofetal fibronectin selectively targets chronic skin inflammation in vivo

The antibody-based targeted delivery of bioactive agents to sites of angiogenesis is an attractive therapeutic strategy for cancer treatment, but is largely unexplored for chronic inflammatory diseases. In this article, we show that the extra domain B (EDB) domain of fibronectin, a marker of angiogenesis, is expressed in psoriatic lesions, and that the anti-EDB human antibody L19 can selectively localize to chronically inflamed skin in vivo. The L19-based delivery of the cytokines IL10 and IL12 did not improve or worsen inflammation in a mouse model of chronic skin inflammation, which overexpressed vascular endothelial growth factor under the control of the keratin-14 promoter. By contrast, the L19-based targeted delivery of the proinflammatory cytokine IL2 or of the photosensitizer Sn(IV) chlorin e6 resulted in an increased swelling and reddening of inflamed skin. These results indicate that antibodies specific to components of the modified extracellular matrix can selectively accumulate at chronically inflamed sites in vivo. This observation now stimulates the search for bioactive molecules which can be fused to antibodies and which may confer a therapeutic benefit as a result of their preferential accumulation in psoriatic lesions and other sites of inflammation.

Antibodies for angiogenesis inhibition, vascular targeting and endothelial cell transcytosis

The endothelium is increasingly recognized as a target for biomedical intervention, not only for its accessibility to molecular agents coming from the blood-stream, but also for the active role played by endothelial cell proliferation to support diseases such as cancer, blinding ocular disorders and chronic inflammatory conditions. The notion that solid tumors cannot grow beyond a size of few millimeters without inducing the proliferation of new blood vessels has stimulated the search for mediators of angiogenesis and for inhibitors of this process, culminating in the approval of a humanized monoclonal antibody to VEGF-A for oncology applications. In parallel, researchers have begun to consider imaging and therapeutic strategies based on the selective delivery of bioactive agents to the new blood vessels, mediated by monoclonal antibody derivatives. Recently, the field of vascular targeting research has been extended to the investigation of molecular agents that may mediate endothelial cell transcytosis, in the hope to overcome this body barrier for drug delivery. This article reviews some of the most significant advances in these areas, and outlines future challenges and opportunities.

Tumor-targeting properties of novel antibodies specific to the large isoform of tenascin-C

BACKGROUND

The targeted delivery of bioactive molecules with antibodies specific to tumor-associated antigens represents a promising strategy for improving the efficacy of tumor therapy. The large isoform of tenascin-C, an abundant glycoprotein of the tumor extracellular matrix, is strongly overexpressed in adult tissue undergoing tissue remodeling, including wound healing and neoplasia, and has been implicated in a variety of different cancers while being virtually undetectable in most normal adult tissues.

EXPERIMENTAL DESIGN

We have used antibody phage technology to generate good-quality human recombinant antibodies (F16 and P12) specific to the alternatively spliced domains A1 and D of the large isoform of tenascin-C. The tumor-targeting properties of F16 and P12 were assessed by biodistribution studies in tumor xenografts using the antibodies in small immunoprotein (SIP) format.

RESULTS

SIP(F16) selectively accumulated at the tumor site with 4.5%ID/g at 24 hours in the U87 glioblastoma model but was rapidly cleared from other organs (tumor-to-organ ratios, approximately 10:1). The accumulation of SIP(P12) in the tumor was lower compared with SIP(F16) and persistent levels of radioactivity were observed in the intestine.

CONCLUSIONS

These data suggest that the F16 antibody, specific to domain A1 of tenascin-C, is a promising building block for the development of antibody-based pharmaceuticals in view of its excellent tumor-targeting performance and the strong expression of the antigen in a variety of primary and metastatic tumors.

Alphastatin downregulates vascular endothelial cells sphingosine kinase activity and suppresses tumor growth in nude mice bearing human gastric cancer xenografts

AIM: To investigate whether alphastatin could inhibit human gastric cancer growth and furthermore whether sphingosine kinase (SPK) activity is involved in this process.

METHODS: Using migration assay, MTT assay and Matrigel assay, the effect of alphastatin on vascular endothelial cells (ECs) was evaluated in vitro. SPK and endothelial differentiation gene (EDG)-1, -3, -5 mRNAs were detected by reverse transcription-polymerase chain reaction (RT-PCR). SPK activity assay was used to evaluate the effect of alphastatin on ECs. Matrigel plug assay in nude mice was used to investigate the effect of alphastatin on angiogenesis in vivo. Female nude mice were subcutaneously implanted with human gastric cancer cells (BGC823) for the tumor xenografts studies. Micro vessel density was analyzed in Factor VIII-stained tumor sections by the immunohistochemical SP method.

RESULTS: In vitro, alphastatin inhibited the migration and tube formation of ECs, but had no effect on proliferation of ECs. RT-PCR analysis demonstrated that ECs expressed SPK and EDG-1, -3, -5 mRNAs. In vivo, alphastatin sufficiently suppressed neovascularization of the tumor in the nude mice. Daily administration of alphastatin produced significant tumor growth suppression. Immunohistochemical studies of tumor tissues revealed decreased micro vessel density in alphastatin-treated animals as compared with controls.

CONCLUSION: Downregulating ECs SPK activity may be one of the mechanisms that alphastatin inhibits gastric cancer angiogenesis. Alphastatin might be a useful and relatively nontoxic adjuvant therapy in the treatment of gastric cancer.

Engineered antibody fragments and the rise of single domains

With 18 monoclonal antibody (mAb) products currently on the market and more than 100 in clinical trials, it is clear that engineered antibodies have come of age as biopharmaceuticals. In fact, by 2008, engineered antibodies are predicted to account for >30% of all revenues in the biotechnology market. Smaller recombinant antibody fragments (for example, classic monovalent antibody fragments (Fab, scFv)) and engineered variants (diabodies, triabodies, minibodies and single-domain antibodies) are now emerging as credible alternatives. These fragments retain the targeting specificity of whole mAbs but can be produced more economically and possess other unique and superior properties for a range of diagnostic and therapeutic applications. Antibody fragments have been forged into multivalent and multi-specific reagents, linked to therapeutic payloads (such as radionuclides, toxins, enzymes, liposomes and viruses) and engineered for enhanced therapeutic efficacy. Recently, single antibody domains have been engineered and selected as targeting reagents against hitherto immunosilent cavities in enzymes, receptors and infectious agents. Single-domain antibodies are anticipated to significantly expand the repertoire of antibody-based reagents against the vast range of novel biomarkers being discovered through proteomics. As this review aims to show, there is tremendous potential for all antibody fragments either as robust diagnostic reagents (for example in biosensors), or as nonimmunogenic in vivo biopharmaceuticals with superior biodistribution and blood clearance properties.

Efficient human interferon-alpha gene transfer to neuroendocrine tumor cells with long-term and stable expression

Interferon (IFN)-alpha has been used in the treatment of neuroendocrine (NE) tumors; however, the feasibility of IFN-alpha gene therapy has not been evaluated in NE tumor cells. In this study, human IFN-alpha2 (hIFN-alpha2) gene has been transferred into a NE tumor cell line BON. hIFN-alpha2-expressing BON cells were subcutaneously inoculated in nude mice. The results demonstrated that hIFN-alpha2 exerted significant antiproliferative effects on NE tumor cell lines (BON and LCC18) and other tumor cell lines (CA46 and SW480) as well as porcine aorta cell line. Furthermore, hIFN-alpha2 demonstrated its antineovascular activity in mice tumor and a direct antiangiogenic effect in chicken chorioallantoic membrane assay. hIFN-alpha2-expressing BON cells had a stable and long-term expression. Mice implanted with hIFN-alpha2-expressing BON cells showed a lower incidence, a delayed development and a significantly longer doubling time of the tumor compared to both wild-type (WT) and vector group. In addition, IFN-alpha significantly inhibited cell adhesion of WT BON cells. hIFN-alpha2-expressing BON tumors had a high level of hIFN-alpha2 protein. Finally, mice implanted with a mixture of WT and hIFN-alpha2-expressing BON cells (1:1) presented a delayed tumor development and had an even lower incidence of tumors than those implanted with hIFN-alpha2-expressing BON cells only. The doubling time of tumor was also longest in the mixture group. Our data suggest that hIFN-alpha2 gene therapy might be possible to be used as a new treatment for NE tumor patients. Further studies on the regulation of hIFN-alpha expression are needed, especially in combination with other cytokines, which could lead to a better understanding and improvements of hIFN-alpha gene therapy.