Journal Article•
Blockade of the Vascular Endothelial Growth Factor Stress Response Increases the Antitumor Effects of Ionizing Radiation
15 Jul 1999-Cancer Research (American Association for Cancer Research)-Vol. 59, Iss: 14, pp 3374-3378
TL;DR: It is reported that VEGF expression is induced in Lewis lung carcinomas (LLCs) both in vitro and in vivo after exposure to ionizing radiation (IR) and in human tumor cell lines (Seg-1 esophageal adenocarcinoma, SQ20B squamous cell carcinoma, T98 and U87 glioblastomas, and U1 melanoma) in vitro.
Abstract: The family of vascular endothelial growth factor (VEGF) proteins include potent and specific mitogens for vascular endothelial cells that function in the lation of angiogenesis Inhibition of VEGF-induced angiogenesis either by neutralizing antibodies or dominant-negative soluble receptor, blocks the growth of primary and metastatic experimental tumors Here we report that VEGF expression is induced in Lewis lung carcinomas (LLCs) both in vitro and vivo after exposure to ionizing radiation (IR) and in human tumor cell lines (Seg-1 esophageal adenocarcinoma, SQ20B squamous cell carcinoma, T98 and U87 glioblastomas, and U1 melanoma) in vitro. The biological significance of IR-induced VEGF production is supported by our finding that treatment of tumor-bearing mice (LLC, Seg-1, SQ20B, and U87) with a neutralizing antibody to VEGF-165 before irradiation is associated with a greater than additive antitumor effect. In vitro, the addition of VEGF decreases IR-induced killing of human umbilical vein endothelial cells, and the anti-VEGF treatment potentiates IR-induced lethality of human umbilical vein endothelial cells. Neither recombinant VEGF protein nor neutralizing antibody to VEGF affects the radiosensitivity of tumor cells These findings support a model in which induction of VEGF by IR contributes to the protection of tumor blood vessels from radiation-mediated cytotoxicity and thereby to tumor radioresistance.
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TL;DR: Preclinical studies have shown that endostatin effectively inhibits tumor growth and shrinks existing tumor blood vessels and therapy with endogenous inhibitors of angiogenesis, such asendostatin and angiostatin may reverse the angiogenic switch preventing growth of tumor vasculature.
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TL;DR: The basic premise of this review is that a combination of imaging and PDT will provide improved research and therapeutic strategies.
Abstract: 1.1 Photodynamic Therapy and Imaging
The purpose of this review is to present the current state of the role of imaging in photodynamic therapy (PDT). In order for the reader to fully appreciate the context of the discussions embodied in this article we begin with an overview of the PDT process, starting with a brief historical perspective followed by detailed discussions of specific applications of imaging in PDT. Each section starts with an overview of the specific topic and, where appropriate, ends with summary and future directions. The review closes with the authors’ perspective of the areas of future emphasis and promise. The basic premise of this review is that a combination of imaging and PDT will provide improved research and therapeutic strategies.
PDT is a photochemistry-based approach that uses a light-activatable chemical, termed a photosensitizer (PS), and light of an appropriate wavelength, to impart cytotoxicity via the generation of reactive molecular species (Figure 1a). In clinical settings, the PS is typically administered intravenously or topically, followed by illumination using a light delivery system suitable for the anatomical site being treated (Figure 1b). The time delay, often referred to as drug-light interval, between PS administration and the start of illumination with currently used PSs varies from 5 minutes to 24 hours or more depending on the specific PS and the target disease. Strictly speaking, this should be referred to as the PS-light interval, as at the concentrations typically used the PS is not a drug, but the drug-light interval terminology seems to be used fairly frequently. Typically, the useful range of wavelengths for therapeutic activation of the PS is 600 to 800 nm, to avoid interference by endogenous chromophores within the body, and yet maintain the energetics necessary for the generation of cytotoxic species (as discussed below) such as singlet oxygen (1O2). However, it is important to note that photosensitizers can also serve as fluorescence imaging agents for which activation with light in the 400nm range is often used and has been extremely useful in diagnostic imaging applications as described extensively in Section 2 of this review. The obvious limitation of short wavelength excitation is the lack of tissue penetration so that the volumes that are probed under these conditions are relatively shallow.
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Figure 1
(A) A schematic representation of PDT where PS is a photoactivatable multifunctional agent, which, upon light activation can serve as both an imaging agent and a therapeutic agent. (B) A schematic representation of the sequence of administration, localization and light activation of the PS for PDT or fluorescence imaging. Typically the PS is delivered systemically and allowed to circulate for an appropriate time interval (the “drug-light interval”), during which the PS accumulates preferentially in the target lesion(s) prior to light activation. In the idealized depiction here the PS is accumulation is shown to be entirely in the target tissue, however, even if this is not the case, light delivery confers a second layer of selectivity so that the cytotoxic effect will be generated only in regions where both drug and light are present. Upon localization of the PS, light activation will result in fluorescence emission which can be implemented for imaging applications, as well as generation cytotoxic species for therapy. In the former case light activation is achieved with a low fluence rate to generate fluorescence emission with little or no cytotoxic effect, while in the latter case a high fluence rate is used to generate a sufficient concentration of cytotoxic species to achieve biological effects.
1,922 citations
TL;DR: The role of V EGF in physiological and pathological processes is reviewed and how modulation of VEGF expression creates new therapeutic possibilities is discussed.
Abstract: Angiogenesis is a hallmark of wound healing, the menstrual cycle, cancer, and various ischemic and inflammatory diseases. A rich variety of pro- and antiangiogenic molecules have already been discovered. Vascular endothelial growth factor (VEGF) is an interesting inducer of angiogenesis and lymphangiogenesis, because it is a highly specific mitogen for endothelial cells. Signal transduction involves binding to tyrosine kinase receptors and results in endothelial cell proliferation, migration, and new vessel formation. In this article, the role of VEGF in physiological and pathological processes is reviewed. We also discuss how modulation of VEGF expression creates new therapeutic possibilities and describe recent developments in this field.
1,750 citations
Cites background from "Blockade of the Vascular Endothelia..."
...Several growth factors, such as tissue growth factor(TGF- ), epidermal growth factor (EGF), and plateletderived growth factor BB (PDGF-BB) induce VEGF-A mRNA expression....
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...Knowing that PDGF is released from platelets following tissue injury, it is possible that VEGF-C is induced in wounds, contributing to the repair of tissue injury....
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...Benjamin LE, Hemo I, and Keshet E (1998) A plasticity window for blood vessel remodelling is defined by pericyte coverage of the preformed endothelial network and is regulated by PDGF-B and VEGF....
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...They mainly block several subtypes of the VEGFR and also other tyrosine kinase receptors such as KIT, PDGF receptor, fibroblast growth factor receptor 1, Tie-2, and FLT3 (Laird et al., 2000, 2002; Wedge et al., 2000; Wood et al., 2000)....
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...It has been shown that VEGF-A mRNA is induced in vivo in wounds by PDGF in fibroblasts and by keratinocyte growth factor in epidermal keratinocytes (Enholm et al., 1997)....
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TL;DR: Angiogenesis inhibitors are a new class of drugs, for which the general rules involving conventional chemotherapy might not apply, and clinical application depends partly on the transfer of expertise from scientists who are familiar with the biology of angiogenesis to clinicians.
Abstract: Angiogenesis inhibitors are a new class of drugs, for which the general rules involving conventional chemotherapy might not apply. The successful translation of angiogenesis inhibitors to clinical application depends partly on the transfer of expertise from scientists who are familiar with the biology of angiogenesis to clinicians. What are the most common questions that clinicians ask as they begin to test angiogenesis inhibitors in cancer clinical trials?
1,545 citations
TL;DR: Recognized as the single most important angiogenic cytokine, VEGF-A has a central role in tumor biology and will likely have an important role in future approaches designed to evaluate patient prognosis and may also become an important target for cancer therapy.
Abstract: Vascular endothelial growth factor A (VEGF-A), the founding member of the vascular permeability factor (VPF)/VEGF family of proteins, is an important angiogenic cytokine with critical roles in tumor angiogenesis. This article reviews the literature with regard to VEGF-A's multiple functions, the mechanisms by which it induces angiogenesis, and its current and projected roles in clinical oncology. VEGF-A is a multifunctional cytokine that is widely expressed by tumor cells and that acts through receptors (VEGFR-1, VEGFR-2, and neuropilin) that are expressed on vascular endothelium and on some other cells. It increases microvascular permeability, induces endothelial cell migration and division, reprograms gene expression, promotes endothelial cell survival, prevents senescence, and induces angiogenesis. Recently, VEGF-A has also been shown to induce lymphangiogenesis. Measurements of circulating levels of VEGF-A may have value in estimating prognosis, and VEGF-A and its receptors are potential targets for therapy. Recognized as the single most important angiogenic cytokine, VEGF-A has a central role in tumor biology and will likely have an important role in future approaches designed to evaluate patient prognosis. It may also become an important target for cancer therapy.
1,537 citations
References
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TL;DR: A new method of total RNA isolation by a single extraction with an acid guanidinium thiocyanate-phenol-chloroform mixture is described, providing a pure preparation of undegraded RNA in high yield and can be completed within 4 h.
65,881 citations
"Blockade of the Vascular Endothelia..." refers methods in this paper
...Northern Blots. Total RNA was isolated from cultured cells and tumor tissue by the guanidine thiocyanate method ( 16 ) using Trizol LS (Life Sciences, Inc.)....
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TL;DR: The genomic sequencing procedures are applicable to the analysis of genetic polymorphisms, DNA methylation at deoxycytidines, and nucleic acid-protein interactions at single nucleotide resolution.
Abstract: Unique DNA sequences can be determined directly from mouse genomic DNA. A denaturing gel separates by size mixtures of unlabeled DNA fragments from complete restriction and partial chemical cleavages of the entire genome. These lanes of DNA are transferred and UV-crosslinked to nylon membranes. Hybridization with a short 32P-labeled single-stranded probe produces the image of a DNA sequence "ladder" extending from the 3' or 5' end of one restriction site in the genome. Numerous different sequences can be obtained from a single membrane by reprobing. Each band in these sequences represents 3 fg of DNA complementary to the probe. Sequence data from mouse immunoglobulin heavy chain genes from several cell types are presented. The genomic sequencing procedures are applicable to the analysis of genetic polymorphisms, DNA methylation at deoxycytidines, and nucleic acid-protein interactions at single nucleotide resolution.
7,858 citations
TL;DR: The work from the authors' laboratories reviewed herein was supported by grants from the National Cancer Institute.
6,895 citations
"Blockade of the Vascular Endothelia..." refers background in this paper
...In normal tissues, angiogenesis is tightly regulated by the balance between angiogenic and antiangiogenic factors ( 1 )....
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TL;DR: The establishment of a vascular supply is required for organ development and differentiation as well as for tissue repair and reproductive functions in the adult.
Abstract: The establishment of a vascular supply is required for organ development and differentiation as well as for tissue repair and reproductive functions in the adult1 Neovascularization (angiogenesis) is also implicated in the pathogenesis of a number of disorders These include: proliferative retinopathies, age-related macular degeneration, tumors, rheumatoid arthritis, and psoriasis1,2 A strong correlation has been noted between density of microvessels in primary breast cancers and their nodal metastases and patient survival3 Similarly, a correlation has been reported between vascularity and invasive behavior in several other tumors4–6
4,603 citations
TL;DR: It is demonstrated that inhibition of the action of an angiogenic factor spontaneously produced by tumour cells may suppress tumour growth in vivo.
Abstract: The development of new blood vessels (angiogenesis) is required for many physiological processes including embryogenesis, wound healing and corpus luteum formation. Blood vessel neoformation is also important in the pathogenesis of many disorders, particularly rapid growth and metastasis of solid tumours. There are several potential mediators of tumour angiogenesis, including basic and acidic fibroblast growth factors, tumour necrosis factor-alpha and transforming factors-alpha and -beta. But it is unclear whether any of these agents actually mediates angiogenesis and tumour growth in vivo. Vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen and an angiogenesis inducer released by a variety of tumour cells and expressed in human tumours in situ. To test whether VEGF may be a tumour angiogenesis factor in vivo, we injected human rhabdomyosarcoma, glioblastoma multiforme or leiomyosarcoma cell lines into nude mice. We report here that treatment with a monoclonal antibody specific for VEGF inhibited the growth of the tumours, but had no effect on the growth rate of the tumour cells in vitro. The density of vessels was decreased in the antibody-treated tumours. These findings demonstrate that inhibition of the action of an angiogenic factor spontaneously produced by tumour cells may suppress tumour growth in vivo.
3,863 citations
"Blockade of the Vascular Endothelia..." refers result in this paper
...By day 6, consistent with previous observations (5, 6, 8, 9 ), treatment with anti-VEGF alone produced a 42.6% reduction in tumor volume (796 6 41 mm3; P 5 0.004)....
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