Summary The study of angiogenesis has grown exponentially over the past 40 years with the recognition that angiogenesis is essential for numerous pathologies and, more recently, with the advent of successful drugs to inhibit angiogenesis in tumours. The main problem with angiogenesis research remains the choice of appropriate assays to evaluate the efficacy of potential new drugs and to identify potential targets within the angiogenic process. This selection is made more complex by the recognition that heterogeneity occurs, not only within the endothelial cells themselves, but also within the specific microenvironment to be studied. Thus, it is essential to choose the assay conditions and cell types that most closely resemble the angiogenic disease being studied. This is especially important when aiming to translate data from in vitro to in vivo and from preclinical to the clinic. Here we critically review and highlight recent advances in the principle assays in common use including those for endothelial cell proliferation, migration, differentiation and co‐culture with fibroblasts and mural cells in vitro, vessel outgrowth from organ cultures and in vivo assays such as chick chorioallantoic membrane (CAM), zebrafish, sponge implantation, corneal, dorsal air sac, chamber and tumour angiogenesis models. Finally, we briefly discuss the direction likely to be taken in future studies, which include the use of increasingly sophisticated imaging analysis systems for data acquisition.

SummaryAngiogenesis, the development of new blood vessels from an existing vasculature, is essential in normal developmental processes and in numerous pathologies, including diabetic retinopathy, psoriasis and tumour growth and metastases. One of the problems faced by angiogenesis researchers has been the difficulty of finding suitable methods for assessing the effects of regulators of the angiogenic response. The ideal assay would be reliable, technically straightforward, easily quantifiable and, most importantly, physiologically relevant. Here, we review the advantages and limitations of the principal assays in use, including those for the proliferation, migration and differentiation of endothelial cells in vitro, vessel outgrowth from organ cultures and in vivo assays such as sponge implantation, corneal, chamber, zebrafish, chick chorioallantoic membrane (CAM) and tumour angiogenesis models.

Neuropilin-1 (Np1) and neuropilin-2 (Np2) are transmembrane glycoproteins with large extracellular domains that interact with both class 3 semaphorins and vascular endothelial growth factor (VEGF), and are involved in the regulation of many physiological pathways, including angiogenesis. The neuropilins also interact directly with the classical receptors for VEGF, VEGF-R1 and -R2, mediating signal transduction. The heart, glomeruli and osteoblasts express both Np1 and Np2, but there is differential expression in the adult vasculature, with Np1 expressed mainly by arterial endothelium, whereas Np2 is only expressed by venous and lymphatic endothelium. Both neuropilins are commonly over-expressed in regions of physiological (wound-healing) and pathological (tumour) angiogenesis, but the signal transduction pathways, neuropilin-mediated gene expression and the definitive role of neuropilins in angiogenic processes are not fully characterized. This review details the current evidence for the role of neuropilins in angiogenesis, and suggests future research directions that may enhance our understanding of the mechanisms of action of this unique family of proteins.

Summary With over thirty different hormones identified as being produced in the gastrointestinal (GI) tract, the gut has been described as ‘the largest endocrine organ in the body’ (Ann. Oncol., 12, 2003, S63). The classification of these hormones and the cells that produce them, the enteroendocrine cells (EECs), has provided the foundation for digestive physiology. Furthermore, alterations in the composition and function of EEC may influence digestive physiology and thereby associate with GI pathologies. Whilst there is a rapidly increasing body of data on the role and function of EEC in the upper GI tract, there is a less clear‐cut understanding of the function of EEC in the lower GI. Nonetheless, their presence and diversity are indicative of a role. This review focuses on the EECs of the lower GI where new evidence also suggests a possible relationship with the development and progression of primary adenocarcinoma.

Summary Initially found expressed in neuronal and then later in endothelial cells, it is well established that the transmembrane glycoproteins neuropilin‐1 (NRP1) and neuropilin‐2 (NRP2) play essential roles in axonal growth and guidance and in physiological and pathological angiogenesis. Neuropilin expression and function in epithelial cells has received little attention when compared with neuronal and endothelial cells. Overexpression of NRPs is shown to enhance growth, correlate with invasion and is associated with poor prognosis in various tumour types, especially those of epithelial origin. The contribution of NRP and its ligands to tumour growth and metastasis has spurred a strong interest in NRPs as novel chemotherapy drug targets. Given NRP’s role as a multifunctional co‐receptor with an ability to bind with disparate ligand families, this has sparked new areas of research implicating NRPs in diverse biological functions. Here, we review the growing body of research demonstrating NRP expression and role in the normal and neoplastic epithelium.

Physiological wound healing is a complex process requiring the temporal and spatial co-ordination of various signaling networks, biomechanical forces, and biochemical signaling pathways in both hypoxic and non-hypoxic conditions. Although a plethora of factors are required for successful physiological tissue repair, transforming growth factor beta (TGF-β) expression has been demonstrated throughout wound healing and shown to regulate many processes involved in tissue repair, including production of ECM, proteases, protease inhibitors, migration, chemotaxis, and proliferation of macrophages, fibroblasts of the granulation tissue, epithelial and capillary endothelial cells. TGF-β mediates these effects by stimulating signaling pathways through a receptor complex which contains Endoglin. Endoglin is expressed in a broad spectrum of proliferating and stem cells with elevated expression during hypoxia, and regulates important cellular functions such as proliferation and adhesion via Smad signaling. This review focuses on how the TGF-β family and Endoglin, regulate stem cell availability, and modulate cellular behavior within the wound microenvironment, includes current knowledge of the signaling pathways involved, and explores how this information may be applicable to inflammatory and/or angiogenic diseases such as fibrosis, rheumatoid arthritis and metastatic cancer.

Tissue factor, the primary initiator of the coagulation cascade, maintains vascular integrity in response to injury. It is now recognised that, in addition to the role as a procoagulant activator, tissue factor participates in many tumour-related processes that contribute to malignant disease progression. The present review details the recent evidence supporting a role for tissue factor in tumour haemostasis, angiogenesis, metastasis and malignant cell survival. Furthermore, future research directions are discussed that may enhance our understanding of the role and regulation of this protein, which could ultimately lead to the innovative design and development of new anticancer therapies. IntroductionAngiogenesis, the development of new blood vessels from the existing vasculature, and haemostasis, the coagulation cascade leading to clot formation, are among the most consistent host responses associated with cancer. Tissue factor (TF) normally safeguards the vascular integrity of tissues by initiating the coagulation cascade following vessel injury. Hypercoagulability is exhibited by most cancer patients and contributes to the pathogenesis of tumour growth and metastasis by promoting angiogenesis. Haemostasis and angiogenesis are therefore interrelated processes with important implications for cancer therapy.TF, similar to a number of haemostatic proteins, participates in many tumour-related processes, including tumour angiogenesis, metastasis, hypercoagulability and tumour cell survival; processes that all contribute to malignant disease progression. The molecular mechanisms responsible for the actions of TF are only just beginning to be elucidated, but it is thought that they occur by the action of intracellular signalling, resulting in gene transcription and subsequent protein synthesis. Tissue factorTF -also known as coagulation factor III, thromboplastin, or CD142 -is a 47 kDa transmembrane glycoprotein first cloned independently by four different groups in 1987 [1][2][3][4]. The human TF gene spans 12.4 kbp, has six exons and is located on chromosome 1, p21-p22. The TF protein consists of a 219-amino-acid extracellular domain, a 23-amino-acid transmembrane segment and a 21-amino-acid cytoplasmic tail that does not bear significant homology with other proteins [5]. In silico studies have resulted in TF being classified as a member of the class II cytokine/haematopoietic growth factor family [6]. The extracellular domain of TF contains factor VII/activated factor VII (FVIIa) binding sites, but the transmembrane domain plays a crucial role in anchoring the TF-FVIIa complex to the cell surface in addition to complete expression of the procoagulant activity [7]. TF gene expression is complex and is regulated by a number of transcription factors that may be sensitive to hypoxia or anoxia, including activator protein (AP-1), nuclear factor-κB (NF-κB), Sp-1 and early growth response gene-1 (Egr-1) [8,9]. In addition, heparanase and platelet endothelial cell adhesion molecule 1 both participate in the regula...

Levels of VEGF, VEGF-R2, Np1 and Np2 are increased, whereas VEGF-R1 expression is decreased in angiogenesis, suggesting a role for VEGF-receptor complexes in early wound healing. This altered protein expression and increased presence of vessels is prolonged, suggesting that structural remodelling continues for at least 2 years after surgery.