Modulation of bovine microvascular endothelial cell proteolytic properties by inhibitors of angiogenesis

Angiogenesis in B cell lymphoproliferative diseases. Biological and clinical studies

Angiogenesis is a necessary step in solid tumor progression (growth, invasion and metastasis) with which it correlates and is indicative of an unfavourable prognosis. We observed bone marrow angiogenesis in patients with active multiple myeloma (MM), though not in patients with non-active MM nor with monoclonal gammopathies of undetermined significance (MGUS). Microvessel density increased in parallel with the labeling index (LI%)--an indicator of plasma cell proliferating activity that correlates with prognosis--and defined a risk of MM progression in much the same way as LI% itself. Consequently, bone marrow angiogenesis could be an indication for unfavourable prognosis in MGUS and MM. Angiogenesis has also been demonstrated in lymph nodes involved by B cell non Hodgkin's lymphoma (B-NHL) belonging to the Working Formulation intermediate-grade (diffuse subtypes), and high-grade categories, but not in the low-grade and intermediate-grade (follicular subtype) categories. It correlated with the B-NHL cell proliferating activity, since large increments in this activity have already been demonstrated in intermediate- and high-grade vs low-grade tumors. Active MM, intermediate-grade, diffuse subtypes, and high-grade B-NHLs correspond to the vascular phases of B cell lymphoproliferative diseases, and could thus be assimilated to locally invasive and metastatic solid tumors. Similarly to solid tumors during these stages of progression, tumor B cells are also capable of inducing angiogenesis, both directly and indirectly by activating the inflammation infiltrate--a possibility that was first demonstrated by means of B-NHL implants onto the chick embryo chorioallantoic membrane. Anti-angiogenic therapy can be envisaged as a possible future development.

Plasminogen activator inhibitor type 1 in cancer: therapeutic and prognostic implications

Degradation of the extracellular matrix plays a crucial role in cancer invasion. This degradation is accomplished by the concerted action of several enzyme systems, including generation of the serine protease plasmin by the urokinase pathway of plasminogen activation, different types of collagenases and other metalloproteinases, and other extracellular enzymes. The degradative enzymes are involved also in tissue remodelling under non-malignant conditions, and the main difference appears to be that mechanisms which regulates these processes under normal conditions are defective in cancer. Specific inhibitors have been identified for most of the proteolytic enzymes, e.g. plasminogen activator inhibitors (PAI's) and tissue inhibitors of metalloproteinases (TIMP's). It has been contemplated that these inhibitors counteracted the proteolytic activity of the enzymes, thereby inhibiting extracellular tissue degradation which in turn should prevent tumor cell invasion. This review focuses on plasminogen inhibitor type 1 (PAI-1). It is described that PAI-1 is not produced by the epithelial cancer cell but by the stromal cells in the tumors, suggesting a concerted action between stroma and tumor cells in the processes controlling proteolysis in cancer. The specific localization of PAI-1 to the tumor stroma and in many cases to areas surrounding the tumor vessels has lead us to suggest that PAI-1 serves to protect the tumor stroma from the ongoing uPA-mediated proteolysis. This hypothesis is supported by recent clinical data showing increased levels of PAI-1 in metastases as compared to the primary tumor as well as data demonstrating that high levels of PAI-1 in tumor extracts from breast, lung, gastric and ovarian cancer is associated with a shorter overall survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Leukemia inhibitory factor (LIF) inhibits angiogenesis in vitro

Using an in vitro model in which endothelial cells can be induced to invade a three-dimensional collagen gel to form capillary-like tubular structures, we demonstrate that leukemia inhibitory factor (LIF) inhibits angiogenesis in vitro. The inhibitory effect was observed on both bovine aortic endothelial (BAE) and bovine microvascular endothelial (BME) cell, and occurred irrespective of the angiogenic stimulus, which included basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), the synergistic effect of the two in combination, or the tumor promoter phorbol myristate acetate. LIF inhibited bFGF- and VEGF-induced proliferation in BAE and BME cells. In addition, LIF inhibited BAE but not BME cell migration in a conventional two-dimensional assay. Finally, LIF decreased the proteolytic activity of BAE and BME cells and increased their expression of plasminogen activator inhibitor-1. These results demonstrate that LIF inhibits angiogenesis in vitro, an effect that can be correlated with a LIF-mediated decrease in endothelial cell proliferation, migration and extracellular proteolysis.