Angiogenesis is essential for tumor growth and metastasis. In the process of angiogenesis, the interaction between adhesive proteins of endothelial cells and extracellular matrix components plays an important role by mediating cell attachment, which is indispensable for their motility, and by transmitting the regulatory signals for cell locomotion and proliferation. In this study, we examined the hypothesis that CD44 expressed on the endothelial cell surface is involved in the angiogenesis process. The experiments using calf pulmonary artery endothelial cells (CPAE) and a human microvascular endothelial cell line (HMEC-I) show that a monoclonal antibody against CD44 (clone J 173) inhibits endothelial cell proliferation by about 30% and migration by 25-50%, and abolishes the stimulating effect of hyaluronan polysaccharides on endothelial cell migration and proliferation. This antibody also suppresses the capillary formation of CPAE in an in vitro model of angiogenesis using fibrin matrix. These results provide evidence of the involvement of endothelial-cell-associated CD44 in angiogenesis.o 1996 Wiley-Liss, Inc.Angiogenesis plays a fundamental role in many physiological and pathological processes including wound healing, tissue repair and tumor growth (Folkman, 1995). For the formation of a new vessel, migration of stimulated endothelial cells and subsequent tube formation virtually depend on the occurrence of timely and locally coordinated extracellular proteolysis, cell adhesion and activation during the cell migration. Therefore, the interaction of adhesive proteins expressed on the endothelial cell surface with the components of extracellular matrix is one of the factors determining the occurrence of angiogenesis. Perturbation of these interactions may abolish an ongoing angiogenesis process. For example, blocking the binding of the integrin molecule to matrix-associated vitronectin led to endothelial cell apoptosis and abolished tumor-induced angiogenesis in vivo (Brooks et al., 1994). Furthermore, the interaction of adhesive proteins with their endothelial cell-surface receptors may also activate the process of angiogenesis. For instance, endothelial cells could be stimulated by the surrounding fibrin I1 matrix to form capillary tubes in vitro (Chalupowicz et al., 1995). However, due to the complexity of the mechanisms involved in cell adhesion, the functions of many adhesive molecules on the endothelial cell surface still remain to be determined.One of the examples is CD44, discovered through its role in mediating leukocyte adhesion and lymphocyte homing (Haynes et al., 1989). Although several studies reported the presence of CD44 on endothelial cells such as human microvascular endothelial cells (HMEC-1) (Xu et al., 1994), bovine microvascular endothelial cells (BME) (Bourguignon et al., 1992) and human umbilical endothelial cells (HUVEC) (Liesveld et al., 1994), the role of CD44 expressed on the endothelial cell surface still remains to be clarified. CD44 is a transmembrane molecule with multiple isofo...

AdmATF is a recombinant adenovirus encoding a secreted within and at the vicinity of the injection site was also supversion of the amino-terminal fragment (ATF) of murine pressed, suggesting that AdmATF inhibited primary tumor urokinase (uPA). This defective adenovirus was used in growth by targeting angiogenesis. AdmATF also interfered three murine models to assess the antitumoral effects with tumor cell establishment at distant sites: (1) lung disassociated with local or systemic delivery of ATF, a broad semination of Lewis lung carcinoma cells was significantly cell invasion inhibitor that antagonizes uPA binding to its reduced following intratumoral injection at the primary site; cell surface receptor (uPAR). A single intratumoral injection and (2) systemic administration of AdmATF inhibited subof AdmATF into pre-established MDA-MB-231 human sequent liver metastasis in a LS174T human colon carcibreast xenografts grown in athymic mice, or into pre-estabnoma xenograft model. These data outline the potential of lished C57/BL6 syngeneic Lewis lung carcinoma resulted using a recombinant adenovirus directing the secretion of an in a specific arrest of tumor growth. Neovascularization antagonist of cell-associated uPA for cancer gene therapy.

Interaction of tumor cells with platelets facilitates metastasis of tumor cells. It has been proposed that platelets protect tumor cells against the host's immune defense and enhance tumor-cell extravasation. In the present work we show that platelets increase the invasiveness of 3 mammalian cell lines (MCF-7, ZR-51 and MDA-MB231) through extracellular matrix, and propose this as an additional mechanism by which platelets facilitate metastasis. Since gelatinase and urokinase have both been implicated in degradation of the extracellular matrix and cell migration, and therefore in tumor invasion, we have also analyzed whether the interaction of platelets with tumor cells can modify the secretion of these proteases by tumor cells. MDA-MB231, which was the most invasive cell line among the 3 tested and was the most potent in inducing platelet aggregation, secreted the highest level of urokinase and was the only one in which gelatinase was detected. While platelets had no significant effect on the urokinase activity expressed by these cells, they induced in MDA-MB231 an important increase in the secretion of gelatinase, which can be reproduced by both platelet membrane and platelet releasate of activated platelets. This increase in gelatinase could be responsible, at least in part, for the increased invasiveness of these cells, since added TIMP-1 significantly reduced the number of cells which traversed matrigel.