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Thrombospondin (TSP)-1 and TSP-2 share similar structures and functions, including a remarkable antiangiogenic activity. We have previously demonstrated that a mechanism of the antiangiogenic activity of TSP-1 is the interaction of its type III repeats domain with fibroblast growth factor-2 (FGF2), affecting the growth factor bioavailability and angiogenic activity. Since the type III repeats domain is conserved in TSP-2, this study aimed at investigating whether also TSP-2 retained the ability to interact with FGF2. The FGF2 binding properties of TSP-1 and TSP-2 and their recombinant domains were analyzed by solid-phase binding and surface plasmon resonance assays. TSP-2 bound FGF2 with high affinity (Kd = 1.3 nM). TSP-2/FGF2 binding was inhibited by calcium and heparin. The FGF2-binding domain of TSP-2 was located in the type III repeats and the minimal interacting sequence was identified as the GVTDEKD peptide in repeat 3C, corresponding to KIPDDRD, the active sequence of TSP-1. A second putative FGF2 binding sequence was also identified in repeat 11C of both TSPs. Computational docking analysis predicted that both the TSP-2 and TSP-1-derived heptapeptides interacted with FGF2 with comparable binding properties. Accordingly, small molecules based on the TSP-1 active sequence blocked TSP-2/FGF2 interaction. Binding of TSP-2 to FGF2 impaired the growth factor ability to interact with its cellular receptors, since TSP-2-derived fragments prevented the binding of FGF2 to both heparin (used as a structural analog of heparan sulfate proteoglycans) and FGFR-1. These findings identify TSP-2 as a new FGF2 ligand that shares with TSP-1 the same molecular requirements for interaction with the growth factor and a comparable capacity to block FGF2 interaction with proangiogenic receptors. These features likely contribute to TSP-2 antiangiogenic and antineoplastic activity, providing the rationale for future therapeutic applications. [ABSTRACT FROM AUTHOR]

Purpose: OTX008 is a galectin-1-targeting compound, currently undergoing a phase I clinical trial. This study aimed at investigating OTX008 pharmacokinetics (PK) and antineoplastic activity. Methods: Pharmacokinetics and activity of OTX008 were analyzed in the human ovarian carcinoma A2780-1A9 and glioblastoma U87MG xenografted in nude mice. In vitro, OTX008 was tested on tumor and endothelial cells. Results: After 5 mg/kg i.v., OTX008 achieved plasma Cmax of 14.39 μg/mL, distributed rapidly, and was eliminated with a half-life of 31.4 h. Tumor OTX008 Cmax (1.65 μg/g, 1.76 μM), achieved at 0.5 h, remained high at 24 h (0.516 μg/g, 0.55 μM) with AUC of 15.76 μg/g*h. OTX008 accumulated in the tumor after repeated administrations achieving a concentration of 2.3 μM, compatible with the concentrations active in vitro. OTX008 (5 mg/kg i.v., every other day for 3 weeks) inhibited the in vivo growth of A2780-1A9, whereas U87MG was not sensitive. In vitro, OTX008 affected endothelial cell proliferation, motility, invasiveness, and cord formation. Tumor cell proliferation was also inhibited, with differences in sensitivity among cell lines (IC50 from 1 to 190 μM). OTX008 potentiated the activity of the tyrosine kinase inhibitor sunitinib on A2780-1A9 in vivo and in vitro, where the combination showed synergistic (endothelial cells) and additive (A2780-1A9) antiproliferative activity, indicating that the combination targets both the tumor and vascular compartments. Conclusions: OTX008-alone or in combination with sunitinib-has a favorable PK and antineoplastic activity on selected tumor models through the effects on both endothelial and tumor cells. [ABSTRACT FROM AUTHOR]

Tumor neovascularization is controlled by a balance between positive and negative effectors, whose production can be regulated by oncogenes and tumor suppressor genes. The aim of this study was to investigate whether the angiogenic potential of tumors could also be controlled by p73, a gene homologous to the tumor suppressor p53, whose involvement in tumor angiogenesis is known. We have studied the production of proangiogenic (VEGF, FGF-2, PIGF and PDGF) and antiangiogenic (TSP-1) factors in two p73 overexpressing clones obtained from the human ovarian carcinoma cells A2780. TSP-1 was downregulated in both clones compared to mock transfected cells, both at mRNA and protein level. Conversely, both clones showed an increased production of VEGF mRNA and protein. For both TSP-1 and VEGF, regulation of expression was partially due to modulation of the promoter activity, and was dependent on p53 status. Production of the other angiogenic factors FGF-2, PIGF and PDGF-B was also increased in p73 overexpressing clones. The two clones were more angiogenic than parental cells, as shown in vitro by their increased chemotactic activity for endothelial cells, and in vivo by the generation of more vascularized tumors. These findings suggest a potential role of p73 in tumor angiogenesis. Oncogene (2001) 20, 7293–7300. [ABSTRACT FROM AUTHOR]