Fibronectin fragments generated by pancreatic trypsin act as endogenous inhibitors of pancreatic tumor growth.

BACKGROUND: The pancreatic microenvironment has a defensive role against cancer but it can acquire tumor-promoting properties triggered by multiple mechanisms including alterations in the equilibrium between proteases and their inhibitors. The identification of proteolytic events, targets and pathways would set the basis for the design of new therapeutic approaches. METHODS AND RESULTS: Here we demonstrate that spheroids isolated from human and murine healthy pancreas and co-transplanted orthotopically with pancreatic ductal adenocarcinoma (PDAC) in mouse pancreas inhibited tumor growth. The effect was mediated by trypsin-generated fibronectin (FN) fragments released by pancreatic spheroids. Tumor inhibition was observed also in a model of acute pancreatitis associated with trypsin activation. Mass spectrometry proteomic analysis of fragments and mAb against different FN epitopes identified the FN type III domain as responsible for the activity. By inhibiting integrin α5ß1, FAK and FGFR1 signaling, the fragments induced tumor cell detachment and reduced cell proliferation. Consistent with the mutual relationship between the two pathways, FGF2 restored both FGFR1 and FAK signaling and promoted PDAC cell adhesion and proliferation. FAK and FGFR inhibitors additively inhibited PDAC growth in vitro and in orthotopic in vivo models. CONCLUSIONS: This study identifies a novel role for pancreatic trypsin and fibronectin cleavage as a mechanism of protection against cancer by the pancreatic microenvironment. The finding of a FAK-FGFR cross-talk in PDAC support the combination of FAK and FGFR inhibitors for PDAC treatment to emulate the protective effect of the normal pancreas against cancer.

Tumor vascular remodeling by thrombospondin-1 enhances drug delivery and antineoplastic activity.

The disorganized and inefficient tumor vasculature is a major obstacle to the delivery and efficacy of antineoplastic treatments. Antiangiogenic agents can normalize the tumor vessels, improving vessel function and boosting the distribution and activity of chemotherapy. The type III repeats (T3R) domain of thrombospondin-1 contains different potential antiangiogenic sequences. We therefore hypothesized that it might affect the tumor vasculature. Ectopic expression of the T3R domain by the tumor cells or by the host, or administration of recombinant T3R, delayed the in vivo growth of experimental tumors. Tumors presented marked reorganization of the vasculature, with abundant but smaller vessels, associated with substantially less necrosis. Mechanistically, the use of truncated forms of the domain, containing different active sequences, pointed to the FGF2/FGFR/ERK axis as a target for T3R activity. Along with reduced necrosis, the expression of T3R promoted tumor distribution of chemotherapy (paclitaxel), with a higher drug concentration and more homogeneous distribution, as assessed by HPLC and MALDI imaging mass spectrometry. T3R-expressing tumors were more responsive to paclitaxel and cisplatin. This study shows that together with its known role as a canonical inhibitor of angiogenesis, thrombospondin-1 can also remodel tumor blood vessels, affecting the morphological and functional properties of the tumor vasculature. The ability of T3R to reduce tumor growth and improve the response to chemotherapy opens new perspectives for therapeutic strategies based on T3R to be used in combination therapies.

CCN-Based Therapeutic Peptides Modify Pancreatic Ductal Adenocarcinoma Microenvironment and Decrease Tumor Growth in Combination with Chemotherapy.

The prominent desmoplastic stroma of pancreatic ductal adenocarcinoma (PDAC) is a determinant factor in tumor progression and a major barrier to the access of chemotherapy. The PDAC microenvironment therefore appears to be a promising therapeutic target. CCN2/CTGF is a profibrotic matricellular protein, highly present in the PDAC microenvironment and associated with disease progression. Here we have investigated the therapeutic value of the CCN2-targeting BLR100 and BLR200, two modified synthetic peptides derived from active regions of CCN3, an endogenous inhibitor of CCN2. In a murine orthotopic PDAC model, the two peptides, administered as monotherapy at low doses (approximating physiological levels of CCN3), had tumor inhibitory activity that increased with the dose. The peptides affected the tumor microenvironment, inhibiting fibrosis and vessel formation and reducing necrosis. Both peptides were active in preventing ascites formation. An increased activity was obtained in combination regimens, administering BLR100 or BLR200 with the chemotherapeutic drug gemcitabine. Pharmacokinetic analysis indicated that the improved activity of the combination was not mainly determined by the substantial increase in gemcitabine delivery to tumors, suggesting other effects on the tumor microenvironment. The beneficial remodeling of the tumor stroma supports the potential value of these CCN3-derived peptides for targeting pathways regulated by CCN2 in PDAC.

The calcium-binding type III repeats domain of thrombospondin-2 binds to fibroblast growth factor 2 (FGF2).

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.

Antimetastatic and antiangiogenic activity of trabectedin in cutaneous melanoma.

Trabectedin is a marine-derived antineoplastic drug. Besides targeting the cancer cells, trabectedin has a peculiar activity on the tumor microenvironment with marked effects on the vasculature and the immune response. Because a favorable microenvironment is a key factor in the progression of cutaneous melanoma, we hypothesized that trabectedin might affect the growth and metastasis of this highly aggressive cancer. This study shows that trabectedin inhibited the subcutaneous growth of the murine melanoma B16-BL6 and K1735-M2. In line with its known activities on the environment of other tumor types, it caused a significant reduction of tumor blood vessel density and tumor-associated macrophages. Trabectedin had a significant antimetastatic activity, inhibiting the formation of lung colonies following intravenous injection of B16-BL6 or K1735-M2 cells. The drug was also active in a clinically relevant spontaneous metastasis assay, where it inhibited lung metastasis when administered before (neoadjuvant) or after (adjuvant) surgical removal of the primary tumor. Relevant to its antimetastatic activity, trabectedin inhibited melanoma cell invasiveness in vitro, associated with increased tissue inhibitor of metalloproteinase-1 production and alteration in cell shape and cytoskeleton organization. This study shows that trabectedin affects melanoma growth and metastasis, acting with tumor-dependent mechanisms on both the tumor cells and the vascular and the inflammatory tumor microenvironment.

Expression of thrombospondin-1 by tumor cells in patient-derived ovarian carcinoma xenografts.

PURPOSE: Thrombospondin-1 (TSP-1), a major regulator of cell interaction with the environment, is often deregulated in cancers, including ovarian carcinoma. Both the tumor and the host cells can release TSP-1 in the tumor microenvironment. The relative contribution of the two sources in determining TSP-1 levels in ovarian cancer remains to be elucidated. This study was designed to investigate the expression of tumor TSP-1 in a panel of 29 patient-derived ovarian adenocarcinoma xenografts (PDX), using analytical tools specific for human (tumor-derived) rather than murine (host-derived) TSP-1. METHODOLOGY: Human-specific microarray and ELISA were used to measure tumor TSP-1 expression and plasma levels. RESULTS: Tumor-derived TSP-1 was heterogeneously expressed in PDX. Expression was higher in the corresponding original patient's tumor, where stroma-derived TSP-1 is also analyzed, indicating that both the tumor and the host contribute to TSP-1 production. TSP-1 was differentially expressed according to tumor grade, but not affected by p53 expression or mutational status. Findings were confirmed in an external gene expression dataset (101 patients). In a functional enrichment analysis, TSP-1 correlated with genes related to angiogenesis, cell motility, communication and shape. Plasma TSP-1, detectable in 10/11 PDX, was not associated to its expression in the tumor. The possible association of plasma TSP-1 with p53 mutations and response to chemotherapy warrants further investigation. CONCLUSIONS: Ovarian carcinoma PDX are a useful tool to investigate the relative contribution of stroma and tumor cells in the production of tumor associated factors, in relation to the tumor behavior, molecular properties and response to therapy.

Thrombospondin-1 is part of a Slug-independent motility and metastatic program in cutaneous melanoma, in association with VEGFR-1 and FGF-2.

Differently from most transformed cells, cutaneous melanoma expresses the pleiotropic factor thrombospondin-1 (TSP-1). Herein, we show that TSP-1 (RNA and protein), undetectable in four cultures of melanocytes and a RGP melanoma, was variously present in 13 cell lines from advanced melanomas or metastases. Moreover, microarray analysis of 55 human lesions showed higher TSP-1 expression in primary melanomas and metastases than in common and dysplastic nevi. In a functional enrichment analysis, the expression of TSP-1 correlated with motility-related genes. Accordingly, TSP-1 production was associated with melanoma cell motility in vitro and lung colonization potential in vivo. VEGF/VEGFR-1 and FGF-2, involved in melanoma progression, regulated TSP-1 production. These factors were coexpressed with TSP-1 and correlated negatively with Slug (SNAI2), a cell migration master gene implicated in melanoma metastasis. We conclude that TSP-1 cooperates with FGF-2 and VEGF/VEGFR-1 in determining melanoma invasion and metastasis, as part of a Slug-independent motility program.

Antiangiogenic activity of trabectedin in myxoid liposarcoma: involvement of host TIMP-1 and TIMP-2 and tumor thrombospondin-1.

Trabectedin is a marine natural product, approved in Europe for the treatment of soft tissue sarcoma and relapsed ovarian cancer. Clinical and experimental evidence indicates that trabectedin is particularly effective against myxoid liposarcomas where response is associated to regression of capillary networks. Here, we investigated the mechanism of the antiangiogenic activity of trabectedin in myxoid liposarcomas. Trabectedin directly targeted endothelial cells, impairing functions relying on extracellular matrix remodeling (invasion and branching morphogenesis) through the upregulation of the inhibitors of matrix metalloproteinases TIMP-1 and TIMP-2. Increased TIMPs synthesis by the tumor microenvironment following trabectedin treatment was confirmed in xenograft models of myxoid liposarcoma. In addition, trabectedin upregulated tumor cell expression of the endogenous inhibitor thrombospondin-1 (TSP-1, a key regulator of angiogenesis-dependent dormancy in sarcoma), in in vivo models of myxoid liposarcomas, in vitro cell lines and primary cell cultures from patients' myxoid liposarcomas. Chromatin Immunoprecipitation analysis showed that trabectedin displaced the master regulator of adipogenesis C/EBPß from the TSP-1 promoter, indicating an association between the up-regulation of TSP-1 and induction of adipocytic differentiation program by trabectedin. We conclude that trabectedin inhibits angiogenesis through multiple mechanisms, including directly affecting endothelial cells in the tumor microenvironment--with a potentially widespread activity--and targeting tumor cells' angiogenic activity, linked to a tumor-specific molecular alteration.

Pharmacokinetics and antineoplastic activity of galectin-1-targeting OTX008 in combination with sunitinib.

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.

Inhibition of SIRT2 potentiates the anti-motility activity of taxanes: implications for antineoplastic combination therapies.

Taxanes are potent inhibitors of cell motility, a property implicated in their antiangiogenic and antimetastatic activity and unrelated to their antiproliferative effect. The molecular mechanism of this anti-motility activity is poorly understood. In this study, we found that paclitaxel induced tubulin acetylation in endothelial and tumor cells, at concentrations that affected cell motility but not proliferation (10(-8) to 10(-9) M, for 4 hours). Induction of tubulin acetylation correlated with inhibition of motility but not proliferation based on a comparison of highly and poorly cytotoxic taxanes (paclitaxel and IDN5390) and tumor cell lines sensitive and resistant to paclitaxel (1A9 and 1A9 PTX22). Consistent with the hypothesis that tubulin deacetylase activity might affect cell response to the anti-motility activity of taxanes, we found that overexpression of the tubulin deacetylase SIRT2 increased cell motility and reduced cell response to the anti-motility activity of paclitaxel. Conversely, the SIRT2 inhibitor splitomicin reduced cell motility and potentiated the anti-motility activity of paclitaxel. The inhibitory effect was further potentiated by the addition of the HDAC6 inhibitor trichostatin A. Paclitaxel and splitomicin promoted translocation into the nucleus--and hence activation--of FOXO3a, a negative regulator of cell motility. This study indicates a role for SIRT2 in the regulation of cell motility and suggests that therapies combining sirtuin inhibitors and taxanes could be used to treat cell motility-based pathologic processes such as tumor angiogenesis, invasion, and metastasis.

Vascular disrupting activity of tubulin-binding 1,5-diaryl-1H-imidazoles.

Highly cytotoxic 1,5-diaryl-1H-imidazoles were studied to clarify the relationship between cytotoxicity and activity as vascular disrupting agents (VDA). All the compounds disorganized the tubulin cytoskeleton, affected endothelial cell morphology and capillary formation in vitro, and caused vessel shutdown and tumor necrosis in vivo, thus confirming their vascular disrupting properties. Nonetheless, the substitution patterns on the imidazole ring, responsible for greater interaction energy with tubulin and higher cytotoxicity, were not associated to greater vascular disrupting activity.

Bioavailability of VEGF in tumor-shed vesicles depends on vesicle burst induced by acidic pH.

Tumor angiogenesis is regulated by a dynamic cross-talk between tumor cells and the host microenvironment. Because membrane vesicles shed by tumor cells are known to mediate several tumor-host interactions, we determined whether vesicles might also stimulate angiogenesis. Vesicles shed by human ovarian carcinoma cell lines CABA I and A2780 stimulated the motility and invasiveness of endothelial cells in vitro. Enzyme-linked immunosorbent assay and Western blot analysis revealed relevant amounts of vascular endothelial growth factor (VEGF) and the two matrix metalloproteinases MMP-2 and MMP-9, but not fibroblast growth factor-2, contained in shed vesicles. An A2780 cell-derived clone transfected to overexpress VEGF shed the same amount of vesicles as did a control clone, but contained significantly more VEGF within the vesicles. Despite a greater amount of VEGF in vesicles of the overexpressing clone, vesicles of both clones stimulated endothelial cell motility to comparable levels, suggesting that VEGF was stored within the vesicle and was unavailable. Only following vesicle burst induced by acidic pH (a characteristic of the tumor microenvironment) was VEGF released, leading to significantly higher stimulation of cell motility. Thus, tumor-shed membrane vesicles carry VEGF and release it in a bioactive form in conditions typical of the tumor microenvironment.

The vascular targeting property of paclitaxel is enhanced by SU6668, a receptor tyrosine kinase inhibitor, causing apoptosis of endothelial cells and inhibition of angiogenesis.

PURPOSE: Different antiangiogenic approaches have been proposed in cancer treatment where therapeutic efficacy has been shown with the addition of cytotoxic agents. Here, we used SU6668, a small-molecule receptor tyrosine kinase inhibitor, to investigate the combinatorial effect with paclitaxel on the cellular populations of the developing vasculature. EXPERIMENTAL DESIGN: The effect of this combination was evaluated in vitro in a 72-hour proliferation assay on human umbilical vein endothelial cells (HUVEC) and human microvascular endothelial cells derived from lungs, endothelial cells, aortic smooth muscle cells, and human ovarian carcinoma cells sensitive (1A9) and resistant (1A9-PTX22) to paclitaxel. Combination data were assessed by isobologram analysis. Cell survival was determined by terminal deoxyribonucleotide transferase-mediated nick-end labeling and Annexin V staining. The activity of the combination in vivo was evaluated in fibroblast growth factor-2-induced angiogenesis in Matrigel plugs s.c. implanted in mice. The 1A9-PTX22, paclitaxel-resistant xenograft model was used to evaluate tumor response. RESULTS: Combination index values and isobologram analysis showed synergy in inhibition of proliferation of HUVEC, human microvascular endothelial cells derived from lungs, and aortic smooth muscle cells. The combination induced greater apoptosis in HUVEC than the single agents. The addition of paclitaxel to the treatment with SU6668 significantly decreased the hemoglobin content and the number of CD31-positive vessels in Matrigel plugs in vivo. The combination of the drugs was more active than either single agent against 1A9-PTX22 xenografts; the tumor growth delay was accompanied by a significant reduction of vascular density. CONCLUSIONS: These findings show that the activity of angiogenesis inhibitors on vascular cells could be potentiated when administered in combination with chemotherapeutic agents that themselves have vascular targeting properties.

Potential antagonism of tubulin-binding anticancer agents in combination therapies.

ZD6126 is a vascular targeting agent, developed for the treatment of solid tumors. In vivo, ZD6126 is rapidly converted into the tubulin-binding agent N-acetylcolchinol. We have previously reported that in vitro N-acetylcolchinol disrupts microtubules and induces rapid changes in endothelial cell morphology, which in a tumor would lead to a rapid loss of tumor vessel integrity and subsequent extensive tumor necrosis. The aim of this study was to investigate the effect of cytotoxic antineoplastic drugs-cisplatin, doxorubicin, vincristine, paclitaxel, and docetaxel-on endothelial cell response to N-acetylcolchinol. We found that cisplatin and doxorubicin did not interfere with the ability of N-acetylcolchinol to cause morphologic changes in human umbilical vein endothelial cells, whereas vincristine showed additive effects. In contrast, the microtubule-stabilizing agents paclitaxel (1-10 micromol/L) and docetaxel (0.1-1 micromol/L) prevented the morphologic changes induced by N-acetylcolchinol in human umbilical vein endothelial cells. The effect was observed when cells were exposed to paclitaxel and N-acetylcolchinol together or when paclitaxel was given shortly before N-acetylcolchinol. Paclitaxel and N-acetylcolchinol interacted at the level of microtubule organization, as shown in immunofluorescence analysis of the cytoskeleton. The protective effect was reversible because 4 hours after paclitaxel wash out, cells recovered the sensitivity to N-acetylcolchinol. In vivo, pretreatment of mice with paclitaxel inhibited the vascular targeting activity of ZD6126 on newly formed vessels in the Matrigel plug assay and ZD6126-induced necrosis in tumors. These findings indicate that paclitaxel, depending on the timing and schedule of administration, can affect the vascular targeting activity of ZD6126, which may have an effect on the optimal scheduling of therapies based on the combined use of microtubule-stabilizing and microtubule-destabilizing agents.

Antiangiogenic properties of 17-(dimethylaminoethylamino)-17-demethoxygeldanamycin: an orally bioavailable heat shock protein 90 modulator.

PURPOSE: The purpose of this study was to investigate the antiangiogenic properties of 17-(dimethylaminoethylamino)-17-demethoxygeldanamycin (17-DMAG; NSC707545), a water-soluble benzoquinone ansamycin. EXPERIMENTAL DESIGN: The activity of 17-DMAG, in vivo, was evaluated for inhibition of fibroblast growth factor (FGF)-2-induced angiogenesis in s.c. implanted Matrigel in mice. In vitro, the activity of 17-DMAG on endothelial cells (human umbilical vein endothelial cells; HUVEC) was tested in FGF-2; and vascular endothelial growth factor (VEGF)-induced proliferation and apoptosis, motility, and extracellular matrix invasion; and on the alignment of capillary like structures in Matrigel. The protein level of heat shock protein (Hsp)90 and client proteins was examined by Western blot in FGF-2 and VEGF-stimulated HUVEC. RESULTS: Daily oral administration of 17-DMAG affected the angiogenic response in Matrigel in a dose-dependent manner. The hemoglobin content in the Matrigel implants was significantly inhibited, and the histological analysis confirmed a decrease of CD31(+) endothelial cells and of structures organized in cord and erythrocyte-containing vessels. In vitro, the compound inhibited dose-dependently the migration and the extracellular matrix-invasiveness of HUVEC and their capacity to form capillary like structures in Matrigel. 17-DMAG treatment also inhibited FGF-2 and VEGF-induced HUVEC proliferation and resulted in apoptosis. Accordingly, the expression of Hsp90 direct client proteins (pAkt and c-Raf-1) or their downstream substrates including pERK was also affected. 17-DMAG consistently increased the expression of Hsp70. Throughout the study similar results were obtained with 17-allylamino-17-demethoxygeldanamycin (17-AAG; NSC330507), the analog compound currently undergoing clinical trials. CONCLUSIONS: We show that the Hsp90 targeting agents 17-DMAG and 17-AAG inhibit angiogenesis. The strong effects on endothelial cell functions, in vitro, indicate that the antiangiogenic activity of 17-DMAG/17-AAG could also be due to a direct effect on endothelial cells. The oral bioavailability of 17-DMAG might be of advantage in investigating the potential of this compound in clinical trials with antiangiogenic as well as antiproliferative endpoints.

Vascular-targeting activity of ZD6126, a novel tubulin-binding agent.

The tubulin-binding agent ZD6126 is a novel vascular-targeting agent in clinical development for the treatment of solid tumors. In vivo, ZD6126 is rapidly converted into N-acetylcolchinol (ZD6126 phenol). In this study, we have explored the antivascular property of N-acetylcolchinol in vitro and ZD6126 in vivo. In cell culture, N-acetylcolchinol induced rapid changes in the morphology of human umbilical vein and lung microvessel endothelial cells. Within 40 min, the compound induced endothelial cell contraction, destabilization of the tubulin cytoskeleton, induction of actin stress fibers, and membrane blebbing. These effects occurred at noncytotoxic concentrations and were rapidly reversed on removal of the drug. Nonconfluent endothelial cells were more sensitive than confluent, quiescent cells. Among different cell types, endothelial cells were the most sensitive to the induction of morphological changes, whereas smooth muscle cells were not affected. In vitro, N-acetylcolchinol rapidly disrupted a network of newly formed cords. In vivo, ZD6126 caused shut down of newly formed vessels in the Matrigel plug assay, shortly after injection. This study indicates that rapid alteration of endothelial cell morphology may be responsible for the loss of tumor blood vessel integrity, vessel shut down, and extensive tumor necrosis induced by ZD6126 in experimental tumor models.

Antiangiogenic and antitumor activity of IDN 5390, a new taxane derivative.

PURPOSE: We previously reported that paclitaxel, a microtubule-stabilizing drug, inhibited angiogenesis, mainly by inhibiting endothelial cell motility (D. Belotti et al., Clin. Cancer Res., 2: 1843-1849, 1996). The aim of this study was to select a taxane with little cytotoxicity but with antimotility and hence antiangiogenic activity. EXPERIMENTAL DESIGN: Different taxanes, seco derivatives, and 14-beta-hydroxy-10-deacetyl baccatin III derivatives were tested for their effects on the proliferation and motility of human umbilical vein endothelial cells. The antiangiogenic and antineoplastic activities of the compound selected from this screening were further investigated in experimental models in vitro and in vivo. RESULTS: From the screening of different taxanes, we selected IDN 5390, a seco derivative that showed potent antimotility activity and less cytotoxicity than paclitaxel. In comparable experimental conditions, IDN 5390 inhibited endothelial cell migration without affecting proliferation. This compound dose-dependently inhibited the capacity of human umbilical vein endothelial cells plated on Matrigel to organize into a network of cords. In vivo, IDN 5390 significantly inhibited fibroblast growth factor-2-induced angiogenesis in Matrigel implants. Daily treatment with IDN 5390 in mice bearing established lung micrometastases from the B16BL6 murine melanoma caused a reduction in the size of metastases. Finally, IDN 5390 slowed the s.c. growth of the paclitaxel-resistant human ovarian carcinoma, 1A9/PTX22, xenografted in nude mice. CONCLUSIONS: The seco derivative IDN 5390 might represent the prototype of a new class of taxane derivatives with antiangiogenic properties.

Shedding of the matrix metalloproteinases MMP-2, MMP-9, and MT1-MMP as membrane vesicle-associated components by endothelial cells.

Production of matrix-degrading proteases, particularly matrix metalloproteinases (MMPs), by endothelial cells is a critical event during angiogenesis, the process of vessel neoformation that occurs in normal and pathological conditions. MMPs are known to be highly regulated at the level of synthesis and activation, however, little is known about the regulation of MMP secretion by endothelial cells. We found that cultured human umbilical vein endothelial cells shed vesicles (300 to 600 nm) originating from localized areas of the cell plasma membrane, as revealed by ultrastructural analysis. Normal and reverse zymography, Western blot, and immunogold analyses of the vesicles showed two gelatinases, MMP-2 and MMP-9, in both the active and proenzyme forms, the MT1-MMP proenzyme located on the external side of the vesicle membrane and the two inhibitors TIMP-1 and TIMP-2. Serum and the angiogenic factors, fibroblast growth factor-2 and vascular endothelial growth factor, stimulated the shedding of MMPs as vesicle components. Shedding the vesicle was rapid, as it was already completed after 4 hours. Addition of shed vesicles to human umbilical vein endothelial cells resulted in autocrine stimulation of invasion through a layer of reconstituted basement membrane (Matrigel) and cord formation on Matrigel. We conclude that endothelial cells shed MMP-containing vesicles and this may be a mechanism for regulating focalized proteolytic activity vital to invasive and morphogenic events during angiogenesis.