Dorina Belotti

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.

Expression levels of vascular endothelial growth factor, matrix metalloproteinases 2 and 9 and tissue inhibitor of metalloproteinases 1 and 2 in the plasma of patients with ovarian carcinoma.

We measured the levels of the vascular endothelial growth factor (VEGF), matrix metalloproteinases type 2 and type 9 (MMP-2 and MMP-9) and tissue inhibitors of matrix metalloproteinase 1 and 2 (TIMP-1 and TIMP-2) in the plasma of patients with ovarian carcinoma (n=40), in other gynaecological pathologies (n=30) and in the plasma of healthy volunteers (n=26). MMP-2 and MMP-9 (pro and active forms) gelatinolytic activity was measured by zymography. Enzyme-linked immunosorbent assays (ELISA) were used to assay soluble VEGF and TIMPs. Preoperative plasma VEGF levels were significantly higher in patients with ovarian cancer than in healthy volunteers (P<0.0001) or patients with a benign gynaecological pathology (P<0.0001). The expression of pro-MMP-9 was higher in the plasma of ovarian cancer patients than in the plasma of women with non-malignant disease (P=0.01) or healthy women (P<0.0002). Pro-MMP-2 was detected in the plasma of ovarian cancer patients, but levels did not differ from those in non-malignant disease or healthy donor samples. Plasma TIMP-1 and TIMP-2 levels were significantly higher in patients with ovarian carcinomas than in healthy volunteers (P<0.0001 and P=0.006, respectively) or in the patients with a non-malignant pathology (P<0.0001 and P=0.002, respectively). Sub-group analysis showed that VEGF and pro-MMP-9 were higher in the plasma of patients with serous carcinomas than other histological types. Furthermore, plasma VEGF and pro-MMP-9 levels were higher in the plasma of cancer patients with thrombocytosis. Throughout the study, and in the univariate analysis, no correlation was found between the VEGF, MMP and TIMP levels. Only TIMP-1 was associated with a poor survival and mortality risk.

Vascular Endothelial Growth Factor Stimulates Organ-Specific Host Matrix Metalloproteinase-9 Expression and Ovarian Cancer Invasion

Vascular endothelial growth factor (VEGF) and matrix metalloproteinases (MMP) regulate each other, contributing to tumor progression. We have previously reported that MMP9 induces the release of tumor VEGF, promoting ascites formation in human ovarian carcinoma xenografts. The aim of this study was to investigate whether tumor-derived VEGF regulated the expression of gelatinase by the stroma, influencing the invasive properties of ovarian tumors. Tumor variants derived from 1A9 human ovarian carcinoma, stably expressing VEGF121 in the sense (1A9-VS-1) and antisense orientations (1A9-VAS-3), were used. In vivo, zymographic analysis of tumors from 1A9-VS-1 implanted in the peritoneal cavity of nude mice showed higher levels of gelatinases, particularly murine MMP9, indicating that VEGF stimulates host expression of the matrix-degrading enzyme. Murine MMP9 expression was also high in the ovaries of mice bearing 1A9-VS-1 tumors. The effect on host MMP9 activity was organ-specific. The levels of host pro-MMP9 in ovaries correlated with the plasma levels of tumor VEGF and with the selective invasion of the ovaries. Induction of host MMP9 expression in tumors and ovaries was independent of the site of tumor growth as it was seen in mice carrying both intraperitoneal and subcutaneous tumors. The anti-VEGF antibody bevacizumab (Avastin) inhibited MMP9 expression and tumor invasion in the ovaries of mice bearing 1A9-VS-1 tumors. These findings point to a complex cross-talk between VEGF and MMPs in the progression of ovarian tumor and suggest the possibility of using VEGF inhibitors to affect MMP-dependent tumor invasion. (Mol Cancer Res 2008;6(4):525–34)

Circulating plasma vascular endothelial growth factor in mice bearing human ovarian carcinoma xenograft correlates with tumor progression and response to therapy

Vascular endothelial growth factor (VEGF) performs as an angiogenic and permeability factor in ovarian cancer, and its overexpression has been associated with poor prognosis. However, models to study its role as a marker of tumor progression are lacking. We generated xenograft variants derived from the A2780 human ovarian carcinoma (1A9), stably transfected with VEGF121 in sense (1A9-VS-1) and antisense orientation (1A9-VAS-3). 1A9, 1A9-VS-1, and 1A9-VAS-3 disseminated in the peritoneal cavity of nude mice, but only 1A9-VS-1, the VEGF121-overexpressing tumor variant, produced ascites. Tumor biopsies from 1A9-VS-1 showed alterations in the vascular pattern and caused an angiogenic response in the chorioallantoic membrane assay. A significant level of soluble VEGF was detectable in the plasma of mice bearing 1A9-VS-1 even at an early stage of tumor growth. Plasma VEGF correlated positively with tumor burden in the peritoneal cavity and ascites accumulation. Cisplatin reduced the tumor burden and ascites in mice bearing 1A9-VS-1; the response was associated with a significant decrease of VEGF in plasma. This 1A9-VS-1 xenograft model reproduces the behavior of human ovarian cancer by growing in the peritoneal cavity, being highly malignant, and producing ascites. Plasma VEGF as a marker of tumor progression offers a valuable means of detecting early tumor response and following up treatments in an animal model.

Shedding of the 67-kD laminin receptor by human cancer cells.

The 67‐kD laminin receptor (67LR) is a cell membrane‐associated molecule exhibiting high affinity for the basement membrane glycoprotein, laminin. While export of the 67LR toward the extracellular matrix has been recently suggested by electron microscopy studies, there is to date no evidence of shedding of the 67LR from cells. Using two monoclonal antibodies directed against the 67LR, we developed a double‐determinant radioimmunoassay that demonstrates that the 67LR is released from cancer cells into the culture medium. The shed molecule exhibited the same apparent molecular weight as that of the membrane‐associated 67LR, suggesting that no proteolytic cleavage is involved in the process. Furthermore, we demonstrate that the 67LR is not anchored to the membrane through a glycolsyl‐phosphatidylinositol bridge. However, the observation that lactose increased the release of 67LR suggests that a lectin‐type interaction is involved in the cell membrane association of this laminin binding protein and the cell surface. Interestingly, the released 67LR recovered after HPLC gel filtration was found free as well as associated to high molecular weight complexes. The free 67LR retained its ability to bind to the cell surface. Our study is the first demonstration that the 67LR is effectively shed by cancer cells. The released free 67LR could play an important role in modulating interactions between cancer cells and laminin during tumor invasion and metastasis.

MMP inhibitors: Experimental and clinical studies

Matrix metalloproteases (MMPs) are a family of structurally related enzymes that are capable of degrading proteins of the extracellular matrix. These enzymes play a role in tissue remodelling associated with both physiological and pathogenic processes. A high expression of MMPs is associated with cancer malignancy: it is related to the tumors ability to metastasize and to the process of angiogenesis. Treatment with MMP inhibitors alone or in combination with cytotoxic therapy is an interesting novel approach to control tumor progression. The expected mechanism of action of these compounds and the difference in side effects compared to cytotoxic drugs make the definition of endpoints and the assessment of response difficult. Furthermore, it is not yet clear whether tumor vascularization or, more specifically, MMP expression/activation should be a criterion of eligibility for this kind of treatment. This review provides an overview of the characteristics of MMPs and their role in tumor progression, metastasis and angiogenesis. Preclinical and clinical studies with synthetic MMP inhibitors are described. The presence of MMPs in biological fluids of patients and their use in prognostic evaluation and in determining the efficacy of treatment with MMP inhibitors is discussed.

Targeting angiogenesis with compounds from the extracellular matrix

The extracellular matrix (ECM) is the central element of a pericellular network of bioactive molecules. It orchestrates molecular interactions, availability and activity, acting as a key regulator of cell functions and complex biological processes, including physiological and pathological angiogenesis. The ECM serves as a source of both stimulatory and inhibitory angiogenesis regulatory factors. The observation that several endogenous inhibitors of angiogenesis derive from the ECM proves its importance in physiological angiogenesis, and point to the ECM as a precious source of therapeutic agents for angiogenesis-driven diseases, including cancer growth and metastatic dissemination. This review focuses on the different approaches to exploit ECM molecules for designing tools for therapeutic inhibition or monitoring of pathological angiogenesis, with particular focus on antineoplastic therapy, and emphasis on peptides of ECM moieties and mimetic small molecules.

Thrombospondin modulates basic fibroblast growth factor activities on endothelial cells

We previously reported that thrombospondin (TSP) induces endothelial cell (EC) adhesion, spreading and motility, suggesting that it can play a role in angiogenesis. We then studied whether TSP might modulate EC response to known angiogenic stimuli in vitro. Here we describe that TSP inhibits EC chemotactic response to basic fibroblast growth factor (bFGF). Furthermore, TSP and its 140 kD fragment reduce EC proliferative response to serum and bFGF. These data support the indicated role of TSP and its 140 kD fragment in angiogenesis and in related pathologies including tumor malignancy.

Identification of thrombin-like activity in ovarian cancer associated ascites and modulation of multiple cytokine networks

Blood coagulation cascades can be activated by different mechanisms and to different levels in cancer patients. In a study conducted on the transcriptional profile of epithelial ovarian cancer patients a number of possible links between coagulation and inflammation have been suggested and we and others have reported that, in addition to its central role in blood coagulation and haemostasis, thrombin is a powerful regulator of inflammatory responses. Here, we report that thrombin- like activities were present in the malignant ascites of patients with ovarian carcinoma. Malignant ascites significantly enhanced the release of cytokines/chemokines, which have been previously shown to support tumour progression, such as interleukin (IL)-6, IL-1β, CCL2 and CXCL8, in human peripheral blood mononuclear cells of healthy volunteers. Interestingly, ascites enhanced the release of the anti-inflammatory cytokine IL-10 and inhibited the production of interferon-γ and IL-12. The presence of the anticoagulant antithrombin reversed IL-12 inhibition induced by ascites in human monocytes. Finally, the use of thrombin and of the specific thrombin receptor (PAR) agonist peptides, TFLLRN and AYGPK, suggests that IL-12 inhibition is thrombin-specific and related to PAR-1, but not to PAR-4. These findings underline the tight relationship between the coagulation pathway, where thrombin is the key enzyme, and cytokine modulation, including IL-12 inhibition, which is a critical feature of the tumour microenvironment, and may represent a powerful strategy used by tumours to escape immune surveillance.

Thrombospondin-1 promotes mesenchymal stromal cell functions via TGFβ and in cooperation with PDGF.

Mesenchymal stromal cells (MSC) are characterized by unique tropism for wounded tissues, high differentiating capacity, ability to induce tissue repair, and anti-inflammatory and immunoregulatory activities. This has generated interest in their therapeutic use in severe human conditions as well as in regenerative medicine and tissue engineering. Identification of factors involved in the regulation of MSC proliferation, migration and differentiation could provide insights into the pathophysiological regulation of MSC and be exploited to optimize clinical grade expansion protocols for therapeutic use. Here we identify thrombospondin-1 (TSP-1) as a major regulator of MSC. TSP-1 induced MSC proliferation. This effect was mediated by TSP-1-induced activation of endogenous TGFβ, as shown by the inhibitory effects of anti-TGFβ antibodies and by the lack of activity of TSP-2 - that does not activate TGFβ. Moreover, TSP-1 strongly potentiated the proliferative and migratory activity of PDGF on MSC. TSP-1 directly bound to PDGF, through a site located within the TSP-1 type III repeats, and protected the growth factor from degradation by MSC-derived proteases, hence increasing its stability and bioavailability. The studies presented here identify a more comprehensive picture of the pleiotropic effect of TSP-1 on MSC behavior, setting the basis for further studies aimed at investigating the possible use of PDGF and TSP-1 in the in vitro expansion of MSC for therapeutic applications.